Journal of Construction Engineering and Management

This paper describes an economic evaluation that determines the value to the user of a fully automated rebar computer-aided design/computer-aided manufacturing (CAD/CAM) system. That value is $167,000, rising to more than $1,000,000, depending on the assumption of various economic parameters. Compared with the cost of the whole machine (about $100,000), this value is very high. The economic evaluation is based on the development of a fully automated rebar manufacturing machine, employing current technology of computerized numerically controlled machines used for the purpose. This paper also describes an actual field implementation of fully automated rebar productions in a large rebar manufacturing plant. The implementation was based on the integration of a CAD/CAM system with the existing setup of the plant. A communication link was developed to enable the data to be transferred after being extracted and processed with the CAD/CAM system.

Problems in operating construction equipment in Egypt were perceived as resulting in low productivity. Productivity was considered in this study as a measurement dimension that sufficiently describes operator's performance. The objectives of this study are to provide an analytical approach for identifying causes of productivity loss and evaluating their effects, and to evaluate the performance of equipment operators. The performance ability ratio (PAR) compares the actual productivity against the estimated productivity to demonstrate the amount of loss of productivity and, thus, judge the level of operator productivity. The study was conducted at 11 jobs concerning 11 pieces of earthmoving equipment: three bulldozers, three elevating scrapers, three off-highway trucks, and two hydraulic backhoe excavators. The analysis led to basic conclusions concerning the amount of downtime and its variation according to equipment type, and the average PAR values for operators of the four types of equipment.

Chain trenchers were used to cut moderately strong sandstone bedrock, compressive strength 6–9,000 psi (41–62 MN/m ² ), of varying thickness up to 17 ft (5.1 m), beneath desert alluvium in Sedona, Arizona. Data from the case history indicated an inverse relation between trencher performance expressed as a cutting rate or volume excavation rate and the thickness of rock cut. This was compared with curves derived from a simple balance of the cutting energy available from the trencher and the energy required to break a unit volume of rock. The closeness of the fit provides a basis for understanding the mechanics of chain-trencher cutting performance and for the prediction of performance in rocks of different strengths and thicknesses. The main conclusions are that: (1) The design of chain trenchers is such that power available for cutting remains constant and low; and (2) machine productivity in terms of traverse speed or excavation rate is inversely proportional to the strength and thickness of any rock cut.

A utility theory model, which is one of three generic methods for bid markup determination, is developed using 21 criteria in the bidding decision. The majority of the criteria are evaluated subjectively by a decision maker, and numerical quantification and evaluation is typically difficult for such criteria. Previous works of Saaty, Lifson and Shaifer, and Ahmad and Minkarah are used to develop a simplified approach using straight-line utility functions to resolve such difficulty. This bidding model accommodates the variation of different decision makers' attitude in the weighting of criteria, and thus the model can be customized to different preferences and bias of risk. Considering the subjectivity of the process, the writers consider the accuracy of this approach to be acceptable for the use of utility theory as one of the decision making tools that are available to assist the construction contractor in determination of bid(s) markup during bid preparation.

A new approach for resource scheduling using genetic algorithms (GAs) is presented here. The methodology does not depend on any set of heuristic rules. Instead, its strength lies in the selection and recombination tasks of the GA to learn the domain of the specific project network. By this it is able to evolve improved schedules with respect to the objective function. Further, the model is general enough to encompass both resource leveling and limited resource allocation problems unlike existing methods, which are class-dependent. In this paper, the design and mechanisms of the model are described. Case studies with standard test problems are presented to demonstrate the performance of the GA-scheduler when compared against heuristic methods under various resource availability profiles. Results obtained with the proposed model do not indicate an exponential growth in the computational time required for larger problems.

