Abstract: In the method of welding open web steel joists a chord member is formed by bending a web in an undulating configuration. The chord is welded to the webs by simultaneously clamping and resistance welding to form four welds. The weld current is applied by a series of time controlled intermittent impulses of electrical current. The weld electrodes used are of unequal resistance so as to balance the heat generated.

Abstract: In an electric resistance welding machine for welding structural members together along a common region of contact through the intermittent application of heat generating electrical energy to said region of contact the combination of; electrode means adapted to releasably contact and clamp said members together so as to exert an external force to said members for urging said members together at said regions of contact, and to transmit and apply said electrical energy to said members in said region of contact on an intermittent basis, transformer means associated with said electrode means for supplying said electrical energy to be intermittently applied to said members in said region of contact, control means for controlling the intermittent application of said electrical energy to said region of contact for a selected timed interval, including means for interrupting said application of said electrical energy for a selected timed interval so as to present a series of intermittent impulses of said electrical en

Abstract: Apparatus for fabricating metal trusses having spaced preformed chord members of generally longitudinal predetermined length and cross-section joined by at least one preformed supporting web member of predetermined length and cross-section by electrically resistance welding together the chord and web member at a common region of contact with the chord member having a smaller cross-sectional area than the web member at the common region of contact. A device includes in to place a station for cleaning the chord and web members, means for moving the clean chord and web members to an assembly station for assembling the chord members in spaced relation joined by the web member. A device for passing the assembled truss along a support to the electrical resistance welder having opposed first and second electrodes of unequal resistance and adapted to releasably clamp the chord and web members respectively at the common region of contact.

Abstract: A device for non-destructively simultaneously testing the shear strength of at least four welded joints presented by a metallic truss having two spaced substantially parallel chord members joined together by a substantially coplanar web member bent into a substantially uniform undulating configuration between the chord members so as to present a series of alternate opposite apices at the bends welded to the spaced chord members respectively along regularly spaced intervals longitudinally of the chord members, the device including; elements for simultaneously clamping the chord members in at least four positions adjacent the welded joints, including elements for eliminating the twisting of the welded joints from the plane defined by the web member during the simultaneous clamping, and elements for simultaneously applying a substantially perpendicular force relative the plane defined by the web member, for a selected timed interval, to at least four of the apices defined by the bent web member, adapted to test