Six new steel standards

March 2011 » Features » STEEL
Updates to typical building design and construction using structural steel
Charles J. Carter, Ph.D., S.E., P.E.

The year 2010 saw the completion of six new standards that relate to typical building design and construction using structural steel. Three are from American Institute of Steel Construction (AISC), one is from the Research Council on Structural Connections (RCSC), and two are from the American Welding Society (AWS).

The highlights of improvements and changes in each are discussed below, and all are incorporated by reference in the 2012 International Building Code. These documents will be the basis of the 14th Edition AISC Steel Construction Manual, which will be published later this year.

ANSI/AISC 360-10
The 2010 AISC Specification for Structural Steel Buildings, which is available as a free download at www.aisc.org/freepubs, includes the following noteworthy improvements and changes:

  • The scope statement in Chapter A has been revised to reflect seismic design requirements and when the provisions in ANSI/AISC 341 are applicable.
  • Structural integrity requirements have been added in Chapter B.
  • The stability analysis and design procedures introduced in the 2005 version have been simplified and better organized (Chapter C and Appendices 7 and 8).
  • Expanded and new provisions are included for composite member design (Chapter I).
  • The available shear strength values for bolts have been increased (Chapter J).
  • Slip-critical design provisions have been simplified (Chapter J).
  • Hollow structural steel (HSS) connection design equations have been reorganized in a tabular format for ease of use (Chapter K).
  • A new chapter has been added on quality control and quality assurance (Chapter N).
  • Inelastic Analysis and Design provisions have been expanded and improved (Appendix 1).

ANSI/AISC 341-10
The 2010 AISC Seismic Provisions for Structural Steel Buildings, which is available as a free download at www.aisc.org/freepubs, includes the following noteworthy improvements and changes:

  • The format of the document has been revised to better align with the format of the ANSI/AISC 360.
  • The intended combination of these ANSI/AISC 341 provisions and ACI 318 provisions for composite construction systems has been clarified.
  • A new chapter on analysis requirements has been added.
  • The capabilities for ductile response of various members in the seismic force resisting system (SFRS) have been made more explicit.
  • Requirements for the design of members and connections that are not part of the SFRS for deformation compatibility have been clarified.
  • A discussion of the “basis of design” has been added to explain the intended seismic response characteristics of each structural system.
  • The consistency and completeness of how each structural system treats the seismic design and detailing have been improved.
  • Two cantilevered column systems have been added to be consistent with other systems in these provisions and the seismic design parameters ASCE/SEI 7-10.
  • Analysis requirements have been added to address the inelastic response of special concentrically braced frames (SCBF).
  • Connection requirements have been added for braced frame systems to ensure that the expected deformation demands can be accommodated.
  • Requirements have been added for the use of box-shaped link beams in eccentrically braced frames (EBF).
  • The use of perforated plates in special plate shear walls (SPSW) is now addressed.
  • Design requirements and details for composite systems have been clarified and improved.
  • AWS D1.8/D1.8M has been incorporated by reference for welding-related issues.

AISC 303-10
The 2010 AISC Code of Standard Practice for Steel Buildings and Bridges, which is available as a free download at www.aisc.org/freepubs, includes the following noteworthy improvements and changes:

  • The scope in Section 1.1 has been revised to cover buildings and other structures in a manner that is consistent with how they are treated in ANSI/AISC 360.
  • Section 1.9 has been added to emphasize that not all tolerances are explicitly covered in the code, and that tolerances not covered are not to be assumed as zero.
  • Clarification has been added in Section 2 that base plates and bearing plates are considered structural steel if they are attached to the structural frame, but not if they are loose items that do not attach to the structural steel frame.
  • Editorial improvements have been made in the commentary to Section 3.1 to improve upon the list of items that should be provided in the contract documents, as well as to link column differential shortening and anticipated deflections to information that has been added in the commentary to Section 7.13.
  • Explicit requirements have been added in Section 3.1.2 as “option 3” for when connection design work is delegated by the structural engineer of record (SER) to be performed by another engineer. Provisions covering connection design by the SER (option 1) and selection or completion of basic tabular connections by a steel detailer (option 2) also have been revised for consistency with and distinction from option 3. Additionally, the defined term substantiating connection information has been added to the glossary, and revisions have been made in Section 4 to correspond with the addition of option 3 in Section 3.1.2.
  • Information has been added to the commentary in Section 4.1 to summarize the importance and benefits of holding a pre-detailing conference to open lines of communication and develop a common understanding about the project.
  • Section 4.7 has been added to address requirements for erection drawings.
  • Section 6.4.3 has been modified to better address incidental camber in trusses.
  • Information has been added in the commentary to Section 7.10.1 to better describe the provisions that relate to special erection conditions or other considerations that are required by the design concept, as well as to highlight special considerations in the erection of cantilevered members.
  • The intent in Section 7.13.1.2(d) has been clarified in the text as well as with the relocation of supporting commentary.
  • The intent in Section 10.2.5 has been editorially clarified for groove welds in butt joints and outside corner joints.
  • The document has been editorially revised for consistency with current terms and other related documents.

