中華民國八十九年九月二十一日凌晨1時47分16.00秒，發生台灣地震史上首見之強烈地震。震央位置為北緯23.86度，東經120.82度，約在集集東北方4.51公里處，地震規模達7.3級，並於地表產生長達105公里之地表斷層。此為世界地震史上所罕見者。由於車籠埔斷層帶兩側之地表產生最大之垂直高差達11公尺，最大水平錯動量約10公尺，在如此巨大之變化下，災區內之鐵路公路之橋梁、隧道均遭嚴重之破壞，以致交通路網全面受阻。 本研究之第一部份乃藉由本次921大地震之發生，討論台灣地區之地質條件及地震發生之原因，並探討本次（921）震災之發生原因。本文之第二部份歸納經由921地震後，公路橋梁各部構件之破壞行為，並希望能藉由此破壞行為之瞭解，對未來橋梁之設計有所建議。第三部份則就已受損惟仍屬堪用之結構物，提出補強與修復之方法，期能以最短之時間、最有效之方法，使得公路橋梁能儘快恢復其交通運輸之功能。最後並以烏溪橋之重建為案例說明。 九二一大地震帶給台灣無法磨滅之傷痕與教訓，而本研究之最終目的，乃希望藉由本文之探討，能更加瞭解地震對公路橋梁之影響，以期於未來能同時兼顧防範與搶修、補強。 In the early morning, the strongest earthquake motion of the Taiwan historical record in September 21, 1999 Chi Chi earthquake (ML=7.3) was occurred. The epicenter was located at 23.86°N,120.75°E and its distance is about 4.51 km NE far from the Chi Chi city. The 105 km length of earth surface ruptures was produced. There were extensive surface slipped with vertical displacement about 11 m and lateral strike slip about 10 m along the Chelungpu Fault. The road and rail bridges, tunnels were damaged badly in the disaster area. The earthquake broke all of the transportation nets down. There are three main categories in this study. Firstly, we want to discuss the geologic structure of Taiwan and the reason why the earthquake occurred frequently in Taiwan seismic history. Furthermore, we also discuss the cause and phenomenon of the Chi Chi earthquake. Secondary, all elements of the damaged bridges behavior is concluded after Chi Chi earthquake in order to make the optimum of the bridges design about preventing the seismic hazards in the future. Finally, to the bridge structures lightly injured after the earthquake shake, we make suggestions about the damaged bridge for recovery and strengthen methods, in order to restore their transportation functions efficiently, economically as soon as possible. The Chi Chi earthquake leaves a suffering memory of Taiwan people that can't be eliminated. To sum up, we hope that we can realize the complex pattern of surface faulting adequately after Chi Chi earthquake. In order to reducing the affect to the bridges after any earthquake motion in the future.