Modern Steel Construction July 2010

July 2010

Expanding in the MiddleHow a big addition got built on a very tight site.

MSCMODERN STEEL CONSTRUCTION

IN THIS ISSUE

Fabrication and Sustainability

National Student Steel Bridge Contest

Steel-ebration Part 1

Model image courtesy of USC School of Cinema and Gregory P Luth & Associates

Tekla Structures BIM (Building Information Modeling) software provides a data-rich 3D environment that can be shared by contractors, structural engineers, steel detailers and fabricators, and concrete detailers and manufacturers. Choose Tekla for the highest level of constructability and integration in project management and delivery.

Greg, Kristen, and John of Gregory P. Luth & Associates (GPLA) know how to ensure the best end result to their projects. With Tekla, GPLA has moved from design to construction-driven engineering, adding value to clients by delivering models that are used downstream. Sharing the Tekla model allows all of the project team members to stay in the building information loop in real-time.

FROM DESIGN TOCONSTRUCTION

4 MODERN STEEL CONSTRUCTION JULY 2010

MODERN STEEL CONSTRUCTION (Volume 50, Number 7. ISSN (print) 0026-8445: ISSN (online) 1945-0737. Published monthly by the American Institute of Steel Construction (AISC), One E. Wacker Dr., Suite 700, Chicago, IL 60601. Subscriptions: Within the U.S.single issues $6.00; 1 year, $44; 3 years $120. Outside the U.S.single issues $9.00; 1 year $88; 3 years $216. Periodicals postage paid at Chicago, IL and at additional mailing offices. Postmaster: Please send address changes to MODERN STEEL CONSTRUCTION, One East Wacker Dr., Suite 700, Chicago, IL 60601.

AISC does not approve, disapprove, or guarantee the validity or accuracy of any data, claim, or opinion appearing under a byline or obtained or quoted from an acknowledged source. Opinions are those of the writers and AISC is not responsible for any statement made or opinions expressed in MODERN STEEL CONSTRUCTION. All rights reserved. Materials may not be reproduced without written permission, except for noncommercial educational purposes where fewer than 25 photocopies are being reproduced. The AISC and MSC logos are registered trademarks of AISC.

22 The Journal Goes E BY KEITH GRUBB, P.E., S.E.A few words about AISCs Engineering Journal and the debut of its online edition.

24 Expansion is Cut to Fit BY MATTHEW GOMEZ, P.E., S.E.Getting a head start on the cooperative effort pays off for the Seton Womens Center.

30 Growing an Office on the PlainsBY MICHAEL HEMSTAD, P.E., S.E.An urgent need for larger facilities was quickly met, thanks to flexibility, cooperation, and the selection of steel framing.

36 On a Beautiful TiltBY ROBERT B. ANDERSON, P.E., MIKE GUTER,

P.E., AND VICTOR JUDNIC, P.E.Featuring asymmetry in two major planes, Michigans first cable-stayed bridge was a challenge in both design and construction.

42 Learning the Art & Science of Steel DetailingBY RON CUTHBERTThe next best thing to years of experience is a solid course that covers the fundamentals.

46 Real-Life LessonsBY THOMAS L. KLEMENS, P.E.Students who participate in the student steel bridge competition learn far more than structural analysis and design.

July 2010

ON THE COVER: Seton Womens Center in Austin, Texas. (Photo: Rogers-OBrien Construction)

departments

6 EDITORS NOTE

9 STEEL INTERCHANGE

12 STEEL QUIZ

18 NEWS & EVENTS

resources

63 NEW PRODUCTS

64 MARKETPLACE

65 EMPLOYMENT

steelwise

50 Horizontal BracingBY BO DOWSWELL, P.E., ALLEN BRICE AND

BRIAN BLAINAn overview of lateral load resisting systems and how to implement them.

quality corner

54 Streamlining the Certification ProcessBY TODD ALWOOD, LEED APNew requirements will simplify the overall process for AISC Certification.

sustainability

56 The Fabrication FactorBY GEOFF WEISENBERGERThe fabrication shop is important in determining not only the cost of a structural steel package, but its environmental impact as well.

business

58 Construction Contracts for SubcontractorsAre You Covered?BY RON THOMPSONWhen you clearly understand what youre being asked to sign, you may want to go for better terms.

event

60 Its a Steel-ebration, Part 1BY ROSS ALLBRITTON AND WALT PRIMERHow to get the most out of hosting a SteelDay event in 2010.

columnsfeatures

24 3630

topping out

66 A Better Way BY DAVID CROWPerhaps gearing up with new tools can enhance your steel detailing productivity.


Editorial Offices1 E. Wacker Dr., Suite 700Chicago, IL 60601312.670.2400 tel312.896.9022 fax

Editorial ContactsEDITOR & PUBLISHERScott L. [email protected]

SENIOR EDITORThomas L. Klemens, [email protected]

EDITORIAL ASSISTANTAlison [email protected]

DIRECTOR OF PUBLICATIONSAreti [email protected]

GRAPHIC DESIGNERKristin [email protected]

AISC OfficersCHAIRMANDavid Harwell

VICE CHAIRMANWilliam B. Bourne, III

TREASURERStephen E. Porter

SECRETARY & GENERAL COUNSELDavid B. Ratterman

PRESIDENTRoger E. Ferch, P.E.

VICE PRESIDENT AND CHIEF STRUCTURAL ENGINEERCharles J. Carter, S.E., P.E., Ph.D.

VICE PRESIDENTJohn P. Cross, P.E.

VICE PRESIDENT SPECIAL PROJECTSLouis F. Geschwindner, P.E., Ph.D.

VICE PRESIDENTScott L. Melnick

Advertising ContactAccount ManagerLouis Gurthet231.228.2274 tel231.228.7759 [email protected]

For advertising information, con-tact Louis Gurthet or visit www.modernsteel.com

Address Changes and Subscription Concerns312.670.5444 tel312.893.2253 [email protected]

ReprintsBetsy WhiteThe Reprint Outsource, [email protected]

editors note

IN A RECENT BLOG, ADRIAN SEGAR WROTE ABOUT ENJOYING MEETING PEOPLE WHEN HE TRAVELSyes, hes the proverbial stranger in the seat next to you on a plane who strikes up a conversation.

I tend to fall into that same category, only for me its not just on airplanes. I might be in line at the grocery store and waiting to pick my daughter up from one of her many extracur-ricular activities. Recently I struck up a brief conversation with a gentleman who turned out to be the parent of one of my daughters close friends. In recounting the conversation to my wife, I reported on what he did for a living, how he had spent five years in Toronto (her home town), how many kids he had and how they got along, and how we both mildly complained about essentially being chauffeurs for our kids and that we reminisced about the freedom and lack of scheduling we enjoyed as kids. My wife in turn expressed surprise about the amount of information I obtained in such a short period of time. But I wasnt surprised; in our ever more connected world, theres still no substitution for face-to-face communication.

Segar, who is an expert on developing top-notch conferences, makes the point that a simi-lar level of interaction occurs among conference attendeesbut he adds the caveat that theres the added pleasure of potentially seeing your new friends again. I find it strange, yet enjoy-able, to meet people once a year and expand my connection on each occasion in unforeseen ways, he states.

The same principles hold true for experi-ences. I can watch a travel video about Paris, I can even go online and view a live webcam at the Eiffel Tower, and I can surf the web to find fascinating information about the construction of that monumental structure. But theres no substitute for actually being there, for climbing the steps to the top, hearing the sounds of the tourists around you, and for looking out over that fabulous city just as the sun is setting. Or

think about any sports event. Your view is going to be much better on a 50-in. high-definition television, your seats are certainly more com-fortable, and you get the insight of a profes-sional commentator. But who wouldnt rather be at the ballpark?

Last year, AISC initiated an event called SteelDay. Held the last Friday in September, this educational and networking event is an opportunity to get up close and personal with steel. Events are held throughout the country at fabrication shops, steel mills, galvanizing facilities, and service centers. Most of the events have educational components (and many offer food and drink). As Richard Miles from Sparks Engineering in Round Rock, Texas, reported: SteelDay gives you an appreciation for what goes into your designand the efforts to recycle/be environmentally friendly. And as Dave Haugland from AHJ Engineers in Boise, Idaho, said: Its a good chance to interact with the design and construction players in a non-project, relaxed atmosphere while learning about their part of the project.

This year were expecting more than 200 SteelDay events. You can find out about the one closest to you (and yes, there are events expected in every state) by visiting www.steelday.org.

