Adaptive Passive Stiffness Shaping and Apparent Weakening for Seismic Protection
Satish Nagarajaiah
Professor of Civil and Mechanical Engineering
Rice University, Houston, TX
Satish.Nagarajaiah@rice.edu
Abstract
Traditionally researchers have focused on supplemental damping systems for earthquake protection. Nagarajaiah group has focused on the development of adaptive/variable stiffness systems and smart tuned mass dampers for response control. This seminar presents various stages of development of the concept of adaptive/variable stiffness structural systems. Recently NSF NEES-Adapt-Struct team with Satish Nagarajaiah as PI has focused on the development of supplemental adaptive stiffness systems for stiffness shaping in structures and apparent weakening for seismic protection. This webinar presents various stages of development of the concept of adaptive passive stiffness shaping achieved through the introduction of supplemental negative and positive tangential stiffness, and the design procedure for implementing it in various structures. The team at Rice University, University at Buffalo, RPI & UCLA funded through the NSF NEES program have developed practical and true negative stiffness system. The aim of the current project was to develop a true negative stiffness system and mimic “yielding” while retaining the main structure either in the elastic range or in the mildly inelastic range with reduced inelastic excursions—leading to a new concept called “apparent weakening”. The webinar presents the invention of the Negative Stiffness Device (NSD) and process that lead to the invention of the NSD—a creative process of 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-positive tangential stiffness which allows stiffness shaping in structures 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. (Proj. site www.ruf.rice.edu/~dsg). View videos of NEES-ADAPT(ive)-STRUCT(ures) project in YouTube RiceDSNG channel
Biography
Nagarajaiah Satish Nagarajaiah is a Professor of Civil and Mechanical Engineering at Rice University, Houston. He obtained his Ph.D. (1987-1990) from University at Buffalo, where he was a post-doctoral researcher before he started his academic career in 1993. He has published extensively and presented several keynote lectures at international conferences. For full details visit his website satishnagarajaiah.rice.edu. Dr. Nagarajaiah currently serves as the managing editor of the journal of structural engineering [ASCE], editor of the structural control and health monitoring international journal [Wiley] and editor-in-chief (North America) of the structural monitoring and maintenance international journal [Techno-press]. He is an elected inaugural fellow of Structural Engineering Institute (SEI) of ASCE since 2012. He was awarded the NSF CAREER award in 1998 for his research on Adaptive Stiffness Structures. He has founded and chaired numerous committees in SEI, EMI, and IASCM on Structural Control and Monitoring.