What are the main types of bridges?
Beam, truss, arch, suspension, cable-stayed and cantilever bridges explained simply, with how each carries load and which ones suit a balsa contest.
Updated · 1 min read
Short answer: the main types are beam, truss, arch, suspension, cable-stayed and cantilever. They differ in how they carry load to the supports. Student balsa contests almost always use a truss.
| Type | How it carries load | Typical use |
|---|---|---|
| Beam | The whole deck bends, with the top squeezed and the bottom stretched | Short spans, such as a plank over a stream |
| Truss | Straight members in triangles, each pushed or pulled | Medium spans, railways, roofs, model contests |
| Arch | A curve that carries load mostly in compression and pushes outward at its feet | Stone and concrete bridges, some long spans |
| Suspension | The deck hangs from cables over tall towers, and the cables are in tension | Very long spans |
| Cable-stayed | The deck is held by cables running straight to a tower | Long spans |
| Cantilever | Arms stick out from supports and carry load in bending | Some long steel bridges, and balanced construction |
Which suits a balsa contest?
A truss is the usual choice, because it is light, uses straight sticks and is easy to build with hobby tools. See truss basics and how a truss works. An arch is possible but harder. Suspension and cable-stayed bridges need strong tension cables and tall towers, which most contests don't allow.
Always check what your rulebook allows. See reading your rulebook.