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Improvement of Productivity through the Control of Continuity and Variation of Work Flow in Building Space

Improvement of Productivity through the Control of Continuity and Variation of Work Flow in... The majority of currently used construction productivity management systems rely on result-based management techniques, which have difficulties in managing in uncertain environments. Massive amounts of time and resources are wasted due to conflicts between works and constraints in space, etc. Hence, we need to recognize the limitations of existing result-based management systems and suggest a productivity management index that is expected to ensure that the issues of productivity reduction are properly controlled. Work flow refers to the progression of work in a limited time and space. Schedule delay and expense waste can be controlled by managing the work flow. Measurement of work flow is evaluated using 3 indices: Continuity Index, Variation Index, and Productivity Index. Therefore, this research suggests an evaluation and measurement system for work flow that shows the productivity of construction work both directly and indirectly, and thereby aims at an improvement in project performance by using a target index. Keywords: work flow; Variation Index; Continuity Index; productivity; Lean Construction 1. Introduction sites. Consequently, a reduction in productivity is often The productivity of construction work is influenced observed, such as discontinuous progression of works, by various factors including construction workers, delays in works, interference between works, and loss design documents, the nature of construction work, of materials. and external factors of construction, etc. In addition, Therefore, the various limitations of the result- the factor of uncertainties in the construction process based management approach currently used need to brings difficulties to project productivity management. be recognized and efforts need to be made to improve The occurrence of uncertainties in construction work such management practices. is inevitable since most current project management The concept of Lean Construction, in the context of systems operate in a top-down manner in which the productivity improvement, adopts the next generation lower level plan is determined by the upper level plan of procurement management technique, schedule (Tommelein, 2002). management technique, and performance management Researchers and site engineers in construction have technique based on productivity waste management. tried to develop appropriate methods of productivity Le an const ruct ion reduc es construction cost, measurement. (Han, 2010) The performance-based improves productivity, and thus aims to maximize productivity management techniques for a project customers' value by minimizing all ever-present factors provide unreliable outcomes on scheduling for a that may cause waste, which always exist during the project's stakeholders since they do not consider construction process. the environment of construction work that is Management of uncertainties by using the Last interdependent and has various uncertainties (Ballard Planner System (LPS) was recommended by the and Howell, 2003). Lean Construction Institute (LCI). However, the Inappropriate project management frequently causes LPS model provides a simple evaluation on the ratio inconsistencies between the planned work process and of the execution of the plan without the process of the actually executed work process on construction quantitative analysis. The weakness of LPS is that it allows neither the analysis of the productivity of the current works nor the proposal of a specific *Contact Author: Jaeho Cho, Research Professor, management goal. Department of Architectural Engineering, Dankook University, Hence, in the present progressive view, an objective 152, Jukjeon-ro, Suji-gu, Yongin-si, Gyeonggi-do, 448-701, Korea technique of measurement, evaluation, and control E-mail: cjhace@naver.com for productivity of work flow is required in order ( Received April 8, 2014 ; accepted October 31, 2014 ) Journal of Asian Architecture and Building Engineering/January 2015/96 89 to prevent issues of productivity reduction such as or to reduce the cost only upon the adoption of new schedule delay and excessive input of resources, etc. technology' since the model recognized the behavior of Approach methods in the context of work flow are production as a set of 'operation processes'. actively used in developed countries including the USA Koskela (1992) categorized the production process and some countries in Europe and are evaluated as into 4 steps including moving, waiting, operation, and successful methods. Also, the construction scheduling inspection, and thereby proposed a production theory technique has progressed drastically as scheduling that was understood by the cyclic process. software has become commercially available to project Variation of work flow in flow production theory participants. (Choi, 2012) was argued to worsen the waste in the production Therefore, this research proposes a method for the process and to lengthen the cycle time by increasing measurement of work flow that directly and indirectly non-value actions including moving and waiting. presents a productivity index of construction work. 'Variation' is the phenomenon caused by uncertain In addition, a work flow variation rating system is status. Ballard and Howell (1998) insisted that such proposed in order to support continuous improvement variation could be controlled by managing reliability. in performance on actual construction sites. In this They also argued that the method of approach used for study, the method of work flow measurement and case existing process planning 'was not able to ensure the analysis of the doctorate thesis written by Park, S. J. reliability of work order existing between works and (2006) is cited and re-analyzed. reliability in work flow.' Ballard (2000) recognized the limitation of project 2. Methods and Scope management when it is centered on result evaluation; A methodology for the measurement of work flow they therefore introduced concepts of flow production that indicates the productivity of the construction and LPS. Fig.1. below shows a fundamental concept process was proposed in this research. In addition, a diagram of the Last Planner System (LPS). case analysis was performed via the establishment of a system. In the case analysis, an improvement method for the performance of a project was offered by using a target control for Variation Index. This research was performed with the following procedure. (1) Discussion on related researches The direction of the research was proposed through investigations on literatures related to flow production theory, work flow variation, and work flow continuity. (2) Measurement method for work flow Various index functional formulas related to productivity were proposed based on the concept of Percent Plan Complete (PPC) and that of work flow evaluation. (3) Development of system prototype Fig.1. Concept of Last Planner System A prototype and operation process for the system was proposed based on the suggested measurement LPS differs from the traditional management system method. that was processed in a work order-centered manner. (4) Validation through case study The works documents should be performed ('Should' in Work flow variation was measured based on works Fig.1.) in a work plan, confirming the work order ('Will') on an apartment housing unit and an improvement based on the constraints that the workers are able to method was proposed by setting the target index. perform ('Can'), and check the execution status ('Did') (5) Conclusions