example2 two equal spans option1 final

8/13/2019 Example2 Two Equal Spans Option1 Final

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10/20/2011 Example2-Two-Equal-Spans-Option1-Final.ppt 1

Example 2 - Two equal spans

Details on following slides

Three foundation options:1. Fixed column bases

2. Pile/cap column bases

Bent cap

Circular bent columns

Abutment

Abutment

( two versions )


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deck

cap

BT-63

bearing

8"

63"

4"

48"

99"

4.0' 3 @ 7.0' 4.0'

29.0'

99"73" 71"75" 4"

4.0' = 48"

20.0' = 240"

73"75"

8" slab deck

Foundation:

Three options

Ground level

4"

railing

30" circular columns


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27.0'

6.0' 17.0'

5.0' 8.5'

1.0'

30"

Bent cap

Foundation

3.0'

4.0'

20.0'

Foundation

300 lb/ft (0.3 k/ft)

9"

18"

26.0' face-to-faceRailing


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Foundation Option 1: Bent columns on fixed supports

Columns assumed fixed at ground level

Bent cap

Bent column

Abutment

Abutment


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Each column supported by 9-pile group

Abutment

Abutment

Bent cap

Pile cap

Foundation Options 2 and 3: Bent columns on capped piles( Two versions )


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Example 2 Option 1:

Bent columns on fixed supports

Columns fixed at ground level

Bent cap

Bent column

Abutment

Abutment


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4.0'

20.0'

8" slab deck

Ground level

4"

railing

75" = 6.25'8.25'

30.25'22.0'

Top of column at mid-

height of bent cap

Fully-fixed foundation ("fixed

foundation springs")


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22.0'

Z = -30.25'

Z = -6.25'Z = -6.083'

Z = -6.25'Z = -6.083'

Z = -8.25'

Z = 0

X = 80.0'

Roller bearing

(X = 0, X = 160')

Pinned bearing

Abutment

Bent

X

Z


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Use Orbto open New File


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Start Bridge Wizarddefine Layout Line


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Bentat X = 80 will

be added later


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Default

materials


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Specify the Frame Sectionsused for the bent cap, bent columns, and girders

BT-63 Girders

48"

36"

Bent cap:same concrete as

used in deck30" concrete columns:

same concrete as used in deck

Option 1: Fixed column bases (shown)

Option 2: Pile/cap foundation


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Frame Sections: bent cap, bent columns, BT-63 girders


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Define and name the Bent Cap (only one)

Verify that section

dimensions are inches

See the next page for a hidden result of

selecting a Rectangularconcrete section


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Selecting a Rectangularconcrete FrameSectionautomatically adds the defaultreinforcing steel A615Gr60 (note default

sizes, etc.) to the list of Defined Materials

Confirm by going

back to Step 3.1 in

the Bridge Wizard


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1

2

3

Bent cap parameters and coordinates


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2

3 1

BT-63 girder and coordinates


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Deck Sections


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Bearings


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Keep default

d.o.f.s


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Abutments


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Bearing

Same abutment named Abutmentsused at both ends of the bridge

"fixed" abutment

support

Recall that the bearings are not part of

the abutment definitions

Define and name abutments


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Columns assumed fixed at ground level

Bent cap

Bent column

Bent

Bent

The bentconsists of the bent cap and the bent columns.

The fixity condition at the base of the column is part of the bent definition. In

Option 1 the columns are assumed fixed at the ground level, as shown below.

A different fixity definition will be required in Option 2 (pile/cap foundation)


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The deck sections in both spans are assumed continuous across the bent cap. This is

permitted only when both deck sections on either side of the bent are the same.

The deck sections are supported (at the undersides of the girders) on pinned bearings

that lie transversely along a single bearing line at the centerline of the cap.

