Partial Safety Factors for Reinforcement

The problem of occupant-induced vibrations in buildings is one of growing importance. Until recently this problem was thought to be confined to floors of timber or composite construction, but in this paper it is shown that some recently constructed concrete floors are sufficiently light and flexible to give rise to disturbing levels of vibration. Methods of designing concrete floors against occupant-induced vibrations are evaluated against an extensive programme of field tests and are found to be deficient in two respects: prediction of the free vibration characteristics of 2-way spanning floors and estimation of structural response to excitations such as walking and heel drop. Martin S. Williams and Peter Waldron

Foundations near trees The discussion on construction near trees, generated by the paper in the issue of 16 August 1994 (Building near trees - the development of NHBC standards for the foundations of low-rise dwellings) has generated divergent views from members. Should we design to prevent all visible signs of ground movement in our buildings or should the cost-effectiveness of accepting minor cracking be a more prominent consideration? To what extent would the public go along with us, bearing in mind that they are the ultimate paymasters even if insurance cover spreads the costs? With the current arguments regarding the excessive cost of construction, should we do more to influence public opinion? Verulam

I feel extraordinarily privileged to have been elected as President of Institution of Structural Engineers and to have been given the honour opportunity of addressing my fellow members on a subject that I feel special importance at this stage of our history, namely that of communication. It is important because, although our Institution promotes and, indeed, achieves excellence in structural engineering among its members, I fear we, on the whole, are much less good at communications than others that several of the ills besetting our profession can be attributed to single fact. Professor P.J. Dowling