Mapping site-based construction workers’ motivation: Expectancy theory approach

The aim of this study is to apply a recently proposed model of motivation based on expectancy theory to site-based workers in the construction context and confirm the validity of this model for the construction industry. The study drew upon data from 194 site-based construction workers in Iran to test the proposed model of motivation. To this end, the structural equation modelling (SEM) approach based on the confirmatory factor analysis (CFA) technique was deployed. The study reveals that the proposed model of expectancy theory incorporating five indicators (i.e. intrinsic instrumentality, extrinsic instrumentality, intrinsic valence, extrinsic valence and expectancy) is able to map the process of construction workers’ motivation. Nonetheless, the findings posit that intrinsic indicators could be more effective than extrinsic ones. This proffers the necessity of construction managers placing further focus on intrinsic motivators to motivate workers.

Effect of mix proportion on robustness of self-compacting concrete

U ovom radu prikazan je eksperimentalni program ocjenjivanja robusnosti za četiri različita samozbijajuća betona (eng. Self Compacting Concrete - SCC). Projektirana je kontrolna mješavina te tri serije mješavina s razlikama u osnovnim svojstvima u svježem stanju. Za ocjenu robusnosti u odabranim mješavinama se mijenjala količina vode. Ispitane mješavine su zatim rangirane primjenom metode višeatributnog odlučivanja. Rezultati pokazuju da smanjenje otpornosti na segregaciju i smanjenje sposobnosti zaobilaženja prepreka uzrokuje značajno smanjenje robusnosti samozbijajućih betona.An experimental program aimed at evaluating robustness of four distinct types of self-compacted concrete (SCC) is presented in this paper. A control mix was designed and three series of mixes were made, with variation of principal fresh mix properties. In order to evaluate robustness, the selected mixes were subjected to variations in water content. The tested mixes were then ranked using the multi-attribute decision making method. The results indicate that the reduction in segregation resistance, and the decrease in the obstacle passing ability, lead to a considerable decrease in robustness of self-compacting concrete

An Integrated Model for Multi-Mode Resource-Constrained Multi-Project Scheduling Problems Considering Supply Management with Sustainable Approach in the Construction Industry under Uncertainty Using Evidence Theory and Optimization Algorithms

In this study, the multi-mode resource-constrained multi-project scheduling problems (MMRCMPSPs) considering supply management and sustainable approach in the construction industry under uncertain conditions have been investigated using evidence theory to mathematical modeling and solving by multi-objective optimization algorithms. In this regard, a multi-objective mathematical model has been proposed, in which the first objective function aims to maximize a weighted selection of projects based on economic, environmental, technical, social, organizational, and competitive factors; the second objective function is focused on maximizing profit, and the third objective function is aimed at minimizing the risk of supply management. Moreover, various components, such as interest rates, carbon penalties, and other implementation limitations and additional constraints, have also been considered in the modeling and mathematical relationships to improve the model’s performance and make it more relevant to real-world conditions and related issues, leading to better practical applications. In the mathematical modeling adopted, the processing time of project activities has been considered uncertain, and the evidence theory has been utilized. This method can provide a flexible and rational approach based on evidence and knowledge in the face of uncertainty. In addition, to solve the proposed multi-objective mathematical model, metaheuristic optimization algorithms, such as the differential evolution (DE) algorithm based on the Pareto archive, have been used, and for evaluating the results, the non-dominated sorting genetic algorithm II (NSGA-II) has also been employed. Furthermore, the results have been compared based on multi-objective evaluation criteria, such as quality metric (QM), spacing metric (SM), and diversity metric (DM). It is worth noting that to investigate the performance and application of the proposed model, multiple evaluations have been conducted on sample problems with different dimensions, as well as a case study on residential apartment construction projects by a contracting company. In this respect, the answers obtained from solving the model using the multi-objective DE algorithm were better and superior to the NSGA-II algorithm and had a more favorable performance. Generally, the results indicate that using the integrated multi-objective mathematical model in the present research for managing and scheduling multi-mode resource-constrained multi-project problems, especially in the construction industry, can lead to an optimal state consistent with the desired objectives and can significantly improve the progress and completion of projects

The Robustness of Self Consolidating Concrete Due to Changes in Mixing Water

Although self consolidating concrete (SCC) has been developed for more than two decades, its practical use is still limited. This is partly because its properties are not fully known and partly because its performance is highly sensitive. In the current study, an experimental program was undertaken to evaluate the robustness of eight selected SCCs. According to the obtained results, the variations of SCC robustness that determined by using innovative method (multi attribute decision making) are studied based on the variations of rheology parameters. The results indicate that there is a direct relationship between robustness and segregation resistance of SCC. Also the greatest reduction in robustness occurs in increase in yield stress together with plastic viscosity. Moreover, the scattering of compressive strength results show that there is a level of robustness in fresh state that after that the scattering of results in hardened state may be affected

