2013 I D E A S 2 awards INNOVATIVE DESIGN in ENGINEERING and ARCHITECTURE with STRUCTURAL STEEL The Design AnD COnsTruCTiOn inDusTry recogniz- The judges considered each project’s use of structural es the importance of teamwork, coordination and collabora- steel from both an architectural and structural engineering tion in fostering successful construction projects today more perspective, with an emphasis on: than ever before. In support of this trend, AISC is proud to ➤ Creative solutions to the project’s program requirements; present the results of its annual IDEAS2 Awards competition. ➤ Applications of innovative design approaches in areas such This program is designed to recognize all team members as connections, gravity systems, lateral load resisting sys- responsible for excellence and innovation in a project’s use tems, fire protection and blast; of structural steel. ➤ The aesthetic and visual impact of the project, particularly Awards for each winning project were presented to the in the coordination of structural steel elements with other project team members involved in the design and construction materials; of the structural framing system, including the architect, struc- ➤ Innovative uses of architecturally exposed structural steel; tural engineer of record, general contractor, detailer, fabricator ➤ Advances in the use of structural steel, either technically or erector and owner. New buildings, as well as renovation, retro- in the architectural expression; fit or expansion projects, were eligible. The projects also had to ➤ The use of innovative design and construction meth- display, at a minimum, the following characteristics: ods such as 3D building models; interoperability; early ➤ A significant portion of the framing system must be wide- integration of specialty contractors such as steel fabri- flange or hollow structural steel sections; cators; alternative methods of project delivery; sustain- ➤ Projects must have been completed between January 1, ability considerations; or other productivity enhancers. 2010 and December 31, 2012; Both national and merit honors were awarded. The jury ➤ Projects must be located in North America; also selected one project for the Presidential Award of Excel- ➤ Previous AISC IDEAS2 award-winning projects were not lence in recognition of distinguished structural engineering. eligible. 2013 IDEAS2 AWARDS JURY ➤ Paul Dannels, FAIA, is a founding principal of sdi structures, institutional buildings, including the Children’s Hospital of Ann Arbor, Mich., where he develops innovative structural Philadelphia and NYU’s Vanderbilt Hall Law School with Kohn systems for buildings on behalf of numerous aspiring Pederson Fox. In her early years in New York, she specialized and accomplished architects. His designs have received in waterproofing repairs for existing buildings, a technical skill several awards and recognitions, including three AISC that has remained influential in all subsequent projects. From IDEAS2 awards. His completed projects include the 1989 to 2000 she worked on the United States Holocaust Broad Art Museum at Michigan State University, the Law Memorial Museum. Prior to Snøhetta, Anne worked with Commons at the University of Michigan and the Lamar Santiago Calatrava on the PATH Station for the WTC Corporate Headquarters in Hudsonville, Mich. Dannels is Transportation Hub. In addition, she serves on the Board of the 2013 President Elect of AIA Michigan and has served in cultureNOW, which has produced the downtownNOW MAP leadership roles with several nonprofits, including Habitat of art and cultural institutions for Lower Manhattan as well as for Humanity of Huron Valley and the Center for Faith and the Manhattan ARTNOW. She is currently working on apps Scholarship. He studied engineering and architecture at for cultural mapping across the U.S. and in Canada. the University of Michigan and worked as a construction engineer in northern Michigan before founding sdi ➤ Chris Olson is chief content director of BUILDINGS Media, structures with his business partner, Andy Greco, P.E. Cedar Rapids, Iowa, where he focuses on digital and print content for facilities professionals who operate commercial ➤ Anne Lewison, AIA, senior architect and senior design leader and public buildings. He has more than 22 years of with Snøhetta, New York, was initially drawn to the city to focus experience in the facilities management and nonresidential on social housing and pursued subsequent opportunities for architecture/engineering/construction industries. He MODERN STEEL CONSTRUCTION may 2013 ➤ The 2013 AisC iDeAs2 Awards jury, from left: Chris Olson, Charles Porter, Mark Simonides, Brian Raff, Paul Dannels, Anne Lewison, Dave Olson and Jacob Schueller. graduated with a B.A. and M.A. from the University of and the Chicago Architecture Foundation (CAF). As an Michigan and a Ph.D. from Northwestern University. adjunct professor at Northwestern University, he teaches a course in commercial real estate development for the ➤ Dave Olson’s career with AISC member fabricator Master of Project Management program. Olson Steel, San Leandro, Calif., began in 1970 as a project manager and estimator. He progressed