Distortion and Fit-Up in a Curved Girder Splice
A shop is splicing two field sections of a horizontally curved plate girder. The specified splice is a complete-joint-penetration groove weld with a backing bar. Fit-up shows a root gap varying from 1/16 in. to 3/8 in. along the 4 ft splice length because of accumulated camber and curvature tolerance stack-up. The fabricator wants to close the gap by pulling with strongbacks and welding as-is. Ambient is 70 F. The girder has a 1-1/4 in. flange and 3/4 in. web. The EOR's splice detail shows a nominal 1/4 in. root gap with a specific groove angle. The inspector must decide whether to permit welding, require re-fit, or require a revised detail.
1. Evaluate the root gap variation against the qualified WPS and the splice detail.
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The qualified WPS and the splice detail define a nominal root gap and a groove angle; root gap is an essential variable for groove welds. A gap ranging from 1/16 in. to 3/8 in. exceeds the nominal 1/4 in. at both extremes. A 1/16 in. gap risks incomplete fusion at the root; a 3/8 in. gap changes the weld volume, heat input, and shrinkage, and may exceed the WPS range. Welding as-is is not supportable without a WPS that brackets the actual gap or an EOR-approved revised detail. The inspector should require re-fit to the specified gap or a documented, approved deviation.
2. The fabricator proposes strongback pulling to close the gap. Assess this under D1.5 fit-up and distortion provisions.
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Forced fit-up by strongbacks introduces residual stress and can induce cracking, particularly in thick sections and complete-joint-penetration welds. D1.5 limits the amount of forced alignment and requires that members not be restrained in a way that produces excessive stress. Pulling a 3/8 in. gap closed over a 4 ft length imposes significant localized strain at the splice. The correct approach is to correct fit-up by re-fit or by adjusting the splice geometry, not by pulling. If any pulling is used, it must be within permitted limits and released before or during welding as specified, and the inspector should verify the limits.
3. If the EOR approves a revised detail with a wider groove, what must the fabricator demonstrate before production welding?
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A revised groove detail changes essential variables - groove angle, root gap, and weld volume - so the fabricator must demonstrate that the WPS covers the revised geometry or qualify a new procedure. The revised detail should be documented by the EOR with a revised drawing, and the fabricator should provide the WPS, procedure qualification, and welder qualification for the revised joint. Preheat and interpass must be confirmed for the 1-1/4 in. flange. The inspector should verify that the revised detail, WPS, and qualification are consistent before permitting production welding, and should record the deviation and approval.