Study On Stability And Dynamic Characteristics Of Rigid Frame Bridge’s High Pier Considering Pile-soil Effect

The stability and dynamic response of high pier during construction and operation of rigid frame bridge are important indexs to evaluate the safety,operation state and bearing capacity of bridge structure.At present,there are many researches on the overall stability and structure dynamic response under seismic load of rigid frame bridge,but the research on high pier is relatively less.Most of the researches only aim at a particular bridge,and the research results are not universality and generalization.Interaction effect of pile-soil will increase the bridge structures’ vibration amplitude and change the stability of high piers.However,most literatures consider that the foundation’s constraint on the bottom of the pier is consolidation or analyze the stress of rigid frame bridge by a single pile-soil effect analysis model,which is not suitable for bridges built on soft foundation soil.Therefore,it is necessary to analyze the high pier’s stability and dynamic characteristics of the rigid frame bridge considering the effect of pile-soil.The main research works and conclusions are as follows:(1)Six different calculation models of pile-soil effect such as direct embedded model,equivalent embedded model,comparative rod model,three-spring model,six-spring model and the beam model on Winkler foundation were established.The three-spring model is identified as the optimal calculation model of high pier under the effect of pile-soil effect by analyzing the merits and drawbacks and the simulation accuracy of these different calculation models and comparing with the measured displacements of the pier top and the model values when the support project closuring and pushing.(2)The Rayleigh-Ritz method is used to derive the stability critical load calculation formulas of the high pier autogenous state,the maximum cantilever state and finished dead state,and the calculation errors between the calculation formulas and the finite element model are less than 10%,which verifies the correctness of formulas in this paper.At the same time,the stability characteristic values of high piers’ three states under different load conditions are analyzed,and the influence degree of different loads on the stability is obtained.Finally,the parameters analysis of the high pier’s stability is carried out by considering the material,the size,the height of the pier and the spring stiffness.(3)By using the Rayleigh and Southwell frequency synthesis methods,the formula of composite vibration fundamental frequency of pier is derived,and the correctness of the calculation formula is verified by comparing with the finite element model and existing specifications.Then the influence of different structural design parameters on natural frequency of high pier are analyzed,and it is concluded that the bending deformation and shear deformation of bridge piers have basically no effects on the natural vibration characteristics,and the main influencing factors are the translational deformation of the structure and the rotational deformation of the foundation.(4)The calculation formulas deduced in this paper have great accuracy and applicability,which can be used in the calculation and analysis of stability and vibration fundamental frequency in different construction stages of high pier or high-rise building structures.At last,the main work done in this paper is summarized,the main conclusions are arranged,and the outlook for the work that has not yet been completed is prospected.