Edinburgh Napier University

  Wavin Industrial Products Limited arranged access in conjunction with Balfour Beatty Construction Limited and Bovis Construction Limited to the Braehead construction site, near Glasgow, to test a mixture of smooth bore and corrugated utility ducts in situ . Samples of all ducts were then parallel plate compression tested to BS EN 50086. Results of all site tests are presented with cumulative frequency charts showing the likelihood of a duct failing. Detailed analysis and discussion of the test results from site then follow. Key points arising from the field deformation measurements were: the stiffest ducts performed well; at no point did the vertical diametral strain exceed 5·3%. This indicated both good-quality duct and good-quality installation. Comparisons are drawn with other types of duct and the cumulative frequency plots revealed that duct stiffness played a major role in ensuring satisfactory performance. The vertical diametral strains are categorized with pass/fail decisions attached to each category. This paper casts doubt on the 450 N limiting force at 5% vertical diametral strain; the authors feel it is too low and that 700 kPa is a more suitable minimum specific stiffness. This was supported by a plot of failure probability against average specific stiffness from four different ducts tested in situ over the last five years.