Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Test of time


Francis Walley (NCE 9 September) expresses surprise that WSP could not use aircraft pavement branch data on pavement deflections under aircraft. I am unaware of measurements of deflections under actual aircraft, but from 1948 to 1987 the standard pavement evaluation method was a plate bearing test, usually with the 70t Plate Bearing Test rig.

Originally the rigid pavement test did not measure deflection under the plate. In 1982 we introduced a new test, linked to A Guide to Airfield Pavement Design and Evaluation (PSA, 1989), that did.

The deflection measurements were compromised by use of a rubber mat, and the stiffness of the plate altered deflections compared to a tyre. Both tests measured failure loads, and not the pavement parameters needed to correlate calculated deflection to load.

Plate Bearing Test data therefore gave limited information on real deflections under actual aircraft. No testing was carried out on slabs cracked into crack and seat patterns.

I operated the rig from 1982 to 1987, and still mourn the passing of a historic piece of equipment, and the records lost on privatisation of PSA, but I don't miss nights working under an old tank transporter in sub-zero temperatures and gale force winds.

Graham Woodman, senior technical director, WSP, graham. woodman@wspgroup.


Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.