Effect of transverse ribs on axial displacement of rebars in bending

Abstract

The strength of buildings is increased by using rebars; these are curved bars obtained with a bending machine and are primarily used with concrete. It is a known issue that a rebar tends to be displaced during bending so that it is no longer touches the fulcrum roller due to deformation and translation inherent to the process. Therefore, the processing conditions are determined based on the shapes of test products and experience of technicians. A reduction in the displacement of the rebar is desired to improve the dimensional accuracy of products. The ultimate aim of this study is to better understand the effect of bending on the axial displacement of rebars. Because deformation of the rebar may occur in one or more directions, many displacement sensors are required to determine the details of the deformation. In this study, the deformation of rebars during bending was photographed with a high-speed camera, and the displacement of the rebars was determined using image analysis based on the captured moving images. A small increase in the axial displacement due to bending was observed in the first half of round bar processing. In contrast, the displacement increased significantly in the second half of processing. It was found that the amount of axial displacement increases with the rotation angle of the circular roller during bending. The bending tendency of D22 rebars under the same conditions as D25 rebars showed different trends in axial displacement growth. In the case of D22 rebars, it was found that the displacement barely increased in the first half of processing but increased significantly in the second half of processing, as with the case of the round bars (φ23).