鋼筋混凝土為一種鋼筋、水泥、砂、骨材、水、附加劑所組合而成之高度非均勻複合材料，所以在檢測鋼筋、缺陷尺寸及位置上仍有許多困難。本論文目的在提供鋼筋混凝土結構物之非破壞檢測技術，其使用伽瑪射線之穿透性發展兩種方法，包括比較球體法及投影幾何法。其中比較球體法是利用伽瑪射線將鋼筋混凝土結構物內部之鋼筋、裂縫、孔洞及結構物外之球狀物體同時投影在底片上，進而藉投影在底片上之球狀物體的放大率來評估鋼筋及缺陷尺寸的大小。而為提高檢測之準確度本論文另再發展投影幾何法，藉物件投影在底片上之幾何關係來評估鋼筋、缺陷尺寸及保護層厚度。 執行本論文方法檢測時，現場放射線施照所需之時間將是本方法成功與否的重要關鍵，因此為得知施照之曝光時間，本論文提出一鋼筋混凝土之伽瑪射線曝光曲線，其可明確建立射源強度、混凝土厚度與曝光時間之關係。經試驗與現場施作證明，本研究確實可有效提高檢測鋼筋及缺陷尺寸之準確度，並將作為結構安全評估之參考。 Reinforced Concrete (RC) is a highly non-uniformed complex material composed of cement, sand, aggregate, water, and admixtures. Due to the nature of RC, it is still very difficult to achieve expected accuracy in determining the size of steel bars and locating concrete defects in RC members. This thesis provides several non-destructive testing methods using penetrating γ-rays to project images of steel bars, cracks and holes in RC members on a film. These images are compared to the image of an iron ball whose size is known and hence the size of steel bars and concrete defects can be determined. To further increase the accuracy of inspection, the geometry of the projected images is developed to examine sizes and locations of steel bars, defects and cover depth. It is known that the key factor of obtaining successful result in (RT) method is the exposure time Radioactive Testing. Therefore, an exposure curve of γrays is generated from testing data and by which the relationship of radioactivity strength, thickness of the reinforced concrete, and exposure time can be precisely established. Through laboratory tests and on-site applications, these methods are proved to effectively increase the accuracy in locating and determining the size of steel bars and defects in RC structures, and the result of inspection can be used in evaluating the safety of construction structures.