Assumed bearing condition at the bent

Deck sections in both spans lie on same bearing line

Bent cap

30" concrete columns

Pinned bearing


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1

2

3

Cap membercoordinate system

X

YZ

1

2

3

The cap "fits" in bridge such that the

origin of the cap coordinate system is at

the left end of the cap, viewed in thestructure +X direction

Cap coordinate orientation


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3.0'

4.0'

20.0'

Fixed base

22.0'5.0' 8.5'

30"

Bent cap

Fixed base

5.0'

22.0'

1

2

View from X = 0


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Bent


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Define columns on

next screen


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Bent column positions, lengths and boundary conditions


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Line load named RIGHTRAIL:

Global coordinate system gravity load ( -Z direction )

Assume 300 lb/foot = 0.3 kip/foot

Assume applied 9" = 0.75 ft from right edge of bridge

Z

XY

Right edge of bridge

Left edge of bridge

"Left" and "right" bridge edges are as seen looking along the bridge

layout line, in the +X global coordinate direction

VIEW

Line load named LEFTRAIL

(same as RIGHTRAIL)

Railingssame as used in Example 1


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Railings as Line Loads


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Deck sections, bearings, abutments, and the bent will be assigned

to Bridge Object after the Bridge Object has been created

Create Bridge Object

One Bridge Object will include both spans

Startabutment

Endabutment

Layout line

Layout line length: 160 ft

Span from start

abutment to bent

80 ft

Span from bent to

end abutment

80 ft

Z

X

Bent

Bearing


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Define and name Bridge Object Bridge_object


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Default Bridg e Object Reference Linebased on

Layout Line defined in Bridge Wizard Step 2

Add New Bridg e Object opening screen


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Note that the "Bent" shown above is a generic term.

It is not the bent Bent_f ixed_basedefined in Bridge

Wizard Step 4.4. This specific bent will be assignedto the Bridge Object in Wizard Step 7.

Name the Bridge Object Bridge_object and then divide it into twosegments by inserting a bent at X = 80 ft.


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Redefined Bridg e Object Reference Line

This panel could be used to assign

deck sections, bearings, abutments

and bent properties.

However, the Bridge Wizardwillbe used in this example


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Ful l Span to End Bent

Start

abutment

End

abutment

Layout line

Z

X

Bent

Bearing

Ful l Span to End Bent Ful l Span to End Abutment

Assign Deck Sectionto Bridge Object

It only takes one Deck Sectionassignment for both spansbecause one Bridge Objectincludes both spans


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Assign Deck_Sectionto Bridge_Object

This is the only Bridge Objectthat has been defined. It is

used by default.


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Since there has been defined only one Deck Section, by default it

is assigned to both spans included in the Bridge Object


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Assign Bearings, Abutmentsand Bentto Bridge Object

Bridge Objectreferences

In the Bridge Object definition, Start Abutm ent,Bentand End Abutmentare the namesof

specific points along the layout line

Start

AbutmentEnd

Abutment

Bent

StartAbutment

EndAbutment

Bent


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Endbearingsand abutments

99"73" 71"75" 4"

4.0' = 48"

20.0' = 240"

73"75"

8" slab deck

Ground level

4"

railing

Roller bearing Roller bearingPinned bearing


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Details and dimensions assumed at the start(X = 0) and end(X = 160 ft) abutments

8" deck slab

rail

BT-63 girder

Z

X

Z = - 73"Z = - 75"

Action point of bearing(assumed at mid-depth

of bearing assembly)Top surface of abutment

substructure

Abutment "fixed"in all 6 d.o.f.)

Similar for X = 160 ft

73"75"

8" deck slab

rail

BT-63 girder

71"

Z

X

Roller bearing


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Do not "OK" yet

Assign both bearingand abutment substructureat Start Abu tment ( X = 0 )


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Repeat at End Abutment ( X = 160 ) - in this example, end abutments are the same


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Details and dimensions assumed at the bent

99"

73" 71"75"

4"

4.0' = 48"

rail

BT-72 girder

8" deck

Pinnedbearing

bent

capMid-depth of bent

cap (top of H-pile

embedment in

bent cap)

Action point of bearing(assumed at mid-depth

of bearing assembly)

Z = -73"

Z = -75"

Top surface

of bent cap


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Assign Bent andBearingto Bridge Object

Default


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Bent

location:

see

BridgeObject


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Bent

Star t A butment

X = 0

End Abutment

X = 160

Leftand RightRailingsassigned as Line Loads


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Assign Line Loads

Default

Click empty

Load Pattern

cell to begin


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U d t Li k d M d l t i t th i t j t


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Update Linked Modelto incorporate the assignments just

made to the Bridge Object Bridge_object:

Bearings, Abutments, Bent, Line Loads


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Note: Could also Update as Spine Model Using Frame Objectsfor most cases.

