Evaluation of loading rate to the stress-strain response of reinforcing steel bar

Abstract

To obtain the material properties of reinforcing steel bar (rebar), a tensile test must be performed in the laboratory. Some standards, such as SNI and ASTM, standardize the condition of the sample and the loading rate of the tensile test. ASTM E8M regulates the loading application (1.15-11.5 MPa/s) of steel rebar test under tension to determine yield properties and SNI 07-2529-1991 governs 10 MPa/s as the maximum loading rate. These circumstances affect the duration of tensile test in real condition, which may lead to one hour of tensile test. In this article, the effect of loading rate of pre-conditioned steel bars (by reducing the section, grinding, and/or lathe according to SNI 07-2529-1991) is investigated using deformed bars (BJTS 40, certified by industries). Random samples of steel reinforcement bar are tested under three different loading rate applications. The result of the material properties of rebar, such as stress-strain curve, yield strength, and ultimate strength, are discussed and analyzed in this study. Different speed tests resulting in different stress rates before yield. However, the stress-strain responses of specimens in the range of linear elastic material are similar. Moreover, at the post-yield/plastic region, the loading rate significantly affected the ductility of the material.