台北盆地鋼構抗彎矩構架之震損與風險評估

由於鋼構建築物重量輕、施工工期短、延性(ductility)能力強等優點，被廣泛地應用在人口密集且常發生地震的台灣。而在過去五十年間，台灣的鋼結構及耐震規範皆經歷了幾次重大的改革，實務設計上亦隨著規範修訂而演變，以致共存於台灣都市中之鋼構造建築物，皆依不同時期之性能目標所設計建造而成，而其對於都市整體震災風險之影響，卻尚未有系統性之探討。因此，對於依不同時期設計之鋼構造建築物，有必要建立一套合理之韌性評估系統，以作為相關決策者之參考依據。為探討台灣之鋼構造建築物於過去五十年間震災韌性之變化，本研究回顧了至今鋼結構耐震規範及實務設計演進之過程，判別出三個具代表性之時期，並以此為依據設計一系列不同樓高之鋼結構抗彎矩構架，作為構架原型。此外，為建立國內評估鋼構建築物震災韌性所需之易損性資料庫，本研究亦統整國內有關鋼結構梁柱接頭實驗之文獻，以決定各時期梁柱接頭之易損性曲線與後果函數。最後，有別於傳統耐震評估上將結構行為作為耐震性能指標，本研究參考美國FEMA P-58所提出之評估流程，以修繕時間、修繕金額、人員傷亡等指標來量化結構之震災韌性，配合商用數值軟體ETABS對原型構架進行非線性動力歷時分析，探討各時期鋼構造建築物在不同等級地震下之災損變化。評估結果顯示，在執行地震強度評估法之下，隨著建物樓層數之提高，平均每層所需花費之修繕金額越高，但在高樓層之後其提高趨勢則趨於平緩。而依據921地震前之規範所設計之建物其災損明顯為最高，且倒塌次數亦較其他兩個時期多，921地震後建物之震災韌性雖有顯著提升，但依現行法規新建之建物則因具有較大之樓層加速度反應而使非結構構件有較高之損害。因此，若以提升社區整體之震災韌性為目標，應優先補強921地震前所設計之建物，尤其是高樓結構，後續則可對新建建物之非結構構件進行改善，以降低其損害時所造成之機能折損與財產損失。

關鍵字

易損性曲線；震損評估；機率式風險評估；鋼結構耐震分析

並列摘要

Over the past 50 years, seismic design provisions and practices in Taiwan have experienced significant changes. As a result, steel buildings in the same Taiwanese community were designed using different principles and performance objects. However, it is still not well understood that how the evolution of the design provisions changes the seismic losses and risk of steel buildings as well as how the differences in these buildings affect the seismic resilience of communities. To address these shortcomings, a series of prototype steel moment frames with different heights are assumed to be located in the Taipei basin and designed according to the seismic design provisions and practices from the three representative eras spanning the past 50 years. The fragility curves, consequence functions, and nonlinear modeling recommendations of steel beam-column connections are also developed based on an extensive set of experimental data to enable seismic loss assessment of buildings in Taiwan. The performance-based probabilistic framework employed in FEMA P-58 is conducted to quantify the differences in the resilience of prototype frames in terms of repair time and repair cost. The assessment results show the seismic loss of buildings designed prior to Chi-Chi earthquakes is obviously higher than the newer ones, but the improvement by the latest revisions of seismic building codes is vague due to severer nonstructural damage under both design basis and maximum consideration earthquakes. Moreover, the average repair cost per floor increases with the increase of building height. Therefore, to optimize the community resilience, the retrofit of buildings constructed before Chi-Chi earthquakes and non-structural components in new the buildings should receive higher priority based on available resources.

並列關鍵字

Fragility curves ； seismic loss assessment ； probability risk analysis ； finite element analysis ； steel structures

參考文獻

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台北盆地鋼構抗彎矩構架之震損與風險評估

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