en stas 10111-2-87 part 1_suprastructuri_beton

7/27/2019 En STAS 10111-2-87 PART 1_suprastructuri_beton

1/12

ICS 93.020

CONTENTS

1 GENERAL 22 ACTIONS 23 MATERIALS 33.1 Concrete 33.2 Reinforcements 43.3 Calculation characteristics of concrete and reinforcements to the fatigue limit state 64 CALCULATION TO ULTIMATE OVERTURNING STABILITY CONDITION 7

5 CALCULATION ON PLAIN CONCRETE ELEMENTS 85.1 Verifications required 95.2 Verification to ultimate strength condition 95.3 Verifications specific to ultimate normal use conditions 105.4 Verification for local concentrated forces 11 6 PROVISIONS REGARDING THE CALCULATION AND

COMPOSITION OF REINFORCED CONCRETE ELEMENTS 116.1 Verifications required 116.2 Verification to the strength limit state 126.3 Verification to the strength limit state, for bent sections 236.4 Verification to the fatigue limit state 316.5 Verification to the cracking limit state 336.6 Verification to the deformation limit state 356.7 Prescriptions regarding the composition of the concrete steel elements 377 PROVISIONS REGARDING THE CALCULATION AND COMPOSITION OF

THE ELEMENTS OF PRE-COMPRESSED CONCRETE 497.1 Necessary verifications 497.2 Determination of the unit stresses in concrete and pre-stressed reinforcement

under the actions of the loadings with exploitation values 497.3 Verification the limit state of strength in normal sections 517.4 Verification to limit state of resistance in cracked inclined sections 637.5 Verification to the fatigue limit state 657.6 Verification to the cracking limit state 657.7 Verification to the deformation limit state 737.8 Calculation of the transmission areas 737.9 Instructions regarding the production of pre-stressed concrete elements 74ANNEX A Concrete deformations in time produced by slow flow and contraction 78ANNEX B Effective length for the elements of simple concrete and reinforced concrete 82ANNEX C The calculation of reinforced concrete bearings for local compressions

(supporting bearings, berth bearings of pre-stressed reinforcement, pendulums etc.) 84ANNEX D The active width of the plate for beams or cased beams 99ANNEX E Calculation at stage II, of the unit stresses in concrete

and reinforcement for the reinforced concrete elements 102ANNEX F Prestressed concrete specific terminology 110ANNEX G Computations of stress losses in pretensioned reinforcement 112ANNEX H Main characteristics of precompression methods with pretensioned reinforcement 116ANNEX I Anchorage and transmission length for preextended reinforcements 121

ASOCIAIA DE STANDARDIZARE DIN ROMNIA (ASRO),Adresa po tal: str. Mendeleev 21-25, 70168, Bucure ti 1, Direc ia General : Tel.: +40 1 211.32.96; Fax: +40 1 210.08.33,

Direc ia Standardizare: Tel. : +40 1 310.43.08; +40 1 310.43.09, Fax: +40 1 315.58.70,Direc ia Publica ii: Serv. Vnz ri/Abonamente: Tel: +40 1 212.77.25, +40 1 212.79.20, +40 1 212.77.23, +40 1 312.94.88 ;

Fax : +40 1 210.25.14, +40 1 212.76.20

ASRO Entire or partial multiplication or use of this standard in any kind of publications and by any means (electronically, mechanically, photocopy, micromedia etc.) is strictly forbidden without a prior written consent of ASRO

R O M A N I A N S TA N D A R D STAS 10111/2-87 Classification index G 61 Replacing:

STAS 10111/2-77

Previous editions:1968

ROAD AND RAILWAY BRIDGESCONCRETE, REINFORCED CONCRETE AND PRESTRESSED CONCRETE

SUPRASTRUCTURES - DESIGN RULES Poduri de cale ferat i sosea - Suprastructuri din beton, beton armat si beton

precomprimat - Prescrip ii de proiectare Ponts de chemin de fer et routiers - Ponts de chemin de fer et routiers - Suprastructuresen beton, beton arm preconcentraint - Prescriptions pour letablissement des projects

Validation date:1987-12-01


2/12

STAS 10111/2-87 - 2 -

1 GENERAL

1.1 Scope

This standard deals with design rules for concrete, reinforced concrete and prestressed concrete structures of regular and narrow railway, road and mixed bridges; the provisions pertaining to calculation of concrete andreinforced concrete elements apply for infrastructures of bridges and for other art works on communication routes.

