Performance And Reliability Study On Progressive Collapse Of Precast Unbonded Prestressed Concrete Frame

Since the collapse of Ronan Point apartment in Britain in 1968,the engineering community has been studying the problem of progressive collapse for more than forty years.In 2001,the disasters of the World Trade Center(WTC)towers in New York caused enormous economic losses and political impact,which made the progressive collapse of structures attract wide attention of the society.Along with construction industrialization degree and building technical level unceasing enhancement in China,research about fabricated structure is still be in the ascendant,however,there is few research on the progressive collapse of prefabricated structures.In this article,a new type of prestressed prefabricated concrete frame joint is selected as the research object,and the reliability analysis method is used to analyze the progressive collapse resistance of precast frame structure in the case of column failure.The main research contents and results are as follows:(1)This article summarizes the research status of progressive collapse of structures,and the importance of progressive collapse resistance analysis of prefabricated frame structures and the importance of evaluating the performance of progressive collapse resistance of structures with reliability are proposed.(2)The basic information of the new kind of unbonded prestressed prefabricated concrete frame ductile joint,such as the background information,structural characteristics,size and reinforcement,and the result of experiments are introduced.On the basis of experiments,the finite element software Opensees is used to simulate the joints,the methods and processes of joint modeling are introduced,include different aspects of material constitution,fiber cross section,element type,geometric transformation etc.The results of experiment and finite element simulation are compared.(3)The pushdown experiment of cast-in-place frame structure and unbonded prestressed cast-in-place frame structure in the literature is simulated,and the results of the experiment and simulation are compared to enhance the credibility of the simulation results.Based on the joint model,the unbonded pre-stressed prefabricated frame structure model is established.The pushdown analysis of frame substructure and twospan frame structure under the failure of side columns and middle columns are carried out,and the effects of the changes of story number,story height and span on the results are studied.(4)The basic principle and calculation method of structural reliability are summarized.The random Pushdown method,which combines Monte Carlo method with Pushdown analysis method,is used.to evaluate the probability of structural anticollapse ability with the reliability calculation program based on MATLAB.Finally,the influencing factors is analyzed by tornado diagram method.