Deformations and Stresses in the Structural Reinforcement when using Wending Rods

In monolithic construction, when manufacturing reinforcing articles on a construction site, technological requirements for the bending of rods may not always be observed. In various regulatory documents, there are differences in the technological requirements for this operation. The article presents the results of studies of the stress-strain state of reinforcement in the manufacture of clamps, pins and other products related to the bending of rods. Normative requirements and calculated values of limiting relative deformations for various classes of reinforcement and mandrel diameters are given. The recommendations of norms on the diameters of rods and mandrels in the manufacture of bent rods are checked and refined. The relative elongations or shortening of the fibers of the rod are determined by the difference in arc lengths of the midline and arc at a distance x from the midline. According to the results of the work, graphs of the distribution of the relative elongations of the rods are presented for different diameters of the mandrels as a function of the distance from the axis of the section. Plastic deformations develop practically over the entire cross-sectional area of the rod. The use of mandrels with radius less than R = 5r at the bending of armatures A400 and A500S is connected by the risk of cracking, delamination or destruction of the rod. The use of mandrels made from reinforcing bars A240 with mandrels of radius R = 2r is unacceptable, since edge deformations reach 35%, which exceeds the normative values and leads to the destruction of the rod. Also, the boundaries of the ratio of mandrel diameters for smooth reinforcement A240 and periodic A500S are presented. The results of this study can be used in practical work, as well as to establish the minimum mandrel diameters when using new types of reinforcement with other physical and mechanical properties.