This step assembles the Bridge Structura l Modelused for analysis and design


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Resulting illustration of skeleton Area Object Model

Area Object Model

Still in Home Tabbecause Bridge

Wizardhas been used up to this point

Note: Could also create a bridge model by Updating


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Note: Could also create a bridge model by Updatingas Spine Model Using Frame Objectsfor most cases.

Spine Model Using Frame Objects

1. Open Bridg e Tab.

2. Turn off Autom at ic Update.3. Use manualUpdatefrom now on


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In the Br idgetab, manually Updateto get back to the

AreaObject Modelfor remainder of this Example

Default view: 3-d skeletal view


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Completed model - viewing options and attributes

Use this portion of Home tab to select and

control viewing the model

YX

Z

Default view: 3-d skeletal view


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Rubberband zoom

(select area to view)

Restore full view

Pan (move image

within view area)

Resume previous zoom

Zoom in , Zoom out

Rotate image (takes some

getting used to)


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Toggle between "perspective" and "flat"

views (doesn't always work!)

Refresh displayed image(useful at times)

Select 3-d or planar views for use in

drawing or editing components

Move through planes defined by grid

lines (during drawing or editing)


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3D and 2D rendering

views (not used for

drawing or editing

components)

Set Display Options (not all options

are available at the same time)


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Switch to Extrude Viewusing Display Options

Note:

Extru de Viewdisablessome of the other

Display Opt ions

3 d Extru de View


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3-d Extru de View

Mostly useful for viewing model to

verify that it "looks right"


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Change from 3-d Viewto plane view: XZ ( orXY,YZ)


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XZperspective view

Layout Lineorigin

X

Z


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Change from XZview toYZview

YZ perspective view


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YZperspective view

Layout Lineorigin

Z (up)

Y

View from X = 160 toward origin


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Turn off Perspect ivetoggle

"Flat" view

Perspective view

Toggle

Try other views and options


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y p

P f D d L d l i ( i d d k ili l d )


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Perform a Dead Loadanalysis (girders, deck, railing loads)

By default, girder and deck weights are assigned to DEAD load case. The railings were

specified as DEAD loads when the railing Line Loadswere assigned to the Bridge Object.

Select Load Case for which analysis is desired


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Opening

RunAnalysisoptions

Toggle

Act ion

between

Runand Do

Not Run

Select

Do Not Run

Select Load Casefor which analysis is desired


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Deflected shape: XZview - JointsON, PerspectiveOFF

Set 3D View:

XZ

Deflection reference line

Deflection at bent due to elastic shortening

of the bent columns and the piles

X (U1)

Z (U3)

U t i lt


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Use Displayto see various results

Draw deflected shape

Various deflections


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Various deflections

X (U1)

Z (U3)

U3 = -0.2947 in

U3 = -0.0263 in

Moment diagram


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Moment diagram

Draw moment diagram


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L it di l t di (i XZ l ) d t i id f b


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Longitudinal moment diagram (in XZ plane) drawn on tension side of member

Manual calculation: maximum negative DL moment


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Manual calculation: maximum negative DL moment

Dead loads (kips/foot):

Girders (BT-63): 4 * 0.743 k/ft = 2.97 k/ft

Deck: 29 ft * (8 in / 12 in/ft) * 0.15 k/ft3 = 2.90 k/ft 6.47 k/ft

Railings: 2 * 0.3 k/ft = 0.6 k/ft

L = 80 ft

w = 6.47 k/ft

Mneg(max) = (AISC Manual)

8

Lw 2

Mneg = = = 5176 ft-k ( 4949 by CSI Bridge)8

Lw 2

8

)ft80(ft/k47.6 2

Why the difference?

Reactions at base of bent column


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Reactions at base of bent column


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Rubberband Zoom

R = 369.5 kips

Vertical reaction on column in Y region


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Axial forces in columns


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Put pointer on joint:

Column force = -369.5 kips

R = 369.5 kips ( Slide 89 )


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Axial force diagram


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Rubberband Zoom

R = 369.5 kips

( Slide 89 )


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Save your CSI Bridge .bdb file in twoversions:

Save as: Example2-Two-Equal-Span-Option1.bdb

This is the option just completed in which the two columns are fixed at

their bases

Save as: Example2-Two-Equal-Span-Option2.bdb

This will be the starting point for the next option in which pile-cap/piles

foundation will be used

example2 two equal spans option1 final

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