Structural design language and a knowledge-based expert system for design of steel building structures

The primary goal of this dissertation was to develop a knowledge-based approach and a new computer program architecture for detailed design of structures in a declarative symbolic language. In order to investigate the practicality of the symbolic language LISP, a small experimental expert system was first developed for design of stiffened steel plate girders, called SSPG, based on the American Institute of Steel Construction specification. SSPG was implemented in a dialect of LISP, called ELISP, on a DEC-2060 machine.;After experimenting with ELISP, a decision was made to use INTERLISP which seems to be the most highly developed implementation of LISP. LISP in general and INTERLISP in particular have been developed primarily for symbolic processing. INTERLISP does not readily have all the built-in procedures necessary for numerical processing. Therefore, to facilitate the development of expert systems for structural design problems, a Structural Design Language (SDL) has been developed in INTERLISP environment on a Xerox AI machine. SDL contains the inference engine, explanation facility, debugging facility, and matrix manipulation functions.;Using SDL, a prototype knowledge-based system has been developed for detailed design of steel buildings consisting of moment-resisting frames, called STEELEX. STEELEX is a hybrid or coupled expert system that uses both symbolic and numeric computing techniques. It has been developed entirely in a symbolic processing language.;The explanation facility of SDL/STEELEX provides three types of explanations: WHY?, HOW?, and WHAT?. The WHY? function provides explanations about the conclusions reached by STEELEX. It finds and displays the production rules used for making a particular conclusion. The HOW? function provides deeper knowledge about the production rules displayed by the WHY? function. Finally, the WHAT? function provides explanations for the terminologies and equations used in production rules.;A multi-window graphics interface has been developed to facilitate the interaction of the user and the expert system. This graphics interface is capable of displaying both isometric and orthographic views. For isometric views, an efficient five-test algorithm has been implemented. The user can view both the three dimensional structure and moment resisting connection from various angles. The orthographic views of the moment-resisting connection consist of the front view, the side view, and the top view. These orthographic views include all the necessary dimensions and designations for building the connection.