結構損傷評估為橋梁系統維修和管理的一項重要任務，本論文發展一種影響線偵測技術，首先量測梁結構跨徑上一點之位移影響線，透過沿梁空間上變數有關的位移影響線作二次微分，可清楚識別裂縫損傷的位置及嚴重性，由解析解及數值模擬證明此損傷評估技術在不同預力型態之梁上是有效且準確的，應用卡氏第二定理計算不同預力條件及損傷之梁位移影響線。因為量測之雜訊，實驗數據的損傷識別能力並不能完全呈現解析解及數值模擬的結果，但是將來如果可以降低量測雜訊的影響，由影響線反應的這種掃描型態損傷評估技術可提供一種改善檢查效率的方法。 Damage assessment of structure is an important task for the maintenance and management of bridge system. An influence line type inspection technique is developed in this thesis. The displacement influence line at a point in the span of a beam structure is measured first. Through the second derivative of this displacement influence line with respect to the spatial variable along the beam, both the locations and the severities of crack damage can be clearly identified. The feasibility and accuracy of this damage assessment technique are verified both theoretically and numerically of beams with various prestress states. The second Castigliano’s theorem is applied to calculate the displacement influence line of beams with various prestress conditions and damages. Due to the measurement noise, the capability of damage identification from experimental data is not as impressive as it shown in the numerical and theoretical investigations. However, this scanning type damage assessment technique by the influence line response provides a possible manner to improve the inspection efficiency if the effect from measurement noise can be reduced in the future.