Bridge vibration and impact under moving vehicles

This paper presents a model for analysis of bridge vibration and impact due to vehicles moving on irregular bridge decks. Emphasis is placed on the effect of road roughness on the bridge dynamic response. The bridge is idealized as a prismatic beam with constant stiffness. A tractor semi-trailer is modeled as a dynamic system with six degrees of freedom. The tires and suspension systems are idealized as linear elastic spring elements and dashpots. The road roughness, defined by power spectral density function, is generated by simulation technique. The envelopes of the bridge dynamic response corresponding to the simulated random roughness profiles are obtained. In addition, sinusoidal profiles are used to study the roughness frequency influence and resonant response corresponding to the fundamental frequencies of the vehicles and the bridges. The effect of local deck depressions such as potholes and unevenness at expansion joints is investigated by placing a single half sinusoidal wave at various locations along the bridge span. The analytical results show that the maximum bridge dynamic response occurs at resonant condition and local depressions have significant effect on bridge dynamic response.