through Percentage of Plan Completed (PPC). The results from this research are summarized and a LPS is the method of productivity management that method for future studies is proposed. is able to control the variations in plan by execution. Ballard and Howell (1998) emphasized the 3. Discussion on Related Researches importance of variation control in a construction Wa l k e r ( 1 9 8 5 ) i n t r o d u c e d t h e c o n c e p t t h a t production system by mentioning that "The first goal "Production process is the conversion process of input of Lean Construction is to understand the dynamics elements including resources, labor, and equipment to of construction production, the influence of mutual output elements as products" from production theory interdependency and variation in resource procurement of the existing manufacturing industry to productivity and production chain". analysis in the construction industry. In Parade Game, Tommelein (1999) analyzed the Koskela (1992) identified the limitation that influence of variation in work flow on the performance 'Walker's model was able to improve the productivity of the entire project through simulation and confirmed 90 JAABE vol.14 no.1 January 2015 Jaeyoul Chun the increase of stock occurring between works and 4. Control of Productivity Variation time delay due to higher variability. The variation of work flow can be distinguished Alarcon (1999) evaluated the influence of variation as the variation of labor work and that of work in in work flow on the cost and schedule of the project space. The difference between the execution plan and through a simulation called Playing Games. the completion work is developed while conducting Kim (2001) understood the Lean Principle that operation management on site. "Enhancement of reliability in schedule management Establishment of successful productivity and contributes improvement in work flow, productivity, continuous improvement in productivity are possibly and quality" and proposed a schedule information achieved when the Continuity Index of space work are model that can be utilized in the detailed planning controlled within the range of target management. stage and a subsequent method for variation control. The weakness of the existing LPS is that it does not Thomas (2003) analyzed the data of an inefficient present the analysis on productivity in terms of the work process through investigation of a case project, work continuity for currently ongoing work. and verified that the enhancement of reliability on The productivity can possibly be improved by labor flow contributed to improved productivity. securing the work continuity since the work continuity Bashford (2003) proposed two methods of uniform serves as a management index indicating an optimal work, one based on a single unit task and the other productivity of currently ongoing work. Hence, this based on a start point, as strategies for securing the study grafts a concept of variation management for work continuity by recognizing the similarities existing labor work and work in space onto LPS in order to between the manufacturing industry and construction analyze the factors decreasing productivity and control works. the work continuity (Refer to Fig.2.). Yoo (2004) presented the labor factors among the The schedule manager can reset the achievable factors influencing both work flow and its continuity target in the present progressive view by using a and proposed indexes listing the measurement of such variation index for work flow. This directly leads to the labor factors. In addition, the correlation between improvement in productivity. continuity of work flow and labor factors was analyzed Low continuity of work can be reflected in the through correlation analysis. improvement in productivity by workers on site by Kim (2005) proposed detailed guidelines for adjusting the resources since it indicates the work management as an operation method for a Lean System problems on site. in order to effectively perform Lean Construction in the domestic industry. Lee (2008) proposed a method of schedule delay analysis using learning effect and linear scheduling since cessations and changes of works in the construction industry cause reduction in productivity. Moon (2009) suggested an evaluation method on Percent Plan Complete (PPC) with consideration given to the variation of work flow. Ki m ( 2 0 0 9 ) p r e se n t e d a r e a l - t i m e p r o g r e ss management system for steel structure construction. Cecília Gravina da Rocha (2013) conducted an analysis on the causes of delay in works by using a Line of Balance (LOB) technique. As listed above, numerous studies aiming at improvement in inefficiency and low productivity in the construction industry by controlling variation and Fig.2. Control of Productivity Variation continuity of work flow have been reported through LCI and the International Group of Lean Construction 5. Measurement for Work Flow Indexes (IGLC). In this section, the concept of the PPC and the work The authors' discussion on existing studies indicates flow measurement for enhancement of productivity in that consultations at a stage prior to the execution construction work will be explained in terms of flow and analyses of constraints on space for the purpose production. of the management of uncertainties in construction First, the PPC presents the degree of achievement sites can enhance reliability of the plan. However, compared to the planned target and refers to the ratio difficulties arise in tracing the productivity of works of the current status to the ideal (the best target) that are currently ongoing and setting a target variation st a t us. Cont i nuous i m prove m e nt c a n be re a c he d index due to the absence of a quantitative method for by continuous removal of possible causes that may measuring the status of a plan by execution. impede moving forward from current status to ideal JAABE vol.14 no.1 January 2015 Jaeyoul Chun 91 WT (x,y): Number of days for waiting in space j where the status. For evaluation using the PPC, the ideal status in i,j work of 'i' is possibly done during measurement relation to the given condition is measured, followed period (date x ~ date y) by the measurement of current status. In this research, continuity and variation of work The Variation of Work Flow (VWF) increases the flow are measured by using the concept of PPC. By 'non-value actions' during the construction process, comparing the variation of work flow in the current resulting in lengthening of cycle time and reduction of status and that in the ideal status, the process and production capacity. Hence, it is measured in order to causes that lead to current productivity are measured. control such results. Furthermore, the users can improve productivity Such variation can be classified into Variation of Input continuously by setting appropriate target indexes. Resource (VIR) and Variation of Operation Process In business, there is an oft-repeated statement: (VOP) ba se d on t he be ha vi o r of t he produc t i on. "If you don't measure it, you can't manage it"; The variation in input resources can be measured the productivity-related-index that quantitatively by analyzing the changes in planned input resources presents the current status is essential to effectively during a planned period of specific work. The amount managing the production system in construction. The of VIR can be expressed by the formula (4) below. measurement indexes systematically present the target to be achieved in the project, and provide a quantitative level of achievement. The properties of work flow …………….……....