Research On Flow-induced Vibration And Vibration Reduction Of Gantry Crane Beams

The gantry crane is an important special logistics equipment in engineering practices,whose stability and safety has always taken a very significant role in its structural design.The wind load,as one of the main loads of the crane,would directly or indirectly destory the crane through the coupled vibration,which has attracted more and more attention.Especially in recent years,with the development of the crane towards much higher,larger and more flexible structures,as well as greater intensity and freqnency of wind loads with the tendency of global warming,the problem of wind-induced vibration(WIV)of crane becomes more and more prominent.Therefore,the research on wind-induced vibration of the crane and the related vibration reduction design has much important scientific and engineering significance.In this doctoral dissertation,based on the wind-induced effect of the basic components of the gantry crane,the wind induced vibration responses of cranes’ structures including the main box girders and their vibration reduction designs are systematically studied.The flow induced vibration response law of the structure with different cross-section,size,mass ratio,and damping ratio is discussed in detail.As the same time,combining with the concept of bionics and the idea of light film attachment,a new design method of reducing resistance and suppressing vibration of box girder structure is explored.The research on wind-induced vibration and vibration reduction of crane structure mainly includes the following contents:(1)By using CFD/CSM(Computational Fluid Dynamics / Computational Solid Mechanics)coupling method and Open FOAM computational platform,the vortex induced vibration(VIV)of a circular cylinder at low Reynolds number is calculated.Comparing to the reported literatures,a good agreement of present circular results is taken,which verify the reliability and accuracy of the present coupling calculation method,so as to lay a foundation for subsequent relevant and discussion for the whole dissertation.(2)The wind-induced vibration of the rectangular beam structure with different side ratios are analyzed and compared by using two different calculation methods for constant Reynolds number and constant structural stiffiness.The variation law of the vibration responses of the rectangular cylinder with different side ratios is obtained and discussed in detail.Then,WIV results with different length of the extended flange and various side ratios of the outer rectangular for the box girder flange structure are conducted and compared.The general law of the response under the flange structure is also summarized.According to the relationship between structural characteristic parameters and WIV response,some meaningful designal strategies of structural drag reduction and vibration reduction are explored,which could provide a reference for the gantry crane structural flange design.(3)The vibration response of the unique trapezoidal structure of the crane in the flow field is discussed.Under the practical condition of long-span and heavy load,the cross-section of the gantry crane’s main girder is usually designed as the trapezoid.Due to its asymmetry to the inflow of the flow field,the WIV response of the trapezoidal structure would be different from that of a rectangular structure,which is called as the “double-period” mode.Firstly,WIV of a trapezoidal structure with specific size is studied,and the influence of structural asymmetry on the vibration response is discussed through the unique vibration responses,frequency ratios,aerodynamic forces and wake structures.Then,the influence of structural asymmetry on vibration response and flow field asymmetry is explored and discussed by changing the ratio of long and short sides of trapezoidal cylinder,which is finially taken to give some helpful advices for the vibration reduction of the trapezoidal cylinder.(4)The influences of mass and damping of the box girder of the crane on WIV are analyzed.The response of WIV with various mass and damping under common box girders are investigated,especially for the trapezoidal box girders.Firstly,for different mass ratios,the variation law of vibration responses for the trapezoidal girder structure are discussed,and various classes of mass ratios are identified through WIV responses.Then,by comparing WIV results of different damping ratio of structural system,the influence of damping ratio on convective vibration is obtained.Finally,according to the variation law of WIV response under different mass and damping,effective measures to reduce structural vibration response are obtained,so as to provide reference for the gantry crane design.(5)Considering the wind-induced vibration characteristics of box girder under different shapes,size,and physical parameters,a new structural bionic vibration reduction design scheme based on boxfish is proposed.The bionic shape of the mouth of boxfish is designed,and on the basis of the concept of light film attachment method,some different attachment shapes including the bionic attachment strategy are proposed.Then,the aerodynamic parameters and vibration response of WIV for crane box girders under different attachment schemes are investigated and compared through the wind tunnel test as well as the numerical simulation.The aerodynamic response results for the crane box girders with both attached and non-attached structures are compared to analyze and verify the vibration and drag reduction effect of the attached models.According to the structural response characteristics of gantry crane in natural wind field,this thesis makes a systematic research and analysis on the wind-induced vibration response of the box girder structure of the crane,which lays a foundation for supplementing and improving the relevant contents of cranes’ wind-induced vibration and its vibration reduction design in the Design Rules for Cranes: GB/T3811-2008.