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BSI PD 6687-2:2008

BSI PD 6687-2:2008

$167.15

Recommendations for the design of structures to BS EN 1992-2:2005

Published By Publication Date Number of Pages
BSI 2008 36
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This Published Document contains non-contradictory complementary information for use with BS EN 1992-2 and its UK National Annex for the design of concrete structures. It does not cover assessment.

This Published Document gives:

  1. background to the decisions made in the National Annex to BS EN 1992-2 for some of the Nationally Determined Parameters;

  2. commentary on some specific subclauses from BS EN 1992-2;

  3. commentary on the application to bridge structures of some specific subclauses of BS EN 1992-1-1 that are called up in BS EN 1992-2;

  4. guidance on subjects not covered by BS EN 1992-2, but previously included in British Standards and other standards and codes of practice.

PDF Catalog

PDF Pages PDF Title
3 Contents
1 Scope 1
2 General 2
3 Basis of design 2
4 Materials 3
5 Durability and cover to reinforcement 4
6 Structural analysis 4
7 Ultimate limit states 9
8 Serviceability limit states 19
9 Detailing of reinforcement and prestressing tendons – General 20
10 Detailing of members and particular rules 24
11 Additional rules for precast concrete elements and structures 27
12 Additional rules for external prestressing 28
Bibliography 29
List of figures
Figure 1 – Imperfections for pier built in at both ends 5
Figure 2 – Limiting strain distributions 10
Figure 3 – Illustration of increment size for shear reinforcement design 13
Figure 4 – Reinforcement SAsw to include in punching check 16
Figure 5 – Illustration of quadruply staggered laps 21
Figure 6 – Corner pile within 2d of a column base 26
List of tables
Table 1 – Effective height, l0, for columns 8
Table 2A – Limiting stress ranges – Longitudinal bending for unwelded reinforcing bars in road bridges 18
Table 2B – Limiting stress ranges – Transverse bending for unwelded reinforcing bars in road bridges 18
Table 3 – Minimum spacing of post-tension ducts 23
Table 4 – Minimum radius of curvature of tendons in the deviators 24
4 Foreword
5 Introduction
1 Scope
a) background to the decisions made in the National Annex to BS EN 1992-2 for some of the Nationally Determined Parameters;
b) commentary on some specific subclauses from BS EN 1992-2;
c) commentary on the application to bridge structures of some specific subclauses of BS EN 1992-1-1 that are called up in BS EN 1992-2;
d) guidance on subjects not covered by BS EN 1992-2, but previously included in British Standards and other standards and codes of practice.
6 2 General
2.1 Definition of National Authority [BS EN 1992-2:2005, Foreword]
3 Basis of design
3.1 Actions and environmental influences [BS EN 1992-1-1:2004, 2.3.1]
3.2 Partial factors for materials [BS EN 1992-1-1:2004, 2.4.2.4 (3) and Annex A]
7 4 Materials
4.1 Creep and shrinkage [BS EN 1992-1-1:2004, 3.1.4]
4.2 Design compressive and tensile strengths [BS EN 1992-2:2005, 3.1.6 (101)P]
4.3 Confined concrete [BS EN 1992-1-1:2004, 3.1.9]
4.4 Ductility characteristic [BS EN 1992-2:2005, 3.2.4]
8 5 Durability and cover to reinforcement
5.1 Requirements for durability [BS EN 1992-1-1:2004, 4.3]
6 Structural analysis
6.1 Second order effects [BS EN 1992-1-1:2004, 5.1.4 (1)P]
6.2 Geometrical imperfections [BS EN 1992-1-1:2004, 5.2]