(4) include Continuity Index and Variation Index, and the VIR (x,y): Variation in input resources of work 'i' during work measurement methods for each index are as follows. period (date x ~ date y) The CWF (Continuity of Work Flow) is classified th IR : Amount of input resources at n work day of work 'i' i,n into Work Flow Continuity in Space (WFCS) and Average amount of input resources during work 'i' Work Flow Continuity on Work (WFCW). The WFCS AIR (x,y): period (date x ~ date y) means the degree of sequential execution without spare time or waiting time in each work per unit space. This The direct comparison of VIR between different can be expressed as the following formula (1). works or different projects is impossible since the VIR changes with the amount of planned input .........................................……………….(1) resources. For standard comparison, the Coefficient of WFCS: Work Flow Continuity in Space Variation in Input Resource (CVIR) of subject work CSW: Count of Space on Working classification can be measured by calculating the TCSW: Total Count of Space on Possible Working function in the formula (5) below. The Continuity Index for ideal work space is 100%, ………...……………………(5) meaning that the work is in progression in every work VOP is the variation of execution in relation to the space where the work is possibly performed. plan. It is called PPC in LPS and is used in LCI. In this The WFCW means the degree of sequential study, it is defined as the variation in the amount of execution of a work. The number of days for waiting work (labor). The value of such variation is obtained is measured based on every space in which the work by dividing the planned amount of work by the actually of 'i' is in progression 'for a certain period'. This can be executed amount of work. expressed as the following formula (2). It is also used as performance indicators that ………………….(2) measure the reliability of the subject work. The VOP is expressed as the formula (6) below. WT (x,y): Number of days for waiting in work 'i' during measurement period (date x ~ date y) AWA (x,y): Actual number of days for work in work 'i' during measurement period (date x ~ date y) ………………….……….…(6) NWD : Number of days on which the execution was x,y VOP (x ,y ): Variation in operation processes of work 'i' performed i,j j j impossible due to non-manageable factors including at 'j' space during work period (date x ~ date y) weather during measurement period (date x ~ date y) th NPW : Amount of work that was planned for n work day at i,j,n 'j' space WT (x,y) is defined as WFCW (Work Flow i,j NDW : Amount of work that has been actually executed on i,j,n th Continuity on Work). The ideal WFCW value is '0', n work day at 'j' space meaning continuous execution of work without waiting days during the measurement period. This can be The direct comparison of VOP between different expressed as the following formula (3). works or different projects is impossible since the VOP changes with the amount of work space. Coefficient of Variation of Operation Process (CVOP) for subject ………….….…………………...(3) 92 JAABE vol.14 no.1 January 2015 Jaeyoul Chun work can be measured by calculating the following 7. System Prototype formula (7). Developing a system that allows for automation of input/output information and the integrated operation of an application program is required in order to measure work flow and effectively perform …………………………(7) productivity management. In terms of developing In general, productivity refers to performance and it a system, the present study is confined to the is 'Productivity = Output/Input'. The productivity used measurement for construction work flow. in this research was mainly focused on productivity in Basic information on the work plan is provided by relation to labor. The amount of Productivity Variation the Project Management Information System. Schedule (PV) can be obtained by calculating the following analysis and causal analysis for schedule delay are formula (8). supported by the Schedule Management System and LPS. Statistical analysis is performed by SPSS, the statistical analysis program. Each system provides ………………………………..(8) a unique function according to its own purpose and PV (x,y): Amount of variation in productivity of work 'i' during i interoperates with the Work Flow Evaluation System work period (date x ~ date y), (WFES) prototype in this research. LP : Productivity of work 'i' i Practically, the WFES suggested in this research ALP (x,y): Average productivity of work 'i' i allows mutual interoperation by using data tables in MS-EXCEL. For standard comparison, the Coef ficient of The operation algorithm for the system is as the Productivity Variation (CPV) can be measured by following Fig.4. Initial plan (Should) and feasibility calculating the following formula (9). plan (Can) are prepared based upon the schedule program. Next, action plan (Will) is determined through discussion between the stakeholders for …………..………………………...(9) rationalization of schedule planning. Once an action plan is determined, variation in work flow and 6. Relationship between Work Flow and Productivity continuity of work flow are measured by utilizing A higher continuity of space means a sequential the WFES system on work flow from the present progression of multiple works in a limited space. This progressive point of view. reduces the duration of the construction along with a Work flow is assessed by evaluating the earned value reduction in variation in work load. for continuity in space. The subjects of evaluation such A greater continuity of work means the reduction of as work flow continuity in space, labor efforts, and variation in input resources through continuous work variation are measured based on the concept of PPC. and improvement in productivity upon learning the Causes of delay are determined by analyzing Variation effects. Index and enhanceable productivity is predicted by As a result, the reduction of variation in work flow adjusting a target variation index. greatly influences the construction duration. The influence of continuity and variation of work flow on productivity is schematized and shown in Fig.3. Fig.4. System Operation Process based on CWF and VWF Fig.3. Relationship in Variation of Work Flow and Productivity JAABE vol.14 no.1 January 2015 Jaeyoul Chun 93 Table 1. Results of Work Flow Measurement (Formwork) Date Production (m ) Labor (crew) Labor Productivity (%) A_IR CVIR WT 5.02~5.08 12,194 158 77.17 23 39.9 14 5.09~5.15 11,894 174 68.35 29 44.8 13 5.16~5.22 14,563 192 75.84 32 42.7 14 5.23~5.29 14,317 210 68.17 30 45.0 11 5.30~6.05 14,155 214 66.14 32 46.0 11 6.06~6.12 14,527 164 88.57 27 34.1 12 6.13~6.19 14,344 189 75.89 32 40.7 15 6.20~6.26 14,438 158 91.37 26 34.2 16 6.27~7.03 13,633 157 86.83 31 36.7 12 7.04~7.10 14,498 156 92.93 26 33.3 16 7.11~7.17 12,803 173 74.00 29 41.2 10 7.18~7.24 13,716 170 80.68 28 40.0 14 8.08~8.14 11,947 121 98.72 20 32.2 16 8.15~8.21 12,524 146 85.77 24 37.4 12 8.22~8.28 14,215 148 96.04 30 27.3 8 8.29~9.04 14,802 150 98.67 25 16.0 17 9.05~9.11 13,124 194 67.65 32 42.3 12 9.26~10.02 9,528 126 75.61 21 39.7 16 10.03~10.09 10,108 124 81.51 21 38.2 11 10.10~10.16 10,083 128 78.77 21 40.6 12 10.17~10.23 12,719 129 98.59 26 20.8 9 10.24~10.30 11,815 121 97.63 20 14.3 14 10.31~11.06 12,813 142 90.22 24 35.2 10 11.07~11.13 11,755 122 96.34 20 27.9 12 8. Case Study In this section, the measurement method for work flow is validated through case analysis and field applicability is reviewed in the WFES. For the case study, data on formwork scheduling and its execution status was collected from the case construction site of a construction firm. Variation and productivity were measured using the measurement technique. Table 1. shows the results of work flow measurement of the formwork. Input labor and productivity were measured on a daily basis. And