An Innovative Approach Towards Designer-Orientated CAD Systems

I was extremely interested in the ‘viewpoint’ by D. Goodger published in The Structural Engineer, 3 March 1992, as this is a subject that has much occupied my thoughts over the last few years. B.J. Shaw

This paper examines the design methods for providing resistance against punching shear, generally concerning the strength requirement for transfer of the load from a flat slab to the supporting column or from a column to its base. The BSI committee B/525/2 (CSB39 as it was then called) had expressed concern about the present design method given in BS 8110: Part 1 : 1985 for providing resistance against punching shear in reinforced concrete slabs. As a result, an examination was carried out, based on a test programme funded jointly by the Department of Environment and the British Cement Association (BCA). The conclusions of this examination have assisted in reviewing the punching shear clauses given in BS 8110: Part 1: 1985*. The results of this exercise have also been used for recommending a revision to the clauses given in the Eurocode 'DD ENV 1992-1-1: 1992 Eurocode 2: Design of Concrete Structures Part I (General rules and rules for buildings)'. This BSI document is expected to be available soon, and it will include a National Application Document providing in formation and additional recommendations necessary for its use in the UK during its prestandard (ENV) stage. P.S. Chana and S.B. Desai

Dr D. Johnson (M) (Nottingham Polytechnic) The author has presented an interesting spreadsheet application in tackling the torsion problem by the stress function formulation, using the finite difference method. While agreeing that such an approach has the attraction of simplicity, it should perhaps be recognised that it also has some limitations. Box and other 'multiply-closed' sections, for instance, are cumbersome to analyse by a stress function formulation and are more conveniently analysed by the use of a warping function. It may also be argued that it is desirable to produce solutions by both warping and stress function based approaches so that upper and lower bounds on the torsional stiffness are obtained, so minimising the need for successively refined analyses. Unfortunately, the warping function approach is much less amenable to finite difference modelling, although either function may be readily used with the finite element method, which would appear to be more versatile in this respect.