Correspondence

The report analyses and tabulates the results of the investigation of 56 major fires, it considers the factors influencing fire limitation and describes each fire investigated. Copies of the Report are available from the C & CA, 52 Grosvenor Gardens, London SW1.

Introduction by Mr. Dunican: 'The design and construction of the first phase of the Stock Exchange rebuilding is in my opinion a working example of the ideas embodied in my paper, "The Art of Structural Engineering", which I presented to the Institution in March 1966. At that time I said, perhaps rather too obviously, that a structure of a building must satisfy four main conditions. It must stand up, it must be capable of being built economically and within the means available, and it must suit the building. I also quoted Eduardo Torroja, who said: "Structural design is concerned with much more than science and techniques, it is also very much concerned with art, common sense, sentiment, aptitude, and enjoyment of the task of creating opportune outlines to which scientific calculations will add finishing touches, substantiating that the structure is sound and strong in accordance with requirements."

This paper describes problems that were encountered, and solutions that were obtained, during the design and construction of foundations for a multi-storey building sited over the Mersey Tunnel in Liverpool. To ensure that the weight of the structure would not adversely affect the rock surrounding the tunnel, theoretical analyses were made to estimate existing stresses: and experiments on photo-elastic models were made to assess imposed stresses. The results showed that major loads would have to be transmitted to either side of the tunnel by air space foundations consisting of floating beams supported on end-bearing piles. A description is given of the piles and the tests which were made to develop frictionless linings. Two floating beams and a floating slab are discussed in terms of analysis by finite element techniques: and their construction in post-tensioned concrete is discussed with special reference to mix design, types of shuttering: and concreting methods. D.M. Bingham and A.J.M. Soane