Selecting an appropriate contractor is essential for the success of any construction project. Contractor prequalification procedure makes it possible to admit for tendering only competent contractor. Prequalification is a multi-criteria decision problem that is, in essence, largely dependent on the uncertainty and vagueness in the nature of construction projects and subjective judgement of the decision-maker. This paper presents a systematic prequalification procedure, based on Fuzzy Set Theory, whose main differences and advantages in comparison with other models are the use of an algorithm to handle the inconsistencies in the fuzzy preference relation when pair-wise comparison judgements are used and the use of linguistic assessment or exact assessment of performance of the contractors on qualitative or quantitative criterion, respectively. Finally, a case study for the rehabilitation project of a building at Technical University of Cartagena is presented to illustrate the use of the proposed model and to demonstrate its effectiveness

Most of the real-world multicriteria decision-making (MCDM) problems contain a mixture of quantitative and qualitative criteria; therefore quantitative MCDM methods are inadequate for handling this type of decision problems. In this paper, a MCDM method based on the Fuzzy Sets Theory and on the Analytic Hierarchy Process (AHP) is proposed. This method incorporates a number of perspectives on how to approach the fuzzy MCDM problem, as follows: (1) combining quantitative and qualitative criteria; (2) expressing criteria pair-wise comparison in linguistic terms and performance of the alternative on each criterion in linguistic terms or exact values when criterion is qualitative or quantitative, respectively; (3) converting all the assessments into trapezoidal fuzzy numbers; (4) using the difference minimization method to calculate the local weight of criteria, employing the algebraic operations of fuzzy numbers based on the concept of α-cuts; (5) calculating the global weight of criteria and the global performance of each alternative using geometric mean and the weighted sum, respectively; (6) using the centroid method to rank the alternatives. Finally, an illustrative example on evaluation of several combined cooling, heat, and power production systems is used to demonstrate the effectiveness of the proposed methodology.

Owing to the wide range of trigeneration systems suitable for small-scale applications, the selection of the optimal system according to the end users' requirements and environmental conditions is crucial. The evaluation and comparison of possible alternatives of trigeneration systems are a multi-criteria decision problem because not only economic aspects must be considered but also technical, environmental and social aspects. This paper presents the case of selection of a trigeneration system for a typical residential building. Several kinds of trigeneration systems, whose dynamical sources are Stirling engines, micro-turbines, reciprocating engines and fuel cells, respectively, and a separate generation system are evaluated and compared in detail. As the evaluation criteria are a mixture of quantitative and qualitative criteria, quantitative multi-criteria methods are inadequate for handling this type of problems. Therefore a multi-criteria decision-making method, which combines the subjectivity of decision maker and the objectivity of numerical data, based on Fuzzy Set Theory and Analytic Hierarchy Process is proposed to solve this selection problem. Copyright © 2010 John Wiley & Sons, Ltd.

The main difference between the Last Planner production control system developed by Ballard and classical control systems is the way in which projects are controlled and planned. The Last Planner system focuses on controlling production units, workflows, and the quality of the performed work. It also permits the identification of the causes for the noncompletion of planned work and decision making in accordance with the project requirements so that actions are timely and productivity is increased. The objective of this paper is to present the results obtained from implementing the Last Planner system in the construction department of a chemical company. In this department, an information flow problem was detected among its members, in which supervisors lacked knowledge about the work to be performed until the project had been perfectly designed. This problem often led to long delays in the projects. The results from the Last Planner system implementation show that identifying the constraints of the planned work leads to an improvement in the percentage and quality of completed activities.