Experimental Research On Compressive Properties Of Concrete Short Columns After High Temperature Confined By CFRP Constraints

Concrete columns are very important components in buildings,They are likely to be burned or collapsed after being attacked by super-large or large fires,But when the fire intensity is moderate,concrete columns can be repaired and reinforced after fire and put into use again.FRP is a new kind of reinforcement material,The application of FRP in the reinforcement of concrete columns after fire can obtain more advantages than traditional reinforcement methods.However,how to effectively and reliably evaluate the axial compressive behavior of concrete columns strengthened by FRP after fire is a problem that need to be solved.At present,researchers have done a lot of research on the axial compre ssive properties of concrete confined by FRP at room temperature and achieved a lot of results.However,only a few researchers have made a preliminary study on the axial compression behavior of concrete confined by FRP after high temperature.In addition,when the researchers study the mechanical properties of concrete short columns confined by FRP at room temperature,the test objects are basically plain concrete specimens,but the stirrups itself can restrain the core concrete in the actual load of concrete columns,whether or not the stirrup ratio will affect the axial compressive behavior of concrete columns confined by FRP after high temperatures is unknown.Therefore,in this paper,the axial compression tests of CFRP-confined standard size concrete cylinders are carried out around two variables: temperature and CFRP layers.At the same time,the axial compression tests of CFRP-confined standard size reinforced concrete prism short columns are carried out with temperature,CFRP layers and stirrup ratio as variables,and ABAQUS software is used to simulate the axial compression test of concrete cylinder restrained by CFRP after high temperature.The main research contents and related achievements are summarized as follows:(1)Heating and cooling of standard size C40 concrete cylinder are completed in high temperature test furnace.Axial compression tests of standard concret e cylinder restrained by CFRP after high temperature are carried out by using 3 million tons of testing machine.The effects of temperature and CFRP layers on compressive strength,initial modulus of elasticity、 ultimate strain and energy dissipation of concrete cylinder restrained by CFRP after high temperature are obtained.Combining the test results with the existing calculation models,a calculation model for the compressive strength of concrete cylinders con fined by CFRP after high temperature is obtained.The model agrees well with the test results.(2)Heating and cooling of standard size reinforced concrete prism short columns are completed in high temperature test furnace.Axial compression tests of standard reinforced concrete prism short columns restrain ed by CFRP after high temperature are carried out by using 3 million tons of testing machine.The effects of temperature,CFRP layers and stirrup ratio on the bearing capacity,axial compression stiffness and ductility of reinforced concrete prism short columns are obtained.(3)The temperature field of concrete cylinder and the axial compression test of concrete cylinder confined by CFRP after high temperature are simulated by ABAQUS.By comparing the experimental results with the simulation results,the feasibility of the finite element analysis method in this paper is verified.