The Copied Fillet Callout at a 45° Skewed T-Joint
A fabricator is detailing a pedestrian canopy at a transit station. The engineer's drawings show W10x49 beams framing into W14x90 columns at a 45° dihedral angle, with a 5/16 in fillet weld all around. The detailer copied the same 5/16 in fillet callout used at the 90° connections elsewhere on the job, and the shop has already cut and fitted the skewed members. The fabricator's WPS is a prequalified FCAW procedure, qualified on 3/8 in plate in the flat position with 1/16 in wire, and the assigned welder holds a current qualification. The owner's inspector arrives before welding starts and asks to see the detail, the WPS, and the basis for the weld size.
1. Is this 45° skewed T-joint with a 5/16 in fillet prequalified under D1.1? Walk through the conditions and identify which ones hold and which do not.
Read the worked answer
Prequalification is a package of conditions that must all hold simultaneously: a base metal listed as prequalified, a prequalified process and filler, a joint detail that matches a prequalified figure within its stated tolerances, and prequalified position and progression.
Here the base metal (A992/A36-type structural steel), the FCAW process with 1/16 in wire, and the welder are all on the acceptable side. The geometry is not. The code's prequalified skewed T-joint details cover a limited range of included/dihedral angles around the perpendicular case; a 45° skew falls outside that envelope, so the detail was never prequalified no matter how good the WPS is.
There is a second, independent problem. A skewed joint cannot deliver the throat of a 90° fillet with the same leg. As the angle departs from 90°, the effective throat shrinks (the familiar Z-loss), so the 5/16 in leg that is adequate at the 90° connections supplies less throat here. Before any arc is struck, the EOR must confirm the required throat, and the weld size must be derived from that throat rather than copied.
2. If the joint is not prequalified, what must the fabricator produce, and what should the inspector do with the fabricated members sitting on the floor?
Read the worked answer
With no prequalified route, the fabricator must write a WPS and qualify it by test under Clause 5. The test assembly has to reproduce the 45° dihedral, because joint geometry is an essential variable: the existing 3/8 in flat-position 90° PQR does not extend to a skewed joint, even though the filler metal classification is unchanged. The PQR should record the actual angle, the pass sequence, and the resulting throat achieved, and the welder must be qualified for the position and progression actually used.
The inspector's role is verification, not design. Practical sequence:
- Do not release the joint; state the code basis for the hold in writing.
- Issue an RFI/nonconformance asking the EOR to confirm required throat and accept a revised weld size.
- Require the WPS to be backed by a PQR covering the skew, and confirm welder qualification for the position.
- Record the correspondence and the eventual basis of acceptance in the inspection file.
Approving the detail because "it is just a fillet" would place acceptance on record with no code basis, and would leave the inspector holding a decision the EOR owns.