Plan to attend a SteelDay event. See first-hand what goes into your steel project. Meet some new people. Its even better than striking up a conversation with a stranger on a plane.

SCOTT MELNICKEDITOR

Copyright 2010 Design Data, Inc. All rights reserved.

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JULY 2010 MODERN STEEL CONSTRUCTION 9

IF YOUVE EVER ASKED YOURSELF WHY? about something related to structural steel design or construction, Modern Steel Constructions monthly Steel Interchange column is for you! Send your questions or comments to [email protected].

steel interchange

Restrained BeamWhat constitutes a restrained beam for fire-rating purposes?

You can find a good listing of what constitutes restrained or unrestrained ratings in Table X3.1 of ASTM E119, Appendix A. For steel framing, this table classifies steel beams welded, riveted or bolted to the framing members as restrained.

A good article titled Restrained Fire Resistance Ratings in Structural Steel Buildings by Gewain and Troup, appeared in Engineering Journal, Second Quarter, 2001, and can be found online at www.aisc.org/ej. Search under either authors name and the year. The download is free for AISC members.

Section 4.3.2 in Appendix 4 in the AISC Specification for Structural Steel Buildings (AISC 360-05) states, Steel beams, girders and frames supporting concrete slabs that are welded or bolted to integral framing members (in other words, columns, girders) shall be considered restrained construction.

Kurt Gustafson, S.E., P.E.

Double-Angle Compression MemberThe term rib in Equation E6-2 of the AISC 360-05 Specification is defined as radius of gyration of individual component relative to its centroidal axis parallel to member axis of buckling. Does this mean that rib will be equal to rx of individual angle for LLBB angles, while it is equal to ry of the individual angle for SLBB angles?

No. I presume that since you are evaluating a built-up angle member with an LLBB configuration, the bolts are through the long legs. These bolts will be subjected to shear when the built-up member buckles about the Y-axis, which lies in the plane between the long legs. Thus, rib is equal to ry of the individual angle, since that angle axis is parallel to the Y-axis of the built-up member.


Peak StressesDoes the AISC Specification define acceptance criteria for steel when using finite-element modeling to assess the stress distribution?

No. Assessment of results employing finite-element modeling techniques is really a matter of engineering judgment. The AISC Specification limit states are based on use of average stresses in most cases; not peak stresses as may result from a finite element analysis. When such is used, engineering judgment is involved as to how this may relate to the Specification parameters, and is beyond the scope of the Specification. Localized stresses in members are assumed to redistribute through inelastic deformation thus justifying the use of average values. Where such localized stresses can be cause for failure, such as at net sections, the Specification accounts for them separately. Please note that AISC typically deals in member strength values that correspond to the entire member cross-section,

while finite element programs are likely to give stress values that vary across the member cross-section.

Kurt Gustafson, S.E., P.E.ASTM A307 BoltsWhy are ASTM A307 bolts not recommended for slip critical connections? Can they be used in low demand slip-critical connections?

ASTM A307 bolts are a carbon steel fastener with lower strength and not suitable for pretensioning; the bolt would just stretch without much residual pretension if you were to try to pretension it. Because you cant induce a pretension of any significance, you cant develop the clamping force necessary to accommodate either a pretensioned or slip-critical installation.


Weld for Single-Plate Shear ConnectionOn page 10-101 of the 13th edition AISC Steel Construction Manual, it is indicated that the leg size of the double fillet welds for a single-plate shear connection is required to be 58 tp. Is there a check required of the support base metal to which the weld is applied?

Yes. Any base metal to which a fillet weld is applied must be capable of developing the required shear being transmitted through the fillet weld. The procedure for making the connecting element rupture strength at the welds is shown on page 9-5 of the 13th edition AISC Manual. In the case of a single-plate shear connection being welded on only one side of the support element, each weld will have a unique shear plane, and thus the tmin = 3.09 D / Fu equation for FEXX = 70ksi welds will apply. If there are single-plate shear connections with equal leg sizes being applied on exactly opposite sides of the supporting element, the tmin = 6.19 D / Fu equation for FEXX = 70ksi welds will apply.

Note that these checks are based upon the support thickness developing the strength of the fillet weld(s). If the actual thickness did not meet the minimum required thickness, it is permissible to use a more exact approach to determine the actual loading of the web and resulting required thickness. Most webs will meet the above checks, however.


Flexure of Flat PlateHow can I determine the strength of a flat plate bent about the strong axis?

Section F11 of the AISC Specification (a free download at www.aisc.org/2005spec) defines the limit states of yielding and lateral-torsional buckling of rectangular bars and rounds in flexure. The limit state of lateral-torsional buckling will generally define the flexural strength of relatively thin, laterally unbraced plate members bent about the strong axis.



steel interchange

Steel Interchange is a forum to exchange useful and practical professional ideas and information on all phases of steel building and bridge construction. Opinions and suggestions are welcome on any subject covered in this magazine.

The opinions expressed in Steel Interchange do not necessarily represent an official position of the American Institute of Steel Construction and have not been reviewed. It is recognized that the design of structures is within the scope and expertise of a competent licensed structural engineer, architect or other licensed professional for the application of principles to a particular structure.

If you have a question or problem that your fellow readers might help you solve, please forward it to us. At the same time, feel free to respond to any of the questions that you have read here. Contact Steel Interchange via AISCs Steel Solutions Center:

One East Wacker Dr., Suite 700Chicago, IL 60601UFM "4,"*4$ t GBY [email protected]

Kurt Gustafson is the director of technical assistance in AISCs Steel Solutions Center. Heath Mitchell, Brad Davis and Larry Muir are consultants to AISC.

The complete collection of Steel Interchange questions and answers is available online. Find questions and answers related to just about any topic by using our full-text search capability. Visit Steel Interchange online at www.modernsteel.com.

Historic Beam DesignationI am investigating a building designed in 1967, with the plans dated February 1, 1968. The plans indicate some roof beams as being 18B35. I have a 6th edition AISC Manual dated 1967 and this shape is not indicated. Can you tell me where I might find the properties of this shape?

There was a grouping of light 18-in. beams (W1840 and W1835) that were added in the 7th edition AISC Manualpublished in 1970. I believe that these shapes were added by some mills in the late 1960s. It is possible that this may be what is designated as an 18B35, even though it was designated as a W1835 by the time the Manual was published. You may want to check the dimensions of the shape against those listed in the 7th edition AISC Manual to see if that is what you have.

In case you do not have a copy of the 7th edition Manual, AISC has developed two sources of information pertaining to historic shapes. AISC Steel Design Guide 15 is a reference for historic shapes and specifications. There is also the AISC Shapes Database v13.1H, where the H stands for Historic. Both of these resources are available as free downloads by AISC members at www.aisc.org/epubs or can be purchased by others.

Kurt Gustafson, S.E., P.E.Rivet ReplacementWhen removal of existing corroded rivets is required, what is the appropriate nomenclature and tightening method for high strength bolts being used as a replacement? Should slip-critical or pretensioned connections be considered? What are the differences in installation and inspection methods between the slip-critical and pretensioned options?

The bolt installation methods for pretensioned joints and slip-critical joints are identical. The only differences are the surface preparation and inspection of the faying surfaces of slip-critical joints. Additionally, slip-critical joints are intended for new construction, not the retrofit that you describe.

If your main concern is replacing the clamping force of the rivet, the bolts should be specified as pretensioned. You may need further notes on your details to ensure that the construction sequence does not result in the degradation of the faying surfaces of the joint, or the loss of clamping force in any previously pretensioned bolts. However, if a snug-tightened joint would be permitted by todays standards, there is no need to do anything more than install the bolts as snug-tightened.

Heath Mitchell, P.E.

Table B4.1 Compression or Flexure?Table B4.1, Case 1 description says Flexure in flanges of rolled I-shaped sections and channels. For bending about the major axis, the stress distribution on the top flange (for a simply supported beam subject to gravity loads) is uniform compression. Therefore, should Case 3 be used for the flange classification?

No. Case 3 applies to a member that is subjected to uniform compression on the entire cross-section. The limiting lambda values are derived differently for a member subject to flexure as compared to a member subject to uniform compressive stress.

Brad Davis, Ph.D., S.E.

Maximum Bolt TensionWe are installing ASTM A325 galvanized bolts by the turn-of-nut method. We are following the preinstallation verification procedure using a tension calibration (Skidmore) unit and making sure that we meet the extra 5% over the 70% mininum tensile strength. I understand there is not an upper limit of the applied pretension on the bolt, with the upper limit in effect resulting in the bolt breaking, or threads stripped during installation. The question has come up if this is true, then why cant we reuse a bolt (A325 galvanized) if it has been previously pretensioned by the turn-of-nut method.

