GLFEA

Revised AISC Steel Construction Code
Topic of GLFEA Breakfast Seminar

Jan. 27, 2003 - Clearer language, easy-to-find explanatory commentary, and practical information on buying and selling structural steel materials were among the goals of the American Institute of Steel Construction when it set out a few years ago to revise its industry standard, the Code of Standard Practice for Steel Buildings and Bridges. The result, the March 7, 2000, edition of the Code is a well organized, succinctly phrased, 80-page handbook for structural engineers and designers, as well as steel fabricators, erectors, detailers, general contractors, and other construction professionals involved in structural steel used in building bridges and buildings.

Steven M. Ashton, P.E., AISC senior engineer for continuing education, outlined changes in the revised Code at a Great Lakes Fabricators & Erectors Association breakfast meeting Jan. 24. Held at the Westin Hotel in

Steve Ashton, P.E., AISC senior engineer, discusses the fine points of the March 7, 2000, edition of the AISC Code of Standard Practice.

Southfield, the meeting drew an audience of about 70 persons, many of whom were structural engineers. GLFEA sponsors the breakfast meetings free-of-charge on topics usually geared toward the engineering/design sector of the structural steel construction industry.

"The new Code should be used more or less as a reference document," Ashton said. Its language is more straightforward than past editions, and its intention is to minimize misunderstandings on project sites, he added. AISC describes the Code as having "…been prepared in accordance with recognized engineering principles and is for general information only. While it is believed to be accurate, this information should not be used or relied upon for any specific application without competent professional examination and verification of its accuracy, suitability and applicability by a licensed engineer, architect or other professional. …The Code provides a useful framework for a common understanding of the acceptable standards when contracting for structural steel."

Ashton cautioned attendees to ensure they're working from the revised March 2000 Code, which supersedes the 1992 edition. The AISC Code was first published in 1924, and has been revised only five times since. The AISC is interested in revising it more frequently, Ashton said, perhaps every five years or six years. The 2000 edition represents the first time non-fabricators were on the AISC committee charged with the revision, in an effort, Ashton explained, to bring more "balance" to the document. The committee included six structural

GLFEA Executive Director Jim Walker welcomes guests to the Jan. 24th seminar.

engineers, two architects, one general contractor, seven fabricators, one steel detailer, three erectors and one attorney, in addition to one staff member each from AISC and the National Steel Bridge Alliance. Copies of the Code are available for $20 (members) and $30 (non-members) from AISC, or for free download at the association's Web site, www.aisc.org.

"In general, what we've tried to do with the 2000 edition is to provide clear-cut language so there's no room or little room for interpretation," Ashton said. "The Code of Standard Practice is a practical, useful basis for buying and selling structural steel. It serves as a standard contract for buying and selling structural steel, so that you don't have to re-invent the wheel every time you write a contract."

Among differences in the 2000 Code, Ashton said, is a change in format to make the explanatory commentary easier to find. It's been "intermingled" with the text, immediately following the corresponding code provision, rather than being placed at the back of the book as in past editions. Also, the use of the word "Owner" has been, in general, eliminated in favor of "Owner's Designated Representative for Design" and "Owner's Designated Representative for Construction." And the new Code includes both U.S. customary units and metric units of measure, with the caution that the engineer or detailer "isn't allowed to mix and match," Ashton said. Choose one unit of measure and stick with it throughout the project's documentation.

The AISC engineer then described in detail two particular sections of the revised Code: the Approvals Process for changes to connections details and the temporary support of structural steel frames during erection.

Language in the new Code on the approval process for shop and erection drawings has been "softened" somewhat, Ashton said, to be more in line with older versions of the Code to avoid some of the "face slapping" tone used in more recent editions. The intent of the section on the approval process was shared by all members of the Code committee, he said, explaining that the fabricator retains the responsibility for dimensional accuracy and fit-up. According the Code, the fabricator is responsible for "…transferring the information from the Contract Documents into accurate and complete shop and erection drawings," and for developing "…accurate, detailed dimensional information to provide for the fit-up of parts in the field." The fabricator cannot just make changes at will to the Contract Documents, Ashton said, and is required instead to notify the design engineer "ahead of time" of a need to change a connection detail.

Ashton discussed the two general "extremes" in methods of handling Connection Design Responsibility, with the one extreme being that the structural engineer assumes all responsibility for designing and drawing all connection details, and the other extreme being that the design engineer delegates all connection details to the fabricator. There are many variations in between those two extremes, Ashton noted. He said the new Code clearly states in the first section "The structural Engineer of Record shall be responsible for the structural adequacy of the structure in the completed project." In later sections the Code "provides guidance in the Commentary on what is acceptable practice for delegating connection detailing to the fabricator." The structural engineer must allow the fabricator the selection of basic connections but the connections must be easily picked out of the AISC Manual of Steel Construction or the Contract Documents, Ashton said in paraphrasing the Code.

In language paralleling that in the American Council of Structural Engineers' Document No. 962, the revised AISC Code says the structural Engineer of Record "retains responsibility for the adequacy and safety of the entire structure." Ashton explained that the Code requires that the structural engineer must state in the design drawings and specifications any limitations to the selection of simple connections.

