Dynamic response of highway girder bridges

The objective of the paper is to investigate the variation of dynamic loading of girder bridges with different girder number and span length due to several vehicles moving across rough bridge decks. Nine girder bridges with girder number ranging from four to eight and span length changing from 40 to 120 ft are designed based on the AASHTO standard highway bridges and modeled as grillage beam systems. The vehicle is simulated as a nonlinear vehicle model with 11 d.f. according to the HS20-44 truck design loading contained in the AASHTO specifications. Four types of road surface roughness generated from power spectral density function for very good, good, average and poor roads in accordance with International Organization for Standardization (ISO) specifications are used in this study. The maximum impact factors of different girders of bridges are obtained for different number of loading trucks (side by side), road surface roughnesses, transverse loading positions and the vehicle speeds changing from 15 to 75 mph. The conclusions reached in this study are useful in the further study of the impact of highway bridges and for practical bridge design engineers.