Four American hardwood species have been the subject of an extensive strength testing programme by Building Research Establishment (BRE).
The aim of the tests, commissioned by the American Hardwoood Export Council (AHEC), was to provide designers with relevant strength and stiffness properties so that structural elements such as frames, load bearing interior components or roofs may be designed as efficiently as possible.
The temperate hardwoods white oak, red oak, ash and tulipwood were all tested and the results showed that all achieve significantly high levels of strength in relation to their density.
Peter Ross of engineering consultants Ove Arup has examined the data and said: ‘Tulipwood, for instance, achieves a characteristic ending strength of 42 N/mm2, almost twice the strength of a medium-strength softwood – around 24 N/mm2 – but with very little weight premium.
‘A high strength/weight ratio is in fact a general characteristic of the joinery grades of the American hardwoods.’
The design information will be made available for use in both permissible stress codes, such as BS 5268, and limit state codes, such as the new Eurocode 5.
AHEC will produce a technical publication based around the test results which will help architects and structural engineers wishing to design with American temperate hardwood species.
