Experimental Study On Mechanical Properties Of Simply Supported Reinforced Concrete Beams After-fire

With the rapid growth of freeway mileage,there are more and more traffic accidents caused by car collision every year.In these traffic accidents,the leakage of inflammable and explosive materials carried by vehicles and other factors often lead to fire,which poses a great threat to the safety of bridges and other concrete structures in the accident place.Therefore,it is important to study the mechanical properties of reinforced concrete structure after fire.Firstly,the after fire research literature of concrete bridges and other fire accidents of concrete structures at home and abroad are classified and summarized,the fire resistance of reinforced concrete structure and the influence factors of high temperature of steel and concrete materials in the process of fire are analyzed,secondly,the thermal parameters of materials specified in different documents and national codes are compared and analyzed,which provides data basis for the numerical simulation.Carry out a fire test of reinforced concrete beams,and make four full-scale simple-supported beam members with a cross-section size of 400mm×600mm and a length of 6.4m.Firstly,different after fire conditions are set up to heat three beams respectively,and the temperature field distribution and mechanical property change of concrete test beams under different conditions are studied.Then,numerical simulation based on ABAQUS software.The main research contents and results are as follows:(1)High-temperature heating test on concrete beams,the temperature change data at different heights inside the beam were measured and fitting analysis of the measured temperature data shows the variation of temperature field.(2)After the heating was completed,the four test beams were subjected to static load test,and the relationship between load-deflection and load-crack of the four test beams was studied during the loading test.The results showed that the crack spacing of the beam after over-fire was larger than that of normal state,mainly due to material performance degradation.(3)The applicability of the existing calculation methods for bearing capacity of several concrete structures after fire is analyzed.Finally,based on the actual conditions of test data,a stratified calculation method is proposed for the calculation of concrete strength reduction.(4)The ABAQUS finite element analysis software is used to build a reinforced concrete simply-supported beam for over-fire simulation.The temperature field and mechanical properties of the simply-supported concrete beam after high temperature are analyzed,and a comparative study with the existing test data proves that Correctness.