A R C H I T E C T U
R E , D E S I G N & E N G I N E E R I N
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Lee Slade P.E., Senior Principal
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When the show concluded at 10:45 PM, over 18,000 fans left, satisfied that the show was a success. Only the riggers were left to appreciate how well the arena’s new state-of-the-art, roof-hung, rigging grid handled the speakers, lights, and other exotic electronics required to stage the show. But the touring event industry is a small world, and word will spread quickly. Soon Toyota Center will enjoy the coveted ‘buzz’ and long-term financial, as well as promotional benefits, of a building that is easy and economical to rig for a new show. Though a nominal part of the overall arena construction cost, the
grid — which typically consists of a network of steel tubes and
channels interwoven above the arena floor near the bottom chord of the
main steel truss structures — is a crucial aspect of its competitive
success. Buildings that set up easily and quickly are popular with
rigging crews, as well as the promoters who hire them, leading to a
marketing advantage for those building managers with well-designed and
flexible rigging grids. All too often, however, the grid inherited by
venue managers suffers from a lack of design foresight, attention to
detail, and a lack of appreciation for the realities of the rigging
industry. These grids are more difficult to rig and their buildings less
competitive than they could be. |
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As a structural designer of numerous arenas, Walter P. Moore has learned many of the key lessons required to create economical and — even more important — easy-to-use grid systems. This article provides a brief overview of some of the key issues involved. Key Issues Most venues in first, second, and even third-tier cities can, if they are aggressively marketed, attract the vast majority of touring shows. As a result, the rigging grid in a particular venue must accommodate a wide variety of shows during the design life of the venue. Once the building opens, the building manager is usually responsible for confirming that the building can safely handle a given show. He or she must compare the technical capabilities of the building’s rigging grid to the technical demands, including weight, size, location, and attachment scheme, of the hung speakers, speaker clusters, lights, and related electrical components included in a specific show package. This comparison is often performed ‘on the fly’, during negotiations to book the act into the venue. The cost and time to accomplish any required upgrades to the grid are highly undesirable, and often unacceptable in the competitive building management business. As a result, capacity and flexibility to accommodate the heaviest and most complex of shows is desirable to keep buildings in even smaller markets as competitive as possible. So, the all-important question; do well-designed rigging grids cost
more? Not necessarily, say experienced structural designers, and even if
they do, the incremental cost of a well-designed grid is nominal in the
total structural construction cost of an arena. Modern arenas are
generally being designed with grids that support at least 120,000-pounds
of total load. |
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Movable electric chain winches, left and below left, can be positioned throughout the rigging grids. |
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A few arenas, including the AmericanAirlines Center in Dallas, have 150,000-pound grids. Although these loads might seem heavy, the total amount typically represents only about 1% to 2% of the total load on the roof structure itself. For example, at Toyota Center, the 120,000-pound (60-tonne) capacity rigging grid is supported by a superstructure that includes about 2,000-tonnes of steel weight alone. Yet the incremental value of a user-friendly rigging grid returns dividends with every show set-up, perhaps 50 to 80 times per year in busier venues, year after year. Modern shows work to rigorous schedules, often limited in tour range
by the distance they can drive overnight. Arriving at a venue early in
the morning, set-up generally starts before dawn and proceeds as quickly
as possible, to allow time for sound testing and rehearsals before fans
arrive for an 8pm show. |
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Almost before the fans clear out after the performance, riggers are hard at work breaking down the show components. By 2am, they are on the road again, reloaded into their 18-wheelers and heading towards the next engagement. During this crucial 20-hour set-up and breakdown period, buildings with effective show rigging grids show their mettle. Riggers and stagehands swarm over the building, hanging speakers and other components in carefully predetermined locations, using cables that are draped over steel rigging beams. ‘Bridles’ are used to distribute loads and to accurately locate show components. The rigging load capacity itself — say 120,000-pounds — is only the simplest measure of the grid capacity and is actually quite misleading. Though building managers are becoming much ‘savvier’ in their knowledge of rigging loads and issues, the total capacity is still often used in marketing the venue because it is simple. The total load, however, usually does not adequately represent the distribution of load capacity over the show area. The total grid capacity is actually comprised of numerous smaller point loads that represent the actual rigging loads from cable-hung show elements. Because show designers often arrange show elements in clusters, non-uniform distributions, and speaker banks, the rigging grid itself must be thoughtfully designed to accommodate specific point loads. In Walter P. Moore’s experience, successful show rigging grids must accomplish each of the following: Build in Adequate Load Capacity Grids must safely accommodate the total rigging loads of the vast majority of touring shows, including future shows that have not yet been designed. Minimum total rigging weights of 120,000-pounds are recommended, though the distribution of the point loads is more important. Time will tell if heavier shows in the future may drive rigging loads even higher. The capacity must be well distributed by zone, in order to accommodate likely layouts for centre stage shows and end stage shows, depending on the seating layout and staging strategy of the venue. Specific load-points, with capacities of 1,000-pounds up to 30,000-pounds or more, are required for flexibility. Some building managers prefer the simplicity of uniform grid-point capacity, but higher capacity load-points can often be helpful to rigging designs. To avoid confusion, each load-point should be clearly marked and colour-coded with markings that are visible from above and