以真實地震紀錄作為耐震需求之詳細評估及軟弱層檢核

Abstract

於2016年高雄美濃地震及2018年花蓮地震後，台灣有許多損傷嚴重之中高樓層建築物，其中大多為住商混合型式之樓房，因為使用需求，往往建築物低樓層之隔間牆量設計不足，或是採用樓層挑高等手法，導致樓層勁度及強度不連續，於強震來襲時，低樓層倒塌之可能性將大幅提高，對於建築物的耐震能力有致命的影響。 此外，根據地震觀測站之資料分析可發現，真實地震紀錄之加速度反應譜可能會有別於《建築物耐震設計規範》 [1] 之設計反應譜，因此，本研究選用兩棟中高樓層案例，將2018年花蓮地震之測站紀錄資料，透過等效單自由度結構之動力分析，得其於實際地震時之耐震需求 (需求譜加速度)。另於ETABS分析程式中建立結構模型與相關構件之非線性鉸，執行側推分析得其耐震容量 (容量譜加速度)，以進行耐震詳細評估，同時於側推分析後，藉由分析結果進行結構之軟弱層檢核。 經由分析與檢核結果，將判斷為危險之案例，採用外置RC構架暨剪力牆之工法進行階段性補強，以降低倒塌之風險。於補強後，亦藉由側推分析與相關之檢核確認該補強設計可消除既有結構之低矮樓層軟弱層現象及結構不良破壞模式之問題，確實可達成階段性補強之目標。

After the Kaohsiung-Meinong Earthquake in 2016 and the Hualien Earthquake in 2018, there were many mid- to high-rise buildings being serious-damaged in Taiwan. Most of them were residential and commercial mixed-use buildings. Due to the functional demand, the design of the partition walls on the lower stories of these buildings was often inadequate, or the height of the lower stories was designed to be higher. These two reasons might result in the discontinuity of story stiffness and strength, when the strong earthquake struck, the possibility of lower stories being collapsed would be greatly increased, which had a fatal impact on seismic performance of the building. In addition, according to the data analysis of seismic observatory, it could be found that the acceleration response spectrum of the real earthquake record was different from the design response spectrum in the “Building Seismic Design Code” in Taiwan. Therefore, two mid- to high-rise examples were selected for this study. Through the dynamic analysis of the equivalent single-degree-of-freedom structure with the 2018 Hualien earthquake record, the seismic demand (demand spectral acceleration) of the actual earthquake could be obtained. By means of the nonlinear static pushover analysis of the structural model established in the ETABS, the seismic capacity (capacity spectral acceleration) could be obtained. Then, seismic detailed evaluation could be done with the seismic demand and capacity. Also, after the pushover analysis, the soft and weak stories in the structure could be checked based on the results. According to the results of analysis and checks, the example judged as dangerous would be stage-retrofitted by the external RC frame and shear wall to reduce the risk of collapse. After the retrofit, by the pushover analysis and the related checks, it was confirmed that the retrofit design could eliminate the problem of the soft and weak layer on lower stories, and also the poor failure mode of the existing structure. It was indeed possible to achieve the goal of stage-retrofit.