A Study of Compressive Stress and Compression of Hard Foam Board for Longitudinally Coupled Slab Track on Bridges

Abstract

Longitudinally Coupled Prefabricated Ballastless Track (LCPBT) system was firstly applied on Suining-Chongqing experimental railway line and Beijing-Tianjin intercity railway line. LCPBT track structure is longitudinally continuous, with fixing a 5-cm-thick hard foam board above every bridge structure joints, between bridge protection layer and the continuous concrete base to reduce detrimental fastening pulling force in case of great rotation angle or displacement. Hard foam board ensures a steady deformation transition, and we calculate its compressive stress, compression and cubical elasticity coefficient Q, for fulfilling force-bearing and deformation requirements. Taking a two-span, simple supported beam, each with 32-m-long bridge for instance, an integral finite element model of continuous welded rail -coupled track slab -coupled concrete base –bridge beam was established, in which a vertical compression amount under 9 different load cases. The maximum bottom tensile stress of concrete base, maximum compressive stress and compression amount of hard foam board are gained from computation results. Besides, Q-value and the control value of rotation angle at bridge structure joints are suggested in this paper. The key findings are: a) under simultaneous actions of train load and beam rotation angle, the maximum bottom tensile stress of concrete base does not exceed its threshold as 250 kPa, given a Q-value of 0.5 N/mm3; b) considering the uniformity of track stiffness and track regularity, a greater Q-value is preferable and we recommend the Q-value as 0.5 N/mm3; c) the beam rotation angle at bridge structure joints should be less than 1.4, including the load cause of uneven settlement of adjacent bridge piers, uneven settlement of adjacent bridge foundation; d) uneven settlement of adjacent bridge foundation on the same bridge pier must be strictly controlled to avoid affecting the service life of hard foam board.