The Chairman I would like to make a first comment, if I may. Mr Hume emphasised, quite rightly, the question of loadings that are being used for modern design, and how difficult it is sometimes to relate these loadings to current standards. I think it is relevant not just for old buildings, but for any building.
An investigation into the specification and achievement of cover to reinforcement on 25 construction sites is reported. It was that the specified cover was not achieved at a significant number of locations on each site. The reasons for this were found to include a complex of factors such as poor workmanship, unbuildable designs and detailing, poor communication, and of coordination. In turn, such factors were traced to contractual terms and conditions and a harsh economic climate which do foster collaboration. The implications of these findings are discussed. Professor L.A. Clark, M.G.K. Shammas-Toma, D.E. Seymour, P.F. Pallett and B.K. Marsh
A large amount of work has in recent years been devoted to the study of the behaviour of single-span masonry arch bridges. Despite the large numbers of multispan bridges in this country and abroad, much less attention has been aforded them. This paper describes a programme of tests on three large-scale model multispan brickwork arch bridges, constructed in the laboratory. In the case of each bridge, when tested to collapse, it was found that one or more of the spans adjacent to the loaded span were involved in the failure mechanism. It was also found that the critical loading position was not at quarter span, but closer to the crown. The presence of attached spandrel walls had a significant influence on the behaviour and strength of the bridges. The experimental results are found to compare reasonably well with theoretical predictions using a rigid block (mechanism) method of analysis, especially when spandrel walls are included in the calculations. Professor C. Melbourne, M. Gilbert and M. Wagstaff