Seismic performance of arch-inverted siphon based on a large shaking table test
[Objective]Recently,several large-scale water conservancy projects have opened in China to alleviate the regional water shortage problem.Inverted siphon structure,an essential part of long-distance water transfer projects is widely used in interbasin water transfer projects.Arch-inverted siphon has characteristics of a water pipeline and an arch bridge,and the mass of the upper water body is vast,which is"top heavy"compared with the supporting structure.Structural seismic problems are prominent;however,studies on the seismic performance of this type of structure are fewer.Therefore,this study conducted shaking table tests to study the effects of changes in the state of water conveyance and ground vibration excitation categories on the seismic response of the structure.[Methods]Based on similarity theory,this study designs a similar relationship of Longchuan River inverted siphon,assembles a corresponding similar model using Plexiglas and steel processing,arranges a certain number of acceleration sensors and displacement sensors in the critical parts of the model,and then,performs 13 shaking table test conditions,which consider the state of water conveyance,the category of ground vibration,and the direction of ground vibration excitation.Dynamic acceleration response of similar models in the tests is collected by the sensors,and the acceleration response in the white noise sweep test can identify the intrinsic frequency of the structure,whereas that in the ground vibration excitation test can be converted into the displacement response by integrating the response to compare and analyze the changes in structural self-oscillation characteristics,peak acceleration,and peak displacement under different working conditions.[Results]The shaking table test results revealed the following points:(1)The acceleration response of the Longchuan River inverted siphon had a pronounced amplification effect under the increase in elevation,and this effect was nonlinear growth,X-direction excitation—the maximum response of the structural acceleration occurs at the top of the pier,and Y-direction excitation—the maximum response of the structural acceleration occurred at the steel pipe.(2)Under different water transfer conditions,the structural period would be extended after the mass of the upper water body was increased,which was far away from the seismic excellence period and reduced the seismic action on the structure.This effect was greater than that of the increased inertia force caused by the increase in mass,which reduced the dynamic response of the structure to a certain extent,and the seismic performance was improved.(3)Under different ground shaking excitations,the same intensity would affect the structure differently.The structural response was strongly correlated with the frequency component of the excitation waveform at the fundamental frequency of the structure,and the larger the frequency component in the fundamental frequency band,the larger the response.[Conclusions]These results reveal the effects of water conveyance state and ground vibration type on the seismic performance of arch-inverted siphon structures,which can provide theoretical guidance for the seismic design of such structures.
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