Study On Collapse Performance Of Prestressed Concrete Frame Strtcture

Explosion,fire,impact and earthquake can cause progressive collapse.Once progressive collapse occurs,it will cause serious economic losses and casualties.Prestressed concrete frame structure members bear a large load,so the risk of progressive collapse of prestressed concrete frame structure is higher than that of RC frame structure.Therefore,it is of great significance to study the progressive collapse behavior and collapse mechanism of prestressed concrete frame.In this paper,the finite element software ABAQUS is used to establish models to analyze the collapse resistance of prestressed concrete frame structure in the case of failure of the middle column.The research contents are as follows:(1)In this paper,13 models of bonded prestressed concrete frame structure are established,and the influence of different parameters such as span-depth ratio and reinforcement ratio of beam on the collapse performance of bonded prestressed concrete frame structure is analysed.The analysis shows that: span-depth ratio,reinforcement ratio of beam,concrete strength,prestressing action and the diameter of prestressed reinforcement have significant influence,while column section and controll stress for tensioning have little influence.(2)In this paper,14 models of unbonded prestressed concrete frame structure are established,and the effects of different parameters such as span to height and concrete strength on the collapse performance of unbonded prestressed concrete frame structure are analysed.The analysis shows that the most significant parameters affecting the peak bearing capacity of compressive arch action are span to height and concrete strength;the most significant parameters affecting the ultimate bearing capacity of catenary mechanism are span to height、 reinforcement ratio of beam、concrete strength and prestressed reinforcement diameter.(3)On the basis of calculation and analysis,the collapse performance of bonded and unbonded prestressed concrete frame is compared.The research shows that:(1)the loading phases and failure mode of bonded and unbonded prestressed concrete frame are similar.The loading phases of prestressed concrete frame in the collapse simulation process can be divided into elastic stage,arching effect stage and catenary mechanism stage.(2)The effect of unbonded prestressing is better than that of bonded prestressing.The ultimate bearing capacity of bonded and unbonded prestressed concrete frame specimen is 149.5% and 154.7%of that of non prestressed specimens respectively.(3)The ratio of the ultimate bearing capacity of catenary stage to the peak bearing capacity of arch compression effect can be used as an index to evaluate the action of catenary.The ratio of bonded prestressed concrete frameis between 2.90 and 4.35,and that of unbonded prestressed concrete frame is between 2.65 and 4.87.It is shown that the ultimate bearing capacity of prestressed concrete frame structure can be significantly increased by considering the effect of catenary.(4)In this paper,the range of DIF value is discussed.DIF calculated by the calculation model based on energy method is mainly distributed between 1.70 and 1.90.This study can provide reference and basis for the collapse resistance design and calculation of prestressed concrete frame structure.