Hybrid Bolted-Welded Connections: WPS and CWI Considerations
When welds and high-strength bolts share a structural connection, AWS D1.1 WPS requirements still apply—but sequencing, heat effects, and inspection access create unique challenges for CWIs.
Most structural connections are either bolted or welded—the two systems rarely share the same joint. When they do, the result is a hybrid (or combination) connection that introduces procedural and inspection complexity that neither code addresses fully on its own. AWS D1.1 governs the welded portion. AISC 360 governs the combined connection design. The CWI sits at the intersection of both.
Understanding the code context, typical applications, and the practical WPS and inspection requirements puts the QC team in position to document hybrid connections correctly and keep them audit-ready.
Rule library based on AWS D1.1:2025; verify against your governing edition. AISC 360 references are to the current Specification for Structural Steel Buildings.
Why Hybrid Connections Are Rare
AISC 360 Chapter J contains a load-sharing provision that severely limits when bolts and welds may jointly resist a force. In most new construction, bolts and welds are not permitted to share load—the conservative assumption is that their load-deformation behaviors are too different for reliable joint action. Bolts in standard holes achieve their limit state at much smaller deformations than fillet welds, so the code assumes one or the other carries the full load.
The one exception in new construction: fully pretensioned high-strength bolts in conjunction with welds may share load when both are explicitly designed to do so. This requires the bolt group to be pretensioned per AISC Table J3.1 and the connection to be detailed to account for compatibility.
Hybrid connections appear more often in modification or strengthening of existing connections: adding welds to previously bolted connections, or adding bolts to supplement an existing welded connection. In that context, the existing fasteners may be considered sharing load with the new welds if proper engineering analysis supports it.
Typical Applications
Where you encounter genuine hybrid connections in structural fabrication:
Heavy splice plates on transfer girders. A transfer girder carrying column loads may have a deep plate girder web splice where the shear is too large for an all-bolted or all-welded configuration within available access or geometry constraints. The welds carry the flange axial forces; bolts carry the web shear.
Seismic moment frame column splices. AWS D1.8 and AISC 341 permit combination connections in column splices in certain seismic design categories. CJP flange welds carry the axial demand; bolted web plates handle shear. The two systems are not sharing a force—they are each resisting different components—but the joint assembly interleaves welding and bolting operations in tight sequence.
Crane runway beam splices and tie brackets. Fatigue-sensitive crane runway girders sometimes use welded bottom flange continuity combined with bolted web splices to facilitate field assembly and future maintenance access.
Strengthening existing structures. When a CWI encounters an AWS D1.1 Section 8 project (welding to existing structures), adding welds to a joint that already has in-place bolts is a standard scenario. The design engineer's sketch or specification governs what the bolt contribution is—the CWI's job is to execute and document the weld.
WPS Requirements: Nothing New, But Important Details
The welded portion of a hybrid connection requires a fully compliant AWS D1.1 WPS—prequalified under Clause 5 or qualified by test under Clause 6—no different from any other structural weld. What changes is the application context:
Preheat and interpass temperature: The base metal adjacent to bolt holes is the same steel as the rest of the connection. If Table 5.11 requires preheat for that base metal and thickness, it applies at the hybrid connection too. The presence of pre-installed bolts does not change the chemistry or thickness of the steel.
Joint access and electrode manipulation: Installed bolts can obstruct electrode angle and gun travel. When the WPS specifies electrode work angle ranges, verify those angles are achievable with bolts in place. If they are not, the WPS may need to account for the actual travel path or welding may need to occur before bolting. Document this on the WPS or in the connection-specific work instructions.
Heat input documentation: For adjacent Q&T steel or any connection where high heat input is a concern, the WPS heat input range must be observed. See Heat Input Qualified Range for Tested WPS for how to calculate and document heat input within the qualified range.
Sequence: Weld Before You Torque
The sequence of welding and bolting matters for bolt tension integrity. AISC engineering research shows that welding in proximity to fully pretensioned bolts can reduce clamp force through thermal expansion and contraction cycles. The bolt, which has been stretched past yield to achieve pretension, may relax as the surrounding base metal heats and then cools.
The accepted practice is: weld first, bolt last. Complete the CJP or fillet welds on the connection, allow the joint to cool to ambient, then install and pretension the bolts per the AISC Table J3.1 requirements.
When the sequence cannot be weld-first—for instance, when bolts serve as erection aids to align the connection before welding—the common approach is:
Install bolts snug-tight (not pretensioned) for fit-up
Complete welding and allow cooling
Pretension bolts to the required clamp force after welds have cooled
If bolts were already pretensioned and welding has occurred in close proximity, re-inspection of bolt tension using a torque wrench or tension-testing device is appropriate before the connection is released for loading.
