Novel Negative Stiffness Device- Concept, Development and Application

主讲人：Satish Nagarajaiah，Professor of Civil and Mechanical  Engineering ，Rice  University, Dept. of Civil and Enviroment Engineering, Houston, Texas,  USA

讲座时间：9月2日（周五）下午15:30

讲座地点：系楼5楼会议室

Abstract

Devices with displacement  dependent stiffness have been explored for vibration isolations. In this seminar  a new negative stiffness device (NSD) that can consists of pre-compressed  springs and can be shaped as a function of displacement by curved templates is  presented. The proposed NSD is made up of a compressed springs attached to  rollers, rolling along curved templates that allow adapting the stiffness as a  predetermined function of displacement. The NSD configuration is presented in  detail, an analytical model is developed and validated using test results. The  NSD is tested under harmonic motion to determine its force displacement behavior  and then it is connected to a single degree of freedom (SDOF) system with an  additional spring with positive stiffness, on a shaking table to determine its  vibration characteristics. The combination of the NSD and the positive spring  results in a composite nonlinear elastic spring with an initial softening  behavior followed by hardening behavior. Frequency response curves obtained from  test results are presented to demonstrate the initial softening followed by  hardening is presented. The new NSD can be used for vibration isolation studies  in future studies.

Bio-sketch

Satish Nagarajaiah is a Professor of Civil and Mechanical  Engineering, at Rice University, Houston, Texas, USA. Dr. Nagarajaiah expertise  is in Advanced Protective Systems (Seismic Isolation, Tuned Mass Dampers etc.),  Structural Dynamic Systems, Structural Control, Structural Modeling, Structural  Identification, and Sensing using Applied Nanotechnology. His research is funded  by the NSF, NASA, DOE, Air Force Office of Scientific Research, Office of Naval  Research, other State, Federal, Private Agencies and Industries. National  Science Foundation has recognized his contributions to adaptive stiffness  structural systems by awarding the prestigious NSF CAREER award in 1998 and  awarded a large ($1.6M) NSF project with five universities and multiple  investigators in which he and his team invented/developed a new adaptive  negative stiffness (patented) structural system that significantly enhances  protection of buildings and bridges. He and his team received the 2015 ASCE  Moissieff Award for their research on innovative adaptive negative stiffness  structures. Dr. Nagarajaiah currently serves as the managing editor of the  journal of structural engineering [ASCE International journal], editor of the  structural control and health monitoring journal [Wiley International Journal]  and editor of Structural Monitoring and Maintenance Journal. He is a fellow of  Structural Engineering Institute (SEI) of ASCE. He currently serves on the ASCE  SEI Board of Governors.