Evaluation is a key task in design, and a major goal in research on computational design is to develop techniques for evaluating design concepts throughout the design process, starting as early as possible. Conceptual design in engineering is abstracted as a function-to-structure mapping and engages the use of functional models of design candidates. This suggests functional model simulation as a method for early evaluation of these alternatives. We describe a computational technique that evaluates such candidates in the conceptual phase through simulation of hierarchically organized Structure-Behavior-Function models. We demonstrate the capabilities of our technique for evaluation in biologically inspired system design that uses biological analogues to address design problems.