Investigation And Analysis Of Seismic Vulnerability Of Urban Concrete Continuous Box Girder Viaducts

In recent years, with our country’s social and economic development and urbanization process’ accelerating, a variety of elevated rapid transit system constructions are also increased. As the city’s lifelines, if the bridges are severely damaged during the earthquake, they will cause enormous difficulties in post earthquake relief work and cause enormous economic losses.Due to the passage of time, the seismic performances of the existing urban viaducts are reduced, and with the new urban bridge rules promulgated, it puts forward new requirements on the seismic performance of city viaducts. It is necessary to evaluate the seismic performance of these bridges, and take appropriate measures of reinforcement.In this paper, through the investigations of the urban concrete viaducts in Fuzhou, predict the earthquake damage of the bridges by using the empirical statistical method. Then based on the investigations, we make theory vulnerability analysis for the vulnerable components and the whole bridge under transverse and longitudinal seismic excitation of the bridges. The main contents include:(1) Summarize the characteristics of the bridge earthquake damage and the development and research status of the bridge structure’s seismic vulnerability, discuss the issues of seismic waves input and the determination of damage index, to provide theoretical basis for the identification of damage index and the establishion of fragility curves.(2) Through the investigations of the urban concrete viaducts on the main roads and the expressways in Fuzhou, collect relevant information, and predict the earthquake damage by using the empirical statistical method.(3) The establishment of the concrete bridge’s dynamic model and the seis mic vulnerability curve of the benchmark bridge along the bridge is introduced in detail.Then we’ll compare "Code for seismic design of urban bridges (CJJ166-20 11)" with " Guidelines for Seismic Design of Highway Bridges (JTG/T B02-01- 2008)" and make a comparison of the bridge vulnerability under different specific ations.(4) The fragility analysis of the city concrete continuous box girder viaducts in the longitudinal earthquake excitation is systematically studied. Through a series of parameter analysis, such as height of pier, span and slope, study the influences to the fragility curves of the bridge most unfavorable components, the supports to the whole bridge and the whole bridge. The bridge most unfavorable components contain the bridge’ sliding laminated rubber bearing, sliding pot bearing, fixed pot bearing and fixed pier.(5) Make a comparison of the vulnerability curves of the benchmark bridge components along the bridge and the transverse direction. The fragility analysis of the urban concrete continuous box girder viaducts in the transverse earthquake excitation is systematically studied. Through a series of parameter analysis, such as height of pier, span and slope, study the influences to the fragility curves of the bridge most unfavorable components and the whole bridge. The bridge most unfavorable components contain the bridge’s sliding laminated rubber bearing, sliding pot bearing, fixed pot bearing and fixed pier.Through the comparison and analysis above, we can get the corresponding rules and conclusions. They can provide a certain basis for seismic retrofitting of Bridges.