The intent of the RCSC Specification is not to allow bolts to be tightened to the point of breakage or thread stripping. Rather, the pretensioning procedures are intended to essentially yield the bolt. Because at that level of strain, the stress-strain curve has hit a plateau, some degree of strain above the target is not detrimental to the performance of the connection.

All bolts possess some degree of ductility, which allows them to reach some strain beyond this plateau without fracture. However, only ungalvanized A325 bolts have been deemed to have enough ductility to undergo repeated tensioning.

The degradation of galvanized ASTM A325 (and black ASTM A490) bolts in repeated cycles of pretensioning is illustrated in Section 4.5 of the Guide to Design Criteria for Bolted and Riveted Joints, 2nd edition, which is available as a free download at www.boltcouncil.org. This clearly shows why galvanized A325 (and black A490 bolts) are not allowed to be reused.

Larry S. Muir, P.E.

Block ShearShould block shear failure be considered for the connection elements loaded in compression?

No. Block shear consists of a shear failure along one or more planes combined with a tension failure along one of more planes. Block shear cannot occur without a plane subjected to tension and therefore need not be checked for compression loads.

Larry S. Muir, P.E.


steel quizLOOKING FOR A CHALLENGE? Modern Steel Constructions monthly Steel Quiz tests your knowledge of steel design and construction. The answers to this months Steel Quiz can be found in the 2005 Specification for Structural Steel Buildings (available as a free download at www.aisc.org/freepubs) and AISC Steel Design Guide 19, Fire Resistance of Structural Steel Framing, also a free download for AISC members at www.aisc.org/epubs.

1 Which ASTM standards covering bars are referenced in the AISC Specification?

2 True/False: The AISC Specification cannot be used to design steel castings and forgings.

3 According to the 2005 AISC Specification, when should the contract documents require that shapes be supplied with Charpy V-Notch (CVN) toughness of 20 ft-lbs absorbed energy at +70 F?

4 True/False: Heavy W-shapes (those with flanges that exceed 2 in. in thickness) require special material, design, and fabrication/erection considerations because the perimeter of the heavy cross section is a zone of coarse grain structure and reduced toughness. 5 What is the maximum permitted

temperature for heating operations per the AISC Specification?

a) 800 F b) 1,000 F c) 1,100 F d) 1,200 F

6 True/False: Steel stud shear con-nectors shall conform to the requirements of AWS D1.1.

7 Which methods of design for fire conditions are recognized by the AISC Specification?

8 True/False: The f ire perfor-mance of concrete-filled HSS columns can be adverse ly affected if vent holes are not provided in the steel section.

TURN TO PAGE 14 FOR ANSWERS

9 What are two commonly used re f e re n c e s t o d e t e r m i n e proprietary assembly ratings when designing for fire conditions using Qualification Testing?

a) IBC and the UL Fire Resistance Directory

b) IBC and ASCE 7 c) ASCE/SFPE 29 and IBC d) ASCE/SFPE 29 and the UL Fire

Resistance Directory

10 Is it permissible to use shapes in assemblies that are different from the shape that was rated by test-ing such as that shown in the UL Fire Resistance Directory?

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steel quiz ANSWERS

1 According to Section A3 of the 2005 AISC Specification bars conform to ASTM A36, A529, A572, and A709 are referenced.

2 False. Cast steel that conforms to ASTM A216 Grade WCB with Supplement S11, and steel forgings that conform to ASTM A668, fall within the scope of the AISC Specification.

3 The supplemental CVN require-ment of 20 ft-lbs absorbed energy at +70 F is required for plates and shapes with flanges that exceed 2 in. in thickness, used as members subject to pri-mary tensile forces due to ten-sion or flexure and spliced using CJP groove welds.

4 False. It is the core area of these shapes, not the perimeter, that can have a coarse grain structure and reduced level of toughness. For more information on this sub-ject, download the NASCC con-ference proceedings for session E13, presented by Duane Miller, available for no charge at www.aisc.org/2010nascconline.

5 Trick question, sorry. Both (c) and (d) are correct depending upon the steel grade. According to Section M2.1 of the 2005 AISC Specification temperatures of heated areas shall not exceed 1,100 F for A514 and A852 steel or 1,200 F for other steel.

6 True. According to Section A3.6 of the 2005 AISC Specification steel stud shear connectors shall conform to the requirements of AWS D1.1.

7 Two methods of design for fire conditions are recognized in Appendix 4 of the 2005 AISC Specification: Qualification Test-ing and Engineering Analysis.

8 True. The fire performance of a concrete-filled HSS column improves when heat absorption occurs as the moisture in the concrete is converted to steam. The resulting steam must be released through vent holes in the steel section. See Section VI of AISC Steel Design Guide 19 for additional information.

9 (d) ASCE/SFPE 29 and the UL Fire Resistance Directory are two commonly used references when fire-resistant designs are based upon qualification testing. See Section IV of AISC Steel Design Guide 19 at www.aisc.org/epubs for more information.

10 Yes. All test assemblies are based upon a specific member size with spray-on thickness adjustment formulas to account for use of other shapes.

Anyone is welcome to submit questions and answers for Steel Quiz. If you are interested in submitting one question or an entire quiz, contact AISCs Steel Solutions Center at 866.ASK.AISC or at [email protected].

At least it was to the construction team on the Missouri River Bridge

project when their initial concrete design priced over budget at almost

$45 million. They then had to scramble for other options.

Turned out the solution was steel. After coming up with a new design,

they turned to Nucor. And we were able to help them build a

beautiful, easy to maintain and environmentally friendly bridge at less

than half the cost of concrete. Who wouldve thought.

www.nucoryamato.com

Its Our Nature.


Newly Certified Facilities: May 131, 2010

news

Newly Certied Fabricator FacilitiesBellingham Metal Works, LLC, Bellingham,

Mass.Campbell Steel Company, Inc., Cayce, S.C.Daniel Metals, Inc., Birmingham, Ala.FitzLord, Inc. dba Vulcan Steel, Jacksonville, Fla.G.A West & Co., Inc., Chunchula, Ala.Miscellaneous Steel Industries, Inc., Kyle, TexasMohawk Northeast, Inc., Groton, Conn.Rast Iron Works, Schertz, TexasRochester Structural, Rochester, N.Y.Sierra Metals USA, Inc., Mentor, OhioSME Steel, Inc., Pocatello, IdahoTate Steel, Inc., Piedmont, S.C.Yakima Steel, Yakima, Wash.

Newly Certied Erector FacilitiesAdvanced Metal Sales, Phoenix, Ariz.B & C Steel, Inc., Denver, Colo.Best Steel, LLC., Longmont, Colo.Forest City Erectors, Inc., Twinsburg, OhioH B Welding, Inc., Pawtucket, R.I.Kesler Erection & Welding, Inc., Lexington, N.C.Mid-Valley Contracting Services, Inc., Moscow,

Penn.MW Erectors, Inc., Peoria, Ariz.Nexus Steel LLC & Inc., Tempe, Ariz.OBrien Steel Erectors, Inc., Stockton, Calif.Red Cedar Steel Erectors, Inc., Menomonie, Wis.The Walker Company, Mt. Sterling, Ky.

Existing Certied Erector Facilities

Existing Certied Bridge Component Facilities

Existing Certied Fabricator Facilities

Newly Certied Fabricator Facilities

Newly Certied Erector Facilities

Newly Certied Bridge Component Facilities

To nd a certied fabricator or erector in a particular area, visit www.aisc.org/certsearch.

