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RF2268AM - CONSTRUCTION PRODUCTIVITY MEASUREMENT: A COMPARISON OF TWO CASE STUDIES 3
دوشنبه 29 فروردین 1390

CONSTRUCTION PRODUCTIVITY MEASUREMENT: A COMPARISON OF TWO CASE STUDIES 3

   نوشته شده توسط: عارف محمدی    نوع مطلب :مدیریت منابع سازمانی ،

To overcome the problems discussed in the previous section regarding the isolation of construction activities in measuring productivity, a decision was made to measure productivity levels using the existing company worker timesheets. Timesheets were found to be extremely useful mainly because timesheets were used for the purpose of calculation of hourly wages and linking this to productivity measurement would probably show meaningfully the notion of a fair wage. Furthermore, measuring productivity on a daily basis was considered to be the most appropriate technique as corrective action could be taken as quickly as possible. For data collection purposes, foremen were instructed to complete time inputs and physical outputs for each worker under their charge within a set time sheet on a daily basis. Table 1 below shows a simplified example of a recording on the activity of pouring concrete by a gang of concrete labourers. Based on the data presented in table 1, a total of 66 man-hours were used to produce 232m3 of concrete, yielding a productivity rate of » 3.5m3 of concrete per man-hour.

 

Date

Worker

Activity

Hours

Location/Output

1 Oct 2001

Foreman A

Pouring Concrete

10

Plot 2-6/ 232m3

1 Oct 2001

B, C, D, E, F, G, H

Pouring Concrete

8 each

Plot 2-6/ 232m3

Table 1: A simplified example of a completed time sheet

 

Emerging issues

A number of issues arose whilst attempting to measure on-site productivity levels for project A in this way. The desire for a speedy construction process meant that many proprietary systems, e.g. in the case of formwork, were used as part of the construction techniques. These were undertaken by specialist subcontractors (with whom access was not granted). What was observed was that the core labourers used by the main contractor were general operatives who were often mobile in terms of the task they did. So, for example, an operative could be involved in general housekeeping on day n, shifting what is known as ‘tables’ (a proprietary form of the conventional birdcage scaffolding that is on wheels to support the formwork) on day n + 1, and putting stop ends along the perimeter of a plot prior to concreting to prevent the concrete from spilling over on day n +2 and so on. Perhaps the only stable groups of workers were those who were relatively more skilled, e.g. concretors and steelfixers, who tended to stick within the task of their trades. Even so, these workers moved to other projects in the vicinity when their tasks were not scheduled for project A. Therefore, while measuring productivity levels in this way appear to be more holistic and probably closer to reality than the methods highlighted in the previous section, the mammoth task of tracking workers posed an immense challenge. Moreover, although the data was collected at the gang level (through the foremen), the boundaries of the gang were found to be arbitrary because of the volatile movement of the workers. This resulted in high variability of the productivity data obtained, which supports Radosavljevic’s and Horner’s (2002) observations, but which implies that discerning the factors affecting productivity especially those related to the workforce issues was particularly problematic.

Administering the measurement was also not without problems. To start with, foremen were not akin to filling out forms and throughout its implementation, the project quantity surveyor discovered that there was a need to constantly explain to the foremen the mechanisms of recording. Two reasons accounted for this. The first relates to the inevitable problem with determining output quantities given that construction operations are often associated with work-in-progress that can be difficult to ascertain. Rules of credit (see e.g. Thomas and Yiakoumis, 1987) may go some way to facilitate this process, although time and manpower is needed to maintain a database of such information for which the project quantity surveyor did not have. In fact, the project quantity surveyor resigned in the middle of the project and the measurement of productivity halted due to the absence of a willing successor. To exacerbate the problems of measurement, the project quantity surveyor had identified a complex list of more than 170 task descriptions, thus causing further confusion for the foremen in the recording process. This enormous list of task descriptions is believed to be due to the fact that many proprietary systems were used in the construction process. Still, as the predicted trend for the construction industry is towards greater outsourcing and use of innovative technology in the production of buildings (see e.g. CRISP, 2001), it would be sensible to take into account such complexities when measuring productivity. It is here that project B sheds some light.

 

Project B: Headquarters of a Commercial Bank

 

Background to project B

Project B involves the construction of the headquarters of a commercial bank on a greenfield site just outside Edinburgh. Access was given to interview senior project managers and to conduct questionnaire surveys with the site operatives. During the interviews, the researchers were struck by the ability of the managers to report what they allege to be the precise number of man-hours expended on the project to date, a phenomenon that was non-existent in other projects observed during the study. Inquisitively, the researchers investigated how project participants captured this data through further probing during the interviews.

 

Figure 1: Extract of project B work package 1 planning and progress update up to week 41

 

According to the project managers, project B utilised what is known as The Last Planner system, a planning system that has gradually gained recognition and refinement since its inception in 1994. Much has been written about the system (see e.g. Ballard, 2000), although this is really related to planning and never intended to be used as a means of measuring on-site productivity. However, one of the KPIs resulting from this system, known as the Percent Plan Complete (PPC), was thought to be extremely valuable by the project participants for them to gain an informed view of the on-site productivity levels. Basically, the PPC refers to how much of the planned work on a weekly basis is actually completed. In a similar vein, this ostensibly is comparable to the earned value analysis used in project management (see Project Management Institute, 2000). Figure 1 above shows an extract from a weekly progress update, which enables project B’s participants to keep track of how productively the work packages were performing to plan. To help improve the PPC, the progress meetings were used as a platform to understand what went wrong, i.e. what intervening events or factors resulted in a low PPC (e.g. weather, lack of materials etc.).


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