TR031: A Formal Approach to Automating Conceptual Structural Design

In the conceptual phase of structural design, a designer develops and investigates many potential alternatives for safe and economic transfer of loads that are to be carried by the structure. A methodology for automating conceptual structural design and an application of the methodology to a specific problem are presented in this report. Some of the salient aspects of the methodology are: (i) an explicit representation of the structural form, function, and behavior; (ii) modeling the structural engineering domain as well as the strategy employed by expert designers; (iii) using Cost/Value ratio as an intrinsic measure of the merit of a design alternative; and (iv) reduced reliance on heuristics with more emphasis on first principles and fundamental knowledge. The categories of knowledge that need to be represented in a computer system to support the reasoning for conceptual structural design are identified. The use of such knowledge is illustrated through examples based on several different types of structures. A constraint classification system (to organize the constraints that arise from structural and exogenous considerations) is also proposed.

The abovementioned methodology is applied in the context of the problem 01 floor framing generation for steel office buildings. Floor framing generation involves providing a path to transfer the gravity loads incident upon the structure from their points of origin to the ground. This is achieved by placing various structural elements in an architectural plan, while meeting the requirements imposed by other entities (such as the architect, the mechanical engineer, and the contractor) involved in the design/construct process. We describe the knowledge and the reasoning behind a computer system, FFG (for Floor Framing Generator), which generates floor framing schemes for steel office buildings that are rectangular in plan and have a single service core. Constraints arising from structural as well as exogenous considerations are enumerated and their effects on the framing schemes are identified. We also elaborate on the evaluation mechanism for ranking alternative schemes, in addition to providing details of the computer implementation.