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POST User Manual

Version 12

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POST User Manual Update Sheet for Version 12

April 2009

Modifications:

The following modifications have been incorporated:

Section Page(s) Update/Addition Explanation

All All Update Conversion to Microsoft® Word format

1.1 1-1 Update Delete references to legacy program PICASO

4.3.2 4-5 Update Delete Section 4.3.2 (PICASO Input)

App A.12 A-12 Update Delete references to legacy program PICASO

Contents


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POST User Manual

TABLE OF CONTENTS

1. Introduction ........................................................................................................ 1-1

1.1. General Description ................................................................................... 1-1 1.2. Facilities Available .................................................................................... 1-2

1.2.1. Shell Elements ................................................................................... 1-2 1.2.2. Laminated Shell Elements ................................................................. 1-3 1.2.3. Beam Elements .................................................................................. 1-3 1.2.4. Axisymmetric Solid and Shell Elements ........................................... 1-3 1.2.5. Harmonic Solids................................................................................. 1-3

1.3. Program Requirements............................................................................... 1-4 1.4. Element Grouping ...................................................................................... 1-4 1.5. Loadcase Combination............................................................................... 1-5 1.6. Local Axes Consideration .......................................................................... 1-5

1.6.1. Local Axes for SHELL, LAMI and SBEAM Data ............................ 1-5 1.6.2. Local Axis for BRICK Data .............................................................. 1-6 1.6.3. Output Axes Definition ...................................................................... 1-6 1.6.4. Averaging Groups with Differing Output Systems ......................... 1-13 1.6.5. Material Axes for Laminated Shells ................................................ 1-14

1.7. Processing of Summed Out-of-Plane Shear Forces for the TRB3 Element 1-15 1.8. Boundary Conditions for Harmonic Runs ............................................... 1-16 1.9. UNITS ...................................................................................................... 1-16

2. INPUT Data ....................................................................................................... 2-1 2.1. General Principles ...................................................................................... 2-1

2.1.1. Special Symbols ................................................................................. 2-3 2.2. UNITS Command ...................................................................................... 2-9 2.3. Data Type Commands.............................................................................. 2-11

2.3.1. Data Type and Sub-Type Commands .............................................. 2-11 2.4. Output Axis Commands ........................................................................... 2-13

2.4.1. CONS Command (SHELL or SBEAM data) .................................. 2-13 2.4.2. OUTP Command (SHELL data only).............................................. 2-14 2.4.3. OUTR Command (SHELL data only) ............................................. 2-15 2.4.4. OUTT Command (SHELL data only) ............................................. 2-16 2.4.5. OUTB Command (SBEAM data only) ............................................ 2-16 2.4.6. SKEW Command (SHELL data only) ............................................. 2-17

2.5. Group Data Commands............................................................................ 2-18 2.5.1. LAYE Command (LAMI data only)................................................ 2-18 2.5.2. RDAT Command ............................................................................. 2-20 2.5.3. TCRD Command ............................................................................. 2-21

2.6. Group/Element Selection Commands ...................................................... 2-22 2.6.1. GROU Command............................................................................. 2-22 2.6.2. EXTR Command ............................................................................. 2-23 2.6.3. SKIP Command ............................................................................... 2-24 2.6.4. NOAV Command ............................................................................ 2-25 2.6.5. AVGR Command............................................................................. 2-26

2.7. Loadcase Combination Commands ......................................................... 2-27 2.7.1. NEWC Command ............................................................................ 2-27 2.7.2. ADDC Command............................................................................. 2-28

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POST User Manual 2.7.3. ADDF Command ............................................................................. 2-29

2.8. Stress Type Selection Commands ............................................................ 2-31 2.8.1. FACT Command .............................................................................. 2-31 2.8.2. AVST Command ............................................................................. 2-31 2.8.3. FANM Command (SHELL data only) ............................................ 2-32 2.8.4. BANM Command (SHELL data only) ............................................ 2-33 2.8.5. PRST Command .............................................................................. 2-34 2.8.6. PRVM Command............................................................................. 2-35 2.8.7. SHRS Command (SHELL data only) .............................................. 2-36 2.8.8. WOOD Command (SHELL data only)............................................ 2-37 2.8.9. REIN Command (SHELL data only) ............................................... 2-38

2.9. Control Output Commands ...................................................................... 2-39 2.9.1. PRIN Command ............................................................................... 2-39 2.9.2. PLOT Command .............................................................................. 2-40

2.10. Check Stresses ......................................................................................... 2-41 2.10.1. FECS and FECM Commands (SHELL data only) .......................... 2-41 2.10.2. VONM Command ............................................................................ 2-42 2.10.3. TRES Command .............................................................................. 2-43

2.11. Harmonic Combination Commands ........................................................ 2-44 2.11.1. Data for Harmonic Analyses ............................................................ 2-44 2.11.2. ANGL Command (HARM Data only) ............................................ 2-45 2.11.3. COMB Command (HARM data only) ............................................. 2-45 2.11.4. SELE Command (HARM data only) ............................................... 2-46 2.11.5. COS and SIN Commands (HARM data only) ................................. 2-47

2.12. Miscellaneous Commands ....................................................................... 2-49 2.12.1. SECT Command .............................................................................. 2-49 2.12.2. ANGL Command (SHELL data only) ............................................. 2-50 2.12.3. END Command ................................................................................ 2-50

3. Examples ............................................................................................................ 3-1 3.1. Example 1: Default Data ........................................................................... 3-1 3.2. Example 2: Simple Shell Result Processing ............................................. 3-1 3.3. Example 3: Simple Axi-symmetric Result Processing ............................. 3-2 3.4. Example 4: Post Processing Component Results from Multi Level Axisymmetric Analysis .......................................................................................... 3-3 3.5. Example 5: Loadcase Combinations ......................................................... 3-4 3.6. Example 6: Post Processing Harmonic Analyses ..................................... 3-5 3.7. Example 7: Harmonic Combinations ........................................................ 3-6 3.8. Example 8: Post Processing Shell Compatible Beams ............................. 3-7 3.9. Example 9: Post Processing Laminated Shells ......................................... 3-8

4. Output ................................................................................................................ 4-1 4.1. Printed Output ............................................................................................ 4-1

4.1.1. SHELL Data....................................................................................... 4-1 4.1.2. LAMI Data ......................................................................................... 4-2 4.1.3. Shell BEAM Data .............................................................................. 4-2 4.1.4. BRICK, AXIS and HARM Data ........................................................ 4-2

4.2. Backing Files ............................................................................................. 4-2 4.3. Plotting Program Input ............................................................................... 4-3

4.3.1. FEMVIEW Input ............................................................................... 4-3 4.3.2. PATRAN® Input ................................................................................ 4-4

Appendix A - Preliminary Data Block for POST ................................................. A-1

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POST User Manual A.1 Introduction ................................................................................................ A-1 A.2 SYSTEM Command .................................................................................. A-2 A.3 PROJECT Command ................................................................................. A-2 A.4 JOB Command ........................................................................................... A-3 A.5 FILES Command ....................................................................................... A-3 A.6 TITLE Command ....................................................................................... A-3 A.7 TEXT Command ........................................................................................ A-4 A.8 STRUCTURE Command........................................................................... A-4 A.9 COMPONENT Command ......................................................................... A-5 A.10 NEWSTRUCTURE Command ................................................................. A-6 A.11 OPTIONS Command ................................................................................. A-6 A.12 SAVE Command ....................................................................................... A-8 A.13 RESU Command ........................................................................................ A-9 A.14 UNITS Command (not valid for fixed format ASAS data) ....................... A-9 A.15 END Command ........................................................................................ A-10

Appendix B - - Running Instructions for POST .................................................. B-1 B.1 ASAS Files Required by POST ................................................................. B-1 B.2 Running Instructions for POST ................................................................. B-1

Appendix C - - Equations used for Stress Calculations ....................................... C-1 C.1 Notation...................................................................................................... C-1 C.2 Stress Formulae .......................................................................................... C-2 C.3 Wood-Armer Calculations ......................................................................... C-3

C.3.1 Wood-Armer Moments - Orthogonal Reinforcing ............................ C-3 C.3.2 Wood-Armer Moments - Skewed Reinforcing .................................. C-4

C.4 Reinforcement Area Calculations .............................................................. C-4 Appendix D - - Loadcase Combination Methods ................................................ D-1

Introduction POST User Manual

Page 1-1 Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

POST Post-processing for ASAS Stress Output

1. Introduction

1.1. General Description

POST is a general post-processing program designed to aid the engineer using ASAS to analyse shell, solid and three-dimensional axisymmetric structures. It performs many tedious tasks on the ASAS results such that the engineer can concentrate on the design of his structure without the need to waste precious man time in repetitive arithmetic calculations.

ASAS and LOCO finish by printing stresses and/or moments for each node of each element and storing these on a backing file. POST reads these stresses from the backing file and averages the stresses given by all the elements at each node. From these, surface, principal, von-Mises, Tresca, section stresses and Wood-Armer moments may be calculated and printed depending on the processing requested and the element type. These and other facilities are described fully in the next section.

Note that if POST is to be run, the command SAVE LOCO FILES must be included in the preliminary data of the previous ASAS or LOCO run, so that the appropriate files will be retained for use by the program.

The program will also convert stress results into a suitable format ready for plotting using FEMVIEW or PATRAN®*.

To produce an interface file for one of these plotting programs, SAVE commands must be given in the POST preliminary data (see Appendix A-). In addition, the run results may be saved permanently on the project files using the RESU command.

Note that the BR32 element is not available with FEMVIEW at present.

* PATRAN® - a corporate trademark of the MSC Software Corporation.



1.2. Facilities Available

POST has six different processing paths depending on which type of element is being considered. The process required is selected by the user and causes POST to processes only those elements of the correct type in the model. Thus an analysis having a number of differing element types will require more than one run of POST to post-process the whole model. The processes are identified by data type as follows:

Data Type Command

Element Family Elements

SHELL thick & thin shells

plate membranes sandwiches

triangular plate

QUS4 TCS6 TCS8 GCS6 GCS8 TBC3 SLB8

QUM4 QUM8 TRM3 TRM6 SND6 SND8 SN12 SND16 TRB3

LAMI laminated shells QUS4 TCS6 TCS8

SBEAM shell compatible beams GCB3 TCBM

BRICK bricks BRK6 BRK8 BR15 BR20 BR32 TET4 TE10

AXIS SOLID AXIS SHELL

axisymmetric solids axisymmetric shells

QUX4 QUX8 TRX3 TRX6 ASH2

HARM SOLID HARM SHELL

harmonic axisymmetric solids harmonic axisymmetric shells

QHX4 QHX8 THX3 THX6 AHH2

Only one data type command may be submitted in each run; other data type commands will be ignored.

Restriction: When using SAVE FEMS or SAVE PICA, only one of the shell element families may be processed in each run. The GROU command should be used to restrict the element type(s) to those associated with one of the SHELL families. (Note that thick and thin plates are considered as one element family).

1.2.1. Shell Elements

For Shell elements, top, middle and bottom surface stresses are calculated for each element in turn, and a set of average stresses is calculated for each node which is associated with two or more elements. The outshears for plate and shell elements, with the exception of the TRB3 element, may also be averaged by using the SHRS command.

The in-plane principal stresses (σ1 and σ2) are printed for each of the three surfaces along with the principal stress difference (σ1 - σ2). Two ’check stresses’ can be provided by the user, against which the stresses at each node can be compared and flagged if they exceed the check stress. As an aid to results interpretation, asterisks are used to highlight the highest absolute values of σ1, σ2 and (σ1 - σ2) for each surface.



1.2.2. Laminated Shell Elements

The nodal stresses in and normal to the fibre direction and also the inshear stress are calculated for individual laminae from the resultant strain for the whole composite section. Where a node is associated with more than one element in the same group the strains for the whole composite section will be averaged at the node prior to the layer stresses being calculated.

1.2.3. Beam Elements

Results for TCBM and GCB3 elements are processed in terms of member forces and moments. Where a node is associated with more than one element within the same groups the averaged results will be presented. The user may also specify a new output axes for the elements to override the default element local axes.

1.2.4. Axisymmetric Solid and Shell Elements

The program calculates average nodal stresses for the solid elements. The user may print the averaged nodal stresses for any or all of the loadcases, each factored by a constant if required. In addition to the average nodal stresses the program prints the von Mises equivalent stress for each node and the factor by which this stress exceeds a user defined allowable level.

The user may also request a printout of principal stresses and directions for any or all of the loadcases, again factored by a constant if required. In addition to the principal stresses and directions, the program prints the sum of the principal stresses, the von Mises equivalent stress, the Tresca stress and the factor by which the Tresca stress exceeds a user defined allowable level.

For axisymmetric solids only, the user may request additional information for the stresses across a specified section of the structure. This comprises the average ‘membrane’ stress components across the section and the bending stress components at each node across the section. The principal membrane stresses are also printed along with the corresponding stress intensities.

1.2.5. Harmonic Solids

Additional features of POST permit the calculation of the average nodal stresses for the harmonic solid elements THX3, QHX4, THX6 and QHX8. The user may generate a number of combined loadcases from structures with different harmonic numbers (analogous to the manner of operation of LOCO) and produce stress output at a number of angular stations around the structure for these combined loadcases. This allows the user to perform Fourier series types of analysis for known harmonics of load at substantially less cost than would be involved in a full three dimensional (brick) analysis.



In order to identify the combined results being created, a new structure name is required and this is defined using the NEWSTRUCTURE command in the preliminary data. If the set of files for the combined loadcases has been saved and additional POST runs on the same load cases are needed, a harmonic re-run with simplified data input requirements may be performed. In the re-run, the structure name becomes the new structure name in the original run with the NEWSTRUCTURE command omitted. All the loadcase combination data are also omitted.

Average nodal stresses at each circumferential station, von Mises equivalent stress and the factor by which it exceeds a user defined allowable are printed.

Principal stresses may be produced in an analogous manner to the purely axisymmetric values described above.

Currently the facility to produce extra information about stresses across specific sections is not available with the harmonic elements.

1.3. Program Requirements

The program works directly from backing files created during an ASAS or LOCO run. The files described must be saved using the appropriate commands described in the User Manuals. All other information is provided via the data commands described in detail in Chapter 2 Any elements other than those allowed for the data type specified in Section 1.2 are ignored by the program; however, at least one of these elements types must be encountered.

