Does D1.8 replace AWS D1.1 for seismic work?

No. AWS D1.8 is a supplement — it extends D1.1, not replaces it. Both codes apply simultaneously. The structural engineer of record specifies which connections are demand critical; for those welds, D1.8 requirements layer on top of the D1.1 baseline.

Is self-shielded FCAW (FCAW-S) allowed for demand critical welds under D1.8?

AWS D1.8 restricts or conditions the use of FCAW-S for demand critical welds due to historical concerns about notch toughness variability and diffusible hydrogen. The specific restrictions depend on the edition of D1.8 in effect on the project. Always check the applicable edition before specifying FCAW-S for seismic connections.

What CVN values does D1.8 require for filler metals?

D1.8 requires filler metals for demand critical welds to meet specific absorbed-energy values at specified test temperatures. The exact values are stated in the supplement and must be verified from the filler metal manufacturer's CVN certification — not assumed from the electrode classification alone.

Do all welds in a seismic frame require D1.8 qualification?

No. D1.8 applies only to demand critical welds as defined by D1.8 and as designated in the project documents. Other welds in the same frame — non-demand critical connections, miscellaneous plates, brace gussets in non-seismic systems — remain governed by D1.1 only.

AWS D1.8 seismic supplement: extra WPS requirements

AWS D1.8 adds supplemental CVN and filler-metal requirements onto D1.1 for seismic moment frame welds. Here's what changes on your WPS and PQR.

AWS D1.8, Structural Welding Code — Seismic Supplement, extends the WPS and PQR requirements of AWS D1.1 for welds made on seismic force-resisting systems (SFRS). If your shop fabricates steel moment frames, eccentrically braced frames, or other AISC 341-governed systems, D1.8 is not optional — it applies alongside D1.1, not instead of it.

The supplement is short compared to D1.1, but its impact on the qualification program is significant. A procedure package that satisfies D1.1 fully may still fail a D1.8 review if the demand critical weld requirements weren't addressed.

What D1.8 adds that D1.1 doesn't cover

AWS D1.1 establishes the baseline: essential variables, mechanical test requirements, and workmanship provisions. D1.8 layers three additional dimensions onto that baseline.

Notch toughness requirements for filler metals. D1.1 has CVN supplementary essential variables under Table 6.8, but those apply only when the project invokes CVN testing. D1.8 mandates specific absorbed-energy values for filler metals used in demand critical welds — the welds expected to yield and dissipate energy during a seismic event. The CVN requirements under D1.8 specify test temperatures and minimum energy values that may be stricter than anything a generic electrode classification implies.

Restrictions on filler metal classifications. D1.8 restricts or conditions use of certain electrode types for demand critical welds. Self-shielded FCAW (FCAW-S) has historically been restricted because of concerns about notch toughness variability and diffusible hydrogen at low test temperatures. The specific restrictions have evolved across editions of D1.8; always check the current edition before specifying any electrode for seismic demand critical work.

Extended PQR testing. Qualifying a WPS for demand critical welds under D1.8 requires CVN testing on both the weld metal and the heat-affected zone (HAZ) of the PQR test plates, in addition to the tensile and bend tests required by D1.1. The test temperatures and acceptance criteria are stated in D1.8. This additional testing adds cost and lead time to the PQR program, and it must be planned before test plates are welded — not added retroactively.

Demand critical vs. non-demand critical welds

Not every weld in a seismic frame is demand critical. D1.8 defines specific weld categories subject to the supplemental requirements; other welds in the same structure remain governed by D1.1 only. The distinction matters because qualifying all shop welds to D1.8 demand critical requirements adds cost that isn't always necessary.

AISC 358 (prequalified moment connection standards) and AISC 341 (seismic provisions for structural steel buildings) specify which joints and which weld passes are demand critical. A complete moment connection procedure package — beam flange groove welds, continuity plate welds, doubler plate welds — has at least some demand critical elements and some non-demand critical elements. Sorting this out before writing procedures prevents unnecessary qualification cost while ensuring the critical welds are properly supported.

The structural engineer of record is the authoritative source on which welds are demand critical. Document that designation in the project quality plan so that inspectors can apply the right acceptance criteria to the right welds.

Weld access holes and geometry requirements

One of the more specific D1.8 provisions concerns weld access hole geometry in moment frame beam flanges. AWS D1.8 and AISC 358 specify the profile, radius, and surface condition of weld access holes in W-shape beams to reduce stress concentration at a location subject to significant cyclic demand.

These requirements override the general provisions in D1.1. Surface condition requirements specify how grinding is to be performed — including the required orientation of grind marks relative to the stress direction — and prohibit abrupt notches or tool marks. A shop accustomed to D1.1-only structural work may need additional fitment and inspection procedures to satisfy D1.8 access hole requirements. This is worth a dedicated procedure for any shop taking seismic work volume.

CVN essential variables and Table 6.8 interaction

When D1.8 mandates CVN qualification for a demand critical WPS, the essential variables from AWS D1.1:2025 Table 6.8 become active in addition to Table 6.6. Changes that would be acceptable under Table 6.6 alone — such as a modest heat input increase or a preheat adjustment — can trigger requalification under Table 6.8 when CVN testing is required.

This means the production WPS for demand critical welds has a tighter change envelope than a standard D1.1 procedure. Heat input limits, interpass temperature limits, and electrode classification are all harder to revise without going back to the PQR. For shops running seismic contracts, this argues for qualifying procedure ranges generously on the first PQR rather than qualifying to minimum ranges and hitting requalification triggers in production.

For more on the Table 6.8 essential variables and how they interact with the qualification program, see CVN Table 6.8 supplementary essential variables explained and PQR tensile and bend test requirements.

Documenting compliance on the WPS

A WPS written for demand critical seismic work should explicitly state:

That the WPS is qualified to AWS D1.1:2025 and AWS D1.8 for demand critical welds
The applicable AISC 358 connection type, if relevant
Filler metal CVN certification requirements (test temperature and minimum energy value) by heat number or lot certification
PQR reference including CVN test results and test temperature
Any weld access hole geometry requirements applicable to the connection

A WPS that states only "AWS D1.1" when D1.8 also applies is a finding in any competent AISC audit or third-party quality review. Explicit documentation of the D1.8 qualification path is part of the deliverable, not an administrative detail.

Building a D1.8 qualification strategy for a fab shop

For a shop that takes seismic work periodically, the most practical approach is to identify a procedure family — FCAW-G with a CVN-certified electrode on A992 material in a representative thickness range, for example — and qualify that family to D1.8 once. The PQR cost is a one-time investment; future demand critical welds in that family ride on the same qualification.

The critical enabling step is selecting filler metals with published heat number CVN certificates at the required test temperature. Not every electrode lot carries this documentation. Working with a filler metal distributor who can provide heat number traceability from the start of qualification prevents last-minute certificate chasing when the inspection team arrives before production welding begins.

For the baseline WPS qualification requirements that D1.8 extends, see how to qualify a welding procedure under AWS D1.1 and AWS D1.1:2025 Table 6.6 essential variables explained. To track multiple qualified procedures with their CVN qualification status, see pricing for WPS management platform options.

Rule library based on AWS D1.1:2025; verify against your governing edition and against the current edition of AWS D1.8. Seismic supplement requirements are project-specific and depend on the governing structural design standard.