SNOB is a smaU CA D system, developed for the statical analysis and partial design of buildings of cross-wall construction. It is particularly suited for the design of large precast panel blocks of flats. This paper is a case study of its development, during which great attention was paid to controlled growth, user comfort, effectiveness and economy.
computer-aided design, architectural design, flats
The origins of SNOB can be traced to a short program for the statical analysis of walls with rows of openings, subjected to horizontal loads. This program was based on Rosman's method. It was sponsored by the Design and Research Centre for Housing and Public Utility Buildings and was thoroughly tested and recommended for use in the standard for buildings of load-bearing wall construction. The program was of a general nature and applicable to in situ or precast walls. It was written in Algol for an ODRA 1204 mini with core memory of 16 k 24-bit words. No use was made of external memory. Structures with up to 30 rows of openings could be analysed in 1-3 rain on this relatively slow computer. The merits and limitations of this statics program are detailed below.
By the time the program became widely used (in 1975 it was installed in 14 computing centres), a practice had developed in the design offices dealing with large panel building systems, whereby the results of computer analyses of a structure subjected to wind load were inserted in a few columns of a large table, the remainder being filled in by hand mostly with the help of nomograms. The nomograms enabled the vertical loads per unit length of a wall due to self weight and superimposed loads, to be calculated depending on the number of storeys and wall spacing. A further nomogram was used to calculate the width and the reinforcement in the footings, depending on the load, foundation depth and the properties of the soil. All this was included in the program by the end of 1975, requiring the splitting of the original statics program into four overlays, separation of input and output modules as well as the addition of four new modules.
With all the inner forces computed, the main burden on the structural designer was the evaluation of the bearing capacity of walls (and horizontal and vertical joints, where applicable) in order to obtain the factors of safety.
This fairly involved calculation (in the case of large panel buildings) was of a different character than the statical analysis and was specific for a given construction system. (The details are discussed below.) It was included as two additional modules and the entire program chain was