新型態外部隔減震技術－地震超材料之設計與分析

「地震超材料」是一種新型態的隔減震技術應用，概念源起於電磁超材料。本文將人造週期性材料的濾波消能特性運用在隔減震工程之中，與傳統結構隔減震最大差異在於，超材料不需於結構體直接接觸，於周邊外部便能發揮功效。其手法為將人造週期性結構圍繞於建物外圍土層中作為屏障，當地震波通過此材料到達結構物之前，會先與此材料產生共振交互作用，將部分震波能量限於週期結構內部，使特定傷害性較強頻率的波無法通過，進而達到保護功效。但由於地震波頻率低、波長大，所需的週期性結構體積也十分龐大，離工程實作應用尚待一段完整實證的歷程。本文將此概念作一介紹與探討，包含設計原理、分析模擬及成效，由離散模型著手計算波在週期性系統中的基本傳遞特性，並探討微觀結構材料配置對波傳的影響，整理出最適設計趨勢，並將概念延伸至連體設計之中，提出一精簡且具工程可行性的二維連體模型，透過有限元素分析結果顯示對於帶隙（bandgap）設計頻率區段內的平面波傳傳遞有明顯的衰減效果，未來期許結合實驗驗證，將理論應用於工程實作之中。

關鍵字

地震超材料；外部隔減振；週期性單元結構；局部共振

並列摘要

Seismic metamaterials are known as a new class of artificially structured media in which, within a certain designed frequency range, seismic waves can be attenuated or controlled in ways not seen in nature. The concept of metamaterials was originated from electromagnetic and acoustic waves about 10 years ago. This artificially engineered material utilizes coupling interference effect between propagating waves and local resonances to prevent the propagation of waves at frequencies near resonances. Seismic metamaterial, corresponding to long-wavelength and low frequency range, is a new research domain with some distinct features compared to those of other physical phenomena. In this work, we propose a simple two-dimensional configuration of seismic metamaterial, made of three different materials, aiming to mitigate the destructive effects of earthquakes. The simple model consists of concentric square cylinders, constituted by steel, rubber and soil, targeting at wave mitigation in the infrasound regime (1-10 Hz). Numerical simulations based on simplified discrete model as well as full-scale continuum layout will be studied. Our finite element simulations show that within the attenuation zone the displacement amplitude can be reduced significantly. These numerical studies demonstrate that the simple design of seismic metamaterial can be served as a promising tool towards seismic cloaking where a full three-dimensional simulation of body as well as surface waves, together with the geological information, can be properly accommodated.

並列關鍵字

seismic metamaterials ； external protection ； periodic unit cells ； local resonance

國際替代計量

新型態外部隔減震技術－地震超材料之設計與分析

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