these were aggregated again on a weekly basis. Approximately 32% of the difference between the minimum labor productivity of 66.14% and the maximum labor productivity of 98.72% was presented. (1) Evaluation of VIR The VWF was categorized into VOP and VIR. For the self-variation as VIR, variation in labor effort, and variation in productivity were measured for the subject work within a certain period. Fig.5. below shows an example of the measurement of VIR (5.73) and CVIR (46.54) for Laminating Work. (2) Improvement in productivity by using WFCS The duration of construction work is predicted by CWF and the improvement effect of productivity is estimated by adjusting the VIR and the VOP. The prediction of duration for the construction work can Fig.5. An Example of Measurement of VIR and CVIR be obtained by adjusting the WFCS. Fig.6. shows the WFCS measured as 41.67% over 27 days performed axes of the cell in Fig.6. represent the space and the th th from the 7 floor to the 10 floor of an apartment days of work, respectively. housing unit. At this point, it was predicted that the (3) Improvement in productivity by CVOP adjustment of WFCS to 50% could reduce the work For prediction of productivity, the CVIR, the CVOP, duration by 4 days (Fig.6.). The vertical and horizontal and the CPV were measured once after the selection 94 JAABE vol.14 no.1 January 2015 Jaeyoul Chun Fig.6. Prediction of Construction Duration through Adjustment of WFCS in Finishing Works evaluated the continuity of space work by accepting the execution plan and completion data on site from the interface system. On-site-engineers can reset possible productivity by controlling a variation index. This study took an academic approach to the concept of LPS productivity in view of site monitoring. The concepts of WFCW and WFCS per unit space were proposed as the information model for productivity Fig.7. Productivity through Adjustment of the CVOP improvement. WF CW and WF CS are the major of duration of work for the subject work. Formula (7) elements of the productivity variation. In the case of was applied in order to calculate the CVOP. The CVOP space work, variation in continuity of space work is of the target index was reset based on the analyzed inevitable since multiple works are conducted in one coefficient of variation in order to estimate the constrained space. Moving to another space or waiting improvement effect. In the case of the construction site should be ordered when conflict among two or more in this case study, the CVOP was measured as 26.64 works in the same space occur. by measuring the variation of work flow for concrete In this study, the status of multiple works in space th work during 6 days between October 17 and October and the management index on information systems nd 22 2010. Improvement in productivity by 16.83% were proposed in order to prevent reduction in was estimated by lowering the CVOP concerning labor productivity and schedule delay. Furthermore, the effort to target level 10.0. Fig.7. presents the prediction developed WFES allows determination of the factors of productivity through the adjustment of variation on decreasing productivity since it promptly provides the the construction site of the case study. information of variation in continuity of space work. The principal results obtained from this research are 9. Conclusion summarized as follows. This study proposed a method for improvement in (1) This research suggested a measurement method productivity by measuring the variation in continuity for continuity in space, continuity in work, and of work flow and controlling this variation in the space variation in relation to work flow in the construction where construction work is repeatedly conducted. It is phase. Work flow presents the operation process possible to determine whether the productivity of work of work in a limited time and space and the factors is progressing effectively or inappropriately by using causing schedule delay and productivity reduction can the Variation Index and Continuity Index of work flow. be prevented by managing the variations related to Existing studies were not able to propose a method work flow. for improvement in productivity in the present (2) The continuity and variation in work flow progressive view since these studies evaluated changes with sensitivity upon the adjustment of input productivity of completion versus execution plan as resources and work (labor) effort. they focused on analyzing outcomes. (3) The system prototype in this study enables For commercialization, this study reviewed the measurement of WFCS, WFCW, and VWF. This on-site-applicability through a case study. WFES system can predict the duration of the project by JAABE vol.14 no.1 January 2015 Jaeyoul Chun 95 14) Koskela, L. (1992) Application of the New Production Philosophy changing the target index. As a result, analysis on to Construction. Technical Report No.72, CIFE, Stanford the status of productivity reduction and continuous University, CA. enhancement of productivity is made possible. 15) LCI: Lean Construction Institute; www.leanconstruction.org (4) WFCS was evaluated by inputting the planned 16) Lee, Jae Seob (2008) Delay Analysis Using Learning Effect and and executed information for each day during 27 Linear Scheduling in Construction. Architectural Institute of Korea, 24 (5), pp.185-193. days of the construction work and was revealed to 17) Moon, H. G. Yu, J. H. and Kim , C. D. (2009) A Study of be 41.67%. At this point, it is possible to reduce the Evaluation Process and Chart of PPC considering Variation, Korea construction term by 4 days by readjusting the WFCS Institute of Construction Engineering and Management, 10 (2), to 50%. pp.75-84. Future study will analyze the enhancement of 18) Moon, H. S. Kamat, Vineet R. and Kang, L. S. (2014) Grid Cell- based Algorithm for Workspace Overlapping Analysis Considering productivity across construction works and analyze Multiple Allocations of Construction Resources, Journal of Asian major works that may reduce the productivity, such as Architecture and Building Engineering, 13(2), pp.341-348. steel structural works, civil works, etc. 19) Park, S. J. (2006) Work Flow Evaluation and Management Model To do this, case-based information on the for Continuous Performance Improvement in Construction productivity of the construction site should be required Projects, Dankook Univ. D. T. 20) Randolph Thomas, H. and Horman, Michael J. Ubiraci Espinelli to be collected and recycled in a database. Lemes de Souza, and Ivica Zavřski (2002) Reducing Variability to Improve Performance as a Lean Construction Principle. Journal of Acknowledgment Construction Engineering and Management, 128 (2), pp.144-154. This work was supported by the Dankook University 21) Randolph Thomas, H. Horman, Michael J., Edward Minchin, Jr. Research Grant in 2012. R. and Dong Chen (2003) Improving Labor Flow Reliability for Better Productivity as Lean Construction Principle. Journal of Construction Engineering and Management, 129 (3), pp.251-261. References 22) Rocha, Cecília Gravina da, and Kemmer, Sergio Luiz (2013) 1) Alarcon (1999) Playing Games: Evaluating the Impact of Lean Method to Implement Delayed Product Differentiation in Production Strategies on Project Cost and Schedule. University of Construction of High-Rise Apartment Building Projects. Journal California, Berkeley, CA, USA, Proceedings IGLC-7. of Construction Engineering and Management, 139 (10), pp.1-8. 2) Ballard, G. (2000) Last Planner System. A Dissertation of Doctor 23) Senouci, Ahmed B. and Eldin, Neil N. (2004) Use of Genetic Philosophy, Univ. of Birmingham. Algorithms in Resource Scheduling of Construction Projects. 