Issue 13

Slender space structures covering large areas can suffer from excessive deflections. In this paper a simple but exact method is given for the design of such structures. This calculates the cross-sectional areas of members so that recent limit state design requirements for strength, well as deflections, are fully satisfied. The method does not depend on analysis of the structure with preselected sections and thus removes need for the explicit solution of a large number of simultaneous stiffness equations. In this manner it saves considerable computer time. Instead proportions the members in the most economic manner and calculates their unknown areas. A design procedure is given so that all the recent BSI recommendations for the limit state design of steel structures satisfied. The results of an investigation into the design of space structures are then reported, in conjunction with a number of practical examples. K.I. Majid and S.Okdeh

The pitched roof portal building is of considerable economic importance in industry, and it is sometimes necessary to calculate natural frequencies of vibration to determine the response of such structures to vibrating machinery or to environmental forces such as dynamic wind forces. Professor A. Bolton

The effect of elevated temperatures on the strength and stiffness properties of four reinforcing and three prestressing steels of varying size, manufactured to British Standard specifications, has been investigated. To simulate the temperatures likely to be experienced by the steel during a fire, a temperature range of 20° to 700° was adopted. The steels were tested in their 'as manufactured' condition in a purpose-built, tensile testing machine with tube furnaces and associated recording instrumentation. The test programme was designed to provide data on three major strength parameters-yield (or 0.2 % proof) stress, ultimate strength, and elastic modulus. Using the datu it is possible to assess the deterioration in strength of a structure during a fire and its residual strength at ambient temperature after a fire. M. Holmes, R.D. Anchor, G.M.E. Cook and R.N. Crook