to the ➤ Brian raff is the marketing director for the National Steel position of COO in 1995 and in 2002 became president Bridge Alliance and is responsible for providing strategic and CEO as well as the sole owner leadership and executing the national of the company. His career has marketing program that builds market A panel of design and included founding and/or leading share for steel bridges. Raff worked as a construction industry professionals several corporations engaged structural engineer before joining AISC judged the entries in three in diverse businesses, including in 2005 as its certification manager of categories, according to their real estate and shipyards. During business development. He received constructed values in U.S. dollars: the last 15 years, Olson has ✓ Less than $15 million his Bachelor’s degree in architectural served as director and trustee ✓ $15 million to $75 million engineering from Penn State University of organizations including the ✓ Greater than $75 million and his MBA in entrepreneurship and Tahoe Maritime Museum, the economic business strategy from DePaul Tahoe Yacht Club Foundation, University. the Ironworkers International Apprentice Trust, the Western Steel Council, Orinda community fundraising ➤ Jacob schueller, a senior in the civil engineering program committees and the San Leandro Vocational Education at Marquette University, has been interested in structural Committee. He holds a B.S. degree in business engineering since early childhood. Now specializing in administration from California Polytechnic University structures, one of his primary focuses at Marquette has in San Luis Obispo. been Engineers Without Borders. He has made three trips to Guatemala with the program, most recently to ➤ Charles C. Porter is principal and cofounder of construct a 270-ft suspension bridge. This past year, Development Management Associates, LLC, Chicago, a Schueller tried his hand in research for the first time by developer and property manager of regional retail and determining the classification, rot sensitivity and strength mixed-use centers. With more than 30 years of leadership characteristics of Guatemalan lumber with Marquette experience in real estate development and construction, professor Chris Foley and fellow classmate Tim Lewis. Porter has played a primary development role, working as an owner and on behalf of client owners, for several ➤ Mark simonides joined Turner’s Chicago business properties, including the 900 N. Michigan Ave mixed-use unit in 1982, where he has served as project engineer, project, the Houston Galleria expansion and renovation, superintendent, project manager and project executive on the Tabor Center redevelopment in Denver and expansion several of Chicago’s premier projects. He currently serves as work at the Old Orchard Center in Skokie, Ill. He holds a vice president and operations manager for Turner’s Great Bachelor’s degree in architecture from the Illinois Institute Lakes Region. In this role, he oversees the operations for of Technology and is a member of the International Council the Illinois, Indiana, Michigan and Toronto offices and is of Shopping Centers (ICSC), the Council on Tall Buildings responsible for the oversight and management of the and Urban Habitat (CTBUH), the Urban Land Institute (ULI) region’s 300 professional personnel. may 2013 MODERN STEEL CONSTRUCTION National Award—Greater than $75 Million nAsCAr hALL Of fAMe, ChArLOTTe, n.C. “Totally bewitching, it grabs hold of your senses long before you find the words to articulate what it has accomplished.” —Paul Dannels The challenge of designing a Hall of Fame for NAS- are analogous to the blur of a car racing past the spectator CAR? Capturing the essential spirit of NASCAR at tremendous speed. Within the Great Hall, a signature el- racing in architectural form. In exploring the pos- ement of a curved, banked ramp leads the visitor from the sibilities for expressing speed and spectacle, the archi- main floor to exhibit levels above. The ramp contains a dis- tect and structural engineer were drawn to the arena of play of race cars frozen in a moment from a race, capturing action, the racecourse, where fans and race teams come in another way the speed and spectacle that is the essence together each race week for the experience of race day. of the sport. Curving, sloped forms are evocative not only of the dy- The selection of material for the Ribbon was critical to namic and changing sinuous shape of the racetrack but realizing the design intent. The team drew on another as- also the perception of speed, which, of course, is at the pect of the world of NASCAR—its technology—and was heart of any race. inspired by the process of shaping raw sheet metal to form The expression of these forms could only have been the body of the race car. This fundamental element has achieved through the use of steel, both as cladding and underlain all NASCAR race cars since the beginning of the structure, encompassing several long-span and architectur- sport. From a design point of view, metal imparts a light ally exposed structural steel (AESS) elements and employ- and airy feeling to the architecture. As the cladding ma- ing