Fillet Weld Size on a Skewed Bent Cap Connection
A fabricator is welding a continuity diaphragm between a precast bent cap and a steel plate girder on a 30-degree skew. The EOR's detail shows a 5/16 in. fillet on both sides of a 3/4 in. stiffener plate lapped to a 1 in. web. During first-article inspection, the CWI measures the as-built fillet leg on the acute-angle side at 3/16 in. and finds the obtuse-angle side at 3/8 in. The fabricator argues that the throat, not the leg, governs and that both welds meet the drawing. Shop ambient is 45 F with no preheat applied to the 1 in. web (A709 Gr. 50). The inspector must decide whether to accept, rework, or reject before the unit ships.
1. Evaluate whether the as-built fillet leg dimensions satisfy the contract requirement, and identify what governs fillet size on skewed joints.
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The drawing calls for a 5/16 in. fillet, and fillet weld size is measured by leg length, not throat. A 3/16 in. leg on the acute side is undersized against a 5/16 in. requirement and must be rejected regardless of throat. The obtuse side at 3/8 in. exceeds the required leg but does not compensate, because each side is evaluated independently. On skewed T-joints the effective throat is reduced relative to the leg, so the detailer must specify the leg that produces the required throat on the acute side; the fabricator cannot reinterpret the callout. The correct disposition is to reject the acute-side weld and repair by adding a fillet of sufficient size, with the joint prepared so the added weld meets the minimum leg. Document the measurement locations and the repair.
2. Given 45 F ambient, 1 in. thick A709 Gr. 50, and no preheat, what does D1.5 require before welding, and does this affect your disposition?
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A 1 in. web is well above the thickness threshold at which preheat becomes mandatory for Gr. 50 steel, and 45 F ambient is below the minimum permissible base-metal temperature for welding without preheat. D1.5 requires the base metal to be at or above a specified minimum temperature before welding, with preheat increasing as thickness and carbon equivalent rise. At 45 F and 1 in. thickness, welding without preheat is a procedure nonconformity independent of the leg-size issue. The disposition therefore has two parts: reject the undersized acute-side fillet, and treat the joint as welded outside qualified conditions. The fabricator must demonstrate that the WPS preheat requirements were met or perform remediation per the EOR; the inspector should not accept the unit on the basis of leg size alone.
3. The fabricator proposes to grind the obtuse-side weld flush and re-weld both sides to 5/16 in. leg. Assess this repair approach.
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Grinding the obtuse-side weld flush removes sound weld metal and reduces the effective throat at the very location where skew already reduces it; that is counterproductive. The undersized location is the acute side, so the repair should add leg there, not remove material from the obtuse side. Re-welding both sides to 5/16 in. leg is acceptable only if the added weld on the acute side achieves the required leg without exceeding the maximum single-pass size for the process, and if preheat is applied throughout. The inspector should require a repair WPS or a qualified procedure covering preheat, and verify leg after repair. Grinding sound weld for cosmetic symmetry is not justified.