The provisions of this standard also apply for bridges for convoys of subways and trams, which are perceivedas railway bridges.

This standard deals with heavy aggregate (regular) concrete suprastructures and does not apply for lightaggregate concrete suprastructures.

1.2 The basic provisions for the calculation and composition of concrete, reinforced concrete and prestressedconcrete elements are in compliance with STAS 10102-75.

1.3 The calculations work with the following limit conditions:- ultimate limit states

- strength

- fatigue- stability of position (overturning, sliding)- ultimate conditions of normal use:

- cracking- strain

NOTE Road bridges and footbridges are to be calculated for fatigue only when in use for convoys on rails or if theyserve roads used by heavy convoys (equivalent of at least 80 % of the convoy used for calculation), with at least 2 x 10 6 cycles repeatability.

1.4 For concrete, reinforced concrete and prestressed concrete suprastructures of a special construction, the provisions of this standard may be adapted to the specific conditions with a technical economic justification andwith the approval of all relevant parts.

1.5 As for bridges placed in earthquake areas, they are to be calculated and composed in compliance with the provisions laid down in specific technical regulations as well.

2 ACTIONS

Action use values are established according to STAS 1489-78 and STAS 1545-80. Actions areclassified and categorised according to STAS 10101/OB-87.

3 MATERIALS3.1 Concrete

3.1.1 Classes of concrete are defined based on the concretes characteristic strength R ck , which is the compressionstrength at 28 days, established according to STAS 1275-81 on 141 mm-side cubes, under the value of which are seen5% of the results at most.

3.1.2 Minimal classes of concrete for strength elements of suprastructures are specified in table 1.

Table 1 No. Strength elements Minimal

class1 Massive plain and reinforced concrete elements Bc 10

- monolithic Bc 152 Tubular footbridges

- precast products Bc 20

- monolithic Bc 153 Plain and reinforced concrete suprastructures

- precast products Bc 20

4 Prestressed concrete suprastructures Bc 30


3/12

STAS 10111/2-87- 3 -

3.1.3 For cases in which a specific strength R bo is established through design to achieve at an age earlier than 28days (depending on the actual date of the construction loading, the prestressing date, the execution technology, the

properties of the cement used, etc.), the execution drafts should indicate the strength per cube (R bo) required at therespective age and the concrete classes; the transfer strength of the concrete should not be lower than the values givenin table 2.

Table 2

Concrete class Bc 25 Bc 30 Bc 35 Bc 40 Bc 50 Bc 60

R bo min, N/mm 25 28 32 35 48 58

3.1.4 The mortar strength when injecting the culverts of post-stretched reinforcements should be measured on70.7 mm-side cubes kept in wet air, and it should be minimally 30 N/mm 2 at 28 days. The minimal strength after 7 days should be 20 N/mm 2.

3.1.5 As for elements in aggressive environments, these should be made of concrete with special cements andaggregates, resistant to the action of aggressive agents, according to STAS 3349/1; 2-83, or measures should be takento protect the concrete (protection layers, surface treatments, etc.).

3.1.6 Characteristic strengths and basic values of calculation strengths of concrete are given in table 3.Calculation strengths should be established by multiplying the basic values in table 3 with coefficients of the

working conditions, taken as follows:- for plain concrete elements mbc = mbt = 0.9;- for concrete elements compressed eccentrically mbc = mbt according to table 4;

- for transfer calculation of single casting precast precompressed concrete products made in factories mbc = 1.1;- for bridges with difficult execution conditions or located in aggressive environments mbc = 0.9;- for constructions for which long term load represents at least 90 % of the total load mbc = 0.85; if long termload does not exceed 50 % of the total load, mbc = 1.00. For other variations, the coefficient of workingconditions should be established by linear interpolation between values 1.00 and 0.85. If calculation convoysintervene with a frequency higher than 50 % in the traffic structure, mbc = 0.85.

In case the conditions mentioned above overlap, the coefficients of working conditions are obtained bymultiplying the values of the respective coefficients.