below. Make the Grid Easy and Safe to Rig After load capacity, the most important characteristic of a rigging grid is its ease of use. It should have acceptable access — preferably without restriction — for riggers, via catwalks and ladders. Elevator access is mandatory to move riggers and equipment quickly, without tiring riggers by requiring them to repeatedly climb ladders, whilst lugging heavy equipment or show components. Safe and solid walk surfaces, with a minimum number of ‘step-overs’, ‘duck-unders’, and rogue ‘headknockers’ to complicate the route, are highly valued among riggers for they allow them to move rapidly and safely. Tie-off anchorages for safety cables are also an excellent idea. Riggers generally attach hung elements to the rig with a simple wrap attachment and a motor-driven chainfall, mounted at the lower end of the rigging cable. Grid beams should have smooth and rounded corners if practical, and top surfaces should be solid and without burrs, to avoid damaging cables or hanging up. Coordinate with Other Ceiling Space Elements Grids are generally comprised of an orthogonal set of steel beams arranged with a typical rectangular layout. For economy, the grid beams should work in rhythm with the structural truss layout, and sometimes even share elements with the trusses, secondary elements, or catwalks. Whilst this is encouraged, they must be designed and detailed carefully to ensure that shared elements do not compromise the accessibility of the grid. Sometimes shared elements do not prove cost-effective. For example, on a recent arena project, our strategy to save construction costs by using the same beams to support both the rigging grid and catwalk systems was rendered moot when the contractor subsequently substituted modular, prefabricated catwalks. In addition to coordination with the primary structural elements, the grid location and layout must recognise the location of HVAC ductwork, scoreboards, and catwalks, as well as lighting and other access platforms. At the newly opened Arena at Gwinnett Center in suburban Atlanta, thoughtful design improved the grid significantly. The main HVAC ducts were located at the perimeter of the arena, away from the rigging and catwalk system, allowing full head-height access for riggers. This building has been lauded as among the easiest to rig in the country and will benefit from that reputation for years to come. If permanent spotlights are located above grids, structural engineers
and lighting designers must coordinate the path of the light beams to
avoid grid beams. Placing the light platforms below the grids in the
first place can minimise some of the coordination challenges whilst
creating others. Some designers have discovered, with horror, that
spotlights light up their grid rather than the performers. Because of
this, some building managers prefer a wider grid spacing, although this
strategy yields fewer load-points and can create bridling challenges.
Others, especially those with grids located closer to the performance
floor, prefer a tighter grid to simplify bridling. At Walter P. Moore,
we have designed successful grid systems with grid layouts as large as
30ft by 30ft, and as small as 10ft by 10ft. |
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Case Studies Several recent arenas — each structurally designed by Walter P. Moore — illustrate the practical application of these recommendations: TOYOTA CENTER: At the Toyota Center, Walter P. Moore worked with sports specialist HOK S+V+E and architect-of-record, Morris Architects, to develop a grid with 120,000-pound capacity. The grid uses a 10ft by 25ft module to seamlessly merge it with the main structural system. Because the main structure bisects the roof into four quadrants, the centre stage grid was separated into four 40ft by 50ft quadrants. End stage shows are supported by a 75ft by 112ft grid layout. In its first outing, the grid easily accommodated the 54,000-pound show set up for Fleetwood Mac. BAYFRONT ARENA: The new Bayfront Arena in Corpus Christi, Texas, was designed by Arquitectonica, with architect-of-record, TVS, of Atlanta, in association with local architect, Gignac and Associates. It will feature a 120,000-pound capacity rigging grid when it opens next year. The grid is arranged in a large 28ft by 21ft module, which will allow high ceiling-mounted spotlights to penetrate the grid without shadowing. Although a lower rigging load was considered by the owner to save costs, a value engineering study showed that the structural savings would be nominal, yet would compromise the event flexibility, so the idea was abandoned. ARENA AT GWINNETT CENTER: The 12,000-seat Arena at Gwinnett Center was designed by a team led by Rosser International of Atlanta. A 120,000-pound capacity grid is arranged in a rigorous 15ft by 15ft module, for simplicity of rigging planning. The grid extends over a 135ft by 286ft area, to allow centre or end stage shows. For economy, the structural engineer used the bottom chord of the main trusses as rigging beams, saving money and improving access to the grid. Local riggers are already raving about the rigging system due to its simplicity and ease of use. Trends Technology innovations continue to shrink the size of virtually all electronics, including speakers, lighting clusters, and related electronics. However, total show loads do not seem to be going down accordingly, as show designers pack more components into show set-ups to make shows more exciting and more diversified. The author of this article, Lee Slade of Walter P. Moore, is currently conducting a detailed research programme, intended to identify emerging trends in the design of future shows and thus highlight the characteristics, and capacities, of the most competitive arenas of the future. If you are a building manager and wish to participate, please contact Lee Slade direct, at the email address noted at the end of this article. No one knows who tomorrow’s greatest act will be, or what rigging
loads might be required to stage their outrageous shows. What is
certain, however, is that those building managers who can offer a
competitively designed rigging grid will be the winners in attracting
them to their venues. Those will be the building managers who “rig to
win”. Acknowledgements: About the Author: |
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Toyota Center enjoys a user-friendly 
ll eyes in the
house were on Fleetwood Mac’s Lindsey Buckingham as he cranked up his
guitar to kick off their recent show in Houston with the first
performance in that city’s new Toyota Center. Over the next two and a
half hours, the new arena demonstrated its capabilities to host a
powerful and diversified musical act, showcasing the band’s trademark
range, from Buckingham’s rollicking guitar riffs to Stevie Nicks’
poignant ballads, finally concluding with the fearsome bongo pounding
and howling vocals of Mick Fleetwood. 
