Bridge Pile Bent P-Delta Curves in Transverse Direction Using FB-Pier and GTSTRUDL Pushover Analysis Procedures

Abstract

Extreme flood events may create large transverse water loads that cause piles of a bent to bend about their weak axes in addition to causing scour. A comparison of the nonlinear pushover analysis procedures and resulting p-delta curves for bridge bents using GTSTRUDL and FB-Pier is presented in this thesis to determine which program most accurately models the pushover behavior of bents during these extreme flooding events. The buckling and pushover capacities of typical standard ALDOT non X-braced and X-braced bents are evaluated for various levels of scour. Stability of the non X-braced bents in the transverse direction is assessed to determine if the end battered piles provide sufficient lateral bracing to prevent sidesway. Several bent parameters were varied to examine sensitivities to flexural stiffness of the piles/bent including soil stiffness modulus, degree of end pile battering, and flexural stiffness of the bent cap. Special consideration was also given to the connections of the piles to the ground and bent cap. It was estimated that these connections would be most accurately modeled with 50% rotational fixities, but neither GTSTRUDL nor FB-Pier have the ability to model partial fixities. Thus, alternate modelings were examined to develop bent models which are believed to behave similarly to those in the field. Conclusions and recommendations are then made based on which computer program models, FB-Pier or GTSTRUDL, provide the most appropriate pushover analysis modeling for in-situ bents.