Research On Method Of Probabilistic Progressive Collapse Analysis Of RC Frame Structures Against Blast Loads In Life-cycle

At present,deterministic methods are adopted for the anti-blast and antiprogressive collapse design of building structures.However,whether it is an accidental explosion or a terrorist blast,the explosion load acting on the building structure has great uncertainty.At the same time,the strength of the material and the resistance of the structure are also uncertain and will degrade over time during the entire Life-Cycle of the building structure.Therefore,considering the uncertainty of explosion load and structural resistance,as well as the degradation of material strength and structural resistance,the reliability analysis of progressive collapse resistance of a building structure under blast load over its entire Life-Cycle is of great significance for its design.In this paper,the RC frame structure is taken as the research object,and the resistance model of RC members in the Life-Cycle is established.The reliability of the RC column failure and the progressive collapse resistance of the frame structure and its degradation law over time under different explosion conditions during the Life-Cycle are analyzed.A reliability analysis method for the progressive collapse resistance of a RC frame structure over the Life-Cycle is proposed.The main research work and results are as follows:(1)Based on the existing research results on the durability of RC,a more accurate formula for calculating the yield strength coefficient of reinforcement was proposed,and a resistance degradation model of RC members based on the corrosion rate of reinforcement was established.Further analysis of the parameters reveals the degradation law of the resistance of RC members with the corrosion rate of the reinforcement.The results show that the resistance of the members can be a threedimensional linear curve with the increase of the corrosion rate,and the inflection points are the corrosion rate when concrete cracks and critical rust rate(1.2/d).(2)Based on the subset simulation method,by introducing the resistance degradation model of RC members in the damage probability analysis of RC columns under blast loads,a damage probability analysis method of RC columns under blast load during the Life-Cycle was established,and the change law of damage probability of RC columns with time was revealed.The factors affecting the failure probability of RC columns are further studied,and the calculation formula of the failure probability of the RC columns under the blast load based on the initial failure probability is proposed,and the correctness of the formula is verified.(3)Combined with the subset simulation method,an energy-based progressive collapse probability assessment method for RC frame structures is proposed,and the reliability degradation model of RC members is further combined to establish a reliability analysis method of the progressive collapse resistance of the RC frame structure over its Life-Cycle.The progressive collapse probability of RC frame structures under different explosive conditions during the Life-Cycle is analyzed.The results show that when the corrosion rate of the reinforcement is between the concrete cracking corrosion rate and the critical corrosion rate(1.2/d),the probability of progressive collapse of the structure under blast load is in a period of rapid growth.