Geometry: clear span is everything

Hangar design starts with the largest aircraft or helicopter the building must accept — wing-tip to wing-tip plus safety margins. Clear span typically ranges:

  • Helicopter hangar: 18–35 m
  • General aviation hangar: 25–45 m
  • Wide-body aircraft hangar: 60–100 m+

Door height is the second driver — typically 8–18 m for helicopter hangars, up to 25 m for large aircraft. The hangar door header alone can represent 15% of total tonnage.

Main frames: portal vs. truss

For spans up to ~40 m, a portal frame with tapered haunches is usually the most efficient solution. Above 40 m, lattice trusses become more steel-efficient — they trade depth for weight, accepting a deeper roof in exchange for less steel.

The hangar door problem

A wide hangar door means the front column line is interrupted. Loads from the roof must transfer to columns at the corners, then down to the foundations. Common solutions:

  • Door-header truss: a deep truss above the opening that spans the full hangar width
  • Cable-stayed front: for very wide openings, a cable system reduces deflection
  • Sliding-leaf door: the door panels themselves contribute stiffness when closed

Bracing: the unglamorous half of the work

Bracing systems handle wind, seismic and stability loads. In a hangar, bracing must work around the door opening:

  • Diagonal X-bracing in the rear gable and side walls
  • Horizontal bracing in the roof to transfer wind to the gables
  • Plumbing bracing (temporary diagonal members during erection)

Foundations

Hangars exert two design-driving foundation forces: vertical column reactions (often 800–2,500 kN per column) and horizontal thrust at portal-frame bases. Tie beams running through the hangar floor often handle the thrust, allowing simpler pad foundations.

Roof drainage

A hangar roof of 1,500 m² generates significant rainwater. Slope is typically 1.5–3%. Internal valleys and external gutters must handle peak storm loads — a 50 mm/hour storm on 1,500 m² is 1,250 L/min. Roof slope is also driven by snow load — flat roofs need to be designed for full undrifted snow.

Fire and lightning

Aircraft hangars carry a fire risk class higher than typical industrial buildings (fuel + composite materials). Foam suppression, smoke vents and lightning protection are usually required.

An Afcel example

The Aselsan helicopter hangar in Akyurt, Ankara: 900 t of steel, 30 m clear span, 12 m to underside of trusses, designed to a Defence Industry security specification with redundant load paths and a high-snow combination case. Erected in 11 weeks with zero major H&S incidents.