What is a column tree in structural steel fabrication?

A column tree is a shop-fabricated assembly where beam stubs are pre-welded to the column flanges in the shop, leaving only splice welds to be made in the field. This approach moves the highest-quality, demand-critical welds from the field into the controlled shop environment.

Do column tree shop welds require AWS D1.8 or AWS D1.1?

Both apply. AWS D1.8 supplements AWS D1.1 for seismic applications. D1.8 imposes additional filler metal CVN requirements, specific preheat minimums, and supplementary essential variable testing (Table 6.8) that are not in D1.1 alone. The WPS must comply with both codes simultaneously.

What filler metal CVN requirements apply to demand-critical column tree welds?

AWS D1.8 and AISC 358 require filler metals meeting minimum CVN values at both 0°F (−18°C) and −20°F (−29°C) depending on the connection type and risk category. Confirm with the demand-critical weld schedule on the connection design drawings; don't guess from D1.1 alone.

Can a prequalified WPS cover column tree continuity plate welds?

Only if the joint details match a prequalified configuration under AWS D1.1 Clause 3 (and AWS D1.8 Clause 4 for seismic). Continuity plate CJP groove welds in heavy plate often fall outside prequalified limits on plate thickness or joint access, requiring a PQR-backed qualified WPS.

Nov 11, 20266 min read

Column Tree Shop Weld WPS: AISC 358 and AWS D1.1

How to qualify and document WPS for shop-fabricated column tree assemblies in SMF and IMF projects, covering demand-critical welds, continuity plates, and AISC 358 coordination.

WPS AISC 358 AWS D1.8 demand-critical welds seismic column tree SMF

New to procedures? Start with WPS welding: what a welding procedure specification is, with a filled-in example.

Column trees move the most critical welds in a special moment frame (SMF) or intermediate moment frame (IMF) off the iron at elevation and into the shop. That is the whole point: groove welds in a moment connection made flat or horizontal in a controlled environment, with preheat monitored by a CWI rather than on a cold column in a stiff breeze thirty feet up. The tradeoff is complexity—shop WPS documentation for column tree welds must satisfy AWS D1.1, AWS D1.8, and AISC 358 at once, and the interplay between those three documents trips up fabricators who treat the WPS as a D1.1-only exercise.

What a Column Tree Assembly Contains

A column tree typically includes a length of wide-flange column with beam stubs shop-welded to both flanges at each floor level. Each beam stub ends at a splice location clear of the connection panel zone—often at a point one-quarter to one-third of the span from the column face, depending on the moment frame connection type per AISC 358. The shop welds in the assembly include:

Beam stub-to-column flange CJP groove welds — the demand-critical (D-C) welds that absorb seismic energy during a design earthquake
Continuity plate CJP or complete-joint-penetration fillet groove welds — transverse stiffeners aligned with the beam flanges to distribute force through the column panel zone
Doubler plate fillet welds — if the panel zone requires shear reinforcement per AISC 360 Equation J10-9 or the connection design

Each weld type has different WPS requirements, and they must all appear on the same WPS submittal package for the EOR's review before fabrication starts.

WPS Qualification Requirements for Demand-Critical Welds

The WPS for the beam stub-to-column flange CJP groove welds must be qualified under AWS D1.8 as well as AWS D1.1. AWS D1.8 imposes supplementary essential variables beyond those in D1.1 Table 6.6. When CVN impact testing requirements are invoked—which they always are for D-C welds in SDC D, E, or F buildings—the variables in AWS D1.1 Table 6.8 become essential. A change in any of those variables requires requalification with a new PQR that includes Charpy V-notch testing of the weld metal and heat-affected zone.

The specific variables that catch shops off guard include:

Heat input limits. AISC 358 connection prequalification conditions and AWS D1.8 place upper limits on heat input (kJ/in) for DC welds. If your production procedure runs at a higher travel speed or wire feed rate than what the PQR captured, the heat input may change enough to trigger requalification. Document the heat input range on the WPS explicitly—calculate it from the arc energy formula (amperage × voltage × 60 ÷ travel speed in in/min) and show the minimum and maximum values your process envelope produces.

Filler metal hydrogen designation. AWS D1.8 requires a minimum hydrogen designator (typically H8 or lower) for D-C weld filler metals. If your stock FCAW-G wire is designated H16, it doesn't qualify regardless of the wire's AWS A5.20 or A5.36 classification. Verify the specific wire lot's certified diffusible hydrogen level before writing it into the WPS. See diffusible hydrogen filler metal requirements under AWS D1.1 for background on the designator system.

Preheat and interpass temperature. AISC 358 connection prequalification sections specify minimum preheat temperatures that may exceed the AWS D1.1 Table 5.11 minimums for the same steel group. The WPS must state the AISC 358 or D1.8 minimum, not the lower D1.1-only value.

Continuity Plate Weld WPS

Continuity plate groove welds—where they are CJP rather than PJP per the connection design—often require a separate WPS because the joint geometry differs from the beam stub flange weld. The access conditions are different: the weld is made inside the column flanges, and the K-zone of the wide-flange column may limit weld torch angle and position.