A survey of the factors affecting the productivity of construction projects in Iran

The intense competition between the Iranian construction companies has led them to take all appropriate measures to decrease the costs as much as possible. Hence, due to the pivotal role of human resources in construction projects cost, a major part of Iranian construction companies seek their profitability and survival in maximizing the productivity of their operatives. Because of the widespread belief among contractors about the low productivity of daily workers and operatives with basic salary, they commit a major part of their projects activities to sub-contractors. Deployment of sub-contractors by construction firms has become largely conventional in country's construction projects. The aims of this paper is defined as determining the factors and grounds affecting sub-contractors productivity and evaluate their overall negative side effects on project productivity via a structured questionnaire. A total of 31 factors selected and were divided into 7 broad categories. The perceptions of companies managers were asked about the level of effect brought about by the mentioned factors and groups upon productivity on a time based criterion. The analysis indicated that the most important grounds affecting sub-contractors productivity in descending order include: Materials/Tools, Construction technology and method, Planning, Supervision system, Reworks, Weather, and Jobsite condition. Project managers should focus on the identified major grounds and relevant factors in order to improve productivity as long as they commit construction activities to sub-contractors

Labour productivity in Iranian construction projects perceptions of chief executive officers

Purpose – The purpose of this paper is twofold. First, it aims to highlight the main factors and items affecting the productivity of construction projects, based on the perceptions of CEOs in construction companies in Iran. Second, the study compares the elicited CEOs’ perceptions against the findings of studies based on the views of such as project managers, middle managers and employees in other levels. Design/methodology/approach – The study drew upon literature on construction work to develop a conceptual model. Further, a total of 60 CEOs from road construction companies were surveyed using a five-point Likert scale questionnaire to generate the data. The collated data were categorised and ranked according to the CEOs perceived level of importance using the relative importance index. Findings – The findings highlight the main factors and items affecting labour productivity in construction projects in Iran as perceived by CEOs, which are mainly of human resources management nature and could be attributed to motivation and managerial policy aspects. The study also recognises that factors associated with the working environment particularly safety and health are perceived as insignificant by Iranian CEOs which could be a concern for the Iranian construction industry. The discussions shed some light on the discrepancies between the perceptions of CEOs and previous studies in regards to major determinants of productivity in the construction context. Originality/value – This study is the first study aiming at discussing the perceptions of CEOs of construction companies active in construction projects in Iran. As such, the study highlights the standpoint of the main decision makers in construction companies in regards to labour productivity in the construction sector. Thus, the key contribution of the present study is providing insight into the perceptions of CEOs, who play the most vital role in strategic development of construction companies whereas previous studies have mostly focused on project or middle managers having a lower influence in determining the strategic plans of companies

Implementing the international benchmarking labour productivity theoretical model

Purpose – Building upon the results of a critical review of previous studies, the purpose of this paper is to present a framework to enhance the reliability of the theoretical model for international benchmarking of labour productivity (TMIBLP) method for construction project activities. The next part of the paper presents the results of implementing the proposed framework for construction activities in the Iranian construction industry. Design/methodology/approach – This paper draws upon a critical review of the literature to highlight the drawbacks of the previous studies concerning implementing TMIBLP within the construction industry. Identifying these shortcomings, the authors propose a framework for construction projects, which presents the procedure for deploying TMIBLP for construction activities in a reliable manner. The final section of the paper demonstrates the empirical implementation of the proposed framework within the Iranian construction industry. Findings – The primary contributions of the paper include: identifying the drawbacks of previous studies within the construction context, the framework that would lead construction managers towards more reliable implementation of benchmarking for construction projects, and determining the baseline of erecting steel structures in a developing country. Practical implications – A practical implementation of the TMIBLP method was presented to address the lack of research in Iran and to show the feasibility of using the framework developed. The authors investigated the daily labour productivity for the activity of structural steel erection for six projects in Tehran in order to determine the values of the baseline productivity for each project. Accordingly, the disruption index, performance ratio and project management index as the project benchmarks were calculated for all six projects. Originality/value – Underlining the necessity of implementing methods such as TMIBLP, this study outlines the outcomes of the first study on the benchmarking of construction activities deploying the proposed framework and using the data on erecting steel structures from six construction projects in Iran. The discussions provide guidelines for construction project managers regarding benchmarking labour productivity. The paper concludes with suggestions for future research opportunities