Abstract
The dynamic Impact Factor (IM) of a bridge is influenced by many factors, including Vehicle-Bridge Interaction (VBI), vehicle speed and road roughness. This paper represents the dynamic effects of moving vehicles and the determination of IM of an existing Pre-stressed concrete I-girder bridge utilizing VBI modeling. Evaluation of the IM is expected to provide valuable information for condition assessment and management of the existing bridge. The interaction problem between the vehicle and the bridge includes a dynamic model for the bridge structure subsystem, a dynamic model for the vehicle subsystem, interaction constraints, road roughness modelling and numerical solution techniques for the dynamic systems. The Half-car model is utilized for modelling of the vehicle dynamics and the bridge dynamic model is idealized according to Finite Element Method (FEM). Then FEM along with the mode superposition method are utilized for determining the Equation of Motion (EOM) for the bridge subsystem. D’Alembert’s principle is used for developing EOM for the vehicle subsystem. The interaction between vehicle vibration and bridge vibration is established through the contact forces between the wheels and the bridge by employing the compatibility relationship between the contact points and by applying the static equilibrium condition. Lastly, Newmark’s-β method is used for solving the coupled mathematical model of the vehicle and bridge interaction problem to determine the responses of the two sub-systems. The whole procedure is then performed for different vehicle speeds and various bridge deck surface roughness conditions to determine the dynamic impact on the existing I-girder bridge named Teesta Bridge located in Bangladesh.
Highlights
In the last years, the ever-growing span length of bridges and the increase of vehicle loads and vehicle speeds have led to the consequent increase in dynamic influence on bridge structures [1]
This phenomenon is known as Dynamic Impact on bridges which is generally considered as Impact Factor (IM) or Dynamic load allowance (DLA) in the bridge design standards
This study describes the amplification of the contact point forces on the bridge due to Vehicle-Bridge Interactions (VBI) with respect to static vehicle loading
Summary
The ever-growing span length of bridges and the increase of vehicle loads and vehicle speeds have led to the consequent increase in dynamic influence on bridge structures [1]. The dynamic effects produced by vehicles passing over the bridge structures and viaducts result in the increase of dynamic forces and displacements over that of the static responses [2] This phenomenon is known as Dynamic Impact on bridges which is generally considered as Impact Factor (IM) or Dynamic load allowance (DLA) in the bridge design standards. 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. The dynamic behavior of an existing Pre-stressed concrete (PC) I-girder bridge structures under moving vehicle is investigated numerically considering all the complex factors mentioned above and the dynamic impact factor is determined.
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