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Project Type
UTRC Research Initiative
Project Dates
01/01/2011 - 06/30/2012
Principal Investigators
Project Status

It has been observed from recent studies that vehicular impacts to highway bridges are the 3rd leading cause of collapse of highway bridges. Recent data from the Federal Highway Administration (FHWA) and other studies show that the bridge overload and lateral impact from trucks, ships and train constitute 20% of the total bridge failures. The National Highway Traffic Safety Administration (NHTSA) estimates that annually 1000 buses or trucks (10,000 pounds gross weight or greater) collide with bridge structures. The AASHTO LRFD Specifications (2007) prescribe the design of bridge piers for 400 kips of static load applied at a height of 4ft from the footing for bridge piers vulnerable to impacts. However, these specifications have been found to be insufficient in providing adequate capacity to bridge piers to sustain impact loads and don’t have a strong rational basis since 400kips load is independent of the probability of impact and shear capacity of piers. The 4 ft height from the footing is also not justified since center of gravity of cargo in trucks (that accounts for most of the weight of trucks) is usually located around 7ft from the horizontal surface in contact with wheels. The understanding the damage modes of bridge piers after the collision is crucial for the safety assessment, impact resistant design and and consequential impact on local transportation network. In order to fill the knowledge-gap identified above, main objectives of the proposed research are: (i) Developing an understanding on dynamic impacts forces as functions of truck speed and weights, equivalent static forces giving the same level of displacement as that by the dynamic forces, (ii) Establishing correlations between seismic resistance and impact forces, and investigating effectiveness of seismic rebar detailing (for bending and shear) and possible improvements so that the piers can sustain impact loads. In this research, we propose to accomplish these objectives through two tasks (Task 1: Calibration of Material Models, Task 2: Simulation of Impacts on Piers Using Calibrated Bridge Model) proposed in this research. The proposed research will increase the understanding of the bridge engineering community on the subject of impact loads on highway bridges. This is an area of national priority and will results in significant economic and societal benefits.

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