انتخاب پیمانکاران نوسازی مسکن بر اساس یک رویکرد ترکیبی گسترش کارکرد کیفیت QFD فازی

With low demand for new construction, limited land usage, and being aware of sustainability, the refurbishment market has grown greatly and has become more in demand in the construction industry. Most refurbishment work, however, involves a high level of risk, uncertainty, and coordination, which are likely to cause asymmetric information between contractors and residents in a refurbishment process. Most private refurbishment contractor selections are usually based on word-of-mouth referrals that lack a systematic and objective assessment method. This study proposes a hybrid approach combining fuzzy set theory and quality function deployment (QFD) to establish a housing refurbishment contractor selection model. With this model, residents can select an optimal refurbishment contractor according to requirements. To test the effectiveness of the proposed model, a known multiple criteria decision-making method, PROMETHEE, is applied to compare the results of contractor selections. The result reveals that the proposed hybrid fuzzy-QFD approach can be expected to be successful and has potential for handling multiple criteria decision-making problems.

The refurbishment industry has received increasing attention and grown hugely in the last decade, because of the change in economic conditions and the emphasis on sustainable development [1]. Global organizations have invested plentiful resources in creating sustainable refurbishment environments [2] and [3]. Although a refurbishment project is relatively small, in some developed countries, the total turnover of the refurbishment market reaches almost a half of the total construction output [4]. Refurbishment has a heterogeneous nature that requires different specialties to perform well in highly variable conditions and requires knowledge and technique to do well [5]. These kinds of projects are usually characterized by complex, small-scale and highly labor-intensive renovation tasks that are full of risk and uncertainty [6] and [7]. Some research reveals that one of the severest challenges of refurbishment projects is asymmetric information between contractors and residents in a refurbishment process [8]. Residents with inadequate refurbishment knowledge usually lack the judgment ability on cost, quality and service provided by contractors. Disreputable contractors who propose deceitful cost estimation, unpredicted quality, and unstable service usually affects customers' satisfaction and project performance. Asymmetric information results in the gap between expectation and perception, and it may lead residents to be in vulnerable conditions [9]. A great number of studies have explored how to evaluate construction bidding contractors for new construction projects [10] and [11]. Only a few efforts, however, have been focused on establishing a contractor selection model in refurbishment projects [12], because most housing refurbishment business comes from word-of-mouth referrals [8]. Some refurbishment jobs are even conducted by unskilled “cow boy” operators, which has multiplied management difficulties [13]. The nature of refurbishment makes it difficult to select an optimal refurbishment contractor. Therefore, an effective and structured contractor selection process for residents needs to be developed. Quality function deployment (QFD) is a quality management method for converting the customer's needs into design specifications [14]. It brings an opportunity to solve asymmetric information problems between resident's implicit needs (What) and contractor's explicit services (How). To help residents express their preference needs precisely, fuzzy set theory is introduced to combine the QFD, a hybrid fuzzy-QFD approach, to explore the asymmetric refurbishment condition between residents and contractors. By means of a refurbishment contractor selection example, the multiple criteria PROMETHEE methodology is adopted to compare results from the proposed approach to test the effectiveness. It is expected that this innovative approach can make a contractor selection process much more useful and the conventional multi-criteria decision-making problems more convincing.

Refurbishment has a heterogeneous nature that requires different specialties and management skills to perform well in highly variable conditions. Traditional housing refurbishment contractor selection procedures are controversial because most of them are usually based on word-of-mouth referrals or resident's intuitive judgments. This may easily lead to a vicious cycle of asymmetric information if, unfortunately, a resident is not able to select an appropriate contractor to conduct a complicated refurbishment project. The introduction of QFD supports the relation assessment for residents' refurbishment requirements (WHATs) and contractors' specifications (HOWs). By using the fuzzy set theory, residents can select a satisfactory contractor even when they have indistinct needs and vague preferences. Traditional application of QFD did only determine, or realize, the relation between WHATs and HOWs. This study has extended the implication of QFD to present an innovative approach for solving the refurbishment contractor selection problems. Compared with conventional multi-criteria decision-making methods, the result of the case study using the hybrid fuzzy-QFD approach has made a successful experiment and demonstrated potential as an alternative analytic tool with less judgment time and more objectivity. The disadvantages of time and objectivity are usually regarded as limitations in traditional multi-criteria decision-making methods. The purpose of this study, however, is not to judge nor validate the application of PROMETHEE methodology. On the contrary, this study pays more attention to establishing an alternative analytic structure well suited to different kinds of multi-criteria decision-making problems. Some extensions and improvements need to be accomplished from this approach. The approach can be extended to explore various multi-criteria decision-making issues such as selection among alternatives or project assessment, if the variables or criteria can be modified with flexibility to conform to the practical needs. How to ensure the completeness of judgment information, such as explicit service or tangible specifications offered by contractors, to rationalize the approach will be an improvement challenge. The number of questionnaire samples may also influence the way of determining WHATs, HOWs and their computing results. It is expected that there will be a steady improvement, based on the core of the proposed approach, in providing more samples and sufficient information in the further research to make the contractor selection more convincing.