Reliability Analysis On Bearing Capacity Of Precast Concrete Structure Of Fire-damaged

With the development and progress of the times,prefabricated buildings are gradually being recognized,which have been the focus of attention of all walks of life since the “13th Five-Year Plan” in 2016.It has been widely applied due to its outstanding comprehensive performance.However,both concrete and steel bars experience a significant change on mechanical properties when exposed to fire.Furthermore,there are few studies on the related mechanical behavior and reliability of assembled structures after fire.Consequently,it is of great theoretical and practical significance to study the reliability of prefabricated concrete structures subjected to fire.In this paper,the general finite element software ABAQUS was adopted to numerically simulate the temperature field of prefabricated concrete members under ISO-834 standard temperature-rising curves.The formula for calculating the post-fired bearing capacity was deduced,and the effects of load effect ratio,fire time and other factors were considered.The computer was programmed by using MATLAB software to calculate its reliability.The main research contents and results are as follows:(1)The basic theory of reliability: center point method,JC method,Monte Carlo method,etc.,each method and its scope of use were introduced.This article used the JC method to calculate the reliability index.(2)The thermal parameters of steel bars and concrete were introduced and selected.Under the standard temperature-rising curve,the temperature field of concrete beams was simulated by ABAQUS software,and the temperature cloud diagrams obtained by the simulation were compared with the EC2 temperature cloudcharts.The results showed that the simulation results were in good agreement with the temperature cloud diagram in EC2,which verified the correctness of the simulation method.(3)The strength reduction formulas of steel bars and concrete after high temperature were introduced and selected,the temperature field of prefabricated concrete beams was simulated,and then the calculation formula of the bearing capacity of the reinforced concrete beams was deduced,which verified the formula.Based on the JC method,and considering the time of fire,load effect ratio and other factors,the reliability indexes of the post-fire concrete beams were calculated.The results showed that the reliability index of bending and shear capacity of prefabricated concrete beams was obviously reduced with the increase of the load effect ratio and the time of fire.(4)The prefabricated floor slab of which reinforced concrete slabs not extended into the bearing were tested by simulation of the temperature field,and their reliability before and after fire was analyzed.The results showed that: under normal circumstances,the prefabricated slab bottom reinforcement of fabricated concrete slab that not extended into the bearing can also meet the requirements of reliability;The reliability index of the bearing capacity of fabricated concrete slab was significantly reduced with the increase of the fire time.