Repair of prestressed (post-tensioned) concrete beams after damage by fire

In a number of structural engineering applications use is made of high tensile steel cables for load carrying purposes, e.g. suspension bridges, guyed masts, overhead electric lines and cableways. In many of these applications the cable is uniformly loaded and hence hangs in a catenary. When a structure incorporating one of these elements has to be analysed difficulties are encountered due to the non-linear response of a catenary to applied loading. This paper gives graphical and analytical data together with the linearized stiffness matrix for a catenary element which enable speedy calculations to be made. The application of this to the analysis of an electric line river crossing is given. T. J. POSKITT

The aim of this paper is to introduce a simplified method for the structural analysis of rigid plane and space frames, based on principles which are well known to structural engineers and which do not involve serious mathematics. The derivation of formulae is based on the concept that when a member, continuous over several rigid joints or supports, is cut at any of its joints, the equilibrium of the two portions of the structure is unaltered if the slopes at the section cut are preserved. Thus, either its left-hand or its righthand portion can be replaced by any such torsional or flexural member that fulfils this requirement. This substitute member is said to have the equivalent stiffness of the portion of the structure which it replaces as it exerts the same effect on the remaining portion of the structure as the part removed. This concept leads to the development of a method of transforming a complicated plane or space frame having mutually perpendicular members into a much simpler type of plane structure for analysis. L.K. Chen and K.C. Wong

The President, recalling the author’s reference to the cost of 20-storey tenements in Hong Kong as being 7 1/2d. per cubic foot for the structure or 9d. per cubic foot including foundations, asked whathe cost in Hong Kong of flats or other dwellings comparable with similar buildings in this country was.