PANSTADIA & ARENA MANAGEMENT 1ST QUARTER 2018 RISING TO THE CHALLENGE Mosaic Stadium Image credit: Nic Lehoux Sports venue developments present complex and unique engineering challenges, as Bart Miller of Walter P Moore and Geoff Wilks of TRP Consulting explain to John Sheehan. rchitects and engineers of modern District in Inglewood, California, which venue below a single, clear-span roof,” Asports venues face a myriad of we believe will be the largest stadium Miller added. challenges as they look to complete roof in the world – covering more than projects on time, on budget, and which 1.2 million square feet – when it opens Globe Life Field meet the specifi c needs of their client. in 2020. Miller said work was also underway on The design of new ‘iconic’ venues with “It is an ETFE-clad, cable-supported a new retractable roof ballpark for the complex feature aspects also add to the roof over a stadium in an extremely Texas Rangers in Arlington, TX. demands faced by stadium and arena high-seismic region and very close to “That’s another very exciting project. LAX airport. It is a very high-profi le designers and builders. It’s not only a retractable roof, but and visible location for a spectacular The rise of multi-purpose venues and also has some ETFE elements as well project; the type of project that has to create a more open feel and bring the requirement to be able to convert never been done before.” them quickly from sporting venues to natural light inside the stadium. There host concerts and other events also Miller said Walter P Moore is the are all the challenges you have in a heightens challenges. structural engineer-of-record for ballpark – including long cantilevers the entire building, working alongside and very little symmetry or repetition Bart Miller, Principal/Structures at architects HKS. – combined with all the challenges of a Walter P Moore, told PS&AM that the retractable roof. company is currently working on a The companies have teamed up on a number of projects including number of high-profi le projects, each AT&T “With any retractable roof, the Stadium in Arlington, TX, Lucas Oil with a unique set of challenges. main challenges from a structural Stadium in Indianapolis and the new design standpoint have to do with He said: “The real speciality and value Globe Life Field for the Texas Rangers, the interaction of the structure and we bring on a lot of these projects is also currently under construction in the mechanisation, as well as the our experience with long-span, and Arlington, TX. delicate balance between the stiffness particularly lightweight, structures and “Los Angeles Sports and Entertainment and fl exibility of the rails and the retractable roofs. District is being designed with multiple moving panels that ensure that the “Right now we’re working on the new uses in mind, and will even feature a mechanisation functions properly. Los Angeles Sports and Entertainment separate, 6,000-seat entertainment Spans are typically very long and that 18 PSAM Magazine 1st quarter 2018 v10.indd 18 19/03/2018 16:52 www.psam.uk.com FEATURE Marlins Ballpark SPORTS Image credit: Christy Radecic VENUE ENGINEERING impacts our design as well, obviously, but mechanisation, in general, will drive a lot of the structural design of a roof. “What we’ve found on these projects is that the least weight solution in terms of structural steel quantities very often does not equal least cost. “You have to think about constructability, fabrication, and absolutely you have to think about the integration of the mechanisation into the structural design. Mechanisation often drives how we approach the structural design. “In addition to that, because the roof “Connected to that is also shadowing “Where we have high seismic activity, moves, theoretically there is an infinite on the field during a game. We think hurricane-prone regions, or high snow number of different positions that about shadowing caused by the density and ice loading, those things have roof could be in, so there are a lot of and positioning of cable-supported to be taken into consideration along different scenarios we need to consider, structures required to support with the functional requirements of a and the amount of analysis increases by transparent roofing materials, for stadium roof. orders of magnitude. example, impacting the ability of an “Lucas Oil Stadium from the very “The fact that these panels move outfielder to catch a fly ball.” beginning was designed to be truly creates dynamic forces, especially multi-purpose. It's not just a football when the roof panel stops abruptly Mosaic Stadium stadium that you can try to host some in an emergency stop scenario. That At the Mosaic Stadium in Regina other events in. is equivalent really to a mild seismic Canada, home of the Saskatchewan “It's a football stadium that is also event, an