People and Firms

Newly Certied Bridge Component FacilitiesBellingham Metal Works, LLC, Bellingham, Mass.

t David C. Jeanes, P.E., has retired as pres-ident of the Steel Market Development Institute (SMDI), a business unit of the American Iron and Steel Institute (AISI), after 34 years of distinguished service with the organization. Jeanes began his career working for a land developer and a steel erection firm. After serving in the U.S. Army, he joined AISI in 1976 as a codes and standards engineer and sub-sequently held a number of positions in the organization. Among other accom-plishments, Jeanes was involved in the development of durable, cost-effective high-performance steel for bridges, which is now in use in more than 300 bridges in 44 states.

t David Ruby, P.E., S .E . , has been named the 2010 Structural Engineer of the Year by the Structural Engineers A s s o c i a t i o n o f Mich igan. Ruby i s f o u n d e r o f Farmington Hills, Mich.-based Ruby + Associates and a nationally recog-nized pioneer in constructability. Early in his career, Ruby was the structural project manager for Chicagos John Hancock Building and the Sears Tower. He is the author of AISCs Steel Design Guide 23: Constructability of Structural Steel Buildings, published in 2009.

t Raymond S. Milman, P.E., senior struc-tural staff engineer with Cleveland-based Middough, was selected as the 2010 recipient of the Association for Iron & Steel Technology (AIST) Distinguished Member and Fellow Award. Established in 1975, the award recognizes AIST members who have attained eminent distinction in advanc-ing the technical development, produc-tion, processing and application of iron and steel and/or related activities of the industry and have performed meritori-ous service to the association. Milman was recognized for his expert meth-odology in structural analysis and for sharing this knowledge through AIST presentations, committee activities and published technical papers. His work has resulted in major economic savings and expanded steel industry knowl-edge relative to mill building design and construction.

The Construction Marketing Association has lauched a comprehensive rating of the Internet presence of top construction brands based on more than 50 variables. This Construction Brand Internet Index (CBII) identifies how effective a specific website domain is relative to other websites. Ratings are based on key search engine data, website meta structure, traffic, social media integration (use of blogs, Facebook, Twitter, YouTube, etc.), inbound links, indexed pages and more. Initial index ratings can be viewed at http://constructionmarketingblog.org.

Overal l , the top construct ion brands rate high due to high volume website traffic and large quantities of links, however a number of missed opportunities were identified with highly rated websites, reports CMA chairman Neil Brown. As we evaluate the top construction brands, it is apparent that we (construction) lag other sectors in Internet best practices. He says the association can help in addressing these opportunities with programs and training.

MARKETING

Web Popularity Do You Agree?


news

In conjunction with SteelDay 2010, AISC is again sponsoring a Student Photo Contest. The contest is designed to capture the essence of SteelDay and is open to any student currently enrolled in a graduate or undergraduate program at an accredited domestic college or university.

Each entry should include a set of three photographs that together pictorially dem-onstrate the combination of structural steel

and the theme Interact. Learn. Build. A brief explanation, completed application form and signed release form also are required. There is no entry fee.

Deadline for entries is Saturday, September 18, 2010. The winner will be announced on SteelDay 2010 (September 24). The winning photos will be published in Modern Steel Construction. For information and to enter, go to http://bit.ly/9pjYaU.

COMPETITION

Student Photo Contest Now Open

The Steel Joist Institute is now accepting entries for its 2010 Design Awards. The winning entries will be announced in November 2010, and the company with the winning project in each category will be awarded a $2,000 scholarship in its name to a school of its choice for an engineering student.

Awards will be presented in three categories: r Industrial (i.e., distribution centers,

warehouses and light manufacturing) r Non-industrial (i.e., office buildings,

schools, and churches) r Unique applications (i.e., projects with

a unique application of steel joists) To enter a project, visit www.steeljoist.

org/awards by August 2, 2010, for an online entry form and a complete listing of rules.

Eligible projects must be located in the U.S., Canada or Mexico, and the steel joists and/or joist girders must be manufactured by an active member of the Steel Joist Institute. A list of members can be found here: www.steeljoist.org/members. Also, projects must have been constructed within the last three years. Eligible projects include new buildings and major retrofit or expansion projects. Companies can submit more than one entry, and each will be judged separately. Projects will be evaluated based on flexibility, speed of construction, value and aesthetic considerations.

COMPETITION

Joist Design Awards Program Launched

Steel Design Guide 24, Hollow Structural Section Connections, is now available as a free download by AISC members at www.aisc.org/dg or can be purchased by others.This new guide addresses bolting and welding issues for connections involving hollow structural sections (HSS), as well as providing design provisions for various configurations of HSS connections and the applicable limit states. Some of the topics included are:

r Moment connections, including W-shape beams to HSS columns, continuous beams over HSS columns, through-plate connections, and directly welded connections.

r Tension and compression connections, including end tee connections, slotted HSS/gusset connections, end plates on round HSS, and end plates on rectangular HSS.

r Branch loads, line loads and

concentrated forces on HSS.r HSS-to-HSS truss and moment

connections.The design guide references the 2005

Specification and the 13th edition Manual. The design provisions of the 2005 Specification are presented in a convenient tabular form for easy reference and the examples give both load and resistance factor design (LRFD) and allowable strength design (ASD) solutions.

PUBLICATIONS

New Steel Design Guide for Hollow Structural Section Connections

The Design Examples and Shapes Database material contained on the CD Companion V13.0 included with the 13th edition AISC Steel Construction Manual have been updated and are now available on the AISC website. Additionally, the references from the Manual also are now available at www.aisc.org/epubs.

The new version of the Design Examples can be found at www.aisc.org/designexamples. The package includes 151 examples illustrating the application of both the 2005 AISC Specification for Structural Steel Buildings and the tables included in the 13th edition AISC Steel Construction Manual. The download is free for AISC

members and $70 for non-members.The up-to-date AISC Shapes Database

V13.2 is at www.aisc.org/shapesdatabase. It includes most of the dimensions and properties of the shapes listed in Part 1 of the Manual. Free for AISC members; non-member cost is $20.

PUBLICATIONS

New Companion Materials for Steel Construction Manual Now Online


The Thornton Tomasetti Foundation has awarded two $5,000 grants to Engineers Without Borders (EWB-USA) for their critical work on the design and construction of bridge projects in Central America. Central Michigan Universitys student chapter of EWB and the Wisconsin Professional Partners chapter, in collaboration with Marquette Universitys student chapter, were selected as grant recipients for the construction of bridges in Gualindo Arriba, El Salvador and Joyabaj, Guatemala.

We are so proud to support Engineers Without Borders extraordinary efforts in Central America, said Richard Tomasetti, chairman of the foundation. The construction of the bridges is critical to the regions infrastructure and will greatly revitalize these communities and boost economic and social opportunities.

The Thornton Tomasetti Foundation

recently partnered with EWB-USAs Project Sponsor program and committed to contributing $25,000 to the organization in 2010 through the EWB Thornton Tomasetti Foundation Grant. The Foundation distributed $10,000 for this springs grant cycle and will distribute the remaining $15,000 in this falls grant cycle. The grants are endowed to meet the mission of the Thornton Tomasetti Foundation and to provide financial support for those pursuing philanthropic activities related to engineering, design or technology for buildings and bridges. EWB-USA student and professional chapters working on projects that meet the criteria can apply for the grants.

The economic, educational and social development of more than 20,000 people has been impeded by the lack of safe and efficient means of crossing the polluted Rio Chiquito in Guatemala.

The Wisconsin Professional Partners chapter of EWB-USA joined forces with students from Marquette University in Milwaukee to conduct a site survey in preparation for a new bridge location. The EWB team met with community leaders and received a firm commitment to move forward with the project, which will provide a new steel girder bridge as an alternative to relying on the existing narrow, old bridge. Labor, financial and material resources were offered by the community to begin construction of the bridge. The estimated completion date for the project is January 2011.

The other current project is located in the mountains of eastern El Salvador, where the Central Michigan University students expect to complete that bridge in March 2011.

COMMUNITY INVOLVEMENT

Foundation Funds New Central American Bridges

Community leaders of 17 of the outlying communities along with the mayor of Joyabaj gathered to discuss needs and involvement/commitment to project.

This existing bridge was built more than 60 years ago designed as an 8-ft-wide pedestrian walkway.The new bridge will unite the outlying communities with the city if Joyabaj and provide safer access to medical care facilities, post elementary schools, and markets.

news

Steve Graziano Adrianna Stanley

CORRECTIONThe detailer for the IDEAS2 award-winning L.A. Live project was incorrectly identified in the May 2010 issue of MSC (page 49). The steel detailing should have been attributed to Steel Systems Engineering, Inc., Sherman Oaks, Calif.

The annual North America Tekla Structures BIM Awards (for-merly Tekla Model Competition) program is now accepting entries. Award categories include:r $BUFHPSZ m *OEVTUSJBM$JWJM .PEFM m 4UFFM BOEPS $PODSFUFr $BUFHPSZ m $PNNFSDJBM*OTUJUVUJPOBM .PEFM m 4UFFMr $BUFHPSZ m $PNNFSDJBM*OTUJUVUJPOBM .PEFM m $PODSFUFr $BUFHPSZ m $PMMBCPSBUJWF 1SPKFDU

Each participant will receive a special gift and winning projects for each category will receive a Tekla Structures Viewer and two tickets to the 2011 Tekla User Meeting. All North American win-ners are automatically entered into the Tekla Global BIM Awards.

