台北市東西向高架道路橋為一種特殊形態之鋼橋，交通部氣象局強震網計畫已於其中安裝強震儀及集錄系統，收集多量地震及橋梁結構反應資料。本文擬利用台北市高架橋梁安裝強震儀段收集之資料，進行系統識別計算、建立分析模型，據以進行該橋之耐震能力分析，並檢討垂直向地震對橋梁耐震設計之影響，研究結果顯示垂直向地震對該類型橋梁之地震反應影響甚小。分析所得之能力曲線可供Haz-Taiwan計畫之應用。 The Taipei viaduct Bridge is one of the special type steel bridge in Taiwan area. In order to understanding the structural characteristics and earthquake responses of the bridge, strong motion accelerometers have been installed on the bridge by National Central Bureau of Weather. In the present study the seismic data collected has been analyzed by using techniques of system identification. The parameters estimated by system identification are used to revise the finite element model set up for seismic assessment of the bridge. In addition, the influence of vertical excitation on dynamic responses of the bridge has been studied. It is found that the effect of vertical excitation of earthquakes is minor. The seismic capacity of the bridge obtained can provide information for Haz-Taiwan Program.