innovative approaches to connections, detailing and the terial the stainless steel softly reflects light and accentu- interface of structural steel with stone, glass and steel as a ates the dynamic aspect of the Ribbon as its sculpted form finish material. changes around the building. The Hall of Fame consists of four basic elements: Technically, there are tremendous benefits to the use of ➤ A large glazed oval shape forming a Great Hall serves as steel. Its lightness as a cladding element allows structural the symbolic core of the Hall of Fame support to be minimized and makes it possible to achieve ➤ A rectangular volume houses visitor services, including the great span over the main entry. The lightweight sub- entry and exhibit space on upper floors panels are easily assembled into unique shapes following ➤ A Hall of Honor is situated as an iconic element within the computer-generated geometry, and the shingled applica- Great Hall tion of the finished stainless skin panels are a natural solu- ➤ A broadcast studio enlivens the Hall of Fame Plaza, the tion to the complex problem of installing a durable finish on sweeping forecourt that welcomes visitors a curvilinear, warped surface. Design explorations of speed and spectacle evolved The Ribbon takes the form of a mobius, a continuous into an architectural element, the Ribbon that envelops the closed surface with only one side, formed from a rectan- full-block building in a form that speaks to the imagery and gular strip by rotating one end 180° and joining it with the spirit of NASCAR. Beginning as a curved, sloping exterior other end. The Ribbon is constructed using 165 prefabricat- wall enclosing the building, the Ribbon twists in a free span ed sub-panels and more than 5,000 stainless steel skin pan- over the main entry to form a welcoming canopy. Long, thin els. At the twisting canopy over the main entry, the Ribbon incisions in the metal skin, which are animated by running free-spans 158 ft and weighs 157 tons, with a 4-ft-diameter, lights in colors that represent those of recent race winners, 1½-in.-thick internal support pipe with W-shape cantilevers MODERN STEEL CONSTRUCTION may 2013 serving as its backbone. At the ends of the twisting free- packages to enable detailing and fabrication of portions of span, significant reactions result from the action of gravity, the project to proceed before the full design was complete. wind, snow, ice and temperature. At one end the Ribbon A 3D Tekla model was used in the steel detailing to identify is anchored to the braced frame at the perimeter of the and resolve potential conflicts in the field. These efforts and Great Hall. At the other it is anchored to a concrete shear effective team communication allowed the long scheduled wall through a large embedded plate with closely spaced public opening to occur on time. deformed bar anchors and shear studs. At the top half of Owner/Developer the embed plate, four 13∕8-in. Dywidag post-tensioned re- City of Charlotte; NASCAR Hall of Fame, Charlotte, N.C. bars provide a clamping force between the embed plate Owner’s representative and the concrete wall. Developing the underlying structure, NASCAR, Charlotte coordinating it with the primary structure of the building and resolving issues of deflection, thermal expansion and Architects construction tolerance were achieved through an intensive Pei Cobb Freed & Partners LLP, New York design and engineering process that used the latest in BIM Little Diversified Architectural Consulting, Charlotte technology. Close coordination among the architect, struc- structural engineer tural engineering team and design-build contractor of the Leslie E. Robertson Associates, RLLP, New York Ribbon was critical to success. The result is a unique iconic general Contractor form, emblematic of the sport it celebrates, and the defining BE&K Building Group, Charlotte, N.C. symbol of the facility. The structure’s significant spans were achieved with Design-Build Contractor for ribbon structural steel trusses: Zahner, Kansas City, Mo. ➤ A set of trusses spanning 175 ft achieve a grand column- steel fabricator and Bender/roller free ballroom SteelFab, Inc., Charlotte (AISC Member/AISC Certified ➤ A 100-ft-long, bi-level footbridge, supported by a pair Fabricator) of one-story-deep trusses, links the ballroom with the steel Detailer existing Charlotte Convention Center Hutchins & Associates, Clemmons, N.C. (AISC Member) ➤ Two- and three-story-high trusses cantilever 30 ft over the steel erector broadcast studio. Williams Erection Company, Smyrna, Ga. (AISC Member/ One of the most significant AESS elements in the proj- AISC Advanced Certified Erector) ect is the Vierendeel frame supporting the glass façade of the Great Hall. The lateral-load-resisting system at this Photographs façade also functions as the braced frame that supports Paul Warchol Photography, Inc. the Ribbon. The structural bid set was issued six months before the 100% CD set. The steel tender was divided into multiple MAY 2013 MODern sTeeL COnsTruCTiOn Merit Award—Greater than $75 Million BArCLAys CenTer, BrOOkLyn, n.y. “This is the kind of bold design that becomes an instant landmark.” —Chris Olson MODern sTeeL COnsTruCTiOn MAY 2013 The new 675,000-sq.