Dynamic Simulation Study Of Multi-span Aqueduct Based On Model Updating

Aqueducts are commonly used in large-scale water conservancy projects such as agricultural irrigation projects and water diversion projects.They are playing an important part in alleviating the uneven spatial and temporal distribution of water resources in China.Aqueducts combine the structure of canals and bridges,so the structure itself is complex.Due to the simplification and idealization assumption in the simulation modeling process,the accuracy of the finite element(FE)model is decreased.Aqueducts are mostly build at earthquake-prone zone,so the anti-seismic of aqueduct is very important.And aqueducts are mostly located in the open or valley zone with large wind speed.The wind resistance of the aqueduct body is more prominent,especially for the high bent aqueduct structure with weak lateral stiffness.With the development of society and technology,the safety of aqueducts has been put forward higher requirements.Based on the FE simulation technology,combined with technology of vibration test,information fusion and numerical simulation,this dissertation studies the aqueduct under fluctuating wind and seismic.The aim is to explore the contact characteristics and response law of aqueduct,and explore the explicit dynamic analysis of aqueduct preliminarily.The main work as follows:1.Multi-span aqueduct simulation system.First,establish simulation system of three-span aqueduct with fluid solid interaction(FSI).And the nonlinear contact between two spans was also established.The modal frequencies of single-span model,connectionless multi-span model and consolidated multi-span model were calculated,and the applicability of the contact model is verified by comparing with the measured frequencies.2.Finite element model updating.A FE model updating method based on information fusion and response surface method(RSM)was proposed.Build design space of the parameters and the frequencies by central composite design(CCD).The dynamic response of the aqueduct under the environmental excitation was measured.The test signals that cover three spans of aqueduct were processed to obtain complete and effective frequencies by a signal de-noising method based on CEEMDAN-SVD and an information fusion algorithm based on variance contribution rate.The first four modal frequencies were extracted as the target to optimize the response surface.Compare the modal frequency of the updated FE model and the frequency after processing based on structural vibration test,and the results show that the calculated frequency of the updated FE model and measured frequency are in a good agreement.3.Wind & seismic response analysis with cross-contact.The fluctuating wind was simulated by the auto-regressive moving average(ARMA)model.The nonlinear contact solution of the aqueduct under fluctuating wind was carried out.Then,the wind-induced and seismic responses of aqueduct structure were analyzed.The contact characteristics and wind & seismic response of large aqueduct span were explored,which provide technical reference for the optimal design of aqueduct structure.4.Explicit dynamic analysis based on ANSYS/LS-DYNA.A simple single-span simulation system of aqueduct was established,which consists of a tank body,bent and rigid ground.By removing the failure component,fluctuating wind was applied on the FE model under normal operating condition.The aim is to preliminarily explore the process of explicit dynamic analysis and the idea of collapse test of aqueduct.