Analysis On Progressive Collapse Of Unbounded Prestressed Fabricated Frame Construction

At present,the application of pre-stressed fabricated frame structure is gradually expanding,but the connection method and theoretical research for its structure are still insufficient.At the same time,in recent years,the collapse of assembled structures happens frequently.The research of structural anti-continuous collapse is of positive significance to structural safety and social stability.Compared with bonded pre-stressed fabricated structure,the research on unbonded pre-stressed fabricated structure is less.In this paper,the performance of unbonded pre-stressed fabricated frame structure against continuous collapse is analyzed.The main research contents are as follows:(1)In this paper,the existing collapse test in China is used as a reference.And the finite element modeling of the collapse resistance test of plane unbonded pre-stressed reinforced concrete frame structures subjected to two-storey and two-span lateral forces is carried out by SAP2000(a finite element software).The numerical simulation results are in good agreement with the experimental results,which verifies the constitutive relationship,element type and modeling analysis method adopted in this paper.(2)The non-linear static analysis method is used to analyze the continuous collapse resistance of space unbonded prestressed concrete frame structures.According to the distribution of the plastic hinge and setting the load reserve coefficient LRR as the quantitative index,the residual capacity of the remaining superstructure is the weakest after the long-side column is removed.At the same time,different parts of the structure have different mechanisms to resist continuous collapse,and there is no catenary mechanism in all parts of the structure.(3)Using the method of non-linear dynamic analysis,the normal use of space unbonded pre-stressed reinforced concrete frame structure is analyzed.The results show that the distribution of structural bending moment,shear force and axial force of the structure has changed compared with the original structure,and the residual internal force of the structure has redistributed after the failure column is removed.The change of the beam and adjacent column members connected with the failure column is particularly obvious.These beam-column members are more likely to occur chain failure,which leads to the continuous collapse of the structure.The influence of the transverse frame is larger than that of the longitudinal frame.The negative bending moment and shear increase at the end of the demolished column are obviously larger than those at the end of the demolished column.Consistent with the results of non-linear static analysis under double loads,no continuous collapse will occur in the four working conditions under normal use.When different failure columns fail,the displacement of failure points will be from small to large:internal column,short side central column,Jong side central column,corner column failure.In conclusion,the failure of corner columns and long-side columns has a significant impact on the structure s continuous collapse resistance.In design,attention should be paid to strengthening the construction of corner columns and long-side columns.The unbonded pre-stressing tendons provide load for the assembled frame structure to ensure that the structure will not collapse under normal service conditions.