Design Process Definitions Design Process

72 the design process. Markus 1969 and Maver 1970, French 1971, Pahl and Beitz 1986, Pugh and Morley 1988, Cross 1993 and Archer 1995 are just some of them in architectural and engineering design domains, who had attempted to generate standardized design procedures Austin et al., 2001. Moreover, Austin 2001 expressed that conceptual design phase of any project is a vibrant, creative and dynamic period, which can be disorganized with incomplete exchange of information between design team members. Whereas transfer of information, ideas and opinion is critical to the development of concepts, it needs to be understood and, ultimately, managed Austin, 2001. According to Fenevis et al. 2000 building design is an iterative process that follows three stages of refinement: conceptual design, preliminary design, and detailed design. He stated that conceptual design is the first stage where the most important characteristics of the building are defined. Major decisions are made regarding the building architectures and also salient features of the engineering support systems. During the conceptual phase of building design, as Fenves 2000 stated major decisions are taken regarding the building type, occupancy, form, dimensions, and type of structural system, all of which have great impact on the final form, constructability, cost, and overall performance of a building. Fenevis et al. 2000 believed that time and resources allocated to this phase are limited. Consequently, designers perform conceptual design by intuition and experience rather than by exploring the vast space of possibilities in a systematic manner Fenevis et al., 2000. 73 Wheeler unpublished, 1978 divided the life of an architectural construction project into nine major phases containing: 1 project master plan, 2 site analysis, 3 programming, 4 schematics, 5 design development, 6 construction documents, 7 bidding, 8 construction, 9 occupancy Chung, 1989. His model was presented in matrix form which depicted the project phases, steps, and activities as performed by each of the project participants such as the owner, the project manager, the design manager, the construction manager, and so on. According to Wheeler the fourth, fifth, and sixth phases cover the design stage of a project and assist the determination of many of the sub activities and outputs.

2.4.2 Design Process Models

As mentioned earlier, the concern of this study is exploring the required knowledge during conceptual design stage of a building project. Furthermore, there is a need to have a deeper inspection of design process models to be able to link the discovered knowledge to the activities of the design stage. In response to the abovementioned need, in this section we narrow down to the details of existing design process models. The design literature has produced a great variety of models of design processes, including the following list, wherein the author’s name and the principal elements of the model have been mentioned. A major source for this list was the review paper by Evbuonwan et al. 1996. We have summarized all the models in Table 2.10. 74 Marples 1960 believed that design is a sequence of decisions which start from stating requirements and ending by producing technical specifications of product. The functional specifications of decisions were represented in a tree. The Maple tree is a graphical method of recording a sequence of design decisions in the form of a series of problems and solutions which radiate from a design objective. The Marple tree can be used inductively to record past design rationale or speculatively to explore alternative courses of action Cross Sivaloganathan, 2005. Asimow 1964 divided design process into three stages: 1 feasibility study phase, 2 preliminary design phase, and 3 detailed design phase. As such Watts stated that design process entails cycles of analysis, synthesis and evaluation, moving through design decisions from abstract levels to ever more concrete ones. French 1971 expressed four steps for design process which were: analysis, conceptual design, development of the generated schemes, and detailing. Also, Jones 1980 stated three stages consisting of analysis, synthesis and evaluation for design process. Hubka 1982 believed that design process entails: establishing function structure technical process, applying technical system, establishing boundaries, and so on. Pahl and Beitz 1986 proposed four steps for design process: clarification of tasks, conceptual design, embodiment design-which consists of preliminary layouts and configurations, selecting the most desirable preliminary layouts and refining and evaluating against technical and economic criteria-and detailed design.