Unbalanced bidding is a common practice used in both unit price and lump sum contracts. Contractors may unbalance their bids in different forms for various reasons. The studies in the literature either focus on developing optimization models that assist contractors in winning contracts and maximizing profits of their bids through unbalancing or developing models that assist owners in detecting and/or preventing unbalanced bids during the bid evaluation stage. Unbalanced bidding is one of the most controversial subjects in the construction management literature and practice. Although there is no consensus on whether it is unethical or not, this practice is not usually for the benefit of owners. Therefore, owners have the right to reject the unbalanced bids and create a fair competition environment if they have a mechanism to detect it during the bid evaluation process. The main objective of this study is to propose a model, which consists of five different grading systems and helps owners in detecting unbalanced bids during the tendering process. In the proposed model, owners may either calculate the individual grades of each bidder or calculate the final score of each bidder by assigning different weights to these grading systems according to the project characteristics or their own needs. The final scores and bid prices of the contractors can be simultaneously evaluated. In order to demonstrate the applicability of the proposed model, an illustrative example is presented. It can be concluded that the proposed model can be effectively and easily used by owners for detecting unbalanced bids. This paper is the revised version of the paper that has been published in the proceedings of the Creative Construction Conference 2018 (Polat et al., 2018).
The formwork system (FWS) in reinforced concrete (RC) construction is a critical component. The appropriate FWS is selected based on a number of conflicting and compromising criteria, and the selection of the FWS is carried out by construction professionals with different technical and/or administrative backgrounds. The perspectives and perceptions of construction professionals and companies involved in the FWS selection process may vary depending on their motives. In addition, some building structural parameters may have a significant impact on the FWS selection criteria. Most of the former studies investigated the FWS selection criteria from only the perspective of contractors and neglected the potential differences in the perspectives and perceptions of different construction professionals (i.e., owners (CO), project managers (PM), construction managers (CM), site engineers (SE), planning engineers (PL), procurement engineers (PR), technical office engineers (TO), and formwork design and/or formwork sales engineers (FD/FSL)) and companies specialized in different fields (i.e., project management service (PMS), engineering and design (ENG/DSG), formwork and scaffolding (FW/SCF), and general and/or sub-contractor (GC/SC)) regarding this issue. Moreover, the impact of building structural parameters on the FWS selection criteria has not been investigated. This study aims to fill this knowledge gap through analysing the FWS selection criteria for building construction projects while comparing the perspectives and perceptions of different groups of construction professionals and companies and investigating how FWS selection criteria are affected by the building structural parameters. Based on a comprehensive literature review, 35 FWS selection criteria were identified and a questionnaire was developed. The questionnaire data obtained from 222 Turkish construction professionals were statistically analysed using mean score analysis, the Kruskal–Wallis test, and the Mann–Whitney U test. According to the study’s findings, the FD/FSL group presented significant statistical differences regarding the FWS selection criteria as compared to the CO, PM/CM/SE, and PL/PR/TO groups. Moreover, the total area of building construction and total building height significantly affected the FWS selection criteria. This study serves to underscore the perspectives of various groups of construction professionals and the critical connection between the structural parameters and FWS selection criteria. The findings of this study may guide construction professionals to select the appropriate FWS for their building construction projects.
Formwork system (FWS) is one of the key components in reinforced concrete (RC) construction. Therefore, selection of the most appropriate FWS plays a critical role in the project success. Since the FWS selection is affected by several compromising and conflicting criteria, numerous studies have been carried out to identify the FWS selection criteria and/or have employed various multi-criteria decision-making (MCDM) methods since the early 1990s. However, there is no research that conducts a critical review of the previous studies addressing the FWS selection criteria in building construction projects. This study aims to fill this knowledge gap. For this purpose, a critical review of the relevant literature was carried out using an integrative approach and the findings were validated through face-to-face interviews with professionals specialized in formwork engineering. The findings of this study may provide practitioners with a useful guide that can assist them in selecting the most appropriate FWS.
An unbalanced bid can be defined as a bid price that does not accurately reflect reasonable cost, contractor's profit, general overhead cost and other indirect costs. Selecting an unbalanced bidder as the contractor may lead to significant increases in the contract price. Therefore, detecting the unbalanced bids is a critical issue for owners. There are two main types of unbalanced bid, which consists of front-end loaded and quantity error exploitation. This study mainly focuses on the second type, namely quantity error exploitation, in which a contractor tends to increase the unit prices of items that are underestimated and reduce the unit prices of items that are overestimated because of errors in the estimated quantities. If an owner can detect the unbalanced bids during the awarding stage, a fair competition environment can be achieved. This study aims to provide owners with a model, which may assist them in detecting unbalanced bids. The proposed model uses five different grading systems. Owners may assign different weights to these grading systems and thereby the final score of each bidder can be calculated. All bidders can be evaluated based on the calculated final scores as well as the offered bid prices. The applicability of the proposed approach is demonstrated in an illustrative example. The findings of this study revealed that the proposed approach can be a useful tool for owners in detecting unbalanced bids.
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