| Building fires cause great harm to people's lives and property,the high temperature of fire deteriorates the reinforced concrete materials,which leads to the decrease of the safety of reinforced concrete structures.Therefore,the reinforcement of reinforced concrete members after fire has always been a hot topic in academic research.Carbon fiber reinforced plastics(CFRP)has been widely used in the reinforcement of building structures due to its excellent physical and mechanical property.In order to calculate and analyze the safety of reinforced concrete structures under fire accurately and uniformly,it is very important to study the variation law of structural reliability index under different factors.At present,there are few researches on mechanical properties and reliability analysis of reinforced concrete structures strengthened with CFRP after fire in the engineering field.In this paper,the reliability analysis of reinforced concrete beams strengthened with CFRP after fire is of great research value and practical significance.In this paper,the temperature data and bearing capacity data of the reinforced concrete beam subjected to fire were obtained by comparative test.Compared with the simulation data obtained by the finite element simulation software ABAQUS and the theoretical calculation value,it verified the correctness of finite element calculation and theoretical analysis.A new model was established and CFRP reinforcement calculation was carried out.MATLAB software was used to calculate its reliability.The effects of fire exposure time,load effect ratio and the number of CFRP reinforcement layers on the reliability of the structure were considered.The main research contents and results of this paper are as follows:(1)The basic theory of reliability: center point method,JC method,Monte Carlo method,etc.,and each method and its scope of use were introduced.This article used the Monte Carlo method to calculate the reliability index.(2)The comparative test on the bearing capacity of reinforced concrete beams after fire was carried out.Through the fire test and bearing capacity test on the specimens.ABAQUS was used to select the corresponding thermalparameters to simulate the fire and bearing capacity of the test under the international standard heating curve,and then the test data,simulation data and theoretical calculation data were compared.The correctness and feasibility of finite element calculation and theoretical analysis were verified.(3)using ABAQUS to simulate the beam subjected to fire,CFRP reinforcement was carried out on the beam subjected to fire,and the influence of load effect ratio,the time under fire and the number of layers reinforced with carbon fiber on the reliability index of beam flexural bearing capacity was studied.The data show that the reliability index of beam bending capacity decreases with the increase of load effect ratio.The reliability index of beam bending capacity decreases with the increase of fire time.With the increase of the number of CFRP reinforcement layers,the reliability index of the flexural bearing capacity of the beam increases obviously,and the reliability index of the flexural bearing capacity of the rear beams of the first and second layers in the reinforcement is significantly improved.(4)the same model was used to analyze the reliability of shear capacity of reinforced concrete beams subjected to fire.CFRP u-shaped hoop was used to reinforce the beams subjected to fire.The reliability index of shear capacity of beams gradually decreased with the increase of load effect ratio.With the increase of fire duration,the reliability index of beam shear capacity decreases gradually,and the research data shows that high temperature has a great influence on the reliability of beam shear capacity.With the increase of the number of layers strengthened by CFRP,the reliability index of shear bearing capacity of beams increases,and the reliability index of shear bearing capacity of beams strengthened by CFRP increases obviously. |
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