Journal of Construction Engineering and Management

Several factors contribute to the complexity of project schedules, including the number of activities, the level of detail, and the shape of the project network. This paper presents a measure that assesses the complexity of project schedules in terms of the connectivity of the activities. Unlike similar complexity measures, the proposed complexity measure does not consider redundant relationships in the project’s schedule. In addition, the measure is expressed as a percentage and therefore has the advantage of being intuitively understand by project managers. The measure considers the degree of interrelationships between the activities in the project’s schedule. The measure has been implemented in a computerized tool to help managers assess the complexity of their projects. The tool is developed as an add-in to popular commercial scheduling software like MS Project.

Airport expansion projects often require the presence and movement of construction labor and equipment near critical airport traffic areas. This close proximity between construction activities and airport operations needs to be carefully considered during the planning of construction site layouts in order to minimize and eliminate all potential construction-related hazards to aviation safety. This paper presents the development of a multiobjective optimization model for planning airport construction site layouts that is capable of minimizing construction-related hazards and minimizing site layout costs, simultaneously. The model incorporates newly developed optimization functions and metrics that enable: (1) maximizing the control of hazardous construction debris near airport traffic areas; (2) minimizing site layout costs including the travel cost of construction resources and the cost of debris control measures on airport sites; and (3) satisfying all operational safety constraints required by the federal aviation administration as well as other practical site layout constraints. The model is implemented using a multiobjective genetic algorithm and an application example is analyzed to demonstrate the use of the model and its capabilities in optimizing construction site layouts in airport expansion projects.

Because of the characteristics of decentralization and mobility in the construction industry, safety culture is crucially important. A comprehensive safety climate questionnaire survey was conducted with all sites and employees of a leading construction company and its subcontractors in Hong Kong. In total, 4,719 records were returned from 54 sites. By means of factor analysis, a 15-factor structure that defines the dimensions of the safety climate has been extracted. Compared with previous research studies, the roles and influences of fellow workers, and safety resources on the safety climate are emphasized. The results also confirm the feasibility of exploring common factors of the safety climate in the construction industry. Through further analysis, logistic regression was used to explore the relationship between the safety climate and personal characteristics. Statistically significant relationships were found between safety climate and personal characteristics, including gender, marital status, education level, number of family members to support, safety knowledge, drinking habits, direct employer, and individual safety behavior. This research is a case study and the results are derived from the data of one company, but the methodology of this research may be useful as a model for further research, and the findings may provide useful information for construction managers and safety practitioners in the construction industry to improve their safety culture.

Repetitive scheduling methods are more effective than traditional critical path methods in the planning and scheduling of repetitive construction projects. Nevertheless, almost all the repetitive scheduling methods developed so far have been based on the premise that a repetitive project is comprised of many identical production units. In this research a non-unit-based algorithm for the planning and scheduling of repetitive projects is developed. Instead of repetitive production units, repetitive or similar activity groups are identified and employed for scheduling. The algorithm takes into consideration: (1) the logical relationship of activity groups in a repetitive project; (2) the usage of various resource crews in an activity group; (3) the maintaining of resource continuity; and (4) the time and cost for the routing of resource crews. A sample case study and a case study of a sewer system project are conducted to validate the algorithm, as well as to demonstrate its application. Results and findings are reported.

As the need for utility service line replacement or repairs with minimum disruption to the surface have increased, so has the demand for trenchless excavation methods, in particular, microtunneling. Microtunneling is a trenchless technique that is used to install new pipelines. Microtunneling can be applied in gravity and pressure lines, permanent ducts for cables, and crossings under rails or roads. When bidding a microtunneling project, the main concern of microtunneling contractors is predicting the underground behavior of the machine. In other words, the productivity of microtunneling is the key to profit in microtunneling projects. Contractors generally predict approximate productivity based on experience, which risks cost estimation accuracy for microtunneling projects. Contractors lack a productivity model that helps them to predict driving time. This paper is a part of a series of papers covering the productivity of microtunneling projects. This paper focuses on predicting the penetration time of the microtunneling machine.

Concurrent design is commonly used in building a semiconductor wafer fabrication facilities to shorten projects. Current practice in managing a design schedule involves preset milestones that represent percentages of completion. Such a simple control scheme does not provide sufficient information to support concurrent design. This study presents an analytical model that applies a cluster identification algorithm to separate the work of designing a multisystem project into management packages that support concurrent design. Tasks within a package have strong informational dependency relationships on each other, and are not suited for concurrent design. Tasks of different packages have weak dependency relationships on each other, and are suited for concurrent design. Tendering design work based on these packages may reduce the number of design interfaces between participating design firms. Possible application of the model includes the management of design schedule, design contract tendering, and design information flow.

