Live load effects in hammer-head piers of continuous highway bridges and design equations based on numerical simulations verified by field tests

In this study, design equations are proposed to calculate the internal forces in hammer-head bridge pier components under the effect of live loads. For this purpose, first, the finite element model (FEM) of an existing bridge is built and the modeling approach is verified against field test results. Next, a four-span benchmark bridge representative of the bridges in the US is selected. FEM of the benchmark bridge is built, and sensitivity analyses are performed on the bridge model to identify the bridge parameters affecting the magnitude and distribution of the girder live load support reactions and hence the internal forces in the hammer-head pier components. The sensitivity analyses revealed that the number of girders, girder spacing, girder type, slab thickness and the overhang distance significantly affect the magnitude and distribution of the girder live load support reactions and hence the forces in hammer-head pier components. Then, parametric analyses of bridges are performed based on the sensitivity analyses results where each parameter is assigned a wide range of values. Subsequently, minimum least squares regression analyses of more than 50,000 data are performed to obtain equations to estimate the maximum cap beam moment and shear force, the maximum column moment and accompanying axial load as well as the maximum column axial load and accompanying moment. The hammer-head pier forces calculated using the design equations are shown to be in reasonably good agreement with FEM analyses results.