9 Figure 1 Imperfections for pier built in at both ends
6.3 Linear elastic analysis [BS EN 1992-1-1:2004, 5.4]
10 6.4 Linear elastic analysis with limited redistribution [BS EN 1992-1-1:2004, 5.5]
6.5 Plastic analysis [BS EN 1992-1-1:2004, 5.6]
6.6 Rotation capacity [BS EN 1992-1-1:2004, 5.6.3]
11 6.7 Analysis of second order effects with axial load [BS EN 1992-1-1:2004, 5.8]
6.7.1 Slenderness and effective length of isolated members [BS EN 1992-1-1:2004, 5.8.3.2]
a) rotational restraint is at least 4(EI)/l for cases 1, 2 and 4 to 6, and 8(EI)/l for case 7, where (EI) is the flexural rigidity of the column;
b) lateral and rotational rigidity of elastomeric bearings are negligible;
c) the height of bearing is negligible compared with that of the column.
12 Table 1 Effective height, l0, for columns
13 6.7.2 Creep [BS EN 1992-1-1:2004, 5.8.4]
7 Ultimate limit states
7.1 Bending with or without axial force [BS EN 1992-1-1:2004, 6.1]
7.1.1 Strain distributions [BS EN 1992-1-1:2004, 6.1 (5) and 6.1 (6)]
14 Figure 2 Limiting strain distributions
7.1.2 External prestressing strain between fixed points [BS EN 1992-2:2005, 6.1 (108)]
15 7.1.3 Robustness of prestressed elements [BS EN 1992-2:2005, 6.1 (109)]
7.2 Shear [BS EN 1992-1-1:2004, 6.2]
7.2.1 Evaluation of chord forces [BS EN 1992-1-1:2004, 6.2.1 (1)P]
7.2.2 Shear enhancement [BS EN 1992-2:2005, 6.2.2 (101) and BS EN 1992-1-1:2004, 6.2.2 (6)]
7.2.3 Shear resistance of uncracked prestressed members [BS EN 1992-1-1:2004, 6.2.2 (2)]
16 7.2.4 Members requiring design shear reinforcement [BS EN 1992-1-1:2004, 6.2.3]
7.2.4.1 Evaluation of inner lever arm [BS EN 1992-1-1:2004, 6.2.3 (1)]
7.2.4.2 Web crushing limits [BS EN 1992-2:2005, 6.2.3 (103)]
17 7.2.4.3 Design for smallest value of VEd in an increment [BS EN 1992-1-1:2004, 6.2.3 (5)]
Figure 3 Illustration of increment size for shear reinforcement design
18 7.2.4.4 Additional tensile force [BS EN 1992-2:2005, 6.2.3 (107)]
7.2.4.5 Segmental construction [BS EN 1992-2:2005, 6.2.3 (109)]
7.2.5 Shear between web and flange [BS EN 1992-1-1:2004, 6.2.4]
7.2.6 Shear at the interface between concrete cast at different times [BS EN 1992-1-1:2004, 6.2.5]
19 7.3 Punching [BS EN 1992-1-1:2004, 6.4]
7.3.1 Distribution of shear with eccentric support reaction
7.3.2 Distribution of shear reinforcement [BS EN 1992-1-1:2004, 6.4.5]
20 Figure 4 Reinforcement to include in punching check
7.4 Design with strut and tie models [BS EN 1992-1-1:2004, 6.5]
7.4.1 Struts [BS EN 1992-1-1:2004, 6.5.2]
21 7.5 Partially loaded areas [BS EN 1992-1-1:2004, 6.7]
7.6 Fatigue [BS EN 1992-1-1:2004, 6.8]
7.6.1 Verification conditions [BS EN 1992-2:2005, 6.8.1 (102)]
7.6.2 Verification of concrete under compression or shear [BS EN 1992-2:2005, 6.8.7 (101)]
7.6.3 Limiting stress range for reinforcement under tension [BS EN 1992-1-1:2004, 6.8.6 (1)]
22 Table 2A Limiting stress ranges – Longitudinal bending for unwelded reinforcing bars in road bridges
Table 2B Limiting stress ranges – Transverse bending for unwelded reinforcing bars in road bridges
7.7 Shell elements [BS EN 1992-2:2005, Annex LL]
23 8 Serviceability limit states
8.1 Stress limitation [BS EN 1992-1-1:2004, 7.2]
8.1.1 Concrete in compression [BS EN 1992-2:2005, 7.2 (102)]
8.1.2 Reinforcement [BS EN 1992-1-1:2005, 7.2 (5)]
8.2 Crack control [BS EN 1992-1-1:2004, 7.2]
8.2.1 Recommended values of wmax [BS EN 1992-2:2005, Table 7.101N]
