Seismic Resilience Function Loss Analysis Of Traffic System Considering The Urban Complex Bridge Node

In modern society,the transport system,together with the energy,water and telecommunications networks,is one of the most important links in urban functioning as the main civil infrastructure system that provides the key pillars of contemporary society.The transport system also provides escape routes for the injured and survivors after extreme events such as earthquakes,as well as emergency transport networks for rescue workers,building repairs and disaster relief.The seismic toughness of transportation system refers to its ability to resist and recover quickly after an earthquake.In the transportation network,Bridges are the most vulnerable infrastructure to earthquake,so the seismic response of Bridges is closely related to the seismic toughness of the transportation system.In this paper,the tangshan city traffic network is taken as the research object to study the seismic toughness and functional loss evaluation of the urban traffic system after the destruction of the bridge structures after the earthquake.The main research contents are as follows:(1)The traffic network of Tangshan city is topologized and the data of each network is collected.Since the traffic flow information cannot be obtained directly,a method to calculate the traffic flow based on the running speed is proposed.The specific method is based on the traffic situation information provided by the existing commercial map software open platform,the basic formula of road speed is obtained through nonlinear fitting,and the speed-to-flow model is converted into the required traffic flow for subsequent OD backtracking.The traffic demand acquisition framework can be used to solve the problems of traffic flow analysis in regions without historical OD matrix and lacking traffic information.(2)The paper analyzes the post-earthquake damage status of Bridges in cities and the function loss of traffic network corresponding to different damage degrees.The paper USES the bridge vulnerability analysis to judge the damage state of the ordinary road and bridge and corresponding to the traffic function loss.A simplified calculation method is proposed to judge the seismic damage state of viaduct by bridge piers,and the function loss of viaduct node is analyzed by taking into account the function contribution of ramp after the earthquake and the space coupling relation.(3)Function loss analysis and toughness evaluation of traffic system after earthquake are carried out.Based on the traffic flow data,OD demand matrix of Tangshan traffic network is obtained by using OD inverse method.The local traffic function loss corresponding to the bridge damage state after the earthquake is input into the network to evaluate the whole traffic network function loss.The saturation index based on the service level is proposed as a function function to judge the road service level,so as to ensure the traffic demand remains unchanged and change the change of total travel time and road saturation information of the bridge function loss judgment system.The corresponding function is used to evaluate the toughness of the system,and the importance of the bridge is judged on the basis of the total passage time of the system,which is used for reinforcement and reconstruction before earthquake and emergency rescue after earthquake.