Issue 6

I read with interest the paper 'Natural frequencies of structures for designers'. Professor Bolton has shown that, with his approximate method, the natural frequencies of multistorey frames can be obtained within 3.3% accuracy. I have solved a three-bay, twostorey frame (which was also solved by Armstrong) using the method proposed by Professor Bolton. The calculations for this frame are given below: N. Subramanian

Mr. A. C. Paterson: As the demand for cooling water for power generation and for industrial and chemical processes grew towards the end of the last century, a point was reached when there were no longer sufficient supplies from rivers and lakes, and it had to be accepted that the same water would have to be used over and over again.

President's Diary The President and Mrs. Harris have now completed most of their visits to the Institution Branches in the UK and Ireland, and have asked that their thanks be offered to Branch Committees and members generally-and their ladies-for the many kindnesses that have been extended to them everywhere.

This paper describes the construction and testing of a one-eighth scale concrete model of a bridge abutment with wing walls cantilevered from large torsion blocks. The model strains at working loads are compared with those predicted by traditional and computer methods of analysis. The mudel performed satisfactorily up to ultimate load, but failure of the wing walls was sudden owing to longitudinal tensile cracking in the string course. P. Lindsell and A. El-Dharat

Fortunately, we are still living in an era in which timber, that is to say sawn timber, is readily available as a structural material and, over the years, continued research, backed by traditional experience, has allowed it to be used with increasing confidence and efficiency in a wide range of structures. Techniques of stress grading, based on visual inspection and on non-destructive testing, are available to enable the timber used to be adequately controlled as regards strength. More recently, a new generation of timber-based products, involving some manufacturing or processing, is being presented for evaluation and use as a structural material. These products may or may not possess properties that reflect those of timber, and their evaluation does present problems. J.W.W. Morgan

This paper is a summary of the law affecting structural engineers. It outlines the extent of the structural engineer's duties to his client and to third parties when advising, designing, supervising, and certifying. Copyright, property in plans and specifications, the special position of local authorities, and the structural engineer's responsibility for his partners and employees are reviewed. Recent developments in the law are emphasised, and the underlying trends discussed, including relevant aspects of the Misrepresentation Act 1967, the Defective Premises Act 1972, and the Unfair Contract Terms Act 1977. The paper states the law as at August 1978. Christopher Lewsley

A question of responsibility The problems of working in a team with other and independent professionals are ever with us; Mr. D. G. McBeth writes on the question of responsibility in such a situation: The majority of contracts upon which I am engaged are being run under the RIBA conditions of contract. I have long been concerned about the position of the structural engineer, in that we are not legally part of the contract. Although we may be mentioned in the bills (but even this is not necessarily the case) all reference to the 'engineer' in specifications is usually deleted in favour of the 'architect', who is, therefore, 'responsible' for approving concrete mix designs, checking steel fabrication drawings, trussed rafter workshop drawings, etc. Verulam