Researches On Ice-induced Pier Vibration And Compound Identification Of Pier Structures

Researches on dynamic ice forces acting on bridge structures over rivers or seas and ocean platforms is one of the important tasks of the ice-resistance response analysis in cold areas.The vibration analysis of bridge structure as the traffic keys over sea and river need to be carefully and is of paramount importance.Considering almost all the parameters can also be controlled conviniently and united reasonably in the model test,performing model test in laboratory is an effective way to find the problems directly in prototype measurement and field experiment,to analyze the relations between each parameter,and to generalize the general laws.All of the above can provide important references for the ice-resistance design in cold areas.Therefore,a series studies of ice-pier vibration are performed from different aspects in this paper.The main work of this his thesis is summarized as follows:(1) Ice response spectra is proposed based on the idea of a seismic response spectra analysis of structures.Firstly,ice response spectra on the basis of power spectra density function is established;Secondly,based on the assumption of quadratic parabolic interpolation method,the nonlinear interpolation analysis method of ice response spectra is studied from both theoretical and practical points of view,and the successive computation formulas including ice displacement,velocity and acceleration response spectrum are deduced by Duhamel integral.Furthermore,to analyze the effectivity and applicability of the method, the real temporal curves of ice pressure are used to be studied.The results show that the presented method is more convenient and accurate to study the structural response induced by ice force,also it can be effectively applied in the design of ice resistance.(2) The degree of accuracy extent of model design directly relates to the success or not of model test.In this paper,to study similitude laws for dynamic ice force model test which is always a hot problem in ice mechanics,a new modified similitude law for dynamic ice force model test is proposed based on ice-induced virbration theory and two reasonable assumptions.So that more precise results of model test can be obtained to evaluate the possible damage of the prototype structure excited by ice loads.To verify the validity and applicability of the similitude law,a ice-induced pier vibration is examplified,and the similitude ratio of time,displacement,velocity and acceleration are analysized in theory, respectively. (3) To solve the parameter identification problem of the flexible arm structure with known loads information or other incomplete input information,an improved physical parameter and load inversion method in time domain is proposed in this paper.A flexible arm pier structure with unknown imput,as the numerical example,is given to verify the new algorithm.Furthermore,precise time integration method is introduced to identify dynamic ice loads due to its facility and applicability.Then,a numerical example and real test datas are performed to investigate the identification effect.The results show that both the first algorithm and the precise time integration method can be effectively applied to identify dynamic ice loads in practical engineering.(4) Based on the modified similitude law,a laboratory test is performed for the simulation of ice-induced vibrations of a pier structure in state key laboratory of coastal and offshore engineering,dalian university of technology.In the model test,the response characteristic of pier structure introduced by ice loads is analysized,and the damage form is also studied.Furthermore,the results obtained from model test and FEM numerical calculation are compared.So that the improved similitude law for dynamic ice force model test also can be got to vertified both in theory and practice in further.(5) To consider the fluid-structure coupling effect on the response of bridge piers in deep water,on the basis of fluid mechanics principle,nonlinear Morison equation of the pier structure is established under different loads action.By the numeric analysis,the pier-water coupling vibration responses of bridge pier are studied and compared deeply under earthquake, ice loads and wave force action.As the effect of added mass of water and the coupling effect of fluid-structure are both considered in the nonlinear Morison equation applied in this paper, the probem of piers-water coupling vibration can be settled fundamentally,and it is feasible to the piers design.