Stress-laminated arches: a stronger case for timber bridges

Timber bridges have been around for a long time but are still viewed with suspicion by design engineers and the public alike. Though not as durable or strong as steel and concrete, timber is nevertheless a sustainable material in plentiful supply and can be combined with other materials to make up for its structural shortcomings. ‘Stress-laminated construction’, where short planks of low-grade timber are simply bolted together to make large flat slabs, is now a primary design option for secondary road applications in the US. This paper reports on pioneering UK research which has shown such bridges can be even stronger when built with arched rather than flat decks.