Table 3Concrete class

Strength type Symbol Bc3.5

Bc5

Bc7.5

Bc10

Bc15

Bc20

Bc25

Bc30

Bc35

Bc40

Bc50

Bc60

Characteristic strengths, N/mm 2

Compression R ck 3.0 4.5 6.4 8.5 12.5 16.6 20.5 24.3 28.0 31.6 38.5 45.0

Stretching R tk - - 0.76 0.92 1.19 1.43 1.65 1.86 2.03 2.20 2.51 2.78

Calculation strengths, basic values, N/mm 2

Compression R c* 2.2 3.2 4.7 6.5 9.5 12.5 15.0 18.0 20.5 22.5 26.5 31.6

Stretching R t* - - 0.50 0.60 0.80 0.95 1.10 1.25 1.35 1.45 1.65 1.85

Table 4

Casting procedure Smallest size of the crosssection< 300 mm 300 mm

m bc = m bt Elements cast horizontally 0.85 1.00Elements cast vertically (pillars, membranes, walls) or inclined withformings on all sides 0.75 0.85


4/12

STAS 10111/2-87 - 4 -

3.1.7 The coefficient of elasticity of concrete under compression strain in short term loads is given in table 5.

Table 5Concreteclass Bc 7.5 Bc 10 Bc 15 Bc 20 Bc 25 Bc 30 Bc 35 Bc 40 Bc 50 Bc 60

E b N/mm 2 14000 21000 24000 27000 30000 32500 34500 36000 38000 40000

The coefficient of elasticity of concrete under stretching strain is considered to be equal with thecoefficient under compression.Transversal strain coefficient is considered = 0.2.The transversal coefficient of elasticity is considered Gb = 0,4 E b.

3.1.8 The linear dilatation coefficient for concrete, reinforced concrete and prestressed concrete elements isconsidered to be t = 1.0 x 10

-5.

3.1.9 The total final specific strain of concrete in use, bt, at the end of the slow flow and contraction is expressedthrough the relation:

(1)where:

be initial specific strain under various strains of concrete, calculated with the value of the elasticitycoefficient E b corresponding to the class of concrete;

bd specific lasting strain of concrete, calculated according to annex A

3.1.10 In order to calculate sections of reinforced concrete elements considering correlation between unit stress andspecific strains, take the unit stress strain curve shown in fig. 1.

Fig. 1Translation NOTE - all the values written with a coma (e.g.: 3,1 ...) in this figure are to be read with a dot (e.g.: 3.1...)

3.2 Reinforcement

3.2.1 Characteristic strengths (R ak ) and calculation strengths (R a) (basic values) of reinforcements for different typesand diameters of steel for non-prestressed reinforcements are given in table 6.

Table 6

No Type of steelNormalised strength

R ak N/mm2

Calculation strengthR a

N/mm2 1 PC 60 d = 6...40 mm 430 350

d 14 mm 360d = 16...28 mm 340

3002 PC 52

d = 32...40 mm 330 290d 12 mm 2553 OB 37d > 12 mm 235 210d 4 mm 490d = 4.5...7.1 mm 440 3704 STNBd > 7.1 mm 390 325

C e n

t r e c o m p r e s s

i o n

Eccentriccompression,axis outsidethe section

F l e x u r e , c

o m p r e s s i o n a n

d

e l o n g a t

i o n , n e u

t r a l a x

i s i n s i

d e

t h e s e c t

i o n


5/12

STAS 10111/2-87- 5 -

3.2.2 The coefficient of elasticity of bar reinforcements is considered: E a = 210,000 N/mm

2, for PC 60, PC 52 and OB 37 E a = 200,000 N/mm

2, for STNB

3.2.3 The pre-tensioned reinforcement of prestressed concrete elements should be composed of:- smooth wires SBP, STAS 6482/2-80 or impressed wires SBPA, STAS 6482/3-80:

isolated or grouped in fascicles (in parallel) gauze wires with two or three wires (litz wire)

- wire strands TBP, STAS 6482/4-80, isolated.

3.2.4 Characteristic strengths ( R pk ) and calculation strengths ( R p) (basic values) of prestressed reinforcements aregiven in table 7.

