What is a yield point?

When the steel or sample is stretched, when the stress exceeds the elastic limit, even if the stress is no longer increased, and the steel or sample continues to have obvious plastic deformation, this phenomenon is called yield, and the minimum stress value when the yield phenomenon is generated is the yield point. With the development of building seismic technology and the in-depth analysis of seismic mechanism, energy dissipation seismic technology has become a developing trend of building seismic technology.

Performance requirement

In addition to the high strength and good plasticity of structural seismic steel, the strain-aging sensitivity, brittle transition temperature, low cycle fatigue resistance and welding properties of steel should also be considered. Low yield point steel is mainly used to make energy dissipation dampers, and its anti-seismic mode determines the performance requirements of steel.

In the earthquake, the energy dissipation damper is required to bear the seismic load before other structural parts, and repeatedly deforms in the plastic zone to absorb seismic energy, so as to achieve the purpose of earthquake resistance. Therefore, the low yield point steel must have a very low yield point and the yield range is controlled in a very narrow range, but also have good processing and welding properties, and have good plasticity, so as to have good deformation ability.

In addition, seismic steel is subjected to repeated alternating loads during an earthquake. The duration of strong earthquakes is generally within 1min, the amplitude frequency is usually 1~3Hz, and the damage of buildings is caused within 100~200 cycles, which belongs to high strain and low cycle fatigue. Therefore, the low yield point steel must have good resistance to low cycle fatigue.