Ultimate capacity of SHS X-joints made of normal and high-strength weathering steels

Abstract

The aim of the current work is to study the static strength properties of welded tubular X-joints made of weathering steel. Quasistatic tensile and compression tests were carried out on welded tubular X-joints made of three weathering steel grades. The X-joints were manufactured from squared hollow section (SHS) tubes of 355WH, 500WH and 550WH weathering steel materials and prepared using gas metal arc welding with a LNM 28 solid wire (diam. 1 mm) as a welding consumable. Both joints with equal and unequal brace width to chord width (β = b1/b0) ratios were studied and a total number of 17 quasistatic tests on the X-joints were conducted, of which four specimens were tested in compression and 13 were tested in tension. In addition, flat coupon specimens were manufactured from the weld sections of the joints with the ratio of β = 1.0 for quasistatic testing, supported by the macrographical investigations, hardness measurement and scanning electron microscopy (SEM) analysis at the joint area. The obtained experimental ultimate capacities exceeded the design resistances for axially loaded joints as per the Eurocode 3 standard and the results thus indicated that the present standard can be used for design purposes of tubular joints made of weathering steels. The investigated high-strength weathering steel grades suffered from the strength reduction due to the welding and the limitations regarding heat inputs should be carefully considered.