A short history of harbour engineering Discussion on the paper by J. P. M. Pannell

Dear Sir, With reference to the article, ‘The elastic analysis of simple rectangular grids by virtual work methods’ by J. B. Martin, BSc, PhD, appearing in The Structural Engineer in June 1963, I would like to point out that a numerical error has been committed in the solution for the numerical example given in the article.

Mr. P. S. A. Berridge (Assistant Engineer (Bridges), Western Region, British Railways) first said how much he appreciated being allowed to join in the discussion. It was a privilege for which he was most grateful.

The paper describes the application of ultimate load design by yield line analysis in pavement slabs and confirms the finding of recent AASHO test results in regard to long-term serviceability of concrete pavements. Based on the following assumptions:- (1)strain is proportional to distance from the neutral axis in accordance with a straight line law, (2)elastic deformations are negligible in comparison with the plastic deformations (this means that the slab elements between the yield lines remain plane and all the deformations take place in the yield lines), (3) yield lines, which are straight, being the meeting lines of two planes, end at a boundary of the slab, (4)a yield line, or yield line extended, passes through the intersection of the axes of rotation of adjacent slab elements, (5)axes of rotation in general lie along the lines of supports of formulae has been developed for the design of concrete pavement. Dr. R. K. GHOSH