Experimental investigation of simply-supported post-tensioned beam after anchorage system failure

Abstract

In recent years, with the rapid development of China's transportation industry, some existing bridges have needed to be demolished and rebuilt. Bridge demolition is a complex process of structural system conversions. During demolition, the prestressed beam performance is not clear after anchorage system failure. Therefore, it is important to carry out research to better understand the behaviour of post-tensioned prestressed concrete members after anchorage failure. In this paper, the demolition project of the Qingkou interchange ramp bridge of the Fuzhou circumferential highway is taken as research background to carry out an experimental investigation on post-tensioned prestressed concrete beam specimens to study their mechanical performance before and after the failure of the anchorage system. The results show that the anchorage has a longitudinal extrusion effect on the concrete, and the contribution of the concrete and the rebar to the structure decreases from the end to the mid-span of the beams. The failure of the anchorage system affects the cracking load, the crack width and the ultimate bearing capacity, while it has no effect on the final crack distribution and the concrete failure mode. Beyond the limit of elasticity, the prestressing tendons and the concrete grout start to debond, and the bearing capacity of the beam decreases gradually. The crack resistance and the ductility of the prestressed concrete beams are also reduced. After concrete cracking and under the same load condition, the prestressing tendons bear a larger load in the case of anchorage system failure. It is suggested that after the failure of the anchorage system, the contribution of the residual stress in the prestressing tendons to the bearing capacity of the structure be taken into account until the limit of elasticity of the structure is reached.