The Importance of Understanding AISC and AWS Codes
Following the requirements of codes and standards can save you significant dollars, create margin, and provide your firm with a quality reputation.
The “Why” of Codes and Standards
To start, let’s review the “why” behind codes and standards. The primary purpose of rules and requirements in these codes and standards is life safety. Contracts for fabrication and erection of structural steel reference the International Building Code (IBC), which fully adopts the American National Standards Institute/American Institute of Steel Construction (ANSI/AISC) 360-22, Specification for Structural Steel Buildings and ANSI/AISC 341-22, Seismic Provisions for Structural Steel Buildings. The AWS D1.1, Structural Welding Code — Steel, and AWS D1.8, Structural Welding Code — Seismic Supplement, are not referenced in the IBC. However, because AWS D1.1 is referenced in AISC 360 and AWS D1.8 is referenced in AISC 341, you are legally bound to follow AWS D1.1 and D1.8 when those AISC codes are referenced. When documents are listed by reference in a contract, all their requirements are legal requirements. The “why” is because they are a legal contract between you and your client.
AISC 360, Chapter N addresses the minimum requirements for quality control (QC), quality assurance, and nondestructive examination for structural steel systems and steel elements of composite members for buildings and other structures. AISC 341, Chapter J addresses QC and quality assurance for structures subject to seismic design. AISC 360, Chapter N and AISC 341, Chapter J specify quality for structural systems but not design of welded connections. In contrast, AWS D1.1 addresses design of welded connections, qualification of welding procedure specifications (WPSs) and personnel, fabrication, inspection, and welding of studs and tubular structures. Understanding and using the relevant requirements to develop quality standards and procedures for your organization will increase quality, reduce defects and repairs, and build a reputation for quality work.
Saving Time and Money
How can you save time and money and create a quality reputation? AISC 360, Chapter N has one primary section that can answer that question: Section N2. If you don’t own AISC 360, visit aisc.org/standards for a free download. Then go to Chapter N, Section N2, Fabricator and Erec-tor Quality Control Program. It states, “The fabricator and erector shall establish, maintain, and implement QC procedures to ensure that their work is performed in accordance with this Specification and the construction documents.”
At a minimum, the fabricator’s QC procedures shall address the following AISC 360 requirements:
a) Shop welding, high-strength bolting, and details in accordance with Section N5;
b) Shop cut and finished surfaces in accordance with Section M2;
c) Shop heating for straightening, cambering, and curving in accordance with Section M2.1; and
d) Tolerances for shop fabrication in accordance with Section 11.2 of ANSI/AISC 303-22, Code of Standard Practice for Steel Buildings and Bridges.
For the erector, AISC 360 requires the following:
a) Field welding, high-strength bolting, and details in accordance with Section N5;
b) Steel deck in accordance with ANSI/Steel Deck Institute (SDI) Standard for Quality Control and Quality Assurance for Installation of Steel Deck;
c) Headed steel stud anchor placement and attachment in accordance with Section N5.4;
d) Field cut surfaces in accordance with Section M2.2;
e) Field heating for straightening in accordance with Section M2.1; and
f) Tolerances for field erection in accordance with Section 11.3 of AISC 303.
Pay special attention to Section N2(a) for both the fabricator and erector:
a) Shop (and field) welding, high-strength bolting, and details in accordance with Section N5.
What is a procedure for welding, and how can its use save time and money? A procedure for welding may have elements that address WPSs, welder qualification/certification and continuity, filler metal storage, and inspection. Let’s break these down to determine their value to your organization.
WPSs. By following the WPS, the crew leader, foreman, and welder will understand the required pre-heat, filler metal, joint details, and more — all of which may have significant cost impacts if not followed. Lack of preheat (D1.1:2020, Clause 7.6) can lead to cracks; the wrong filler metal (D1.1:2020, Clause 5.6) can cause significant joint failure; and incorrect joint tolerances (D1.1:2020, Clause 5.4) lead to cutouts, cracking, and/or a lot of filler metal being used to fill a larger volume. For instance, a 1-in.-thick plate with a B-U4 joint and 1/4-in. root opening requires approximately 4.24 lb/in. of weld metal. A 1/16-in. increase in root opening to 5/16 in. requires approximately 4.46 lb/in. of weld metal, a 20% increase. Each of these examples adds considerable time and costs in rework. They can be avoided by developing and communicating WPSs to the staff.
Welder qualification/certification and continuity. Welders must be qualified (D1.1:2020, Clause 6.2.2) and have documented evidence of welding at least once every six months. A welder who is not qualified/certified might not understand the WPS and cause significant issues with lack of preheat, visually unacceptable welds, and more. Welds that are not performed following the WPS can lead to rework. Qualified welders will be able to follow the WPS and consistently de-liver proper welds.
Filler metal storage. If not stored properly, the coating on E7018 filler metal (D1.1:2020, Clause 7.3) is a sponge for hydrogen. Because the hydrogen atom is about four times smaller than an iron atom, it works its way out of the base metal after welding, sometimes immediately and other times not until hours later. It’s the several hours later that can cause latent cracking on joints that have diffusible hydrogen and applied mechanical or residual stress. These situations can manifest in the form of connection failure and/or costly reworks late in the project life cycle or beyond.
Inspection. QC is the responsibility of the entity, such as the fabricator or erector, doing the work. Because it is a mandatory requirement in AISC 360, Chapter N (Sections N4 and N5) as well as in D1.1:2020 (Clause 184.108.40.206), this activity is a legal requirement. This inspection procedure should address the level of qualification for the QC inspector (see AISC 360, Chapter N, Section 4.1, and AWS D1.1:2020, Clause 8.1.4), frequency of inspection, and documentation. A robust quality program that is independent of production, is strongly backed by executive lead-ership, works collaboratively, and is well documented can understand trends, foresee issues that could lead to rework, and help reduce overall costs by keeping rework to a minimum.
The information in this article supplies a snapshot of what is contained in ASIC 360 and AWS D1.1. The QC procedures discussed can be as expansive as your company requires and no less than those required by AISC 360, Chapter N, and AWS D1.1.
This article was written by Mike Gase (email@example.com) for the American Welding Society.