-ft Barclays Cen- Flatbush trusses. Three planar trusses ter, home of the NBA’s Brooklyn Nets, frame out an inner “oculus” in the center seats 18,103 and will host more than of the canopy. Supplemental steel is 200 sporting and cultural events annually provided within the oculus and at the (seating capacity increases to 19,000 for perimeter to support the latticework concerts). It features 95 luxury suites, four façade. Additional supplemental steel party suites, two conference suites, four hangs below the truss structure to bars/lounges, four clubs, a restaurant and create the supplemental framework to several street-level retail stores. support the “pouch.” The structural The arena is in a tight urban setting engineer, Thornton Tomasetti, provided near a subway station and train terminal, Tekla models, connection samples and presenting unique challenges for the foun- full connection design, which allowed dation system. The building was designed the team to produce models quickly, with a pair of truck elevators feeding a be- store large quantities of information low-grade loading dock with a large truck and coordinate with the entire team. turntable to facilitate turning. Columns in Even from its initial design, the project this region were transferred using large constantly pushed the limits of BIM plate girders spanning over the dock. and educated staff about the use of The dominant feature of the arena is several different programs and ways the weathering steel lattice that wraps to link and automate processes. The the structure. Rows of steel panels en- complex geometry of the façade and velop the exterior, including an entrance the shortened schedule meant that the canopy that cantilevers 85 ft over the team needed to coordinate in a 3D plaza. The façade design, with 12,000 environment and provide the information pre-weathered steel panels, and the can- to the contractor in this format as well. opy were added a month after the GMP Thornton Tomasetti’s team consisted package was released and two months of staff members across multiple offic- before the first steel mill order was due, es and practice areas. Teams in Kansas requiring the team to develop the façade City and New York designed the roof design while keeping pace with the origi- and bowl and then these two compo- nal schedule. Nearly 1,000 tons of steel nents had to be integrated. Construc- were added to support the façade, which tion support services teams worked on also became a prominent design feature. the Tekla models, model delivery and Another major structural feature, connection design; erection engineer- the distinctive arched roof, spans more ing was performed in the Chicago of- than 380 ft and is supported by a pair fice. The firm maintained staff on-site of 350-ft tied arch trusses spanning the full-time to accommodate changes and long direction of the arena. The roof sys- oversee work, and weekly coordination tem geometry was further complicated meetings helped to identify issues ear- by the additional loads imposed by the ly on and develop solutions proactively. outer façade system. As such, the build- Owner/Developer ing lateral system and diaphragms were Forest City Ratner Companies, Brooklyn, designed to resist thrust forces from the N.Y. roof arches, which were minimized by use of the tension tie. Architects The primary load-carrying members AECOM, Kansas City, Mo. of the canopy are a pair of box trusses SHoP Architects, New York cantilevering 85 ft beyond the column structural engineer supports along the Atlantic Avenue face Thornton Tomasetti, New York to the north and the Flatbush Avenue face to the southwest. Each box truss general Contractor consists of a pair of planar trusses Hunt-Bovis joint venture, Indianapolis ranging from 8 ft to 12 ft deep and laced steel fabricator together with horizontal bracing. The Banker Steel Company, Lynchburg, Va. planar trusses have W14 chords turned (AISC Member/AISC Certified Fabricator) web-horizontal to maximize out-of-plane stiffness with W14 braces and verticals steel Detailer shop welded to the chords. Field splices WSP Mountain Enterprises, Inc., between trusses consist of bolted flange Sharpsburg, Md. (AISC Member) plate connections. Another box truss Photographs spans at the leading edge of the canopy Bess Adler between the tips of the Atlantic and may 2013 MODERN STEEL CONSTRUCTION Merit Award—Greater than $75 Million nATiOnAL geOsPATiAL-inTeLLigenCe AgenCy, sPringfieLD, VA. Situated on the outskirts of the Capital Beltway To fill the central atrium and interior of the building with adjacent to the Accotink Creek stands the National light, the west end wall of the atrium was glazed with a curtain Geospatial-Intelligence Agency’s (NGA) 2.4 million- wall system and the roof of the atrium was covered with a sq.