Discussion on Brick Diaphragm Walls-Development, Application, Design, and Future Development by W.G.

Mr C. W. Brown (Freeman Fox & Partners): I should like to congratulate the authors on their most refreshing approach to the design of the structures in question and on not being tied up in all the advanced mathematics that one is apt to meet these days. They have a fairly simple extension to BS 153. I do notice, however, that shear lag has appeared in the paper; what were the shear lag factors actually used for? Did the authors calculate the peak stresses in their box girders and compare these with allowable stresses, or did they use shear lag purely for fatigue analysis-or what? I should have thought that, from the proportions of the ramps, shear lag would not play a very large part in overall behaviour.

Dance halls A collapse this year in America has highlighted the problem of rhythmic loading on the floors of dance halls, and we have received the following letter from Mr W. G. Scott (of Lothian Regional Council) who was involved in some of the problems at Edinburgh Playhouse. Verulam

A number of inconsistencies in the approaches given in British Codes for the design of reinforced concrete slabs are discussed. These are cases where a more rigorous design leads to a requirement for more reinforcement than do simplified methods. Since experience suggests that the simplified methods are adequate, a review of the bases of slab design seems necessary. Various aspects of the behaviour of slab systems are discussed including the nature of loading and membraneffects. It is suggested that the more rigorous design methods are indeed overconservative, and a change in the design load patterns is proposed. A.W. Beeby