3) Ballard, G. and Howell, G. (1998) Shielding Production: Essential Journal of Construction Engineering and Management, 130 (6), Step in Production Control. Journal of Construction Engineering pp.869-877. and Management, 124 (1), pp.11-17. 24) Tommelein, Iris D. Riley, David R. and Howell, Greg A. 4) Ballard, G. and Howell, G. (2003) Competing Construction (1999) Parade game: Impact of w ork F low Variability on Management Paradigms. Construction Research Congress, pp.1-8. trade performance. Journal of Construction Engineering and 5) Bashford, Howard H. Anil Sawhney, Walsh, Kenneth D. and Kunal Management, 125 (5), pp.304-310. Kot (2003) Implications of Even Flow Production Methodology 25) Walker, A. (1985) Project management in construction. Collins P. for U.S. Housing Industry. Journal of Construction Engineering And T. Books, New York, N.Y. and Management, 129 (3), pp.330-337. 26) Yu, J. H. Lee, H. S. Kim, S. K. Kim, C. D. and Suh, S. W. (2004) 6) Choi, J. (2012) A Knowledge Representation Model for Effect of Labor Factors on Work Flows. Architectural Institute of Formalizing Subcontractors' Scheduling Process, Journal of Asian Korea, 20 (4), pp.135-143. Architecture and Building Engineering, 11( 2), pp.275-282. 7) Han, S. (2010) Productivity Analysis Comparison of Different Types of Earthmoving Operations by Means of Various Productivity Measurements, Journal of Asian Architecture and Building Engineering, 9(1), pp.185-192. 8) Howell, G. Ballard, G. and Tommelein, I. (2011) Construction E ngi ne e ri ng—Re i nvi gora t i ng t he Di sc i pl i ne . Journa l of Construction Engineering and Management, 137 (10), pp.740-744. 9) Khalied Hyari and Khaled El-Rayes (2006) Optimal Planning and Scheduling for Repetitive Construction Projects. Journal of Management in Engineering, 22 (1), pp.11-19. 10) Ki m , C. H. a n d Ki m , C. D. (2 0 01 ) De v e l o p m e n t o f C PAM (Const ruc t i on Proc e ss Ana l ysi s Mode l ) ba se d on L e a n Construction Principle. Architectural Institute of Korea, 2 (4), pp.48-52. 11) Kim, D. Y. (2005) Deployment of Lean System for Effective Lean Construction Implementation. Korea Institute of Construction Engineering and Management, 6 (6), pp.152-160. 12) Kim, K. H. Kim, G. T. Kim, K. H. Lee, Y. S. and Kim, J. J. (2009) Real-Time Progress Management System for Steel Structure Construction, Journal of Asian Architecture and Building Engineering, 8(1), pp.111- 118. 13) Kim, Y. W. and Ballard, Glenn (2002) Is the Earned Value Method an Enemy of Work Flow. Brighton, United Kingdom, Proceedings IGLC-8, 2002. 96 JAABE vol.14 no.1 January 2015 Jaeyoul Chun http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Asian Architecture and Building Engineering Taylor & Francis

Improvement of Productivity through the Control of Continuity and Variation of Work Flow in Building Space

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© 2018 Architectural Institute of Japan
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Abstract

The majority of currently used construction productivity management systems rely on result-based management techniques, which have difficulties in managing in uncertain environments. Massive amounts of time and resources are wasted due to conflicts between works and constraints in space, etc. Hence, we need to recognize the limitations of existing result-based management systems and suggest a productivity management index that is expected to ensure that the issues of productivity reduction are properly controlled. Work flow refers to the progression of work in a limited time and space. Schedule delay and expense waste can be controlled by managing the work flow. Measurement of work flow is evaluated using 3 indices: Continuity Index, Variation Index, and Productivity Index. Therefore, this research suggests an evaluation and measurement system for work flow that shows the productivity of construction work both directly and indirectly, and thereby aims at an improvement in project performance by using a target index. Keywords: work flow; Variation Index; Continuity Index; productivity; Lean Construction 1. Introduction sites. Consequently, a reduction in productivity is often The productivity of construction work is influenced observed, such as discontinuous progression of works, by various factors including construction workers, delays in works, interference between works, and loss design documents, the nature of construction work, of materials. and external factors of construction, etc. In addition, Therefore, the various limitations of the result- the factor of uncertainties in the construction process based management approach currently used need to brings difficulties to project productivity management. be recognized and efforts need to be made to improve The occurrence of uncertainties in construction work such management practices. is inevitable since most current project management The concept of Lean Construction, in the context of systems operate in a top-down manner in which the productivity improvement, adopts the next generation lower level plan is determined by the upper level plan of procurement management technique, schedule (Tommelein, 2002). management technique, and performance management Researchers and site engineers in construction have technique based on productivity waste management. tried to develop appropriate methods of productivity Le an const ruct ion reduc es construction cost, measurement. (Han, 2010) The performance-based improves productivity, and thus aims to maximize productivity management techniques for a project customers' value by minimizing all ever-present factors provide unreliable outcomes on scheduling for a that may cause waste, which always exist during the project's stakeholders since they do not consider construction process. the environment of construction work that is Management of uncertainties by using the Last interdependent and has various uncertainties (Ballard Planner System (LPS) was recommended by the and Howell, 2003). Lean Construction Institute (LCI). However, the Inappropriate project management frequently causes LPS model provides a simple evaluation on the ratio inconsistencies between the planned work process and of the execution of the plan without the process of the actually executed work process on construction quantitative analysis. The weakness of LPS is that it allows neither the analysis of the productivity of the current works nor the proposal of a specific *Contact Author: Jaeho Cho, Research Professor, management goal. Department of Architectural Engineering, Dankook University, Hence, in the present progressive view, an objective 152, Jukjeon-ro, Suji-gu, Yongin-si, Gyeonggi-do, 448-701, Korea technique of measurement, evaluation, and control E-mail: cjhace@naver.com for productivity of work flow is required in order ( Received April 8, 2014 ; accepted October 31, 2014 ) Journal of Asian Architecture and Building Engineering/January 2015/96 89 to prevent issues of productivity reduction such as or to reduce the cost only upon the adoption of new schedule delay and excessive input of resources, etc. technology' since the model recognized the behavior of Approach methods in the context of work flow are production as a set of 'operation processes'. actively used in developed countries including the USA Koskela (1992) categorized the production process and some countries in Europe and are evaluated as into 4 steps including moving, waiting, operation, and successful methods. Also, the construction scheduling inspection, and thereby proposed a production theory technique has progressed drastically as scheduling that was understood by the cyclic process. software has become commercially available to project Variation of work flow in flow production theory participants. (Choi, 2012) was argued to worsen the waste in the production Therefore, this research proposes a method for the process and to lengthen the cycle time by increasing measurement of work flow that directly and indirectly non-value actions including moving and waiting. presents a productivity index of construction work. 