The selection of design-build operational variations in the People's Republic of China using Delphi method and fuzzy set theory

Abstract

The design-build (DB) system has been demonstrated as an effective delivery method and has gained its popularity worldwide. Within the overall concept of design-build, a number of operational variations of the DB system have been developed, which are similar to, but different from each other. Every DB operational variation has its own strengths and weaknesses, and owners have to choose the appropriate one to best deliver their projects. However, it is never an easy task and poses changes to most of DB owners. In addition, there are few, if any, systematic research studies focusing on the selection of DB operational variations. The aim of this research study is, therefore, to develop a model using the Delphi survey technique and fuzzy set theory for objectively, reliably and practically choosing the appropriate DB operational variations in the construction industry of China. Although the importance of selecting an appropriate DB operational variation has been widely accepted, the classification of DB operational variations remains controversial. A comprehensive literature review has been conducted to assess various classification frameworks proposed by different researchers. The rationales for their classifications were explored and summarized as contracting methods, design proportions, and contractor selection methods. These classification rules were then developed to set up a new classification framework. Finally, five fundamental operational variations of DB have been proposed, which include develop and construct, novation design-build, enhanced design-build, traditional design-build and turnkey. These five categories serve as the basic alternative options in the selection of DB operational variations. In order to facilitate the selection process, a set of evaluation criteria for determining the appropriateness of each operational variation is required. A three-round Delphi questionnaire survey was conducted with 20 construction experts in the People's Republic of China (PRC) to obtain such criteria. Seven top selection criteria and their importance weightings were finally identified, which include, namely, (1) availability of competent design-builders, with the weighting of 0.178; (2) owner's experience, with the weighting of 0.156; (3) project complexity, with the weighting of 0.147; (4) owner's control of project, with the weighting of 0.137; (5) early commencement & short duration, with the weighting of 0.132; (6) reduced responsibility or involvement, with the weighting of 0.127; and (7) clear end user's requirements, with the weighting of 0.122. A statistically significant agreement on the top seven selection criteria was also obtained. These identified criteria could furnish stakeholders, in particular the DB owners, with objective and reliable perspectives to compare and evaluate the different operational variations of the DB system. The selection of DB operational variation is a complex multi-criteria decision making process involving fuzzy characteristics and uncertainties. A fuzzy multi-criteria decision-making (FMCDM) model is regarded as the most suitable technique for this problem. The fuzzy membership function, which is a core concept in fuzzy set theory, can be adopted to measure the performance of each operational variation against the selection criteria. A modified horizontal approach with the bisector error method was applied to set up the fuzzy membership functions. These fuzzy membership functions provided quantitative calculation method for measuring performance of each DB operational variation. As a result, owners could objectively examine the suitability of each DB operational variation. A fuzzy multi-criteria decision-making model was finally developed using the weighted mean method to aggregate the performance of DB operational variations measured against the selection criteria. The proposed model enables owners to perform quantitative calculations in a fuzzy decision-making environment and provides a useful tool to select the most suitable DB operational variation with respect to a set of situational factors. This research study is the first attempt to develop a fuzzy multi-criteria selection model for DB operational variations. The selection model will not only offer a better understanding of different design-build options but also can be used as a guideline for the design-build delivery practice. It will in turn, help promote the design-build application in China. In addition, considering that the problem of selecting appropriate DB operational variations also exist in the overseas DB markets, this research study provides useful reference for similar studies in different geographical locations.