FRAGILITY ANALYSIS OF BRIDGES OF A RAIL NETWORK

Abstract

Critical infrastructure networks, such as power networks, transport networks are critical to a society's and economy's operation. Since in India, the major mode of transportation is railway transportation, the railway networks become more important as compared to other modes of transport. Railway network is difficult to operate as there are an ever-increasing number of disruptions because of climate change, natural calamities (Earthquake and Tsunami etc.), as well as system failures. As a result, many trains are cancelled or severely delayed, and many passengers are unable to reach their destinations, putting customers' mobility at risk. The requirement to quantify the effects of disruptions and the evolution of system performance is becoming increasingly important. This report contains study of fragility analysis of bridges of a railway network. In the present study, bridges (Bridge No. 3,4,5) present on upcoming railway network in the Indian Himalayas is considered for fragility analysis. For carrying out the fragility analysis, firstly non-linear dynamic analysis (Incremental Dynamic Analysis) is performed on the considered bridges. Methodology considered in this report for Bridge No. 5 is performing IDA on all piers separately and then performing IDA on the complete bridge. All piers are modelled using a fibre lumped plasticity hinge. The remaining portion of the piers is modelled as elastic frame element. The mass of superstructure is lumped at the top of the pier. All models are subjected to 22 ground motions obtained from FEMA P695 for IDA. For every single ground motion, both horizontal components are applied simultaneously on models. Results of the incremental dynamic analysis of all separate piers, and bridges are compared to find the most critical pier of bridge and then fragility analysis is done considering record to record variability, capacity uncertainty, and modeling uncertainty. For Bridge No. 3 and 4, IDA is performed on complete bridges directly and their results are used to find fragility of these bridges. Finally, fragility of all bridges is compared in this report.