COMPETITION

Entries Sought for BIM Awards Program

All Tekla Structures users are encouraged to participate. There is no fee to enter, but projects must be submitted on or before July

For more information from the Tekla website, go to http://bit.ly/crnhPZ.


Vice President of CertificationFollowing its double-digit growth in 2008, the AISC program for fabricator certication grew another 18% and its erection certication program grew a whopping 39% in 2009with similar results expected in 2010. AISC is now seeking a Vice President of Certication to help develop strategies to manage this phenomenal growth as well as to develop administrative procedures to better support the program. This dynamic and experienced individual will manage the department coordinating the program, hire the rm responsible for audit services, and coordinate with the committee responsible for developing the certication standards. A knowledge of certication procedures is less important than an aptitude for leadership, strategic management, customer service, and budgeting. The Vice President of Certication must be able to mentor a young staff and create a growth strategy to maximize participation and prots. The successful candidate will either be located in Chicago or be willing to relocate, have a minimum of 10 years of management experience, and have a solid working knowledge of construction or manufacturing industries.

Submit your cover letter and resume to [email protected].

lettersA Question About Design Guide 1Q. I noticed that Design Guide 1 was taken offline for awhile and now its back. Is there a list of what changes were made to the document compared to the second edition from 2006?

A. Thanks for the question. Actually, the new printing is a full revi-sion. There were many changes made on nearly every section of the document, so please just review the entire document for changes to clearly understand it, prior to using it.

AISCs Steel Design Guide 1, Second Edition (corrected second

printing), is now available online at www.aisc.org/dg. As with all the design guides, it is a free download for AISC members. Non-members can download the document for $60. This design guide, titled Base Plate and Anchor Rod Design, provides a useful discussion on options for dealing with short, bent and misplaced anchor rods.

What methods do you use for short, bent and misplaced anchor rods? Have you faced unique field challenges in this arena that have required some out of the box approaches? Share your insights and experience with others at www.steeltools.org.

The American Iron and Steel Institute (AISI) has published an update to its S110-07-S1-09, Standard for Seismic Design of Cold-Formed Steel Structural SystemsSpecial Bolted Moment Frames With Supplement No. 1. The standard addresses the design and construction of cold-formed steel seismic force-resisting systems (SFRS) in buildings and other structures, with focus on the special bolted

moment frame (CFS-SBMF) system.Cold-formed steel special bolted

moment frames have been widely used in industrial platforms, and the system is potentially suitable for a broad range of construction applications. Revisions and additions were made in Supplement No. 1 to ensure that the application of the design provisions remains within the configurations used in the initial research

of special bolted moment frames. The commentary on the standard is also included, which provides important background information. This standard should be used in conjunction with AISI S100-07, The North American Specification for the Design of Cold-Formed Steel Structural Members. All of these publications are available for purchase online at AISIs Publications Bookstore at www.steel.org.

CODES AND STANDARDS

Updated Seismic Standard for Cold-Formed Steel

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publications

EBY KEITH GRUBB, P.E., S.E.The JournalGoesWhat is Engineering Journal?

Engineering Journal (or EJas engineers we love our acro-nyms) is AISCs quarterly technical journal. Weve been publish-ing it since 1964.

What makes EJ different from MSC?Articles in EJ are much more technical in nature. Internally at

AISC, we joke about EJ as the home of articles with equations. But equations dont tell the whole story: EJ articles often feature design tables, design examples, and test data. EJs articles are also peer-reviewed by industry experts with interests in the fi eld in question.

Why should I read EJ?Facing challenges and solving problems is an integral part of

our jobs in the engineering and construction community. EJ tries to provide information to help us all face those challenges. For example, last year EJ published an article on design procedures for extended, unstiffened single plate shear connectionsfor those cases when a standard shear tab wasnt quite long enough. To read this article, go to www.modernsteel.com/EJsample1.

Also, seismic events have spurred research into alternative structural designs. Have you ever heard of self-centering steel frames? The concept is rather simple: allow a building to rock during an earthquake event, but provide a structural fuse to dissipate energy and a means to draw the building back to its original position after rocking. (Check out this YouTube video here: http://bit.ly/d8J8Fp). You can be assured that EJ will have articles covering this topic as it develops.

What makes EJ different from other technical journals?Many technical journals have a strong academic tendency. EJ dif-

fers in that we try to provide articles with practical applications as well. For example, one of the most popular EJ articles of all time is

Field Welding to Existing Structures, by David T. Ricker. This arti-cle is also available as a free download by going to www.modernsteel.com/EJsample2.

How do I get EJ?All EJ articles,

current and past, are available as Adobe Acrobat PDFs through the EJ search on AISCs

website at www.aisc.org/ej. Members should make sure they are logged in, because viewing EJ articles is free for members. Non-members pay a nominal fee through the AISC online bookstore.

Printed copies of EJ are a member benefi t. Each member fi rm (professional, full, associate, etc.) gets one mailed copy of EJ to circulate and fi le in their paper library.

An exciting new development is the delivery of EJ as a digital journal. In addition to the paper copies we already send, AISC is now providing the current edition of EJ in digital format, via a link in a quarterly email. The digital format lets you browse EJ as soon as its available, without waiting for a paper copy to circulate to your desk. When each new issue of EJ is available, youll receive a fresh link via email. First Quarter 2010 (the issue available when this arti-cle went to press) is available here: http://bit.ly/cHb6DW.

The navigation and controls are fairly self-explanatory and very similar to the digital edition interface for MSC. Hyperlinks within the document allow you to jump directly to articles from the cover; the zoom feature lets you enlarge the page and pan around; and the print feature lets you easily highlight only those pages youd like to print.

The search feature allows you to search the current issue for any terms youd like. Because older EJs do not exist in digi-tal edition format, the digital edition search function does not access them. But all materialcurrent and pastis accessible via the PDF search at www.aisc.org/ej.

Is that all?Not quite. AISC is working on enhancements to the EJ home

page and search function that will provide clearer results and more information about each article. Well be sure to let you know!

Keith Grubb, P.E., S.E., is senior research engineer with AISC and editor of Engineering Journal.

A few words about AISCs Engineering Journal and the

debut of its online edition.

PRINT allows you to select speci c pages or the entire journal for printing.

Preset the level of magni cation you prefer. When you click on the ZOOMbutton it applies that percentage.

CONTENTS provides linked article headlines so you can quickly jump to the speci c articles.


EEVERY CONSTRUCTION PROJECT has its challenges, as any engineer and contractor will attest. But some, such as the Seton Womens Center in Austin, Texas, stand unique in their complexity.The overriding challenge was that there was only one open space available on the 20-acre campus. That meant the new Wom-ens Center had to be carefully squeezed into the opening between the existing nine-story Seton Medical Center hospital and an adja-cent medical office building.

This six-floor, 128,000-sq.-ft addition is shoehorned between two existing facilities, said Dan Vickers, an architect and project manager for Seton Network Facilities. The existing facilities are askew to the city grid. The new addition matched the city grid, which led to skewed connections at the interface point with the Womens Center. This was the only solution within our master

plan to accommodate the need for growth, given the previous additions to the campus.

But solving the geometric part of the puzzle was only the first part of the solution. Complicating the construction project was the requirement that the adjacent hospital remain open as a 24-hour facility, including ambulance and helicopter traffic, which demanded critical construction scheduling and reduced construc-tion work areas on premises.

Capping the list of project challenges was a design that called for the Womens Center to cantilever 85 ft over the two-story Emergency Services department on the southwest corner of the Medical Center.

Facing these unique construction considerations, the general contractor understood that it was critical to engage in early dis-cussions with specialty subcontractors for material procurement, fabrication and erection of the steel superstructure.

healthcare

Expansion is Cut to Fit

BY MATTHEW GOMEZ, P.E., S.E.


Getting a head start on the cooperative effort

pays off for the Seton Womens Center.

The answer was to use a program called Fast-Frame offered by Gerdau Ameristeel. The program brought together a steel mill, a steel fabricator, a connection engineer, and a steel erector, all of whom were allowed to work closely with the Engineer of Record.

The philosophy behind the Fast-Frame approach is simple: Bring in the specialty steel contractor team in a design-assist role as early as possible to evaluate ways to optimize the cost and schedule of the deliv-ered steel structure, and to address project specific goals. Because the program is led by the steel producer, the team is able to ensure optimal material selection, with guaranteed material pricing for the duration of the project, and on time delivery of material to the fabricator.

