Fracture Behavior of Structural Steels under Earthquake Dynamic Loadings

Abstract

The satisfactory design of the components is highly dependent on the adequate knowledge of the material behavior and operational conditions. For the structures under earthquakes, often this information is not available, is incomplete or inaccurate, and leads to increases the risk of the possible failures. The extensive brittle fracture of steel structures during the Northridge earthquake (USA, 1994) and Kobe earthquake (Japan, 1995) highlighted many of these deficiencies. The investigations have shown that the failures were caused by combination effects of high strain rate, welding defects, welding residual stress, and seismic loads. In this chapter, the effects of strain rates on mechanical properties of steel materials have been discussed. Welding defects act as cracks and cause the structures to fail at loads lower than design stress. Thus, the issue has been evaluated from the view point of failure mechanics. Welding processes produced residual stresses in the weldments. These regions have higher stresses triaxiality and will be prone to brittle fracture. Therefore, the role of residual stresses in the failure of steel structures is well expressed. The contents given in this chapter can be of great help in preventing the failure of structures during an earthquake and the occurrence of human and financial losses.