Experimental Study on Fracture Behavior of RC Piles and Superstructure Dynamic Response Using Centrifuge Model

In past earthquake disasters, many pile foundations of building were damaged. Although many researchers have examined the relationships related to soilpile-superstructure interaction, few studies have been conducted to examine the damage of piles based on experiment. This study investigated the relationship between the pile fracture and dynamic response of a superstructure when the footing is embedded. Also, we tried evaluating the ultimate shear strength of a pile foundation when the pile was shear fractured. The shaking table test under a centrifuge field was conducted to investigate the behavior of the RC pile foundation. The diameter of the pile model is 25mm (1.25m in prototype scale). This pile model consists of mortar, four main reinforcement bars and a hoop reinforcement bar. The experimental model was set in a laminar shear box filled with Toyoura dry sand. The density of the soil was 60%. In the shaking table test, 11 different amplitude Rinkai waves were input under a 50G field. In the result of the experiment, the heads of the pile models were shear fractured. It caused the reduction of vibration transmissibility between the superstructure and the ground surface. The maximum inertial force of the superstructure mostly corresponded to the total value of the ultimate shear strength calculated using the shear strength of the pile model, the coefficient of pile group effect, and the resistance force of footing.