| In recent years, more and more requirements on the quality of construction are presented, which speed up the development of civil engineering. And higher requirements of civil engineering experimental techniques are also proposed. Existing engineering study methods, such as displacement meter, dial indicator, strain gauge and so on, are often subjected to less measuring points, position and measuring range which interfere with each other as electromagnetic interference and space constrains. The results of measurement are often approximate relative deformation characterization based on single measuring point and single direction. This is not conductive to represent deformation on samples. The Digital Image Correlation(DIC) technique enables full-field, non-contact deformation measurement. But when measuring the typical components in the civil engineering experiments, like columnar, annular and longilineal specimens, it is difficult to use the 2D-DIC or 3D-DIC techniques to achieve full field deformation measurement with high accuracy. As a result, one multi-camera DIC system is introduced in this paper, and its accuracy has been studied. It can well meet the civil experimental measurement requirements. Apply the multi-camera digital image correlation system to measuring the deformation of the long beams, columns and square columns. In these experiments, the system has been used to conduct the displacement measurement and strain measurement, and record the development of the crack. Focusing on the applications of the multi-camera digital image correlation system in civil engineering experiments, the main contents and achievements of this paper includes the following aspects:(1) The multi-camera digital image correlation system can be arranged in two different ways. One is continuous system in which there are overlapping field-of-views of at least 1/2 between neighboring cameras. By this way, it can obtain the complete information in a continuous deformation under the action of three-dimensional digital image correlation technology and image stitching technology; Another one is discrete system in which 3D-DIC subsystems are distributed and no or little overlapping field-of-view exist between subsystems. It can get the deformation information which is independent and discrete. Actually, using discrete system is equivalent to using several 3D-DIC systems at the same time.(2) Design experiments to study the test precision of the multi-camera digital image correlation system. Using the load displacement as a reference, the relative precision of the in-plane displacements can reach 0.01%,and the relative precision of the out-plane displacements can reach 0.01%. The results are both better than the results got by the 3D-DIC system. Using the results that measured by strain gauge, when the deformation of the specimen exceeds 20%, the average on the timeline of the relative error of the eight-camera DIC system is 8.67%.(3) The flexural behavior of Coral reef concrete beams which are reinforced with BFRP bars have been researched. The full field deformation information of the long beam has been achieved, which implied a close match between deflection measurement and displacement meter's results. The load-displacement curve was obtained and strain field was used to record the development of the crack.(4) The deformation of the BFRP confined HRBF500 column which is under low-cycle fatigue load was monitored by eight-camera DIC systems. The fatigue damage property was studied based on strain field, fracture development and displacement response of the column.(5) FRP-steel composite columns was measured using discrete multi-camera digital image correlation system to get deformation under compressive force. The out-plane displacement field has been obtained which is used to observe the damage process and lateral deformation. |
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