By necessity, the character of this paper has to be rather general. Its subject is very broad, and some emphasis should be given to the physical and analytical modelling of the behaviour under seismic actions. However, because of this generality, a more complete picture of all aspects of aseismic design is needed and hence the briefness of the presentation of each aspect and the inevitable gaps in the presentation. Consequently, originality is claimed only for some of the models presented during the paper. Professor Dr. T.P. Tassios
The collapse of a factoy roof in the UK under snow loading is described. The mode of failure was repeated in a number of similar structures. As discussed in a recent BRE Digest, these failures may have been due to the increased sensitivity of certain types of structure to snow driffing. In this paper, it is shown that the failure occurred from the unintended consequences of progress in our understanding of the structural behaviour of cold formed steel purlins. Several lessons are drawn regarding the design of these elements, the role of Code recommendations, the production of ssfe load tables for design, and the need for engineers to be aware that human action can result in unintended consequences and that decisions should be taken so as to minimise their effects. N.F. Pidgeon, D.I. Blockley and B.A. Turner
This series started in January 1983 with ‘Aims of structural design’, and since then more than 25 additional ‘Viewpoints’ have been published on a varied range of topics:
Questions on cement and concrete Mr John Park, writing to us from London, makes two observations on British Standards on which he would welcome comments from our readers. These are: Firstly: BS 12 states that ordinary Portland cement shall have a minimum specific surface (fineness) of 225 m2/kg while rapid-hardening Portland cement shall have a minimum of 325 m2/kg. Cement from other countries may have values higher than this. Should they then be regarded as rapid-hardening and be rejected if OPC has been specified? What would be the effects on the structure of using higher values? Presumably early drying shrinkage will increase. What extra precautions should be taken if the contractor offers cement with a fineness of 300 m2/kg in one part of the structure and, say, 350 m2/kg in another? Should a maximum value be specified? If so, what should it be? Verulam