Which steel shapes trigger the AWS D1.1 Clause 5.4 heavy section requirements?

AISC Group 4 and Group 5 hot-rolled shapes and plates 2 in [50 mm] or thicker in the through-thickness direction of a CJP weld trigger Clause 5.4. Common examples include W14×257 and heavier column sections.

Do I need extra CVN testing of the base metal itself when welding Group 4/5 shapes?

Yes. AWS D1.1 Clause 5.4 requires the steel producer to provide CVN test results for the core of thick Group 4/5 flanges and plates, typically 20 ft-lb at 70°F minimum. This supplements, not replaces, the filler metal CVN requirements.

Can a prequalified WPS be used for CJP welds on Group 4/5 shapes?

A prequalified WPS satisfying the process and preheat requirements of Clause 5 may be used, but you must also satisfy all Clause 5.4 supplementary requirements—reduced weld access holes, backing removal, low-hydrogen process—before the WPS is fully compliant.

Why are weld access holes required to be larger for heavy sections?

Larger access holes (reduced-area geometry per Clause 5.4) reduce restraint and allow the welder to see and clean the root area. The standard access hole dimensions in prequalified joints can leave tri-axial stress concentrations in heavy sections that promote lamellar tearing and hydrogen cracking.

AWS D1.1 Group 4/5 Heavy Section CJP Weld Requirements

AWS D1.1 Clause 5.4 imposes extra requirements on CJP welds in AISC Group 4 and Group 5 heavy shapes: base metal CVN testing, reduced weld access holes, and strict low-hydrogen controls.

Heavy sections in moment-resisting frames, transfer girders, and heavily loaded column splices represent the highest-consequence welds in structural fabrication. AWS D1.1:2025 Clause 5.4 imposes a layer of requirements on top of the normal prequalified or qualified-by-test WPS rules specifically for these joints. Skipping them is a common audit finding—and a genuine fracture risk.

What Triggers Clause 5.4

The trigger is geometric, not process-based. AWS D1.1:2025 Clause 5.4 applies when you make a complete joint penetration (CJP) groove weld in either of two configurations:

AISC Group 4 or Group 5 hot-rolled shapes — the flange or web that receives the CJP is from these heavier sections.
Plates 2 in [50 mm] thick or greater loaded in the through-thickness direction at the weld.

The reason is well established: the core of a thick flange or plate cools more slowly, and rolled steel is not homogeneous through its thickness. CVN toughness at mid-thickness is consistently lower than at the surface; segregation of sulfur and phosphorus at the plate centerline increases lamellar tearing risk; and the tri-axial stress state in a restrained heavy joint limits the material's ability to redistribute stress plastically.

AISC Group 4 shapes start at approximately W14×233 (for W14), W12×210, W24×370, and similar—any W, S, or HP shape whose flange thickness exceeds roughly 1½ in. Group 5 includes the heaviest wide-flange columns such as W14×550 through W14×873. Your structural drawings should identify Group 4/5 shapes; if they do not, check AISC Table 1-1.

Base Metal CVN Requirement

The most overlooked Clause 5.4 provision is the base metal CVN requirement. When the steel is to be welded to a CJP joint under these conditions, the material certification (MTR) must include CVN test results from specimens taken at the core of the flange or plate—not just the surface—demonstrating at minimum 20 ft-lb [27 J] absorbed energy at 70°F [21°C].

This is not automatically on a standard ASTM A992 or A572 MTR. You must:

Order the heats with this test required, or
Verify the MTR explicitly states core CVN values, or
Have the material certified to ASTM A6 Supplementary Requirement S30, which covers core CVN for Group 4/5 shapes.

If the MTR is silent on core CVN, the material is not in compliance with Clause 5.4 for CJP joints. The time to discover this is during material receiving inspection—not during the AISC certification audit. See also CMT/MTR review during CWI pre-weld inspection and through-thickness testing for heavy weld joints.

Weld Access Hole Geometry

Standard prequalified weld access holes (cope cuts) may not be used on Group 4/5 sections welded for seismic or other demand-critical connections. AWS D1.1:2025 Clause 5.4 specifies a reduced-area weld access hole geometry:

Minimum height equal to 1½ times the flange thickness tf, but not less than 1 in [25 mm]
Minimum horizontal length from the face of the web equal to the greater of 1½ tf or 1 in [25 mm]
The corner radius shall be no less than ½ in [13 mm] and shall be smooth, free of notches, and ground

This geometry distributes the stress concentration more evenly and gives the welder room to deposit a sound root pass. Access holes cut with a plasma or oxy-fuel torch must meet the thermal cut surface quality requirements of Clause 5.14; grinding is required wherever roughness or hardness exceeds Code limits.

