PRAXIS: A Program for Reproducing Proforma Design Calculations

PRAXIS embodies a computer language for reproducing design calculations in a paginated and tidy layout suitable for submission to a checking authority. Some calculations reproduced by PRAXIS are illustrated in Fig. 1. From the calculations alone it would be impossible to tell whether the page came from a typewriter (being copied from a designer's hand-written calculations) or from a computer, because the calculation is self-descriptive. Every line is checkable. Every formula is shown in symbolic form before specific values are substituted. The only thing suggesting the involvement of a computer is the consistent neatness, and absence of arithmetical mistakes. Although Fig. 1 shows a calculation for a brick wall, PRAXIS itself knows nothing about walls; it is independent of any particular engineering discipline. In order to reproduce calculations for a wall PRAXIS must be given a 'proforma' calculation for a wall. Such a proforma is shown in Fig. 2. This is the proforma from which the calculations shown in Fig. 1 were generated. The proforma corresponds directly to the finished calculations, groups of question marks in the proforma being replaced by parameters of a particular wall. The function of PRAXIS is to substitute these parameters, then resolve arithmetically the expressions in the proforma which were given algebraically. Fig. 3a illustrates another proforma, details of which are explained more fully later in this paper. The resulting set of calculations in Fig. 3c shows extra lines generated from those in the proforma. Nevertheless the calculations in Fig. 3c remain self-descriptive and not evidently the product of a computer program. During the last twenty-five years many design programs have been written to produce, as a by-product, calculations similar to those illustrated in Figs 1 and 3c. But these programs were written specifically to design beams or slabs or whatever the structural entities concerned. PRAXIS is a program which knows nothing about beams or slabs; such knowledge is embodied only in the proforma. Thus the proforma is analogous to a computer program for which PRAXIS is the interpreter (or processor). In this respect PRAXIS offers a novel approach to the reproduction of . designers' calculations at least as far as the authors are aware. A proforma, being analogous to a computer program, need be composed only once for each problem. When a satisfactory proforma has been developed for the design of a rectangular column, say, then that proforma may be stored on disc to be recalled whenever a rectangular column is to be designed. An ever-growing library of proformas may be stored on disc in this way. The rest of this paper explains the principles of processing a proforma, concentrates on certain features of the 'language' in which proformas are composed and describes the operation of PRAXIS on a computer. Finally this paper discusses the current scope and possible future of PRAXIS in structural engineering.