Research On Ice-induced Pier Vibration Model Test And Ice Load Identification

Dynamic interactions of ice with structures,ice-induced vibrations and ice loads identification,are still the hot and key problems in ice engineering.However,due to the complexity of ice mechanics,a widely accepted physical model describing the mechanism of dynamic ice-structure interactions and ice-induced vibrations has not yet been well developed, especially the methods for identifying dynamic ice loads are not so satisfactory.As bridge structures play important roles in ocean engineering and traffic hinge project over the river or sea,the problem of ice-induced Pier Vibration can not be ignored.Considering all the factors, the main work of this thesis is to deal with the three following topics:Firstly,Model test is an important method in ice force mechanics research but the development of dynamic ice force model test is not mature.In this paper,the idealized similitude laws theory for dynamic ice force model test is enduced based on static force model test.Then,in order to apply better,a kind of modified similitude law is proposed based on reasonable assumptions.For further studies,this method is vertified with a ice-induced pier virbration example,and the results indicate that the new modified similitude law is feasible to study dynamic ice force model test.Secondly,to study the mechanism and characteristics of ice-induced pier vibration, taking a pier for example,a test procedure is designed,and a type of ice force FBG sensor is also developed to measure ice force in the process of test.Then,a laboratory test is performed for the simulation of ice-induced vibrations of a pier structure,in which DUT-1 model ice sheet are driven by the trailer at different velocity.Both the ice sheet time histories and the response of pier are measured.From the test phenomenon and measured results,some conclusions are drawn:The predominant failure of DUT-1 ice sheet are seperatey yield failure under low velocity and crushing failure under middle or high velocity;The magnitude of the measured ice loads coincides with that of the measured ice force in Bohai Sea;The trend of maximum ice load increasing with the ice velocity is obtained through the results calculated and the dynamic ice loads has the abundant frequency contents by the Fourier spectrum analysis;The measurement of displacement and acceleration of pier are small but the trend of maximum adds with the ice velocity increasing.Besides,the predominant vibration of pier is first frequency known by the Fourier spectrum of displacement;Finally a FEM model of ice-induced pier vibration considering the hydrodynamic pressure effect is established,the numerical simulation results show:the variable regular of measured value as time is nearly the same to the calculated value,the maximum error of which is 30%.So the test results are satisfied in some extent.Finally,to develop ice loads identification,precise time integration method is proposed to apply.Based on the principle and some assumption,an improved dynamic identification method for proportional damping system is presented by linear interpolation within discrete time.Then,the results of numerical examples show that the precise time integration method compared with other methods is much more simple in form,and can be effectively applied to to identify all kinds of dynamic loads in the engineering.