WES 2808 for Brittle Fracture Assessment of Steel Components Under Seismic Conditions Part II: Change in Mechanical Properties of Structural Steels by Pre-strain and Dynamic Loading

摘要

The yield strength and tensile strength of the steels are varied by pre-straining, dynamic loading and temperature. In addition, the fracture toughness is strongly affected by the strength variation. Therefore, the fracture assessment of steel weldments under seismic loading condition needs to be considered the effects of strength variation caused by cyclic and dynamic large strain. In WES 2808:2003, the estimation method of strength increase with superposition effect of pre-straining, dynamic loading and temperature was proposed in the strength range of 400 - 590 MPa class steel plate, 400 - 490 MPa class H-section steel and 590 MPa class weld metal. However, 780 MPa class steel plate has recently begun to be applied in building structures. Therefore, the strength range of the estimation method needs to be expanded. In this study, the dependence of strength variation on pre-straining for 780 MPa class steel plate was investigated by experiment. And the applicability of the WES 2808 strength estimation methods for 400 - 780 MPa class steel was investigated. As a result, the effects of pre-straining on both the yield strength and tensile strength of the 780 MPa class steel were revealed. In addition, new equations that are based on old equations of WES 2808:2003 for estimating the strength with varied pre-straining are proposed. The strength range of the estimation method could be expanded.