Study On Compression Performance Of Reinforced Concrete Columns After Fire And Wrapped With Thin-wall Steel Tube

At present, the research results of the technology and design method for the reinforcement and reconstruction of the reinforced concrete structure after fire are relatively few. The outsourcing of thin-walled steel tube, filling self leveling micro expansion grouting material reinforcement after fire concrete columns, steel tube as the grouting material template with, and the steel tube is not easy to appear local buckling, old and new material cowork performance is good. It can obviously improved after fire concrete column bearing capacity and stiffness and other advantages. In this paper, the experimental study on the axial compression test of the concrete column strengthened by the thin wall steel tube after high temperature is carried out. Specific work and main conclusions are as follows:The 37 after external thin-walled steel, sandwich filled with grouting material at high temperature under restraint of concrete prism under axial compression test is carried out. The shape and thickness of the outsourcing of thin-walled steel tube of different burned temperature of concrete confined should the influence law of the curve of stress-strain and the expression of the curve are analyzed. Test results show that:(1) concrete core subjected to temperature less than 200℃, wall thickness limit of concrete-filled square steel tube bearing capacity has little effect, the core concrete subjected to temperature greater than 200℃, with the wall thickness increase the limit bearing capacity is increased 4.73%~11.7%, but deformation ability with the wall thickness increased with the increase 55.4%~265.5%; ultimate bearing capacity of circular steel tubes with the wall thickness increases with increasing 11.6%~24.5% deformation ability with the wall thickness increases with increasing 34.9%~171.8%. Round steel pipe of the ultimate bearing capacity and deformation is much higher than that of square steel tube;(2) square steel tube reinforced specimens, with the increase of core concrete subjected to temperature, ultimate bearing capacity decreased 4.5%~19.4%, but deformation capacity to improve the 15.7%~59.3%; round steel pipe reinforcement specimens. With the increase of core concrete subjected to temperature, limit bearing force decreased 0.98%~12%, but deformation ability improve 28.2%~62.0%;(3) steel pipe reinforcement specimens, the ascent of core concrete stiffness with concrete under elevated temperature in fire and reduce, after reaching the peak stress test pieces fall into the descending speed with steel tube wall thickness increase and is slow. The shape of steel tube has little influence on the stress-strain relationship of core concrete.The 10 epiboly thin-wall steel tube strengthened after fire reinforced concrete column subjected to eccentric compression test, analysis of the different eccentric rate of outsourcing thin-walled steel reinforcement after fire reinforced concrete columns subjected to eccentric load bearing force was studied. The experimental results show that:(1) outsourcing thin-wall steel tube under fire after the bending of reinforced concrete column stiffness, the eccentric bearing force increased significantly strengthened, bearing capacity of eccentrically loaded without fire can be restored to;(2) package thin-walled steel capacity of the bias of the reinforced concrete columns strengthened after the fire, with the increase of eccentricity decreases 10.2%~52.3%.