'Variation' is the phenomenon caused by uncertain In addition, a work flow variation rating system is status. Ballard and Howell (1998) insisted that such proposed in order to support continuous improvement variation could be controlled by managing reliability. in performance on actual construction sites. In this They also argued that the method of approach used for study, the method of work flow measurement and case existing process planning 'was not able to ensure the analysis of the doctorate thesis written by Park, S. J. reliability of work order existing between works and (2006) is cited and re-analyzed. reliability in work flow.' Ballard (2000) recognized the limitation of project 2. Methods and Scope management when it is centered on result evaluation; A methodology for the measurement of work flow they therefore introduced concepts of flow production that indicates the productivity of the construction and LPS. Fig.1. below shows a fundamental concept process was proposed in this research. In addition, a diagram of the Last Planner System (LPS). case analysis was performed via the establishment of a system. In the case analysis, an improvement method for the performance of a project was offered by using a target control for Variation Index. This research was performed with the following procedure. (1) Discussion on related researches The direction of the research was proposed through investigations on literatures related to flow production theory, work flow variation, and work flow continuity. (2) Measurement method for work flow Various index functional formulas related to productivity were proposed based on the concept of Percent Plan Complete (PPC) and that of work flow evaluation. (3) Development of system prototype Fig.1. Concept of Last Planner System A prototype and operation process for the system was proposed based on the suggested measurement LPS differs from the traditional management system method. that was processed in a work order-centered manner. (4) Validation through case study The works documents should be performed ('Should' in Work flow variation was measured based on works Fig.1.) in a work plan, confirming the work order ('Will') on an apartment housing unit and an improvement based on the constraints that the workers are able to method was proposed by setting the target index. perform ('Can'), and check the execution status ('Did') (5) Conclusions through Percentage of Plan Completed (PPC). The results from this research are summarized and a LPS is the method of productivity management that method for future studies is proposed. is able to control the variations in plan by execution. Ballard and Howell (1998) emphasized the 3. Discussion on Related Researches importance of variation control in a construction Wa l k e r ( 1 9 8 5 ) i n t r o d u c e d t h e c o n c e p t t h a t production system by mentioning that "The first goal "Production process is the conversion process of input of Lean Construction is to understand the dynamics elements including resources, labor, and equipment to of construction production, the influence of mutual output elements as products" from production theory interdependency and variation in resource procurement of the existing manufacturing industry to productivity and production chain". analysis in the construction industry. In Parade Game, Tommelein (1999) analyzed the Koskela (1992) identified the limitation that influence of variation in work flow on the performance 'Walker's model was able to improve the productivity of the entire project through simulation and confirmed 90 JAABE vol.14 no.1 January 2015 Jaeyoul Chun the increase of stock occurring between works and 4. Control of Productivity Variation time delay due to higher variability. The variation of work flow can be distinguished Alarcon (1999) evaluated the influence of variation as the variation of labor work and that of work in in work flow on the cost and schedule of the project space. The difference between the execution plan and through a simulation called Playing Games. the completion work is developed while conducting Kim (2001) understood the Lean Principle that operation management on site. "Enhancement of reliability in schedule management Establishment of successful productivity and contributes improvement in work flow, productivity, continuous improvement in productivity are possibly and quality" and proposed a schedule information achieved when the Continuity Index of space work are model that can be utilized in the detailed planning controlled within the range of target management. stage and a subsequent method for variation control. The weakness of the existing LPS is that it does not Thomas (2003) analyzed the data of an inefficient present the analysis on productivity in terms of the work process through investigation of a case project, work continuity for currently ongoing work. and verified that the enhancement of reliability on The productivity can possibly be improved by labor flow contributed to improved productivity. securing the work continuity since the work continuity Bashford (2003) proposed two methods of uniform serves as a management index indicating an optimal work, one based on a single unit task and the other productivity of currently ongoing work. Hence, this based on a start point, as strategies for securing the study grafts a concept of variation management for work continuity by recognizing the similarities existing labor work and work in space onto LPS in order to between the manufacturing industry and construction analyze the factors decreasing productivity and control works. the work continuity (Refer to Fig.2.). Yoo (2004) presented the labor factors among the The schedule manager can reset the achievable factors influencing both work flow and its continuity target in the present progressive view by using a and proposed indexes listing the measurement of such variation index for work flow. This directly leads to the labor factors. In addition, the correlation between improvement in productivity. continuity of work flow and labor factors was analyzed Low continuity of work can be reflected in the through correlation analysis. improvement in productivity by workers on site by Kim (2005) proposed detailed guidelines for adjusting the resources since it indicates the work management as an operation method for a Lean System problems on site. in order to effectively perform Lean Construction in the domestic industry. Lee (2008) proposed a method of schedule delay analysis using learning effect and linear scheduling since cessations and changes of works in the construction industry cause reduction in productivity. Moon (2009) suggested an evaluation method on Percent Plan Complete (PPC) with consideration given to the variation of work flow. Ki m ( 2 0 0 9 ) p r e se n t e d a r e a l - t i m e p r o g r e ss management system for steel structure construction. Cecília Gravina da Rocha (2013) conducted an analysis on the causes of delay in works by using a Line of Balance (LOB) technique. As listed above, numerous studies aiming at improvement in inefficiency and low productivity in the construction industry by controlling variation and Fig.2. Control of Productivity Variation continuity of work flow have been reported through LCI and the International Group of Lean Construction 5. Measurement for Work Flow Indexes (IGLC). In this section, the concept of the PPC and the work The authors' discussion on existing studies indicates