-ft campus, known as New Campus East (NCE). The transparent fabric membrane. The west end atrium wall facility was not only designed to enhance the agency’s consists of a 135-ft-tall by 140-ft-wide curtain wall backed capabilities as one of the leading intelligence organizations by a round HSS steel space frame. AESS requirements were in the world, but also to achieve a unifying, cultural incorporated into the design, fabrication and erection of the transformation. This effort is expressed in the design of the space frame structure, which served several functions. In nine-story main office building. Composed of two curved addition to supporting the gravity loads of the curtain wall, 900-ft-long overlapping bars around a 500-ft-long central it supports atrium roof gravity and wind loads and meets all atrium and elliptical auditorium, the building’s overall form mandated ATFP criteria. It also acts as a pedestrian bridge is in the shape of a lens—a fitting metaphor for NGA, at several levels, providing access and circulation between which serves as the nation’s eyes, the primary source of the towers. geospatial intelligence for the purposes of U.S. national The atrium roof is more than 500 ft long, with an area security, defense and disaster relief. of 45,000 sq. ft, and consists of AESS arched HSS mem- This defining architectural expression was accomplished bers supporting an air-filled ethylene tetrafluoroethylene primarily due to the benefits of structural steel. Steel facili- (ETFE) fabric roof. Although it appears clear, the custom tated the large bay size needed for program flexibility of silkscreen pattern and air-filled ETFE system provide signifi- the typical office; reinforced the architectural concept and cant daylight while minimizing solar gain. Being extremely imagery expressed in the transparent atrium roof, west end lightweight minimized ATFP-related effects and aided in re- wall and exterior V-columns; and accommodated the con- ducing the tube structure size and tonnage; 18-in. by 12-in. straints of the highly complex technical Anti-Terrorism Force built-up HSS was used for the arched roof members, which Protection (ATFP) criteria as well as a demanding schedule. vary in span along the tapered atrium, with a maximum span Managed by the U.S. Army Corps of Engineers – Balti- of 125 ft and a 75-ft rolled radius. The roof arches span be- more District, the project has its origins in the 2005 Base tween the office towers and were designed as “springs” to Realignment and Closure Act (BRAC). RTKL Associates, accommodate independent movement of the two wings un- Inc., and KlingStubbins formed a joint venture to provide der lateral and thermal loads. design services, including master planning and full archi- The two 900-ft wings are configured to focus on the cen- tecture, engineering, interiors, site/civil, landscape and tral atrium. This dramatic space and the atrium’s light-filled technology design. amenities create a “Main Street” for the office building com- At 2.2 million sq. ft, the nine-story main office build- munity. Enhancing this effect are the west end atrium wall ing is the second largest single-occupancy building in the and the atrium roof structure. world (after the Pentagon) and the largest federal building The unique exterior design of the main office building in the world to achieve LEED Gold certification from the U.S. was achieved as a coordinated partnership between the Green Building Council. MODern sTeeL COnsTruCTiOn MAY 2013 Merit Award—Greater than $75 Million nATiOnAL geOsPATiAL-inTeLLigenCe AgenCy, sPringfieLD, VA. “ The various bridges are an eye-catching aspect of the structure and add convenience and function to the vast space.” —Jacob Schueller architect and structural engineer. Signature V-columns spaced at 40 ft on center are featured along the first- and second-floor perimeter, providing a separation between the visually solid base and the triangulated precast façade of the upper six floors, while also continuing the diagonals of the upper façade. In addition to providing a strong aesthetic statement, the V-columns participate in the lateral load resisting system and accommodate alternate load path/progressive collapse design. Removal of any V-column leads to loads above being shared between transfer girders at the fourth floor and roof levels. Owner/Developer National Geospatial-Intelligence Agency, Springfield, Va. Owner’s representative U.S. Army Corps of Engineers – Baltimore District, Fort Belvoir, Va. Architect and structural engineer RTKL/KlingStubbins joint venture, Baltimore general Contractor Clark/Balfour Beatty joint venture, Bethesda, Md. steel fabricator and Detailer SteelFab, Inc., Charlotte, N.C. (AISC Member/AISC Certified Fabricator) Consultant Hinman Consulting Engineers, San Francisco Photographs James West, J West Productions Paul Warchol Photogaphy, Inc. David Whitcomb (RTKL) MAY 2013 MODern sTeeL COnsTruCTiOn National Award—$15 Million to $75 Million CiTy Creek CenTer reTrACTABLe rOOf, sALT LAke CiTy, uTAh “Having a roof spanning two city blocks that can be transparent and open and close is amazing.” —Charles C. Porter Beginning in 2003, the Church of Jesus Christ of Latter- pairs of glass-covered, arching panels that cantilever 33 ft day Saints developed plans to transform two Salt Lake from the adjacent structures over the retail concourse. When City “mega-blocks” just south of the town’s Temple closed, all six panels seal together and create an air- and Square into a 5.5 million-sq.