RCSC
The 2009 RCSC Specification for Structural Joints Using High-Strength Bolts, which is available as a free download at www.boltcouncil.org, includes the following noteworthy improvements and changes:

  • The title has changed (from Specification for Structural Joints Using ASTM A325 or A490 Bolts) to recognize that many grades of high-strength bolts now are used and the RCSC specification covers more than just the conventional ASTM A325 and A490 grades.
  • ASTM F2280 bolt assemblies were added to the specification. These are twist-off-type tension-control bolts with a strength equivalent to that in ASTM A490.
  • ASTM F1136 coating usage was added to the specification. This type of protection can be used on both ASTM A325 bolts (which can be galvanized) and ASTM A490 bolts (which can’t be galvanized).
  • References to ASTM A153 have been replaced with an updated reference to ASTM F2329. This is just a new ASTM standard that better addresses hot-dip galvanizing of fastener products.
  • Section 3.3 was modified to provide a clarification on thermally-cut holes. In short, thermal-cutting methods are permitted if they result in an acceptable surface condition.
  • Section 3.4 was modified in regard to burrs greater than z-inches high to make the provisions easier to apply.
  • Table 5.1 was modified to show new shear design values for joints based on overall joint length. Like the new values in the AISC Specification, bolt shear strength is now higher in the RCSC Specification as well.
  • Sections 7 and 8 had a number of clarifications added in relation to pre-installation verification and installation practices. Among them, Table 7.1 was added to clarify the minimum bolt pretension for pre-installation verification.
  • The “snug-tight” definition and references have been modified to make this terminology less subjective in its application. Now you can think of snug-tight as the condition in which the nut cannot be removed by hand.
  • Appendix B (ASD) tables were brought into consistency with equivalent provisions in Section 5 (LRFD).

AWS D1.1-10
The Structural Welding Code – Steel, which is available at www.aws.org, also contains some noteworthy revisions. An excellent summary of changes to AWS D1.1-10 has been published by John Gayler, AWS Director of National Standards Activities in the AWS Welding Journal. Following are a few excerpts from that article:

  • The update cycle for AWS D1.1 has been changed to a five-year rather than the previous two-year cycle.
  • A new table in the prequalification section (Table 3.8) lists which variables must be included on a prequalified WPS, and how changes beyond certain parameters would require a new or revised WPS to be written.
  • Weld profile figures (Figure 5.4) have more illustrations to better clarify what weld profiles are required in different types of weld joints. Many clarifications and improvements have been made in the information surrounding these new figures as well.
  • New thermal cut roughness values are tied solely to the comparison samples found in AWS C4.1, Oxygen Cutting Surface Roughness Gauge.
  • Weld access hole dimensions have been modified and mandatory minimum, and recommended maximum depth dimensions of access holes have been set to prevent unnecessarily deep or shallow access holes.
  • A smaller radius on re-entrant corners in connection material and beam copes is permitted.
  • Beam copes in galvanized sections must now be ground to bright metal to reduce the possibility of cracking.
  • Preheating before thermal cutting of beam copes and weld access holes in heavy shapes is now mandatory to reduce the formation of a hard surface layer and the tendency to initiate cracks.
  • Backing requirements in Subclause 5.10 now allow for discontinuous backing in some limited statically loaded HSS applications.
  • Under Subclause 3.3, the matching and undermatching table has been revised and clarified.
  • New commentary on electroslag and electrogas welding (ESW and EGW) has been added as assistance to users in implementing these welding processes. Also, commentary to alert users when applying ESW and EGW on quench and tempered steels, thermomechanical control processed steel, and precipitation hardened steels subjected to cyclic loading applications has been added.
  • Additional commentary has been added to emphasize that the UT acceptance criteria shown in Tables 6.2 and 6.3 have been established within specific testing parameters, and that using testing equipment or procedures, such as transducers of a different size or angle shown in these tables, may invalidate the results.

AWS D1.8-09
The Structural Welding Code – Seismic Supplement, which is available at www.aws.org, is a new supplement to AWS D1.1 to address welding requirements in high-seismic applications (when the provisions of ANSI/AISC 341 apply). Its provisions parallel and develop those previously included explicitly in ANSI/AISC 341-05. It is now incorporated in ANSI/AISC 341-10 by reference.

Charles J. Carter, Ph.D., S.E., P.E., is vice president and chief structural engineer at the American Institute of Steel Construction in Chicago. He can be reached at carter@aisc.org.

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