This paper presents an account of a research project concerned with the application of artificial intelligence techniques to structural design in civil engineering. INDEX is a rule-based system for the design of industrial buildings that is being developed at the University of Edinburgh. It has a blackboard architecture and its knowledge base is organized into a hierarchy of two levels. The main focus of this paper is to summarize the implementation aspects of one of its knowledge modules, ALTSEL which is responsible for the preliminary design. The organization of knowledge inside the ALTSEL module is briefly outlined using a number of representative rules from its sub-modules. The use of the Edinburgh PROLOG Blackboard Shell in the development of INDEX is also described briefly.