Force Transfer Characteristics And Dynamic Stiffness Of Cable Supported Bridge Based On Stress Wave Theory

Different from the holistic vibration analysis,the local effect caused by the energy redistribution at the discontinuity of the structure should be considered for the wave response analysis as well as the delay effect caused by propagation efficiency disparity of different propagation paths.In addition,the dynamic stiffness matching of structural system based on wave analysis is a problem worthy of attention since there are many discontinuous and force propagation paths in the beam-cable coupled bridge.The propagation characteristic of the stress wave excited by the vehicle load in the structure during the operation is closely related to the dynamic response of the structure.Therefore,the propagation characteristic of the stress wave is the core factor that restricts the selection of the bridge configuration and even the basis for judging the merits of structural dynamic stiffness design.Base on theoretical analysis,numerical simulation and experimental approach,a systematic study,including accurate and efficient calculation of wave response,propagation mechanism of stress wave,reasonable evaluation of structural force transfer efficiency and concept of universal dynamic stiffness design,was carried out in the present work,which had comprehensively solved the issue of force transfer characteristics and high stiffness design problems of beam-cable coupled structure.Result of this study could provide scientific basis for relevant theoretical revision and innovative engineering practice.The main research work of this dissertation are as follows:(1)Aiming at the calculation of the solution of stress wave transfer function of beam-cable coupled structure,considering the influence of structural damping and prestress of beam,as well as the effect of moving impact load and additional impact load,the calculation formula was constructed based on the MRRM.The wave response of the structure was analyzed as the superposition of multiple types of stress wave transfer functions,and the physical significances of the stress wave transfer functions were discussed.The types and propagation efficiency of flexural waves under various impact loads were preliminarily discussed,and the evaluation theory of structural force transfer efficiency for wave energy was finally established.(2)To improve the practicability of the stress wave propagation theory and solve the inherent problems of the traditional method of reverberation-ray matrix(MRRM)in matrix inversion,the wave response was transformed into the superposition of the multi frequency stress wave transfer function by combining the idea of discrete fourier transform and the stress wave superposition theory.Work mentioned above implied the dynamic response mechanism of the structure,that is,the superposition and propagation effect of the stress wave.Based on experimental research and numerical analysis,the spectrum characteristics of stress wave in the beam-cable coupled structure were proved,and the computational efficiency of wave problem was further improved.The calculation method and formula of Kelvin-Voigt damping coefficient were proposed to find out the reasonable value range of internal damping coefficient.Theoretical derivation was carried out and the mathematical relationship between mechanical parameter damping coefficient and engineering measurable physical quantity damping ratio was established.The internal damping coefficients of three bridges were obtained through experimental research as the basis for subsequent research.So far,the construction,perfection and parameter determination of stress wave propagation analysis theory in beam-cable coupled structure under impact load had been completed.(3)To find out the relationship between the stress wave propagation characteristics and the macroscopic response of the structure,the dispersion relationship,frequency spectrum characteristics,dispersion characteristics and propagation velocity of the flexural wave and the longitudinal wave in the beam-cable coupled structure were studied.The correlation between the structural response and the design parameters was proposed from the perspective of the stress wave propagation,and some structural design suggestions were obtained.Based on the basic principle that the phase difference in the wave function affects the wave effect,the basic concept that the propagation efficiency determines the significance of the wave effect was formed,and thus the relationship between the wave response analysis and the holistic vibration analysis was established,that is,the wave analysis is a general method of dynamic analysis while the holistic vibration analysis could be used as a simplified calculation method if the structural propagation efficiency is extremely high.(4)The research results of the propagation characteristics of stress waves in beam-cable structures under impact loads were implemented into the structural dynamic stiffness perception and design practice.Based on the stress wave theory,the dynamic stiffness analysis theory of the stress wave propagation path was constructed,and three intuitively perceptible dynamic stiffness structure concepts were condensed,which led to the "shortest propagation path concept".Combined with the distribution law of wave energy on different propagation paths at the node,the idea which is the force transmission efficiency and dynamic stiffness of the structure have inherent unity was confirmed,and the dynamic stiffness matching criterion was proposed.Through the verification and application studies,it was pointed out that it is feasible and meaningful to improve the overall transmission efficiency and the overall dynamic stiffness of the structure at the same time.(5)Based on FEA,dynamic experiment of bridge and scale model,the theory of stress wave propagation analysis was verified,and propagation characteristics of stress wave were studied.