The quality of the access hole surface itself is subject to CWI inspection before welding begins. A sharp notch at the corner, a drag line left by a dulled plasma nozzle, or a residual arc strike from a misplaced tack weld are all nonconformances that must be repaired before the production weld begins.

Low-Hydrogen Process and Preheat

Clause 5.4 requires a low-hydrogen welding process. The four commonly used in structural fabrication—SMAW with low-hydrogen (H8 or lower) electrodes, FCAW-G, GMAW (spray or pulse), and SAW—all qualify. SMAW with E6010 cellulosic root passes does not qualify by itself, even if it is allowed elsewhere as a root process, because E6010 is not classified as low-hydrogen.

Minimum preheat and interpass temperature for Group 4/5 CJP welds under Clause 5.4 is 70°F [21°C] regardless of plate thickness, and this must be maintained throughout the weld cycle. For most structural carbon and HSLA steels at these thicknesses, Table 6.3 will drive the preheat higher—Clause 5.4 sets the floor, not the ceiling. Verify preheat using contact thermometers or temperature-indicating crayons at a point at least 3 in [75 mm] from the joint on each side. See preheat temperature measurement methods for CWI structural welding for measurement technique.

Steel Backing Removal

For CJP groove welds made with steel backing bars—the most common configuration in column splice and moment connection details—Clause 5.4 requires the backing to be removed after welding. The root must then be back-gouged to sound metal and the resulting cavity filled with weld metal.

Why? Steel backing left in place creates a crevice at the root that can act as a fatigue initiation site under cyclic loading and traps hydrogen in high-restraint conditions. Seismic connections and demand-critical welds in moment frames nearly always see this requirement extended by AWS D1.8 and AISC 341 as well.

The weld procedure must specify backing removal, the back-gouging method, and the filler metal and passes used to fill the gouge. This is a common WPS omission on column splice details: the WPS covers the CJP groove weld with backing but is silent on the backing removal and fill pass.

Documentation in the WPS Package

A Clause 5.4-compliant WPS package for a Group 4/5 section CJP joint should contain:

The WPS itself, noting the low-hydrogen process designation and H-suffix electrode classification
The PQR (if tested) or the prequalified WPS listing with Clause 5.4 acknowledgement
A material note on the drawing or in the WPS body specifying core CVN ≥ 20 ft-lb at 70°F per Clause 5.4
The access hole detail—either a dimensioned sketch on the connection detail or a reference to Clause 5.4 geometry
A note that steel backing is to be removed and back-gouged after welding

At AISC Category I, II, or III audits, the CWI or QC manager is expected to walk the auditor through how Clause 5.4 is enforced on these joints. Having a written QC plan that identifies Group 4/5 connections as a hold-point category, with the CWI signing off on base metal certification before fit-up, is the clearest demonstration of control.

Interaction With AWS D1.8 Seismic Supplement

When the project also invokes AWS D1.8 for demand-critical welds—column splices in special moment frames, for example—the D1.8 requirements overlay and in some cases supersede Clause 5.4 minimums. D1.8 requires CVN-rated filler metal at the toughness levels specified in Table 5.1, written removal and repair procedures for backing, and mockup qualification for some connection geometries. See AWS D1.8 demand-critical WPS requirements and reduced beam section connection weld procedures under D1.8 for the full seismic overlay.

Checklist for the Fabricator QC Program

Before the first arc is struck on a Group 4/5 CJP joint:

MTR on file showing core CVN ≥ 20 ft-lb at 70°F for each heat of material
WPS designates a low-hydrogen process with H-classified electrode
Access hole geometry dimensioned per Clause 5.4, cut surface inspected by CWI
Minimum preheat of 70°F confirmed; Table 6.3 preheat also verified for the actual base metal chemistry
WPS includes backing removal and back-gouge fill procedure
CWI sign-off required at fit-up hold point before first pass

Getting these items into your project QC plan before the steel hits the floor is the surest way to avoid a stop-work order from the owner's verification inspector.

Rule library based on AWS D1.1:2025. Verify against your governing edition—your contract or AHJ may specify 2020 or an earlier edition.

For a full WPS workflow—from material verification through final NDE documentation—explore the WPS generator and qualification tools at wpswelding.com.