Table 7

*) For wire strands the diameter is considered to equal 3 diameters of the peripheral wires.Translation NOTE - all the values written with a coma (e.g.: 3,1 ...) in this figure are to be read with a dot (e.g.: 3.1...)

3.2.5 The coefficient of elasticity of pre-stressed reinforcements ( E p) is considered: E p = 200000 N/mm

2, for SBP, SBPA and for straight fascicles over 50 m length; E a = 180000 N/mm

2, for wire strands, litz wires and fascicles.

3.2.6 For hot-rolled steels (PC60, PC52, OB37), the characteristic curve ( -) may be used, as in fig. 2.

Fig. 2

No. Type of reinforcement Diameter of

reinforcementmm

Characteristic strengthR pk

N/mm2

Calculation strengthR p

N/mm2


6/12

STAS 10111/2-87 - 6 -

3.2.7 For SBP, SBPA, TBP steels, the characteristic curve ( p- p) may be used, as in fig. 3:for (2)

for (3)

Fig. 3

Translation NOTE - all the values written with a coma (e.g.: 3,1 ...) in this figure are to be read with a dot (e.g.: 3.1...)

The specific calculation limit strain of pre-tensioned reinforcement is considered 0.010 l += (according tosubclause 7.3.3.2).

3.3 Calculation characteristics of concrete and reinforcements to the fatigue limit state

3.3.1 Elements under repeated stresses inducing fatigue should be calculated by taking into consideration theasymmetry coefficient established with the relation:

(4)

where min , respectively max is the minimal, respectively maximal unit stress, established based on the exploitationvalues of the loads; use with (+) or (-), according to the conventional sign of the stress.

3.3.2 Calculation fatigue strengths

c R0 for concrete in reinforced and prestressed concrete elements should be

established using the relation:

(5)where:

bm0 = 0.6 +0.5 1.0

according to subclause 3.3.1

c R* basic value of the concrete calculation strength, given in table 3

k n coefficient depending on the number of cycles: for current constructions k n = 1; if the number of cycles during exploitation exceeds 2 x 10 6, k n is calculated with the relation:

(6)

where n is the number of cycles in millions, but maximum n = 10.

3.3.3 Calculation fatigue strengths

c R0 for reinforcements in reinforced concrete elements should be established

using the relation:

where:

Ra basic value of the calculation strength given in table 6

am0 strength reduction coefficient as a result of repeated stress, given in table 8

a sm coefficient that includes the effect of welding, given in table 9.


7/12


8/12

STAS 10111/2-87 - 8 -

4.2 The overturning stability (fig. 4) is verified using the relation:

(7)

Fig. 4

where M rc conventional overturning moment, equalling the sum of the moments of all forces, in relation to point G,

located at the midpoint between the two bearings; M sl limit stability moment, equalling the moment of the vertical component of the resultant R, in relation with

point G; it is considered that the resultant acts at a distance20

b x = , that is, in the support point A, against

which the overturning stability is verified; N i components of the forces, having a direction normal, to the line of the bearings ( i = 1; 2... n); H i components of the forces, having a direction parallel with the line of the bearings ( i = 1; 2 n);ci, h i lever arms of the components of the N i respectively H i forces, in relation to point G

(i = 1;2... n);eo distance from point G to the point in which the resultant R crosses the line of the bearings;

xo distance from point G to the support point A against which the overturning stability is verified;mS coefficient of the working conditions, being:

0.95 when verifying the bridge stability in longitudinal line;0.85 when verifying the bridge stability in transversal line.In relation (7), the moments of the forces should be introduced with their signs, depending on their sense of

action.

5 CALCULATION ON PLAIN CONCRETE ELEMENTS

5.1 Verifications required

5.1.1 Calculation on plain concrete elements should include:- verification to strength limit state under the action of loads considered in limit values, in the most

disadvantageous grouping, taking into consideration the dynamic coefficient, according to subclause 5.2;- specific verifications to limit states of normal use, according to subclause 5.3.

NOTES:1 Plain concrete elements of suprastructures should not be verified in fatigue limit state.2 Elements for which verification in position stability limit state should be calculated:

for overturning, according to clause 4 in this standard and according to STAS 10111/1-77; for sliding, according to STAS 101111/1-77.

