Performance Analysis On Progressive Collapse-resistance Behavior Of External Prestressed RC Frames

How to effectively prevent the continuous destructive collapse of the building structure has been a hot issue in the engineering field,since the gas explosion in the Ronan Point apartment in the United Kingdom in 1968 caused the progressive collapse of the structure.In recent years,many scholars around the world are getting more and more research on structural collapse resistance.The use of prestressing techniques to reinforce structures has been widely recognized.Prestressing is used to strengthen the structure's ability to resist progressive collapse has a bright future.In this paper,the simulation analysis of the external prestressed reinforced concrete frame structure was carried out under the support of the National Natural Science Foundation of China(No.51308556).The main research contents are as follows:1.Based on the test results of the five-dimensional external prestressed reinforced concrete frame carried out by the research group,a finite element model was established,the model parameters were set reasonably,and the analytical results were in good agreement with the experimental results.2.Based on the finite element model,four parameters of frame height,internal longitudinal reinforcement ratio,external prestressed tendon area and initial tensile stress ratio of external prestressed tendons were analyzed.The results show that increasing the beam height will significantly improve the ultimate bearing capacity of the beam during the mechanism stage;increasing the longitudinal reinforcement ratio of the frame beam will lag the beam mechanism-suspension mechanism transition point and reduce the bearing capacity of the external prestressing tendon to the frame structure.Contribution rate;the area of external prestressed tendons is positively correlated with the collapse bearing capacity of the catenary mechanism stage;and with the increase of the initial tensile stress ratio of the external tendons,the collapse bearing capacity of the catenary mechanism stage is significantly increased.The beam mechanism-the catenary mechanism transition point is postponed,and the contribution of the external prestressing tendon to the collapse capacity of the frame is greater.3.A simplified calculation formula for the ultimate bearing capacity of the beam mechanism based on the verification of the normal section bending capacity and the deformation coordination formula is proposed.Based on the mathematical expression of the catenary,a simplified calculation formula for the ultimate bearing capacity of the catenary mechanism is proposed.The results verify the reliability of the calculation formula.4.Using the theoretical calculation formula to analyze the four groups of parameters,and explore the influence of the parameter combination on the collapse of the frame.5.The finite element analysis of the multi-layer external prestressed reinforced concrete plane frame and the single layer external prestressed space frame against progressive collapse is carried out,and the ultimate bearing capacity of the collapse is evaluated.The reinforcement effect of the stressing device is verified.6.Based on the results of the tests and finite element analysis,several design suggestions against progressive collapse are given in combination with engineering application.