Abstract
Because the methods used to compute the live load distribution for moment and shear force in modern highway bridges subjected to vehicle loading are generally constrained by their range of applicability, refined analysis methods are necessary when this range is exceeded or new materials are used. This study developed a simplified method to calculate the live load distribution factors for skewed composite slab-on-girder bridges with high-performance-steel (HPS) girders whose parameters exceed the range of applicability defined by the American Association of State Highway and Transportation Officials (AASHTO)’s Load and Resistance Factor Design (LRFD) specifications. Bridge databases containing information on actual bridges and prototype bridges constructed from three different types of steel and structural parameters that exceeded the range of applicability were developed and the bridge modeling verified using results reported for field tests of actual bridges. The resulting simplified equations for the live load distribution factors of shear force and bending moment were based on a rigorous statistical analysis of the data. The proposed equations provided comparable results to those obtained using finite element analysis, giving bridge engineers greater flexibility when designing bridges with structural parameters that are outside the range of applicability defined by AASHTO in terms of span length, skewness, and bridge width.
Highlights
Skewed composite high-performance-steel (HPS) I-girder bridges are an economical solution for modern highways subject to space constraints in congested urban areas, providing roadway alignments with low environmental impact and minimal pollution for new road construction projects.unlike in right-angle bridges, where the load transfer to the support is linear, skewed superstructures create high complexity in the force flow
In order to take into account the Association of State Highway and Transportation Officials (AASHTO) limits on performance and safety, it was important to select a set of key parameters and build a matrix that covers a wide range of HPS bridges
Zokaie’s formulas for the Load Distribution Factors (LDFs) of the shear and bending moment, the data presented in Figure 7 reveal that the AASHTO Load and Resistance Factor Design (LRFD) formulas produce highly conservative values for both the bending moment and shear force, which are up to 55% and 25% higher, respectively, than the results obtained by the
Summary
Skewed composite high-performance-steel (HPS) I-girder bridges are an economical solution for modern highways subject to space constraints in congested urban areas, providing roadway alignments with low environmental impact and minimal pollution for new road construction projects. The more recent AASHTO LRFD specifications [13] accept the proposed LDF equations proposed in the National Copperative Highway Research Program (NCHRP) 12-26 project report [14] as an alternative to AASHTO’s standard method These equations significantly boost the accuracy of LDFs, the high complexity and defined limits of applicability often compel bridge designers to perform in-depth analyses. Owing to a lack of simplified methods with which to compute the LDFs of these bridges, bridge engineers must perform complicated analyses when refining their designs To address this problem, this study was undertaken to develop simplified LDFs equations or the bending moment and shear force acting on skewed composite bridges with HPS girders. The proposed equations were verified using a comparative study
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