Seismic Metamaterials with Low Frequency Wide Bandgaps Using Steel Barriers

讲座名称: Seismic Metamaterials with Low Frequency Wide Bandgaps Using Steel Barriers
讲座时间 2020-01-10
讲座地点 航天学院 第四会议室
讲座人 C. W. Lim
讲座内容

题目:Seismic Metamaterials with Low Frequency Wide Bandgaps Using Steel Barriers
报告时间:  2020年1月10日(星期五)上午10:30- 12:00
报告地点:航天学院 第四会议室
报告人:C. W. Lim
报告摘要:
The feasibility of built-up steel section as barriers of seismic metamaterials is proposed in this study.  We consider two types of built-up steel sections (as resonators) and the surface waves propagation in a single layer homogenous medium and a six-layered soil medium (substrate) is investigated by analytical and computational techniques.  The presence of resonator on the surface of a semi-infinite substrate results in the generation of local resonance that induces low frequency wide bandgaps.  The generation of local resonance bandgaps are mainly governed by the impedance mismatch between resonator and substrate and the coupling of surface waves propagating on the surface of a semi-infinite substrate with a longitudinal mode of resonator.  We further consider the surface waves propagation in both types of media and compared the bandgap frequencies.  For layered soil media, a bandgap with relative bandwidth greater than 1.5 is reported that indicates the surface wave bandgap is relatively wide and it is located at a low frequency.  The result also shows the effect of impedance mismatch on the bandgap width.  Furthermore, with a change in geometric parameter of the resonator and material properties of substrate, the position and width of bandgap do vary.  The infinite unit cell model study is further validated by a finite unit cell based frequency response and time transient analyses.  An excellent agreement is observed.  The time transient analysis results indicate more than 50% reduction in vibration amplitude of the surface waves.  The study provides an insight for having steel piles to protect critical infrastructures from earthquake hazards..

讲座人介绍

Currently a fellow of ASME, ASCE, EMI and HKIE, Ir Professor Lim received a BEng from Univ of Tech. of Malaysia, MEng and PhD from National Univ of Singapore and Nanyang Tech. Univ., respectively.  Prior to joining CityU, he was a post-doctoral research fellow at Dept of Civil Eng, The Univ of Queensland and Dept of Mech Eng, The Univ of HK.  Professor Lim is also a visiting professor at various universities including the Univ of Western Sydney, Dalian Univ of Tech., Huazhong Univ of Science and Tech., etc.  He has expertise in vibration of plate and shell structures, dynamics of smart piezoelectric structures, nanomechanics and symplectic elasticity.  He is one of the editors for JoMMS, Assoc Editor (Asia-Pacific Region) for JVET, Assoc Editor for IJBC, subject editor for AMM, etc. and also on the editorial board of some other top-ranked international journals.  He has published one very well-selling title in Engineering Mechanics entitled “Symplectic Elasticity”, co-authored with W.A. Yao and W.X. Zhong from Dalian Univ of Tech., as recorded in April 2010 by the publisher, World Scientific.  He has published more than 280 international journal papers, accumulated more than 6000 independent citations and has an ISI H-index 42.  One of his papers co-authored with G. Zhang and J.N. Reddy, is a highly cited paper in JMPS and the most cited paper since 2009 in the journal, while another co-authored with L.H. He and B.S. Wu was granted the IJSS 2004-2008 most cited article award.  He was also awarded Top Referees in 2009, Proc. A, The Royal Society.  Professor Lim is also a registered professional engineer in HK.

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