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G. Charles Naeve, P.E., Richard A. Martin, P.E.and Brian Johnson

An of exposed structural offers an impressive welcome to visitors to the convention center in Austin, TX.

Modern Steel Construction • May 2003 n 1998, The City of Austin ap- proved bonds for expansion of the existing city Convention Center. The original , completed in 1992 and designed by the Austin ICollaborative Venture, had been suc- cessful in luring convention business and visitors to Austin, and an expan- sion was warranted. The Austin Col- laborative Venture, led by Page Southerland Page (PSP) Architects with Lawrence W. Speck, FAIA, was chosen to double the size of the facility with a 400,000-sq.-ft addition on a plot of land about half the size of the origi- nal building. The restricted site led to a vertical solution, with meeting and a 45,000-sq.-ft placed above a 125,000-sq.-ft, -free exhibition . The exhibition space is contiguous with the existing and bordered on the west and north with circulation and pre-function space. The northwest cor- ner punctuates this circulation with a new entrance facing north toward Austin’s central business district. The entrance takes the form of a glass pavil- ion with an exposed structural steel framework, a shingled glass façade, and a west-facing skeletal screen-. The approximately $80-million con- vention center expansion, completed in May 2002, is largely a structural steel building. More than 4500 tons of struc- tural steel were used in the building, including 400 tons of grade 65 trusses. The program for column-free exhibi- tion halls led to a clear-span structure. Nineteen-ft-deep trusses spaced at 30’ on center span 210’ between Within the glass pavilion, the escalators run to an intermediate landing adjoining a can- on the north side. A 65’-deep super- tilevered . truss with a span of 270’ is placed on the south side. This strategy, when coupled with the existing exhibit halls, provides an ion . Here the structural steel is only by an entry and a glass- L-shaped, clear-span space of about showcased as a part of the building’s balcony extension. As the after- 165,000 sq. ft. The floor trusses, sup- architecture, adding order and material noon sun begins to illuminate the porting the ballroom above, hover im- context to the architectural palette. screen-wall, shards of blue light move pressively in the of the exhibit Painted steel fins frame the shingled through the interior of the pavilion, halls; but only the lower third of the panes of blue-green glass, and slender changing with the sun’s daily and super-truss gives any evidence of the box columns stand free adjacent to the yearly movement, extending the visual work being performed. The upper two glass skin. The columns reach for an or- depth of the art wall to include the di- thirds of the truss are concealed within dered roof of tree-like struts braced mension of time. and ceiling space, extending to with stainless cables and machined Within the glass pavilion, an escala- the high roof of the ballroom. stainless fittings. A west-facing art-wall tor runs free of enclosure to an inter- stands free of the pavilion, shading the mediate landing adjoining a SHOWCASE STRUCTURE enclosed space with a field of cobalt- cantilevered balcony, projecting The substantial structure of the blue glass panels overlain by a grid of through the west façade, at 22’ above main building is contrasted with the el- photovoltaic fins. The art wall extends the hall floor. The escalator then turns egance and lightness of the glass pavil- to a height of 96’ and is interrupted 340 degrees in plan to reach for the

May 2003 • Modern Steel Construction The 65’-deep super-truss spans 270’.

The exterior “art wall” uses panes of cobalt- blue glass supported by structural steel struts to filter into the atrium.

ballroom pre-function area, 31’ above vide a primary building entrance. Ar- STRUCTURAL TREES the landing. The escalator ride is an chitecturally, the pavilion was to pro- The structural concepts for the event for convention-goers, with spec- vide a sense of arrival and inspiration atrium were a direct response to the ar- tacular views of the city skyline to the to the convention attendee. The vision chitectural desire to provide a minimal, north and glimpses of the hill-country for the space was one of a large shin- three-dimensional framework compli- to the west. At night, the space be- gled glass box, 90’-tall by 62’-wide by mentary to the shingled glass façade. In comes a lantern for the convention cen- 140’-long. order to keep the members as small as ter area, with a pale-green-lighted In order to realize this vision, Speck possible, a strat- ceiling plane illuminating the entire and Project Architect Brett Rhode, AIA, egy was developed to gain as much pavilion. collaborated with Matt King of Ove continuity as possible at the floor and Arup and Partners on structural frame roof attachments. This strategy was ac- ARCHITECTURAL GOALS concepts, and with James Carpenter, of complished by essentially cantilevering The pavilion was designed to be a James Carpenter Design Associates, on up from the with exposed celebratory space and the focus of the artistic design of the west facing art concrete fin columns, 16”-wide by 4”- addition. In the early phases of design, wall. Davidson Norris of Carpenter deep, and cantilevering down from the architect Lawrence Speck identified the Norris Consulting provided day-light- roof structure with an inverted pyra- pavilion as an area with many goals. ing and glass selection expertise. Archi- mid consisting of four, 3”-diameter Functionally it had to serve as the con- tectural Engineers Collaborative, the solid bars. vention registration area, provide verti- project structural engineer, was en- A central thin box column, 6”-wide cal circulation to the ballroom above, listed to work with the team in a col- by 30”-deep, spans vertically between facilitate perimeter circulation to ex- laborative design effort, and to execute the concrete base and the column tree hibit halls and meeting rooms, and pro- the construction documents. for a height of 60’. The box columns

