Structural Details To Increase Ductility of Connections

Materials used in steel structures are increasingly becoming thicker and heavier. A greater chance of cracking during welding of beams to columns, for example, has resulted due to increased thickness of material. With weld shrinkage restrained in the thickness, width, and length, triaxial stresses develop that may inhibit the ability of steel to exhibit ductility. This paper will try to explain why these cracks may occur and what can be done to help prevent them by expanding on information presented in the AISC Supplement No. 1 (LRFD) or No. 2 (ASD). We will first consider the pulling of a simple tensile specimen to find out what conditions cause this ductile behavior. Then we will find out why this behavior goes from ductile to brittle when triaxial tension is applied. Finally, we will see what conditions under triaxial stresses the ductility can be restored. This information is then applied to the practical question of how wide the weld access hole in the web of a connection should be to avoid brittle behavior.