Trussing Safety

If you look back at some of my older posts (Oct.28, 07 and Mar.16, 09), you will see my emphasis on safety and effective risk management. One of the biggest concerns for safety is in trussing. I am still amazed at the number of major trussing collapses that occur each year at special events. Here are just a few examples from YouTube that have happened in the past couple of years.

1. Christina Aguilera and Justin Timberlake Concert 2008

http://www.youtube.com/watch?v=7pDyfA3hsng

2. Elton John Chichen Itza Concert Stage Collapse 2010

http://www.youtube.com/watch?v=WXszTmkzqKw

3. Madonna Concert Stage Collapse in France 2009

http://www.youtube.com/watch?v=XP0VoqYAc-Y&feature=related

4. Stage Collapse at Big Valley Jamboree in Canada, August 2009

http://www.youtube.com/watch?v=vt-vOBG78uA&feature=fvw

5. Silverdome Truss Collapse 2010

http://www.youtube.com/watch?v=crQQ6XTGuYM&feature=related

6. South African Stage Trussing Collapse 2010

http://www.youtube.com/watch?v=wHY9V-QxqzM&feature=related

7. Roof System Collapse in Turkey

http://www.youtube.com/watch?v=2ZDvrVW-TZI&feature=related

8. Rocklahoma Side Stages Collapse 2008

http://www.youtube.com/watch?v=GdXgIOaEaaA&feature=related

It's pretty obvious that even production teams for the most well-known stars have problems. That still is no reason to bypass the necessary equipment safety standards and procedures for safe installation of trussing used in smaller events. But we're rushing things a bit. Let's look at trussing from the beginning.

Trussing as we know it, started to develop at the end of the 1970s in response to the entertainment industry’s demand for lightweight, strong temporary structures that could span the width of a stage and be used to hang lighting and audio systems. Familiar with the spatial lattice structures found in bridges, scaffolding, and buildings, manufacturers used this as the basis for modern truss design. Today it is ubiquitous in the industry and comes in a wide variety of sizes, shapes, colors, and strengths.

Trussing must be able to withstand loads imposed on it in shear (i.e. force directed along the cross section, such as high loads on top of a vertical truss section) and in deflection (i.e. force directed down and perpendicular to its horizontal access, such as too many luminaires clamped in one position). The amount it can withstand depends of course on its size and rated load. Each type and size of truss is rated by the manufacturer for specific maximum loads under these conditions. It is therefore critical that riggers know the exact loads that will be imposed on the truss in these conditions and what the total weight of the loaded truss will be so that the correct choice of supporting wire rope cable, slings, and chain motors may be made. Not only that, but the truss supplier for an event (e.g. usually the lighting company) is obligated to understand the load rating of their truss and to choose the proper truss accordingly, knowing in detail what the loading will be before the truss is ever rigged into position.

Particularly important are unique loading scenarios encountered outdoors. These include:

• Wind. Wind can cause damage to canopies and walls, it can overload trusses and towers due to the extra load of attached walls, and it can lift all or part of the complete structure.
• Rain or snow. This can make trussing slippery for climbing, it can cause overloading of rooftops due to accumulation of snow or water, it can cause short-circuiting in control systems, and it can cause the support of saturated soils to weaken. 
• Lightning. This can cause severe personal safety risk if it hits towers. 
• Temperature. Solar heat can cause aluminum to become extremely hot, thus making it unsafe to the touch. It may also cause the safe temperature of any polyester cling covers to exceed their allowable limit. (e.g. surface temperature can reach 150 C, greater than the normal safe limit for polyester of 100 C).

It is therefore imperative that such things as roofs be constructed properly and with due consideration of the expected weather conditions. For example, the inclusion of supporting guy wires, base distance frames (to minimize compression loads), and adequate ballast is absolutely necessary. Additionally, heights of towers and roofs must be restricted to recommended maximums, both indoors and outdoors. For example, the height of a tower grid system should be no more than 6 m if the width of the outrigger tower base is 2 m (outdoors is generally three, and indoors four times the base width as a rule-of-thumb). A properly qualified rigger and the truss supplier should be able to certify compliance with these requirements.

From this it can be implied that to rig trussing at an event without using a properly qualified rigger is asking for trouble. And that goes for trussing hung indoors or roof systems that are ground-supported outdoors.

