Experimental and Numerical Evaluations of Live Load Distributions of Steel-Concrete Composite Bridge

Abstract

Live-Load Distribution Factors (LLDFs) are commonly used by the bridge engineers to represent the placement of design lanes to generate the extreme effect in a specific girder. Summing all of the distribution factors for all girders produces a number of design lanes greater than the bridge can physically carry. This research aims to assess the LLDFs suggested by the American Association of State Highway and Transportation Officials (AASHTO) specifications for steel-concrete composite girders bridge. A bridge consisting of four steel plate girders, 1650 mm depth; 33,950 mm span; and connected by shear connectors to a reinforced concrete deck, was investigated experimentally and numerically in this work. Eight trucks of 248 kN each were used with different arrangements to achieve the static test and to obtain the maximum design live load and deflection values for all girders. In addition, a finite element (FE) analysis was implemented for the bridge by using ANSYS. Comparisons among the numerical results and the available measured deflections showed a close agreement. The responses of the bridge, measured during the static test and the FE analysis, was used to assess the LLDFs presented by AASHTO. In addition, the proposed FE model was used to assess the LLDFs for shear and the effect of Cross-Frame Diaphragms (CFDs) on the LLDFs for composite steel girder bridges. The significance of the CFDs to distribute live loads among the girders was confirmed by increasing the LLDFs for exterior girders and decreasing the LLDFs for internal girders.