Fracture behavior of welded steel structures subjected to dynamic loads

The Marmara earthquake on August 17, 1999 resulted in great human tragedy for the Turkish people. Thousands of people died in the collapse of concrete building although steel structures, which are generally used for industry, could withstand. However, the Kobe in Japan (1995, January 17) and Northridge in US (1994, January 17) earthquakes brought about serious damage to some steel welded structures by unexpected failure in a brittle manner. This indicates that it is not only enough to use the steel structures in seismic areas but also necessary that they have ability of the connection to deform plastically without brittle fracture during an earthquake.The goal of this thesis is to investigate and develop the performance of the steel welded connections. To this end, the effects of the material properties of the weld which is used in steel structures, crack placed in the weld region and dynamic loading on the fracture behavior of the structure have been examined. ABAQUS 6.5 has been used to examine the stress distribution in the welded steel structure and fracture behavior. Elastic and elasto-plastic finite element analyses have been performed. The nonlinear finite element analyses have been repeated for various frequency values of different loading cases in order to see the effect of the strain rate, which defines the earthquake loads. It is concluded that electrode type affects the fracture behavior of the welded structure.Keywords : Fracture, finite element method, welded steel connections.