eva‎luation of fragility curve in arched ballast railway lines

1/20/2023 12:00:00 AM

Rail transport network of each country is one of the safest, cheapest and most cost-effective public transport systems that are environmentally friendly, so in recent years, attention to intercity and suburban rail systems in Iran has increased. Also, considering the role of this system as a vital artery system and the need for its usability after a natural disaster such as an earthquake, it is necessary to study its behavior in earthquakes. The purpose of this study is to develop a three-dimensional numerical model of straight and curved boundary line components by SAP 2000 software that can be used for seismic analysis of railway lines. The statistical concepts of fragility curve are used to investigate vulnerability. Determining the critical length and developing the fragility curve in the arched railway line are some of the innovations of this study. First, the three-dimensional finite element model is validated for the straight line by the laboratory work of Nakamura et al. Then the railway system was modeled nonlinearly at different lengths for straight rail lines with horizontal arcs with different radii. In the three-dimensional model, beam elements are used for rails and sleepers, and mass, spring and damping systems are used for ballast and undercarriage. After applying Kobe earthquake to the models, the length of the line in which the maximum amount of lateral displacement of the line was created is considered as the critical length. This length was estimated at 20 meters for all lines. After examining the critical length, the statistical meanings of the fragility curve were investigated and the line vulnerability was presented using fragility curves based on the index of maximum displacement damage and ground acceleration. In this study, using the chronological history analysis of 35 earthquakes as input to the structure and using the results of the analysis and the relationships related to fragility, the fragility curve was drawn. The results of this study show that by decreasing the line radius, the failure index increases and also for a constant transmittance probability, the arc with a smaller radius will demand less spectral acceleration to achieve a functional level. The probability of minor failure at 0.4 g acceleration is 90% for an arc line with a radius of 500 m and 68% for a straight line. However, a straight line at 0.7 g acceleration has a 90% chance of failure, so arched lines are more vulnerable than a straight rail line.

مدل عددي سه بعدي اجزامحدود , قوس , طول بحراني , تحليل تاريخچه زماني , آسيب پذيري لرزه اي , منحني شكنندگي

Three-dimensional numerical model of finite elements , arc , critical length , time history analysis , seismic vulnerability , fragility curve

Fatemeh Hedayati Goudarzi

Morteza Esmaeili