混凝土結構物中之成分受到化學反應將會產生膨脹現象，致而誘發裂縫生成，裂縫將會造成混凝土劣化，影響結構物之耐久性及強度。 在傳統實務上乃採用接觸性方式量測。然而單一裂縫之寬度並非為一定值，且有人工量測之偏差存在。因此採用接觸性方式量測有相當多之不便與困擾存在。遂乃提出一套使用非接觸性量測方式來分析膨脹量與裂縫寬度間之關係以彌補現行實務上之不足處，並滿足對量測結果之一致性與重複性。 裂縫搜尋中為了提高其成果之可靠性因此採用半自動之方式來搜尋裂縫，除利用灰階資訊外尚再加上附加條件之輔助以得較佳之成果。為使求解更具穩定性，先使用高斯函數對資料作平滑化處理以減少雜訊干擾，並利用差分近似微分，算出像點的灰度梯度大小，俟透過取閥值等操作便可將邊緣檢出。 將所搜尋出之裂縫邊界處與人工所數化之結果作一比較，以瞭解所提出之搜尋方式與人工所數化結果間之差異。 The elements of concrete structures suffering from chemical reactions trend to be an expansion phenomenon, which lead to cracks. The concrete structures of inferior quality caused by cracks have much influence on the structures’ durability and strength. The non-contact measurement is employed because of the physical limitations in manual measurements. This paper deals with semi-automatic crack feature extraction from digital close-range images to infer the relationship between concrete expansion and crack width. Only few manual seed points are required on crotches of crack features. Then, the shape and position may be illustrated with automatic feature extraction in two- dimensional image space. In the process of crack searching, a Gaussian filter is applied in advance to smooth the noise along crack profiles to improve the reliability and precision. Subsequently, the edges of cracks are determined by computing the gradient of the crack profiles. The edges of cracks detected by the proposed algorithm will be compared with the one digitized by manual operations.