For an axisymmetric job all the elements are not only axisymmetric themselves but the loading is also axisymmetric. For harmonic analyses the program checks that the user specified harmonic number on all the harmonic elements accessed from an individual ASAS structure have the same harmonic number. Clearly, a structure with a mixed harmonics in a loadcase is physically meaningless as discontinuities in displacements are implied.

1.4. Element Grouping

It may not always be desirable, or even meaningful, to average the nodal stresses of adjacent elements. For example, where there are different material properties or thicknesses between elements, the strains may be continuous but there will be step changes in the stresses. If the nodal stresses are averaged at such discontinuities, these step changes will be lost and a false average obtained.

For this reason, POST considers the elements in groups. These groups may be made up of one ASAS element group (i.e. the groups defined in the ASAS element topology data), or of elements defined by a list of element numbers in the POST data. In the case of the former, individual elements may be omitted from a group by using the SKIP command in the POST data. Note that if EXTR groups are created in POST, then the CREATE Command should be used on the SAVE FEMS line.

POST works through the groups in order, considering all loadcases for one group before moving on to the next. Within the groups, all nodal stresses are averaged, but no averaging occurs across the group boundaries.



If a group contains a mixture of more than one sub-type, e.g. shells, plates and membranes, then POST will only process elements with the same type as the first valid element found for that group (i.e. shell, membrane or plate). If other element types are required from a group then new groups can be created using the EXTR command (Section 2.6.2) containing only the element types required.

In SHELL data, should any thickness discontinuity be encountered between adjacent elements within a group, an error message is printed and POST moves on to the next group. The allowable tolerance is 1% difference in thickness at each node. It is possible to override this error by a warning if option CCGO is specified in the preliminary data.

For SHELL and SBEAM data, a check is also provided to ensure the offset compatibility between adjacent elements within a group. An error message is printed if this check fails and POST moves on to the next group. As before, it is possible to change the error status to warning status by specifying option CCGO in the preliminary data.

For LAMI data, strains rather than stresses are averaged. Nodal thickness however, is used in the calculation of the individual lamina stresses and so once again there may not be nodal discontinuities within a group. Additionally all the elements within the group must have a consistent ASAS material axes and composite layer data in order that the layer stresses are calculated correctly from the averaged strains. Further consideration of the ASAS material orientation is given in Section 1.6.5.

1.5. Loadcase Combination

The program allows the user to create new loadcases by factoring and combining any or all of the existing loadcases, including new loadcases already created. Average nodal stresses and principal stresses may be printed for these combinations as well as for the original loadcases. A number of combination methods are available in addition to simple summation. These are described in detail in Appendix D-.

1.6. Local Axes Consideration

1.6.1. Local Axes for SHELL, LAMI and SBEAM Data

ASAS nodal stresses are calculated in the element local axis system for some shell elements and the shell beam elements. In cases where the element local axis systems of adjacent elements within an element group are not consistent (that is, the same orientation with respect to the global axis system), it is not meaningful to average nodal stresses across element boundaries. In such cases it is possible to reorientate the stresses into a consistent set before averaging by specifying a new axis system, called the output axis system, which is common to all elements within the group. The new output axis systems are defined by the OUTP, OUTR, and OUTT commands for shell elements and the OUTB command for the shell beam elements.

Whilst an output command must be used for any group containing elements with inconsistent axes they may also be used whenever the user simply wants to reorientate the output axes. If an output command is not used for a



given group, then the CONS command should be used for that group, indicating the axes are consistent. POST is not able to check for axes consistency, so if CONS is used it is the user’s responsibility to satisfy himself that the axes are consistent.

For laminated shells the strains used to calculate the individual layer stresses are once again in the element’s local axes system. In this case the output orientation of the results is already predefined by the fibre orientation for each layer which in turn is related to the material axes of each each element. POST automatically converts the ASAS strains into the material axes before the nodal averaging, and then further rotates the strains into the fibre direction for each of the individual layers examined.

1.6.2. Local Axis for BRICK Data

In the case of brick and axi/harmonic elements, the ASAS results are in the global axis system and therefore consistent. For this reason there are no commands for reorientating stresses for these element types.

1.6.3. Output Axes Definition

(a) Cartesian Axes System - OUTP Command

The cartesian axes are defined in terms of a reference direction and a reference point. Firstly, the top and bottom surfaces of the shell are defined. This is done by drawing a vector from the reference point towards the node in question. This is called the control vector. The first surface cut by the control vector is defined as the bottom surface, and the second as the top surface. The new Z axis at this node is normal to the shell and positive in the direction from the bottom surface towards the top surface. See Figure 1.

The new X axis lies in the plane containing the new Z axis and the reference direction: note that the reference direction is specified by direction cosines with respect to the global axis system. The X axis is positive on the side of the Z axis containing the positive reference direction. The new Y axis forms a right-handed set with the new X and Z axes. See Figure 2.

The above rules break down in two cases. The first is where the reference direction and the new Z axis are parallel and the second where the control vector is tangential to the shell surface.

In both cases, warnings are printed when the control vector is within 5° of the shell surface tangent. Errors are printed should the angle be less than 1°. In the case of an error the node in question is omitted.



Figure 1 Figure 2



Example: Cylindrical Shells

Consider a cylindrical shell of diameter 10 and length 100 orientated parallel to the Z axis with its central axis at X=5, Y=0. A suitable output axes may be specified by a reference direction parallel to the central axis and the reference point on the central axis halfway along the cylinder.

Figure 3

The reference point could be anywhere within the boundary of the tube, but the central location ensures the least chance of failing the 5º check. The resulting output axes system has the outer surface of the cylinder as the top surface, the local x’ stress in the longitudinal direction and the local y’ stress in the hoop direction.



Example: Flat Shells/Plates

For a flat plate the ideal position for the reference point is on the plate normal through the centre of the plate at a distance equivalent to half the plate length below the plate. Again the exact position is not critical. The reference direction should then be defined in the plane of the plate in the direction required for the local x’ stress.

Figure 4

In some cases it may be desirable to use the same output axes definition for a series of plates. If the reference point is placed between plates this will result in a reversal of the local y’ direction. This may not be significant for stress results but will affect the definition of the skew angles for Wood-Armer moments and reinforcement area calculations.

Figure 5

node 2

x'

y'y'

x'node 1

L

Reference Point

Reference direction

2L

y 'x'

x'y '

Reference point

x'y '

Reference point

x'y '

B T

T B

T B

T B



(b) Radial Axes System - OUTR Command

The cartesian axes definition cannot be used to give radial and hoop stresses for a flat circular disc. In order to cover this case the radial axes definition may be used. These axes are defined by two points, the first is the centre point for the radial axes system and the second is a reference point as for the cartesian axes system. A reference direction is set up for each individual node within the group and is defined by the vector from the node to the centre point. The local axes system for the node is then set up from the reference direction and the reference point using the same conventions as for cartesian axes definition. See Figure 6.

At the centre of the disc the centre point may coincide with the central node, such that a reference direction is not defined. In this case (and also if the reference direction defined is normal to the shell) the local X will be defined as lying in the plane containing the local Z (or shell normal) and the global ordinate that is most normal to the local Z. In the case of the local Z being normal to two global ordinates, the global X would be used as first preference and the global Y as the second. The local Y is then defined normally to both local X and Z.

Figure 6

Z2

X2

Y2

Z1

X1

Y1

Node 1Node 2

Centre Point

Reference Point

Reference Direction for Node 1



Example: Hemispherical Shell/Disc

For a hemispherical shell the reference point should be placed at or near the centre of the hemisphere (at zero radius) and the centre point on the hemisphere at the centre.

In the case of a flat disc the reference point should be positioned on the axis of the disc at a distance equivalent to the radius of the disc below the disc.

Figure 7

In both cases the local y’ stress will be in the hoop direction. For the hemispherical shell the local x’ stresses will be in the longitudinal direction and for the flat disc in the radial direction.



(c) Toroidal Axes System - OUTT Command

The toroidal axes system is used to give hoop and longitudinal stresses for torus shaped structures. These axes are defined by the coordinates of the torus centre point, the direction cosines for the major axes and the major radius. For each node a radial slice is made through the torus at the position of the node. The axes reference point for the node is then defined as being on the circular minor axis at the position of the slice, and the reference direction as tangential to the circular minor axis at the same point. The reference direction is positive in the positive sense of the minor axes which itself follows a right hand screw rule with the direction cosines defining the major axes. The local axes system for the node is then set up form the reference direction and reference point using the same conventions as for the cartesian axes definition. See Figure 8.

For the toroidal axes system, the major radius may not be zero (instead the OUTP or OUTR systems should be used). Also if the node under consideration lies on the circular minor axes, the local axes for the node cannot be defined and the elements containing this node will be skipped.

Figure 8 OUTT Axes System

See Figure 10 for an example demonstrating the use of the OUTT output axes system.



(d) Beam Axes System - OUTB Command

The new output axes system is assumed to have the X lying tangentially along the beam element. The positive direction is defined by specifying a reference direction for the output X-axis. The positive direction along the beam is that which gives an angle in the range of ±90° with the reference direction.

A second reference direction (relating to the Z) is used to complete the output axes system. The new Y is positioned such that it is mutually perpendicular to the new X and the second reference direction, the direction forming a right handed set with the reference direction and the new X. Finally the new Z is positioned to form an orthogonal right handed axes set with the new X and Y.

Example output systems for beam elements are shown in Figure 9.

Figure 9 OUTB Axes System

1.6.4. Averaging Groups with Differing Output Systems

The AVGR command gives the user the ability to average across group boundaries with differing output axes systems. This is admissible, but the user must ensure that where the groups meet the local axes systems are aligned so that averaging is valid. Figure 10 shows a typical example of where averaging across group

Z

X Y

X

Z

Y

X Axis Reference Direction

Z Axis Reference Direction



boundaries with differing output axes systems may be used. The structure consists of a cylinder (Group 1 with output system OUTP), connected to a 90° section of a pipe bend or torus (Group 2 with output system OUTT). The other end of the bend connects to a second cylinder (Group 3 with output system OUTP). Finally the second cylinder is closed with a spherical cap (Group 4 with output system OUTR). For each section, the longitudinal stress is σx and the hoop stress is σy. The through thickness direction for all Groups in the local Z axis.

Figure 10 Example of Averaging Across Groups

1.6.5. Material Axes for Laminated Shells

The consistency of the material axes is a requirement for POST since the element strains are converted into the material axes prior to combination. This is usually satisfied unless different global reference axes have been defined to set up the material axes on adjacent elements. Figure 11 shows the relationship between global axes, element local axes, material axes and fibre orientation. Layers are numbered from the bottom surface of the shell element (on the negative local Z side of the element) towards the top surface.



Figure 11

1.7. Processing of Summed Out-of-Plane Shear Forces for the TRB3 Element

For the TRB3 elements only, the nodal shear value obtained using the FANM command is the sum of the nodal shear force from all elements surrounding the node. This value is of limited use as it represents the outforce balancing any external force or reaction at that node and gives little indication of the internal shearing force in the plate. More useful values are obtained if the nodal shears are summed either side of a line or section defined by the element boundaries. The section may form a closed loop ie, first and last nodes identical, or may be open ended.

If the FANM/BANM/AVST and the SECT commands are present in the data, the normal output is augmented by an extra table. The summed nodal shears on each side of the section are reported for each nodal point on the section, giving two shear forces at each node. The elements which contribute to each value are also reported.



These shear forces may be interpreted to give a picture of the internal shearing forces at each node on the section.

1.8. Boundary Conditions for Harmonic Runs

If the harmonic part of the program is used then each ASAS job accessed must have the same element topology data. Thus, if an analysis was to combine a purely axisymmetric structure (and load) this must be run as a harmonic job with the geometry property for the harmonic number set to 0.0. To restrain rigid body motions special suppression data are required for the harmonics 0 and 1. For harmonic 0 at least one TH (θ) degree of freedom should be removed, to prevent the structure rotating as a rigid body about the Z axis. For harmonic 1 there must be at least one R and one θ degree of freedom suppressed as the displaced shape implied by this harmonic corresponds to a rigid body motion of the section in the R–θ plane. All harmonics require at least one Z suppression, but for the harmonics 2 and above there is no need to have any R or θ suppressions to remove rigid body movements.

1.9. UNITS

If UNITS have been employed in the ASAS analysis it is possible to specify modified units for both the POST input data and the results. The default units will be those utilised in the original analysis and if this is satisfactory then no additional information is required in the POST data. Note, however, that the angular data unit defaults to degrees.

If modified units for input data are required, this is achieved by specifying one or more UNITS commands within the main body of the POST data thus permitting a combination of unit systems within the one data file (see Section 2.2 UNITS command).

If the stress results are required in different units to the default, the UNITS command can be specified in the Preliminary data. See Appendix A-, Preliminary Data.

If UNITS were not employed in the ASAS analysis, the units of all data supplied must be consistent with that adopted for the original data. No modification to reported stresses is possible under these circumstances.

Input Data POST User Manual


2. INPUT Data

As with most of the member programs of the ASAS suite, the input of information and data is divided into two sections. The first is the Preliminary Data and the second is the POST Data.

The Preliminary Data defines the relationship of the run to all the other runs already completed in the project, the backing files required, and also specifies the title of the run. If subsequent processing is required after POST, the data to be saved from the run must also be defined in the Preliminary Data. The full details of these commands, along with examples, are given in Appendix A- of this manual.

A summary of the POST commands available is given in Table 1. Detailed descriptions of each of the commands will be found in the remainder of Chapter 2

2.1. General Principles

The input data for POST are specified according to syntax diagrams similar to the one shown below. The conventions adopted are described in the following paragraphs.

Within a data block, each horizontal branch represents a possible input instruction. Input instructions are composed of keywords (shown in upper-case), numerical values or alphanumerics (shown in lower-case characters), and special symbols. Each item in the list is separated from each other by a comma or one or more blank spaces.

An input line must not be longer than 80 characters.

Numerical values have to be given in one of two forms:

(i) If an integer is required a decimal point must not be supplied.

(ii) If a real is required the decimal point may be omitted if the value is a whole number.

Exponent formats may be utilised when real numbers are required.

