Experimental Stuady On Progressive Collapse Performance Of Prestressed RC Frame Substructure

Accidental effects such as explosions,vehicle impacts and natural disasters may cause some of the load-bearing members in the frame structure to fail and exit,thereby causing the overall progressive collapse of the structure.In recent decades,the damage of local structural members caused by accidental loads such as fires and explosions has caused the progressive collapse of the structure as a whole.Therefore,the progressive collapse resistance of the structure has been extensively studied,and its anticollapse design has gradually caused design.The attention of personnel.Prestressed RC(reinforced concrete)frame structure is widely used in largespan engineering.The load area of a single loadbearing component is large.When some loadbearing structural members fail to push out,the risk of collapse of prestressed RC frame structure is higher than that of general RC frame structure.At present,there are few experimental studies on the anticollapse performance of prestressed RC frame structures,and there is also a lack of targeted design methods.In view of the existing problems,this paper intends to study the progressive collapse performance of prestressed RC frame structures under the failure of the middle column through experiments and theoretical analysis.The main research work is as follows:(1)Six prestressed RC frame beam column structure specimens with scale ratio of 1/4 ratio were designed.The dynamic collapse performance of the structure under failure of the middle column was studied by rapid sampling test.The results show that:in the middle column in the case of sudden failure,the structural damage is mainly concentrated on the upper part of the side column beam and the lower part of the center column beam;the natural frequency of the structure is reduced,the damping ratio is increased,and the prestressing force can significantly enlarge the damping ratio of the remaining substructure,and the damping ratio is maximum.The increase to 3.86 times of the non-prestressed test piece;the maximum dynamic displacement of each substructure test piece is 1.43 times of the corresponding static displacement,and the maximum structural response acceleration is 2.875 g.(2)The static collapse test of the specimen after dynamic pumping is carried out.The research shows that the collapse process of the prestressed RC beam-column frame substructure has the working mechanism of the arch and catenary,the existence of prestress can significantly improve the structure.The ultimate capacity of the anticollapse bearing capacity,the unbonded prestressed test piece and the bonded prestressed test piece are 139.9%and 131.1%of the non-prestressed test piece S1 respectively;whether the weight is applied or the prestressing action mode is applied(If there is bonding or no bonding,it will affect the failure mode of the structure;during the collapse process,the side column is subjected to obvious horizontal load,and the maximum horizontal load reaches 61.5%of the shear capacity of the column.The frame column resists collapse of the structure.The impact of carrying capacity should be taken seriously.(3)Based on the experimental study,the anticollapse working mechanism of the prestressed RC frame during the collapse process is discussed.A simplified calculation model for the collapse resistance of unbonded prestressed RC frame structures is established.The comparison with the experimental results shows that the model can be used to predict the collapse resistance of the catenary stage structure.Finally,the anticollapse design suggestions for prestressed RC frame structures are proposed.The research results in this paper can provide reference and reference for the anticollapse design of prestressed RC frame structures.