Structural welding procedures under AWS D1.1 specify every detail of every weld on a structural steel project: the joint geometry, filler metal classification, preheat temperature, interpass temperature, and welding parameters. Prequalified procedures cover most standard joint configurations and save you the cost of procedure qualification testing. If the joint matches a prequalified detail in the code, document it as a written WPS and start welding.
AWS D1.1 Prequalified Welding Procedure Specifications
AWS D1.1 provides prequalified joint details for common structural connections. A prequalified WPS uses these pre-validated joint geometries combined with approved filler metals and welding parameters. The advantage is significant: no procedure qualification record (PQR) is required, which means no test coupons, no destructive testing, and no waiting for results.
To use a prequalified WPS, every variable must fall within the code’s prequalified limits:
| Variable | Prequalified Requirements |
|---|---|
| Welding Process | SMAW, SAW, GMAW (except short-circuit), FCAW |
| Base Metal | Listed in D1.1 Table 5.3 (Groups I through IV) |
| Filler Metal | Matching strength per D1.1 Table 5.1 |
| Preheat/Interpass | Per D1.1 Table 5.8 based on thickness and process |
| Joint Details | Per D1.1 Figures 5.1-5.4 (prequalified geometries) |
| Position | All positions for applicable process |
If any variable falls outside the prequalified range, the procedure must be qualified by testing per AWS D1.1 Section 6. This includes non-standard joint designs, unlisted base metals, or processes not included in the prequalified list (such as short-circuit GMAW, which requires separate qualification).
Writing a Prequalified WPS
Every prequalified WPS must be documented in writing before production welding begins. The written WPS includes:
- Joint design details (bevel angle, root opening, root face, backing type)
- Base metal specification and thickness range
- Filler metal classification and diameter
- Shielding gas type and flow rate (for GMAW and FCAW)
- Electrical characteristics (current type, polarity, amperage range, voltage range)
- Travel speed range
- Preheat and interpass temperature requirements
- Post-weld heat treatment (if applicable)
- Position(s) of welding
- Single or multi-pass designation
The WPS is a shop floor document. It tells the welder exactly how to make the weld. Keep it clear, specific, and accessible at the welding station.
Complete Joint Penetration (CJP) Groove Welds
CJP groove welds fuse completely through the joint thickness. They develop the full strength of the connected members and are required wherever the design demands complete load transfer across the joint.
Where CJP Welds Are Required
- Moment frame beam-to-column flange connections
- Column splices in tension zones
- Butt splices in tension members
- Connections designated as demand-critical under AWS D1.8
- Any joint where the engineer specifies full-strength connection
CJP Joint Configurations
The most common CJP joint in structural steel is the single-V groove with backing bar. The backing bar (typically 1/4 x 1 inch steel flat bar) bridges the root opening and supports the first weld pass. The welder fills the joint from one side, and the backing bar prevents blow-through.
| CJP Joint Detail | Bevel Angle | Root Opening | Backing | Common Application |
|---|---|---|---|---|
| Single-V with backing | 45-60 degrees | 1/4 in | Steel backing bar | Beam flange to column, field splices |
| Double-V | 45-60 degrees each side | 0 to 1/8 in | None (welded both sides) | Shop splices, thick plate connections |
| Single-bevel with backing | 45 degrees | 1/4 in | Steel backing bar | T-joints, corner joints |
| Single-V without backing | 60 degrees | 1/4 in | Back-gouged and back-welded | Demand-critical welds (seismic) |
For demand-critical welds under AWS D1.8, the backing bar is removed after welding, the root is back-gouged to sound metal, and a back-weld reinforces the joint from the second side. This eliminates the stress concentration and potential crack initiation point at the backing bar notch.
Partial Joint Penetration (PJP) Groove Welds
PJP groove welds penetrate only to a specified depth, not through the full joint thickness. The effective throat of a PJP weld is less than the base metal thickness, so the joint develops less than the full strength of the connected members.
Where PJP Welds Are Acceptable
PJP welds work for connections where the applied loads don’t require full member strength:
- Column splices in compression (bearing connections)
- Web-to-flange welds on built-up members (some configurations)
- Non-critical attachments and stiffeners
- Connections where the engineer’s calculations show PJP is adequate
PJP Effective Throat
The effective throat of a PJP groove weld depends on the joint configuration and welding process:
| Joint Configuration | Effective Throat (SMAW, GMAW, FCAW) | Effective Throat (SAW) |
|---|---|---|
| Single-V groove (60 degrees or more) | Depth of groove minus 1/8 in | Depth of groove |
| Single-V groove (45-59 degrees) | Depth of groove minus 1/8 in | Depth of groove minus 1/8 in |
| Single-bevel groove (60 degrees or more) | Depth of groove minus 1/8 in | Depth of groove |
| J or U groove | Depth of groove minus 1/8 in | Depth of groove minus 1/8 in |
The 1/8-inch reduction accounts for the possibility of incomplete fusion at the root of the joint. SAW gets credit for the full groove depth on wider-angle joints because the high heat input and deep penetration of submerged arc produces more reliable root fusion.
