Research On The Dynamic Reliability Of Electrified Railway Catenary System Subjected To Environmental Loads

Catenary system takes the responsibility of transmitting the electricity energy from transaction power supply system to electric locomotives, and its quality and working condition will directly affect the electric railway transport capacity. Therefore, catenary is request in good working condition under any weather condition, satisfing the safety and high-speed move requirement when the electric locomotives are on the line. Catenary is a special form of space overhead line structure, and has a tall and large span feature-its suspension and support structure has the coupling effect under the dynamic characteristic of different orders of magnitude. Catenary has complex dynamic responses, strong sensitive and high degree of uncertain feature under random load of sand and ice, which is the main reason of catenary failure in recent years. Also, catenary has long line, many points and no reserve, which may cause the train to stop and make serious impact on safety and reliability of the catenary. The safety problem is the main consideration of electric upgrading of Lanzhou to Xinjiang railway.Under the electric upgrading needs of Nanjiang and Lanxing railway, it's emergent to conduct research of wind protection and the influence of wind on catenary structure's stability and reliability, which serves the very magnificent theoritical meaning and engeering practical value.The research object of this paper is based on catenary of certain strong wind area of Lanxin line. The environment loads of wind and sand are in random uncertainty that the catenary has the characteristics of high, big, thin, long flexible structures. Owing to this, from the perspective of probability and time-domain, this paper is based on a wide range of home and abroad counterparts research results, focusing on catenary vibration which induced by catenary structure environment, and also studied wind-resistant stabilization and wind-resistant reliability issues. The thesis includes the following aspect:1. It was analyzed on the causes of strong winds in Xinjiang area and the statistical law of the winds, according to the documentation and data in hand, based on minimum error approximation and matrix method, resulting in the probability distribution of average wind speed and annual maximum average wind speed in Lanxin line's strong wind area.According to the Environmental and catenary structure characteristics, it was considered about the profile about the distribution of gradient wind load, turbulence pulsation correlation, turbulence intensity and power spectral density by adopting harmonic superposition method, establishing numerical simulation of fluctuation wind field by davenport wind speed spectrum and the simplified wind field simulation method suit for catenary structure. By calculating the wind speed of different catenary structure with the simplified wind field simulation method, the results shows that the simulated wind speed power spectrum is consistent with the target spectrum, and the simulation-generated wind fields can be characterized by random wind field in random nature of time domain.In order to describe the basic characteristics of sand and its influence on catenary structure, it is combined with the natural properties of sand, the load formation patterns and the structural characteristics of catenary system and analyzes the influence on wind loads to catenary structure by using sand-wind two-phase flow's mathematical model.2. By regarding the coupling effect between catenary support structures and its suspended structure; the sag effect of contact line and carrier cable and the geometric nonlinearity and the material nonlinearity of support structure through finite element software ansys, it is established three-dimensional finite element model of the catenary system based on its two-dimensional model. By verifing the validity of the model in experiment and determining the parameter and process methods of wind induced vibration response time domain analysis of catenary structure system, it is analyzed on dynamic response of catenary structural system from wind load and wind-sand load, etc.The result shows that when compared with the nature frequency of catenary with the nature frequency of independent support structure and suspension structure, the natural frequency of independent support structure and suspension structure are slightly decreased and the coupling effect between independent support structure and suspension structure are very significant. The design of catenary structure is unreasonable when it is only equivalent to the load of carrier cable and contact line to static load. With the increase volume ratio of sand, the influence on wind-sand load to catenary structure's feature point response comes to increase. This shows that, the sand load has obvious incentive contribution to the feature point response.3. On account of the characteristic of catenary structure, based on the process of wind-induced vibration response of feature response point, the dynamic incremental method is introduced to the Budiansky-Roth stability criteria, proposing dynamic stability criteria of wind-resistance by its compared with the influence on different structural characteristic of the dynamic stability of centenary. The result reflects that by increasing the tension, reducing the span, reducing the contact line height and appropriately increase the number of suspension lines, the wind-resistance stability of catenary structure can be effectively improved.4.In the premise of systematically analyzing the reason and failure mechanism of catenary structure fatigue damage which occurred and developed, based on the finite element stress response time-history,the probability distribution characteristic of catenary structure's environmental load effect and the fatigue damage theory's fatigue reliability analysis method are estabilished by taking the contact line as an example, analyzing the impact degree of the contact line fatigue reliability by structural factors and environmental factors. The case suggests that the weight of contact line, the load of ice and sand make large impact on the fatigue reliability of contact line, which can't be ignored.5. By considering the probability distribution of wind speed and the sand environmental characteristics, it is proposed time-domain dynamic reliability calculation method of catenary structure from applicability and strength failure aspect by using first time beyond theory. The calculation method is combined with the finite element method, RBF neural network and Monte Carlo simulation, unrestrained from the form of random variable distribution, and also isolated from the non-linear restrict of limit state equation, resulting in more satisfied calculation accuracy.