| With the cable-strut bridge constantly building, a large number of cable-strut structure isapplied. Due to the installation of shock absorber, damping frame, supporting frame, cableclip, cable-strut structure presents a multi-bearing characteristics, so called multi-supportcable-strut structure. Multi-supporting cable-strut structure is the "lifeline" of the cable-strutbridge, its security is essential, while vibration parameters of the multi-supporting cable-strutstructure are important parameters of cable-strut bridge safety assessment in the design,construction, maintenance and reinforcement. Therefore, vibration parameters of themulti-supporting cable-strut structure have important practical significance. In this paper,based on the vibration characteristics of multi-supporting cable-strut structure, with method ofcombining theoretical analysis, model test and practical engineering applications, In-depthresearch of vibration parameter identification problem of multi-support cable-strut structure.The study includes the following sections:(1) The proposed resolution algorithm of transverse free vibration frequency ofmulti-supporting cable-strut. Constructing model of axial force beam with intermediate elasticsupport, and considering vibration influencing factors of intermediate elastic support, axialforce, flexural rigidity, end boundary conditions, and then the lateral free vibration frequencyanalytic formula of cable-strut structure with an intermediate elastic support is deduced.Frommulti-support cable-strut structure test, the frequency deviation of calculated results and theexperimental is small, the maximum deviation of0.5%. Therefore, the transverse freevibration frequency resolution algorithm of multi-supporting cable-strut structure is feasibleand calculation results is reliable.(2) Explore the relationship between transverse free vibration frequency and bearingstiffness of multi-supporting cable-strut structure. From multi-supporting cable-strut structuretest, the middle bearing stiffness and frequency of the cable-strut structure are inverselyproportional to each other. When the middle bearing stiffness is reduced by40%, frequency ofthe cable-strut structure increases to15%. So they are affecting each other larger. Therefore,the intermediate support must be considered to solve frequency of cable-strut structure, suchas shock absorber and cable clip of stayed-cable, shock absorber and cable clip of suspender,supporting frame of tie bar.(3) The proposed algorithm of vibration parameter identification of multi-supportingcable-strut structure. Algorithm of vibration parameter identification is anti algorithm oftransverse free vibration frequency of multi-supporting cable-strut structure, and is optimization identification method with the objective function of the difference betweencalculate frequency and test frequency as zero. The algorithm is identified vibrationparameters by frequency of multi-supporting cable-strut structure, such as the length, quality,flexural rigidity, bearing stiffness, internal force etc. A single parameter identification methodand multi-parameter identification method are established, based on the number of order oftest frequency and unknown vibration parameters of multi-supporting cable-strut structure.Single parameter identification method can only identify one unknown vibration parameters,according to whether the number of order of test frequency is equal to1, a singleparameter&single-frequency identification method and the single-parameter&multi-frequency identification method are established respectively. Multi-parameter identificationmethod needs to meet the number of order of test frequency more than the number ofunknown vibration parameters.(4) The proposed calculation method of cable-strut flexural rigidity, at the same time, itsresults can be provided iterative initial value for flexural rigidity identification ofmulti-supporting cable-strut structure. Cable-strut is composed of parallel steel wire orstrand.Cross-section of cable-strut structure is Irregular and not closed surface domain, whichis composed of dozens or hundreds of root wire cross-sectional. The structural characteristicsof the wire, is a wire section as the center, and other wire section tiered progressively outwardclosely packed with the form of a hexagon.Thus, based on cross-sectional structuralcharacteristics of cable-strut structure, moment of inertia of the wire can be hierarchicalcalculated. And then moment of inertia of cable-strut structure can be cumulative gotten.Finally, flexural stiffness of cable-strut structure can be calculated. So the formula has beenestablished,which composed of flexural stiffness of cable-strut structure, the number of thewire, the diameter of the wire.(5) The complex engineering application of vibration parameter identification method ofmulti-supporting cable-strut structure. Some vibration parameter of suspender and the tie barof Sanshanxi Bridge have been identified. Internal forces of suspender and the tie bar ofSanshanxi Bridge is important parameters for safety assessment. The best way to get internalforces of cable-strut structure is vibration method for the operation bridge, but there are tworeasons for the traditional vibration method cannot be accurately identified:1) the accuracy ofthe other vibration parameters influence the accuracy of the internal forces, and the otherparameters of cable-strut structure is very difficult to obtain accurately, especially bendingrigidity and supporting rigidity of cable-strut structure;2) traditional formula is someapplication formulas based on the vibration theory of end support cable-strut structure. In this paper, based on characteristics of the engineering, the following analysis have been done:1)the use of multi-parameter identification method for identifying vibration parameters ofsuspender, including flexural rigidity, bearing stiffness, internal force;2) the use ofsingle-parameter&multi-frequency identification method for identifying internal force ofsuspender;3) using a single parameter&single-frequency identification method for identifyinginternal force of short suspender and the tie bar. From the analysis results, the vibrationparameter identification method of multi-supporting cable-strut structure is very effective inengineering applications. So it has tremendous value. |
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