For example 0.004 4.0E-3 4.0D-3 are equivalent

similarly 410.0 410 4.10E2 have the same value



The letters A-Z may be supplied in either upper or lower case but no distinction is made between the upper and lower case form. Hence “A” is assumed identical with “a”, “B” with “b” and so on.

For example COMB are all identical strings

Comb

comb

Integer lists are terminated by supplying an END command either on the last line of the integer data, or on the line immediately after. For example

GROU is the same as GROU 1 5 6 END 1 5 6 END

Note that END following immediately after the header line specifies no values. For example

GROU END

In order to reduce the amount of data required, facilities exist to abbreviate the integer lists.

(i) Where the integer list represents all items from an existing list (for example, choosing all groups for

processing) the list may be replaced by the word ALL.

GROU ALL

Note that when ALL is utilised, the keyword END is omitted.

This may not be used where the integer list is to specify new items of information, for example, new

loadcase numbers.

(ii) A sequence of integers may be generated by giving the first value and following this with the negative of

the last value for example 5 -8 generates the numbers 5,6,7 and 8.

If a command is optional, this is shown by an arrow which bypasses the line(s)

A data list is indicated by a horizontal arrow around the list variable

HEADER

list END



Where one or more possible alternative items may appear in the line, these are shown be separate branches for each

2.1.1. Special Symbols

The following is a list of characters which have a special significance to the LOCO input.

* An asterisk is used to define the beginning of a comment, whatever follows on the line will not be

interpreted. It may appear anywhere on the line, any preceding data will be processed as normal. For

example

* THIS IS A COMMENT FOR THE WHOLE LINE

case 4 2.7 * THIS IS A COMMENT FOR PART OF A LINE

’ single quotes are used to enclose some text strings which could contain otherwise inadmissible characters.

The quotes are placed at each end of the string. They may also be used to provide in-line comments

between data items on a given line.

For example

STRUCTURE ’As used for design study’ STRU

, A comma or one or more consecutive blanks will act as a delimiter between items in the line.

For example 5, 10, 15 is the same as 5 10 15

list

KEYWORD1

KEYWORD2



Note that two commas together signify that an item has been omitted. This may be permissible for certain data blocks.

For example 5,, 15 is the same as 5 0 15

Unless otherwise stated in the section describing the data block, omitted numerical values are zero.



Table 1 : Summary of Commands

Units Command Section 2.2

Command Meaning Additional Data Required

Valid For

Note

UNIT Input units definition Unit name(s) all 1

Data Type Commands Section 2.3


Valid For

Note

SHELL SHELL None S

LAMI LAMI type data None L

SBEAM Shell BEAM type data None Sb

BRICK BRICK type data None B

AXIS AXISYMMETRIC type data Data sub-type (on new line) A

HARM HARMONIC type data Data sub-type (on new line) H

SOLID Data sub-type - SOLID elements None A H

SHELL Data sub-type - SHELL elements None A H

Output Axis Commands Section 2.4


Valid For

Note

CONS Consistent local axis system throughout elements

None Sb 2

OUTP Define cartesian output axis system

6 real numbers = 3 direction cosines, 3 coordinates

S 2

OUTR Define radial output axis system 6 real numbers = 2 sets of 3 coordinates

S 2

OUTT Define toroidal output axis system 7 real numbers = 3 coordinates, 3 direction cosines, 1 radius

S 2

OUTB Define beam output axis system 6 real numbers = 2 sets of direction cosines

Sb

SKEW Defines (non orthogonal) x, y, directions for Wood-Armer and reinforcement area calculations

2 real angles (degrees) S



Group Data Commands Section 2.5


Valid For

Note

LAYE Define laminate layers to be processed

Integer list of lamina layers or ALL

L

RDAT Define data required for tensile reinforcement area calculations

4 real numbers = 2 design stresses, 2 cover depths

S 3

TCRD Define data required for tensile/compressive reinforcement area calculations

5 real numbers = 3 design stresses, 2 cover depths

S 3

Group/Element Selection Commands Section 2.6


Valid For

Note

GROU Selection of specified ASAS groups

Integer list of ASAS groups or ALL

all

EXTR Selects extra groups of elements Integer list of user element numbers

all

SKIP Selects elements not to be considered

Integer list of element numbers all

NOAV Prevents stress averaging at nodes None all

AVGR Amalgamates groups for stress averaging

Integer list of ASAS groups or ALL

all

Loadcase Combination Commands Section 2.7


Valid For

Note

NEWC Defines new loadcase numbers Integer list of loadcase numbers all

ADDC Defines loadcases to be used in creating new loadcases

Integer list of ASAS loadcase numbers

all

ADDF Defines loadcases with specific factors used in creating new loadcases

Integer loadcase number followed by integer-real pairs for loadcase number and factor

all



Stress Type Selection Commands Section 2.8


Valid For

Note

FACT Defines a factor to be applied to results

One real factor all

AVST Selects loadcases for processing of averaged stresses

Integer list of loadcase numbers or ALL

all

FANM Forces and Moments printout for average stresses


S

BANM Bending and membrane printout for average stresses


S

PRST Selects loadcases for processing of principal stresses


S Sb B A H

PRVM Selects loadcases for processing of von Mises stresses


S 4

SHRS Selects loadcases for processing of averaged out-of-plane shear forces

Integer list of loadcase numbers S

WOOD Selects loadcases for processing of Wood-Armer moments


S

REIN Selects loadcases for processing of reinforcement areas


S

Control Output Commands Section 2.9


Valid For

Note

PRIN Selects loadcases for printing Integer list of loadcase numbers or ALL

all

PLOT Selects loadcases for plotting Integer list of loadcase numbers or ALL

all

Check Stresses Commands Section 2.10


Valid For

Note

FECS Defines surface stress allowable One real stress value S

FECM Defines mid-plane stress allowable

One real stress value S

VONM Defines level of allowable von Mises stress

One real stress value B A H

TRES Defines level of allowable Tresca stress

One real stress value B A H



Harmonic Combination Commands Section 2.11


Valid For

Note

ANGL Defines angular position around structure for stress output

List of angles H 5

COMB Defines number of new loadcases One integer value H 5

SELE Define new loadcase numbers and titles List of new loadcase numbers and titles

H 5

COS Selects component loadcases and defines factors for combined cases (even expansion about θ=0°)

List of component loadcase numbers and factors

H 5

SIN Selects component loadcases and defines factors for combined cases (odd expansion about θ=0°)

List of component loadcase numbers and factors

H 5

Miscellaneous Commands Section 2.12


Valid For

Note

SECT Defines a section across which stresses are to be calculated

Integer list of ASAS group numbers, section numbers and node numbers

A S

ANGL To print the angle of the principal axes for SHELL type data or define angular location for HARM type data

None for SHELL type data. Real list of angular locations for HARM type data

S H

NAME For PATRAN, instructs POST to create stress files using the first four characters of the name followed by a unique integer and extension, e.g. MODE0001.NOD MODE0002.NOD etc

Name of model to be created in PATRAN database e.g. MODE

all

VMPS This command defines that von Mises stress is to be calculated from principal stresses. If no VMPS command is present the von Mises stress is calculated from average stresses. Not applicable for PATRAN.

S B A H

END Terminate the run all 6 Data types: S - Shell type data Sb - Shell beam type data L - Laminated shell type data B - Brick type data A - Axisymmetric type data H - Harmonic type data



Notes

1. UNIT command may only be used if units have been specified in the preceding ASAS run.

2. Only one is applicable to a group of elements, however different groups may have different output axis within the same run. If none are present then CONS is assumed.

3. RDAT and TCRD may be used in same run but must apply to different groups.

4. For shell elements von-Mises stresses are not printed but the PRVM command will cause them to be added to the plot file.

5. For HARM type jobs, these commands must follow the data sub-type command.

6. Mandatory END command: all other decks are optional subject to note 2

2.2. UNITS Command

Specifies the units associated with subsequent data. This command is only valid if UNITS were employed in the ASAS analysis (see Section 1.9).

Parameters

UNITS : keyword

unit : name of unit to be utilised (see below)

Note

Force, length and angular unit may be specified. Only those terms which are required to be modified need to be specified, undefined terms will default to those of the analysis global units unless previously overwritten by another UNITS command. The default angular unit is degrees for all data types.

Valid unit names are as follows:

Length METRE(S) M CENTIMETRE(S) CM MILLIMETRE(S) MM FOOT,FEET FT INCH,INCHES IN

Force unit NEWTON(S) N KILONEWTON(S) KN

unitUNITS



MEGANEWTON(S) MN TONNEFORCE(S) TNEF POUNDAL(S) PDL POUNDFORCE LBF KIP(S) KIP TONFORCE(S) TONF KGFORCE(S) KGF

Angular unit RADIAN(S) RAD(S) DEGREES(S) DEG(S)

The UNITS command may be repeated throughout the data deck thus permitting the greatest flexibility in the data input.



Example

Command Operational Units Notes

SYSTEM DATA AREA 50000

. UNITS do not have to

. appear in the Preliminary

. data, see Section 1.9 UNITS N M NEWTON, METRES, DEGREES and Appendix A-. .

.

.

END

SHELL NEWTONS, METRES, DEGREES Default global analysis CONS units except that angular GROU input is in degrees ALL

AVST

ALL

UNIT MM NEWTONS, MILLIMETRES, DEGREES Stress now input in FECS N/mm2

200.0

END

2.3. Data Type Commands

2.3.1. Data Type and Sub-Type Commands

This command defines the type of elements to be processed in the POST run and must be the first command to follow the preliminary data.



Parameters

SHELL : keyword to denote that one or more of the following element types are to be processed: Shell GCS6, GCS8, TCS6, TCS8, TBC3, QUS4 Plate SLB8, TRB3 Membrane QUM8, QUM4, TRM6, TRM3 Sandwich SND6, SND8, SND12, SND16 Only one element type will be processed for each group defined (see Section 1.4)

LAMI : keyword to denote that laminated shells are to be processed: QUS4, TCS6 and TCS8 elements

SBEAM : keyword to denote that shell beam elements are to be processed: TCBM or GCB3 elements

BRICK : keyword to denote that brick elements are to be processed: BRK6, BRK8, BR20, BR32, TET4, TE10 elements

AXIS : keyword to denote that the axisymmetric elements are to be processed

SOLID : subcommand to AXIS to denote that axisymmetric solid elements are to be processed: TRX3, TRX6, QUX4, QUX8 elements

SHELL : subcommand to AXIS to denote that the axisymmetric shell element is to be processed: ASH2 elements

If neither subcommand is given, SOLID is assumed.

HARM : keyword to denote that the axisymmetric harmonic elements are to be processed.

SHELL

LAMI

BRICK

AXISSOLID

SHELL

SOLID

SHELLHARM

SBEAM



SOLID : subcommand to HARM to denote that harmonic solid elements are to be processed: THX3, THX6, QHX4, QHX8 elements

SHELL : subcommand to HARM to denote that the harmonic shell element is to be processed: AHH2 elements

If neither subcommand is given, SOLID is assumed.

Note

All POST runs require either SHELL, LAMI, SBEAM, BRICK, AXIS or HARM as the first command following the preliminary data; they are mutually exclusive options.

2.4. Output Axis Commands

2.4.1. CONS Command (SHELL or SBEAM data)

Specifies that the element local axis systems are consistent and that no stress reorientation is required (see Section 1.6)

Parameters

CONS : keyword

When CONS is specified, any groups referenced by subsequent GROU and EXTR group commands will be assumed to have consistent local element axis systems until a new output axis system is defined (OUTP, OUTR, OUTT, OUTB). If no output command is supplied, CONS will be assumed.

Notes

1. A group may only be assigned one axis system within the same run. Different groups however, may have different output axis systems.

2. This command does not make elements within a group have consistent axes. If they do not already have consistent axes in the ASAS model then the CONS command must not be used otherwise invalid stress averaging will occur. In this instance one of the alternative output commands (OUTP, OUTR, OUTT, OUTB) must be used.

Example

CONS



CONS

GROU

1 5 END

EXTR

10 15 16 17 END

2.4.2. OUTP Command (SHELL data only)

Defines a cartesian/cylindrical output axis system into which all nodal stresses are to be converted prior to nodal averaging (see Section 1.6)

Parameters

OUTP : keyword

dx,dy,dz : direction cosines of the reference direction with respect to the global axis system. (Real)

x,y,z : global coordinates of the reference point. (Real)

When OUTP is specified, any groups referenced by subsequent GROU and EXTR group commands will adopt the output axis system defined by the direction cosines and reference point until a new output axis system is defined (CONS, OUTR, OUTT, OUTP).

Note

A group may only be assigned one axis system within the same run. Different groups, however, may have different output axis systems.

Example

OUTP

0.7071 0.7071 0.0 10.0 0.0 0.0

GROU

1 5 END

OUTP

dx dy dz x y z



EXTRA

10 15 16 17 END

2.4.3. OUTR Command (SHELL data only)

Defines a radial/spherical output axes system into which all nodal stresses are to be converted prior to nodal averaging (see Section 1.6).

Parameters

OUTR : keyword

xo,yo,zo : global coordinates of the centre point. (Real)

xr,yr,zr : global coordinates of the reference point. (Real)

When OUTR is specified, any groups referenced by subsequent GROU and EXTR group commands will adopt the output axis system defined by the two pairs of coordinates until a new output axis system is defined (CONS, OUTP, OUTT, OUTR).

Note


Example

OUTR

1.0 0.0 10.0 1.0 0.0 2.0

GROU

1 5 END

EXTRA

10 15 16 17 END

OUTR

xo yo zo xr yr zr



2.4.4. OUTT Command (SHELL data only)

Defines a toroidal output axes system into which all nodal stresses are to be converted prior to nodal averaging (see Section 1.6).

Parameters

OUTT : keyword

xc,yc,zc : global coordinates of centre of torus (Real)

dx,dy,dz : direction cosines of major axis (Real)

r : major radius (Real)

When OUTT is specified, any groups referenced by subsequent GROU and EXTR group commands will adopt the output axis system defined by the specified torus until a new output axis system is defined (CONS, OUTR, OUTT, OUTP).

