Research on the material properties of prestressed concrete girder bridge after exposed to fire

Abstract

The factors such as maximum temperature, duration, diffusion condition and concrete bursting at high temperature increase the difficulty of obtaining material properties by using temperature. In order to quickly obtain the real performance parameters of the materials of the pre-stressed concrete beam bridge in the post-disaster bridge evaluation, the appearance classification and material test of 32 hollow slabs demolished after the fire of the existing beam bridge in a highway were carried out. The relationship between the commonly used testing indexes and the properties of materials is obtained by measuring the properties of materials after fire. The applicability of these indexes is verified by the ultimate bearing capacity test and finite element simulation. The results show cracking and spalling of concrete at high temperature not only results in significant loss of section, but also significantly reduces the strength of concrete and prestressing steel strand in this area, which leads to the reduction of bearing capacity. When the spalling depth of concrete exceeds 2/3 of the net protective layer of steel strand after overfire, the reduction coefficient of compressive strength and tensile strength of pre-stressed steel wire reaches 0.7, which will seriously affect the ultimate bearing capacity. The normal plain round steel bar can be deviated safely to the design standard value when calculating the ultimate bearing capacity of the structure. The ultimate bearing capacity of the prestressed hollow beam after fire is analyzed by using the reduction relationship between the conventional inspection indexes and the material properties, and the finite element simulation, so as to meet the engineering precision.