Optimization Of Location-routing Problem On Post-earthquake Emergency Logistics Systems

Among the most destructive natural disasters, the earthquake always results in the disruption of transportation and communication facilities, abundant deaths and economic losses in the affected area. Transportation paths are unlikely to recover in a short time after the disaster. Thus, earthquake relief response requires a scientific and effective emergency response logistics system to eliminate the losses and damage. Two inter-connected key problems in the emergency response logistics system optimization are how to locate the emergency facilities and optimize the routes to affected area.After the earthquake, the authorities immediately activated emergency response plans and resolutely adopted a series of effective measures to carry out emergency relief. But the lack of rational planning of the emergency logistics system program always led to iterative distribution, oversupply, missed deliveries, and inefficient distribution of relief resources. Consequently, the integrated optimization of LRP on emergency logistics system in earthquake disaster was studied with its great theoretical and practical significance as follows:(1) For air transport emergency logistics system optimization in initial phase of post-earthquake response, a single echelon LRP model was formulated to minimize the total time elapse of the entire system in relief response. This model assisted in distribution center location-allocation and route planning at the initial response stage. A two phase decomposed triangle based heuristics was generated and proved its ascendency and computational efficiency compared with improved genetic algorithm.(2) Breakage of road network, a two-echelon LRP model was formulated to determine the locations of distribution centers of relief commodities and relief distribution centers, as well as the relief airplane routes during relief process. According to the characteristics of the model, an improved genetic algorithm (GA) was proposed. And a special real-valued coding scheme, punishment function method and demand split strategy were adopted to deal with restriction in the model. The results of a numerical example show that the proposed model and algorithm can resolve the facility location-allocation and cargo-transport plane, helicopter routing problem in post-earthquake emergency logistics systems in an efficient manner.(3) Considering timeliness, connectivity of road networks, multi-modal transportation and uncertain demand in the system, a fuzzy LRP model multi-objective was developed to determine the locations of distribution centers of relief commodities and relief distribution centers, as well as scheduling the routes of emergency vehicle during relief process. According to the characteristics of the model, an weighted coefficient transformation based GA was proposed. To overcome the premature problems of GA, stochastic selection, regrouped strategy and changing mutation probability are used, and a special real-valued coding scheme, punishment function method and demand split strategy were adopted to deal with restrictions in the model. The validity of the model and algorithm was demonstrated by a numerical example.(4) With the changing need intensity of rescue resources at different stages, a weighted coefficient of the dispatching time and the cost was changing along. A fuzzy dynamic two-echelon optimization model with multi-objective was developed to determine the locations of distributing centers of relief commodities around the disaster area and relief distribution centers in the disaster area, as well as the relief vehicle routes in each period during relief process. The last rescue point of every route was likely to not satisfy needs in fuzzy optimization. Therefore, an emergent distribution strategy needs to be adopted. A weighted coefficient transformation and multi-period parallel computation based improved GA was proposed, and a special real-valued coding scheme, punishment function method and demand split strategy were adopted to deal with restrictions in the model. The results of a numerical example show that the proposed model and algorithm are effective for resolving the joint decision-making of LRP in post-earthquake emergency logistics systems.(5) Considering the priorities of relief items, multi-commodities and multi-modal transportation, a stochastic demand LRP model with multi-objective was formulated to determine the locations of relief distribution centers in the disaster area, as well as the relief vehicle routes in each period during relief process. According to the characteristics of the model, a multi-period parallel computation and weighted coefficient transformation based GA was proposed, and a punished function method was adopted to deal with restriction in model. The results of a numerical example indicated the effectiveness of the proposed model and algorithm.