TR063: QSTRUC: An Approach for Qualitative Structural Analysis

Understanding the behavior of a structure and its components in the preliminary design phase can have a significant effect on the quality of the final design. Accurate prediction of the behavior of a structure can reduce the number of alternative solutions and avoid costly design revisions. However, there are few tools available for modeling and qualitatively analyzing a structure.

This report describes a system, QStruc, for qualitative structural analysis which combines first principles in structural engineering and experiential knowledge of structural behavior. The purposes of QStruc are (1) to generate qualitative models from the schematics of a structure, and (2) to infer the qualitative response of the structure in terms of deflected shape, moments, and reactions. The framework consists of two main modules: the model generation module and the qualitative analysis module. The proposed qualitative analysis strategy is a "greedy," depth-first approach that tries to expand the derived response as much as possible from known parameter values. The system makes use of:

• Causal ordering mechanism, that enables the system to identify the solution path for the qualitative analysis. A causal model is used to describe the behavior of a structure in terms of physical quantities and causal interactions among them.

• Qualitative calculus, which enables the qualitative evaluation of the physical quantities of the causal model that describes the behavior of the structure.

• Quantity Lattice [7], which enables the system to reason about partial ordering among physical quantities and to reduce some of the ambiguous conclusions caused by the impreciseness of the information.

The report discusses the following aspects of QStruc: (1) representation of the physical model, fundamental principles, and experiential knowledge, (2) model generation, and (3) qualitative analysis. We provide a simple example to illustrate the operations of the prototype system QStruc. The report concludes by summarizing our preliminary findings and suggesting directions for future research.