COMPUTER AIDED PRODUCTIVITY MEASUREMENT A UNIFIED PRODUCTIVITY MEASUREMENT METHODOLOGY

INTRODUCTION

Construction industry is as diversified as the uses and forms of the many types of structures that it produces. However, three general categories can easily be identified, although there is some overlap among these categories. The three main categories [1] in construction are: I. Heavy engineering-­highway, airport, dam, etc., just to name a few. II. Industrial construction--refinery plant, utility/power plant, steel mills, etc. III. Building construction--sometimes this category is further divided into residential and non-residential buildings. Apartment and single family houses are residential buildings. Buildings for other purposes such as educational, commercial, religious, social, and recreational are non­residential buildings. The productivity information gained in one category of construction is very hard to compare with other category if not impossible. Therefore, if a unified productivity measurement methodology can be adopted by the industry the benefit is obvious.

PRODUCTIVITY MEASUREMENT TECHNIQUES

The productivity measurement is an industry wide problem in the execution phase of a construction project. It has a strong effect on project control. No meaningful and valid comparison among different projects should draw more attention from productivity researchers. The greatest barriers to successful research are confidentiality of the job site data and research funding. No company will share its payroll/produc-tivity/estimating strategy with anyone else. The individual hourly rate for carpenters in the same area is the same for all the union contractors, yet no two contractors will provide the same price for a carpentry job. The difference is the productivity rate and method adopted for estimating the productivity.

Some techniques for measurements of productivity have been proposed in the past two decades. Heney N. Parker and Clarkson H. Oglesby [²] proposed stopwatch studies, time lapse motion pictures, work sampling, activity sampling, five-minutes rating etc. The common advantage of all these techniques is that it can provide more timely information about job site productivity.  The common disadvantage is that it is not as objective and accurate as the man-hour report. Borcherding [3] conducted extensive study about productivity, mostly on nuclear power plants , by using questionnaires. The problem with questionnaires is that sometimes the researcher gets ridiculous answers from persons filling it. Such as, in a eight-hour working day, how many hours do you spend on waiting for materials --- answer is 10 hours. These answers are not the worst ones yet, because they will be excluded from the study. The worst ones and most damaging ones are those which are unlikely to happen but could be true ones. To exclude or not to exclude that questionnaire depends on the subjective judgment of the researcher. Therefore, the results of any questionnaire study could be biased in some degree.

Another overriding concern of the construction industry is the inability to establish valid and meaningful comparisons among different projects completed over different times in different categories of construction. The difficulty in data collection is one of the problems. Lack of uniformed format of collected data is a much more severe problem. It is generally agreed that quality research could ultimately effect the project duration, productivity, and resource usage. However, only provided with meaningful, timely collected, comparable against each other, and objective data can anyone achieve the research goals. Partly because the nature of the construction industry that it is extremely difficult, if not impossible, to compare the same product under different working environment. The man-hour needed to pour one cubic yard of concrete in a nuclear power plant is certainly different from that needed for the foundation of a two bedroom house again is different from mass concrete dam. How to compare these productivity figures to decide the efficiency of a project is a major concern facing construction productivity researchers.

Work sampling could be a method that potentially could provide quick and reliable estimates on site productivity. However, some statistical methodologies must be developed to isolate those factors with influence work samplings results. Therefore, a standardized method needs to be established to collect only comparable data among different projects completed through different geographical area and time. Or, some methodology needs to be used to draw a conclusion from work sampling study so that the unit rates or other productivity measurements can be assessed without the bias from environmental factors such as temperature, type of work, size of project etc. Comparability of data in the construction industry is one of the most critical problems that needs to be solved. The owner, designer and contractor are all eager to know if the job is done fast, within the budget and with good quality. These questions usually can not be answered until the job is done. The need for a methodology to identify the problems or potential problems during the early process of construction is obvious.

STANDARDIZED PRODUCTIVITY MEASURE­MENT

Traditionally, one method is to use all the man hours reported from the field office, comparing it with the amount of job completed for that period of time. This method can gather very reliable results but the information always reaches the management too late. Usually too little information is reported too. Only hours spent on job and percentage of job completion are reported. Management needs to know more about field situation and needs it fast. The other extreme is to use more subjective methods such as five minutes rating, work sampling, etc., to get early information. But this end of the productivity measurement is not as accurate as expected. A lot of data is gathered through subjective judgment. For example, there is no clear-cut definition among idle, productive work, indirect work, ineffective work, etc. Therefore, two persons evaluating the same job site may get quite different results for the same period of time.

Value added approach to productivity measurement has the potential to become the standardized method in measuring the productivity of the on-going project. The capacity of the micro-computer and its ability in storing data and transferring information among different places has much potential in the construction industry by greatly speeding up the counting and arithmetic operations. The computer system allows the contractor or productivity measurement party to get timely results. In turn, using the results in early stage of the construction process to prevent problems from disaster. The management can get early warning signals to be alert. The second major property of the computerized system is its accuracy. If a standard method of measuring productivity can be developed in conjunction with computer system, we can analyze large amounts of raw data without incurring any errors. This is very important when data is collected on a daily or weekly basis, and the results are needed within a short period of time.

Construction businesses have utilized microcomputers in the few years they have been available. This has caused more dramatic impact on productivity than any powered tool or equipment item ever invented. The construction information to be distributed by computer can take a variety of forms. They include, but not limited to, the following:

This paper proposes the using of micro-computer and telephone lines to distribute/transfer field productivity data to the main office. The data will be collected/updated daily. The proposed method in this paper is to combine the advantages from both ends to get objective, reliable results at the early stage of job performance. The method itself must be simple enough so the foreman, journeyman, and contractors can all understand it. The data collected by this method should be uniform in a standard format so the results can be compared for different projects completed in different parts of the country at different times. Simplicity is one of the major considerations of any construction productivity data collection. We shall always keep in mind that the majority of people working in the field don't have much education. They learned their trade through experience. If there is a lengthy form or questionnaire for them to fill, we should not expect too much accurate or useful data to be collected. They do not have the reading/writing ability, nor the patience. To collect first-hand productivity information, the following things shall be avoided whenever it is possible--lengthy form, subjective judgment, vague definition, lengthy writing description [4]. The method proposed in this research avoided all the pitfalls mentioned above. The data collected is also comparable with other projects because the format is standardized.

PROPOSED METHOD FOR STANDARDIZED PRODUCTIVITY MEASUREMENT

A simplified step-by-step procedure of this Value-Added­Productivity-Sampling is:

CONCLUSION

The key to success of any job site productivity measurement is simplicity and timely results. The value-added productivity-sampling proposed in this paper can be used to achieve both goals. Timely results are attained because the transfer and calculation of productivity information is done by personal computers automatically. Also, the only hardware needed are personal computers and telephone lines which most contractors have purchased in the past already. No new cost for the contractor. The simplicity of this method is obvious because only one page of data is collected each time of observation and only largest twenty items are measured. The subjective judgment of researcher is largely excluded because counting heads needs no judgment. The bias inherent in most productivity measurement techniques is therefore minimized. This method could be a standard productivity measurement data collection technique for construction industry. The research of collected data must be performed with meaningful comparison among different projects. This goal is attained because data collected is in the format of ratios.

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