a) For XD or XS exposure, BS EN 1992-2:2005, Table 7.101N requires only decompression. While this will be satisfactory in the im…
b) The decompression requirement is specified for durability of tendons. The recommended distance from the tendons where decompr…
c) Because the exposure is defined at the surface but decompression is checked at the tendon, there was a lack of clarity when the surface with the most severe exposure classification is not the most tensile face.
d) It has been clarified that the exposure used is the worst the surface is exposed to, even if the cracking will arise at a different time.
e) It has been found that compliance with the recommended rules is unduly restrictive in the case of tops of the precast beams a…
24 8.2.2 Concrete cover to be used in the evaluation of crack spacing and crack width [BS EN 1992-1-1:2004, 7.3.4]
8.2.3 Crack width due to restrained imposed deformation
9 Detailing of reinforcement and prestressing tendons – General
9.1 Laps [BS EN 1992-1-1:2004, 8.7]
25 Figure 5 Illustration of quadruply staggered laps
26 9.2 Spacing of post-tension ducts [BS EN 1992-1-1:2004, 8.10.1.3]
9.3 Anchorage zones of post-tensioned members [BS EN 1992-1-1:2004, 8.10.3]
27 Table 3 Minimum spacing of post-tension ducts
28 9.4 Deviators [BS EN 1992-1-1:2004, 8.10.5]
Table 4 Minimum radius of curvature of tendons in the deviators
10 Detailing of members and particular rules
10.1 Shear reinforcement and torsion reinforcement [BS EN 1992-1-1:2004, 9.2.2 and 9.2.3]
29 10.2 Compression reinforcement of beams and columns [BS EN 1992-1-1:2004, 9.2.1.2 (3) and 9.5.3 (6)]
a) Links should be so arranged that every corner and alternate bar or group in an outer layer of compression reinforcement is held in place by a link anchored in accordance with BS EN 1992-1-1:2004, Figure 8.5 a) or b).
b) All other compression reinforcement should be within 150 mm of a bar held in place by a link.
c) The minimum size of the transverse reinforcement and links, where necessary, should be in accordance with BS EN 1992-1-1:2004, 9.5.3 (1).
10.3 Additional longitudinal reinforcement with unbonded tendons [BS EN 1992-1-1:2004, 9.2.1.3 (2)]
10.4 Pile caps
a) Flexural shear on planes passing across the full width of the pile cap. Flexural shear should be checked on planes passing ac…
30 b) Maximum permissible shear stress for punching. The maximum permissible shear stress at the face of piles and piers should be …
c) Punching resistance of corner piles. Corner piles should be checked for punching resistance at a 2d perimeter (without support enhancement) ignoring the presence of the pier or support and any vertical reinforcement within it.
Figure 6 Corner pile within 2d of a column base
10.5 Requirements for voided slabs
10.5.1 General
31 10.5.2 Transverse shear
a) the increased stresses in the transverse reinforcement and shear links due to cell distortion resulting from transverse shear…
b) the resistance of the flanges and webs to the local moments produced by the transverse shear effects should be verified.
10.5.3 Longitudinal shear
10.5.4 Punching
10.5.5 Transverse reinforcement
a) in the predominantly tensile flange either 1 500 mm2/m or 1% of the minimum flange section, whichever is the lesser;
b) in the predominantly compressive flange either 1 000 mm2/m or 0.7% of the minimum flange section, whichever is the lesser.
11 Additional rules for precast concrete elements and structures
