Designing 60-metre clear spans
When self-weight stops fighting you, the whole span table changes. A worked example with CHITOSPAN-ZX.
Every long-span designer knows the vicious circle. A longer span needs a deeper beam. A deeper beam weighs more. That extra weight is a load the beam now has to carry — over the same long span — so it needs to be deeper still. In steel, this feedback loop is what eventually caps economical span lengths and drives roof depths to absurd proportions.
Specific strength breaks the loop
The property that governs the loop is specific strength — strength divided by density. It measures how much load a material can carry before it has to start carrying itself. CHITOSPAN-ZX posts a specific strength around 314 kN·m/kg against roughly 60 for structural steel. Same strength, roughly a fifth of the weight.
Drop self-weight by that much and the feedback loop nearly stops turning. The beam that spans 60 metres barely has to account for its own mass, so it can be shallower, which makes it lighter still. Designers used to spending their whole depth budget on dead load suddenly have it back for daylight, services, or simply a thinner roof.
A span table isn't a property of geometry. It's a property of how much a material weighs relative to how strong it is.
A worked comparison
Take a simply supported roof beam over a 60-metre column-free hall carrying a typical roof load. Sized in S355 steel, the section is deep, heavy, and demands sizeable foundations just to carry the frame's own dead load. Re-sized in CHITOSPAN-ZX tension chords with a light lattice web, the same beam:
- carries the same design load with a markedly shallower section;
- reduces frame dead load enough to shrink the foundations and the seismic mass;
- arrives in longer factory-made lengths, because light members are easier to transport and lift.
Detailing notes
Chitospan is a tension specialist — design it into the tension chords and ties, and let a compression family such as Mycelith take the struts. Connections are bonded and bolted through cast end-fittings rather than welded; because there's no heat-affected zone, the joint keeps the parent strength. Our engineering team supplies capacity tables and end-fitting details with every grade.
Want capacity tables for a specific span and load case? Send us the geometry and we'll size the chords.