Forced Vibration Tests of the Foundation and Surrounding Soil at the NEES Large High Performance Shake Table

University Of California-San Diego, La Jolla CA

Investigators

Abstract

This action is to support forced vibration tests of the reinforced concrete foundation block and of the soils in the vicinity of the National Earthquake Engineering Simulation (NEES) Large High-Performance Shake Table at Camp Elliott, University of California-San Diego. The objective is to obtain fundamental information on the concept of using soil stiffness and radiation damping to reduce the necessity for extremely massive and deeply embedded foundations to resist dynamic and static loading. The tests will be conducted upon completion of the excavation for the foundation and the adjacent soil pits, and again, after completion of the reinforced concrete foundation block. This will be done in collaboration with researchers associated with the NEES Field Testing Facility at UCLA and with the Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (CICESE), Ensenada, Mexico. In the initial tests, eccentric mass shakers will be placed at the bottom of the excavations for the foundation block of the shake table and for the foundation of the adjacent equipment building. Measurements will be made of the dynamic response at dense arrays on the cavities for the foundations, on the adjacent soil pit and on the ground surface up to a distance of 200 meters. The tests will be repeated after the foundation block for the shake table and the foundation for the equipment building have been completed. The first objective of the project is to take advantage of limited time-windows to obtain dynamic ground motion data and, by inference, geotechnical data to be used in the development of a virtual model of the complete NEES Large High-Performance Shake Table facility at Camp Elliott. The second objective is to validate a new design approach for foundations subjected to impact loads that use soil stiffness and radiation damping to substitute for part of the foundation block, leading to a more economical installation. If fully validated, this approach, which takes advantage of advances in analysis of dynamic soil-foundation interaction, will result in significant savings. The project will play an important role in efforts to model the seismic and vibration response of structures in dense urban environments. The project will provide a unique training opportunity for undergraduate and graduate. students, will be useful in integrating the results of research into undergraduate and graduate courses on geotechnical and earthquake engineering, and will test the tele-observation capabilities from the UCSD NEES site at Camp Elliott.