This paper reviews the problems of durability and maintenance from two aspects. In the first part the size of the problem, recent developments and techniques for calculating the effects of design decisions are discussed. In the second part, the factors on which structural engineers must base their decisions on durability are examined for four particular problems: concrete in sulphate-bearing soils; steel reinforcement in concrete; the avoidance of inorganic ' growth ' on concrete; and the uses of corrosion resistant metals. T. O'Brien
Mr. Colbridge (British Iron and Steel Federation) : ' I should firstly like to congratulate the authors on their paper, which describes a number of innovations of an extremely interesting character. The Drapers' Gardens Development is also an example of the growing interest in structures that combine both structural steel and structural concrete in an overall design concept. A number of buildings designed on this principle can now be found both in this country and abroad, and there is no doubt that it is a trend which will continue as new solutions are developed for the integration of the two media. '
The paper describes the design and construction of the new Horseferry Road Government Office block. It discusses the influence of the existing heavily constructed RC structures in determining the layout of the scheme; the design aims in the selection of a building system and the development of the Ministry's BP Frame; the use of burster reinforcement at the ends of columns in lieu of lapping continuity column steel, together with a brief report on short column tests: the recommendation to use helical coils in preference to stirrups; the advantages of precasting individual components versus built-up frames. The general stability of industrial building systems is discussed with its limitations in strength arising from pin-ended connections, erection techniques and erection dangers. The basement is constructed with the use of precast waffles, and tests on their strength are described. Fire requirements and winter working precautions are briefly mentioned. The problem of differential settlement on a difficult site is described together with the methods used to reduce its effect. H.E. Mills
Mr. Brian Scruby : 'I would like to hear more about the application of a calculated displacement at the head of the column and how this was applied. I would also like to know exactly what happens if unfortunately a vessel hits one of the piers. This was partly explained in the paper and the authors have referred to it in their presentation.'