The integrated team examines trade-offs between material costs, fabrication labor costs and field labor costs. Each project brings a differ-

Matthew Gomez, P.E., S.E., is the Ger-dau Ameristeel Fast-Frame National Sales Manager. The company is the second largest mini-mill steel producer in North America, with annual manufacturing capacity of approximately 12 million tons of mill fin-ished steel products. Through its vertically integrated network of mini-mills, scrap recycling facilities, and downstream opera-tions, Gerdau Ameristeel serves customers throughout the U.S. and Canada.

Cantilevered trusses were assembled and stacked with dunnage on the fifth floor of the building during construction. Pictured are ironworkers from Deem Steel Erectors.

Cranes lift one of two trusses into position after assembly on the fifth floor of the Womens Center during construction. The two cantilevered trusses connected to create the southeast corner of the new building, with three levels of framing hanging below the trusses.

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Ironworkers in personnel lifts guide the south wall truss into position. Note the back gusset plate already in position on the column at left, facilitating the bolt-up connection.

A new entrance and lobby in the existing hospital was constructed, accessed by a driveway below the Womens Center addition.

Gerdau Ameristeel


The engineer determined the truss con-fi guration and load requirements, Griffi n said, then the steel team came in with new designs for the trusses and connections.

The connections originally were envi-sioned as gusset plates, shop welded to the wide-fl ange members and fi eld welded into notched ends of the HSS members, which required a signifi cant amount of shop time. Lastly, the truss members would be fi eld-assembled and welded into place. How-ever, because of the tight site conditions, the fi eld assembly had to be done within a short period of time.

It was a tight fi t on the construction site, which made scheduling and sequencing of material delivery very important, said Denny Dinsmore, Rogers-OBriens senior fi eld superintendent. There was no room on the campus to store material. We needed a sequence that allowed us to handle each piece a minimum amount of times.

The alternative design solution offered by the integrated team was to use W-shapes for all members, and all of similar depth to simplify connections. Connection would be made with bolted side plates on either side of the cord faces. The trusses would be shop-assembled to ensure fi t-up, then

ent set of challenges and criteria (e.g., site con-ditions, project schedule, budget constraints, BIM enabled capability, LEED accreditation, etc.) that requires a unique solution.

Early in the design process, and prior to award, the steel team was asked to review the Womens Center progress drawings to pro-vide suggestions for improvement. Because the design was still in development, many of the design and constructability issues were still on the table for discussion. That allowed the team to offer alternate solutions that had minimal impact on design and maximum impact on cost savings. An initial budget was developed and submitted to the general con-tractor for evaluation, and a target was set for developing value engineering options.

The fi rst area targeted for optimiza-tion dealt with the construction of the two major trusses that would be used to support the cantilevered southeast corner of the building. The original design used wide-fl ange sections as the top and bottom truss chords, with HSS sections for the vertical and diagonal members.

There can often be a big difference between how it looks on paper and how its fabricated, delivered and erected, said Greg Griffi n, project manager for general contractor Rogers-OBrien. An integrated team brings into the picture all of the pro-fessionals who know best how the project comes together properly.

One example involved the truss design.

Thwarting Murphys LawIt was critical that construction of the Seton Womens Center project go smoothly, especially

given the need for the existing facilities to remain open 24/7. And from the participants perspec-tive, building an integrated, committed teamincorporating the steel mill, fabricator, detailer and connection engineervery early in the process was a huge step in the right direction.

The integrated project team made this project successful, said Greg Grif n, project manager for general contractor Rogers-OBrien. The complexities of this project were such that early involvement of the steel team helped solve a lot of issues.

Architect Dan Vickers, Seton Network Facilities project manager, summed up his impres-sions of the project delivery team with high praise. I like establishing relationships with good companies you trust, Vickers said. Despite the proximity of existing facilities and other hid-den conditions, the construction of the Womens Center was very successful. We brought in this team for their expertise and they delivered a great project.


broken down for transportation, and finally bolted together at the site.

The initial drawback to this option was that these members were slightly heavier than the initial HSS equivalent; however the unit cost of the W-shapes was signifi-cantly lower at the time of procurement than that of the HSS shapes, resulting in a minimal differential in material cost.

A key advantage of the alternative design option was that it significantly reduced the labor time (and thus cost) for both shop fabrication and field erection. Adopting the alternative solution allowed a majority of the fabrication to be performed by com-puter numerically controlled (CNC) equip-ment. Members were cut and drilled using CNC beam lines, and the gusset plates were cut and drilled using a CNC plasma table.

As the design progressed it became clear that the space and time available to shake-out and assemble the two trusses at grade level would be even more limited than first anticipated. As a result, the team decided to assemble the trusses on the fifth floor of the building, one atop the other. That required significant coordination among the fabri-cator, erector and connection engineer to coordinate support points and to ensure that the floor members and their connec-

tions were adequate to support the added weight of the trusses as well as to maintain truss stability during erection.

This same strategy also was applied to the design of the vertical brace frames, changing the braces from HSS members to wide-flange members, resulting in additional savings in cost and field erection time. In this case, con-nections would be made using bolted con-nections with claw angles on the flanges and side plates on the webs to transfer axial loads. As with the trusses, that significantly reduced the labor time (and thus cost) for both shop fabrication and field erection. The members were cut and drilled using CNC beam lines, the claw angles were cut and drilled using a CNC angle master, and the gusset plates were cut and drilled using a CNC plasma table.

Other areas led to additional cost savings and schedule improvements, including:

Reducing the number of column splices, which added weight but cut fabrica-tion and erection time and costs.

Revising work points where multiple members met at skewed connections, which improved constructability and reduced fabrication and erection time and costs.

Revising the HSS support framing to be wide-flange beams for a pedestrian

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Viewing the construction from the north, the southern wall truss in place and the crane is lifting the longer western truss into position.

Advance Steel


bridge that connects to the existing medical office building, with the same benefits as changing the trusses.

Revising the floor framing to minimize the number of different member sizes in a typical bay. That allowed the detailer to simplify the shop drawings, reduced retooling in the shop, and simplified the erection planning. It also allowed the mill to provide material in bundle quantities and to nest the lengths more effectively, resulting in reduced waste.

It was a team effort, Griffin said. There are benefits when everyone comes together early, and throughout the project; it will more likely be a successful project, and we can give the owner the best value for the money.

And thanks to the integrated approach, the savings on this project can be quantified. By the end of construction, the integrated deliv-ery team identified approximately $210,000 of value engineering savings for the $3.4 mil-lion steel portion of the project.

The completed Womens Center building, seen from the north, is defined by a silver/blue cladding. Below the building is a drive, access-ing a new entrance to the hospital (to the left).

OwnerSeton Healthcare Network, Austin, Texas

ArchitectSTG Architects, Austin, Texas

Structural EngineerDatum Engineers, Austin, Texas (AISC Member)

Connection EngineerStructural Solutions, Inc., Fort Worth, Texas (AISC Member)

Steel ErectorDeem Erectors, Longview, Texas (SEAA Member)

Steel FabricatorCrist Industries Inc., Fort Worth, Texas (AISC Member)

General ContractorRogers OBrien Construction, Austin, Texas

Structural SoftwareSDS/2, RISA-3D, RAM Steel

Gerdau Ameristeel

TTHE JOURNEY FROM an overcrowded office campus to com-fortable, cohesive, and flexible workspaces began with a Fargo, N.D., software companys need to expand its workforce. At the same time, the company realized it did not have enough space for new hires. In fact, there was not even enough space for current employees, who had spilled out of the two existing buildings into leased space nearby, but off the campus, incurring additional cost and fracturing the workforce. As plans developed for a new build-ing, it became clear that efficiency could be increased by bringing back on campus the resources that currently took employees off campus, such as eating spaces, meeting rooms, and presentation facilities. With this new perspective, the idea to build a new build-ing became a plan to build two.

The company engaged three Minneapolis firms to work on its new two-building project: architects Perkins+Will, with Meyer Borgman Johnson as structural engineers, and JE Dunn as general contractor. Criteria for the project included an architectural design

that complemented, but did not copy, the existing two buildings on the campus, and that would be as memorable as it was functional. No big box buildings. The owner also was interested in creating work spaces of a scale conducive to teamwork and collaboration among employees. The desire was for an open architecture capa-ble of being flexible and responsive to changing needs. Because the need was imminent, programming began immediately with the project team designing within the constraints presented by both owner and site.

