Glulam is making its way from buildings to bridges, becoming a cost-effective, viable and sustainable alternative to steel and concrete, according to research out of South Dakota State University in the US.
Researchers at the university’s J Lohr Structures Lab tested the strength of a glulam bridge as part of a push to give counties and towns more options when designing new bridges or replacing old ones.
“To our knowledge, this is the first time that full-scale testing has been done on glulam timber bridges,” co-principal investigator Mostafa Tazarv said.
Bridges on low-traffic county and township roads must be strong enough to withstand great weight – enough to support the typical 15 fully loaded trucks per day that cross these roads, Dr Tazarv said.
To prove the glulam bridge’s reliability and strength, the researchers applied a 32-kip – or about a 14,500 kilogram-force – load to the middle of the tester bridge, approximately equal to one lane of traffic, at a rate of one load a second.
“This ages the bridge in a short period of time,” Dr Tazarv said.
“The bridge withstood half a million load cycles, which equates to 90 years of service.”
Glulam construction costs can also be anywhere from 25 to 50 per cent less than conventional bridges, he said. As well, they can be installed in a day without specialised equipment or trained personnel.
A sustainable alternative, glulam has low levels of formaldehyde and can be reused to make longer pieces of straight or curved timber.
The engineered timber material, made by clamping together layers of wood with glue, originated in Germany in the 1900s and adopted by Australia in the 1950s, however it has not reached the same level of popularity as in Europe and North America.
The annual glulam consumption in Australia is approximately 30,000 cubic metres, which is only 0.6 per cent of Australia’s total timber consumption, according to the Glued Laminated Timber Association of Australia.