flow measurement for enhancement of productivity in that consultations at a stage prior to the execution construction work will be explained in terms of flow and analyses of constraints on space for the purpose production. of the management of uncertainties in construction First, the PPC presents the degree of achievement sites can enhance reliability of the plan. However, compared to the planned target and refers to the ratio difficulties arise in tracing the productivity of works of the current status to the ideal (the best target) that are currently ongoing and setting a target variation st a t us. Cont i nuous i m prove m e nt c a n be re a c he d index due to the absence of a quantitative method for by continuous removal of possible causes that may measuring the status of a plan by execution. impede moving forward from current status to ideal JAABE vol.14 no.1 January 2015 Jaeyoul Chun 91 WT (x,y): Number of days for waiting in space j where the status. For evaluation using the PPC, the ideal status in i,j work of 'i' is possibly done during measurement relation to the given condition is measured, followed period (date x ~ date y) by the measurement of current status. In this research, continuity and variation of work The Variation of Work Flow (VWF) increases the flow are measured by using the concept of PPC. By 'non-value actions' during the construction process, comparing the variation of work flow in the current resulting in lengthening of cycle time and reduction of status and that in the ideal status, the process and production capacity. Hence, it is measured in order to causes that lead to current productivity are measured. control such results. Furthermore, the users can improve productivity Such variation can be classified into Variation of Input continuously by setting appropriate target indexes. Resource (VIR) and Variation of Operation Process In business, there is an oft-repeated statement: (VOP) ba se d on t he be ha vi o r of t he produc t i on. "If you don't measure it, you can't manage it"; The variation in input resources can be measured the productivity-related-index that quantitatively by analyzing the changes in planned input resources presents the current status is essential to effectively during a planned period of specific work. The amount managing the production system in construction. The of VIR can be expressed by the formula (4) below. measurement indexes systematically present the target to be achieved in the project, and provide a quantitative level of achievement. The properties of work flow …………….……....(4) include Continuity Index and Variation Index, and the VIR (x,y): Variation in input resources of work 'i' during work measurement methods for each index are as follows. period (date x ~ date y) The CWF (Continuity of Work Flow) is classified th IR : Amount of input resources at n work day of work 'i' i,n into Work Flow Continuity in Space (WFCS) and Average amount of input resources during work 'i' Work Flow Continuity on Work (WFCW). The WFCS AIR (x,y): period (date x ~ date y) means the degree of sequential execution without spare time or waiting time in each work per unit space. This The direct comparison of VIR between different can be expressed as the following formula (1). works or different projects is impossible since the VIR changes with the amount of planned input .........................................……………….(1) resources. For standard comparison, the Coefficient of WFCS: Work Flow Continuity in Space Variation in Input Resource (CVIR) of subject work CSW: Count of Space on Working classification can be measured by calculating the TCSW: Total Count of Space on Possible Working function in the formula (5) below. The Continuity Index for ideal work space is 100%, ………...……………………(5) meaning that the work is in progression in every work VOP is the variation of execution in relation to the space where the work is possibly performed. plan. It is called PPC in LPS and is used in LCI. In this The WFCW means the degree of sequential study, it is defined as the variation in the amount of execution of a work. The number of days for waiting work (labor). The value of such variation is obtained is measured based on every space in which the work by dividing the planned amount of work by the actually of 'i' is in progression 'for a certain period'. This can be executed amount of work. expressed as the following formula (2). It is also used as performance indicators that ………………….(2) measure the reliability of the subject work. The VOP is expressed as the formula (6) below. WT (x,y): Number of days for waiting in work 'i' during measurement period (date x ~ date y) AWA (x,y): Actual number of days for work in work 'i' during measurement period (date x ~ date y) ………………….……….…(6) NWD : Number of days on which the execution was x,y VOP (x ,y ): Variation in operation processes of work 'i' performed i,j j j impossible due to non-manageable factors including at 'j' space during work period (date x ~ date y) weather during measurement period (date x ~ date y) th NPW : Amount of work that was planned for n work day at i,j,n 'j' space WT (x,y) is defined as WFCW (Work Flow i,j NDW : Amount of work that has been actually executed on i,j,n th Continuity on Work). The ideal WFCW value is '0', n work day at 'j' space meaning continuous execution of work without waiting days during the measurement period. This can be The direct comparison of VOP between different expressed as the following formula (3). works or different projects is impossible since the VOP changes with the amount of work space. Coefficient of Variation of Operation Process (CVOP) for subject ………….….…………………...(3) 92 JAABE vol.14 no.1 January 2015 Jaeyoul Chun work can be measured by calculating the following 7. System Prototype formula (7). Developing a system that allows for automation of input/output information and the integrated operation of an application program is required in order to measure work flow and effectively perform …………………………(7) productivity management. In terms of developing In general, productivity refers to performance and it a system, the present study is confined to the is 'Productivity = Output/Input'. The productivity used measurement for construction work flow. in this research was mainly focused on productivity in Basic information on the work plan is provided by relation to labor. The amount of Productivity Variation the Project Management Information System. Schedule (PV) can be obtained by calculating the following analysis and causal analysis for schedule delay are formula (8). supported by the Schedule Management System and LPS. Statistical analysis is performed by SPSS, the statistical analysis program. Each system provides ………………………………..(8) a unique function according to its own purpose and PV (x,y): Amount of variation in productivity of work 'i' during i interoperates with the Work Flow Evaluation System work period (date x ~ date y), (WFES) prototype in this research. LP : Productivity of work 'i' i Practically, the WFES suggested in this research ALP (x,y): Average productivity of work 'i' i allows mutual interoperation by using data tables in MS-EXCEL. For standard comparison, the Coef ficient of The operation algorithm for the system is as the Productivity Variation (CPV) can be measured by following Fig.4. Initial plan (Should) and feasibility calculating the following formula (9). plan (Can) are prepared based upon the schedule program. Next, action plan (Will) is determined through discussion between the stakeholders for …………..………………………...