| Typical urban bridges are usually located in densely populated and well-developed core areas.They usually cross trunk lines,rivers and canyons.Influenced by the rapid growth of vehicles,pedestrian and driver violations,and poor traffic management,large and medium-sized vehicles are often overloaded,congested,left and right vehicles are parallel in the operation process,resulting in larger traffic congestion and even safety accidents.As a result,the service level of serving bridges has been seriously reduced,which has seriously affected the service life of bridge structures.This paper was supported by monitoring-early warning and safety risk control technology for over-limit load of urban expressway bridges(No.2017YFC0806000).In consideration of the traffic characteristics of urban roads with high saturated flow and heavy load,as well as the lack of two-dimensional load spectrum of urban expressways and the research on the identification methods of bridge structure load and response,the identification methods of urban bridge load,the simulation and compilation of two-dimensional load spectrum,and the identification methods of bridge structure response was studied in this paper studies.The following work had been carried out:Firstly,drawing on the experience of domestic and foreign research on vehicle load identification methods and vehicle load spectrum compilation,four theoretical methods of moving load identification of existing bridges were put forward based on the traffic conditions of large traffic flow,congestion and significant multi-lane effect of wide urban bridges.And the commonly used dynamic weighing systems(WIM,BWIM)in practical engineering bridges were introduced to identify the load of bridges.Secondly,the load spectrum of vehicle loads on urban bridges was compiled,and the influence of multi-lane lateral loads on bridge structure response was discussed.By counting the vehicle flow on different lanes,the response of external loads was regarded as a two-dimensional study(namely,considering the randomness of time and space,vehicle travel time and location(lane)of wide urban bridges).Vehicle flow data of three lanes of a bridge in Yuzhong District in Chonqqing were counted separately,and then the vehicle flow data of four types of vehicles were converted into bus flow.And then the autocorrelation function,power spectral density function and two-parameter Weibull distribution of this section were simulated under congestion and multi-vehicle effect.Furthermore the two-dimensional random load spectrum were obtained,which reflected load characteristics of three lanes.Then the identification of bridge structure response was studied,and the identification to stress and strain through static test data was proposed.Dynamic response identification method based on vibration displacement,acceleration,frequency and damping of bridges was also proposed.At the same time,a health monitoring system was established to identify stress and strain in structure.Based on the monitoring data,the static and dynamic load test data were combined with the finite element model to identify structural response.Finally,taking a dual-purpose bridge for highway and light rail as the engineering background,the two-dimensional load spectrum was applied to the real bridge.And the structural response was identified by finite element method.In order to make the finite element model effectively simulate the actual stress and deformation of the structure,it was proposed that the structural response data based on static and dynamic tests modified the finite element model.It hoped that axle load,speed of vehicles and spatial structure response can be identified through the comparision between the later period health monitoring data and the results of the finite element model,which laid the foundation for the next research. |
PDF Full Text Request