In South Florida, where hurricane "season" occupies a full six months of the calendar, AEC industry professionals are especially attuned to the challenge of designing for high winds. Vincent J. DeSimone, chairman of DeSimone Consulting Engineers, has been there—and knows just where to look for answers. "The most useful tool that structural engineers have to determine the forces on the building skin is wind tunnel testing and the ensuing results," said DeSimone, who will deliver a talk on "Innovative Facade and Building Design Through Modern Wind Tunnel Engineering" at September's Facades+ Miami conference. During a wind tunnel test, explained DeSimone, engineers place a scale model of a building inside a tunnel, then vary the wind speed and direction to determine the pressures on the structure. Sensors detect these pressures, which are then translated into forces acting on the facade. Forces on the facade vary from low to high, he noted, and some "hot spots" on the building envelope can achieve local forces in excess of 200 pounds per square foot. The load for the structure as a whole are generally determined by average these minimum and maximum forces. Per the applicable building codes, Miami-area structural engineers base the wind forces used in wind tunnel strength tests on maximum wind forces for a 50 year wind cycle. Building movement is another matter, said DeSimone. For architects and builders in Miami, the allowable lateral displacement—the height of the floor divided by 360—is determined using a 25 year wind cycle. In a building with a story height of 12 feet, in other words, the allowable movement is 0.4 inches. "In seismic zones where movement is expected to be much higher during a seismic event, facades are allowed to be much more flexible," observed DeSimone. "Knowing that facades do not determine the allowable movement of a structure, doesn't it stand to reason that here in Miami we are designing buildings much stiffer than they need to be?" Recalculating allowable movement according to a 10 year wind cycle, for instance, could reduce the building's shear walls by 22 percent. "This reduction—which, by the way, is used all over the country—results in a true sustainable reduction in material," he said. "Remember, the most sustainable building is the building you don't build and, conversely, the building which uses the least material." Learn more from DeSimone and other experts in high performance envelope design and fabrication at Facades+ Miami September 10–11.
Posts tagged with "Structural Engineering":
Austin’s Circuit of the Americas gets an iconic observation tower using 350 tons of steel.The Circuit of the Americas (COTA) in Austin, Texas, will host the United States Grand Prix from 2012 to 2021. While German Formula 1 specialist Hermann Tilke designed the racecourse and technical facilities, COTA’s owners hired local firm Miró Rivera Architects to turn out a main grandstand and amenities for the 9,000 fans expected to attend the races. In addition to imbuing the project with a variety of programmatic functions that go beyond racing, Miró Rivera created a sleek observation tower that gives spectators unrestricted views across the racetrack’s twisting expanse. “Our idea for the tower was to be able to go way up and see the track from one focal point in a structure that was an iconographic symbol for the track,” said Miguel Rivera, founder and principal of the architecture firm. “Our inspiration came from Formula 1 cars, where speed and efficiency are so important.” Just like the track’s feature attractions, the tower’s design didn’t feature any excesses. Structural engineers at Walter P Moore helped ensure every piece of steel did some kind of work so the tower was as efficient as possible. Working with the architects’ 2D drawings, the structural engineering team developed a three dimensional tower with all the requisite details for construction—right down to bolts and welding points—in Tekla Structures. “Everything that goes into fabrication is digitally defined in this program,” said Mark Waggoner, principal with Walter P Moore. “Generally, in our business, we deliver paper drawings for the steel fabricator to interpret and build, but we were able to bypass this step and print shop drawings directly from our model.” To increase efficacy, the engineers wrote some of their own connections for programming interfaces with steel fabricator Patriot Erectors. Waggoner also located the joints, especially for the veil, (the tubular red feature, inspired by the tracers of a car’s tail lights in the dark) in Tekla. To reduce the cost of bending each 8-inch steel tube to the architect’s initial drawings, the program helped break large radii into segmented, straight lines to achieve time and cost savings. To facilitate shipment to the COTA track, the 20- by 20- by 250-foot structure was broken into four pieces that could be stitched back together on site. Patriot Erectors welded 10- by 10- by 30-foot sections in their Dripping Springs, Texas-facility that were assembled on three different casting beds and craned into position. Reflecting on the 11-month digital design/build schedule, Waggoner said the process for the COTA Observation Tower was somewhat unconventional. “People generally like to have paper drawings for these types of projects,” he explained. “But at the end of the day, the general contractor felt this process saved us about three months of time.”