Aside from the owners desires, the site itself presented strong challenges mainly because of the areas geology. Fargo sits within the shores of glacial Lake Agassiz, the remains of the last glaciers which melted some 10,000 years ago. This ancient lake bed comprises about 100 ft of clays and very fine silts, and for 10,000 years, these materials have been slowly drying out from the top down. To date, this desicca-tion has extended roughly 8 ft below ground level. Below this eleva-tion, the ground consists of unconsolidated, undrained clay with very

An urgent need for larger facilities was quickly met, thanks to exibility, cooperation, and the selection of steel framing.

low-rise ofce

Growing an Office


low bearing strength. Deep foundations can be built, extending 100 ft or more to rock, but they are expensive. If economical shallow foundations are to be used, a relatively light structure is necessary. Fargo is also known for cold winters and strong winds. Concrete construction through the winter requires extensive tenting and heating and is at constant risk because of the wind.

Combining the owners requirements with geology and climate considerations, structural steel framing was the obvious choice. Structural steel allows large open bays (varying here from 26 to 40 ft in floors), it can be erected quickly regardless of wind and winter weather, and it is lighter than concrete.

Schematic design began in the spring of 2007 and by mid-September, both buildings were sufficiently defined so that foundation plans and structural steel drawings could be issued. The Office build-ingits working name as well as its anticipated functionwas configured in two parallel pieces called bars with a large glass atrium between them. Communication between the two bars was enhanced with footbridges across the atrium at the second floor.

Development of the second building, with the working name

on the Plains BY MICHAEL HEMSTAD, P.E., S.E.

Michael Hemstad, P.E., S.E., is an associate and structural engineer at Meyer Borgman Johnson, Minneapolis. He has more than 20 years of experi-ence in the design of various structures and has performed inspection and load rating of more than 1,000 bridges in several states. He also has significant experience with rehabilitation projects, restoration of historic structures, and design-build construction.


Completion of the new Office (left) and Amenities buildings on this office campus permitted the entire company workforce to work within close proximity and in styl-ish and comfortable surroundings.


of Amenities, lagged slightly as the architects assembled project teams for each building. It took shape as a rela-tively rectilinear cafeteria/kitchen area on the ground floor with a variety of meeting spaces and outdoor terraces above. An adjacent tall, triangular, single-story dining area surrounded with glass rendered the building more or less trapezoidal in plan.

The architect envisioned both buildings as modernistic and functional whose structure would provide much of the aesthetic treatment, especially the interior. Thus, much of the structure remains exposed. Round HSS were chosen for columns because of their simple form. Many areas had no ceilings or partial ceilings, but left the overhead fram-ing exposed. For this reason, the architect requested that all beams framing any given area be the same depth. In this and many other instances, a small upcharge in steel quantity and cost was offset by other considerations. Where possible, simple bolted shear tabs were used for connections, as they are visually the cleanest and least obtrusive connections, in addition to being the most economical and easiest to erect.

As the architectural design continued to gain definition, our choice of steel framing proved to be a sound one. Both buildings demanded significant cantilevers, large suspended wall areas, and long spans supporting glass and other visually light elements, and would have been fundamentally differ-ent architecturally if built of other materials.

The exterior skin of both buildings is a combination of curtain wall, brick, and weathering steel panels. To express these walls cleanly, especially the curtain wall, the archi-tect requested that columns be held several feet inside of the walls, requiring welded cantilever connections through the columns. Variations on these details became one of the structural signatures of the buildings.

In the large presentation spaces, desired roof heights combined with a mechanical requirement for very large ducts steered us to use bar joists, deeper than necessary, with the ductwork running through the joists, rather than running the ducts beneath the roof structure, which would have been easier to install.

Lateral systems were also challenging. In the Office building, each bar has a stairwell at both ends, so these spaces were designed as simple shear wall buildings, with an expansion joint between the two bars. However, the Amenities building uses open stairs inside, and the exterior walls are primarily glass curtain wall. A small elevator shaft was available for use as a shear element at one end of the building, and a bathroom core provided some capacity at the other end, but the entire dining area was left without significant lateral support. In addition, the roof of this area is about 5 ft lower than the adjacent high roof over the meet-ing spaces, so the building lacks a continuous diaphragm.

In order to provide lateral support to the dining area, framing supporting an entry vestibule and overhead eye-brow canopy was configured as a rigid frame, with brac-

Left: This view of the dining room vestibule, from the inside looking out, shows the rigid frame on the second level. Note the offset in the pipe columns, by about half the pipe diam-eter, which was required to accommodate the difference in cladding between the upper and lower levels.

Looking from the outside at the dining room vestibule, on the left, the lower portion of the pipe columns are visible inside the glass walls. The upper clad-ding is weathering steel.

The dining area opens into a two-story open area and required a section of the second floor support to cantilever out from the columns.

ing allowed in the upper 20 ft but not the lower portion. This framing consists of large pipe columns, offset at mid-height. Bracing in the upper half consists of pairs of large angles hidden inside a weathering steel wall. The entire frame is founded on a continuous concrete footing with helical anchors at each corner to resist uplift.

Adding to the challenge, the architecture in this area calls for these columns to be inside the vestibule at ground level. Above the vestibule, there is a decorative wall that is constructed flush with the face of the vestibule glass, and into which the columns extend. Thus, they needed to offset laterally within the ceiling of the vestibule. This was done by cutting vertical slots in the lower section within the overlap zone, sliding the HSS sections together, adding stiffener/closure plates, and welding.

A similar issue arose at the east end of the building, in a large wall referred to as the Shield Wall. A large decorative wall clad in weathering steel floats above a glass curtain wall which extends about 10 ft up from ground level. Again, columns are visi-ble inside the glass, then offset horizontally and disappear into the weathering steel wall. These columns (which are primarily wind columns, i.e. bending members) are fabricated with wide-flange shapes, plates, and a lot of welding. Below the floor, the member was offset back on grid to ease erection stability concerns. In addition to strength requirements, the design paid careful attention to stiffness, ease of fabri-cation, and stress concentration and force flow at the structural discontinuities.

We resolved the discontinuity in the roof diaphragm by using a line of fabri-cated trusses at the change in height. The upper roof is supported by the top chord, and the lower roof by the bottom chord. Excess shear in the dining area roof dia-phragm transfers through the trusses to the upper roof diaphragm, and is resisted in part by the elevator and bathroom cores in the two-story space. Shear perpendicu-lar to the roof height change is resisted by column bending.

To accommodate the owners request for outdoor spaces where employees could congregate and entertain clients, two large terraces, partially shaded by steel trellises, were designed to flank either side of the Amenities building. The owners desire to provide pleasant, comfortable, and flexible spaces within which employees could work and play is reflected in the design of both

Offsetting the upper portion the pipe column involved a 1-ft, 6-in. overlap with slots in the lower portion of the column into which the upper pipe was slipped. Also note the inclusion of plates at top and bottom.

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This detail of the shield wall column shows the 2-ft offset, accomplished using wide-flange shapes, plates, and welding.


ArchitectPerkins+Will, Minneapolis and Chicago

Structural EngineerMeyer Borgman Johnson, Minneapolis (AISC Member)

Steel Detailer and FabricatorMid America Steel, Fargo, N.D. (AISC Member)

General ContractorJE Dunn, Minneapolis (AISC Member)

Structural SoftwareRAM, Revit

These trusses provide the step up in the dining area of the amenities building. The angles on the top chord are what transfer the diaphragm shear through the truss.

Fast-Paced Steel DesignSteel design for this project was pro-

duced primarily in RAM. Once each build-ings main structure was dened and sized, a model was exported from RAM to Revit. Drawings were then advanced based on the Revit structural model. The building model was shared and updated weekly among all members of the design team.

The initial steel drawings were intended as mill-order drawings and con-tained little detail. Due to the extremely rapid pace of development, they were regarded by the entire design and con-struction team as continuously evolving, snapshot-in-time documents. The entire team worked hard throughout the proj-ect to digest this stream of information and produce and erect structural steel, enabling the architecture while honoring the schedule and budget.

Obviously, document control and communication became a critical (and time-consuming) part of this project. Changes and clarications communicated from owner to design team were often rst designed, sketched, and issued to the contractor, fabricator, and eld inspector (and, later, the erector) and then incorporated into the structural drawings with the usual change clouds and revision notations. Drawings for each building were revised and formally re-issued every other week, hop-scotching over each other. The structural engineers talked frequently with the architect to determine which areas were still in ux and which areas were more likely to remain unchanged, then shared this information with the construction team. Formal weekly meetings served as much to record these exchanges as to generate new ones. The fabricator was able to absorb some of these changes within its existing steel inventory. When this was not feasible or desirable, discussion usually produced a solution that worked for all parties.

