Study On The Residual Bearing Capacity Of Rc Column Piers Considering Concrete Bursting After Fire

Pier is an important part of the bridge substructure,which plays an important role in bearing the upper load of the bridge and transferring it to the foundation.Reinforced concrete(RC)column pier is the most common form of pier.With the rapid development of China’s transportation industry,the number of fuel and dangerous goods transportation vehicles is increasing day by day,and the resulting bridge fires are also increasing year by year.Bridge fire will bring serious economic losses,even casualties.Concrete and reinforcement will be seriously deteriorated under the action of fire and high temperature,especially when the concrete burst at high temperature,the thickness of concrete cover will be reduced,and when it is serious,the reinforcement will be directly exposed,which will aggravate the attenuation degree of bearing capacity of the pier,and seriously threaten the safety of the superstructure of the bridge.Therefore,it is very important to study the residual bearing capacity of RC column piers considering concrete bursting after fire.Based on the National Natural Science Foundation of China(51878057)and Shaanxi basic research plan of Natural Science(2018JM5018),this paper uses the ANSYS finite element program to study the residual bearing capacity of RC column piers considering concrete bursting after fire,which lays a theoretical foundation for the safety evaluation,repair and reinforcement of the bearing capacity of RC column piers after fire.The main research work is as follows:(1)The mechanical properties of concrete and reinforcement after high temperature fire are studied.According to the bursting characteristics of RC column piers after the actual fire,a "three-level index" of concrete bursting at high temperature for RC column piers is established.(2)The maximum depth of temperature conduction in the section of RC column pier is determined,and the temperature gradient of the pier section is stratified to determine the maximum temperature experienced by each layer of structure.A fire scene database is established,which is coupled with the maximum temperature,fire location and fire height.(3)Taking the RC column pier with a height of 4m and a diameter of 1.2m as the research object,the life and death element technology in ANSYS finite element software is used to control the depth of concrete burst and carry out modeling analysis.This paper analyzes the residual ultimate bearing capacity and the corresponding axial deformation of RC column piers under axial compression in different fire scenarios,and analyzes the residual ultimate bearing capacity and the corresponding lateral deflection of RC column piers under eccentric compression in different fire scenarios.The decay formula of ultimate bearing capacity of RC column piers under different fire scenarios is proposed.(4)This paper studies the evaluation of the residual bearing capacity of RC column piers after fire and the methods of repairing and strengthening.This paper puts forward the preliminary evaluation standard of RC column pier after fire,and establishes the "four level damage" index of RC column pier after fire.The reinforcement measures for RC column piers with different damage degree are put forward.