Experimental And Theoretical Study Of Fire And Strengthening Of Reinforced Concrete Beams

Based on the previous work, this issue tried to establish a relatively complete experimental and theoretical framework on the behavious of simply-supported beams under fire, fire disaster assessment and reinforcement after fire. The main content include :(1) By collecting and collating fire documents obtained by foreign and native researchers , thermal and mechanical properties at high temperature of steel and concrete are summarized and concluded .(2) By the experiment on the three full-scale simply-supported beams under fire , we analysis the temperature field of beam section, deflection ,and the crack characteristics .We examine the influence of reinforcement ratio on the fire-resistant properties and come to raise that increasing the reinforcement ratio can improving fire-resistant properties(3) The basic theories on fire damage assessment of reinforced concrete structures are summarized , and a new method to calculate the residual bearing capacity is put forward.(4)We assess the damage of beams after fire and speculate the loss of concrete strength by rebound method and coring method. We measured the residual strength of steel after fire and obtained that after cooling the strength of steel decrease very little and you can take the simple temperature strength instead for it.(5)An experiment of two beams strengthened by CFRP (carbon fiber reinforced polymer) and one common beam for comparison is test to observe and compare the whole failure process. The results are analyzed. It is found that RC beams strengthened with CFRP can considerably increase the ultimate strength and the stiffness after the steel has yielded and it can limit the further development of the cracks of beams and improving the damage characteristics of beams .(6) Proposed a method to calculate the ultimate bearing capacity of reinforced concrete beams after fire which are strengthened by CFRP. The ultimate bearing capacity of Beams in this experiment at simple temperature, after high temperature and reinforced by CFRP is analyzed and compared. Obtain that for RC beams after fire damage strengthening with CFRP is an available method.