Optimization Design Of Periodic Surface Wave Barriers Under Arbitrary Angle Incidence

Periodic surface wave barriers can isolate surface waves in a specific frequency range due to the band gap.The performance of band gap is closely related to the material distribution of wave barriers.Therefore,in this thesis,the material distribution of wave barriers is designed by topological optimization considering oblique incidence of surface waves,so as to achieve precise control of band gap and better vibration isolation/reduction effect.This thesis carries out the design of periodic surface wave barriers by topology optimization aiming at the maximum relative or absolute bandwidth of Rayleigh surface waves from 2 to 20 Hz.Genetic algorithm(GA)is used to solve the topology optimization problem of three-component periodic surface wave barriers under vertical incidence.Utilizing the partial differential equation(PDE)module in COMSOL calculation of the dispersion relationships of the partially embedded periodic wave barriers and the periodic trenches under arbitrary angle incidence are realized.On this basis,the combination design of the partially embedded periodic barriers and the topology optimization design of the periodic trenches are carried out respectively.Numerical simulation of EI Centro seismic waves with oblique incidence verifies the seismic isolation effect of the designed wave barriers.The main conclusions are as follows:(1)The proposed topology optimization framework can obtain optimized structures with wide bandgaps under different design objectives and constraints,and the convergence of optimization results is stable.(2)Topology optimization results of three-component periodic surface wave barriers in the case of vertical incidence show that:(i)The introduction of rubber is beneficial to improve the band gaps performance of the wave barriers.For the same configuration,the higher the filling rate of rubber,the lower the frequency at the lower edge of band gap of the optimized structures is.(ii)The larger the design area is,the lower the frequency at the lower edge of the band gap is,and the larger the relative bandwidth of the band gap are.(iii)Symmetry of the design region has little influence on the relative bandwidth,but the lower the degree of symmetry is,the more complex the optimized configurations are.(iv)The optimized wave barriers attenuate surface waves by converting them into shear body waves far from the ground or absorbing the energy of surface waves.(3)The bandgap characteristics of partially embedded periodic wave barriers under arbitrary angle incidence are completely different from those under vertical incidence.With the increase of the incidence angle,an excellent and stable zero-order band gap will appear.The combination design of wave barriers arrangement is realized by using the characteristics of the zero-order band gap.The combined wave barriers can effectively isolate the surface waves with oblique incidence in a specific frequency range.(4)The representative configuration obtained by topological optimization of the periodic trenches under arbitrary angle incidence can isolate surface waves at a specific frequency range with an incidence angle from 0° to 30°.(5)For EI Centro seismic waves with oblique incidence,the surface acceleration amplitude behind the barriers can be effectively attenuated by arranging the designed combined wave barriers.