Note


Example

OUTT

100.00 0.0 100.0 0.0 1.0 0.0 25.0

GROUP

2.4.5. OUTB Command (SBEAM data only)

Specifies information to determine output axis system for shell beam elements (see Section 1.6)

OUTT

xc yc zc dx dy dz r



Parameters

OUTB : keyword

dxx,dxy,dxz : directions cosines for x-axis reference direction with respect to the global axis system. (Real)

dzx,dzy,dzz : direction cosines for z-axis reference direction with respect to the global axis system. (Real)

When OUTB is specified, any groups referenced by subsequent GROU and EXTR group commands will adopt the output axis system defined by these direction cosines until a new output axis system is defined (CONS, OUTB).

Note


Example

OUTB

0.7071 0.7071 0.0 0.0 0.0 1.0

GROU

7 5 END

EXTRA

10 15 16 17 END

2.4.6. SKEW Command (SHELL data only)

Defines the local axes for Wood-Armer moment and reinforcement area calculations.

OUTB

dxx dxy dxz dzx dzy dzz



Parameters

SKEW : keyword

angx : angle that local x axis makes to the output x axis (CONS, OUTP, OUTR or OUTT) (Real)

angy : angle between local y axis and local x axis. (Real).

Notes

1. The WOOD/REIN commands normally assume that orthogonal axes are in use. The SKEW command allows non-orthogonal axes to be defined.

2. The angles defined are measured in a conventional right-handed system. The units are degrees.

Example

SKEW

22.5 78.5

2.5. Group Data Commands

2.5.1. LAYE Command (LAMI data only)

Specifies which layers of a laminated shell are to be processed.

SKEW

angx angy



Parameters

LAYE : keyword

ilay : individual layers to be processed

END : keyword to denote the end of the current block of layer data. If the list of layers continues onto

subsequent lines, END is required on the last line only.

ALL : keyword to denote that all layers are to be reported. END not required.

Note

When LAYE is specified, any groups referenced by subsequent GROU and EXTR group commands will have the layers processed that are defined on this command. If no LAYE command is given then all layers of the groups selected will be processed.

Example

LAYE

1 2 5 6 END

GROU

1 2 END

LAYE

ALL

EXTR

11 1 -20 END

LAYE

ilay END

ALL



2.5.2. RDAT Command

Specifies details of allowable stresses and cover depths for tensile (only) reinforcement calculations. For this case it is assumed that all compressive stress is carried by the matrix (e.g. concrete) alone and all the tensile stress by the reinforcement (e.g. steel) alone.

Parameters

RDAT : keyword

rdstrs : reinforcement design stress (Real)

mdstrs : matrix design stress (Real)

cdeps : cover depths (Real)

Notes

1. If cdeps is omitted the cover depth for all reinforcing will default to 10% of the shell thickness.

2. If only one cdeps value is specified, this is taken as the cover depth for all reinforcing.

3. If two cdeps values are specified, these are taken as the top and bottom surface cover depths respectively.

4. If four cdeps values are specified, these are taken as the top X and Y direction cover depths followed by the bottom X and Y direction cover depths.

5. This data applies to any groups of elements defined on subsequent GROU or EXTR commands, until superceded by further RDAT or TCRD commands.

6. RDAT and TCRD may appear in the same run but may not be for the same group of elements.

RDAT

rdstrs cdepsrdstrs mdstrs



2.5.3. TCRD Command

Specifies details of allowable stresses and cover depths for tensile/compressive reinforcement calculations. For this case it is assumed that the tensile stress is carried by the reinforcement (e.g. steel) alone, but the compressive stress is carried by both the matrix (e.g. concrete) and the reinforcement.

Parameters

RDAT : keyword

rdtstr : tensile reinforcement design stress (Real)

rdcstr : compressive reinforcement design stress (Real)

mdstrs : matrix design stress (Real)

cdeps : cover depths (Real)

Notes

1. If cdeps is omitted the cover depth for all reinforcing will default to 10% of the shell thickness.

2. If only one cdeps value is specified, this is taken as the cover depth for all reinforcing.

3. If two cdeps values are specified, these are taken as the top and bottom surface cover depths respectively.

TCRD

cdepsrdtstr rdcstr mdstrs



4. If four cdeps values are specified, these are taken as the top X and Y direction cover depths followed by the bottom X and Y direction cover depths.

5. This data applies to any groups of elements defined on subsequent GROU or EXTR commands, until superseded by further RDAT or TCRD commands.

6. RDAT and TCRD may appear in the same run but may not be for the same group of elements.

2.6. Group/Element Selection Commands

2.6.1. GROU Command

Specifies the ASAS group numbers to be processed by subsequent execution commands (AVST, PRST, SHRS, WOOD and REIN)

Parameters

GROU : keyword

igroup : ASAS group number to be processed (Integer). All the group numbers specified must exist

otherwise POST will stop after data checking.

GROU

igroup END

ALL



END : keyword to denote the end of the current block of group number data. If the list of group numbers

continues onto subsequent lines, END is required on last line only.

ALL : keyword to indicate that all groups are selected. END is not required.

Note

If this command is omitted, and provided no extra groups are specified (see Section 2.6.2, EXTR groups) then all the ASAS groups will be processed by default. If this command is omitted, but extra groups are defined, then none of the ASAS groups will be processed.

Examples

(i) To process ASAS groups 1 2 3 4

GROU

1 -4 END

(ii) To process all ASAS groups

GROU

ALL

(iii) To process ASAS groups 1,3,5,7,10,12,14

GROU

1 3 5 7

10 12 14 END

2.6.2. EXTR Command

Defines new group numbers and assigns elements to the groups for processing by subsequent execution commands (AVST, PRST, SHRS, WOOD and REIN)

Parameters

EXTR

igroup ENDielem



EXTR : keyword

igroup : group number for new group to be generated (Integer). This group number must be unique and must not exist in the original ASAS analysis.

ielem : user element numbers to be included in the new group (Integer).

END : keyword to denote the end of the current block of extra group data. If the list of element numbers continues onto subsequent lines, END is required on last line only.

Note

1. One extra group is defined by each EXTR group command. Up to 50 groups may be processed at a time.

2. This command effectively removes the elements from their original ASAS group since an element may only be in one group at a time.

3. EXTR groups may be redefined with different lists of elements in separate runs of POST provided the Interface file is not saved from run to run.

4. Note that if EXTR groups are created in POST, then the CREATE Command should be used on the SAVE FEMS line.

Examples

(i) New group 12 contains elements 7 to 35

EXTR

12 7 -35 END

(ii) New group 5 contains elements 1 to 10 and new group 7 contains elements 11 to 20

EXTR

5 1 -10 END

EXTR

7 11 12 13 14 15 -20 END

2.6.3. SKIP Command

Specifies user element numbers which are to be excluded from the analysis.



Parameters

SKIP : keyword

ielem : user element number to be skipped (Integer)

END : keyword to denote the end of the SKIP data. If the list of element numbers continues onto

subsequent lines, END is required on last line only.

Note

1. This command is used to remove elements from an ASAS group. If the skipped elements need processing on their own, the EXTR group command should be used which will remove the elements in the extra group from their original ASAS groups.

2. Up to 500 elements may be skipped.

Example

SKIP

1 7 9 END

2.6.4. NOAV Command

Specifies that no averaging of adjacent element stresses is to be carried out.

Parameters

SKIP

ENDielem

NOAV



NOAV : keyword

Notes

1. By default, nodal stresses of adjacent elements within a group are averaged and reported. For model checking it may be useful to manually check the absolute variation from element to element in a consistent axis set using this command together with an output axis system definition. (OUTP, OUTR, OUTT).

2. With the NOAV command no thickness checks are carried out to ensure that all elements at a node have the same thickness.

3. This command will require a significantly larger data area (see Appendix A.2) and will produce larger results files than usual and thus should be used with care.

2.6.5. AVGR Command

Specifies a set of group numbers which are to be considered as one single group for the purposes of stress averaging.

Parameters

AVGR : keyword

igroup : group number (Integer). This may be either an ASAS group or one defined in an earlier EXTR

group command.

END : keyword to denote the end of the current block of averaged group data. If the list of group

numbers continues onto subsequent lines, END is required on last line only.

ALL : keyword to indicate that all groups are selected. END is not required.

Notes

1. By default, stress averaging only occurs between elements which are in the same group. (See Section 1.4). There may be situations, however, where groups of elements require different axis sets but stress averaging across the group boundaries is both desirable and meaningful (see Figure 10). This may be

AVGR

ENDigroup

ALL



achieved by use of the output axis commands (CONS, OUTP, OUTR, OUTT) and AVGR (See Section 1.6.4).

2. The results will be reported under the first group number appearing in the list.

Example (see Figure 10)

OUTP 0.0 0.0 1.0 0.0 0.0 50.0 GROUP 1 END OUTT 50.0 0.0 100.0 0.0 1.0 0.0 50.0 GROUP 2 END OUTP 1.0 0.0 0.0 100.0 0.0 150.0 GROUP 3 END OUTR 200.0 0.0 150.0 150.0 0.0 200.0 GROUP 4 END AVGR 1 2 3 4 END

2.7. Loadcase Combination Commands

2.7.1. NEWC Command

Specifies the numbers and titles of new loadcases that are to be created using the ADDC and ADDF commands (see Sections 2.7.2 and 2.7.3 respectively).

Parameters

NEWC : keyword

newcase : number of new loadcases to be created (Integer).

NEWC

newcase END

loadcase `title'



END : keyword to denote the end of the current block of new loadcase numbers. If the list of new

loadcase numbers continues onto subsequent lines, END is required on last line only.

For each loadcase defined by newcase

loadcase : loadcase number which must also appear in the newcase list above. (Integer)

title : title associated with the new loadcase number. (Maximum 40 characters)

Note

The order of the title lines is not important.

Example

NEWC

5 7 9 11 END

5 ’FIRST COMBINATION’

9 ’THIRD COMBINATION’

7 ’SECOND COMBINATION’

11 ’LAST COMBINATION’

2.7.2. ADDC Command

Specifies the constituent loadcases to be added together to form a new loadcase defined in the NEWC command (see Section 2.7.1).

Parameters

ADDC : keyword

keywrd : second keyword to define the type of summation to be carried out to the constituent loadcases

defined on the following line(s). Valid options are:

SSUM simple summation (default)

MAXE maximum envelope

MINE minimum envelope

ADDC

newcase loadcase

(keywrd)

END



MXAE maximum absolute envelope

ABSS absolute sum

SRSS square root sum square

REEN reinforcement calculation envelope

WDME Wood-Armer moment envelope

newcase : new loadcase number which must have been defined using the NEWC command. (Integer).

loadcase : existing loadcase number to be used in the creation of the new loadcase (see notes below).

(Integer)

END : keyword to denote the end of the current block of constituent data. If the list of loadcase numbers

continues onto subsequent lines, END is required on last line only.

Notes

1. The constituent loadcases are factored by the value defined in the latest FACT command.

2. Either ADDC and/or ADDF commands must be used for each of the new loadcases defined on the NEWC command.

3. The loadcase list may include new loadcases defined on earlier ADDC or ADDF commands.

4. Appendix D- gives details of summation types.

Example

ADDC SSUM

5 2 -4 END

2.7.3. ADDF Command

Specifies the constituent loadcases, together with their factors, to be added together to form a new loadcase defined in the NEWC command (see Section 2.7.1).

Parameters

ADDF : keyword

ADDF

newcase loadcase

(keywrd)

ENDfactor



keywrd : second keyword to define the type of summation to be carried out to the constituent loadcases

defined on the following line(s). Valid options are:

SSUM simple summation (default)

MAXE maximum envelope

MINE minimum envelope

MXAE maximum absolute envelope

ABSS absolute sum

SRSS square root sum square

MXLS maximum limit stress

MNLS minimum limit stress

WDME Wood-Armer moment envelope

REEN reinforcement calculation envelope

newcase : new loadcase number which must have been defined using the NEWC command. (Integer)

loadcase : existing loadcase number to be used in the creation of the new loadcase (see notes below).

(Integer)

factor : factor to be applied to the loadcase. (Real) For the MXLS and MNLS two factors per loadcase are

required.

END : keyword to denote the end of the current block of constituent data. If the list of loadcase numbers

continues onto subsequent lines, END is required on the last line only.

Notes

1. Either ADDC and/or ADDF commands must be used for each of the new loadcases defined as the NEWC command.

2. The use of ‘-’ to indicate a range of integers is prohibited in this command.

3. The loadcase list may include new loadcases defined on earlier ADDC or ADDF commands.

4. Appendix D- gives details of summation types.

Example

ADDF SSUM 7 1 1.5 2 0.5 END

ADDF MXLS 11 1 1.5 1.0 2 0.5 0.0 END



2.8. Stress Type Selection Commands

2.8.1. FACT Command

Specifies a factor to be applied to the stresses from the loadcases defined by subsequent execution commands (AVST, PRST, SHRS, WOOD and REIN) or loadcases referred to with the ADDC command.

Parameters

FACT : keyword

factor : scaling factor to be applied to subsequent loadcases. (Real)

Note

The factor remains on the selected loadcases until it is overwritten by another FACT command.

The default value is 1.0

Example

FACT

105.0

2.8.2. AVST Command

Specifies the loadcases for which average stresses are to be calculated.

Parameters

FACT

factor

AVST

ENDloadcase

ALL



AVST : keyword

loadcase : loadcase number to be processed (Integer). This must either appear in the original ASAS analysis

or be defined in a NEWC command.

END : keyword to denote the end of the current block of averaged stress data. If the list of loadcase


ALL : keyword to indicate that all loadcases are selected.

Notes

1. If AVST and PRST commands are both omitted then the averaged stresses and principal stresses (if applicable) will be calculated for all loadcases in the ASAS run.

2. For BRICK, AXIS and HARM data types, the von Mises equivalent stress is calculated during printing of average nodal stresses. The formulae are given in Appendix C-.

If the von-Mises equivalent stress exceeds the allowable value set by a previous VONM command (see

Section 2.10.2) the factor by which the allowable value is exceeded is also printed.

Example

(i) AVST 1 4 6 END

(ii) AVST ALL

2.8.3. FANM Command (SHELL data only)

Specifies the loadcases for average stress calculation where FORCES and MOMENTS are required, as opposed to surface stresses.

Parameters

FANM

ENDloadcase

ALL



FANM : keyword

loadcase : loadcase number to be processed. (Integer). This must either appear in the original ASAS

analysis or be defined in a NEWC command.

