Seismic Performance Analysis Of Unbonded Prestressed Precast Frame Structure

The unbonded prestressed prefabricated frame structures use high-strength prestressed reinforcement to connect precast beams and columns into a framework in construction site,which have efficient construction,low labor costs,reliable quality and so on.Building industrialization is a significant way to realize the sustainable development strategy of our country,so there will be broad development prospect for unbonded prestressed prefabricated frame structures in the construction market.But now,the researches on this frame structure mainly focuses on connection members,and the study about the seismic performance of the frame structure is insufficient.This paper firstly uses Open SEES software to establish finite element model about the unbonded prestressed prefabricated structures.After verifying the availability of the model,the paper designs one ordinary reinforced concrete frame(RC frame)and 8unbonded prestressed prefabricated fame structures which has three-storey and two-span in zone of earthquake intensity 8(0.3g)according to requirements of the code.Then,the paper explores the effects of main parameters on the behaviors of the unbonded prestressed prefabricated structures by static hysteretic loading,and studies the differences of seismic performance about two different frame structures by dynamic time history analysis.Through comparing seismic perform the unbonded prestressed prefabricated fames which has three-storey and two-span,with RC frame,this paper draws the following conclusions:(1)when the bearing capacity of the beams and columns of the unbonded prestressed fabricated frame is same as the RC frame,its displacement-load hysteretic curve is not as full as the cast-in-place frame,the peak bearing capacity is about 90% of the RC frame,and the cumulative energy consumption and equivalent viscous damping coefficient are about 55% and 65% of the RC frame.Meanwhile,the skeleton curve’s initial stiffness of the unbonded prestressed fabricated frame is larger than the RC frame,reaching the yield,reaching the yield,peak point and ultimate failure earlier,and has smaller residual deformation of the structure and the better displacement ductility.(2)With changing the prestressed reinforcement ratio and the initial prestressing force,the unbonded prestressed fabricated frames remaining the same bearing capacity of beam do have the indifferent structural seismic performance.When the unbonded prestressed fabricated frames keep the same prestressed reinforcement ratio,the smaller the initial prestressing force is,the smaller the initial stiffness is and the smaller the peak bearing capacity is,but there is no significant difference in displacement ductility,cumulative energy dissipation capacity and equivalent viscous damping coefficient.(3)Under the frequent earthquakes,the maximum displacement of the unbonded prestressed precast frame’s top floor is about 7.6% smaller than the RC frame,and its maximum bottom shearing force is about 28% larger than the RC frame,which indicates that the initial stiffness of this kind of precast frame structure is obviously larger than RC frame structure because of the preloading created by the prestressed reinforcement.At the same time,the maximum story drift of the unbonded prestressed precast frame is smaller than the RC frame,and both of them can satisfy the requirements of the elastic story drift limit in the code of China.(4)Under the rare earthquakes,the maximum floor displacement and bottom shearing force of the unbonded prestressed precast frame are little smaller than the RC frame structure.The maximum story drift can also satisfy the requirements of China’s code,and the residual deformation is smaller and the recoverable capability is better.Compared with the RC structure,its beams’ damage is worse,but the damage of the column is slighter,which is helpful to prevent the structural collapse.