AISC 360 STEEL SPECIFICATIONS - “OBSERVE” AND “PERFORM” DEFINED

Understanding the meaning of those nebulous steel code words “observe” and “perform”

When the 2012 edition of the International Building Code (IBC) replaced the IBC 2009 code cycle, one of the significant changes was the deletion of Table 1704.3, “Required Verification and Inspection of Steel Construction.” Table 1704.3 was marvelous and listed the special inspections required in the fabrication shop and the field during construction. The table also advised special inspectors, engineers, architects, and contractors which inspections were periodic (random) and which were continuous. The updated IBC code also dropped the terms periodic inspection and continuous inspection where structural steel inspection was concerned. The new code language stipulated that all special inspections for structural steel be in accordance with the quality assurance inspection requirements of American Institute of Steel Construction 360 (AISC 360).

AISC 360 introduced us to the words observe and perform, which replaced the old code words periodic and continuous, respectively. Observe and perform indicate the frequency of special inspections and tests just as periodic and continuous previously had done in Table 1704.3. Even though observe and perform replaced the words periodic and continuous more than a decade ago, there remains anxiety and confusion about implementing them into structural steel quality assurance programs in the field.

AISC 360, Chapter N, defines these terms:

Observe (O): The inspector shall observe these items on a random basis. Operations need not be delayed pending these inspections.

Perform (P): These tasks shall be performed for each welded joint or member.

AISC 360 uses these terms to address the frequency of special inspections and tests related to structural steel inspections, including welding and bolted connections. Numerous other steel codes and standards use these words to indicate the frequency of inspections, just as the words periodic and continuous did for steel inspections in the previous decade. Architects, engineers, specification writers, steel fabricators, and contractors still need help getting a handle on observe and perform as the terms apply to the frequency of steel inspections.

Let’s get started on this trip through parts of AISC 360, Chapter N, to explain. Observe, denoted by the letter (O) in the Chapter N tables, means that the special inspector will observe these items randomly during steel construction phases. Perform, denoted by the letter (P) in the Chapter N tables, means that the special inspector will check and/or test every welded or bolted connection. It is essential to understand that the special inspector will provide these random inspection tasks and/or tests on many items during construction phases, as required by the Chapter N tables listed below.

Random inspection tasks include observing settings on the welding equipment, welding materials, preheats and interpass temperatures, welding position, and other functions regarding welds and bolted connections as stipulated in specific Chapter N Tables N5.4-1, N5.4-2, N5.6-1, and N5.6-2. The special inspector will provide these random services more than once or twice during construction.

How many times will the inspector visit the project site to perform perform-required tasks? Who knows? Every project is unique, and steel elements and connections are different regardless of whether they are welded or bolted connections. Some steel connections are simple, and others are very complicated and require more inspection time. The number of welders and other steel erection personnel also impacts the special inspector’s schedule and time. Other contributing factors are the project size and experience of the erection team.

If the inspector encounters few or no discrepancies during inspection tours, then the required time on the project is moderate; however, if the inspector encounters numerous discrepancies, the number of reinspections increases and the amount of inspection time on the project grows. The inspector must also determine if (a) the project welders are adequately certified per American Welding Society (AWS) requirements and (b) that welders follow Weld Procedure Specifications (WPS) before and during construction phases.

Calculating the time required to provide special inspections on the steel elements of a project is complex. The many random inspections required under the term observe is unique in that the special inspector never knows how many inspection site visits will be required, nor do they know the duration of those visits. The magnitude of these random inspections is highly variable from project to project. Experience typically drives how anticipated code-required random inspections are calculated. However, even firms that provide structural steel special inspections have difficulty preparing project cost proposals for code-required testing and inspections.

Random inspections enable the special inspector to ultimately judge whether the work complies with the code and the construction documents. AISC 360 stipulates that “the inspector shall, at suitable intervals, observe joint preparation, assembly practice, welding techniques and performance of each welder, welding operator, and tack welder to ensure that the applicable requirements of the Code (AISC 360) is met.” Therefore, the special inspector must decide how many random inspections to complete in tandem with the required perform-tasked inspections. This combination will help the inspector verify that the steel elements comply with all applicable requirements.

AISC 360, Chapter N, Table N5.4-3, above, lists required inspection tasks after welding. The time (and ultimate cost) of the inspections required under perform verbiage is a little easier to understand than the various inspection tasks provided under the term observe. This is because most inspections provided under the perform term are done after the welds are completed. The perform class of inspections is mostly about visually inspecting the welds for length and measuring the size and contour of the welds while applying the visual acceptance criteria of AWS D1.1, Table 6.1.

The AISC 360 Chapter N tables for bolted connections work the same way as the Chapter N welding tables. These bolted connection tables are Table N5.6-1, Table N5.6-2, and Table N5.6-3, and about 10% of the inspection tasks are perform and 90% are observe. This means that 90% of the special inspector’s tasks will be of the random variety, and about 10% of the tasks will be inspection of every bolted connection. Table N5.6-3 of Chapter N requires that the special inspector visually inspect every bolted connection and document the acceptance or rejection of the connections. In addition to this Chapter N requirement, the Research Council on Structural Connections (RCSC) requires that two bolts or 10% of the bolts in the connection (whichever is greater) be inspected.

But Wait — We Have a Lot More to Say! For a complete picture of the Code and how it relates to Special Inspections, F&R would love to provide a virtual (for the time being) AIA-accredited Lunch & Learn presentation to the professionals at your firm.

Trouble Deciphering the Code? Call the Experts at F&R!

Alan S. Tuck, Director of Code Compliance & Training: T 540.344.7939 | M 540.798.4440 | [email protected]