Design Guide for Bridges for Service Life (2013) / Chapter Skim
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Pages 561-571
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From page 561... ...
559 This appendix summarizes the work for addressing the effect of skew on lateral movement of the bridge at the abutment. B.1 bAckground A skewed bridge is a bridge with the longitudinal axis at an angle other than 90° with the piers and abutments.
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From page 562... ...
560 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Figure B.1. Components of abutment soil passive pressure response to thermal elongation in skewed integral abutment bridges.
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From page 563... ...
561 Appendix B DiSpLACEMENT OF SKEWED BRiDGE Figure B.3.
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562 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Because of potential problems and uncertainty related to the response of skewed integral abutments, many state departments of transportation limit the skew angle. A typical limit for maximum skew angle for integral abutment bridges used by many states is 30°.
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From page 565... ...
563 Appendix B DiSpLACEMENT OF SKEWED BRiDGE B.2 AnALySeS For trAnSverSe reSPonSe to thermAL exPAnSion B.2.1 Skew Angle Limit for Limiting transverse Effects Figure B.6 shows the passive soil pressure response (Pp)
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From page 566... ...
564 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE With larger skew angles, the integral abutment either can be designed to resist the transverse force generated by the soil passive pressure in an attempt to guide the abutment movement to be predominantly longitudinal, or it can be detailed to accommodate the transverse movement. B.2.2 forces Required to Resist transverse movement Adding lateral resistance of the abutment (Fa)
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From page 567... ...
565 Appendix B DiSpLACEMENT OF SKEWED BRiDGE For relatively short bridges or bridges in locations with small effective temperature ranges, it may be feasible to design the abutment substructure to resist Fa .
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From page 568... ...
566 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE B.3 exPected trAnSverSe movement with tyPicAL integrAL Abutment B.3.1 method of Analyses To investigate the relationship between skew angle and expected transverse movement for a typical integral stub abutment, a set of relationships was derived based on equilibrium and the compatibility of end abutment forces in the plane of the bridge superstructure. For this analysis, the superstructure is assumed to act as a rigid body with rotation b about the center of the deck (for a longitudinally symmetrical bridge)
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From page 569... ...
567 Appendix B DiSpLACEMENT OF SKEWED BRiDGE B.3.3 Sensitivity Analyses for the Effects of Skew Angle on transverse movement and Longitudinal Restraint To demonstrate the effects of skew angle on expected transverse movement and longitudinal restraint forces, further analyses were carried out using the spreadsheet program.
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From page 570... ...
568 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE in the analyses by decreasing the width and keeping the length constant. The length of the wingwall at each skew angle was constant; therefore, the results in Figure B.9 demonstrate the effects of increasing the ratio of the length of the wingwalls to the length of the abutment wall.
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From page 571... ...
569 Appendix B DiSpLACEMENT OF SKEWED BRiDGE B.3.4 Design Recommendations Because the baseline abutment used in these analyses is a relatively typical stub abutment (but also relatively deep, with an abutment height of 13.0 ft and with strong axis pile bending for movement normal to the abutment versus weak axis bending for movement parallel to the abutment)
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