Strategic planning is an essential function of senior management in any business firm. Planning involves the firm's behavior in a competitive market and adaptation of the company's resources towards the selected market strategy. This paper presents a methodological procedure for strategic planning in a construction company. This procedure consists of the following stages. First, examine the company's mission. The mission reflects the owners' views with regard to the company's scope of activities and objectives. Second, survey the company's business environment. The environment includes both general economic factors that affect all types of business activity and additional factors, specific to the construction sector. This survey should reveal the specific “packages” of prospective project opportunities and highlight potential threats to a company's orderly activity. Third, analyze the company's main resources. The main resources in this respect include the construction capacity, the procurement system, the marketing system, the organization, personnel, finances, and knowledge. The relative strengths and weaknesses of each resource, in light of market needs, are identified. Fourth, develop a strategy. The development of a strategy is based on “mapping” of the relative attractiveness of the various possible activity areas. This strategy can follow one of several generic types that must be adapted to particular conditions of the market and company. It affects the subsequent choice of a strategy for development of the company's own resources. The choice of the optimal strategy, from several available alternatives, should follow a careful analysis of the costs and benefits inherent in the implementation of each.

The up/down construction method has great potential to shorten construction time. Until several years ago, this method had rarely been used in the United States. Recently, however, it has emerged, being applied in several projects, and its effectiveness in saving construction time is being proven. While efficient in terms of scheduling, the up/down method poses some disadvantages and risks for the contractor due to its unusual and complicated construction procedures. Various modifications of the up/down technique can be devised to accommodate project conditions and the contractor's experience and familiarity with a given construction methodology. This paper presents a modified up/down method that depends on more conventional construction techniques, but that can still result in significant construction time savings. A real construction project is presented to illustrate the effectiveness of the modified up/down method in terms of construction time saving and practical cost considerations. Applying the method presented in this paper provides an easy and useful way for the contractor to shorten construction duration and, in the long run, reduce costs.

Automation and robotics are often proposed as solutions to problems in productivity, quality, safety, and skilled-labor availability in the United States and in Japan. In recent years, many prototype robots have been developed, but few practical examples can be found on construction sites today. Nevertheless, several large Japanese contractors are aggressively pursuing research and development (R&D) programs to introduce robots on construction sites. United States contractors exhibit little interest. This paper evaluates construction automation and robotics in the context of their ability to satisfy the often conflicting demands of managers and owners, workers, and society in the United States and in Japan. In the United States, there is weak demand for construction automation and robotics. In fact, there may be considerable resistance. In Japan, there is a great deal of demand for automation and robotics, much of it coming from workers and society in general. Differences in cultural, economic, and business practices help explain why construction automation and robotics are generating so much activity and investment in Japan and so little in the United States.

Despite the fact that the majority of construction workers today are hired by merit shop (nonunion) contractors, little prior research is available on the recruitment and selection practices of such employers. This paper examines the recruitment and selection of skilled and common labor based on mail survey responses from 44 Alabama merit shop (nonunion) contractors. Both the frequency of use and perceived effectiveness of different recruitment sources and selection methods were examined. Sixty-five percent of contractors surveyed did not have a formal written policy covering recruitment and selection procedures. Few firms ( <7) included a specific estimate of recruitment and selection costs as part of project bid proposals. Internal sources (e.g., current employee referral or previous hires) were primarily used to recruit both skilled and common labor. Contractors used an average of seven different sources to recruit skilled labor and six different sources to recruit common labor (e.g., referral from a current employee, previous hires, walk-in applicants). On average, contractors used five different methods to select skilled labor and four different methods to select common labor applicants (e.g., job interview, reference check, written application, drug test). None of the recruitment sources or selection methods used were rated by contractors, on average, as either excellent or very good. Contractors frequently encountered problems recruiting common labor including an insufficient labor supply; inadequate math, technical, and oral or written communication skills; and a poor work ethic or motivation level. Fifty percent of contractors also experienced an inadequate supply of skilled labor. General contractors required significantly fewer days than specialty contractors to hire skilled labor (20 versus 52 days, respectively). General and specialty contractors required, on average, six days to fill a common labor position. These results and recommendations for construction human-resource management practice are discussed in this paper.

