An electromagnetic horizontal impact device for centrifuge testing

The device presented herein consists of an electromagnetic horizontal impact device. The use of a steel ball serves to avoid friction of the impact mass within the guide tube, and the presence of a slight back-slope easily leads the ball back to its initial position after bouncing on the target structure. Repeated impacts can then be triggered and tuned while in-flight. The obtained impact force duration is shorter than the impact of a truck on bridge piles; however, the required level of momentum transmitted to the pile could be attained, as could the other requirements such as remote control, reproducibility and tunability. This device produces sharp impacts that enable modeling the free vibration response of structures or the impulse response in modal terms. Two applications are presented here in order to demonstrate both the versatility of the device and the types of observations it yields: a study of the inertial pile response; and a study of structure-soil-structure interactions, as part of an effort to describe the “site-city interaction”.