Khalied Hyari

Automated trade‐off between time and cost in planning repetitive construction projects

An automated model is developed to support the optimization of the planning and scheduling of repetitive construction projects. The model provides the capability of optimizing two important objectives commonly sought in scheduling repetitive construction projects: minimizing project duration; and minimizing project cost. The model performs this multi‐objective optimization using a genetic algorithm approach. The output of the model is a set of optimal solutions that represent the trade‐off between time and cost in planning repetitive construction projects. Furthermore, the model can be utilized to find a single scheduling solution that provides the minimum overall project cost by simply adding project indirect cost to the obtained project direct cost for each of the obtained scheduling solutions on the Pareto optimal curve. Other important time‐related costs are also considered in the model including: early completion incentives, late completion penalties and lane rental costs. Providing the planners of repetitive construction projects with an automated set of optimal time–cost trade‐off solutions should contribute to cost‐effective and speedy delivery of this type of construction project. An application example is analysed to illustrate the use of the model and demonstrate its capabilities in generating optimal trade‐off solutions between minimizing the project time and cost for repetitive construction projects.

Automated DSS for Lighting Design of Nighttime Operations in Highway Construction Projects

Nighttime construction lighting is reported to be a crucial factor affecting quality, safety, cost and productivity of nighttime construction projects. This paper presents an automated decision support system (DSS) for lighting design in highway nighttime construction projects. The DSS is designed to optimize four major objectives: (1) maximizing average illuminance; (2) maximizing lighting uniformity in the work zone; (3) minimizing glare produced by the lighting system; and (4) minimizing cost of the lighting system. Seven decision variables are optimized in this lighting design problem namely: (1) lighting equipment selection; (2) type of lamps; (3) lamp lumen output; (4) mounting height; (5) lighting towers positioning; (6) luminaires aiming angle; and (7) lighting towers rotation. A multi objective evolutionary algorithm (NSGA-II) is used to optimize this lighting design problem. The proposed DSS provides a practical tool for the design and optimization of lighting arrangements in nighttime construction operations.

Lighting Design Requirements for Highway Nighttime Construction

The utilization of nighttime construction in highway projects has been increasing in recent years in order to alleviate construction-related traffic congestions and delays. In order to ensure quality and safety in these nighttime construction projects, proper and adequate lighting conditions need to be provided on site. This paper presents the findings of a recent study that focused on (1) identifying lighting requirements for nighttime construction operations in highway projects; and (2) developing a practical design tool to address these requirements. Survey and site visits were conducted to identify the current practices and requirements of highway nighttime construction operations. The analysis of the survey results have led to a number of important findings, including: (1) participant Departments of Transportation (DOTs) reported that an average of 17% of their construction projects involved nighttime work in fiscal year 2001; (2) standards to regulate work zone lighting were found to be lacking in many states as 60% of responses received from state DOTs indicated that they do not have lighting standards or guidelines for nighttime construction operations; and (3) the main challenges in nighttime construction lighting were identified to be insufficient lighting, non-uniformity of provided lighting, and glare to road users. This paper also presents a design and optimization tool to address the needs of highway nighttime construction operations that were identified in the above survey. This tool can be utilized by contractors in design and implementation of lighting arrangements, and by resident engineers in the inspection of lighting conditions on site.

Field experiments to evaluate lighting performance in nighttime highway construction

The utilisation of nighttime highway construction has increased in recent years in order to minimise daytime construction‐related service disruptions and traffic congestion. In this type of nighttime construction, lighting arrangements need to be properly designed and implemented in order to enhance safety and productivity on site, and ensure full compliance with the required lighting specifications. A number of field experiments were conducted to evaluate the performance of various lighting arrangements in three typical highway construction zones, namely: activity area, transition and termination areas and flagger stations. In each of these zones, a number of practical lighting arrangements were found to be capable of satisfying all the lighting design criteria required by various Departments of Transportation. The experimental results also confirm that the set‐up of lighting equipment on site has a significant impact on lighting performance, and therefore lighting arrangements should be carefully designed and executed on nighttime highway construction projects.