END : keyword to denote the end of the current block of force and moment data. If the list of loadcase

numbers continues onto subsequent lines, END is required on the last line only.

ALL : keyword to indicate that all loadcases are selected. END is not required.

Notes

1. If FANM is specified, the nodal averaged values are output as force/unit length and moment/unit length instead of stresses at the top, middle and bottom surfaces.

2. For TRB3 elements this command will produce summed through thickness shears for each node.

3. FANM only controls the type of values output. AVST is also needed if nodal averaged values are required.

Example

FANM

1 3 END

2.8.4. BANM Command (SHELL data only)

Specifies the loadcases for average stress calculation where BENDING and MEMBRANE stresses are required, as opposed to surface stresses.

Parameters

BANM : keyword

BANM

ENDloadcase

ALL



loadcase : loadcase number to be processed (Integer). This must either appear in the original ASAS analysis


END : keyword to denote the end of the current block of bending and membrane stress data. If the list of

loadcase numbers continues onto subsequent lines, END is required on the last line only.


Note

1. If BANM is specified, the nodal averaged values are output in the form of bending and membrane stresses instead of stresses at the top, middle and bottom surfaces.

2. BANM only controls the type of values output. AVST is also needed if odal averaged values are required.

Example

BANM

4 -6 END

2.8.5. PRST Command

Specifies the loadcases for which principal stresses are to be calculated.

Parameters

PRST : keyword

loadcase : loadcase number to be processed. (Integer). This must either appear in the original ASAS analysis


END : keyword to denote the end of the current block of principal stress data. If the list of loadcase



PRST

ENDloadcase

ALL



Notes

1. If AVST and PRST commands are both omitted then the averaged stresses and principal stresses will be calculated for all loadcases in the ASAS run.

2. During the processing of principal stresses for solid elements (including axi-symmetric) the Tresca stress and von Mises equivalent stress are calculated. The formulae are given in Appendix C-.

3. For SHELL data, P3 is the through thickness stress and is equal to zero, and hence the Tresca stress becomes the greater of the P1, P2 or P1 - P2 values. This value of Tresca stress is flagged with an asterisk in the printout but not printed separately.

4. The von-Mises equivalent stress is not printed but if the PRVM command is specified, the value is written to the plot file. See Section 2.8.6 and A.12.

5. PRST may not be used with the SBEAM data type.

Example

PRST 5 2 1 END

PRST ALL

2.8.6. PRVM Command

Specifies the loadcases for which von-Mises equivalent stresses are to be processed.

Parameters

PRVM : keyword

loadcase : loadcase number to be processed (Integer). This must either appear in the original ASAS analysis or be defined in a NEWC command.

PRVM

ENDloadcase

ALL



END : keyword to denote the end of the current block of von-Mises data. If the loadcase numbers continue onto subsequent lines, END is required on the last line only.


Notes

1. This command must be used in conjunction with the PRST command, see section 2.8.5.

2. The von-Mises stress is not printed for shell elements even when the PRVM command is used.

3. The PRVM command causes the von-Mises stresses to be written to the plot file.

4. The formulae used to calculate the von-Mises stress are given in Appendix C-.

Example

PRVM

3 7 9 END

2.8.7. SHRS Command (SHELL data only)

Specifies the loadcases for which average out of plane shear force/unit lengths are to be calculated.

Parameters

SHRS : keyword

loadcase : loadcase number to be processed (Integer). This must either appear in the original ASAS analysis or be defined in a NEWC command.

END : keyword to denote the end of the current block of SHRS data. If the loadcase numbers continue onto subsequent lines, END is required on the last line only.


SHRS

ENDloadcase

ALL



Notes

1. This command should not be used for TRB3 elements which are covered separately by the SECT command in Section 2.12.1 (see also Section 1.7)

2. SHRS only controls the type of values output. AVST is also needed if nodal averaged values are required.

Example

SHRS

3 7 9 END

2.8.8. WOOD Command (SHELL data only)

Specifies the loadcase numbers for which Wood-Armer moments are to be calculated. Only valid for SHELL data and element types GCS6, GCS8, TCS6, TCS8, TBC3, QUS4, SLB8 and TRB3.

Parameters

WOOD : keyword

loadcase : loadcase numbers to be processed (Integer). This must either appear in the original ASAS analysis


END : keyword to denote the end of the current list of loadcases. If the list of loadcase numbers



Notes

1. The formulae used for calculating Wood-Armer moments are given in Appendix C-.

WOOD

ENDloadcase

ALL



2. If Wood-Armer moment envelopes are required, the WDME combination type should be used on an ADDC/ADDF command (see Section 2.7.2/2.7.3).

3. Specifying WOOD for a loadcase will automatically invoke the FANM command, unless BANM has been specified, in which case Wood-Armer stresses are produced.

Example

WOOD

5 3 END

2.8.9. REIN Command (SHELL data only)

Specifies the loadcase numbers for which reinforcement areas are to be calculated. Only valid for SHELL data and element types GCS6, GCS8, TCS6, TCS8, TBC3, QUS4, SLB8 and TRB3.

Parameters

REIN : keyword

loadcase : loadcase numbers to be processed (Integer). This must either appear in the original ASAS analysis


END : keyword to denote the end of the current list of loadcases. If the list of loadcase numbers



Notes

1. The formulae used for calculating Reinforcement Areas are given in Appendix C-.

REIN

ENDloadcase

ALL



2. If reinforcement area envelopes are required, the REEN combination type should be used on an ADDC/ADDF command (see Section 2.7.2/2.7.3).

3. Specifying REIN for a loadcase will automatically invoke the FANM command.

Example

REIN

5 3 END

2.9. Control Output Commands

2.9.1. PRIN Command

Specifies which loadcases are to be printed. Only loadcases that are processed may be printed (AVST, PRST, SHRS, WOOD and REIN commands).

Parameters

PRIN : Keyword

loadcase : loadcase number to be printed. (Integer)

END : keyword to denote the end of the current block of print data. If the list of loadcase numbers


ALL : keyword to indicate all loadcases are selected. END is not required.

Notes

1. By default all loadcases that are processed will be printed.

PRIN

ENDloadcase

ALL



2. The PRIN command must only be used with a SAVE plot FILE command (see Appendix A.12). In this case, all cases processed will be written to the plot file.

Example

To print loadcases 5 and 6 only

PRIN

5 6 END

To suppress printing of all the loadcases

PRIN

END

2.9.2. PLOT Command

Used to specify which loadcases are to be saved for processing with any valid plotting program. Only loadcases that are processed may be plotted (AVST, PRST, SHRS, WOOD and REIN commands). A SAVE plot FILE command must be supplied in the preliminary data if plotting is required (see section A.12).

Parameters

PLOT : keyword

loadcase : loadcase number to be saved for plotting. (Integer)

END : keyword to denote the end of the PLOT data. If the list of loadcase numbers continue onto

subsequent lines, END is required on the last line only.


PLOT

ENDloadcase

ALL



Notes

1. If the PLOT command is omitted then all loadcases that are processed will be saved for plotting if a SAVE plot FILE command has been supplied, otherwise none is saved.

2. If the PLOT command is used and no SAVE plot FILE command has been specified, the program will terminate after reading the data.

Example

Cases 1,2,3,6,7 and 8 will be added to the plot file.

PLOT

1 2 3 6 -8 END

All loadcases processed will be added to the plot file.

PLOT

ALL

No results will be added to the plot file.

PLOT

END

2.10. Check Stresses

2.10.1. FECS and FECM Commands (SHELL data only)

Specifies an effective surface or membrane stress to be used as the check stress to be applied to subsequent average and principal stress calculations.

Parameters

FECS : keyword to denote that an effective surface stress is to be defined.

FECM : keyword to denote that an effective membrane stress is to be defined.

stress

FECS

FECM



stress : check stress. (Real). A value of zero implies no checking.

Note

If the FANM command is in operation for any of the loadcases then no stress checking will be carried out.

Example

Command Current Check Stress Values

AVST FECS FECM

6 END 0.0 0.0

FECM

150.0

AVST

1 2 END 0.0 150.0

FECS

200.0

PRST

5 END 200.0 150.0

2.10.2. VONM Command

Specifies a user defined von Mises stress level against which the calculated von Mises stresses will be checked, for loadcases defined by subsequent AVST and PRST commands.

Parameters

VONM : keyword

stress : von Mises stress check value (Real). A value of zero implies no checking

VONM

stress



Note

The stress check value remains for selected loadcases until it is overwritten by a subsequent VONM command.

Example

VONM

5.0

2.10.3. TRES Command

Specifies a user defined Tresca stress level against which the calculated Tresca stresses will be checked, for loadcases defined by a subsequent PRST commands.

Parameters

TRES : keyword

stress : Tresca stress check value (Real). A value of zero implis no checking.

Note

The stress check value remains for selected loadcases until it is overwritten by a subsequent TRES command.

Example

TRES

10.0

TRES

stress



2.11. Harmonic Combination Commands

2.11.1. Data for Harmonic Analyses

If a Fourier series type of analysis is being carried out on the harmonic solid elements, THX3, QHX4, THX6 and QHX8, data must be defined for the constituent structures and loadcases (see Section 1.2.5). The following commands provide this additional information and must follow the HARM and BRICK / SHELL command.

Parameters

See following sections for details of each command.

ANGL

COS

SIN

COMB numcomb

SELE newcase title

STRUCTURE struct

COMPONENT struct tree

angl END

loadcase factor

END



Note

The harmonic combination commands must be omitted in a harmonic re-run and the loadcase details will be obtained from the previously saved files.

2.11.2. ANGL Command (HARM Data only)

Specifies the angular positions around the structure at which stress output is required.

Parameters

ANGL : keyword

angle : angle at which results are required. (Real)

END : keyword to denote the end of the angle data.

Notes

1. A maximum of 50 angular stations are permitted.

2. Continuation lines are permitted, the END appearing at the end of the last continuation line.

3. The ANGL command is compulsory for all HARM data files and must be the first data after the HARM BRICK / SHELL data type commands.

Example

ANGL

20.0 33.0 42.0 57.0 30.0 END

2.11.3. COMB Command (HARM data only)

Specifies the number of harmonic combinations which are to be created by this run.

ANGL

angle END



Parameters

COMB : keyword

numcomb : number of harmonic combinations to be created. Must be 9 or less. (Integer)

Note

The COMB command must immediately follow the last ANGL command

Example

COMB 3

2.11.4. SELE Command (HARM data only)

This command identifies the combination number and title to be associated with the harmonic combination created by the subsequent commands.

Parameters

SELE : keyword

combno : user combination number for this case (Integer)

This value must be 9 or less (see note below).

title : combination title, up to 40 characters.

COMB numcomb

SELE combno ’title’



Notes

1. The combination number specified on the SELE command line is used in conjunction with the specified angular positions to generate internal loadcase numbers for reporting results.

2. The combination number defined on the SELE command is multiplied by 1000 and added to the integer angle of a station (in degrees) to arrive at a representative loadcase number. For example,

if the SELE command defines a new combination 5 and angles of 20.0, 32.0 and

47.0 degrees have been specified on the ANGL command, the following internal

loadcases will be generated:- 5020, 5032 and 5047.

3. There must be as many SELE commands supplied as the number defined on the COMB command.

Example

SELE 2 ’CASE 7 HARMONIC 0 + CASE 5 HARMONIC 2’

2.11.5. COS and SIN Commands (HARM data only)

Specifies constituent loadcase numbers and factors to be used in the generation of a harmonic combination, together with optional information defining the structure or component to which the loadcases are relevant.

Parameters

STRUCTURE : keyword

SIN

COS

STRUCTURE struct

COMPONENT struct tree

loadcase factor

END



struct : 4-character ASAS structure name identifying which structure within the current project is to be accessed

tree : this is the path down the component tree from the given structure in sname to the component being used for the POST combinations. If processing a global structure run from a multilevel analysis, i.e. the component tree is not required, use the STRUCTURE command instead.

COS : keyword to indicate that the loadcases selected are symmetrically expanded about the reference direction (θ=0.0), i.e. the loading is maximum at θ=0.0)

SIN : keyword to indicate that the loadcases selected are antisymmetrically expanded about the reference direction (θ=0.0), i.e. the loading is maximum at an angle of θ=π/2n, where n is the harmonic number

loadcase : constituent ASAS loadcase number (Integer)

factor : factor by which the constituent loadcase is to be multiplied (Real)

END : keyword to denote the end of the current block of constituent loadcase information. Required on the last COS or SIN command for the current SELE command.

Note

If all the constituent load information is from one ASAS run, i.e. as defined in the Preliminary data, the COMPONENT and STRUCTURE commands are unnecessary. If the loadcase information is drawn from more than one component or structure, the appropriate command should precede the relevant COS or SIN command. Having specified the STRUCTURE or COMPONENT in this way, POST will continue to draw information from the loadcase selection commands accordingly. To avoid ambiguities it is recommended that the STRUCTURE or COMPONENT commands be defined explicitly at all times.

Example

Loadcases 1, 2 and 3 are taken from the assembled component defined in the Preliminary data. To these are added loadcases 5 and 7 from assembled component CMP9 of structure WQH2.

SELE 6 COMBINED LOADCASE

COS

1 1.3 2 2.4

SIN

3 -2.3

COMPONENT WQH2 CMP9

SIN

5 1.0

COS

7 2.0

END



2.12. Miscellaneous Commands

2.12.1. SECT Command

Specifies a section across which stresses are to be calculated and printed for the loadcases defined with the AVST command. This command is only valid for AXIS type jobs or to process summed out of plane shears for TRB3 elements (see Section 1.7).

Parameters

SECT : keyword

igroup : the ASAS group number across which the sectional stresses are to be calculated (Integer).

sectid : identifying number for each section defined across the ASAS group.

nodenm : node numbers defining the section. (Integer).

END : keyword to denote the end of the current block of data. If the list of node numbers continues onto

subsequent lines, END is required on last line only.

Notes

1. For each section identifier defined on the igroup line, there must be a related sectid line.

2. Up to 17 nodes may be specified across a section. These nodes should form a ”straight” line although they do not necessarily have to follow the edge of an element (the section may pass diagonally across elements). The nodes defining a given section must be in the same order as the nodes across the ASAS model.