For A992 wide-flange columns, the weld access hole geometry must conform to AISC 358 requirements for the specific connection type. Undersized or non-standard access holes change the joint root opening and can push the detail outside the prequalified joint configuration, requiring PQR qualification. Document the access hole dimensions on the WPS or the accompanying joint design detail—the EOR cannot verify compliance from the AWS D1.1 Annex J Form J-1 WPS form alone.

If continuity plate welds are classified as demand-critical (the engineer of record should state this on the structural drawings), the same CVN and hydrogen designation requirements apply. If they are non-DC, standard D1.1 Table 6.6 essential variables govern and the full D1.8 layer is not required.

Doubler Plate Fillet Weld WPS

Doubler plate fillet welds are typically non-demand-critical. A prequalified WPS under AWS D1.1 Clause 3 is usually achievable here, provided the fillet size meets the minimum for the plate thickness (Table 7.7, based on the thinner part for low-hydrogen processes) and the joint fits within prequalified fillet weld details.

Watch the minimum fillet size: doubler plates in heavy column sections can be 1 in. thick or more. For plate thicknesses over 3/4 in., the Table 7.7 minimum fillet size is 5/16 in. Document this clearly on the WPS. Undersized fillet welds on doubler plates are a common finding in AISC certification audits because the weld looks acceptable visually but the leg size doesn't meet the Table 7.7 minimum. See minimum fillet weld size requirements under AWS D1.1 Table 7.7 for the full table.

Submittal Package to the EOR

A complete column tree WPS submittal package for the EOR's review should include:

WPS documents (Annex J Form J-1 or equivalent) for each weld type in the assembly
Supporting PQRs with CVN test data for demand-critical WPS qualifications
Filler metal certifications with diffusible hydrogen designators
The demand-critical weld schedule (which welds are D-C vs. non-DC), if the fabricator is developing it rather than receiving it from the structural drawings

AISC 303 requires the fabricator to submit WPS documentation for review before welding begins. The EOR cannot approve a D-C weld WPS that lacks the CVN data or uses the wrong hydrogen designation—and an unqualified D-C weld discovered in the final inspection audit means destructive retesting and potentially weld removal.

Practical Shop Sequencing

The order of welds in a column tree assembly affects distortion and final straightness. For SMF assemblies where column plumbness tolerances are tight, most shops follow a balanced welding sequence: stiffener welds before beam stub welds, beam stubs welded in alternating passes on opposing sides of the column, and final inspection before the assembly cools.

Preheat must be maintained throughout the sequence. For A992 W-shapes in the Group IV/V range, preheat requirements can be 150°F to 225°F (65°C to 107°C) or higher depending on the governing requirements of AISC 358 and the connection design package. Interpass temperature limits apply too—AISC 358 and AWS D1.8 place maximum interpass temperatures on D-C welds that are more restrictive than a plain D1.1 WPS might show. See interpass temperature limits for structural welding for verification methods.

Why This Matters for Your WPS Library

Column tree projects are typically large-contract jobs—multi-story commercial or industrial frames where the engineer of record is enforcing D1.8 rigorously and the AISC certification auditor will check the weld documentation. A WPS library built only for standard D1.1 work may be missing the CVN-tested PQRs and the D1.8-compliant hydrogen designations needed to start fabrication. Getting the WPS package right before the first arc is struck is far cheaper than a failed audit midway through the job.

If you need to build or audit your WPS library for seismic moment frame work, wpswelding.com/pricing shows the plan options for managing qualified WPS, PQR, and welder qualification records in one system.

Rule library based on AWS D1.1:2025; verify against your governing edition. AISC 358 and AWS D1.8 requirements vary by connection type and seismic design category—confirm with the project structural drawings.

FAQ

Frequently asked.

What is a column tree in structural steel fabrication?: A column tree is a shop-fabricated assembly where beam stubs are pre-welded to the column flanges in the shop, leaving only splice welds to be made in the field. This approach moves the highest-quality, demand-critical welds from the field into the controlled shop environment.
Do column tree shop welds require AWS D1.8 or AWS D1.1?: Both apply. AWS D1.8 supplements AWS D1.1 for seismic applications. D1.8 imposes additional filler metal CVN requirements, specific preheat minimums, and supplementary essential variable testing (Table 6.8) that are not in D1.1 alone. The WPS must comply with both codes simultaneously.
What filler metal CVN requirements apply to demand-critical column tree welds?: AWS D1.8 and AISC 358 require filler metals meeting minimum CVN values at both 0°F (−18°C) and −20°F (−29°C) depending on the connection type and risk category. Confirm with the demand-critical weld schedule on the connection design drawings; don't guess from D1.1 alone.
Can a prequalified WPS cover column tree continuity plate welds?: Only if the joint details match a prequalified configuration under AWS D1.1 Clause 3 (and AWS D1.8 Clause 4 for seismic). Continuity plate CJP groove welds in heavy plate often fall outside prequalified limits on plate thickness or joint access, requiring a PQR-backed qualified WPS.