In 1979, the Business Roundtable (BR) commissioned a study to determine the true costs of accidents and injuries in the construction industry. At that time, the BR concluded that accidents and injuries account for 6.5% of the total cost of industrial, commercial, and utility construction. Since the time of the original study, much has changed in the construction industry. Most importantly, the costs of workers' compensation insurance have skyrocketed and there has been a rash of third-party lawsuits as a result of accidents on construction sites. This paper reexamines the total costs of accidents and injuries to the construction industry, updating the original inputs, and, where necessary, modifying methods. Because the results are very sensitive to several assumptions, the analysis is performed using a range of values for each key assumption, rather than just a single figure. This paper shows that the total costs of accidents have risen to somewhere between 7.9% and 15.0% of the total costs of nonresidential, new constrution.

Researchers and practicing engineers have recently paid considerable attention to alternative approaches to project integration, such as partnering, design-build, constructability, and combinations of these. Each approach may improve a project's integration by increasing the quality and/or quantity of interaction between designers and builders. It is generally accepted that project performance can be enhanced when interaction occurs on a regular basis, beginning early in the project, in an open and trusting environment. This paper presents a method for measuring a project's degree of interaction (DOI), and verifies the relationship between DOI and performance indicators such as cost growth, schedule growth, and number of modifications. The writers apply the analytic hierarchy process technique in weighting criteria for measuring DOI. Data were collected from 25 recently completed public-sector projects using traditional and alternative approaches. The projects with low DOI have a wide range of cost and schedule growth and number of modifications, while projects with high DOI tend to have better and more consistent performance indicators.

Since many construction worker fatalities and injuries are the result of contacts with overhead powerlines, a detailed investigation was conducted on approximately 500 powerline accidents. The objective was to learn more about the conditions and circumstances surrounding these accidents. Because nearly 60% of the accidents involve equipment, these types of accidents were examined in greater depth. Cranes and boom trucks are most frequently involved in equipment powerline contacts. Most equipment contacts are with the boom or the load line. Carrying or handling metallic items, especially aluminum ladders, are the cause of many nonequipment-related fatalities. Human contacts most frequently occur with the hands. The ages of workers killed in powerline contacts are generally in the range of 20–29 years. These contacts when considered by the hour of their occurrence in the day are similar to the pattern observed in other construction accidents. The occurrence of these contacts by the month of the year show an unusual peak in October, a phenomenon that is not explained by the data.

This paper examines the pattern of stochastic dynamics, which includes percentage changes, trends, and volatility for economic and financial variables of failed and nonfailed contractors and uses them to predict contractor failure. Contractor failure is defined as the termination of a contractor's operation. Monthly economic data were collected from publicly available economic reports such as the Federal Reserve Bulletin . Contractor financial data were obtained from five insurance companies. The total sample consisted of 430 financial statements representing 120 contractors (49 failed and 71 nonfailed). Statistic analysis reveals that failed contractors have a negative trend and larger volatility in the percentage changes of net worth, gross profit, and net working capital. A random coefficient method is proposed to describe the stochastic dynamics, i.e., the future position, the trend, and the volatility. A discriminant function for detecting failed contractors has been developed using stepwise regression. The discrimination function includes the following variables: (1) trend–prime interest rate; (2) future position–new construction value in-place; (3) trend–new construction value in place; (4) future position–net worth/total asset; (5) trend–gross profit/total asset; and (6) volatility–net working capital/total asset. An additional 23 contractors (10 failed, 13 nonfailed) were used to validate the developed model. The model misclassified five contractors. Example applications of the model are also provided.

Soundless chemical demolition agents (SCDAs) have been used in a variety of circumstances where other more conventional means of demolition were not feasible. When compared with conventional explosives, SCDAs are not yet economically competitive. Research was conducted on SCDAs to examine the possibility of adding an inert material (sand) to the SCDA in order to extend the material. Results show that although the expansive pressure generated by the SCDA is reduced by adding sand, reduction is not commensurate with the amount of sand added. Research was also conducted in order to determine if the workability of the SCDA slurry could be improved by adding a superplasticizer. These tests were conducted at water contents below levels where conventional mixtures were too stiff to effectively deposit them in a borehole. Results show that a superplasticizer can effectively improve SCDA workability and that the resultant expansive pressure is greater than that which is possible without the superplasticizer.