3. Each section may be at any angle to the global axis system. A new reference plane, defined by the first and last nodes in the list, will be calculated for each section. All averaged nodal stresses are then resolved normal and parallel to this plane before the member components are evaluated.

Example

Three sections are to be numbered 22, 23 and 24, taken across ASAS group number 2. Section 22 has nodes 1, 8, 9, 10 and 14 across it

SECT

igroup sectid

sectid nodenm

END

END



Section 23 has nodes 11, 18, 19, 20 and 24 across it Section 24 has nodes 21, 28, 30, 34 and 29 across it

SECT 2 22 -24 END 22 1 8 9 10 14 END 23 11 18 19 20 24 END 24 21 28 30 34 29 END

2.12.2. ANGL Command (SHELL data only)

Requests output of the direction of first principal stress instead of (P1 - P2)

Parameters

ANGL : keyword

Notes

1. If present, the angle of the first principal stress measured from the output x-axis is reported instead of the principal stress difference (P1 - P2).

2. This command should not be confused with the ANGL command in a HARM run. (See Section 2.11.2)

2.12.3. END Command

Specifies the end of the data. This command must be present.

Parameters

END : compulsory keyword

ANGL

END

Examples POST User Manual


3. Examples

3.1. Example 1: Default Data

This example shows the minimum of data necessary to run POST.

The preliminary data defines the space required (30000 words), the project name and the ASAS results to be processed (LVW1, a single level analysis), a title and the option GOON (to prevent termination if any warnings are issued).

Two POST commands are used: SHELL to indicate that the shell elements of LVW1 are to be processed and END to denote the end of the post data. For this particular example it is assumed that the local axes of the shell elements are consistent. POST will also make this assumption and print a warning which necessitates the GOON option in the preliminary data. Similar default data may be used for each of the POST data types by substituting the appropriate data type keyword.

POST will process all loadcases and print average and principal stresses. No files will be saved for plotting.


PROJ LVW1

JOB POST

TITLE POST PROCESSING FOR LVM MODEL

OPTION GOON END

END

SHELL

END

3.2. Example 2: Simple Shell Result Processing

This example shows the data file for running POST after a single level ASAS analysis. The structure name to be accessed is SBSS from project SBSS. As the elements within each group are all aligned similarly with regard to the global axes, the CONS option is selected. Elements from Groups 1, 3, 5, 6, 7 and 9 are to be processed. The mid-plane check stress is 50.0 and the surface check stress is 75.0. The average stresses and principal stresses are to be processed for user loadcases 1, 3, 7 8, 9, 10, 11 and 14. The average stresses and principal stresses are to be printed for user loadcases 1 and 10. All processed stresses will be written to a FEMVIEW file with default filename SBSSFS and default model name SBSS.


PROJ SBSS

JOB POST

TITLE EXAMPLE ILLUSTRATING SHELL DATA

STRUCTURE SBSS

OPTIONS END



SAVE FEMS FILES

END

SHELL

CONS

GROU

1 3 5 -7 9 END

FECM

50.0

FECS

75.0

AVST

1 3 7 -11 14 END

PRST

1 3 7 -11 14 END

PRIN

1 10 END

END

3.3. Example 3: Simple Axi-symmetric Result Processing

This example shows the data deck for running POST after a single level ASAS analysis. The structure to be accessed is named is ROTA. Elements from Groups 1, 3, 5, 6, 7 and 9 are to be processed. The von Mises check stress is 50.0 and the Tresca check stress is 75.0. The average stresses for all loadcases are to be processed, and principal stresses for user loadcases 1, 3, 7, 8, 9, 10, 11 and 14. The average stresses and principal stresses are to be printed for user loadcases 1 and 10. All processed stresses will be written to a FEMVIEW file called ROTA.FVI with a model name ROTOR.


PROJ ROTA

JOB POST

TITLE EXAMPLE ILLUSTRATING AXIS DATA

STRUCTURE ROTA

OPTIONS END

SAVE FEMS FILES CREATE ROTOR FILE ROTA.FVI

END

AXIS

GROU

1 3 5 -7 9 END

VONM

50.0

TRES

75.0

AVST



ALL

PRST

1 3 7 -11 14 END

PRIN

1 10 END

END

3.4. Example 4: Post Processing Component Results from Multi Level Axisymmetric Analysis

This example considers elements in component MLS1 which has been assembled into structure MLST. Elements in groups 1, 3 and 5 are selected. One section (numbered 19) is taken from ASAS group 1 on a plane defined by nodes 28 and 49 and passing through nodes 29, 30 and 48. Averaged stresses will be printed for loadcases 1, 4, 5, 6 and 7.

Next an extra group, number 15, is formed of user elements numbered 31 to 36, 40 and 62 to 70. This extra group has von Mises and Tresca check stress levels of 25.0 and 37.5 and the averaged stresses will be printed for loadcases 2, 3, 8, 9 and 10.


PROJECT MLPJ

JOB POST

TITLE AXIS DATA WITH EXTRA GROUP

STRUCTURE MLST

COMPONENT MLST MLLB MLS1

OPTIONS END

END

AXIS

GROU

1 3 5 END

SECT

1 19 END

19 28 29 30 48 49 END

AVST

1 4 5 -7 END

EXTRA

15 31 -36 40 62 -70 END

VONM

25.0

TRES

37.5

AVST

2 3 8 -10 END

END



3.5. Example 5: Loadcase Combinations

This example considers elements in component MLS1 which has been assembled into structure MLST. The elements considered do not all have consistently oriented local axes and hence the OUTP and OUTR commands are given to define new output axis systems. Firstly a cartesian output axis system is defined using the OUTP command. This will then be used for elements in groups 1 3 and 5. A new radial output system is then defined using the OUTR command. This will then be used for the elements which are defined as a new group using the EXTR command and also for elements in groups 2 and 4. The new group will be group 16 consisting of elements 75 to 80 and 82. In all these groups user elements numbered 37 to 39, 43 to 47 and 51 to 53 are to be omitted from the calculations. Mid-plane and surface check stresses of 50.0 and 75.0 are set and the averaged stresses and principal stresses will be printed for loadcases 1, 4, 5, 6 and 7.

Next the output axis system is set back to consistent axes using the CONS command, and a new extra group, number 15, is formed of user elements numbered 31 -36, 40 and 62 -70. This extra group has mid-plane and surface check stress levels of 25.0 and 37.5. Two new loadcases are formed, 101 by adding together cases 1 and 4 and factoring by 1.05 and 102 by adding case 4 factored by 1.25 and case 6 factored by -0.5. The averaged stresses will be printed for loadcases 2, 3, 8, 9, 10 and 101. Note, the FACT command is used to reset the factor to 1.0 before printing.


PROJECT MLPJ

JOB POST

TITLE SHELL DATA WITH EXTRA GROUPS AND OUTPUT COMMANDS

STRUCTURE MLST

COMPONENT MLST MLLB MLS1

OPTIONS END

END

SHELL

OUTP

0.5 0.8660 0.0 25.0 0.0 0.0

GROU

1 3 5 END

OUTR

1.0 0.0 10.0 1.0 0.0 2.0

EXTRA

16 75 -80 82 END

GROU

2 4 END

SKIP

37 -39 43 -47 51 -53 END

FECM

50.0

FECS

75.0



AVST

1 4 5 -7 END

PRST

1 4 5 -7 END

CONS

EXTRA

15 31 -36 40 62 -70 END

FECM

25.0

FECS

37.5

NEWC

101 102 END

101 COMBINATION OF CASE 1 AND 4

102 COMBINATION OF CASE 4 AND 6

FACT

1.05

ADDC

101 1 4 END

ADDF

102 4 1.25 6 -0.5 END

FACT

1.0

AVST

2 3 8 -10 101 END

END

3.6. Example 6: Post Processing Harmonic Analyses

This data file runs POST for a HARMonic analysis. One new loadcase is generated which is just case 1, with an antisymmetric expansion about θ=0, of STRUCTURE WQH1. Stress output is generated for angle θ=20° only. Note, this will have loadcase 5020 on its printout.


PROJ WQX8

JOB POST

FILE WHHH

TITLE SIMPLE HARMONIC EXAMPLE

STRUCTURE WQH1

NEWSTRUCTURE WHHH

OPTIONS END

SAVE FEMS FILES

END



HARM

ANGL

20.0 END

COMB 1

SELE 5 LOADCASE 1 of WQH1

STRUCTURE WQH1

SIN

1 1.0

END

END

3.7. Example 7: Harmonic Combinations

This example produces two new loadcases (5, 6) from the stress results from structures WQHO, WQH1, WQH2, WQH3, and WQH4. Output is requested at angles 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 and 120 degrees. The output will refer to loadcases 5020, 5030, 5040 ..... 5110, 5120, 6020, 6030 .... 6110, 6120. Each combined loadcase accesses each structure and more than one loadcase from each original structure. As no PRST or AVST command appears, the output will include both principal and average stress results.


PROJ WQX8

JOB POST

FILE WHHH

TITLE FULL HARMONIC EXAMPLE

STRUCTURE WQHO

NEWSTRUCTURE WHHH

OPTIONS END

END

HARM

ANGL

20.0 30.0 40.0 50.0

60.0 70.0 80.0 90.0

100.0 110.0 120.0 END

COMB 2

SELE 5 1ST COMBINED LOADCASE

COS

2 1.0 3 1.0

STRUCTURE WQH1

COS

2 1.0 3 1.0

STRUCTURE WQH2

COS

2 1.0 3 1.0



STRUCTURE WQH3

COS

2 1.0 3 1.0

STRUCTURE WQH4

COS

2 1.0 3 1.0 END

SELE 6 2ND COMBINED LOADCASE

STRUCTURE WQHO

COS

1 1.0 2 1.0 3 3.0

STRUCTURE WQH1

COS

1 1.0 2 2.0 3 3.0

STRUCTURE WQH2

COS

1 1.0 2 2.0 3 3.0

STRUCTURE WQH3

COS 1 1.0 2 2.0 3 3.0

STRUCTURE WQH4

COS 1 1.0 2 2.0 3 3.0 END

END

END

3.8. Example 8: Post Processing Shell Compatible Beams

This example shows the data for running POST after an ASAS analysis which includes shell BEAM elements (TCBM or GCB3). It is assumed that all the beam elements in groups 1 2 and 3 have consistent local axis and that the user wishes to have the moments/forces reported in the element local axis.

Groups 4, 5 and 6 are to be reported in a new output axis system defined by the preceding OUTB command.

Three new loadcases have been formed. The first two have the same combination factors, one representing the positive (or maximum) limit stress value, the second the negative (or minimum) limit stress value. The third new loadcase takes the first two new cases and finds the absolute envelope, giving the overall worst absolute values.

Finally the forces/moments for all loadcases are to be printed out. Since a SAVE FEMS FILES command is present in the preliminary deck, all results will be saved for plotting in FEMVIEW. Since APPEND is specified, no model data (coordinates and element definitions) will be added to the plot file. If the plot file STIFFNER.FVI already exists the results will be appended to it. If not then the new STIFFNER.FVI file can be read into FEMVIEW if the model data already exists for model STIFNR.

SYSTEM DATA AREA 35000 PROJECT STIF JOB POST



TITLE EXAMPLE ILLUSTRATING SBEAM DATA STRUCTURE STIF OPTIONS END SAVE FEMS FILES APPEND STIFNR FILE STIFFNER.FVI END SBEAM CONS GROU 1 2 3 END OUTB 0.0 1.0 0.0 0.0 0.0 1.0 GROU 4 5 6 END NEWC 101 102 103 END 101 MAXIMUM LIMIT STRESS CASE 102 MAXIMUM LIMIT STRESS CASE 103 MAXIMUM ABSOLUTE ENVELOPE OF CASES 101 & 102 ADDF MXLS 101 1 1.3 1.0 2 1.0 1.0 3 1.3 -1.3 END ADDF MNLS 102 1 1.3 1.0 2 1.0 1.0 3 1.3 -1.3 END ADDC MXAE 103 102 101 END AVST ALL END

3.9. Example 9: Post Processing Laminated Shells

This example shows the data deck for calculating laminate layer stresses with POST following an ASAS analysis using laminated shells. For the ASAS groups 1 and 2 only the stresses of layers 1, 2, 5 and 6 are to be reported (these may be the top and bottom two layers of the composite section). In addition a new group (group 11) has been formed from elements 1 to 20 for which all the layers are to be processed. Finally a new loadcase has been formed consisting of the summation of ASAS loadcases 1 and 2.


PROJECT COMP

JOB POST

TITLE EXAMPLE ILLUSTRATING LAMI DATA

OPTION GOON END

SAVE FEMS FILES

END

LAMI

LAYE



1 2 5 6 END

GROU

1 2 END

LAYE

ALL

EXTR

11 1 TO 20 END

NEWC

101 END

101 LOADCASE 1 + LOADCASE 2

ADDF

101 1 1.0 2 1.0 END

END

Output POST User Manual


4. Output

Three forms of output are available from POST, the printed stress output, a backing file that may be used for further post-processing, and the sequential files required as input for a variety of proprietary plotting packages.

4.1. Printed Output

The printed output consists of the data check, followed by the stress output, listed group by group. Within each group the average surface stresses and also the principal stresses are listed if requested for each loadcase in turn. The exact form of the output will depend on the type of data being analysed, and is discussed in further detail in the subsequent sections of this manual.

4.1.1. SHELL Data

The average surface stresses are printed for the top, bottom and mid-surfaces of the element (as defined in Section 2.1). These stresses are given in terms of the output axis system, as defined by the OUTP or OUTR commands, or the local element axis system in the case of consistent axes. This set of output also includes the number of elements contributing to the nodal average and the maximum variation in stress at the particular node. The variation shows the user the level of the stress difference between adjacent elements at the same node and also indicates on the accuracy of the overall stresses. In the cases of high variation compared to averaged stresses, the accuracy of the model should be checked.

The in-plane principal stresses P1 and P2 together with the principal stress difference (P1 and P2) are printed for each of the three surfaces. Two check stresses are also printed at the head of each page of principal stress output. These are the mid-plane (membrane) and the surface (membrane plus bending) stress allowables FECM and FECS respectively, and are defined by the user for the particular loadcase. At each node the ‘effective’ stress on each of the three surfaces is checked against the allowable stress - that is the top and bottom surface effective stresses are compared with FECS and the mid-surface effective stress is compared with FECM. The maximum of the surface stress ratios and the mid-plane stress ratio are printed only for values greater than unity under columns headed FECS and FECM respectively.