CWI Inspection Priorities
When inspecting a hybrid connection, the standard AWS D1.1 visual and NDE acceptance criteria apply to the welds. Beyond those, the CWI should:
Verify welding sequence was followed. The inspection record should note whether bolts were snug-tight, pretensioned, or absent at the time welding began. Sequence departures are a quality record entry.
Inspect for weld spatter on faying surfaces and bolt threads. The faying surface (the mating face between connection elements) must be free of weld spatter, paint, oil, and debris that would compromise slip-critical bolt behavior. Spatter in bolt holes or on threads can prevent achieving the required pretension and constitutes a nonconformance. See Weld Non-Conformance Report Documentation for how to document and disposition it.
Check preheat on base metal near bolt holes. The full plate surface, including areas within 3 inches of bolt holes, must meet preheat requirements. A bolt-hole punch or drill through a plate leaves the edge in a potentially stressed state; preheat protects against hydrogen cracking propagating from those discontinuities.
Confirm electrode access and weld completion. With bolts installed, visually confirm that full electrode access to the weld joint was achieved—no missed weld passes due to obstruction. For partial-penetration joints, the specified effective throat must be achieved over the full weld length despite bolts being present.
AISC Chapter N Special Inspection
IBC-governed projects with structural steel typically require special inspection per AISC 360 Chapter N and the applicable IBC Chapter 17 provisions. For hybrid connections, the special inspector's scope typically includes both the welded portion (per AWS D1.1 and the WPS) and the high-strength bolting work (per AISC Specification Section J3 and RCSC Specification).
If a single special inspector is covering both scopes, verify they are qualified for both. AWS D1.1 CWI certification covers the welding inspection; AISC-qualified Special Inspector certification (or equivalent per local AHJ acceptance) covers the bolting. Some jurisdictions require both endorsements from the same inspector; others allow distinct personnel to cover each scope.
For the overlap at hybrid connections—where weld heat may affect bolt tension—clear documentation of sequence and post-weld bolt verification is the combined deliverable that satisfies both inspection programs.
Audit-Packet Considerations
When assembling the closeout package for a project that includes hybrid connections, include:
WPS and PQR for the welded components (standard)
Welder qualifications covering the process, position, and base metal (standard)
CWI inspection records noting weld sequence relative to bolt installation
Any bolting inspection records (turn-of-nut verification, DTI inspection, or pre-installation verification) related to bolts installed post-weld
Engineering note or RFI response confirming the load-sharing basis for the hybrid connection, if applicable
Hybrid bolted-welded connections are uncommon, but when they appear the CWI and QC manager need to address both the standard AWS D1.1 weld requirements and the unique complications that bolts introduce:
AISC 360 limits load sharing to specific bolt and weld configurations—verify the design basis
The AWS D1.1 WPS applies unchanged, but joint access, preheat, and heat input documentation deserve extra attention
Weld before pretensioning bolts to protect clamp force integrity
Inspect for weld spatter on faying surfaces and verify sequence compliance in the inspection record
Assemble a closeout package that covers both welding and bolting documentation for the hybrid connection
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FAQ
Frequently asked.
Can bolts and welds share load in the same structural connection?
Only in specific conditions defined by AISC 360. Generally, bolts and welds cannot share load in new construction unless the bolts are fully pretensioned (slip-critical or bearing condition per AISC J1.8). In practice, hybrid connections are uncommon in moment-critical joints but do appear in heavy splice and transfer-girder applications.
Does welding near high-strength bolts require a different WPS?
No—the same AWS D1.1 WPS applies. However, the WPS should document any restrictions on heat input, preheat, or interpass temperature that apply to protect the base metal adjacent to pretensioned fasteners. For Q&T steels, interpass temperature limits are already mandatory.
Does the sequence matter—weld first or bolt first?
Yes. AISC recommends welding before final bolt tensioning in most hybrid applications. Welding after bolts are fully pretensioned can relax bolt tension due to thermal cycling. If the sequence is reversed, re-verification of bolt tension after welding is typically required.
What does the CWI inspect differently on a hybrid connection?
Beyond standard AWS D1.1 weld acceptance criteria, the CWI should verify the welding sequence was followed, document that preheat was achieved on the base metal near the bolt holes, and check for weld spatter on the faying surfaces or in the bolt threads. Any spatter that compromises bolt seating or thread engagement is a nonconformance.