Fillet Weld Sizing
Fillet welds are the most common weld type in structural steel fabrication. They join two surfaces at approximately right angles (T-joints, lap joints, corner joints) without requiring a groove preparation.
Minimum Fillet Weld Size
AWS D1.1 specifies minimum fillet weld sizes based on the thickness of the thicker member being joined:
| Thickness of Thicker Part | Minimum Fillet Weld Size |
|---|---|
| Up to 1/4 in (6 mm) | 1/8 in (3 mm) |
| Over 1/4 to 1/2 in (6-12 mm) | 3/16 in (5 mm) |
| Over 1/2 to 3/4 in (12-20 mm) | 1/4 in (6 mm) |
| Over 3/4 in (20 mm) | 5/16 in (8 mm) |
These are code minimums. The engineer specifies the required fillet weld size based on the applied loads. The welder is responsible for meeting the specified size, not just the code minimum.
Fillet Weld Effective Throat
The strength of a fillet weld is calculated using the effective throat dimension, which is the shortest distance from the root of the joint to the face of the weld. For equal-leg fillet welds, the effective throat equals 0.707 times the leg size. A 5/16-inch fillet weld has an effective throat of approximately 0.221 inches.
Maximum Single-Pass Fillet Weld Size
In the horizontal position, the maximum single-pass fillet weld is typically 5/16 inch. Larger fillets require multiple passes. In the flat position, 3/8-inch single-pass fillets are achievable with higher deposition processes like FCAW or SAW.
Visual Inspection Acceptance Criteria
Every structural weld gets a visual inspection. AWS D1.1 Table 8.9 defines the acceptance criteria for visual inspection of statically loaded and cyclically loaded structures.
| Discontinuity | Statically Loaded | Cyclically Loaded |
|---|---|---|
| Cracks | Not permitted | Not permitted |
| Incomplete Fusion | Not permitted | Not permitted |
| Crater Cracks | Not permitted | Not permitted |
| Undercut (depth) | Less than or equal to 1/32 in | Less than or equal to 0.01 in for primary, 1/32 in for secondary |
| Porosity (CJP groove) | No visible piping porosity, sum of visible porosity less than or equal to 3/8 in per inch of weld | No visible piping porosity, no visible porosity |
| Porosity (fillet) | Sum less than or equal to 3/8 in per inch of weld, max individual 3/32 in | No visible piping porosity, no visible porosity |
| Weld Profile | Per D1.1 Figure 7.4 | Per D1.1 Figure 7.4 |
| Fillet Weld Size (undersize) | Max 1/16 in undersize for 10% of weld length | Max 1/16 in undersize for 10% of weld length |
Cyclically loaded structures (bridges, crane runways, structures subject to fatigue) have tighter acceptance criteria than statically loaded structures (most buildings). The engineer of record specifies which loading condition applies.
Welder Qualification Under D1.1
Qualification Test Types
AWS D1.1 requires welders to pass performance qualification tests on the specific joint types and positions they’ll use in production. The qualification test must use the same process, electrode type, and position as the production work.
| Test Type | Qualifies For |
|---|---|
| 3G (vertical plate) | Flat, horizontal, and vertical groove welds on plate |
| 4G (overhead plate) | Flat and overhead groove welds on plate |
| 3G + 4G combined | All position groove welds on plate |
| Fillet weld test | Fillet welds only, specific positions |
| 6G pipe (all positions) | All position groove and fillet welds on plate and pipe |
Plate vs. Limited Thickness Qualification
D1.1 qualifications include thickness limitations. Testing on 1-inch plate qualifies a welder for unlimited thickness. Testing on thinner material limits the qualification to twice the test plate thickness. Most structural welding qualification tests use 1-inch plate to get the unlimited thickness range.
CWI Witness Requirement
All D1.1 welder qualification tests must be witnessed by a Certified Welding Inspector (CWI) or an individual designated by the contractor and accepted by the Engineer. The CWI verifies that the test follows the WPS, inspects the completed test coupon, and witnesses or reviews the destructive test results.
Process Selection for Structural Steel
Structural steel welding uses several processes, each suited to specific applications:
FCAW-G (Gas-Shielded Flux-Core) is the dominant process in structural fabrication shops. High deposition rates (8-15 lb/hr in flat position), all-position capability with E71T-1 or E71T-8 wire, and good penetration make it the workhorse process. Shielding gas is typically 75% argon/25% CO2.
FCAW-S (Self-Shielded Flux-Core) dominates field erection work. The E71T-8 electrode generates its own shielding gas from the flux, eliminating the need for external gas supply. This makes it the preferred choice for outdoor work where wind disrupts gas coverage.
SAW (Submerged Arc) handles long, flat-position welds in the shop. Flange-to-web joints on plate girders, long butt splices, and continuous fillet welds are ideal SAW applications. Deposition rates of 15-40 lb/hr make SAW the fastest structural welding process.
SMAW (Stick) is used less frequently in modern structural work but remains common for small welds, repair work, and situations where other processes aren’t practical. E7018 is the standard structural stick electrode.
Understanding which process to apply where, and how to document each in a prequalified or qualified WPS, is fundamental to structural welding engineering and execution.
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