For thousands of years, it has been widely acknowledged that glass is not only a compelling material, but is unbreakable in compression. More recently, glass as an innovative facade technology has steadily surfaced, propelled mainly by prominent international building designers pursuing transparency in building facades. At The Architects Forum Glass+Performance on September 11 at the GlassBuild America expo in Atlanta, Michael Ludvik of M. Ludvik Engineering will present about structural glass in a session titled Structural Glass: Ancient Material Modern Treatment. To explore glass as an appealing facade material, Ludvik will provide project examples including the TKTS Booth at Times Square, the Canopies at the Lincoln Center, and the Sky Dive Dubai wind tunnels. The work is characterized by an architecturally sensitive first principles approach. Ludvik is a structural engineer who gives particular attention to structural glass. Since graduating from the University of Sydney with a BE in Civil Engineering, he has worked as an engineer at notable firms such as Arup, Hardesty & Hanover, and Dewhurst Macfarlane & Partners. His Brooklyn-based firm M. Ludvik & Co. offers structural, glass, and facade engineering services for both architects and contractors. Register here to hear Ludvik speak about structural glass at Glass+Performance on September 11, 2013!
|Brought to you with support from:|
A fellow at the Knowlton School of Architecture expounds on the work of Le Ricolais with a new plugin for Rhino.For Justin Diles, Ohio State University’s KSA LeFevre fellowship was a fateful progression of past experiences and ongoing professional work. While studying under Cecil Balmond at the University of Pennsylvania, Diles encountered hand-built models that Robert Le Ricolais constructed with his students in the 1960s. “Le Ricolais built models with his students for 20 years,” said Diles, “and one that I found he had built out of tubular steel and loaded to failure. It produced a really beautiful deformation pattern.” Two years later, Diles was teaching at the University of Applied Arts Vienna in the master class studio of Greg Lynn. While in Austria, he met Clemens Preisinger, a developer who, with support from Klaus Bollinger’s firm Bollinger Grohman Engineers, wrote a new plugin for Rhino called Karamba. The plugin is an architect-friendly, finite, element analysis method that delivers fast, intuitive graphic information, along with the requisite numbers. The plugin would figure heavily in Diles’ fellowship work. When he arrived in Ohio, Diles’s work progressed along two parallel tracks: The first was developing a computational design component with a formal vocabulary of the structural deformation Le Ricolais’ model. The second was developing a material capable of realizing the design. In Karamba, Diles augmented a tectonic simile from le Ricolais’s latticed models as surfaces for fabrication with composites. “That was an ah-ha moment for me,” said Diles. “I began taking a single assembly and ran it through multiple iterations of buckling deformations.” Diles layered multiple deformations into patterns that produced a puzzle of nesting components. Black and white coloring helped him track the layers and lent a graphic, architectural appeal. After the design was finalized, Diles made a series of molds from lightweight Styrofoam. “It was interesting because it’s usually a junk material and, in a way, has a very bad reputation as a material,” he said. “But it’s recyclable and can hold a tremendous amount of weight and is easily worked on a CNC mill.” A 3-axis mill generated components of a mold, which were taped together and sealed with Plaster of Paris to prevent resins of the composite from bonding to the foam. “We used a lot of tricks from Bill Kreysler’s fabrication shop,” said Diles. The final mold was sealed with Duratec StyroSheild. Diles and his team coated the mold with layers of different materials, not knowing exactly how the final components would safely release from the cast. An outermost layer of marine-grade gel coat was applied to the mold and roughly sanded so a chopped E-glass fiberglass reinforcement could be affixed to it with resin. Since fiberglass is a lightweight material, about three layers were built up to realize the final 11 1/2- by 6-foot form. Convex white sections and hollow black pieces were friction-fitted, sans glue, with maximum gap spaces of only 1/32-inch.
For most architecture students, a model malfunction won't land you in the middle of a river, but one group of Buffalonian risk takers at the University of Buffalo School of Architecture and Planning, under the direction of Associate Professor Jean La Marche were up for the challenge. Students Troy Barnes, Stephen Olson, Scott Selin, and Adrian Solecki designed and installed half of a bridge—made of cardboard—cantilevered over the Buffalo River, and invited people to step out over the water. The frightening experiment worked, challenging conventional notions of material constraints. The small structure was built from locally-produced cardboard tubes and is held up using rollers, pulleys, and ropes tied back to disused rails on the site. A supporting frame on a boat used to position the structure "lent the whole operation a nautical feel, fitting with the site," a spokesman for the team said in a statement. "With one of us on the raft, one manning the ropes, two were left to do the heavy work of pushing the cantilever out six inches at a time. After forty-five minutes, the structure dropped over the edge into place." The Buffalo Rising blog visited the installation, even venturing out onto the cardboard cantilever, and has more photos and observations.
Engineering firm Buro Happold is known for designing innovative structures. The glazed canopies it suspended above the courtyards of the Smithsonian and the British Museum baffle the mind with their seeming lightness. And the Experimental Media and Performing Arts Center at Rensselaer Polytechnic, on which the firm collaborated with fellow UK native Grimshaw, introduced upstate New York to some of the most space-age forms it has seen since Whitley Streiber's Communion. Now the firm—along with designers Hoberman Associates and Innovative Designs—has turned its expertise to the world of rock and roll with its structural design for an expanding 4,000-square-foot video screen that will accompany U2 on their current 360º tour. Made up of 888 LED panels (500,000 pixels) the screen weighs 32 tons, can expand and contract from 23 feet tall to 72 feet tall in 90 seconds, and can be assembled in 8 hours and broken down into portable pieces in 6 hours. More pics and some videos after the jump. The expanding video screen debuted on June 30th in Barcelona, Spain. It will open in America on September 12th in Chicago's Soldier Field. A video mock-up of screen produced by Stufish. The screen in action on opening night in Barcelona.