Seismic performance of prestressed concrete solid square piles reinforced with an additional built-in reinforcement cage

The helical grooved steel bars (HGBs) are commonly used as the prestressing tendons in the prestressed concrete solid square piles (PSPs). Due to the insufficient tensile elongation capacity of the HGBs, the PSPs under lateral loads are prone to the brittle failure due to the premature tensile fracture of the HGBs. In this paper, the PSPs additionally reinforced with a built-in reinforcement cage using the deformed rebars, herein referred as PSPRs, have been developed to improve the seismic performances. Three full-scale PSPR specimens were tested under quasi-static cyclic loading to evaluate the effects of the additional reinforcement cage on the seismic behavior of PSPs, and a comparison is also conducted to previous experimental results of the counterpart PSPs. The flexural bearing capacity of PSPRs including cracking, yield and peak moments is theoretically analyzed. Dedicated finite element (FE) models of PSPR specimens are developed using the software DIANA and verified against the test results. Then, the validated FE model is used to conduct the parameter analysis. The findings show that the additional reinforcement cage can markedly ameliorate the evolution and distribution of the pile body concrete cracks, and significantly delays the premature rupture of HGBs at the main cracks, resulting in a significant increase in flexural bearing and deformation capacity of PSPs especially under lower axial force ratios. Furthermore, the additional reinforcement cage also improves the hysteretic behavior and energy dissipation capacity of PSPs. Under higher axial force ratios, increasing prestressing tendon ratios and concrete strength can remarkably improve the flexural bearing capacity of PSPRs, but slightly reduce the deformability and ductility.