既存橋梁結構之耐震能力評估

Abstract

九二一集集地震後，國內橋樑設計規範對於耐震力的要求作了相關的修正，於修正規範中新建橋樑要求在地震發生時，需要有較舊設計規範佳的耐震能力。以公眾安全的角度而言，修正後之耐震規範的確可以增加橋樑在地震發生時的可信賴度，然而在經濟性的考量上，新規範所產生的較保守設計，就可能增加額外的建造成本，因此本研究對於新修正的耐震設計規範進行探討。此外，針對依據舊規範所建造之既有橋樑，在面對新的規範地震力要求時，是否有足夠的耐震能力，也是另一個重要的探討議題。本研究採用位移設計法來評估既有橋樑耐震能力，依據墩柱的位移韌性能力，檢視橋樑於地震發生時是否有足夠韌性，以避免發生非預期之橋樑損壞，以保障大眾運輸安全。

The seismic design specification has been revised to meet the increased seismic loads requirement / demand in which all the new bridges are designed to higher seismic capacity after the event of Chi-Chi Earthquake. For ensuring public safety and increasing reliability of the bridge, the revised seismic design specification has adopted a more conservative design approach. Therefore, it would increase additional constructing cost. This study is to assess the related modifications to reflect the revision seismic design specification and another significant matter is to analyze whether the existing bridge employing the previous seismic specification has an adequate seismic capacity to meet the revised seismic demand. In this report, the methodology of displacement-based approach is adopted for the evaluation of existing bridges. The displacement ductility capacity of piers is employed to estimate whether the bridge has an adequate ductility meeting the safety requirement of public transportation during earthquake.