The design of continuous reinforced concrete slabs is a routine item-moments are taken from CP114 Table 15 or CP110 Table 4 (according to taste), reinforcement is calculated and it is then placed according to normal detailing practice: it is customary to stop off top reinforcement at 0.25 L or 0.3 L from a support (L = span). Yet, as Beeby has pointed out in a recent paper3, this situation contains a paradox. Both Codes specify similar theoretical rules for curtailing reinforcement-e.g. CPllO cl. 3.11.7.1: ‘ . . . every bar should extend, except at end supports, beyond the point at which it is no longer needed for a distance equal to the effective depth of the member, or twelve times the size of the bar, whichever is greater. . . ’. A.N. Beal
Damage to property may occur when high explosives are used for mining, quarrying or civil engineering operations or may arise from acts of terrorism. Claims for compensation are often exaggerated or comprise allegations of damage where defects are due to other causes, such as thermal or moisture variations in the building materials or settlement of foundations. J.D. McCaughey
Mr G. M. Pinfold (F) (NCL Consulting Engineers): First, I should like to say how interesting the paper was, particularly in the treatment of structural arrangements not normally considered as being wind-sensitive.
Mr M. Shears (Ove Arup & Partners): The author is to be congratulated on giving us such a comprehensive description of this interesting and unusual structure.
Lateral restraint for cold-formed purlins A number of our readers have written to us seeking, or providing, advice on the effectiveness of lateral restraint for purlins in lightweight steel roofing systems, since Mr L. Wadsworth first raised the problems of design in April 1983. Further information is now provided by Dr. S. J. Bates who writes on behalf of his firm as follows: As the largest UK manufacturer of cold-formed purlins, selling systems which have been independently designed and tested at the country’s foremost universities, specialising in the design of cold-formed sections, we have always taken a pride in our ability to offer a technical backup service to deal with specific inquiries. Perhaps the time has now come to offer a general discussion on points raised in open forum, although we would emphasise that specific questions should always be dealt with on an individual basis and we are always willing to discuss particular applications with individual engineers. Verulam