Study on the Stress Histories and Fatigue Stress Spectrums of Longitudinal Connected Slab Track on Bridge During Service Life

The paper aims to study the stress histories and the fatigue stress spectrums (FSS) of longitudinal connected slab track (LCST) on the bridge during service life, and to provide an important basis for the fatigue test design of slab track (ST) in the laboratory and in situ, fatigue life prediction and fatigue designing of ST for the actual engineering. First, the temperature field model for LCST on bridge, high speed train (HST)-LCST-bridge coupling dynamic model, and LCST-bridge-piers and abutments longitudinal interaction model are established and verified. Then, based on these models, a calculation method of the FSS for the LCST on bridge under combined loads is proposed. Finally, taking the climate of the Guangzhou district in China as an example, the stress histories and FSS of LCST on a multi-span simply supported box girder bridge under combined loads are numerically simulated. The simulation results show that: (1) the stress of each component of LCST is small when considering only the vertical train load, and there will be no fatigue failure for LCST. (2) The temperature gradient load and longitudinal loads of ST significantly affect the stress distribution of LCST, so the combined effects of these loads should be considered when calculating the FSS. (3) The mechanical state of LCST is more severe around the beam end. The concrete stresses of track slab (TS) on the bottom surface and base plate (BP) on the top surface are significantly larger than the concrete stresses of TS on the top surface and BP on the bottom surface, respectively. (4) There are many peaks in the FSS of LCST on bridge under combined loads. Therefore, several probability curves should be used together to fit the FSS of LCST.