Dynamic Response of Multigirder Bridges

Abstract

The objective of the paper is to study the dynamic behavior of multigirder bridges due to vehicles moving across rough bridge decks. The multigirder bridge is modeled as a grillage beam system. The vehicles are simulated as two nonlinear vehicle models with seven and 12 degrees of freedom according to the H20–44 truck and HS20–44 truck design loadings contained in the American Association of State Highway and Transportation Officials (AASHTO) specifications, respectively. The road‐surface roughnesses of the approach roadways and bridge decks are generated from power spectral density function for very good, good, average, and poor roads in accordance with International Organization for Standardization (ISO) specification. A prestressed‐concrete bridge with span of 20 m is designed based on AASHTO standard bridge girders. The dynamic responses of the longitudinal girders are calculated for single truck and two trucks (side by side), with different speeds and road‐surface roughness. The analytical results show that the transverse diaphragms of bridges greatly affects the lateral dynamic, load distribution of concrete multigirder bridges. In order to verify the proposed procedure for calculation of the dynamic load, the theoretical results obtained have been compared with experimental data reported by Fenves et al. (1962). The comparison shows that the agreement between experiment and theory is quite satisfactory.