-ft, mixed-use development water-tight barrier. To open, the panels part in the middle and featuring retail, residential, office and parking space. The retract onto the building structure as the panels bow down out centerpiece would be a man-made replica of the area’s of sight from below. Key to the bowing action are innovative historically significant City Creek that would meander for whalebone-shaped ribs that support the glass roof. Each roof two blocks and be surrounded by walkways and a six-acre panel is comprised of three parallel whalebones made of public park. Developers wanted an urban, open-air setting curved and tapered welded steel box girders that run from but also needed the assurance that retail businesses would the tip of each panel’s arch to the end of its backspan. The be protected during inclement weather. After studying glazed portion of the three whalebone arches are joined by many skylight possibilities, structural engineer Magnusson four purlins made of 8-in. A106 Grade B pipe and one purlin Klemencic Associates (MKA) produced a retractable roof of HSS10¾×½-in. ASTM A500 Grade B tube. concept that would fully meet the developer’s needs. Uni- The purlins are designed with concealed connections Systems was selected as the design-build contractor, with that are invisible from below and provide attachment points MKA as their structural engineering sub-consultant, and for 6-ft, 4-in.-sq. panes of glass. A typical roof panel is Ducworks as the steel fabricator. The resulting retractable, glazed with 72 panes of glass, each weighing approximately barrel-vaulted roof is configured in two sections, each 300 lb, although the size of each panel varies because of the spanning one city block. roof’s curvature. The three whalebone backspans are con- Each section is 240 ft long and 58 ft wide, with an S- nected with rectangular HSS ASTM A500 Grade B tubing in shape that echoes the curve of the signature creek below. a K-brace configuration to provide shear stiffness between The precision-sculpted steel and glass transparently shields them. In order to meet special finish and detailing require- patrons when closed and disappears from sight when open, ments, the side and bottom whalebone girder walls were connecting nature with the areas below. ground and filled to produce perfectly flat plane surfaces, For each block, the retractable roof is comprised of three and a Tnemec Fluoronar paint system gives the whalebones MODERN STEEL CONSTRUCTION may 2013 and purlins a high-quality metallic finish. The whalebones 8 ft per minute and opens or closes in approximately six were built at Ducworks’ fabrication facility in two sections us- minutes. Each panel has a unique operating sequence to ing custom-designed fixtures and joined with a plate-weld- prevent the panels from interfering with one another as ed connection to accommodate the unique geometry. The the seals engage and disengage. Because the S-shaped pre-assembled rail girders and whalebones were hoisted curve of the roof causes the three panels on one side to onto the roof, and the panels were assembled in place. converge when opening, the center panel on that side Each 10½-ton whalebone is supported by a 27-in. dou- remains in the raised position when opening, rather than ble-flanged steel wheel located at the bottom of the arch bowing down, to prevent collisions. The roof’s curvature, and two guide rollers located at the end of the backspan. along with the complex seals and intersecting panels, The wheel follows one geometric path on top of the rail made the control system the most complicated ever de- girder, and the guide rollers ride an inclined track along the veloped by Uni-Systems. bottom of the rail girder. As the guide rollers travel up the Owner incline, the roof’s cantilevered front edge dips down, caus- City Creek Reserve, Salt Lake City ing the roof to bow down, with the wheel as the vertical rotation point. The guide roller track surface is a heat-treat- Architect ed, hardened plate welded to the A572 Grade 50 steel rail Hobbs + Black Architects, Ann Arbor, Mich. girder. A custom welding procedure was developed to join structural engineer the two elements to avoid damaging the hardened plate. Magnusson Klemencic Associates, Seattle The flanges on the center wheel closely surround the center general Contractor rail and act as wheel guides. The flanges on the two outer Jacobsen Construction, Salt Lake City wheels leave a slight gap around the rails to accommodate lateral movement between the three rails caused by con- steel fabricator struction tolerances and structural and thermal movement. Ducworks, Inc., Logan, Utah (AISC Member/AISC Certified Locking pins mounted to the whalebones automatically Fabricator) engage the rail girders when the panels reach the open or steel erector and Mechanization Consultant closed end of travel. With the pins engaged, the roof pan- Uni-Systems, Minneapolis (AISC Member) els can accommodate differential movement from potential seismic activity. Photographs An industrial computer located in a remote control Michael Dickter, Magnusson Klemencic Associates room operates the retractable roof, which travels up to Uni-Systems may 2013 MODERN STEEL CONSTRUCTION