Tent Structures Expert Overview

The failure of temporary tent structures, like those used at outdoor celebrations, sporting events, and festivals, can become the subject of litigation involving personal injury or property damage claims. This article provides a technical overview of tent failures from a structural engineering perspective.

Our structural engineering experts are frequently retained to investigate the failure of tent structures of all configurations, ranging from small canopy tents to large, engineered event structures. Regardless of the size, shape, or anchoring method, our investigation and analysis procedures follow the same process.

Primary Structural Components of Tents

Temporary tent structures represent a unique class of engineered structures that combine architectural flexibility with engineering principles.

Tents vary in complexity and can be as simple as a membrane stretched over a single pole with stabilizing ties staked to the ground, or complex enough to resemble a traditional single-story building.

An engineered tent system can include several integrated structural elements working in concert:

1. Membrane Covering: The fabric envelope that provides weather protection and transfers wind, rain, and snow loads to the supporting framework. This membrane can be composed of different materials and fabrics such as PVC or polyester, canvas, or nylon.

2. Primary Support Elements:

• Posts: Vertical compression members supporting the entire structure and transferring loads to the ground
• Beams: Horizontal members spanning between posts, carrying roof loads
• Purlins/Rafters (often not present for simple tents): Secondary framing members supporting the membrane between primary beams

3. Stability System Components:

• Rigid joint connections: The connections between the posts and the beams that provide overall stability
• Braces (often not present for simple tents): Diagonal members providing lateral stability against horizontal forces
• Tension Ties: Cables or straps that resist outward and upward forces and maintain geometric stability
• Knee Braces (often not present for simple tents): Diagonal members connecting posts to beams to create rigid moment-resistant joints

4. Foundation System:

• Anchors: Connection points to the ground that resist lateral forces, uplift forces and overturning forces
• Base Plates (not always present): Elements distributing concentrated vertical loads from posts to the ground
• Ballast Systems: Weights (in lieu of Anchors) that provide resistance to lateral forces, overturning and uplift forces

Load Path: Critical for Structural Integrity

A complete load path is essential for tent stability. Loads (primarily wind) must be transferred through the structure to the ground through the following sequence:

1. Wind pressure acts on the membrane surface
2. Membrane transfers these forces to the structural members (beams and posts)
3. Beams transfer loads to posts
4. Posts transfer loads to anchoring system
5. Anchoring system transfers loads to ground

Any discontinuity in this load path can lead to catastrophic failure. Unlike permanent structures with rigid connections and substantial mass, tents rely on proper tension, bracing, and anchoring to maintain structural stability.

More on load paths in this article.

Design Loads for Tent Structures

Tent structures must be engineered to resist multiple load types:

• Dead Loads: The self-weight of structural components including frame, membrane, and attached equipment (lighting, HVAC systems)
• Live Loads: Occupancy loads, maintenance personnel, and equipment loads (for more complex tents)
• Environmental Loads:
  • Wind Loads: Both positive pressure (windward side) and negative pressure/suction (leeward side and roof)
  • Snow Loads: Vertical loads on roof surfaces in applicable climates
  • Rain Loads: Particularly important for ponding considerations

Temporary tents are vulnerable to wind loads due to their lightweight nature and large surface areas. Proper engineering must account for site-specific wind exposure, topography, and seasonal conditions.

Wind uplift forces, which create significant tension in anchoring systems and can cause membrane billowing, progressive failure, or complete detachment of the membrane, straps, or connections. Windspeeds and the corresponding forces for temporary structures are defined in jurisdiction adopted (and sometimes modified) codes and standards.

The American Society of Civil Engineers (ASCE) publishes a standard ASCE 37 - Design Loads on Structures during Construction which defines the permissible reduction of forces if the erected structure is temporary. The factor by which the wind loads may be reduced depends on how long the tent will be up.

Modern meteorological and weather prediction tools make monitoring weather a relatively simple task for owners and erectors of tents or the delegated party. Most wind events are foreseeable, making many tent failures preventable. Some tent failures occur at windspeeds below that which they are required to resist.

Anchoring Systems

The anchoring system serves as the final component in the load path and represents a common point of failure in our forensic casework. Two primary types are employed:

Ballast Systems: These systems typically are comprised of concrete blocks, water-filled containers, or steel weights
Advantages: No ground penetration, suitable for paved surfaces
Limitations: Significant weight requirements, sliding potential

Ground Anchoring Systems: These systems typically consist of drive stakes, screw anchors, or earth anchors and resistance is provided through soil friction and soil interaction.
Advantages: Higher pull-out resistance, less material required
Limitations: Performance dependent on soil conditions, not suitable for paved areas

Engineers must calculate required hold-down forces based on anticipated and foreseeable uplift and lateral loads, including appropriate safety factors. Anchoring systems must be verified through appropriate testing methods or published test results.

Primary Failure Mechanisms of Properly Designed and Erected Tent Structures

Two principal failure modes dominate tent structure collapses. The first is a lateral stability failure. This type of failure can result in total or partial collapse. Lateral stability failures can be caused by insufficient lateral bracing, inadequate moment (rigid joint) connection, or a lack of lateral restraint at the base.

In this failure mode, wind or other lateral forces create rapid or progressive deformations of the frame causing the posts to rotate or shift, ultimately leading to the failure. This type of failure is often preceded by visible deformation of the frame system but can also happen suddenly and without warning. It can involve significant damage to frame and joint components.

The second primary failure mode is an anchorage/ballasting failure, which results from inadequate anchor system capacity or improper installation. With this failure mode, the structure can tip over, hop/jump, blow away. It can occur when the anchorage or the strapping connecting frame to the anchors is insufficient or loose. This failure mode is frequently associated with improper anchor and strap installation or insufficient ballasting.

Tent Failure Expert Witness Investigations

At Robson Forensic, our experts are frequently tasked with investigating the causation, standard of care, and contributing factors to the failure of tent structures. We provide investigations and analysis of the failure of tent structures, accounting for the applicable standards of care, the applicable loads, and the causation of the failure.

For more information, submit an inquiry or call us at 800.813.6736.

Featured Expert

David Beh, P.E., MSCE

Civil Engineer & Construction Expert

David Beh is an expert in structural engineering with nearly two decades of professional experience in the design of buildings and a variety of other structures. He has specialized knowledge in wind,… read more.