In this construction the beam is not a single unit laid on an abutment at each end. Two beams are used, each fixed at one end with the other projecting over the stream that is to be spanned. The two beams meet each other and are bolted together, or for longer spans the central gap can be infilled with a short beam. The cantilever beams have to be made of stiff material and strongly anchored to bear the weight. This essential requirement can make this type of construction awkward to use. However, it has the advantage that two short beams can be used instead of one long beam, which might not be available.
Arches
Arches have been traditionally used in many places. Old stone arch bridges designed for use by packhorses and dating back centuries can be found in many remote areas. They need special skills for construction, and these are unlikely to be found nowadays. However, wooden arch constructions can be used. Similar in many ways to the trussed beam construction described above, an arch of timber latticework can form an inherently strong structure using small-dimension components, and can be erected on site. Laminated timber beams can also be fabricated into curving sections resembling arches.
