Journal of Construction Engineering and Management

In the past decade, considerable research effort has been devoted to alleviating site productivity problems in Taiwan's construction industry. However, the results generated so far are frustrating. A school of academic debates are raised concerning the elements missing from the research framework adopted. The disregard of the crucial role played by subcontractors in the construction process is the main missing element. To gain a thorough understanding of the subcontracting practice in construction, an extensive questionnaire survey targeting more than 1,000 general contractors, selected at random, was conducted in 1995. Major findings of the survey are reported briefly in this paper. The relationship between subcontracting and site productivity was investigated. A conceptual model for analyzing productivity barriers due to subcontracting was developed and various aspects of this model were also examined. Based on the insights gained from the survey and the follow-up interviews, three promising institutional strategies for overcoming the identified productivity barriers are presented and discussed.

Bid decisions by subcontractors are complex due to the uncertainty about many factors affecting their outcomes. This study was able to identify, through a questionnaire survey, many factors characterizing the bid decision-making process. The questionnaire was mailed in August 1995 to 320 subcontractors in Colorado. The results indicate that the contractor's credit history, habit in the issuance of periodical payments, and leadership and capability in planning and managing the project are identified as the top factors that affect a subcontractor's decision to bid for a project. The subcontractor's previous relationship with the contractor, the contractor's capabilities, financial capacity, current work load, and specialty, and the prospect of future business relationships are the highest ranked factors affecting quotation decision. Suggestions are advanced to subcontractors for improving their bidding decisions.

This paper discusses an approach that was developed to enable effective use of systems simulation in the scheduling of construction projects. The approach was implemented in a software program named SimCon, which enhances current simulation methods through the use of continuous production links for activities that comprise a project. The continuous production links provide construction managers with a flexible representation of activity sequencing. The procedure builds on existing CYCLONE fundamentals through new constructs to connect processes in a simulation-based project plan. These constructs are used to simplify the cyclic interprocess relationships, standardize the techniques for logical linking of simulation processes, provide a better estimate of progress, and model a continuous and smooth flow of construction. Various scheduling alternatives are modeled without the need to change activity sequencing, as is required in current scheduling systems. Examples from an actual construction project show the advantages of the continuous production links. The concepts are implemented using a prototype computer system that integrates object-oriented concepts, event-driven programming, a relational database, and a simulation system.

A study was made in the early 1990s of the utilization of labor and equipment resources in the in situ concreting of buildings in Hong Kong. The study involved close observation of 154 pours on building construction sites and 38 days spent at 38 ready-mixed concrete (RMC) batching plants, one day at each. Much detailed productivity information has been derived and the different concrete placing methods have been compared. Other factors affecting the placing rates, pour size, type of pour, and supply of concrete have also been studied. Benchmarks, which describe the state of the industry in broad terms, have been produced not only for measuring progress in the standards applying in Hong Kong as time goes by but also for making comparisons with other large cities.

Today's projects suffer from high uncertainty, great demand for accelerated speed, and severe scarcity of attention of the project manager. At the same time, the schedules of today's projects are expected to be more reliable than ever. This paper presents a new concept for improving the reliability of a project schedule suffering from uncertainty in the duration of its activities. The paper shows that the technique for applying the new concept requires minimal information, incorporates subjective information, is simple to use, and assists in the preparation of project schedules at a desirable level of reliability. Specific examples demonstrate the use of the technique for: (1) calculating the reliability of the project schedule; (2) enhancing the reliability of the project schedule; (3) reducing project duration without diminishing its reliability; and (4) examining how overlapping of project activities affects its reliability.

In recent years there has been a move away from methods and material specification for pavement projects and toward end product specifications (EPS) as part of a general improvement in quality assurance programs. Typically, the EPS are based on the average of a number of measurements on a given day, and the between-test variance and the between-days variance are ignored. This paper presents a methodology for identifying the components of the total variability, estimating the variance associated with each component, and identifying the responsibility of each component to overall variance. The total variability and individual component variability may be used for a number of quality assurance applications—for example, identifying potential problem areas in the construction of a particular pavement, as input to new end product specifications that account for the variability in the measured results, or for aiding in setting appropriate bonus/penalty schedules, which are typically used in conjunction with EPS. The statistical approach adopted in this paper is a nested analysis of variance and the methodology will be tested on five years of data from an EPS program in the Province of Alberta, Canada. Data are from Marshal density and field density tests of asphalt concrete, although the procedure may be used for any EPS field test.