In the above, the effective stress is the Tresca stress σT where:

σT = max. absolute of P1, P2, (P1 - P2)

Asterisks are used throughout the printout to highlight maximum values of P1, P2, (P1, - P2) and the stress ratio.

The backing file, when saved, contains the information required to plot the stress contours for both principal stresses and averaged nodal stresses for each loadcase of every group considered in the POST run.

If the user has specified some of the options (BANM, FANM, WOOD) which produce SHELL output with forces and/or moments instead of the surface stresses the same procedures are followed as described above. The



principal and average values will, however, relate to the net section forces and moments rather than to individual surface stresses. If the SHRS command is used, only the out-of-plane shear forces are reported.

4.1.2. LAMI Data

The direct stresses in the fibre direction and to the normal fibre direction and the inshear stresses are presented for each of the layers requested at each node on a group basis.

4.1.3. Shell BEAM Data

The results for shell beams are presented as forces and moments in the output axis system defined by the OUTB command, or the local element axis in the case of the CONS command. In addition to the forces and moments, a variation value is printed giving an indication of the force/moment variation at a node common to two or more elements.

4.1.4. BRICK, AXIS and HARM Data

The average nodal stress output gives the direct stress in the three global directions and also the three shear stresses in these directions. The von Mises stress is also calculated and listed for each node. The user defined allowable stress is listed at the top of each page of output; where it is exceeded the ratio of the von Mises stress to the allowable is printed in the ‘EXCESS’ column.

The principal stress output gives the three principal stresses at each node and also the sum of the principal stresses and their direction cosines or principal angle. (For AXIS data, the hoop stress σHH is a principal stress). The von Mises and Tresca stresses are also printed for each node. The Tresca stress is checked against the user defined allowable which is printed at the top of the page. When the allowable is exceeded the ratio of the Tresca stress to the allowable is printed in the ‘EXCESS’ column.

4.2. Backing Files

The backing file, or intermediate file, is used within POST to temporarily save data that will be written to a plot file or used in loadcase combination/enveloping. It contains information on both the form of the model (nodes, elements groups etc) and calculated stress results. For this reason it is a useful file if further processing of results is to be undertaken. If it is required then it may be saved using SAVE INTE FILE in the preliminary deck. The saved file will be called XXXX12 where XXXX is the 4 character structure name.

If a subsequent run of POST is made on the same structure and an intermediate file is found to exist then post will try to append data from the current run. Before it can do this it has to check for any inconsistencies on the



intermediate file with the current run. Such inconsistencies include different element groupings and conflicting loadcase numbering. In this event the current run would be terminated.

In some cases it is desirable to overwrite an existing intermediate file rather than append to it. This can only be achieved by using SAVE NEWP FILES in the preliminary data. It is not recommended to delete the old intermediate file, since its existence is determined from the project index file not its physical existence, hence deleting the 12 file will require you to re-run in order to correct the project file referencing.

If the RESU command is specified in the preliminary data, the results from POST will be saved to a file called XXXX45.

4.3. Plotting Program Input

This section describes the contents of the file(s) produced by POST for input to different plotting packages.

4.3.1. FEMVIEW Input

FEMVIEW uses a formatted file that is created when the SAVE FEMS FILES command is present in the preliminary data. By default the file will be saved as nnnnFS where nnnn is the four character backing file name. This may be overridden by specifying a file name explicitly on the SAVE FEMS FILES command (Appendix A-).

The exact format of the FEMVIEW file is described in detail in the FEMGEN/FEMVIEW user documentation (Appendix B-). This section will only give a brief overview of the file format, sufficient for the user to be able to understand the data within it. The data is divided into a series of ‘data decks’, each of which begins with a header line and a terminator line (consisting of -3 only). The first number on the header line defines the type of data that follows. The following are used in the POST created file:

1 - user header defining model name (no corresponding terminator line)

2 - nodal coordinates

3 - element connectivity

100 - results data

9999 - end of data file

If APPEND is defined in the SAVE FEMS command then data types 2 and 3 will not be written. These may already be in the file to which the data is being appended. The data type number is followed by either C (for create, if model data present) or A (for append, no model data present). On the user header line this is followed by the model name to be used by FEMVIEW. By default this is the four character backing file name, but may be defined explicitly on the SAVE FEMS FILES command. Note that if EXTR groups are created in POST, then the CREATE Command should be used on the SAVE FEMS line.

The nodal coordinate data and element connectivity are self explanatory except that on the elements the group number is output in place of the material number required by FEMVIEW. The reason for this is that POST



averages stresses on a group basis and so a node may have different stresses for each of the groups, which can only be accommodated by FEMVIEW by material based nodal results. This has repercussions throughout the ASAS suite of programs, the material and group numbers being swapped over to maintain compatibility with POST.

The results data header is followed by a loadcase name, made up of ‘L’ followed by the loadcase number, and the loadcase title truncated to 20 characters. This is followed by further headers that give the name of the results set, the type of results, and the names of each component of the results. Two basic results types are used, material based nodal results and element nodal results, the latter being used only for the SBEAM results. Where the results are in the global axes system they are written in a matrix form allowing FEMVIEW to calculate principal stresses and present vector diagrams of principal stresses. For multi-surface results (e.g. shell/plate stresses), the results are written from bottom surface to top surface. Thus, surface 1 is the bottom surface.

4.3.2. PATRAN® Input

PATRAN® displays any defined stresses at each node. In POST stresses are calculated on an element group basis and, therefore, any node lying on a boundary between two or more element groups can have more than one set of stresses. To overcome this problem each element group is output to a separate file generated by POST. Two files per group are generated, the first containing average stresses, the second containing principal stresses.

SBEAM result cannot be plotted in PATRAN®.

4.3.2.1. The PATRAN® Results File

Each PATRAN® Results file generated by POST is assigned a different file name. This file name is made up from the first 4 characters given on the line following the NAME command. Appended to this is a 4 digit integer starting at 0001 and increment by 1 for each file output. Finally, the 4 characters .NOD are added to indicate that the values are nodal stresses.

The type of stress contained in any file, average or principal, is indicated in the title record on the file. This title is also printed in the POST output together with the corresponding file name.

The structure of the PATRAN® input file depends upon the stress output requested. The file is written as binary or formatted depending on the save option PATN or PTNC.

Record 1 85 Words for non-lamina 1-80 Title (First byte of each word only - A1 format) stresses 81 No. of nodes in the group (NNOG) 82-84 Dummy 85 No. of stresses on each record (NST)

Record 1 85 Words for lamina 1-7 ‘ GROUP ’



stresses 8-12 Group number 13-23 ‘ LOAD CASE ’ 24-28 Loadcase number 29-48 ‘ LAMINA STRESS ’ 49-53 No. of layers 54-80 Dummy 81 No. of nodes in the group (NNOG) 82-84 Dummy 85 No. of stresses on each record (NST=3 x No. of layers)

Record 2 80 Words. Subtitle. Contains all blanks Record 3 80 Words. Subtitle. Contains all blanks

Record 4 NST+1 Words 1 Node number . 2-(NST+1) The stresses for that node . Record NNOG+3



4.3.2.2. PATRAN® Results File for each Analysis Type

Each type of analysis processed by POST will write a different set of nodal stresses to the PATRAN® results file. The correspondence between analysis type and the stress written to file is shown in Tables 4.3 and 4.4.

Element No. of Stresses

Stresses Surface

xx yy zz xy yz xz

AXIS 4 σRR σHH σZZ σRZ

HARMONIC 6 σRR σHH σZZ σRZ σZH σRH

BRICK 6 σxx σyy σzz σxy σyz σzx

SHELL 9 σxx σyy σxy T

σxx σyy σxy M

σxx σyy σxy B

PLATE 9 σxx σyy σxy T

0 0 0

σxx σyy σxy B

MEMBRANE 9 0 0 0

σxx σyy σxy M

0 0 0

LAMI 3*NLAY σxx σyy σxy 1 to

NLAY

Notes

T M B refer to top, middle and bottom surfaces respectively

NLAY number of layers in laminate

Table 4.3 Average Stresses Written to Patran® Results File



Element No. of Stresses

Stresses Surface P1

L2 P2 M2

P3 N2

L1 L3

M1 M3

N1 N3

AXIS 7 P1 P2 Ph L1 M1

L2 M2

HARMONIC 12 P1 P2 P3 L1 M1 N1

L2 M2 N2 L3 M3 N3

BRICK 12 P1 P2 P3 L1 M1 N1

L2 M2 N2 L3 M3 N3

SHELL 12 P1 P2 (P1-P2) T

P1 P2 (P1-P2) M

P1 P2 (P1-P2) B

Tresca(T) Tresca(M) Tresca(B)

PLATE 12 P1 P2 (P1-P2) T

0 0 0

P1 P2 (P1-P2) B

Tresca(T) 0 Tresca(B)

MEMBRANE 12 0 0 0

P1 P2 (P1-P2) M

0 0 0

0 Tresca(M) 0

Table 4.4 Principal Stresses Written to Patran® Results File

Note

P1 P2 P3 are principal stresses Ph hoop stress L1 M1 N1 are direction cosines for P1 L2 M2 N2 are direction cosines for P2 L3 M3 N3 are direction cosines for P3 T M B refer to top, middle and bottom surfaces respectively

Appendix A POST User Manual

Page A-1 Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Appendix A - Preliminary Data Block for POST

A.1 Introduction

The preliminary data is the first block of the LOCO data. It defines the memory size to be used, the project name, structure and component names, file names and options to be used. It also defines which files are to be saved for further processing.

The preliminary data must commence with the SYSTEM command and terminate with END. Within these bounds the other commands may be given in any order. It is suggested, however, that the order given above is adopted.

SYSTEM

pnamePROJECT

fnameFILES

TEXT

STRUCTURE

DATA AREA memory

POSTJOB

titleTITLE

text

sname

COMPONENT sname tree

NEWSTRUCTURE nsname

OPTIONS option

UNITS unitm

SAVE set (FILES)

END

resultnm

RESU



A.2 SYSTEM Command

To define the amount of memory used for data by this run. Optional.

Parameters

SYSTEM : keyword

DATA AREA : keyword

memory : amount of memory (in 4 byte words) to be used by this run. Typical values are between 30000 and 1000000. If the SYSTEM command is omitted, a default value of 1000000 is used. (Integer)

Examples


A.3 PROJECT Command

To define the project name for the current run. Optional.

Parameters

PROJECT : keyword

pname : project name for current run. (Alphanumeric, 4 characters, first character must be alphabetic)

Note

All runs with the same project name access the same data base. A project data base consists of one project file (with a file name consisting of the 4 characters of pname with the number 10 appended) which acts as an index to other files created under this project, together with those other files.

Example

PROJECT HIJK

SYSTEM DATA AREA memory

pname PROJECT



A.4 JOB Command

To define the type of analysis being performed. Compulsory.

Parameters

JOB : keyword.

POST : keyword.

Example

JOB POST

A.5 FILES Command

To define the prefix name for the backing files created in this run. Optional.

Parameters

FILES : keyword.

fname : prefix name for any backing files created by this run. (Alphanumeric, 4 characters, first character must be alphabetic)

Note

fname is used as a prefix for all files created during the current run. The four characters are appended with two digits in the range 12 to 35 to create each individual file.

Example

FILES BILL

A.6 TITLE Command

To define a title for this run. Recommended.

POST JOB

fname FILES



Parameters

TITLE : keyword

title : this line of text will be printed out at the top of each page of ASAS output. (Alphanumeric, up to 74 characters)

Example

TITLE THIS IS AN EXAMPLE OF A TITLE LINE

A.7 TEXT Command

To define a line of text to be printed once only at the beginning of the output. Several TEXT lines may be defined to give a fuller description of the current analysis on the printed output.

Parameters

TEXT : keyword

text : this line of text will be printed once, at the beginning of the output. (Alphanumeric, up to 75 characters)

Example

TEXT THIS EXAMPLE OF THE TEXT

TEXT COMMAND IS SPREAD

TEXT OVER THREE LINES

A.8 STRUCTURE Command

To define the name of an existing structure within the current project that is to be processed in this run.

title TITLE

TEXT text



Parameters

STRUCTURE : keyword

sname : structure name identifying which existing structure is to be accessed from the project defined on the PROJECT command. (Alphanumeric, 4 characters, the first character must be alphabetic)

Note

For harmonic combinations the loadcase information to be processed may be drawn from more than one structure and this is achieved by respecifying a STRUCTURE command within the COMBination data (see Section 2.11.3). The structure defined in the preliminary data is adopted until a new STRUCTURE command is supplied.

For harmonic re-run, the structure name should identify the files that contain the combined loadcase information.

See also A.9 COMPONENT command.

Example

STRUCTURE SHIP

A.9 COMPONENT Command

For substructure analyses, this command defines the recovered component being processed in the current run.

Parameters

COMPONENT : keyword

sname : structure name as defined on the previous STRUCTURE command. (Alphanumeric, 4

characters, the first character must be alphabetic)

tree : this is the path down the component tree from the given structure in sname to the

component which is being used for POST post-processing.

STRUCTURE sname

COMPONENT sname tree



Notes

(i) If the user is processing the global structure run in a substructure analysis, use only the STRUCTURE command (A.8).

(ii) For harmonic combinations the loadcase information to be processed may be drawn from more than one structure and this is achieved by respecifying a COMPONENT command within the COMBination data (see Section 2.11.3). The structure defined in the preliminary data is adopted until a new COMPONENT command is supplied.

Example

To process the second level component, CMP2, which is part of assembled component CMP1, which is part of structure STRU.

COMPONENT STRU CMP1 CMP2

A.10 NEWSTRUCTURE Command

This command is only needed for HARM data type and is used to identify the results being created. However, in this case the new structure name will not be permanently saved in the project file if no SAVE or RESU command is specified. In this case, the same new structure name may be used repeatedly within one project.

Parameters

NEWSTRUCTURE : keyword

nsname : new structure name. This must be unique within the current project (but see note

above). (Alphanumeric, 4 characters, the first character must be alphabetic)

Example

NEWSTRUCTURE NSTR

Notes

NEWSTRUCTURE command is not needed in a harmonic re-run where the loadcase combination data are omitted.