One positive recent development is the introduction of a North American, industry-wide certification program by the Entertainment Services and Technology Association (ESTA). This program, called the Entertainment Technician Certification Program (ETCP), requires that riggers pass a three-hour knowledge exam set and scored by an independent body, the Applied Measurement Professionals, Inc. There are two certification categories: ETCP Certified Rigger – Arena and ETCP Certified Rigger – Theatre. For the special event industry, the arena certification is the desired one and it is strongly recommended that producers only work with such qualified individuals.

You wouldn't want your event to end up being a disaster video on YouTube.

Stage Safety

Back in March I detailed how to determine the proper horizontal size of a stage. The topic has proven to be quite popular, so I am now going to add some more to it and discuss stage safety.

Too many event producers and event managers are unaware of the fact that there are currently no North American standards for the allowable loading of stages. Why is this important? Consider the fact that, in the last seven years, at least fifteen temporary stages have collapsed at special events in various countries around the world. Now I'm not talking about the trussing and roof structures over or around or near stages but the actual stage surfaces themselves. Trussing is another serious problem in itself and I'll talk about it in the future. In many of these incidents, people were seriously injured or killed. In fact, some of the collapses were of the stages that major stars were to perform on.

Here are links to several You Tube videos of stage collapses:

• Brazilian Stage Collapse
• Super Bowl Stage
• Uma Bharti Stage Collapse
• Stage Collapsed in Hinthada
• Floor Collapses at Starfield Concert

Event producers must be aware of the allowable loading for any given stage design, and since there are no standards, it makes this point even more important because, as part of proper risk management, the stage provider, whether it is a venue or a subcontracted staging company, should be able to provide producers with the deck manufacturer’s figures for safe loading limits. In the case of customized staging, the builder should have made proper calculations or should provide proper calculations from a certified structural engineer to prove that the staging will be adequate for the loads anticipated.

If the staging is owned by a venue, that venue should be able to provide an event manager/producer with the documentation for the allowable loading of the staging. Guesswork or corporate knowledge does not suffice.

I'll delve deeper into the actual loads in my next post.

Interesting Entertainment and Event Links

1. Compilation of more than 40 dance scenes from movie vaults
http://www.flixxy.com/movie-dancing-compilation.htm

2. 2010 Harbin China ice and snow sculpture festival
http://www.boston.com/bigpicture/2010/01/harbin_ice_and_snow_sculpture.html

Thanks to meeting specialist Corbin Ball for the links in his always informative newsletter at http://www.corbinball.com/techtalk/index.cfm?fuseaction=cor_av&artid=8153

More New Tent and Tensile Structure Ideas

I have a Russian friend who just won a prestigious award for his tent design from the Industrial Fabrics Association International. His designs are amazing. Check out http://www.ifaipublications.com/iaa/articles/2213_summer.html.

While you're there also take a look at other winners who have some very creative concepts with potential application for special events.

Technical and Logistical Requirements for Outdoor Venues

Last time we looked at the techinical requirements for indoor venues. This time, we look at outdoor sites. Outdoor sites present an entirely different set of concerns for producers, some requiring extensive and ongoing monitoring. Some of the key ones are:

• What is the optimum layout of the site for the most benefit to attendees and the least impact on surrounding neighbors? This includes optimization for foot and possible vehicular traffic.
• Where will each and every temporary structure be located? How will necessary power be run to them if needed?
• What is the potential acoustic impact on neighbors and must event parameters be changed to minimize the impact?
• Where will entrances and exits be located and how many of each will there be?
• How accessible is the site for technical equipment load-in and also for emergency vehicles (e.g. fire, police, and ambulance)? Where can technical vehicles be parked?
• What is the ground surface and is there anything required to protect it from damage?
• Is security fencing required and how much?
• Are there any dangerous areas or areas that cannot be used because of hidden infrastructure (e.g. water mains, telephone lines, sewage, electrical)?
• Where exactly are water and electrical power located, if any? Can either be tapped into for use at the event? Is portable power required?
• What is the best location for portable toilets?
• What is the best central location for waste and refuse accumulation?
• Is there any available site lighting and is it adequate or must additional be brought in?

Of course, this is a very basic list, but at least it should get you started on surveying a site and determining if it will be suitable for an event.

Armed with the answers to these questions, the producer can now proceed to drawing a site or venue plan to scale and to producing a preliminary production schedule.