Abstract
In order to take into account the dynamic effects of moving vehicles, bridges are designed to carry static loads that are increased by dynamic impact (IFs) factors (or dynamic amplification factors) that are a function of either the span or the first flexural natural frequency of the bridge. However, this approach tends to produce very conservative designs as the IFs are calculated based on a relatively few general parameters, ignoring many significant bridge and truck dynamic characteristics. This paper presents a method for determining more realistic dynamic impact factors for skewed composite slab-on-girder bridges under AASHTO LRFD truck loading. An extensive parametric study of over 125 bridge prototypes examined key parameters, namely, the number of girders, number of lanes, skew angle, and span length. Based on the data generated by this analysis, appropriate expressions for dynamic impact factors for the longitudinal moment and deflection are proposed. In order to reduce the complexity of proposed expressions, the effects of road surface roughness on dynamic responses of bridge-vehicle interaction are considered in bridge modeling. The findings of this study are expected to help bridge engineers to design composite slab-on-girder bridges more reliably and economically and can also be used to reassess the safe live-load capacity of existing structures, potentially preventing the unnecessary posting or closing of busy highway bridges.
Highlights
Recent developments in industry have contributed to a major increase in the number and speed of vehicles, especially trucks, passing over bridges in many parts of the world
As the mode superposition method tends to underestimate the dynamic responses for grid models due to modal clustering [20], the direct integration method utilizing CSIBridge (V20) software is used for dynamic analyses of bridges. e Wilson-θ and Hilber–Hughes–Taylor operations provide the time-history responses of bridge-vehicle interactions via a direct integration technique due to its inherent stability and economy [4]
An extensive study was carried out to evaluate the influence of key parameters on the dynamic impact factors for skew composite concrete-steel slab-on-girder bridges. e resulting empirical expressions provide bending moment and deflection impact factors for the AASHTO truck-loading condition
Summary
Recent developments in industry have contributed to a major increase in the number and speed of vehicles, especially trucks, passing over bridges in many parts of the world. The types of bridge superstructures are changing and becoming more diverse Taken together, these trends have a significant impact on the dynamic responses of our bridges. E dynamic responses of a bridge under vehicle loading are a complex phenomenon because of the interaction between the bridge and the vehicle. E factors affecting the dynamic increment with respect to the static component have been recently investigated by several researchers [2, 3], and the surface roughness, vehicle characteristics, and the geometry and type of bridge were found to significantly affect the dynamic bridge-vehicle interactions. Deng and Cai [13] developed a threedimensional vehicle-bridge coupled model to simulate the bridge-vehicle interaction and determine the dynamic impact factors for composite multigirder bridges. e method relied on an iterative approach, in which the vehicle and bridge became totally uncoupled and were only linked by connect force history to predict the vehicle-induced responses of bridges [14]
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