5.1.2 Elements should be executed from plain concrete only if they comply with the terms specified under subclause 5.3.


9/12

STAS 10111/2-87- 9 -

5.2 Verification to strength limit state

5.2.1 Elements of plain concrete under centric compression should be calculated as elements under eccentriccompression; the calculation bending moment, called additional moment, should be established from the relation:

M = N e a (8) where:

N longitudinal force from calculation loads considered as per subclause 5.1.1;ea additional eccentricity, equalling the highest of the following values: 20 mm or h/30, where h is theheight of the cross section. The additional eccentricity may be present in any direction.

5.2.2 Elements under eccentric compression, with eccentricity on a main direction, should be verified under strengthlimit state using the relation:

M * M cap (9)where

M * calculation bending moment, established using the relation:

M * = M + N e a (10)

M cap capable bending moment (load carrying capacity) in the section considered, established using therelation:

M cap = N e b (11)

M bending moment produced by calculation loads

N and ea according to subclause 5.2.1;

eb distance between the centroid of the cross section and the centroid of the compressed area ( Abc).

The surface of the compressed area ( Abc) is established using the relation:

(12)

For rectangular sections, the capable bending moment in the section considered is established using therelation:

(13)

where h is the height of the cross section, and x is determined using the relation:

(14)

where b is the width of the cross section.

5.2.3 Elements under eccentric compression with eccentricity on any direction should be verified under strengthlimit state using the relation:

(15)

where M * x and M * y bending calculation moments produced by the calculation loads, determined using the

following relations:

(16)

(17)

M *x and M *y bending moments on the two main directions (x and y), established with calculation loads, N longitudinal force from calculation loads;


10/12

STAS 10111/2-87 - 10 -

eax the highest of the following values: the side parallel with the bending plan M x divided by 30 and20 mm;

eay the highest of the following values: the side parallel with the bending plan M y divided by30 and 20 mm;

M capx and M capy capable moments of the section on the two main directions (x and y), established with therelations:

(18)

(19)

ebx and eby distances between the centroid of the cross section and the centroid of the compressed area(Abc ) measured on the direction x, respectively y

The surface of the compressed area (Abc ) is established using relation (12):

For rectangular sections, M capx and M capy are established using the relations:

(20)

(21)

where x is determined using relation (14), and y, using the relation:

(22)

The exponent in relation (15) is established using the relation:

= 1.5 (1 - 0.85 n) (23)

for irregular sections

for rectangular sections

In these relations, Ab is the surface of the cross section.

5.3 Verifications specific to normal exploitation limit states

5.3.1 For elements with rectangular sections under eccentric compression on one single direction, eccentricityshould comply with the following relation:

eo cxo (24)

where:eo eccentricity of the resultant established with exploitation loadsc coefficient, taking the following values:

0.5 for actions in group I;0.6 for actions in group II;0.67 for actions in group III;

xo distance from the centroid of the section to the side most compressed.If the value obtained for the eccentricity ( eo) is higher than the values resulting from relation (24), but not for

more than 10 %, a reinforcement having a surface of 0.05 % of the surface of the concrete section should be used on thestretched area.

For values exceeding for more than 10 %, the reinforcement required should be established following the procedures for reinforced concrete elements.

5.3.2 For elements with rectangular sections under eccentric compression on two directions ( x and y) and for elements of any shape (triangle, trapezium, parallelogram, polygon, circle), the active section ( Abc) should comply withthe following requirement:

Abc ca Ab (25)


11/12

STAS 10111/2-87- 11 -

whereca coefficient, taking the following values:

0.75 for actions in group I;0.60 for actions in group II;0.50 for actions in group III;

Ab total surface of the section.

5.4 Verification for local concentrated forces5.4.1 The effective unit stress ( Al ) induced by the local force under the support plates (the plates of the supportapparatus, counterweights, braces of prestressed elements, etc.) should be established using the relation:

(26)

where: P E force normal to the support plate, from loads taking exploitation values. For prestressed concrete

elements, P E is the control force increased by 10 %; Al the surface of the support plate; if the force P

E acts off-centre on the support plate, it should beestablished according to annex C, subclause C 1.

5.4.2 If:

Al 0.7 Rc (27)

the concrete under the support plate may take over the stretch stress induced by local unit stress actions, without anyspecial reinforcement measures being required.

