近年來土木工程建設損傷評估漸漸受到工程人員的重視。在本研究中，我們應用摸態分析技術來針對人工缺陷梁進行檢測。另外我們必須發整一套量測技術以獲得足夠的分析資料。我們使用Graffi’s彈性動力互易定理，由最少數量的感測計獲的梁之振動反應。藉由傳遞函數法及亞伯拉罕時間序列法，從所得之離散振動訊號來求得有/無損傷梁之模態。 我們可以由傳遞函數及亞伯拉罕時間序列法所獲得之模態振動函數，求得鋁梁之缺陷位置。由於亞伯拉罕時間序列法是採用穩態振動訊號，而傳遞函數法是使用暫態反應，因此並不會受到外加作用力延遲的影響。在研究中，使用亞伯拉罕時間序列法來進行損傷檢測，似乎比較容易也比較穩定。我們也對雙裂縫梁進行損傷評估，發現獲得一趨勢，但結果沒有比單一裂縫來得顯著。在現今的研究中，一套簡單的梁損傷評估量測分析技術已逐漸發展。而這門技術可以延伸至複雜的構架系統。 Damage assessment of civil infrastructure is interested by engineers for decades. In this study, the modal analysis technique is applied to detect artificial defects of beams. To get enough analysis data, a measurement technique is also developed. The Graffi’s dynamic reciprocal theory of elasticity is used to obtain vibration response at impact sites along the beam from a minimum number of sensors. Mode shapes of undamaged and damaged beams by the transfer function method and Ibrahim time domain (ITD) method can be calculated from these distributed vibration signals. Location of defects in the aluminum beam can be detected from the variation of mode shape function either from the ITD or the transfer function method. Since the ITD technique just is using the vibration signals of steady state and does not like the transfer function technique uses the transient response that is affected by the duration and intensity of input loading. It seems that the damage mode obtained by ITD method is more stable and is easier for damage detection. Damage assessment of a beam with two separated cracks was also conducted, the locations of defects can be detected but was not so distinguished as the case of single defect. However, a simple measurement and analysis technique for damage assessment of beam is developed in current study. This technique can be extended to complicated frame structure.