The owner-responsibility system is conducted for implementation of the Three Gorges Project (TGP). For the construction management of the project, the contracting system, the contract administration system, and the construction supervision system are executed for the project management. Contractors for civil projects are determined through bidding and contracting. The permanent equipment and construction materials are purchased through bidding. Some of large-sized construction machines and mechanical and electrical equipment are procured by the international competitive bids. Qualified engineers from qualified engineering bodies, scientific research organizations, and construction companies are selected for the construction supervision. This paper covers the construction of the TGP in some detail, particularly the main dam structure, diversion work, the construction program, and management, project cost, and financing.

Optimal infrastructure development and expansion decision making requires taking into account contingent expansion decisions and underlying uncertainty, such as demand, during the planning period. Recent publications on life cycle management have used lattice models and Markov decision models to evaluate infrastructure development and management policies. In this paper, a risk-preference based lattice model is presented, and it provides the optimal contingent decisions in terms of a risk preference that can be other than risk neutrality. The proposed methodology is demonstrated in an example involving constructing and expanding a parking garage.

This paper considers the issue of safety risks on construction sites. It introduces the concept of combined effect of different risk factors to the accident. For proper safety planning, safety managers need to be well aware of the direct causes of the accident as well as indirect factors that adversely effect on site safety. If it is observed that if a hazardous environment exists at the site, then either that hazardous environment must be eliminated or occupations and processes related to that hazard must be properly protected. One of the measures for evading such hazardous situations is to predict such situations and to reschedule the start time of high-risk situation so that risks are not concentrated during certain periods and at certain locations. In order to predict when and where the risk will reach its highest level, analysis should be performed based upon various information including statistical sources such as accident histories and this should be done in coordination with the activity scheduling. This paper analyzes the result of accident history and provides information about vulnerable situations. In addition, it presents a theory of safety planning method which estimates the risk distribution of a project and helps the safety manager to both estimate situations of concentrated risk and then to reschedule it when it is necessary.

Construction delays are common in civil engineering projects in Hong Kong, inevitably resulting in contractual claims and increased project cost. This study was aimed, first, at gathering the perceptions of civil construction practitioners on how significant are the causes of delay; and, second, investigating whether the suggestions as stated in the report of the Construction Industry Review Committee (the Committee comprises members with good standing and knowledge in the construction and related fields as well as those from other professions who are responsible for examining the current state of the construction industry in terms of its output quantity, the quality of work, its environmental friendliness, site safety, its workforce and the system of supervision) are applicable to and effective at mitigating the corresponding delays with reference to a ranking order established using the mean score method. The extent of the differences in perception among the different respondent groups on these two issues was also examined using the rank agreement factor (RAF), percentage agreement (PA), and percentage disagreement (PD). The differences in the perceptions of the respondents on the significance of delays and the actual causes of delays for the six projects studied were also examined. The results of the study showed that the respondents tended to admit their own faults as shown in the top ten significant causes of delay. A strong consensus was found between the client and consultant groups on the significance of the various causes of delay $(\mathrm{PA}=74\%)$ and the effectiveness of mitigation measures $(\mathrm{PA}=67\%)$ compared with the other pairs of groups. The consultant and contractor groups held extremely different perceptions regarding the significance of various delay causes ( $\mathrm{RAF}=4.9$ and $\mathrm{PD}=32\%$ ) and the effectiveness of corresponding mitigation measures ( $\mathrm{RAF}=6.2$ and $\mathrm{PD}=47\%$ ). It is believed that the findings can provide much more insight for the construction practitioners as well as the researchers and thus help to improve the productivity and overall performance of civil construction projects in Hong Kong.

To overcome the variability and the impact of subjective factors on the cost of concrete-related activities in developing countries, neural networks can offer a guiding tool. In this study, three neural networks were developed to estimate the productivity, within a developing market, for formwork assembly, steel fixing, and concrete pouring activities. Eighteen experts working in six projects were carefully selected to gather the data for the neural networks. Ninety-two data surveys were obtained and processed for use by the neural networks. Commercial software was used to perform the neural network calculations. The processed data were used to develop, train, and test the neural networks. The results of the developed framework of neural networks indicate adequate convergence and relatively strong generalization capabilities. When used to perform a sensitivity analysis on the input factors influencing the productivity of concreting activities, the framework has demonstrated a good potential in identifying trends of such factors.