考慮工址放大效應之建築耐震補強

Seismic Strengthening of a Building with Site Specific Ground Amplification Consideration

This study presents a seismic retrofit strategy of buildings related to the site geological characteristics, and a case study is demonstrated in this study. An old temple had been retrofitted several times but still suffered damages continually from recent earthquakes. In order to find out a good retrofit strategy to strengthen the temple, we studied the strong motion characteristics of earthquake records by using response spectrum analysis from a nearby seismic station. The results indicated that increasing the building's stiffness would also increase the input energy. Therefore, we proposed another retrofit scheme by consuming earthquake energy instead of increasing the building's stiffness. In order to quantify the effects of the retrofit schemes, a computer structural model of the target building was built and its accuracy was verified by using ambient vibration experiment. In this study, a conceptual strengthening model was developed and the computer analysis was targeted for the temple's inter-story drift ratio to be kept under 0.5%. The effect of the final design was analyzed and discussed. 本研究以實際案例說明建築物之結構補強受到建築物工址特性的影響，一棟老舊之庵廟院宇為當地著名之信仰中心，並受到居民的敬重且香火亦十分鼎盛。然而在近年幾次大地震的作用下，建築物均有受到破壞的情事發生，因此本研究透過電腦結構模型並嘗試不同的補強型式，最終提出適當的耐震補強方法，用以提升該建築結構的耐震強度。本研究的內容首先在於說明地建築物結構模型之建立，並與現地量測之微振動分析結果進行比對，適度調整電腦結構模型使之能合理模擬該建築物之結構特性，同時亦能提供高準確性之預測分析。本研究採用該建築物最近地震測站所量測之地震記錄進行電腦模型之動力分析，確實暸解建築物在地震作用下之振動情形，並探討受損較嚴重處的原因，同時亦針對建築物附近的地震紀錄進行反應譜分析，從分析中發現在該工址中建築物之自振頻率愈高，建築物所受到的地震力也會相對增加，此結果顯示若依照傳統的補強方式，像是擴柱或增設翼牆，目的在於提高建築結構之勁度但同時也會相對提高建築物的自振頻率，在本案例中亦會造成建築物受到更大之地震力。本研究最終以消能的方式作為結構補強之主要方法，採用的耐震元件為版片型黏彈性制震壁（VEM Damper），此元件本身的勁度並不會造成建築物自振頻率的提升，但可以降低局部結構的變形量，同時能提供阻尼吸收地震能量，減少建築物之振動量以及加速度反應，相當適合針對地震力發揮制震效果，提高建築物的安全性及使用性。