In the relation above, Rc is the calculation strength of the concrete (plain or reinforced) used in the element onwhich the plate stays, taking values as per subclause 3.1.6.

The concrete under the support plates should be at least class Bc 25, used on a height equal to minimum thewidth of the support plate and at least 400 mm.

The edge of the support plate should be withdrawn from the edge of the concrete element for a distance at leastequal to the width of the support plate a l ; if the distance is approximately a l , the concrete under the support plate will bereinforced with a net of structural steel 8 with approximately 150 mm meshes with adequate concrete coverage.Welded nets of smooth drawn wires (STNB) with 6 mm diameter and 100 mm meshes may be used.

Minimal distances specified in STAS 10111/1-77 shall be observed for support apparatus in addition to theminimal distance a l .

5.4.3 If the distance from the edge of the concrete element to the edge of the support plate is smaller than the widthof the support plate, or when:

Rcl Al > 0.7 Rc (28)

the concrete mass under the support plates (of the support apparatus, counterweights, braces of pre-tensionedreinforcements, etc.), referred to as bearing should be reinforced with structural steel bars resulting from thecalculations, as per annex C.

In relation (28), Rcl is the calculation local compression strength and should be determined as per annex C.

6 PROVISIONS REGARDING THE CALCULATION AND COMPOSITION OFREINFORCED CONCRETE ELEMENTS

6.1 Verifications required6.1.1 Calculation on reinforced concrete elements should include:

- verification to the strength limit condition;

- verification to the fatigue limit condition*);- verification to the cracking limit condition;- verification to the strain limit condition;

NOTE:*) Road bridges and footbridges should be checked for fatigue only if they match the provisions under subclause 1.3.


12/12

STAS 10111/2-87 - 12 -

6.1.1.1 If resulting as necessary, the verification for the position stability limit state (overturning, sliding) should beverified as well.

6.1.1.2 The elements of footbridges embedded in the backfill for which the stress is calculated without the dynamiccoefficient should not be verified under fatigue limit state.

6.1.2 The verification to strength limit state for elements under compression and eccentric compression stress should be made taking into consideration the flexibility influence coefficient as well, according to subclause 6.2.5.

For special cases (elements having a special shape of the cross section, elements under complex stress, massiveelements), verification to the strength limit state may be conducted by setting the requirement that the unit stress in theconcrete and reinforcements, induced by the limit loads, determined in stage II of the works, not exceed the calculationstrengths.

6.2 Verification to the strength limit state, in normal sections

6.2.1 The calculation of stress (section stress) is done by taking into consideration the limit values of the loads with adynamic coefficient in the most disadvantageous grouping.

6.2.2 The distribution of unit stresses in the calculation to the strength limit state in normal sections should beestablished considering the following hypotheses:

- normal plane sections stay plane after the distortion of the element (hypothesis of plane sections);- the elongation strength of the concrete should be neglected;- the - curves of the concrete and reinforcements are the ones presented in fig.1 and fig.2;- the specific compression limit strain of the concrete blim , should be considered 3.5 if the neutral axis isinside the section (see fig. 1) and 2 in the conventional case of centre compression; between the two limits,the values of bllm should be calculated from the relation:

(29)

where:

- the specific elongation, a llm of the reinforcement should be considered 10 .

NOTE For non-linear analyses on groups of loads including seismic action, values of blim and a lim different from theones mentioned may be adopted based on special prescriptions.

6.2.3 Calculation in normal sections of reinforced concrete elements under bending, off-centre compression and off-centre tensile stress with high eccentricity should be done considering that (fig. 5):

- unit stresses in the concrete in the compressed area have a constant value Rc

- stress a' in reinforcement a A

' should be considered in the calculation as having the value (- Ra), if x > 2a;

otherwise a simplified calculation may be done, in which the resultant of all compressions at the level of the

centroid of the a A' reinforcements is considered;

- stress a in the reinforcement Aa, concentrated at the stretched or less compressed edge, should be used in thecalculations as having the values:

if (31)

if . . (32)

if (33)

Translation NOTE - all the values written with a coma (e.g.: 3,1 ...) in this relations are to be read with a dot (e.g.: 3.1...)

en stas 10111-2-87 part 1_suprastructuri_beton

Documents