Seismic Load Identification And Post-disaster Assessment Based On Structural Health Monitoring

After the earthquake,rapid state assessment of buildings can provide scientific basis for disaster relief and personnel resettlement.Accurate seismic load,fine building model and fast calculation method are the most important preconditions for state evaluation.Although seismic load can be obtained from the seismic network,due to the influence of soil and rock during propagation,actual load acting on the buildings is quite different from the records obtained from the seismic network.Overall model considering the interaction between soil and buildings can most accurately simulate the actual stress state of the buildings.However,the overall model is huge and requires a lot of time to solve,reducing the timeliness of post-earthquake state assessment.With the development and popularization of structural health monitoring system,the dynamic responses of structure can be used to indentify the seismic load.In recent years,the emerging finite particle method(FPM)has an excellent characteristic of parallel acceleration,which provides a new way of solving large-scale fine calculation.Based on the finite particle method,the research group developed FPM computing platform,which can be used as a powerful tool for time-history analysis of soil-structure system.This paper mainly focuses on three aspects:seismic load identification,seismic response analysis of soil-structure system and post-earthquake state assessment of buildings.For non-damped structures,a seismic load identification method based on Kalman filter in modal space is proposed,which identifies the seismic load with several orders of modal information and partial acceleration responses.The structural motion equation in absolute coordinate is first derived and then identification formula of seismic load is given.Examples of shear structure and bending structure are used to demonstrate the universality of the method.Sensitivity analysis of modal parameter and observation noise is carried out.The research shows that frequency information has a great influence on the results,and its accuracy should be improved.Under the influence of observation noise,the identification results can still be used to calculate the seismic responses of medium and long period structures,and the inter-story displacement error is less than 5%.The effectiveness and accuracy of the proposed method for non-damped structures are verified by shaking table test of a five-storey frame.For damped structures,the extended Kalman filter algorithm under unknown input is used to identify the seismic load.Especially for isolated structures,seismic load is identified without the information of isolation bearing.Numerical verification is carried out on the Bouc-wen isolation bearing model and the Bilinear isolation bearing model,respectively,and the unknown structural parameters,nonlinear isolation force and seismic load are simultaneously identified with limited acceleration responses.The displacement,velocity and strain responses are combined with the acceleration responses respectively to suppress the drift of identification results under the influence of noise.A multi-rate fusion method is introduced for data fusion with different sampling frequencies between multiple sensors.The effectiveness and accuracy of the proposed method for damped structures without information of isolation bearing and data fusion technology are verified by shaking table test of a frame with unkown isolation bearing.The basic theory of finite particle method and the computing platform FPM are introduced.The fiber beam model and material constitutive models used in the detailed analysis are described.The identified seismic loads on the soil surface are reverted to the soil bedrock by using the one-dimensional equivalent linearized site response analysis method.The problem of setting artificial boundary in the seismic response analysis of soil-structure system is studied in detail.Results show that the lateral boundary can effectively simulate the propagation of seismic wave in the semi-infinite space of soil,and the distance from the calculated range of soil to the buildings can be taken as one time of the thickness of soil layer,which can meet the requirement of calculation accuracy.Through seismic response analysis of 100 buildings,the effectiveness of FPM platform is verified.The seismic response of soil-structure system is compared with that of a single frame,which indicates the necessity of considering soil-structure interaction.A three-level and five-state evaluation system is proposed.Based on the response analysis of fine finite particle method model,the state evaluation results of component,floor and whole structure are given.Component evaluation is based on strain index of concrete and reinforcement.The floor evaluation of frame structure is based on force and displacement limit.The evaluation of frame shear wall structure is determined by the number of damaged anti-lateral members.The overall structural condition is evaluated by the most unfavorable condition of each floor.Finally,the evaluation results of 100 buildings and the evaluation rendering based on FPM platform are presented.The program of seismic response monitoring and display is developed.The dynamic response measured by the monitoring system is read in real time,and the maximum floor acceleration distribution,the maximum inter-story displacement angle distribution and the maximum instrumental intensity distribution are displayed.The time of the earthquake is determined automatically by means of multi-channel joint triggering,and the preliminary evaluation of the measured structure is presented after the earthquake.Through shaking table test of two frames,the practicability of the proposed program is verified.In this paper,a lot of simplifications and assumptions have been made on seismic load identification and seismic response analysis of soil-structure system.There are many details needed to be perfected and improved,which are explained at the end of the dissertation.