In This Issue

In the case of one 11-year-old Chicago office tower, "up" was the only way to go. Lohan Associates (now Goettsch Partners) designed the 33-story steel-framed Blue Cross-Blue Shield tower with vertical expansion in mind: columns had been stubbed through the roof, and a dramatic glass-enclosed atrium was designed to become high-rise elevator shafts. Now that Blue Cross has outgrown the tower, a 24-floor vertical expansion is underway.

 

Adding more floors to an existing structure is not without its challenges, especially when you're starting from 500 feet in the air. For example, a 17-ton derrick was hauled up through the building in sections on a 6,000-lb-capacity freight elevator. The 17-ton derrick was used to bring up the pieces for a 35-ton derrick, which was then used to dismantle the 17-ton derrick and assemble the first of two tower cranes. The location of the building, just a few blocks from the lake Michigan shoreline, made winds an issue. City of Chicago rules prohibit crane assembly when winds are more than 30 mph, delaying tower crane erection by 30 days.

 

Read more about this carefully-planned steel project here.

The structural steel industry has a long track record of success in sustainable development, consistently leading the way in implementing energy, carbon and resource utilization improvements for the past 25 years. Those improvements have been driven by the three hallmarks of sustainability — environmental, social and economic stewardship.

 

Today, however, the structural steel industry is faced with a significant challenge, one that originates not from a lack of accomplishment with respect to sustainability, but rather from being too successful in this area.

 

AISC has significant concerns with some provisions in the recently published second draft of the proposed ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.) Standard 189.1 Standard for the Design of High-Performance Green Buildings Except Low-Rise Residential Buildings. AISC's concerns with this proposed standard are that we believe it:

 

1. is outside the scope and expertise for which ASHRAE is ANSI-accredited.
2. will result in adverse environmental impacts.
3. includes provisions that are unfair to steel, and inappropriately preferential to the interests of the concrete industry.
4. adversely restricts the freedom of design professionals in their selection of structural framing materials.

 

The proposed ASHRAE standard, being developed jointly with the US Green Building Council and the Illuminating Engineering Society of North America, is intended to provide minimum requirements for high-performance green buildings. The apparent goal of ASHRAE is to include 189.1 in the International Building Code as an appendix available for local adoption.

 

While addressing HVAC and lighting issues, the standard also establishes prescriptive requirements for construction materials, an area that AISC believes to be outside the scope and expertise of ASHRAE, USGBC and IESNA. In addition, the committee responsible for the proposed 189.1 standard was not constituted in a balanced manner under appropriate ANSI consensus protocol. We also believe that the committee lacks expertise in the area of construction materials, particularly as they relate to structural framing systems.

 

This apparent lack of balance and expertise has resulted in provisions that AISC believes to be significantly slanted toward the interests of the cement and concrete industry under the guise of encouraging less sustainable industries to become more sustainable.

 

For example, today a typical structural steel frame provides an 11% credit towards the overall recycled content of a building. A concrete frame may provide one to two percent. At the same time, the reinforcing steel in the concrete structure will provide an additional 5% credit. The proposed standard will limit the contribution for any material at 5%. The result: structural steel gets capped at 5%, while concrete still gets its full credit AND the 5% credit for steel.

 

Similarly, the definition of recycled content is that portion of a material by mass that originates in either pre- or post-consumer waste streams. But the ASHRAE committee has decided to allow the calculation of the recycled content of concrete to violate that definition. Instead of reflecting the actual recycled content of the concrete, ASHRAE 189.1 allows the recycled content of the cementitious portion of the concrete to be used as the recycled content of the entire concrete mix.

 

For example, at present, substituting 25% fly ash for Portland cement in concrete with no other recycled content, results in an actual recycled content of 3%. Under ASHRAE 189.1 the cement and concrete industries are allowed to claim a 25% recycled content.

 

The committee’s justification is that they wish to encourage the use of fly ash in concrete. In reality, they are discouraging the use of recycled aggregates, removing over 50% of the mass of a concrete building from green considerations and providing the cement/concrete industry with an unfair advantage in the marketplace.

 

It is not the role of a standard to provide incentives and to favor particular products. The selection of structural framing materials should be based on the merits of the materials as judged against a consistent metric.

 

The inclusion of this standard in building codes is being encouraged by ASHRAE as an appendix at the national level available for local adoption. Including these provisions in a local building code in order to provide incentives to certain materials will significantly limit the opportunity of design professionals to select construction materials for high performance green buildings that properly balance economic, environmental and design issues.

 

The structural steel industry believes strongly in the need for high-performance green buildings. We also believe that standards for the selection and optimization of structural framing materials for those buildings should be developed in a balanced, consensus-based ANSI process that engages design professionals, industry associations and interested parties with the required level of expertise to develop a fair and environmentally sound standard. We would welcome the participation of the concrete, cement, masonry, wood, pre-cast, light gauge steel, per-engineered building and any other affected industries in that process.

 

AISC’s objection to 189.1 is not a rejection of sustainable construction practices or the need for green buildings. Much to the contrary, our commitment is to continue to be the leader in cradle-to-cradle sustainable construction materials and to actively pursue additional sustainable practices within our industry.