11.1 Dynamic effects [BS EN 1992-1-1:2004, 10.2 (2)]
32 12 Additional rules for external prestressing
a) All external and unbonded tendons should be replaceable. Where the detailing does not enable tendons to be removed and replac…
b) Where it is necessary to restrict traffic on the bridge to replace the tendons, the extent of this restriction should be agreed with the client and defined in a method statement
c) Bridges should be checked to ensure that the removal either of any two tendons or of 25% of those at one section, whichever has the more onerous effect, will not lead to collapse at the ultimate limit state under the design ultimate permanent loads.
d) Where tendon restraints are widely spaced (typically at distances greater than 12h) checks should be made to ensure the natural frequency of the free length of tendons is not resonant with that of the structure as a whole.
33 Bibliography
[1] fib Bulletin D’Information No. 242. Ductility of reinforced concrete structures, Lausanne: Comite Euro-International du Beton, 1998.
[2] HENDY, C.R., and D.A. SMITH. Designers’ guide to EN 1992-2. London: Thomas Telford. 2007. ISBN: 0727731599.
[3] DENTON, S.R., The strength of reinforced concrete slabs and the implications of limited ductility. PhD Thesis, Cambridge University, 2001.
[4] CLEMENTS, S. W., CRANSTON, W. B. and M. G. SYMONS. Influence of section breadth on rotation capacity, Cement and Concrete Association, Technical Report 533, Slough, 1980.
[5] JACKSON, P.A. Slender concrete bridge piers and the effective height provisions of BS 5400: Part 4: 1984. Wexham Springs: Cement and Concrete Association, June 1985. Publication 42.561.
[6] WESTERBERG, B. Second order effects in slender concrete structures: Background to the rules in EC2. KTH TRITA-BKN Report 77. 2004.
[7] JACKSON, P. and S. SALIM. Web crushing in EN 1992. The Structural Engineer. 2006, 84 (23), 50-57.
[8] SCHLAICH, J., SCHAFER, K and M. JENNEWEIN, Toward a consistent design of structural concrete, PCI Journal. 1987, 32(3), 74-150.
[9] WOOD, R.H. The reinforcement of slabs in accordance with a pre-determined field of moments. Concrete. 1968, 2, 69-76.
[10] ARMER, G.S.T. Correspondence on Wood, R.H. [17], Concrete. 1968, 2, 319-320.
[11] DENTON, S.R., and C.J. BURGOYNE. The assessment of reinforced concrete slabs. The Structural Engineer. 1996, 74 (9), 147-152.
34 [12] HIGHWAYS AGENCY, BD 57/01 Design for Durability Highways Agency, 2001. Design Manual for Roads and Bridges Vol1 Section 3 Part 8.
[13] CIRIA Report C660, Early age thermal crack control in concrete, London: CIRIA, 2007.
[14] CIRIA Guide 1, A guide to the design of anchor blocks for post-tensioned prestressed concrete members, London: CIRIA, 1976.
[15] SERVICE D’ETUDES DES ROUTES ET AUTOROUTES. External prestressing. Bagneux, France: SETRA, 1990.
[16] CLARK, L.A. and P. THOROGOOD. Flexural and punching shear strengths of concrete beams and slabs. Transport and Road Research Laboratory, Contractor Report 60, 1987.
[17] ELLIOTT, G., CLARK, L. A. and R.M. SYMMONS. Test of a quarter-scale reinforced concrete voided slab bridge. Cement and Concrete Association. 1979
[18] WALKER, G. Strength assessment of reinforced concrete voided slab bridges. PhD thesis, Cambridge University, 2006.
[19] CLARK, L.A. and G. ELLIOTT. Crack control in concrete bridges. The Structural Engineer. 1980, 58A(5), 157-162.
BSI PD 6687-2:2008
$167.15