Scale Model Design Using Attached Plates And Its Application For Underwater Shaking Table Test Based On Coordinative Similitude Law

Bridges in the water environment are subjected to hydrodynamic effects under earthquakes,which have an impact on the responses and seismic performance of the bridges,and have received extensive attentions from scholars in recent years.The development of underwater shaking table test equipment provides supports for the seismic behavior study of engineering structures in the water environment.Modern shaking table test methods have established a relatively complete scale theory within the elastic range.However,in a water environment,due to the fact that the density of the water body cannot be changed,the hydrodynamic action on the bridge cannot fully satisfy the law of similarity.During the test,the effect of the hydrodynamic action is reduced in the scaled model.In recent years,the coordinative similitude law of underwater shaking table tests has theoretically solved the problem of coordinated scaling between hydrodynamic and seismic forces,but there are many problems in practical applications.For this reason,this paper proposes a scale method using attached panel based on the theory of coordinative similitude law.Through the numerical simulation of the bridge pier model,the dynamic effect of the water on the bridge pier and the working performance of the scale method using attached panel are studied.On this basis,the applicability of the scale method using attached panel to the entire bridge model is studied.The main research contents and results of this paper are as follows:(1)A scale method using attached panel for underwater shaking table test considering the coupling effect of unidirectional ground motion and hydrodynamic force is established,and the shutter type attached panel and its design formula is proposed.Through the use of ADINA software for finite element simulation,the response of the structure prototype,the traditional scale model and the scale model using attached panel under different ground motions and different water depths are carried out to verify the feasibility and applicability of the scale method using attached panel.According to the finite element simulation results of bridge piers,the response simulation error between the scaled model using attached panel and the prototype pier is less than 6%,while the pier response simulation error of the traditional scale model and the prototype will increase with the rise of water depth,up to 20%.(2)Based on the above research,a two-way scale method using attached panel considering the coupling effect of two directional ground motion and hydrodynamic force is established.Through the finite element simulation,the response of the structure prototype,the traditional scale model and the scale model using attached panel under different ground motions,different pier section heights and different water depths are carried out to verify the feasibility and applicability of the two-way scale method using attached panel.According to the research results,the test simulation accuracy of the two-way slab scale model under two-way ground motion is close to that of the one-way earthquake slab scale model.According to the research results,the experimental simulation accuracy of the pier under two directional ground motions with the two-way scale method using attached panel is close to that under the unidirectional ground motions with the one-way scale method using attached panel.(3)The applicability of the scale method using attached panel in the overall model of seismically isolated bridges in the water environment is studied.According to the research results,for the isolation model with a long period,the hydrodynamic effect on the structure response under ordinary ground motions can reach 11.59%,and the hydrodynamic effect under pulse-like ground motions can reach 28.11%.When the traditional scale method is used,the response of the scaled structure is smaller than the analysis result of the prototype structure,and the maximum error can reach 24.09%;the traditional scale method cannot effectively simulate the hydrodynamic effect,which may cause an overestimation of the seismic performance of the bridge.When the scale method using attached panel is adopted,the simulation errors are all less than 5%.