Comparative Study on the Effect of Number of Girders on Live Load Distribution in Integral Abutment and Simply Supported Bridge Girders

Abstract

In this study, the effect of the number of prestressed concrete girders on the distribution of live load effects among the girders of integral abutment bridges (IABs) and simply supported bridges (SSBs) is investigated. For this purpose, two and three dimensional finite element models (FEMs) of several single-span IABs and SSBs are built and analyzed. In the analyses, bridges with various superstructure properties, such as span length, girder type and size, slab thickness are considered. The finite element analyses (FEA) results are then used to calculate the live load distribution factors (LLDFs) for the girders of IABs and SSBs as a function of the number of girders. Comparison of the analyses results revealed that, LLDFs for SSBs vary slightly as the number of girders changes. However, in the case of IABs, it is found that while the LLDFs for the girder moments decrease significantly as the number of girders increases, the number of girders has a negligible effect on the LLDFs for the girder shear. Accordingly, the number of girders is added as a new parameter to the previously developed correction factors for AASHTO LRFD LLDFs for the girder moment. It is observed that the developed formulae yield a reasonably good estimate of live load effects in prestressed concrete IAB girders.