Monday, 1 August 2011

Crazy Summer Weather and Stage Roof Collapses

Every recent summer seems to bring out not only the worst in weather but also dangerous situations at summer festivals that accompany the weather.

Exactly two years ago today, a main stage roof at the Big Valley Jamboree in Camrose, Alberta collapsed, killing one person and injuring 75 as a result of a sudden storm and high winds. As of last Friday, 33 charges were laid stemming from that collapse.

On July 17th this year, a main stage collapsed at the Ottawa Bluesfest while Cheap Trick was playing. This collapse injured at least 5 people, one seriously. The collapse was also attributable to a violent gust of wind.

Although I cannot make a comment about how the producers of either event handled the respective situations, from what I can glean from news reports, they were both aware of the ANSI standard that governs the construction and safety of outdoor stage roof structures, particularly with respect to wind gusts. For reference, see American National Standard E1.21 - 2006 - Entertainment Technology, Temporary Ground-Supported Overhead Structures Used to Cover the Stage Areas and Support Equipment in the Production of Outdoor Entertainment Events. It is available at

What most worries me as I read these reports is not whether the producers of these large festivals followed the standards, it is how many producers and planners of much smaller community and private outdoor summer events even know that such a standard exists, and what kind of liability situations they are unknowingly placing themselves and other organizations in. These are strict guidelines that call for - among other things - full documentation of engineering analysis and a complete Operations Management Plan that covers situations with high winds. Below are two applicable sections of the standard:

3.5.2 Wind loading The wind load on all exposed surfaces including but not limited to truss and tower sections, scaffolding, roof skin, back drops, banners, advertisements, and suspended equipment shall be considered. The overall stability and resistance to wind uplift and overturning forces shall be provided by means such as wire guys anchored to ground anchors (or ballast), diagonal braces, ballast applied to the tower sections, self weight of roof top (the dead load) and live loads. The design wind speed for structures as defined by this document shall be 0.75 times the basic wind speed defined in ASCE 7. Where a structure will be erected in an area prone to hurricanes, and precautionary measures can be taken such as dismantling and adequate securing in the event of a hurricane warning, a basic wind speed of 90mph, 3 second gust, shall be allowed per ASCE 37, section 6.2.1. A reduction in effective wind area can be permitted, provided that such elements can be removed in less than 5 minutes. The method of wind monitoring and removal of the equipment shall be clearly defined in the Operations Management Plan. Not withstanding the above, the structure shall be designed to resist wind forces on all elements associated with the design wind speed of 40mph.

3.5.3 Operations Management Plan The Operations Management Plan shall be prepared by the User and his engineering advisors. Reference shall be made to Clause 5.2.3 of this document. The Operations Management Plan shall be based on sound engineering analysis and the allowable loads as defined in the engineering documentation. The Operations Management Plan shall define the actions to be taken for different parts of the structure and cladding (where applicable) under prescribed loading conditions, with particular regard to wind loads. No action shall be taken that shall reduce the overall lateral stability of the structure.

The standard goes on to discuss the need for proper consideration of the supporting ground surface, lateral loading, proper design of trussing and the provision of associated drawings and calculations, plus a host of other detailed requirements.

I've hammered away at this topic before in this blog and also in my books. My contention is that full compliance with this ANSI standard not only should, but must, be written into every contract that an event planner/manager or producer has with a supplier who has anything to do with the construction and/or erection of a stage roof system to be used outdoors. It does not matter how big or small your event may be. You can be sure, that come the day of reckoning when a disaster happens like those mentioned above, the courts are going to be calling for a detailed paper trail.

Beware of summer storms!

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