Experimental Study on Seismic Performance Improvement of Pile-Cap Joints in a Prestressed Concrete Solid Square Pile Using a Snap-In Mechanical Connection

Abstract

ABSTRACT To improve the seismic performance of prestressed concrete solid square piles with a snap-in mechanical connection, effects of the prestressed tension control stress of PC steel rods, anchoring method and reinforcement ratio of hot-rolled steel bars on the seismic performance of the pile-cap joints in the prestressed concrete solid square piles using a snap-in mechanical connection were investigated in this article. Considering the above-mentioned effect factors, the quasi-static test was first carried out on the cap pile-cap joint specimens. Then, the seismic performance of the specimens was investigated. The results indicated that the yield load and ultimate load changed slightly, the displacement ductility increased, the stiffness decreased and the damage development rate slowed down as the prestressed tension control value decreased. When the prestressed tension control stress was reduced to 0.4 times of the standard value of tensile strength of the PC steel rods, the crack resistance moment could meet the requirements of construction and hoisting at the same time. In the process of pile cutting and anchoring, the 135° hook treatment on the end of the PC steel rods could reduce the strength degradation of the pile-cap joints during the loading process, improve the energy-dissipation capacity and slow down the damage development rate of the pile-cap joints. For the specimens with ordinary hot-rolled deformed steel bars added to the pile end, its ductility was improved, the horizontal bearing capacity, displacement ductility and energy dissipation capacity were all greatly improved, and the damage development rate was slowed down. However, the reinforcing ratio of the ordinary hot-rolled steel bars should be kept within a reasonable range. Finally, the improvement measures were proposed to improve the mechanical properties of the prestressed concrete solid square piles and pile-cap joints.