NEESR-II: Advanced Site Monitoring and Effective Characterization of Site Nonlinear Dynamic Properties and Model Calibration

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

This award is an outcome of the NSF 08-519 program solicitation George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)competition and includes Rensselaer Polytechnic Institute (lead institution) and Manhattan College (subaward). This project will utilize the NEES equipment sites at the University of California at Santa Barbara, the University of Texas at Austin and Rensselaer Polytechnic Institute. Site liquefaction during earthquake excitations is often associated with significant permanent displacement and lateral spreading that lead to costly damage to civil systems of all types. However, realtime field measurements of permanent displacements have eluded researcher and practitioners until recently, and hindered the development of reliable tools to predict site lateral spreading and failure. This project proposes a research program to develop a capability to monitor the cyclic and permanent displacement of field sites and use the associated measurements to characterize the in situ low and large strain dynamic properties for soil strata ranging from the ground surface to a depth of about 30 meters. A number of wireless shape-acceleration arrays (WSSA) will be installed permanently at the NEES@UCSB Wildlife liquefaction site to monitor low strain response as well as earthquake induced liquefaction, permanent deformation and lateral spreading. It is anticipated that an earthquake in the near future will induce large permanent deformation at this site. The installed arrays would then provide for the first time measurement of the time history of a site lateral spreading profile. Specifically, this project comprises the following tasks: (1) development and validation of optimal array configurations using centrifuge model tests and computational analyses, (2) installation of a number of wireless shape-acceleration arrays within an optimal configuration at the NEES@UCSB Wildlife liquefaction site, (3) excitation of the site using the NEES@Texas T-Rex vibrator, and (4) development of innovative data reduction and identification tools to estimate the 3-dimensional (small and large strain) dynamic properties and response mechanisms of the Wildlife site as well as other field sites that may be instrumented in the future. This project will have a broad impact on our capabilities to test in situ soil systems, evaluate their (low and large strain) mechanical properties and calibrate computational models of these systems, all while avoiding the issues of soil sample disturbance and limitation of small scale or sample testing. The outcome of the planned research will contribute to the development of more robust modeling procedures and predictive tools of soil systems to reduce losses associated with earthquakes. The proposed curriculum development at Rensselaer and Manhattan College will accelerate and enhance the emerging new paradigm in engineering education where hands-on experience is one of the catalysts for effective transmission of knowledge. Data from this project will be made available through the NEES data repository (http://www.nees.org).