Truss and Layher Systems for Stage Structures

Box truss (square or rectangular cross-section) is the most common type for overhead rigging, offering high torsional rigidity and load capacity in multiple directions. It typically uses four main chords connected by diagonal bracing, making it ideal for long spans and heavy point loads like line arrays or LED walls. Triangular truss, with three chords, is lighter and more cost-effective for straight runs with uniform loads, but has lower torsional resistance, so it's often used for ground-supported structures or lightweight overhead applications.

The choice between box and triangular truss depends on span length, load requirements, and budget. For flown arrays or roof structures, box truss is preferred due to its superior strength-to-weight ratio and ability to handle off-center loads. Triangular truss is suitable for truss arches, stage legs, or decorative elements where loads are minimal and predictable.

Spigot connections use a tapered pin and sleeve system that allows quick assembly without tools, common in aluminum truss systems. They are fast and reliable but require precise alignment and are typically rated for lower loads than bolted connections. Spigots are ideal for touring and temporary setups where speed is critical.

Bolt connections use steel plates and high-tensile bolts, providing higher load capacity and rigidity. They are slower to assemble but necessary for heavy-duty structures like grandstands or large roofs. Many modular stage systems (e.g., Layher-style) use bolted connections for their strength and reusability. Always consult load tables to ensure the connection type matches the structural requirements.

Every truss system comes with span and loading tables that specify maximum allowable loads for given spans and configurations. These tables are derived from structural analysis and testing, accounting for factors like deflection, buckling, and material yield. For example, a 12-inch box truss might support 1,500 lbs over a 40-foot span, but only 800 lbs over 60 feet.

Engineers use these tables to design structures that meet safety factors (typically 4:1 for overhead rigging). It's crucial to never exceed published ratings and to consider dynamic loads from wind, movement, or crowd sway. For complex structures, a professional structural engineer should verify the design.

Ground support systems use towers or goalposts to support trusses from the ground, eliminating the need for building rigging points. They are common in outdoor events or venues without adequate overhead capacity. Ground support towers are typically braced with guy lines or outriggers and can be stacked to achieve heights up to 40 feet or more.

Flown systems suspend trusses from existing building steel or roof structures using motors or chain hoists. Flown rigging offers cleaner sightlines and faster load-in but requires certified rigging points and fall protection. The choice depends on venue capabilities, load requirements, and budget. SSOUNDS engineers often specify ground support for touring productions to ensure consistency across venues.

Layher is the gold standard for modular event structures, using a bolted connection system of steel frames, beams, and diagonal braces. These systems can be configured into stages of any size, covered roofs, grandstands, and even temporary buildings. The key advantage is the ability to create rigid, safe structures without welding or custom fabrication.

A typical Layher stage uses Allround scaffolding components: vertical posts with rosettes, horizontal ledgers, and diagonal braces. For roofs, a truss grid is often combined with Layher towers to support roofing panels. Grandstands use tiered frames with stair towers and handrails. All components are hot-dip galvanized for durability and weather resistance. Load capacities are well-documented, and assembly follows strict guidelines to ensure stability.

Designing a safe temporary structure requires understanding load paths, wind loading, and soil bearing capacity (for ground-supported structures). Engineers use software like RSTAB or Layher's own design tools to model the structure and verify compliance with local codes (e.g., BS EN 12812 for falsework, or IBC for temporary structures).

Key safety practices include: always using base plates and sole plates on soft ground, bracing towers in both directions, calculating wind loads for roof structures, and never exceeding manufacturer ratings. Regular inspection during assembly and before use is mandatory. SSOUNDS recommends partnering with certified riggers and structural engineers for any large-scale structure.