earthquake-type of loading Roughriders, a particular challenge designed specifically for basketball, being distributed over the entire was around the roof and the weather concerts, and conventions with full roof structure.” patterns in the area. rigging capacity, catwalk access, and Hurricane winds also need to be taken “That canopy is a PTFE fiberglass lighting capabilities that function for into consideration in cities like Miami and fabric stretched across a cantilevered any of those types of events. So truly a Houston, Miller said. structural steel frame. Beyond the multi-purpose type of facility.” “At Minute Maid Park in Houston, the complex, curving geometry, the biggest roof is designed to be closed and structural design challenges are Multi-purpose venues strapped down during a hurricane event. associated with snow and ice prevalent Miller said the majority of arenas are in that climate. now being built to be truly multi-purpose “At Marlins Park in Miami, however, venues that are not just intended for the roof is actually designed to be left “We're designing not only for the basketball or hockey, but for concerts, partially open in a hurricane, in order to weight of snow and ice that can drift circuses, ice shows, and conventions. reduce internal pressure on the inside of and pile up on top of this roof, but also the building. These intentionally planned the possibility that the fabric can be “Being able to easily convert these and strategically located gaps between punctured or torn and the resulting buildings from one function to another panels saved a significant amount of unbalanced horizontal loading that can quickly is really important to make structural steel and money by leaving create on our structure. sure that facilities maximise their that roof open a little bit and designing “So we're designing for a lot of event dates, revenue, and return the rest of the building accordingly.” different scenarios for both gravity on investment. The need to keep the playing surface and lateral loads associated with a “Right now we're working on a new healthy and grass growing is also a combination of those two factors. We arena for the NBA’s Milwaukee Bucks. major concern for designers. also spent a lot of time working on Populous and HNTB are designing snow and ice guards that keep those the building and we're the structural Miller said: “There’s a lot of talk about elements from sliding off the roof and engineer for the roof in addition to trying to find ways to grow natural onto the people below.” serving as consultants on the façade. grass under a roof by using transparent materials. Stationary, opaque canopies Miller said environmental factors are “The roof is very complex geometrically and even partially transparent roof a major driver of the design, shape, as most of these buildings are. It’s structures make growing natural grass materials, and the aesthetic of modern curving in plan and in section and nearly impossible below. sports venues. these multiple, curving surfaces have 19 PSAM Magazine 1st quarter 2018 v10.indd 19 19/03/2018 16:52 PANSTADIA & ARENA MANAGEMENT 1ST QUARTER 2018 to merge seamlessly to create a very transparent membrane solutions, either compressed design schedules with the dynamic shape that emphasises the on the roof, or façade, or both. So the use of innovative technologies. very iconic building that it’s going to be; industry is clearly headed that way. “The other thing that we have to keep one of the most recognisable buildings “I think another trend in design is the in mind when we're talking about in Milwaukee.” types of digital design and fabrication lightweight structures is the limitations He said the roof is designed for tools that are now available. They of the material itself. We're not dealing maximum flexibility with the rigging grid significantly improve the design with a metal deck, we're dealing with spread out across the roof. process, especially when tackling perhaps a very thin ETFE membrane “The rigging grid in Milwaukee complex geometric forms that which has a different set of design is both large in terms of area or architects are envisioning these days criteria and of capabilities, but also a coverage, but also in terms of its load and addressing the added complexity different set of limitations on what it carrying capacity. that tension structures introduce. can really do, the type of load that it can support. “It's going to be capable of handling “We're doing a lot with advanced anything that these performers are computational tools. Parametric “One thing we're looking forward going to throw at it.” modeling specifically allows us to study to is continuing innovation in these a lot of these different geometries, materials in terms of their ability to Roofing Trends multiple roof configurations and provide greater strengths that can options.