Truss and Layher Systems for Stage Structures

Box truss (square or rectangular cross-section) is the most common profile for overhead rigging, lighting, and sound support. Its four-chord design provides high torsional rigidity and evenly distributed load capacity, making it ideal for long spans in flown arrays or ground-supported roofs. Typical sizes range from 12"x12" to 20"x20" or larger, with chord diameters and wall thicknesses tailored to load requirements.

Triangular truss (delta truss) uses three chords, offering a lighter, more aerodynamic profile often used for lighting towers, PA wings, and curved applications. It is less rigid torsionally than box truss but can be more cost-effective for shorter spans or vertical loads. For heavy point loads or large cantilevers, box truss is generally preferred. SSOUNDS engineers often specify box truss for flown line array hangs to ensure minimal deflection and predictable load paths.

Spigot connections use a tapered pin and sleeve system that allows rapid assembly without tools. They are common in mobile truss systems for touring and temporary events where speed is critical. Spigot joints are typically rated for lower bending moments compared to bolted connections, so they are best suited for straight runs and moderate loads.

Bolt connections (bolted flanges or bolted corner blocks) provide higher structural integrity and are required for heavy-duty applications, long spans, or permanent installations. Bolted joints transfer moment more effectively and are less prone to loosening under vibration. Many national standards (e.g., BS EN 13814) mandate bolted connections for large span roofs and grandstands. When designing a flown PA system with long line arrays, SSOUNDS recommends bolted truss for main support beams and spigot for secondary lighting bars where speed is beneficial.

Every certified truss system comes with span and loading tables that specify maximum uniformly distributed load (UDL) and point load capacities for given spans and configurations. These tables are derived from structural analysis and physical testing, and they must be followed without deviation. Factors include chord size, bracing pattern, material (usually 6082-T6 or 6061-T6 aluminum), and connection type.

For example, a 12"x12" box truss with 2" OD chords may support a UDL of 500 kg over a 10 m span but only 200 kg over a 15 m span. Point loads require further derating. Always consult the manufacturer's tables and have a qualified structural engineer verify any custom configuration. SSOUNDS integrates loading data into its system design software to ensure every flown array stays within safe limits.

Ground support towers (goalposts or towers) support overhead truss from the ground, eliminating the need for building rigging points. They are ideal for outdoor events, tents, or venues without adequate roof loading capacity. Towers are typically braced with guy lines or outriggers and must be ballasted or anchored per engineering calculations.

Flown systems suspend truss from existing structure (roof beams, grid, or chain hoists). They offer cleaner sightlines and faster load-in but require certified rigging points and fall protection. The choice between ground support and flown depends on venue constraints, load requirements, and budget. For large festival stages, a combination of ground-supported roof truss and flown PA wings is common.

Layher is a leading manufacturer of modular scaffolding and staging systems, widely used for temporary stages, seating grandstands, and event roofs. Their system uses a wedge-lock connection (similar to Allround scaffolding) that allows rapid assembly without loose parts. Components include vertical standards, horizontal ledgers, diagonal braces, and decking units.

Modular staging systems can be configured into almost any shape: flat stages, tiered seating, covered roofs, or combination structures. Load capacities are well-documented, and systems can be engineered to meet local codes (e.g., BS EN 12811, BS EN 13814). For example, a Layher stage deck might support 5 kN/m² live load, suitable for heavy PA equipment or dancing crowds. SSOUNDS often works with staging providers to integrate PA towers and delay towers into modular grandstands for optimal coverage.

All temporary structures must be designed, erected, and inspected by competent persons. In Europe, the standard EN 13814 governs temporary structures for event and entertainment use. In North America, ANSI E1.2 and local building codes apply. Structural calculations should account for dead load (truss, rigging, speakers), live load (wind, snow, crowd), and dynamic loads (wind gusts, crowd movement).

Certification involves material testing, weld inspection, and load testing of representative assemblies. Reputable manufacturers provide certificates of conformity and design reports. For custom structures, a chartered structural engineer must sign off. SSOUNDS ensures all its flown arrays are designed within the certified limits of the truss system and that ground support towers are properly ballasted.