Damage Mechanism of Broad-narrow Joint of CRTSII Slab Track under Temperature Rise

There is two typical damage pattern at broad-narrow joint of CRTSII slab track breakage of narrow joint and fracture at junction between broad joint and narrow joint. This paper aims to study the damage mechanism and develop of broad-narrow joint of CRTSII slab track and put forward the methods to reduce the damage. Based on damaged plasticity model for concrete and cohesive zone model, the damage mechanism and development process of broad-narrow joint are analyzed in this study. The unequal width of broad joint and narrow joint, different concrete strength between broad-narrow joints and slab and slab integrity reducing due to the interface are the main reason for the typical damage. It is suggested to set the same width of broad joint and narrow joint, set the same strength of broad-narrow joint and slab and enhance the integrity of the slab by chipping or adding adhesives, among which the former two methods are more effective. Breakage of narrow joint is a gradual compression damage due to the lower concrete strength than slab. Fracture at the junction between narrow joint and broad joint is a mutational tension damage due to the unequal width of broad joint and narrow joint. The temperature gradient has significant effect on the compression damage, but small to the tension damage, it has the risk of complete destruction under extreme conditions.