Truss chord members carry the primary axial forces in a structural truss — tension in the bottom chord, compression in the top chord under typical gravity loading. When a chord must be spliced at mid-span or at a panel point transition, the splice weld must transfer the full member force across the joint without a reduction in stiffness or load capacity that would degrade structural performance.
Chord splices are among the more demanding WPS applications in structural fabrication. They combine the full-penetration requirements of moment-connection flanges with the alignment precision that axial-load-carrying members require. Getting the WPS, preheat planning, and inspection sequence right matters here more than on many other joint types.
What a chord splice involves structurally
A chord splice is a butt joint between two chord segment ends. In design, the splice is usually treated as a full-strength connection — the weld must develop the full design capacity of the chord cross-section. For tension chords, the groove weld must develop the tensile capacity of the base metal. For compression chords, the compressive bearing area and weld configuration must transmit the full compression force without eccentricity or stability loss at the joint.
Chord members take many forms: wide flange shapes (W-shapes), tee sections cut from W-shapes, channels, hollow structural sections (HSS), or built-up box sections in heavy industrial truss work. The joint geometry of the splice — and therefore the WPS requirements — depends on the cross-section type.
CJP groove weld as the baseline requirement
For tension chord splices in structural trusses, AWS D1.1:2025 requires a complete joint penetration (CJP) groove weld. CJP groove welds develop the full plate or flange thickness in tension; the prequalified joint configurations in Clause 5 cover the butt joint geometries used in most chord splice applications.
PJP (partial joint penetration) groove welds are not appropriate for primary tension chord splices. PJP welds carry a throat penalty that reduces tensile capacity, and the unfused root acts as a fatigue initiation site in cyclic service. They are sometimes acceptable in compression chord splices where the compressive load transfers through direct bearing and the weld's role is positioning and stability — but even then, most engineers specify CJP to maintain consistent bending stiffness at the splice and eliminate root discontinuities.
See: CJP vs. PJP groove weld WPS requirements
WPS selection for chord splice groove welds
Process selection. SMAW low-hydrogen (E7018) for root and fill is a reliable shop choice for chord splices in A572 Grade 50 members. FCAW-G (E71T-1 or E71T-9) fill over an SMAW root pass is the high-deposition alternative for heavier chord sections. All-GMAW spray transfer works for clean shop conditions with good fit-up. The chosen process must have access to the root in the groove geometry; a tight, deep groove in a heavy W-shape flange restricts electrode angles.
Position. Shop-fabricated chord splices are typically welded in the 1G (flat) or 2G (horizontal) position with the member on rollers or a positioner. Field splices at erection joints may require 3G (vertical) or 4G (overhead) qualification if the erection sequence cannot reposition the member. Position qualifications on the WPS and WPQ must cover the field position before production welding begins.
Joint geometry. W-shape chord splices involve separate groove welds in the two flanges and the web. The groove configuration for the web and for the flanges may use separate WPS records if the process, polarity, or current range differs, or a single WPS covering both if essential variables align. Verify that the groove angle, root opening, and root face dimensions on the joint fit-up drawing match the WPS-qualified ranges before fit-up acceptance.
Steel backing. Most shop chord splices use steel backing bars on the root side of the groove. For statically loaded tension chords, backing removal is not always required but improves root quality and eliminates the backing-to-base-metal fillet weld as a fatigue detail. For cyclically loaded trusses — crane bridges, overhead conveyor structures, fatigue-critical industrial frames — backing removal and root back-gouging are standard practice in tension zones. See: CJP root pass inspection under AWS D1.1
Preheat requirements for heavy chord sections
Chord members in industrial trusses commonly use plate thicknesses or flange thicknesses of 1 in [25 mm] or greater. For A572 Grade 50 at 1 in, the minimum preheat per AWS D1.1:2025 prequalified conditions is typically 150°F [65°C] at ambient temperature. Cold ambient conditions, higher carbon equivalent, or high-restraint joint geometry require preheat above the table minimum.
The high-restraint nature of a chord splice — two chord segments with their full cross-sections butted together, often with steel backing — means transverse shrinkage is constrained from both sides. High-restraint CJP groove welds with insufficient preheat are a recognized cause of transverse hydrogen-induced cracking. The crack typically initiates in the heat-affected zone beneath the weld and may not surface visually for 24–72 hours after welding.
Preheat must be verified before arc strike and maintained as the interpass temperature minimum throughout the weld. For a multi-pass chord splice on a heavy W-shape, the interpass temperature minimum equals the preheat minimum, and the interpass maximum is typically 550°F [288°C] unless the WPS specifies otherwise for low-heat-input applications. See: Preheat and interpass temperature on a WPS