STRENGTH, STIFFNESS AND FAILURE MECHANISM OF DOUBLE SHEAR WELDED CONNECTIONS BETWEEN COLD-FORMED AND HOT-ROLLED STEEL

Abstract

Cold-formed steel is widely used for routine structural steel design including portal frames composed of open and/or closed sections. Nowadays, cold rolled steel channel and Z sections are now used in structure as a structural member with the hot rolled steel by welding connection. The connection between hot rolled and cold rolled steel is very important in the structure. Structural behavior of steel structures generally depends on the rigidity of the connections and their force transfer mechanism. In the present study, an experimental investigation has been conducted on double shear welded connections made of ASTM A653 Gr.50 and ASTM A36 grades of cold-formed steel. Primarily a set of coupons extracted from the cold form steel of different thicknesses and steel grades are tested under uniaxial tension to understand their actual strength and modulus of elasticity. In addition, a total of 4 numbers of weld coupons are fabricated to determine different weld specifications used in this study. Finally, 24 test specimens of double shear welded connections are formed by overlapping two cold-formed steel plates of similar thickness with the two hot rolled steel plates and forming a double shear welded connection at the joint. The influence of weld strength, plate strength, and plate thickness on joint behavior is evaluated meticulously by employing standard data acquisition system. These weld connections are tested on tensile loading until failure. The response of the double shear welded connections for varying material properties is examined in terms of load-elongation plot, connection strength, failure mode, stiffness, and ductility. It is observed, that with the increase of plate thickness failure mode changes from net-section fracture to weld throat failure. Usually increasing weld strength, steel grade, and plate thickness shows a rise in joint capacity and stiffness. Current American design provisions are evaluated for these ASTM A653 Gr.50 and ASTM A36 grade samples. Research into the Heat Affected Zone (HAZ) strength resulting from joint welding reveals a reduction in joint capacity of 6 to 19% due to the Heat Affected Zone (HAZ) effect.