A.11 OPTIONS Command

To define the control options for this run. Optional.

NEWSTRUCTURE nsname



Parameters

OPTIONS : keyword

option : 4 character option name, or list of option names. See table below for details of the options available

Note

The following options are available in POST:

Option Name Application

DATA Stop after checking the data and do not process the stresses.

GOON Proceed even after printed WARNINGS. This option allows the program to continue despite doubtful data. It should be used after a run in which the WARNINGS have been noted and rejected.

NOBL Do not print the POST title page.

CCGO Proceed with stress averaging even after thickness and/or offset discontinuities are encountered within an element group, see Section 1.4.

GLST Print shell element stresses to FEMVIEW file in global stress format. This allows the FEMVIEW stress calculation facilities to be used. Note: This does not convert the FEMVIEW stresses into the global system and so vector plots may be misleading.

UPLT Write any unity stress values computed in the current run to the plot file. Unity stress values are computed when check stress values are defined, see Section 2.10.

OAIS The material axis definition for anisotropic shells changed with the issue of POST version H11.3. This option allows the user to continue to employ the old material axis definition if needed. It is required if and only if the structural analysis was undertaken using a version of ASAS prior to H11.3, or the complementary OAIS option has been used in the ASAS run.

Example

OPTIONS DATA GOON END

OPTIONS option



A.12 SAVE Command

To define the plot file which is to be saved for subsequent display by the relevant plotting program, or to save the intermediate file

Parameters

SAVE : keyword

FEMS : keyword to save the FEMVIEW plot file

prog : mnemonic to define the plotting program name. Valid names are:

PATN - PATRAN nodal results file, binary

PTNC - PATRAN nodal results file, formatted

(FILES) : keyword

CREATE : keyword to signify model data is to be included (default)

APPEND : keyword to signify no model data to be included

model : model name to be used by FEMVIEW

FILE : keyword to indicate filename follows

filename : name of FEMVIEW file to be created

INTE : keyword to save the intermediate file and append data to it if necessary

NEWP : keyword to save the intermediate file and overwrite existing file if necessary

Notes

1. The plot files are mutually exclusive and only one may be specified within any POST analysis.

2. CREATE/APPEND and following data is only valid for prog = FEMS

SAVE prog (FILES)

SAVE INTE (FILES)

CREATE

APPEND

(model) (FILE) (filename)SAVE FEMS (FILES)

SAVE NEWP (FILES)



3. FILE may only be omitted if model is specified

4. Note that if EXTR groups are created in POST, then the CREATE Command should be used on the SAVE FEMS line.

Example

SAVE PATN FILE

A.13 RESU Command

To specify saving of results. The results processed by POST will be added to the database.

Parameters

RESU : keyword

Example

RESU

A.14 UNITS Command (not valid for fixed format ASAS data)

If UNITS have been employed in the ASAS analysis it is possible to specify modified units for the POST results. The default units will be those utilised in the original analysis and if this is satisfactory the UNITS command may be omitted.

Parameters

UNITS : keyword

STRE : keyword

unitm : name of unit to be utilised (see Section 2.2)

RESU

UNITS unitmSTRE



Notes

1. If the results from more than one structure or component are being combined in a HARM type analysis, the analysis units must be identical

2. Only those terms which are required to be modified need to be specified, undefined terms will default to those supplied on the global units definition.

3. For a full list of valid unit names see Section 5 of the ASAS User Manual.

Example

The global units defined in the ASAS run are N and M. If the units are redefined in the POST runs as follows:

UNITS STRE MM

the stress results will be reported in N/mm2.

A.15 END Command

To terminate the preliminary data. Compulsory.

Parameters

END : compulsory keyword

END

Appendix B POST User Manual

Page B-1 Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Appendix B - - Running Instructions for POST

B.1 ASAS Files Required by POST

POST operates on the files produced by the preceding ASAS or LOCO analysis. The appropriate files must physically be present in the user’s disk space for the program to run successfully. In all cases the Project File must exist which contains information about all other files in the current set of analyses. The name of this file is derived from the four character Project name defined on all PROJECT commands in the set. For example, if the project name is PRDH, then the Project File will be PRDH10.

The appropriate results for running POST will be saved when a ‘SAVE LOCO FILES’ or a ’SAVE STRESS FILES’ command appears in the preliminary data of the ASAS or LOCO data. The file name will be derived from appending 35 to the four character name on the FILES command of the ASAS or LOCO preliminary data. This name will also appear on the STRUCTURE command of the current preliminary deck (name2 in Appendix A-). For example, if this name had been RNDH, then the backing file containing stresses (and displacements) would be RNDH35. For a POST run on a substructured analysis the file name for the results is derived from the second four character name on the JOB command of the relevant stress recovery run. If this name has been SRGP then the file would be SRGP35.

For a harmonic run accessing several structures the files required by POST are precisely analogous to those required by LOCO.

B.2 Running Instructions for POST

See the appendices in the ASAS User Manual for details on how to run any of the programs in the ASAS suite.

Appendix B POST User Manual

Page B-2 Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Appendix C POST User Manual

Page C-1 Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Appendix C - - Equations used for Stress Calculations

The equations used for stress calculations are based on the averaged nodal stresses. These will be orientated according to the ASAS local element axes system unless an output axes system has been specified to reorientate the stresses.

C.1 Notation

Stresses and Moments

Principal Stresses

Equivalent Stresses

Wood -Armer Values

Reinforcement Values

σσσ zzyyxx , , σσσ zxyzxy , ,

σσσ zzhhrr , ,

σσσ zrhzrh , ,

M ,M ,M zzyyxx

M ,M ,M zxyzxy

Direct stress in X, Y and Z directions

Shear stresses in XY, YZ and ZX planes

Direct stresses in R, H and Z directions

Shear stresses in RH, HZ, ZR planes

Moments in X, Y, and Z directions

Torques in XY, YZ and ZX planes

Principal stresses (P1 is the highest principal stress value)

Principal stress angle (measured from the output X axes to the absolute

maximum principal stress - not necessarily P1)

P ,P ,P 321 θ

von-Mises equivalent stress

Tresca equivalent stress

σ V

σ T

Positive Wood-Armer moment in X and Y directions

Negative Wood-Armer moment in X and Y directions

Skew angle between reinforcement directions

M ,M PyPx

M ,M NyNx α

Reinforcement cover depths (top and bottom)

Thickness of slab

Equivalent in-plane loads in idealized layers

Loads to be resisted by reinforcing in X and Y directions

Design stress for reinforcing

Area of reinforcement required in X and Y directions

Compressive force in concrete

C,C BT h

N ,N ,N xyyx

N ,N *y

*x

F RA

A ,A yx f c



C.2 Stress Formulae

Principal Stresses: 2D Stress Field:

3D Stress Field

Von-Mises Equivalent Stress:

Tresca Equivalent Stress:

( )σ+

σσσσ 2xy

yyxx2

yyxx1 4

-+

2 +

= P

( )σ+

σσσσ 2xy

yyxx2

yyxx2 4

--

2 +

= P

σσ

σθ

yyxx

xy-1

-2

2

tan=

( ) ( ) ( )P-PP+P-PP+P-PP= 133322211Vσ

( ) ( ) ( )( ) σσσσσσσσσσ 2zx

2yz

2xyxxzz

2zzyy

2yyxx

2V +3+3+3-+-+-2

1=

( ) ( ) ( )( ) σσσσσσσσσσ 2zr

2hz

2rhrrzz

2zzhh

2hhrr

2V +3+3+3-+-+-2

1=

σσσσσσ 3+-+= 2xyyyxx

2yy

2xxV

- Solids

- Solids

- Shells

- Axi-symmetrics

P-Por P-Por P-P of valuemaximum = 133221Tσ

P-Por Por P of valuemaximum = 2121Tσ

- Solids

- Shells (P3=0)

:equation theof roots by thegiven are P & P,P 321

( ) ( )P---+++P++-P 2zx

2yz

2xyxxzzzzyyyyxx

2zzyyxx

3 σσσσσσσσσσσσ

( ) 0=---2+- 2xyzz

2zxyy

2yzxxzxyzxyzzyyxx σσσσσσσσσσσσ



C.3 Wood-Armer Calculations

C.3.1 Wood-Armer Moments - Orthogonal Reinforcing

Positive Moments:

Negative Moments:

M + M = M xyxxPx

M + M = M xyyyPy

: then 0 < M If Px

MM + M = M

xx

xy2

yyPy

0 = M and Px

0 = M then 0 < M If PyPy

or : then 0 < M If Py

MM + M = M

yy

xy2

xxPx

0 = M and Py

0 = M then 0 < M If PxPx

M - M = M xyxxNx

M - M = M xyyyNy

MM - M = M

xx

xy2

yyNy

0 = M and Nx

0 = M then 0 > M If NyNy

or : then 0 > M If Ny

MM - M = M

yy

xy2

xxNx

0 = M and Ny

0= then0 > M If Nx

etc. Mfor ngsubstitutiby given are sStresse Armer- Wood:Note PxPxσ′′

: then 0 > M If Nx



C.3.2 Wood-Armer Moments - Skewed Reinforcing

Positive Moments:

Negative Moments:

Note: In the original Wood-Armer papers the equations were derived using a left handed axis system. Since ASAS uses a right handed system the above equations have been modified by reversing the direction of the reinforcing skew angle α.

C.4 Reinforcement Area Calculations

α

ααα

sincotM-M+cotM+cotM-2M=M

2yyxy2

yyxyxxPx

α

α

α sincotM-M+

sinM=M

2yyxy

2yy

Py

: then0<M If Px

0=MPx

( )

αα

α

α cotM+cotM-2M

cotM-M+Msin

1=M 2yyxyxx

yyxy2

yy2Py

: then0<M If Py 0=MPy

( )M

cotM-M+cotM+cotM-2M=Myy

yyxy2

2yyxyxxPx

ααα

α

ααα

sincotM-M-cotM+cotM-2M=M

2yyxy2

yyxyxxNx

α

α

α sincotM-M-

sinM=M

2yyxy

2yy

Ny

: then0>M If Nx 0=MNx

( )

αα

α

α cotM+cotM-2M

cotM-M-Msin

1=M 2yyxyxx

yyxy2

yy2Ny

: then0>M If Ny

0=MNy

( )M

cotM-M-cotM+cotM-2M=Myy

yyxy2

2yyxyxxNx

ααα



Reinforcement areas are calculated using the approach described by Clark using the equations by Nielson. The full equations are extensive and complex and so only a brief overview of the method employed is given below. Full details of the procedure may be found in the document ESR170490 - ASASPOST ‘Reinforcement Area Calculations’. The method assumes that the loading in a slab is carried as direct loading only in the layers of concrete at the top and bottom of the slab. The thicknesses of these layers are assumed to be twice the relevant reinforcement cover depth. The loading in the layers are calculated from the following equations:

Similar equations may be written for NyT, NyB, NxyT and NxyB equivalent forces. The actual load to be carried by the X and Y directional reinforcing is then given by:

It will be apparent that these are effectively the same as the Wood-Armer equations above and indeed the full set for skew reinforcement applies. Having established the load carried by the reinforcing (N*) the area of required area of reinforcing is given by:

N + N = N xyx*x

N + N = N xyy*y

: then 0 < N If *x

N

N + N = Nx

xy2

y*y

0 = N and *x

0 = N then 0 < N If *y

*y

or : then 0 < N If *y

N

N + N = N

y

xy2

x*x

0 = N and *y

0 = N then 0 < N If *x

*x

FN=ARA

*x

x FN

=ARA

*y

y



In addition the principal concrete compressive force fc is also calculated:

The above equations do not consider any compressive load capability of the reinforcement. For details of how this effect is included see the document ESR170490 described above.

N -2=f xyc

: then 0 < N If *x

NN + N =f

x

2xy

xc

0 = N and *x

: then0<N and 0 < N If *y

*x

or : then 0 < N If *y

N

N + N =f

y

2xy

yc

0 = N and *y

( )N+

4N-N+

2N+ N =f 2

xyyx

2yx

c

Appendix D POST User Manual

Page D-1 Contains proprietary and confidential information of ANSYS, Inc. and its subsidiaries and affiliates.

Appendix D - - Loadcase Combination Methods

The stress results for new loadcases in POST may be formed by factoring the stresses from the ASAS, or previously formed new POST loadcases and combining them according to one of the following methods:

SSUM - simple summation (default)

The factored stresses for each of the constituent loadcases are simply added together.

ABSS - absolute sum. The absolute values of the factored stresses for each of the constituent loadcases are added together. All resulting stresses will be positive.

SRSS - square root of the sum of the squares The factored stresses for each of the constituent loadcases are squared and then added together. The resulting stresses are then square rooted. The final stresses will be positive.

MXLS - maximum limit stress The stresses for each of the constituent loadcases are examined to see if they are positive (additive) or negative (relieving). If they are additive, then they are factored by the first factor, if relieving, then they are factored by the second. The resulting factored stresses are then combined using the SSUM method.

MNLS - minimum limit stress The stresses for each of the constituent loadcases are examined to see if they are negative (additive) or positive (relieving). If they are additive, then they are factored by the first factor, if relieving, then they are factored by the second. The resulting factored stresses are then combined using the SSUM method.

MAXE - maximum envelope The factored stresses for each of the constituent loadcases are considered in turn. The final loadcase consists of the highest (positive) stress values found in the constituent loadcases for each stress type.

MINE - minimum envelope The factored stresses for each of the constituent loadcases are considered in turn. The final loadcase consists of the lowest (negative) stress values found in the constituent loadcases for each stress type.

MXAE - maximum absolute envelope The absolute values of the factored stresses for each of the constituent loadcases are enveloped using the MAXE method.



WDME - Wood-Armer moment envelope The Wood-Armer moments are calculated from the factored stresses of each of the constituent loadcases. The resulting Wood-Armer moments are then enveloped.

REEN - Reinforcement Calculation Envelope The reinforcement requirements are calculated from the factored stresses of each of the constituent loadcases. The resulting reinforcement requirements are then enveloped.

For LAMI type data the loadcase combination is conducted on the composite section strains and not the individual layer stresses. The user should take this into account in the case of envelope and limit stress type combinations.

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