Modal Analysis And Monitoring Of Space Truss Structure Considering Snow Load Effects

As a natural environmental factor,the snow load will affect the static and dynamic response of the structure.Therefore,it is of great importance for the condition assessment and damage identification of structures to analyze the static and dynamic response under snow load effects.In this paper,the steel tubular truss structure of the elevated station building in Harbin Railway Station is taken as the research object and the corresponding structural health monitoring system is designed.The variation mechanism of the static and dynamic responses of the steel tubular truss structure under snow load effects are obtained through theoretical analysis,numerical simulation and monitoring data analysis.The change regulations of structures' modal parameters under snow load effects are derived.The main contents are as follows:(1)The finite element model is established based on the design data of the steel tubular truss structure.In the process of gradual application of uniform and non-uniform distributed snow load,the overall and partial stress and displacement changes of the steel tubular truss structure are analyzed and compared.(2)Taking a single-span homogeneous simply supported beam as an instance,the variation of modal parameters under snow load effects are analyzed.According to the force transmission form diversities of different structures,the snow load is considered to be continuously distributed and concentrated distributed,respectively.The variation of the modal frequencies and the mode shapes of the structure is analyzed when the additional concentrated masses are located in different positions of the beam.(3)The modal analysis of the steel tubular truss structure is carried out using the established finite element model.The variation of the modal frequencies and mode shapes under uniformly and non-uniformly distributed snow load effects are compared.Combined with the theoretical analysis results,some special changes of the modal parameters of the steel tubular truss structure under snow load effects are expounded.The mechanism of snow load effects on modal parameters are obtained.(4)The corresponding structural health monitoring system is designed in accordance to the actual situation of the steel tubular truss structure.The types,quantities,layout schemes and categories of physical quantities monitored of the used sensors are described.Using the data obtained from the structural health monitoring system,the static and dynamic responses of the structure before and after the snowfall are analyzed.The modal identification method is used to identify and analyze the modal frequencies and mode shapes of the structure based on the dynamic response data.The accuracy of theoretical analysis and numerical simulation results are verified.And the reliability of the monitoring data is proved.