 

When the domestic structural steel industry experienced a rebirth 25 years ago, purposeful decisions were made to create a sustainable domestic structural steel industry. Central to that decision was the transition from Basic Oxygen Furnaces using iron ore and coke to Electric Arc Furnaces using scrap iron and steel as the primary raw material and electricity and natural gas as energy sources.

 

Resulting from this transition have been numerous gains positively impacting sustainable construction:

 

• Wide flange structural steel products average in excess of a 90% recycled content.
• A 96% recycling/reuse rate for structural steel members removed from existing structures.
• An increase in mill productivity by a factor of 20 moving from 10 to 12 man-hours per ton to 0.6 man-hours per ton.
• A reduction in energy consumption per ton of product by 30%.
• A reduction in carbon emissions by 47% since 1990 — by comparison the Kyoto protocol would have mandated a 5.2% reduction by 2012.
• A recycling rate for automobiles now exceeding 100% emptying out salvage yards.
• The elimination of all production water discharges and the minimization of water utilization.
• An increase in the strength of structural steel by 38% over the past 10 years reducing the quantity of structural steel required in a typical building.

Supplement No. 1 to the 2005 AISC Standard Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications (ANSI/AISC 358-05) is now available for public review. This supplement includes limited revisions to existing provisions for End-Plate and Reduced Beam Section (RBS) Connections, and provides design provisions for additional moment connection technologies, including the Bolted Flange Plate (BFP) Moment Connection, the Welded Unreinforced Flange – Welded Web (WUF-W) Moment Connection, and the Kaiser Bolted Bracket (KBB) Proprietary Cast Moment Connection. The Supplement also includes a draft appendix for cast steel material and quality.

 

The draft supplement is available for your review by downloading the document at the links provided below. Please vote and submit comments on the Supplement using the attached ballot form. A hard copy of the supplement can also be requested for a fee of $15 by calling 312-670-5411 or by e-mail to cummins@aisc.org.

Please submit your comments electronically to hewitt@aisc.org using the comment form available at the links below, or mail to:

 

Christopher Hewitt, S.E.
American Institute of Steel Construction
Suite 700
One East Wacker Drive
Chicago, IL 60601

 

All comments are due by May 12, 2008.

 

To download the public review document, visit www.aisc.org/358s1.

 

To download the comment form, visit www.aisc.org/358s1PRcomments.

 

To download the existing 2005 ANSI/AISC 358 Standard, visit www.aisc.org/AISC358.

The winner of the Best EJ Paper of 2007 competition is James O. Malley for his paper "The 2005 AISC Seismic Provisions for Structural Steel Buildings," which was published in the first quarter 2007 issue of AISC’s Engineering Journal.

 

The winning author was offered complimentary registration to the 2008 NASCC, held in Nashville last month, as well as travel expense reimbursement; the award was presented during the conference.

 

Be sure to participate in selecting the Best EJ Paper of 2008. Voters are eligible for a drawing to receive complimentary registration to NASCC, including travel reimbursement. Manuel Perez, employed by the City of Los Angeles, was the winner of this year’s drawing.

OSHA has launched a National Emphasis Program (NEP) targeting health hazards associated with occupational exposure to crystalline silica. The new program directs OSHA regional offices to inspect workplaces with elevated exposure levels and to provide "compliance assistance" to employers. Crystalline silica is a carcinogen and can lead to silicosis, a disabling and irreversible lung disease.

 

The directive lists streel fabrication as one of the industries at risk for exposure. The exposure potential comes from sand blasting steel with silica sand. While not prevalent in the fabrication industry, sand may still be used in some situations. Companies using sand for blast media are encouraged to use the NEP to establish and enforce rigorous procedures to prevent exposure to blast personnel and bystanders. The NEP includes inspection procedure information and an inspector checklist. You can view the diretive at www.osha.gov/OshDoc/Directive_pdf/CPL_03
-00-007.pdf.

What's being answered right now:

Q.

I am trying to determine the load-bearing capacity of a roof on a building that is about 100 years old. The steel has been identified as S9x19.75 (purlins) and S15x33 (girders). Is there any way, for purposes of calculations, to determine the yield strength of the members? I'm guessing it's unlikely that the members are ASTM A36 steel. What was standard for the time?

A.

If the building is about 100 years old, it is definitely not ASTM A36 steel. The ASTM A36 Standard was not issued until 1962.

 

The year 1900 represented the issuance of the first ASTM Standard for Structural Steel which was intended to bring uniformity to the various steel materials being produced at the time. It is only a guess as to what the actual characteristics of a specific material may represent for that time period; that is, if it was produced to an ASTM Standard. The 1900 ASTM A9 Standard for Buildings listed Tensile Strength of 60,000 to 70,000 psi with a minimum yield point of 35,000 psi. The 1909 ASTM A9 Standard listed slightly lower Tensile Strength (T.S.) at 55,000 to 65,000 psi and Minimum Yield Point at ½ of the T.S. AISC Design Guide 15 titled AISC Rehabilitation and Retrofit Guide is a reference for historic shapes and specifications. Therein you will find a historical summary of ASTM Specifications for structural steel.

 

Unless there is good documentation as to what was specifically specified for the project, it would be prudent to undertake a testing program to determine reasonable material parameters for the structure. For further guidance refer to Appendix 5 of the 2005 AISC Specification for Structural Steel Buildings (a free download at www.aisc.org/2005spec), which covers evaluation of existing structures. Section 5.2 of this Appendix covers material properties.

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