LOAD RESISTING MECHANISM OF PRECAST STRUCTURE UNDER EXTERIOR COLUMN FAILURE

In order to study the anti-continuous collapse mechanism of an unbonded post-tensioning precast structure with prestressed spliced connections under the condition of side column failure, four one-half scaled precast beam-column substructures were tested in the laboratory. The performance of three types of precast beam-column connections are investigated by using a pushdown loading approach. The test results demonstrated that different connection types exhibit different failure modes. The installation of unbonded post-tensioning connections is an effective way to resist the progressive collapse of precast concrete frames. The hybrid connection achieved greater load resistance than the summation of the load resistance of the unbonded post-tensioning connection and steel angle connection individually. Higher effective prestress in unbonded post-tensioning tendons could increase the load resistance in a relatively small deformation stage. However, the higher effective prestress may decrease the ultimate load capacity of the frame at a large deformation stage. Finally, high-fidelity finite element models, which were relied on commercial software ANSYS/LSDYNA, were developed. After validation, the results, which could not be measured during tests, were presented and discussed. Then, parametric studies were carried out based on the validated models. The numerical results showed that bonded post-tensioning tendons could increase the resistance of the specimen with unbounded post-tensioning tendons. Increasing the concrete strength could also increase the load resistance significantly. However, higher axial compressive forces at side columns will aggregate the P-Δ effects, which leads to lower deformation capacity and ultimate load resistance capacity.