(9) rationalization of schedule planning. Once an action plan is determined, variation in work flow and 6. Relationship between Work Flow and Productivity continuity of work flow are measured by utilizing A higher continuity of space means a sequential the WFES system on work flow from the present progression of multiple works in a limited space. This progressive point of view. reduces the duration of the construction along with a Work flow is assessed by evaluating the earned value reduction in variation in work load. for continuity in space. The subjects of evaluation such A greater continuity of work means the reduction of as work flow continuity in space, labor efforts, and variation in input resources through continuous work variation are measured based on the concept of PPC. and improvement in productivity upon learning the Causes of delay are determined by analyzing Variation effects. Index and enhanceable productivity is predicted by As a result, the reduction of variation in work flow adjusting a target variation index. greatly influences the construction duration. The influence of continuity and variation of work flow on productivity is schematized and shown in Fig.3. Fig.4. System Operation Process based on CWF and VWF Fig.3. Relationship in Variation of Work Flow and Productivity JAABE vol.14 no.1 January 2015 Jaeyoul Chun 93 Table 1. Results of Work Flow Measurement (Formwork) Date Production (m ) Labor (crew) Labor Productivity (%) A_IR CVIR WT 5.02~5.08 12,194 158 77.17 23 39.9 14 5.09~5.15 11,894 174 68.35 29 44.8 13 5.16~5.22 14,563 192 75.84 32 42.7 14 5.23~5.29 14,317 210 68.17 30 45.0 11 5.30~6.05 14,155 214 66.14 32 46.0 11 6.06~6.12 14,527 164 88.57 27 34.1 12 6.13~6.19 14,344 189 75.89 32 40.7 15 6.20~6.26 14,438 158 91.37 26 34.2 16 6.27~7.03 13,633 157 86.83 31 36.7 12 7.04~7.10 14,498 156 92.93 26 33.3 16 7.11~7.17 12,803 173 74.00 29 41.2 10 7.18~7.24 13,716 170 80.68 28 40.0 14 8.08~8.14 11,947 121 98.72 20 32.2 16 8.15~8.21 12,524 146 85.77 24 37.4 12 8.22~8.28 14,215 148 96.04 30 27.3 8 8.29~9.04 14,802 150 98.67 25 16.0 17 9.05~9.11 13,124 194 67.65 32 42.3 12 9.26~10.02 9,528 126 75.61 21 39.7 16 10.03~10.09 10,108 124 81.51 21 38.2 11 10.10~10.16 10,083 128 78.77 21 40.6 12 10.17~10.23 12,719 129 98.59 26 20.8 9 10.24~10.30 11,815 121 97.63 20 14.3 14 10.31~11.06 12,813 142 90.22 24 35.2 10 11.07~11.13 11,755 122 96.34 20 27.9 12 8. Case Study In this section, the measurement method for work flow is validated through case analysis and field applicability is reviewed in the WFES. For the case study, data on formwork scheduling and its execution status was collected from the case construction site of a construction firm. Variation and productivity were measured using the measurement technique. Table 1. shows the results of work flow measurement of the formwork. Input labor and productivity were measured on a daily basis. And these were aggregated again on a weekly basis. Approximately 32% of the difference between the minimum labor productivity of 66.14% and the maximum labor productivity of 98.72% was presented. (1) Evaluation of VIR The VWF was categorized into VOP and VIR. For the self-variation as VIR, variation in labor effort, and variation in productivity were measured for the subject work within a certain period. Fig.5. below shows an example of the measurement of VIR (5.73) and CVIR (46.54) for Laminating Work. (2) Improvement in productivity by using WFCS The duration of construction work is predicted by CWF and the improvement effect of productivity is estimated by adjusting the VIR and the VOP. The prediction of duration for the construction work can Fig.5. An Example of Measurement of VIR and CVIR be obtained by adjusting the WFCS. Fig.6. shows the WFCS measured as 41.67% over 27 days performed axes of the cell in Fig.6. represent the space and the th th from the 7 floor to the 10 floor of an apartment days of work, respectively. housing unit. At this point, it was predicted that the (3) Improvement in productivity by CVOP adjustment of WFCS to 50% could reduce the work For prediction of productivity, the CVIR, the CVOP, duration by 4 days (Fig.6.). The vertical and horizontal and the CPV were measured once after the selection 94 JAABE vol.14 no.1 January 2015 Jaeyoul Chun Fig.6. Prediction of Construction Duration through Adjustment of WFCS in Finishing Works evaluated the continuity of space work by accepting the execution plan and completion data on site from the interface system. On-site-engineers can reset possible productivity by controlling a variation index. This study took an academic approach to the concept of LPS productivity in view of site monitoring. The concepts of WFCW and WFCS per unit space were proposed as the information model for productivity Fig.7. Productivity through Adjustment of the CVOP improvement. WF CW and WF CS are the major of duration of work for the subject work. Formula (7) elements of the productivity variation. In the case of was applied in order to calculate the CVOP. The CVOP space work, variation in continuity of space work is of the target index was reset based on the analyzed inevitable since multiple works are conducted in one coefficient of variation in order to estimate the constrained space. Moving to another space or waiting improvement effect. In the case of the construction site should be ordered when conflict among two or more in this case study, the CVOP was measured as 26.64 works in the same space occur. by measuring the variation of work flow for concrete In this study, the status of multiple works in space th work during 6 days between October 17 and October and the management index on information systems nd 22 2010. Improvement in productivity by 16.83% were proposed in order to prevent reduction in was estimated by lowering the CVOP concerning labor productivity and schedule delay. Furthermore, the effort to target level 10.0. Fig.7. presents the prediction developed WFES allows determination of the factors of productivity through the adjustment of variation on decreasing productivity since it promptly provides the the construction site of the case study. information of variation in continuity of space work. The principal results obtained from this research are 9. Conclusion summarized as follows. This study proposed a method for improvement in (1) This research suggested a measurement method productivity by measuring the variation in continuity for continuity in space, continuity in work, and of work flow and controlling this variation in the space variation in relation to work flow in the construction where construction work is repeatedly conducted. It is phase. Work flow presents the operation process possible to determine whether the productivity of work of work in a limited time and space and the factors is progressing effectively or inappropriately by using causing schedule delay and productivity reduction can the Variation Index and Continuity Index of work flow. be prevented by managing the variations related to Existing studies were not able to propose a method work flow. for improvement in productivity in the present (2) The continuity and variation in work flow progressive view since these studies evaluated changes with sensitivity upon the adjustment of input productivity of completion versus execution plan as resources and work (labor) effort. they focused on analyzing outcomes. (3) The system prototype in this study enables For commercialization, this study reviewed the measurement of WFCS, WFCW, and VWF. This on-site-applicability through a case study. 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Brighton, United Kingdom, Proceedings IGLC-8, 2002. 96 JAABE vol.14 no.1 January 2015 Jaeyoul Chun

Journal

Journal of Asian Architecture and Building Engineering – Taylor & Francis

Published: Jan 1, 2015

Keywords: work flow; Variation Index; Continuity Index; productivity; Lean Construction

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