This paper presents a performance driven computational design methodology through introducing a case on parametric structural design. The paper describes the process of design technology development and frames a design methodology through which engineering, -in this case structural- aspects of architectural design could become more understandable, traceable and implementable by designers for dynamic and valid performance measurements and estimations. The research further embeds and customizes the process of topology optimization for specific design problems, in this case applied to the design of truss structures, for testing how the discretized results of Finite Elements Analysis in topology optimization can become the inputs for designing optimal trussed beams or cantilevers alternatives. The procedures of design information exchange between generative, simulative and evaluative modules for approaching the abovementioned engineering and design deliverables are developed and discussed in this paper.