In the past 10 years a number of transportation agencies have adopted end product specifications (EPS) as part of their quality assurance programs. The basic premise behind EPS is that the contractor is remunerated based on how well their final product meets specifications set by the transportation agency. For example, an EPS for asphalt concrete pavement might state that the field density should be within 97% of the Marshall density. If the field density is below this value, the contractor would receive a penalty, whereas if the field density is above this value the contractor would receive a bonus. Because of uncertainty regarding the exact relationship between the reduced (or increased) performance of the product and the measure of effectiveness, the price adjustments were established based on engineering judgment and were indirectly related to anticipated performance. For example, the transportation agencies pavement engineers would look at past performance in developing guidelines for what reasonably could be expected for a given EPS. However, the fact that many agencies collect and save EPS data means that the variability in the EPS may now be analyzed and the effects studied. This paper demonstrates how the data collected from an EPS, and in particular the variability measures identified from these data, may be used to identify optimal testing strategies and to identify the risk, to both the producer and the agency, inherent in the bonus/penalty schedules. In addition, the trade-off between sample size and testing accuracy will be demonstrated. Last, the implications of incorporating variance within the EPS will be explored. Data obtained from Alberta Transportation and Utilities on Marshall density and field density EPS measurements will be used to illustrate the methodology and demonstrate the key components of the paper.

Environmental issues are becoming an increasingly important consideration in the design of a facility. In many cases, a facility's life cycle must now include a disposal phase that addresses the facility's physical removal from its present site, with the site being returned to its “natural” condition. If the disposal phase costs are identified as a significant portion of the facility's overall life-cycle cost, the owner can initiate a balance between functional requirements and disposal requirements early on in the facility's planning and design phase. This paper discusses the development of a model that qualifies and quantifies a facility's final disposal cost. Life-cycle cost equations are formulated to quantify the disposal phase costs. During the facility's life cycle, the owner will be able to revise the costs in the model to reflect the facility's changing conditions, track the changes in the disposal costs, and assess the causes for these changes. Owners are thus empowered to take a more proactive role in controlling the identified adverse changes.

In line with the economy reform program, competitive tendering methods have been introduced to the Chinese construction industry to supplement and gradually replace the past assignment system for the procurement of construction projects. The major objectives of applying the competitive methods are to improve the effectiveness of construction investment and to develop the Chinese construction market toward the international procurement practice. This paper examines the development of competitive tendering practices in the Chinese construction industry, particularly in the more developed regions. It presents the characteristics of the tendering practice within the special environment where the national economy system is being reformed from a purely planned system to a market-oriented system. Outstanding problems in the development of tendering practices have also been investigated. A constructive survey and an in-depth discussion from Chinese academic institutions and governmental departments are used to support the analysis. The study provides a strong indication of the potential development of a competitive tendering system in China.

The goal of this research was to develop and illustrate a technique for finding the optimum crew configuration, from a range of possible configurations, assigned to complete a defined quantity of work in a timely and cost-effective manner. The concept of activity-based costing was used to define the scope of the work in terms of the activities to be accomplished and their associated productivity rates and cost of performance. These data are modeled as distributions of random variables. Past experience, as well as local job conditions, can be used to determine the values associated with these distributions. The temporal and logical relationships between the activities are established through a process flowchart. An activity based, stochastic simulation program (ABC-SIM), was used to measure the elapsed time and activity cost for each of the candidate crew configurations. Excess cost is the activity cost minus the shift cost, which is based on the number of full shifts required to accomplish the work multiplied by the cost per shift. Excess cost is a measure of inefficiency caused by crews waiting in queue. Finally, an optimum crew configuration can be selected using an optimization rule that best satisfies project objectives.