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Jarkas A.,Mazaya Holding Co.
Journal of Engineering, Design and Technology | Year: 2012

Purpose: The purpose of this paper is to investigate the effects and relative influence of: surface floor area; number of trowelling machines used in the operation; machine floating ring diameter size; and operative employment mode, on power-trowelling productivity of concrete surface floors. Design/methodology/approach: To achieve this objective, a sufficiently large volume of productivity data was collected and analyzed using the categorical-regression method. As a result, the effects and relative influence of the factors investigated on trowelling productivity were determined and quantified. Findings: The findings show significant influence of the factors explored on the trowelling productivity of concrete surface floors, which substantiate the importance of the "economy of scale" concept, and confirm the negative effect of "overcrowding". On the other hand, contrary to many previous productivity research findings, and anecdotal perceptions of industry practitioners, the results obtained provide little evidence to the positive impact of the subcontracting employment mode on the trowelling operation. Research limitations/implications: Further research into the influence of other factors which could not be determined by this study, i.e. quantifying the difference in trowelling productivity between the "walk-behind" and "ride-on" machine types, and the average change in the operation efficiency as a result of utilizing the 0.60 m "walk-behind" floating ring diameter size, in comparison with the 0.80, 1.00, and 1.20 m explored ring-size, is recommended. On the other hand, the results obtained suggest that for a specific surface floor area, there may be an optimum number of trowelling machines, which leads to optimum trowelling productivity. It is, therefore, recommended to determine this number in order to rationalize the use of such devices and optimize the efficiency of the operation. Practical implications: The findings of this research can provide estimators, planners and construction managers guidance for reasonable estimates, effective planning and efficient operative utilization. The results obtained may be further used to "benchmark" the efficiency of the operation, and "formalize" the specific productivity knowledge acquired. Originality/value: The outcomes of this study fill a gap in productivity knowledge of primary factors influencing an important surface floor finish technique, which is frequently encountered on concrete construction sites, especially parking structures, storages and industrial facilities. © Emerald Group Publishing Limited. Source


Jarkas A.M.,Mazaya Holding Co.
Journal of Construction Engineering and Management | Year: 2012

Buildability is one of the most important factors influencing labor productivity. A thorough investigation of the literature, however, revealed a dearth of research into its effects on the labor productivity of an integral trade of the in situ reinforced concrete material; namely, rebar installation, especially at the activity levels. Because reinforced concrete columns are among the major encountered activities on construction sites, the objective of this research is to explore primary buildability factors influencing their rebar installation labor productivity. To achieve this objective, a sufficiently large volume of productivity data was collected and analyzed by using multiple and categorical-interaction-regression methods. As a result, the effects of the variability of column sizes, rebar diameter size, reinforcement quantity, and column geometry, are determined and quantified. Although the extent of the size variability and circular geometry show significant negative impacts on the labor efficiency of the operation, the rebar diameter size and quantity of reinforcement installed exhibit positive effects. The results obtained may be used to provide designers and construction managers with feedback on how well the design of this activity considers the requirements of buildability, and the consequences of designers' decisions on the productivity of the installation operation. Moreover, a set of practical recommendations is presented, which upon implementation can improve the design buildability level of the activity explored and, thus, translate into higher labor productivity and more efficient planning and utilization of operatives. © 2012 American Society of Civil Engineers. Source


Jarkas A.M.,Mazaya Holding Co.
Journal of Engineering, Design and Technology | Year: 2010

Purpose: The objective of this paper is to investigate the effects and relative influence of: grid patterns; variability of foundation sizes; total surface area; and average surface area, on formwork labour productivity of isolated foundations. Design/methodology/approach: To achieve this objective, a sufficiently large volume of productivity data were collected and analyzed at both levels; macro, and micro, using the linear regression method. As a result, the effects and relative influence of the investigated factors on formwork labour productivity are determined and quantified. Findings: The findings show significant impacts of the buildability factors investigated on formwork labour productivity, and substantiate the importance of applying the rationalization and standardization concepts to the design stage of construction projects. Research limitations/implications: Further research into the effects of buildability factors on formwork, and other related trades of in situ reinforced concrete material, i.e. rebar fixing/installation and concreting, labour productivity, which are common to other structural elements and activities such as, grade/ground beams, columns, walls, beams, and slabs, is recommended, so that the related findings can ultimately be used to develop an automated "Buildability Design Support System" to formalize the buildability knowledge of reinforced concrete construction projects. Practical implications: The outcomes of this research provide designers with feedback on how well their designs consider the requirements of buildability principles, and the tangible consequences of their decisions on labour productivity. In addition, practical recommendations deduced from the findings are presented, which upon implementation, can improve the buildability level of this activity, hence translate into higher labour efficiency and lower labour costs. On the other hand, the depicted patterns may provide guidance to construction managers for effective activity planning and efficient labour utilization. Originality/value: The findings fill a gap in buildability knowledge and its influence on formwork labour productivity of an important, labour intensive, activity within the in situ reinforced concrete construction projects. © Emerald Group Publishing Limited. Source


Jarkas A.M.,Mazaya Holding Co.
Canadian Journal of Civil Engineering | Year: 2010

Several factors affect labour productivity, but buildability is one of the most important. A thorough investigation of the literature, however, revealed a dearth of research into the effect of buildability on labour productivity of in situ reinforced concrete construction. Therefore, this research focuses on quantifying the effects and relative influence of the variability of beam sizes, repetition of floor layout, floor area, average slab panel area, intersection of beams, beam-floor area ratio, and percentage of curved beams and nonrectangular slab panels on formwork labour productivity of building floors. Apart from the variability of beam sizes, buildability factors investigated are found to have significant effects on formwork labour productivity, confirming the importance of applying the concepts of rationalization, standardization, and repetition to the design stage of building projects. The findings can be used to provide designers with feedback on how well their designs consider the requirements of buildability principles and the consequences of their decisions on the labour efficiency of the formwork operation. On the other hand, the depicted patterns of results may further provide guidance to construction managers for effective activity planning and efficient labour utilization. Source


Jarkas A.M.,Mazaya Holding Co. | Radosavljevic M.,University of Reading
Journal of Management in Engineering | Year: 2013

In today's global economic conditions, improving the productivity of the construction industry is becoming more pressing than ever. Several factors impact the efficiency of construction operatives, but motivation is among the most important. Since low productivity is one of the significant challenges facing the construction industry in the State of Kuwait, the objective of this case study is to identify, explore, and rank the relative importance of the factors perceived to impact the motivational level of master craftsmen involved in primary construction trades. To achieve this objective, a structured questionnaire survey comprising 23 factors, which were shortlisted based on relevant previous research on motivation, the input of local industry experts, and numerous interviews with skilled operatives, was distributed to a large number of master craftsmen. Using a relative importance index technique, the following prominent factors are identified: (1) payment delay; (2) rework; (3) lack of a financial incentive scheme; (4) the extent of change orders during execution; (5) incompetent supervisors; (6) delays in responding to requests for information (RFI); (7) overcrowding and operatives interface; (8) unrealistic scheduling and performance expectation; (9) shortage of materials on site; and (10) quality level of drawings. The findings can be used to provide industry practitioners with guidance for focusing, acting upon, and controlling the critical factors influencing the performance of master craftsmen, hence, assist in achieving an efficient utilization of the workforce, and a reasonable level of competitiveness and a cost-effective operation. © 2013 American Society of Civil Engineers. Source

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