Research on influence of cracks on bearing capacity of rectangular concrete drainage box culvert

Rectangular concrete box culvert is widely used in municipal drainage engineering, but it is easy to produce crack damage during long-term service, which leads to the degradation of structural bearing capacity. At present, there is still a lack of in-depth study on the systematic quantitative influence of cracks on the structural performance of concrete box culverts. Therefore, several groups of trilateral external load tests of rectangular concrete box culverts were carried out, and the parameters such as crack depth, number and spatial location were considered. The effects of crack characteristics on the load-bearing capacity of box culverts were systematically analyzed; meanwhile, the crack parameters were quantitatively evaluated based on the normalized sensitivity index, and an ultimate bearing capacity prediction model considering the influence of crack depth was proposed. Results indicate that the failure process of rectangular box culverts under triaxial loading conditions can be divided into crack-free initial stage, crack propagation stage and final failure stage. When the crack depth varies between 4 mm and 12 mm, the ultimate bearing capacity decreases by 4.5%~16%, and the influence of crack depth on yield load and ultimate load is significantly higher than that of crack number and spatial position. The maximum error of the established ultimate bearing capacity prediction model in the test range is only 11.93 %, indicating good accuracy. This study provides a theoretical foundation and design reference for crack damage assessment and reinforcement or repair strategies in box culvert structures.