Vibration Analysis of Light Rail Transit (LRT) Bridge Supported on Rocking Pier(s) and Isolated Abutments

Light rail transit (LRT) is a popular mode of transportation in modern metropolitan areas. In LRT systems, trains run on tracks over elevated guideways, streets, or combinations of both. The passengers inside the train feel vibrations due to the vibration of the train, tracks, and bridge while the train is running on the bridge/elevated guideway. In order to determine passenger comfort, vibration analysis is often required if a fundamental vertical flexural frequency of the bridge is less than 3.0–4.0 Hz (usually specified by the owner). Passenger comfort increases with decreasing vertical acceleration inside the train and vice versa. In accordance with Eurocode EN 1990:2002, Table A2.9, recommended levels of comfort (vertical accelerations) are usually followed. These levels of comfort and associated limiting values may be further defined by the owner for the individual project. Per Eurocode, vertical acceleration less than 1.0 m/s2 is very good, and more than 2.0 m/s2 is unacceptable. The vertical acceleration of the train is a function of vehicle speed, mass of the coach and bridge, and stiffness and damping of the primary and secondary springs of the coach, tracks, bridge, and soil. Therefore, train–track–bridge–soil interaction (TTBSI) analysis is required to determine the vertical acceleration of the train in other words passenger comfort. In this parametric study, a two-span LRT bridge supported on rocking pier and isolated abutments is chosen to demonstrate these interactions; however, the TTBSI analysis is applicable for any conventional bridges. This paper presents train–track–bridge–soil interaction analysis of a bridge. This study is intended to be a reference for bridge designers and owners to provide a step-by-step procedure for TTBSI analyses.