| 種別 | report |
| 主題 | MEASUREMENT OF SURFACE DISPLACEMENT FIELD OF CONCRETE BY LASER SPECKLE METHOD |
| 副題 | |
| 筆頭著者 | Tirath Manojya Pallewatta（Asia Institute of Technology） |
| 連名者1 | Masaru TADA（Asia Institute of Technology） |
| 連名者2 | Hideyuki HORII（University of Tokyo） |
| 連名者3 | |
| 連名者4 | |
| 連名者5 | |
| キーワード | |
| 巻 | 12 |
| 号 | 2 |
| 先頭ページ | 835 |
| 末尾ページ | 840 |
| 年度 | 1990 |
| 要旨 | INTRODUCTION Accurate measurement of surface displacement field of a concrete specimen is of much significance in clarifying the governing mechanism of mechanical phenomena in concrete. Fracture phenomenon is a typical case which requires such measurement. Recently a remarkable progress was accomplished in the application of fracture mechanics to concrete. However the governing mechanism has not been clarified completely. Observations with Moire interferometry, laser holography and acoustic emission have been tried. There are several methods of measurement of a displacement field. The laser speckle method is one such method which provides high accuracy with simple equipment and procedures. With this method it is not necessary to touch the specimen. The information of surface displacement field is kept on a film and the displacement of each point is obtained point wise after developing the film. Accuracy of the technique is subjected to the measurement of fringe spacing projected on a screen. Moire interferometry method and laser holography method provide real time measurement (as the test is being conducted) of displacement field as two dimensional image information. To achieve a high degree of precision, a very fine grating must be carefully pasted on the specimen in Moire interferometry method. Laser holography method provide high accuracy but requires a number of equipment and very delicate settings. The purpose of this article is to report on the application of laser speckle method to concrete. An image analysis technique is employed to improve the precision of measurement. It is shown that relative displacements can be measured with an accuracy of +1μm by the present method. The method is employed for several types of fracture tests with a special interest on the measurement of crack length and distribution of crack opening displacement. APPLICATION TO FRACTURE PROBLEMS Application of the above method to various problems in concrete engineering seems to provide valuable information. The following are some of the application already tried out. 1.Determination of crack length and distribution of crack opening displacements with increasing load. The result is compared with theoretical prediction to discuss governing mechanism in fracture of concrete. 2.Fatigue crack growth in concrete under cyclic loading. 3.Crack propagation from an anchor embedded in concrete; see FIG.6. The crack length and mode of deformation are examined. The result is compared with theoretical prediction to evaluate the applicability of fracture mechanics to concrete. 4.Direct measurement of curvature of a RC beam due to flexural cracks. It is for the theoretical prediction of the role of flexural cracks in the deflection of an RC beam. |
| PDFファイル名 | 012-02-2141.pdf |