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Most construction projects involve earthmoving operations. Careful management of trucks to perform these operations is considered crucial by earthwork contractors in Taiwan. A mechanism is described that optimizes the management of the truck fleets of earthwork contractors. The proposed model integrates a discrete event simulation technique and genetic algorithms (GAs) to minimize the duration of earthmoving operations. The discrete simulation model is applied to simulate earthmoving operations and generate schedules for dispatching various trucks, and the GAs are used as a filter to screen out schedules that require long trips. Examples prove that the proposed model can determine near-optimal solutions efficiently. In addition, a user-friendly computer program is developed so that earthwork contractors can plan the dispatch schedule of earthmoving trucks easily and effectively. DOI: 10.1061/(ASCE)CF.1943-5509.0000219. (C) 2012 American Society of Civil Engineers

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Construction processes are complex operations that include the uses of equipment, materials, crews and geological conditions. Simulation can be used to study these processes in order to make competent decisions that will lower costs and shorten the duration of the project before it has started. Tunneling is a highly repetitive construction operation and simulation can be used to analyze the process. A model used to simulate the NATM tunneling construction operations for Pakuashan highway tunnel project is developed in this paper. This project is unique because of the soil conditions. A discrete event simulation methodology, CYCLONE, is used to build the operation model and simulate the tunheling processes. Statistical analysis indicates that duration of most tunneling operations can be modeled by Beta probability distribution. Results also show the model predicting the advancement rate of such tunneling proj ect in accurate.

A new approach for improving the performance of freight train timetabling for singletrack railways is proposed. Using the idea of a fixed-block signaling system, we develop a matrix representation to express the occupation of inter-and intra-station tracks by trains illustrating the train blocking time diagram in its entirety. Train departure times, dwell times, and unnecessary stopping are adjusted to reduce average train travel time and single train travel time. Conflicts between successive stations and within stations are identified and solved. A fuzzy logic system is further used to adjust the range of train departure times and checks are made to determine whether dwell times and time intervals can be adjusted for passenger and freight trains at congested stations to minimize train waiting times. By combining manual scheduling expertise with the fuzzy inference method, timetable efficiency is significantly improved and becomes more flexible.