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The Structural Engineer

Mr A. N. Beal (M): It is surely a little optimistic to assume that restrictions on time of day for movement of unusual loads will have an ‘insignificant’ effect on their probability of combination with temperature differences (p179). Indeed, it is likely that correlations with time of day-and time of year-will have a dramatic effect on any calculated probabilities and that the figures quoted in the paper can be regarded only as approximate in the extreme. However, in considering the problems of combined temperature and vehicle loading, there are non-probabilistic questions to ask-and these may be more important. In particular, it should be remembered that temperature stresses arise from imposed deformations, whereas live and dead load stresses arise from imposed loads. The distinction is important because one is relieved by the onset of yielding, whereas, for the other, yielding leads to failure. Thus while temperature changes may lead to high calculated stresses, these are quite different in nature to, and much less worrying than, stresses due to applied loads-and this, rather than assumed probabilities of joint occurrence, may be the true reason for the satisfactory performance of bridges designed to pre-1973 rules. Mr J. Wheeler (Main Roads Department, Perth, Western Australia):

The Structural Engineer

This paper describes the design of an office block over Fenchurch Street Station in the City of London. The way in which the design was developed over a number of years is emphasised. Special considerations involved in building over a station are outlined. The alternative structural forms considered for the office block and the reasons for the adoption of a design in which most of the building spans nearly 30 m across the station are described. A detailed description of the design of 2.5-3.5 m diameter hand-dug piles and of the analysis of the interaction of these piles with 4m-deep transfer beams is given. R.F. Jacobs, S.C. Smith and E.H.F. Taylor

The Structural Engineer

There is an increasing trend towards the refurbishment of existing buildings, many of which contain large numbers of cast-iron columns and beams. Very few data, however, have been published on methods of predicting the fire performance of cast-iron structural elements. This paper deals with the factors affecting the performance of cast iron in fire and proposes fire design parameters for use when refurbishing existing buildings containing structural cast-iron that is required to meet current Fire Regulations. J.R. Barnfield and A.M. Porter

The Structural Engineer

The new regulations, extensively discussed by the industry and masterminded by the Department of Environment, are now reaching the final stage of their review. They cover both the requirements of the Building Regulations and proposed methods of control. The review was started by a study in depth, by the Department and its consultants. This led to discussions and discussion drafts, prepared by the Department, which have gradually hardened into Acts of Parliament and of Statutory Instruments to go before Parliament. Inevitably, this process brings compromise between the ideals of the profession and what Parliament believes to be necessary to safeguard the public. Also it is still incomplete and includes recommendations that engineers may wish to see changed. S.B. Tietz

The Structural Engineer

Computer design programs During recent months, we have published correspondence from readers on the use of computers in engineering. We are now very pleased to have heard from Mr M. Bowden, writing from Bromley, on his experience of using a microcomputer in his practice. He writes: I read with interest your appeal in the July issue for ready-made programs which could be of use to other engineers. I was surprised to note in the August issue that only one such program had been received. Verulam