Modeling of the residual stresses in welded beam ? to ? column connections

Residual stresses induced by the welding process are regarded as secondary stresses and generally disregarded. However, they have unfavorable effects on the overall performance when the structural integrity of the system is considered and may cause sudden brittle fractures. Since a, triaxial stress case occurs in welded connections, this decreases the capability of plastic deformation of the structure. Some factors such as welding speed, material properties, welding method, type of connection, number of pass and cooling speed determine the order of the residual stresses. The aim of this thesis is to examine the effects of the connection types, welding speed and cooling rate on the residual stresses and to predict the welded column-beam connections in the steel structures resistant to earthquake loads.In this study, the residual stresses in the welded steel column-beam connections arising during arc welding are determined using nonlinear finite element method with ABAQUS software. Transient mechanical and thermal analyses are performed. In order to obtain realistic results, material properties are defined as functions of temperature. Three-dimensional finite element models are developed and welding process is simulated in order to investigate the characteristics of the residual stresses in the welded connections. Three different connections are modeled to investigate the effect of the type of the connection on the residual stress. The conditions of stresses are determined for six different thermal cycles. In addition, the effect of the welding access hole is examined. The order of the residual stresses increases with the presence of the welding access hole. On the other hand, extending the cooling time decreases the order of the residual stresses.