Editor’s Note

“Developing a Complexity Measure for Project Schedules”: Nassar and Hegab present a measure that assesses the complexity of project schedules in terms of the connectivity of activities. Unlike similar measures, the authors’ proposed measure does not consider redundant relationships in the project schedule. The measure considers the degree of interrelationships between the activities in the project’s schedule and has been implemented in a computerized tool developed as an add-on to popular commercial scheduling programs.

“Minimizing Construction-Related Hazards in Airport Expansion Projects”: The close proximity between construction activities and airport operations during airport expansion projects needs to be carefully considered during the planning of the project to minimize potential construction-related hazards. Khalafallah and El-Rayes present the development of a multiobjective optimization model for planning airport construction site layouts that is capable of simultaneously minimizing construction-related hazards and site layout costs. The model is implemented using a multiobjective genetic algorithm, and an application example is analyzed to demonstrate its use.

“Safety Climate in Construction Industry: A Case Study in Hong Kong”: Authors Fang, Chen, and Wong extract a fifteen-factor structure that defines the dimensions of safety climate from results of a safety climate survey performed in Hong Kong, of which a total of 4,719 records from 54 sites was returned. Compared with previous research studies, the roles and influences of fellow workers and safety resources on safety climate are emphasized. Through further analysis, logistic regression is used to explore the relationship between safety climate and personal characteristics, including gender, marital status, education level, and other key qualities.

“Non-Unit-Based Planning and Scheduling of Repetitive Construction Projects”: Because almost all repetitive scheduling methods developed to date have been based on the premise that a repetitive project is comprised of many identical production units, Huang and Sun develop a non-unit-based algorithm for planning and scheduling repetitive projects. Instead of repetitive production units, repetitive or similar activity groups are identified and employed for scheduling. A case study of a sewer system project is conducted to validate the algorithm, as well as to demonstrate its application.

“Soil Penetration Modeling in Microtunneling Projects”: As the need for utility service line replacement or repairs with minimum disruption to the surface has increased, so has the demand for trenchless excavation methods, in particular, microtunneling. When bidding a microtunneling project, the main concern of microtunneling contractors is predicting the underground behavior of the machine. As part of a series of papers covering the productivity of microtunneling projects, Hegab, Smith, and Salem focus on predicting the penetration time of the microtunneling machine to aid contractors who lack a productivity model to help predict driving time.

“Identifying a Design Management Package to Support Concurrent Design in Building Wafer Fabrication Facilities”: Current practice in managing a design schedule involves preset milestones that represent percentages of completion, which do not provide sufficient information to support concurrent design. Dzeng 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. Because tasks of different packages have weak dependency relationships on each other, they are suited for concurrent design.

“Management and Construction of the Three Gorges Project”: Dai, Cao, and Su cover the construction of the Three Gorges Project, the key project in harnessing and developing the Yangtze River. The project employed the use of the owner-responsibility system. The authors explain the roles of project managers and contractors and the processes each used to successfully execute the construction of the project.

“Infrastructure Development and Expansion under Uncertainty: A Risk-Preference-Based Lattice Approach”: Optimal infrastructure development and expansion decision making requires taking into account contingent expansion decision and underlying uncertainty, such as demand during the planning period. Zhao and Fu present a risk-preference-based lattice model to evaluate infrastructure development and management policies which provide the optimal contingent decisions in terms of a risk preference. The proposed methodology is demonstrated in an example involving constructing and expanding a parking garage.

“Scheduling-Based Risk Estimation and Safety Planning for Construction Projects”: One of the measures for evading high-accident-risk situations so that risks are not concentrated during certain periods is to predict such situations and to reschedule their start times. Yi and Langford analyze results of historical accidents and provide information about vulnerable situations. In addition, the authors present a theory of safety planning that estimates the risk distribution of a project and helps the safety manager to estimate situations of concentrated risk and to reschedule the activities when necessary.

“Construction Delays in Hong Kong Civil Engineering Projects”: Construction delays are common in civil engineering projects in Hong Kong, inevitably resulting in contractual claims and increased project cost. Lo, Fung, and Tung present a study aimed at gathering the perceptions of civil construction practitioners on how significant are the causes of delay. In addition, the authors investigate whether the suggestions proposed by the Construction Industry Review Committee are applicable to and effective at mitigating the corresponding delays with reference to a ranking order established using the mean score method.

“Neural Networks for Estimating the Productivity of Concreting Activities”: This technical note on neural networks can offer a guiding tool for overcoming the variability and the impact of subjective factors on the cost of concrete-related activities in developing countries. Ezeldin and Sharara have developed three neural networks to estimate productivity for formwork assembly, rebar installation, and concrete pouring activities that are based on 18 experts and 92 surveys. Results indicate adequate convergence and relatively strong generalization capabilities.