Reading an Intermittent Fillet Symbol on a Bracket Detail
A fabricator is building a support bracket. On the detail for the bracket-to-column joint, the arrow-side fillet symbol carries '3/8' to the left and '4-12' to the right. The other-side symbol carries '1/4' with no length. The joint runs 44 in along the column, and the tail of the symbol notes 'AWS D1.1.' Working from a third-generation photocopy on which the other-side symbol is faint, the welder runs a continuous 1/4 in fillet the full 44 in on the near side only. He says the far side is inaccessible because of a stiffener plate, and that 'the 3/8 on the drawing is the throat, so a 1/4 leg is close enough.' The inspector has a fillet weld gauge, the controlled drawing and a copy of AWS D1.1, and must decide whether to accept, rework or reject the joint before the bracket is erected Monday.
1. Interpret the symbol exactly as written: size, length, pitch and side for both welds.
Read the worked answer
Reference line with two fillet symbols, one on each side of the line.
Arrow side: fillet, size 3/8 in leg (the dimension to the left of the weld symbol is the leg for a fillet), length 4 in, pitch 12 in - intermittent, 4 in of weld on 12 in centers.
Other side: fillet, size 1/4 in leg, and no length shown. The absence of a length means the weld runs the full length of the joint, so a continuous 1/4 in fillet for the full 44 in.
The tail reference to AWS D1.1 means that code supplies the acceptance criteria and the workmanship requirements, and the WPS for the joint must be qualified to it. The symbol says what to build; the code says whether what was built is acceptable.
2. Over the 44 in joint, how much arrow-side weld does the drawing require? Was the welder's continuous near-side pass a substitute?
Read the worked answer
At 12 in pitch, 4 in long, the segments start at 0, 12, 24 and 36 in, giving four segments and 16 in of weld over the 44 in joint. Intermittent welds are normally placed so the joint is welded at its ends, which this layout does.
The welder's continuous 44 in pass is not a substitute for two reasons. First, it exceeds the required length but is undersize: 1/4 in leg where 3/8 in is specified. Second, and worse, the 1/4 in other-side weld is required continuous over the full 44 in and is entirely missing. Length cannot compensate for missing weld on the opposite side: the bracket load has to transfer through both legs of the joint, and the designer specified continuous weld there deliberately.
So the joint is nonconforming on both counts - undersize on the near side and absent on the far side. Continuous rather than intermittent welding on the near side is not itself a defect, but it does add distortion and cost and was not what the detail required.
3. Is the welder's '3/8 is the throat' claim correct? What must be measured, and what should happen about the claimed inaccessibility?
Read the worked answer
The claim is wrong. In AWS welding symbols, the number to the left of a fillet weld symbol is the leg size, not the throat. The effective throat of a fillet is the leg multiplied by 0.707, so a 3/8 in leg fillet gives an effective throat of about 0.265 in, and the 1/4 in leg the welder deposited gives about 0.177 in - roughly two-thirds of the required throat. That is a strength deficiency, not a cosmetic one, and it is objectively measurable.
The inspector measures leg size with the fillet weld gauge at several points along the joint, checks weld length and pitch against the symbol, checks for the other-side weld, and records measurements. Undersize beyond what the code tolerates is a rejectable discontinuity and the joint must be reworked, not accepted on the welder's assurance.
On access: if the stiffener genuinely blocks the far side, that is a conflict between two details on the drawing. The fabricator raises an RFI to the engineer of record and gets a documented disposition - sequence the bracket before the stiffener, notch or cope the stiffener, or obtain approval for a revised weld. A welder cannot unilaterally delete a specified weld because a detail is inconvenient, and the welder should not be working from a faint third-generation photocopy; the controlled, legible drawing is the only basis for fabrication.