Lab Based Structural Appraisal of Vacuum Pressed CLT Panels & GLT Beams

 

Previous tests performed on UK homegrown CLT, GLT and NLT were undertaken on panels and beams manufactured using mechanical/ hydraulic presses. For this reason, the project sought to increase the data available by carrying out further testing on homegrown CLT and GLT panels manufactured using the UK’s only commercial-scale vacuum press at the Construction Scotland Innovation Centre. Additional tests were also undertaken on NLT panels, manufactured for the first time using homegrown timber and hardwood (beech) timber nails. 

Edinburgh Napier University’s (ENU) Centre for Offsite Construction + Innovative Structures (COCIS) was commissioned to undertake a series of structural tests on behalf of Transforming Timber project partner ECOSystems Technologies. This was to ensure that computer modelling and structural calculations aligned with actual performance data generated through the test programme.

The table below details the test programme developed in accordance with BS EN 16351 and designed to determine key mechanical properties of all homegrown mass timber systems currently being manufactured in Scotland, including CLT and GLT manufactured using CSIC’s vacuum press.


Principle Outputs

  • The production process was set-up to directly replicate full-scale commercial production process, currently implemented by ECOSystems Technologies at CSIC’s Innovation Factory

  • A total of 30no. mass timber panel were manufactured for the purpose of the testing (4xCLT, 14xGLT and 12xNLT)

  • The results from preliminary tests (acoustic characterisation of the boards used for mass timber manufacture) are based on a total of 167 boards with nominal dimensions of 40x145x4800 mm

  • The properties of boards used for CLT, GLT and NLT production were of good quality, slightly exceeding characteristic properties of C16 strength graded timber

Conclusion

Results from preliminary test work (acoustic characterisation) confirmed that the raw material supplied by sawmilling partners BSW Group was sufficiently dried and of satisfactory quality. Based on the results, the stiffness of beams evaluated in this test programme slightly exceeded the stiffness of C16 Timber strength class.

Based on the results from full scale panel testing, all mass timber systems (CLT, GLT and NLT) performed well under severe stress conditions, exhibiting minimum line failures, which can often indicate issues with bond integrity. Test evidence suggests that the manufacturing process adopted by ECOSystems Technologies at CSIC Innovation Factory are appropriate and that products manufactured by the organisation are suitable for use in appropriate scenarios within construction.

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