Ir Professor C.W. Lim
City University of Hong Kong
Title: Seismic Metamaterials with Low Frequency Wide Bandgaps Using Steel Barriers
Abstract: 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.
Prof. Genquan Qin
Strong Technology Co.,LTD.
Integration and Application of Key Technologies for River and Lake Water Environment and Treatment in the New Era
A. Prof. Fadzli Mohamed Nazri
Universiti Sains Malaysia
Title : The efficiency of an improved seismic vulnerability index under strong ground motions
Abstract: This paper examines the seismic performance of a Hospital Building damaged during the Ranau earthquake in Malaysia of intensity level (VIII), through an improved empirical seismic vulnerability index (SVI). The research aims at reducing the limitations and the uncertainties associated with the GNDT and the EMS approaches related to RC buildings, which can possibly be resolved by implementing the analytical techniques via applying nonlinear parametric analysis. Nonlinear time-history analyses were performed by incorporating an array of strong ground motions divided between far-field and near-field sets to assess the influence of each category on the SVI values and then comparing with SVI values obtained from the nonlinear static analysis (NSA). For a better comparison, the results are depicted in terms of collapse fragility curves for the modelled parameters. The proposed approach has been verified through observational fragility curves after Ranau earthquake. Whereas, the obtained SVI values were similar for the near-field and far-field, but with different collapse intensities and mean damage grades.