Study On A Novel Ring Spring-Rubber Three-Dimensional Vibration Isolation Bearing And Dual Control System For Vibration In Metro Superstructures

Considering the adverse effects of metro vibrations and seismic safety issues in metro superstructures,this paper introduces a novel three-dimensional vibration isolation bearing,combining ring springs and rubber bearing,along with a design method for a dual control system to enhance both vibration comfort and seismic safety in metro superstructures.The study employs theoretical analysis,experimental research,and finite element analysis to investigate the fundamental mechanical properties and vibration filtering effects of the three-dimensional isolation bearing.The vibration isolation performance and mechanisms are further validated through field tests.Additionally,the paper explores the dual control vibration performance of super high-rise structures within metro superstructures using finite element analysis and shaking table model tests.A metro vibration response spectrum is proposed to ensure accurate input for metro superstructures,and a design method for a dual control vibration structure is presented.Finally,the key parameters,such as vertical modal frequency and damping ratio of the dual control vibration structure,are analyzed through finite element simulation.The main research findings and conclusions of this paper are as follows:(1)A new type of ring spring-rubber three-dimensional vibration isolation bearing is proposed,and two types of specimens,3DIB-A and 3DIB-B,are designed and manufactured.The working principle,mechanical model,and design method of both 3DIB-A and 3DIB-B are first analyzed theoretically.Subsequently,their basic mechanical properties are examined through vertical pure compression,compression shear,and tensile shear tests.The test results show that the connection structure of the two types of isolation bearing specimens can connect the horizontal part and the vertical spring part in series,and realize the decoupling of the horizontal and vertical properties,and the deformation mode conforms to the design expectation.Both 3DIB-A and 3DIB-B exhibit high vertical bearing capacity,low vertical stiffness,and good stability.Notably,3DIB-A remains intact under a 2 MPa tensile force and 3 Tr horizontal deformation.The vertical spring component of 3DIB-B significantly reduces its vertical stiffness to about 1/12 of traditional rubber bearings,shows a good vibration filtering effect,reduces frequency vibrations in the range of 50 to 175 Hz,and effectively attenuates metro vibrations.(2)The modal dynamic characteristics of a fixed base floor(FB)and floors with coil spring bearings(CSB),ring spring bearings(RSB),thick rubber supports(TRB),and combined threedimensional vibration isolation bearings(RSB+TRB)are tested.The vibration isolation performance of these floors under metro vibrations is then evaluated through field model tests.The results indicate that the first-order cumulative mass participation coefficient of structures with vibration isolation bearings is significantly higher than that of non-isolated structures.Additionally,a lower vertical mode frequency corresponds to a greater cumulative mass participation coefficient.For analyzing metro vibration response,it is recommended to set the damping ratio of the concrete structure to 0.02,keep the first-order vertical modal frequency of the vibration isolation structure below 8 Hz,and maximize the first-order modal mass participation coefficient.This approach helps to reduce the main frequency band of metro vibration energy and the vertical high-order modal resonance of the structure.The key to the vibration isolation mechanism is to reduce the vertical stiffness of the structure,thereby enhancing its vertical vibration isolation performance.(3)To study the dual vibration control performance of super high-rise structures,a fullsize finite element analysis model is first examined and validated for metro and seismic vibration control design.The vertical metro and seismic vibration isolation performance of the structure is then tested using a scaled shaking table model test.The results show that the shaking table test model is well-designed and accurately reflects the dynamic characteristics of the structure.By lowering the vertical modal frequency and increasing the damping ratio of the structure,the vibration isolation layer using traditional rubber bearings can reduce the tendency of metro vibration amplification along the floors and provides effective metro vibration damping.This ensures that the metro vibration comfort and seismic safety of the structure meet design specifications.Additionally,the vibration isolation bearings significantly reduce the horizontal seismic response of the structure,satisfying the anti-overturning requirements for super high-rise vibration isolation structures.(4)Metro vibrations at various horizontal distances above a metro tunnel section were measured,and the metro vibration acceleration response spectrum at different locations was constructed.This response spectrum was used to generate random metro vibration acceleration time histories,and its validity was confirmed through comparative analysis.The results demonstrate that the harmonic synthesis method,based on the fitted target metro vibration response spectrum,effectively simulates several corresponding random metro vibration acceleration time histories,accurately reflecting the measured metro vibration data.This approach provides a good statistical envelope for the discrete measured metro vibrations.The application prospect of metro vibration response spectrum is wide,which provides reference for the calculation of metro vibration input.(5)Based on the analysis of key design points for the dual control structure of metro superstructures,a method for dual vibration control design of metro roof structures is proposed,along with a time-domain display algorithm for efficiently calculating the metro vibration response of the structure.The modal frequency and damping ratio parameters of the vibration response for structures using different types of bearings are analyzed.The results indicate that the three-dimensional vibration isolation bearing effectively reduces the vertical stiffness of the structure,increases the cumulative mass participation coefficient of the structural modal mode,and mitigates high-frequency vibration resonance.It is recommended that the vertical firstorder modal frequency of the metro roof structure be below 8 Hz,the modal mass participation coefficient be greater than 75%,and the damping ratio of concrete structures be set at 0.02.This dual control design method for metro superstructures provides comprehensive guidance for the engineering application of dual vibration control structures in metro roofs,summarizing the full paper’s findings.