Extensive forced vibration tests were conducted at the Englekirk Center site to identify the soil properties at the site, study the motion and the deformation patterns of the reaction mass, and to validate analytical and computational models of the soil and reaction mass. Two large eccentric mass shakers from the NEES @ UCLA equipment site were used for the experiments. Tests were conducted in two phases, after excavation and prior to the construction of the LHPOST reaction mass, and after the reaction mass was completed when the adjacent soil pit was empty. The dynamic response of the site was recorded at a large number of stations within the excavation and on the ground surface at distances of up to 350 m from the shake table location over a wide frequency range (0 — 25 Hz).
The LHPOST is composed of a variety of mechanical, structural, hydraulic, control, weatherproofing and safety components.