Development of Dynamic Impact Factor Expressions for Skewed Composite Concrete‐Steel Slab‐On‐Girder Bridges

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. is 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. e 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.

Dynamic Impact Factor Determination of an Existing Pre-stressed Concrete I-Girder Bridge Using Vehicle-Bridge Interaction Modelling

“…( 28) and { } is (n+4) order displacement vector consisting of modal response of bridge combined with vehicle response as shown in Eq. (29). By solving Eq.…”

“…Zhu and Law [28] also studied the continuous bridge and vehicle interaction to investigate the dynamic load effects. Mohseni et al [29] conducted an extensive numerical study to evaluate the influence of some key parameters on the dynamic impact factors for skew composite concrete-steel slab-on-girder bridges and proposed that apart from AASHTO [30] bridge design specification, all the current design specifications for considering IM are un-conservative. Pieraccini et al [31] performed an experimental study to assess the IM of a railway bridge using the interferometric radar sensor.…”

Comparison of Dynamic Amplification Factor of Deflection and Bending Moment of Highway Continuous Box-Girder Bridges by Mode Superposition

“…Similar findings were also reported by other researchers. Mohseni [ 9 ] formulated the DAFs for bending moment and deflection based on an extensive numerical study involving 125 composite slab-on-girder prototype bridges with simple support. Szurgott [ 10 ] conducted experimental tests on a reinforced concrete simply supported girder bridge and found that the DAFs derived from deflection were significantly larger and less trustworthy than those recorded from strains.…”