A Rule-Based Program to Construct an Influence Line for a Statically-Determinate Multi-Span Beam Structure

Abstract

The form of any influence line for an internal or external force present in a statically-determinate multi-span beam structure is based entirely on straight lines. An engineer can readily draw such influence lines by following a few simple rules of procedure. The program presented in this paper emulates this procedure by using a Production System, a classic technique of Artificial Intelligence programming.

The struc ture is represented by a string of symbol seach symbol corresponding to a certain type of node; this string forms the data-base. Rules of the form, LHS implies RHS are present in the knowledge-base, and have their analogue in the geometrical properties of the influence line. The LHS of each rule is matched, if possible, by the interpreter against the literals of the data-base; if the match succeeds, then the RHS of the successful rule deposits the y ordinate(s) of the influence line into the data-base.

At the end of the matching process, the data-base contains information about the (x,y) co-ordinates of the change points of the influence line, which may then be plotted by connecting each pair of (x,y) co-ordinates.