Unlike the classic design-bid-build for-mat, design and, especially, drafting of these buildings overlapped signicantly with fabrication and construction. As draw-ings progressed through mill order to con-struction stage, fabrication and construc-tion kept pace and at times threatened to get ahead of them. Again, constant com-munication with the contractor was neces-sary in order to deliver design for what was to be built next. Just in time, a concept originating in manufacturing to reduce storage and inventory costs, became part of our vocabulary to reduce contractor downtime and engineering redesign, yet allow the architects vision to emerge.

buildings and their surrounding outdoor spaces. Though the journey to completion was often challenging, the completed proj-ect brings an architecturally rich environ-ment to this northern prairie location, as well as the potential to increase employee satisfaction and productivity.

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DDETROITS NEW MEXICANTOWN Bagely Street Pedestrian Bridge is the first cable-stayed bridge in the state and part of Mich-igans $230 million I-75 Gateway Project. The two-span, cable stayed structure crosses 10 ramps and roadways, including both I-75 and I-96, and provides a vital link between the east and west sides of Detroits Mexicantown community.The total bridge length is 417 ft, with a main span of 276 ft

and a back span of 141 ft. The forestays are arranged in a fan con-figuration and are inclined in both the longitudinal and transverse directions. The bridge features a unique asymmetrical design, with a selected look of a single cable plane. A single 155-ft-tall inclined pylon provides the upper support for the cables, which form an eccentric plane and are anchored at the lower end to a tapered, trapezoidal, single-cell steel box girder.

The back span balances the forces imposed by the forestays and anchors into a deadman/abutment. The welded steel, trapezoidal box girder carries the variable-width deck slab. The project incorporates

five tuned mass dampers to control vibration of the bridge super-structure. Each portion of the project, including abutments, entry plazas, barriers, and fencing employs architectural finishes with three-dimensional variations, and is therefore highly stylized aesthetically.

The bridge lies on a tangent horizontal alignment. The western span expands from 15 ft, 3 in. to 21 ft, 6 in. while the shorter east-ern span widens even more dramatically, from 21 ft, 6 in. to 34 ft. The pedestrian walkway entrance and exit grades of the vertical profile are at 5% grades and are connected by a 200-ft crest verti-cal curve whose midpoint is located near the pylon. The minimum vertical clearance to the closest underlying roadway is 16 ft, 1038 in. at the eastern abutment.

The structural systema single-cell box girder superstructureis supported at the westerly forespan by stay cables anchored eccen-trically to the girder shear center at the northern girder web. The eastern back span is self-supporting and also transmits compression forces introduced by the westerly forestays to the east abutment.

Featuring asymmetry in two major planes, Michigans rst cable-stayed bridge was a challenge in both design and construction.

bridges

Beautiful


TiltBY ROBERT B. ANDERSON, P.E., MIKE GUTER, P.E., AND VICTOR JUDNIC, P.E.

The new Mexicantown Bagley Street Pedestrian Bridge in Detroit crosses I-75 and I-96 and is Michigans first cable-stayed bridge.

Peter Bug

ar, URS C

orporation

On a


Robert B. Anderson, P.E., is a senior structural engineer for URS Corporation, Tampa, Fla., and has been involved in the planning, design and construction of bridges for more than 21 years. Bobs experience includes the design of five major cable-stayed bridges, several major freeway-to-freeway interchanges, as well as numerous water crossing structures. Mike Guter, P.E., is a project manager for URS Corporation in Grand Rapids, Mich. He has worked on a variety of transportation projects since beginning his career in 1993, including roles in both construction and design. Victor Judnic, P.E., is a senior construction engineer for the Michigan Department of Transportation. His experience includes the design and construction of harbors, roads and bridges over the past 21 years.

The plan and elevation view show the bridges general layout, including the pylons eccentricity in two directions.

Pylon elevation and side view.

The eccentric cable loading on the single box girder system produces torsion and lateral thrust in the girder and this is resisted by upward, downward, and lateral bearings at the west abutment and tension linkages and vertical and lateral bearings at the pylon. This figure shows that both vertical and lateral bearings are used to resist torsion. The pylon linkage and bearing system also allows translation produced mostly by thermal affects along the longitudinal axis of the bridge.

The concrete and steel pylon is eccentric in two direc-tions and also tapers in two directions from its base to its top. The foundation, at the base of the pylon, resists grav-ity loads primarily by a cluster of piles located at the line of action of the pylon. An extension of the foundation to the north helps to resist overturning loads created primarily by wind and live load effects.

Construction Activities and Scheduling This bridge required a detailed erection manual and

geometric control plan prepared by a specialty erection engineer. The erection manual outlined 62 individual stages for completing the bridge and closely followed the proposed erection plan conceptualized by the design engi-neer and included in the contract documents.

To ensure that survey discrepancies would be mini-mized and resolved quickly, the project team agreed to coordinate all surveys. The erection engineer, as part of the erection manual and ongoing computations, provided target coordinates and elevations for key points and eleva-tions, including at the pylon stay housing, at temporary shoring, at box girder splices, along the box girder deck and at all stay cable connection points.

The contractor and the owner/engineer closely moni-tored the geometry throughout construction. In one instance, the temporary guys were adjusted to correct the location of the pylon stem; however giving credit to the accuracy of the erection engineers analysis, the geometry largely agreed with the predictions.

The steel box girder erection scheme required three falsework towers to support the west span before the stay cables were installed. The contract documents included camber values to account for these three temporary sup-ports. Two additional falsework towers were provided at each side of the pylon to support the girder prior to the deck pour engaging the vertical and lateral bearings and link plates at that location. The contractor opted to com-plete the top of the pylon strut after placement of the steel

box girder to mitigate tolerance and fit-up requirements of the girder itself and the many support elements.

The first major step in the bridges construction was to build the abut-ments and the pylon. To help maintain alignment and provide support dur-ing construction and prior to installation of the stay cables and pylon post-tensioning, the pylon was temporarily guyed with four guys at two vertical levels. At each level, guys extended transverse and longitudinal to the bridge axis to maintain pylon stability and provide support in all directions.


Construction started at the east abutment, which serves as the bridge abutment; an earth anchor wall for five stay cables anchoring the front span of the bridge; and an architectural plaza that transitions from the pedestrian bridge to a much larger non-structural plaza area. This abutment also was used as the temporary anchor point for the east temporary pylon guys.

Additionally the east abutment provided the fixity for the steel tub girder, with a diaphragm cast integrally with the girder. The eastern end of the girder was temporarily supported on bearings to allow for beam rotation during the deck pour. The temporary bearings ultimately were encapsulated in concrete and the integral abutment connection was made complete.

The back span is fully supported by the east abutment and the pylon strut. The east abutment earth anchor wall is constructed on a 6-ft by 6-ft, 11-in. concrete grade beam that was integrally tied to the remainder of the abutment with steel reinforcement. The stay cables are anchored with steel forgings connected to post-tensioned anchor rods that include an end plate poured into the grade beam. A structural and architectural wall extends up from the grade beam, supporting, hiding and protecting the anchor rods. This wall has aesthetic treatments including bush-hammered and board-formed surfaces.

The west abutment was the next substructure element to be constructed. A more conventional abutment, it includes three pot bearings supporting the steel box girder vertically (both upward and downward to prevent tor-sional rotation) and transversely.

On to the SuperstructureThe east abutment earth anchor wall plate, pylon stay cable housing, and

steel box girders are shop fabricated steel components. The earth anchor plate forms a base for the five east stay cable anchor blocks. This assembly was cast into the concrete earth anchor wall. Post-tensioned bars extend from the face of this plate into a concrete beam that sits underneath the earth anchor wall.

The pylon stay cable housing is 30 ft, 6 in. in height and forms the northern half of the top pylon stem. The stay housing includes five 2-in.-thick plates with two pinholes on the west side and one pinhole on the south side for connection to the clevis-type stay cable anchorages. The placement of the stay housing was controlled by levelling nuts on 18, 1-in. anchor bolts poured into the pylon stem.

The box girder remains a constant width from the west abutment to just west of the pylon, at which point it begins to widen to its largest width at the east abutment. The top flange of the box girder also varies from being solid across the top, in areas of high torsion, to being split into two flanges on top of each web. In areas where the top flange spanned from web to web, plates were added to provide bending strength to suppo

Modern Steel Construction July 2010

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