"The intent is that fabricators and detailers are not making design decisions," Ashton said.

A third option for connection design responsibility involves the special case of Design/Build. Even with this method, the structural engineer still retains responsibility for connection design, Ashton said.

Regarding the temporary support of structural steel frames during erection, "the new code could not be more clear in its intent," Ashton said, referring to the code's §1.8.1, which states: "The Erector shall be responsible for the means, methods, and safety of erection of the Structural Steel frame." and "The Structural Engineer of Record shall be responsible for the structural adequacy of the structure in the completed project. The Structural Engineer of Record shall not be responsible for the means, methods and safety of erection of the Structural Steel frame."

The terms "supporting" and "self-supporting" were removed from the new edition of the Code. "Those were lightening rods," Ashton explained. He said they were replaced with information the erector needs from the designer and constructor.

The new Code identifies the structural engineer as being responsible for identifying in the Contract Documents the lateral-load-resisting system and pertinent connecting diaphragm elements. "The reason for that is to that the erector knows when the temporary bracing or the guys, cables, and such can be removed once everything is in place," Ashton explained.

Information the erector needs from the constructor includes when the non-steel elements identified by the designer as the lateral-load-resisting system will be in place. "Armed with this information…," Ashton said, then quoted from the Code: "The Erector shall determine, furnish, install all temporary supports … or other elements required for the erection operation." Ashton pointed out that the Code finds the erector is responsible for providing temporary supports capable of handling such common loads during erection as those created by wind and erection operations. The erector is not responsible, however, for such unpredictable elements as hurricanes, tornadoes, earthquakes, explosions, or collisions, or for loads created by the actions of others or by the installation of non-structural steel materials such as cladding, interior partitions, and etc.

Other major changes in the Code, which are briefly described in the manual's Preface and which Ashton mentioned in the seminar, include:

Requirements for existing structures have been added to in order to include four scenarios: demolition and shoring, protection against damage, surveying or field dimensioning, and hazardous materials. The standard is clear, Ashton said, that the fabricator is not responsible for these requirements.

Materials classification has been expanded and distinguishes between structural steel materials and non-structural steel materials.

The resolution of discrepancies in the contract documents has been expanded and clarified and states it's not the responsibility of the fabricator or erector to find discrepancies, but it is their responsibility to report them in a timely manner. The "order of precedence" has been changed, Ashton said, noting that the design drawings take precedence over specifications.

Regarding revisions to the design drawings, Ashton quoted from the new Code: "…all revisions, including revisions that are communicated through the annotation of shop and/or erection drawings shall be clearly and individually indicated in the Contract Documents." The Code also calls for design drawings to be dated and identified by the same drawing number throughout he project. Ashton said it's surprising how many times that doesn't happen.

Fast Track Project Delivery is addressed in the revised Code, and Ashton noted that it provides a "great opportunity" for structural steel, making structural steel the "best and sometimes the only option" for the project. He emphasized the risk the project Owner assumes with Fast Track project delivery for additional design and construction costs.

The use of design drawings by fabricators and erectors is now covered in the Code, Ashton said. Permission for such use has to be sought, he advised, since the design drawings are the "intellectual property" of the designer. The steel fabricator still is responsible for ensuring that the shop drawings match the design drawings, he cautioned.

Straightness tolerances for curved members are discussed in the new Code. They were not covered in prior editions. The revised Code uses the tolerances described in ASTM A6/A6m for wide flange shapes, except in those cases where the Contract Documents call for less variation in straightness.

Permissible variations in truss camber tolerances require that the "variation in camber at each specified camber point shall be equal to or less than plus or minus 1/800 of the distance to that point from the nearest point of support."

The new Code finds that most structural steel doesn't need to be primed or painted. Ashton referred the audience to an article in the December 1993 issue of Modern Steel Construction (available on the AISC Web site) for more information.

The installation of bearing devices and their grouting is covered in the revised Code, which emphasizes the timing of grouting. Ashton cautioned attendees to be aware of the safety issues involved with the use of shims, quoting from section 7.7 of the Code: "Standard practice provides that loose base plates and leveling plates are to be grouted as they are set. Bearing devices that are set on shims or leveling nuts are grouted after plumbing, which means that the weight of the erected structural steel frame is supported on the shims or washers, nuts and anchor rods. The erector must take care to ensure that the load that is transmitted in this temporary condition does not exceed the strength of the shims or washers, nuts and anchor rods."

Accumulation of mill and fabrication tolerances is allowed, Ashton explained, but they are not to exceed the erection tolerance.

Anchor rods are discussed in the new Code, including allowable tolerances. "So much money is spent because these (anchor rod) tolerances are not met," Ashton said.

Quality Assurance gets a fair amount of attention in the Code, and Ashton described the AISC's Quality Certification for Steel Erectors and Quality Certification for Steel Fabricators programs that he said attempt to quantify that a fabricator or erector has the necessary personnel, equipment, and quality control processes in place to meet quality assurance standards.

Architecturally exposed structural steel (AESS) is discussed in the new Code, with attention given to welds (they must conform to American Welding Society, AWS D1.1 requirements), and hollow structural steel (HSS) members, on which the welds must be oriented away from view.

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