چكيده به لاتين
Today, between 20% and 40% of the railway costs are spent on repairs and maintenance. The existence of this huge expense reveals the necessity of using accurate and optimal planning for this operation. Each year, a number of rail maintenance projects are set up across the network and allocated to existing work teams. On the other hand, the implementation of these projects leads to the blocking of railroads, which is the lack of trains that cause to lose railroad revenue and customer satisfaction.
The Curfew planning problem (CPP) is the creation of a long-term planning in the rail network, which simultaneously addresses the optimal allocation of team works to rail maintenance projects and determines the optimal timing of clustering in subdivisions and service corridors. Since today because of speed, precision and efficiency of mechanized machinery using them instead of manpower is expanding, in this research we design a mathematical model of CPP for assigning projects to mechanized rail machinery and determining the optimal curfew time regarding to some side constraints such as precedence restriction, mutual exclusivity for projects and subdivisions, machine travel between consecutive activities and simultaneity of a project activities with the aim of minimizing disruptions in train routes. The objective function in this model is minimizing various costs, such as the cost of allocating machines to each activity, car journeys between successive activities, the cost of blocking in each subdivision and penalties of side constraints violation. In this research, projects that themselves have different types, are divided into a set of activities and each machine can perform a certain type of activity. At the end, the designed model was implemented for the Islamic republic of Iran railway. In this case study the proposed railway program for conducting projects and curfew planning of entire network in the two six-month periods of year 97 was examined and then it solved by mathematical model to compare the current and disirable situation of curfew scheduling. In the model designed table, there were noticeable improvements in network status, so that all projects are completed by limited resources and costs are clearly reduced. Finally, after sensivity analyze on important parameters of the problem, such as the number of available machinery and the number of projects in each period, suggestions for improving rail productivity in the future studies were presented.
