Engineering Seminar
Satish Nagarajaiah, Ph.D.
Professor of Civil and Mechanical Engineering
Rice University, Houston, Texas

Adaptive Stiffness and Negative Stiffness for Seismic Protection


Traditionally researchers have focused on supplemental damping systems for earthquake protection. The speaker and his coworkers have focused on the development of adaptive/variable stiffness systems for seismic protection. This talk presents various stages of development of the concept of adaptive/variable stiffness systems. Variable stiffness and adaptive pendulum tuned mass dampers developed during the course of the investigation are presented. The invention of adaptive tuned mass dampers is presented in detail resulting in real implementation.
Recently a team of researchers at Rice and University at Buffalo (along with RPI & UCLA researchers) funded through the NSF NEES program have developed practical negative stiffness systems. The talk presents the invention of the Negative Stiffness Device (NSD) and process that lead to the invention of the NSD-a creative process of invention and innovation by a team of researchers. The innovation of apparent weakening concept is presented. Detailed analytical and shake table test results are presented to show the effectiveness of the new and innovative concept of adaptive negative stiffness and apparent weakening for earthquake protection. Effectiveness of NSD in base isolated structures, inelastic single and multistory buildings, and based isolated bridges is demonstrated using experimental and analytical results obtained in the NEES-Adapt-Struct project. (project website:


Wednesday, October 10th, 2012


11:00 AM EST

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