The critical design decisions in bridge design are made at the prelimi
nary design stage. They depend on the expertise of the designer, built
up from extensive experience. Experience is difficult to acquire, and
may be entirely lacking when new technology is introduced. As a resul
t, there is little shareable and transferable collective design knowle
dge within the profession. This paper explores how preliminary design
knowledge may be generated, updated, and used, employing techniques of
machine learning from the field of artificial intelligence. A model o
f the preliminary design process is first presented as a sequence of f
ive tasks and then specialized to the design of cable-stayed bridges.
A computer tool serving as a design support system is described, whose
design follows the model of the preliminary design process, and a des
ign example using the tool is presented. The key property of the syste
m is its adaptive nature: it acquires knowledge from information on ex
isting bridges as well as from designs generated with the system, ther
eby continuously improving its performance. Future enhancements to the
tool breadth and depth are offered.