Doctoral Dissertations

Date of Award

12-2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Civil Engineering

Major Professor

Zhongguo John Ma

Committee Members

Richard M. Bennett, David B. Clarke, Xiaopeng Zhao

Abstract

Railroad infrastructure in the United States is comprised of numerous structures that are about or over 100 years old. With railroad infrastructure aging quickly, there is a push to reuse existing substructures while replacing entire superstructures. Often these substructures are unreinforced masonry (URM) or unreinforced concrete (URC). In order for the URM or URC elements to be accepted for an extended design life, they must be evaluated for their ability to withstand seismic loading.In the U.S. railroad design code, it is hypothesized that the restraining effect of rail track structure contributes to the less damage of railroad bridge during earthquake. A structure modelling scheme for the ballast bridge and the open-deck girder bridge are proposed in SAP2000 using nonlinear link element to simulate the behavior of bearings and ballast structure under the lateral push. The experimental data from previous studies are used to calibrate and verify the proposed modelling scheme. The equivalent spring stiffness of the rail track system obtained by the modelling analysis is intended to be used in the subsequent small-scale shaking table experimental study which investigates the dynamic response of column shape rigid body specimens with spring restraint on top. Several parameters are considered in the test matrix such as stiffness of restraint spring, height/breadth ratio, ground excitations and single-body or multi-body configuration. The testing data prove the restraining effect of rail track applied on the top of the bridge piers.Coefficient of restitution is an important index to evaluate the kinetic energy loss during the impact for a rocking block. The models and expressions proposed by Housner and other researchers are reviewed comprehensively. A hypothetical model that includes three coordinated and consider the possible bouncing up scenario of the rigid block is proposed. A unified expression is developed in study.

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