ANSI E1.21-2024: Temporary Structures for Outdoor Events

Whether it is a music, film, food, culture, or art festival, each type of festival offers a unique and enriching experience to immerse oneself in different forms of art, culture, and tradition. It is no wonder that approximately 32 million people attend at least one music festival in the U.S. each year. ANSI E1.21-2024: Temporary Structures Used For Technical Production Of Outdoor Entertainment Events provides regulations and guidelines for temporary special event structures used in the technical production of outdoor entertainment events.

What Is Considered the Most Famous Music Festival?— 1969 Woodstock Music & Art Fair

Taking place in nearly 300 acres of rolling farmland in rural Sullivan County, NY, the 1969 Woodstock Music & Art Fair is considered the most famous music festival of all time as it was a watershed event in the transformation of American culture. In fact, under Social History and Performing Arts/Music, Woodstock is nationally significant as one of the most important cultural and social events of the second half of the twentieth century.

Over three days, the festival featured thirty-two individual performers, folk singers, blues, and rock and roll bands—such Jimi Hendrix, Janis Joplin, The Band, The Who, Sly & the Family Stone, Grateful Dead, Joe Cocker, and Crosby, Stills, Nash & Young. It is estimated that the festival has between 400,000 to 500,000 attendees.

Woodstock was more than just a festival; however, it marked the culmination of changes in culture that took place across the 1960s from civil rights, lesbian and gay rights, the elimination of poverty, ending the Vietnam War, women’s rights, and universal voting rights. It was the definitive expression of the musical, cultural, and political idealism of the 1960s. The music and culture of the Woodstock era lives on in today’s concert and festival venues.

What Is ANSI E1.21?

ANSI E1.21-2024 establishes a minimum level of design and performance parameters for the design, manufacturing, use, and maintenance of temporary ground-supported structures used in the technical production of outdoor entertainment events. This American National Standard presents a coordinated set of rules that may serve as a guide to government, municipal authorities, and other regulatory bodies responsible for public safety in the context of special events. The artist, set designer, riggers, production company, stage managers, and structural engineers are all involved in the installation and design of temporary structures and their production, and as such they must work together to ensure public safety around these structures. Custom temporary structures supporting performance platforms are included in the scope of the standard. The purpose of ANSI E1.21-2024 is to ensure the structural reliability and safety of these structures.

The standard does not address fire safety and safe egress issues. Further, general public access temporary structures, such as food vendor tents, portable toilets, and other portable temporary structures for directly serving the audience or attendees at outdoor entertainment events, are not included in the scope of this standard. ANSI E1.21-2024 also does not include manufactured modular floor staging systems used as platforms for performance, where such structures are independent of other temporary structures.

What Are the Changes in ANSI E1.21-2024?

The 2024 version of ANSI E.21 does not have any critical revisions to its prior 2023 version. The main update is in Section 3: Design and Engineering. In section 3.2 under the sub-header of Design Requirements, ANSI E1.21-2024 removed section 3.2.6, which stated “when using allowable stress design load combinations of SEI/ASCE 7, reduced wind loads as determined by this standard shall not be multiplied by a load combination factor of less than 1.0.”

Changes in the 2023 Version of ANSI E.21

ANSI E1.21-2023 superseded the 2020 edition. This new edition brings E1.21 into line with the upcoming 2024 International Building Code in an unprecedented harmonization collaboration when dealing with outdoor structures. The International Building Code 2024 provides design loads and operational management plans that both the building official and structural engineer can agree on, and it acknowledges that performance-based criteria for a structure with a limited duration can be achieved safely.

Types of Temporary Structures

Stages take many forms and sizes, from large steel structures to lightweight aluminum box truss structures that can be required to support 30 to 50 tons of rigging equipment.

1. Mobile Stages: are pulled behind a truck or semi and open up into stages that can be 50 feet wide and up to 40 feet tall. Hydraulics are typically used to open the stages with guy wires and locking pins installed after deployment. The chassis and structure self-weight, along with additional ballast, if necessary, are used to resist sliding and overturning loads.
2. Concert Stages: are assembled, raised into position, lowered, and placed on a truck to travel to the next show. Large stage roofs are typically erected on the ground and hoisted into place using a pulley system attached to the tops of the truss columns. The motor attaches to the structure’s base, and the lift line wraps over two pulleys at the top of the truss. It then connects to the fully assembled roof structure. The roof structure, supporting only its self-weight, is lifted into place, locked out, and ready to support the show loads 
3. Aluminum Roof Stage Structures (aluminum shapes and trusses): are sometimes 40 feet x 40 feet x 30 feet tall and can be used as an erector set to support rigging loads. Sticks of trusses, typically 10 feet in length, are bolted together to form large roof systems supporting the show’s rigging.

Outdoor Concert Weather Planning

When planning an outdoor concert, festival, or another type of outdoor event, there is no escaping dealing with weather factors: air temperature, air pressure, humidity, cloud cover, wind, and precipitation. ANSI E1.21-2024 maintains that the engineering documentation should include definitive statements about the operating limits of the temporary structure including environmental conditions and physical forces:

• Environmental Limitations: notes and calculations addressing any specific limitations regarding the addition of coverings, canopies, overhanging elements, side walls, backdrops, or any other feature that can significantly change wind pressures, total weight, or attract snow and ice
• Environmental Thresholds: environmental thresholds that require specific mitigating actions; required actions when specified environmental thresholds are reached
• Live load: allowable live load
• Payload: allowable payload, per element or subassembly as applicable
• Seismic Design Loads
• Snow/Ice: allowable snow/ice load or accumulation
• Temperature: allowable minimum and maximum temperature
• Wind: unfactored service-level design wind speed; wind reduction factors used and design wind speed; allowable wind speed during erection of the temporary structure, if different than the design wind speed; assumed effective wind area inclusive of the temporary structure and equipment suspended from, or attached to, the temporary structure; notes and calculations addressing effects of wind pressures on coverings and overhanging elements when effective wind area under roof/canopy/overhanging elements is changed; notes and calculations addressing effects of wind pressures on coverings and overhanging elements if side walls or backdrops are changed

ANSI E1.21-2024 notes that if the design of a temporary structure calls for mitigating actions or changes to the temporary structure configuration when specified environmental thresholds are reached (e.g., lowered to the ground, or removal of superimposed loads), such as wind speed or snow accumulation, the user information should contain definitive statements about these operating limits for each defined environmental condition.

ANSI E1.21-2023: Temporary Structures Used For Technical Production Of Outdoor Entertainment Events is available on the ANSI Webstore.