以結構性能為基準之鋼筋混凝土建築物耐震能力評估

Performance--Based Seismic Evaluation of Reinforced Concrete Buildings

對於位處地震高危害度地區之國家而言，建築結構物之耐震能力評估已成為相當重要的課題。近年來自從美國應用技術協會出版ATC-40，揭櫫了鋼筋混凝土建築物耐震性能評估指針以後，以結構性能為基準的建築物耐震能力評估觀念已廣受矚目，但其繁複的計算方法與精確度則仍有改進空間。本文導入一直接擷取結構容量曲線上性能點的觀念來決定建築物耐震能力的改良式評估法，除可改進ATC-40所提方法的缺失之外，同時亦可獲得各種結構性能狀態與地表加速度之間的相互關係。另一方面，由於構件桿端塑性鉸設定的良窳會直接影響側推分析的準確度，本文也就鋼筋混凝土構材三種常見的破壞模式來決定其塑性鉸之計算方式。最後，並以一座於九二一集集大地震中損壞之傳統低矮鋼筋混凝土建築校舍為研究案例，透過本文所提之側推分析流程，評估建築物所能承受的最大地表加速度，達到以結構性能為基準之耐震能力評估的目的，並續以非線性動力歷時分析進行相關驗證。本文研究成果顯示，依據本文所提方法可有效模擬鋼筋混凝土結構的非線性行為，且可不失準確性的評估出建築物之耐震性能，相關成果冀能供為學術研究與新建結構物耐震設計、老舊建物耐震能力補強及建築物損壞維修等實務參考之用。

For countries located at with high seismic risk, seismic damage assessment of buildings is an important issue. In the past few years, much attention has been paid to the performance-based concept of the assessment due to the appearance of ATC-40. However, its tedious procedure and deficiency in precision have left rooms for improvement. The present paper is to introduce a modified procedure to improve the efficiency as well as accuracy of the said assessment. The main ideal of the modification is that by treating performance point on structural capacity curve as input to determine the corresponding seismic demands of RC structures. This approach is also capable of finding the correlations between peak ground acceleration (PGA) and various structural performances. On the other hand, it was known that the accuracy of pushover analysis was greatly affected by the proper setting of plastic hinge. In this paper, an algorithm for determining plastic hinges with respect to three well-known distinct failure modes is also suggested. Finally, a traditional low-rise RC school building damaged in the Chi-Chi earthquake is adopted as a case study. In addition to follow the proposed seismic damage assessment method by performing the pushover analysis based on the suggested algorithm to find the ultimate PGA that the building could with stand, nonlinear time history analysis is also applied to verify its accuracy. It is seen that the proposed method gives acceptable results and is expected to be helpful both in facilitating the seismic damage assessment as well as making the strategy of repairing, retrofitting, or strengthening for RC buildings.