Modern Steel Construction • May 2003 Section looking east. Trusses 19’ deep spaced at 30’ on center span 210’ between columns on the north side. A 65’-deep super-truss with a span of 270’ is placed on the south side. stand free of the glass wall, punctuated ture was extended beyond the tree on 12’ centers by 2”-diameter solid columns to capture tee-shaped hangers struts and paired with ½”-diameter at 10’ on center. The glass façade, fabri- stainless cables. At corners, the con- cated and installed by WinCon, con- crete fins and steel box columns be- sists of shingled panes of insulated come cruciform in shape, adding glass. The glass slopes within the 18” stiffness to the pavilion structure. depth of the tee, with the tee stems pro- A parallel benefit of the three-part jecting beyond the façade as elegant ex- structure (concrete base, column link terior fins. Between the tees, on 12’ and column tree) is that the construc- vertical centers, frame horizontal steel tion satisfied the building-code fire HSS, 8”-wide by 4”-tall. The HSS sup- protection requirements for the space. port two slanted 5’-by-12’ panels. Glass The “atrium occupancy” called for a panels are 1”-thick, low-E insulated two-hour fire-resistance rating to the glass, imprinted with a frit to 18’ height and a one-hour construction improve thermal efficiency and reduce between 18’ and 25’. Above 25’, the glare. Panels are surface mounted to construction could be unprotected. The conventional aluminum frames with An interior view of the completed exhibition two-hour fire-resistive requirement glazing between individual pieces of hall. was satisfied by the concrete columns, glass. and the one-hour construction was The horizontal HSS framing also provided by an intumescent coating on performs the structural function of the steel. Above the 25’ height to the transferring wind loading to the box space to block the trajectory of the af- top of the atrium at about 90’, the struc- columns through triangulated, paired ternoon sun. Blue glass lies in the plane ture simply was painted, allowing the strut-and-cable assemblies. These as- of the wall while glass photovoltaic steel shapes to be exposed in their true semblies enable bracing of the thin box panels project to collect energy from form and shape without restrictive columns by restricting column rotation the afternoon sun. coatings. and lateral displacement. The bracing The framework meets strength and makes it possible for the columns to be ATRIUM CONSTRUCTION serviceability requirements of the very thin, 6” wide, for their 60’ height. AISC-member Beck Steel prepared building code by carrying gravity loads shop drawings for the atrium structure within its three-dimensional shape, by ART WALL STRUCTURE in a three-dimensional format, locating resisting local lateral loads internally The art wall structure was con- every bolt and pin in the entire struc- and by transferring global lateral loads ceived as a mirror image of the pavilion ture within one three-dimensional file. into the adjacent main building frame. column structure. Paired struts and ca- Individual members were extracted bles are mirrored about the horizontal from the file and further delineated as GLASS WALL FRAMING support tube. The exterior- pieces in the traditional manner. This Early discussions on the glazing wall box columns, reduced in depth to process and the resulting fabrication system centered on the advantages of a 24”, support a horizontal grid of steel produced a structure that was easy to hanging façade with members loaded HSS, 6”-wide by 4”-tall, at 12’ on cen- erect in spite of its complicated geome- primarily in tension. Glass panes and ter. One-inch-diameter sag rods tie the try and numerous pieces. framework could be minimized if not HSS together and become the armature subject to compressive stress and the for attachment of the photovoltaic pan- A YEAR LATER potential for compressive buckling. In els. The columns and wall cantilever The Austin Convention Center Ex- order to hang the façade, the roof struc- beyond the height of the adjacent roof pansion is now approaching one year

May 2003 • Modern Steel Construction of occupancy. For those involved in STRUCTURAL ENGINEER the design, there is still the pleasant Architectural Engineers Collaborative, surprise of watching the convention Austin, TX attendees as they enjoy the atrium PAVILION STRUCTURE space, look through the glass to our CONCEPT city beyond, rush to a meeting , Ove Arup and Partners, New York, NY or stop to greet a colleague. At con- vention time, the space has the feeling PAVILION ART-WALL DESIGN of an active public square, and the James Carpenter Associates, New structure joins the architectural palette York, NY as a comforting backdrop to the vi- PAVILION DAYLIGHTING brant activity. ★ CONSULTANT Carpenter Norris Associates, New G. Charles Naeve, P.E. is a principal at York, NY Architectural Engineers Collaborative, P.L.L.C., Austin, TX, and was principal in STEEL FABRICATOR–BUILDING charge of the convention center expansion. Cives Steel Company, Rosedale, MI Richard A. Martin, P.E. is an associate (AISC member) principal at Architectural Engineers Col- STEEL ERECTOR–BUILDING laborative and was project engineer for the Peterson Beckner Industries, Houston, expansion. Bryan E. Johnson is a graduate TX (AISC member, SEAA member) engineer at Architectural Engineers Col- STEEL FABRICATOR–PAVILION laborative. Beck Steel, Inc., Lubbock, TX (AISC member) OWNER GENERAL CONTRACTOR City of Austin Convention and Visitors SpawGlass Contractors, Inc., Austin, TX Bureau, Austin, TX PROGRAM MANAGER ARCHITECT Gilbane Building Company, Houston, TX Page Southerland Page, Austin, TX

Modern Steel Construction • May 2003