12.23: Research on low‐yield‐point steels in Tsinghua University

Abstract

For the advantages of low yield strength, high tensile-to-yield strength ratio and excellent ductility, low-yield-point steels are extremely applicable for energy dissipation in seismic design of steel structures, so they are more and more used in steel structures in seismic areas. To get comprehensive understanding on material properties of low-yield-point steels and give support to the design and engineering application, the research group in Tsinghua University has conducted the study on the LY100, LY160 and LY255 three grades of low-yield-point steels in China. The data of mechanical properties such as tensile strength, yield strength, percentage elongation and impact work from the steel manufacturer have been collected and analyzed by the mathematical statistics method based on the reliability theory, and the partial factors for resistance of low-yield-point steels have been proposed. Also low-yieldpoint steel coupon specimens were tested by different cyclic loading programs, and the constitutive models under cyclic loading were proposed and calibrated. Furthermore, the lowcycle fatigue behavior of low-yield-point steels were studied by tests, and the test results can be used to predict the cyclic loading safety and life of low-yield-point steel components in steel structures under earthquakes.