Buckling Stability Analysis Of High Pier And Piles System In Consideration Of The Pile-soil Interaction

With the implementation of Western Development Program in recent years, a lot of railways and highways are planned and built in West China. Because of landform factors, the bridges with high piers that span rivers, valleys and channels are key projects in these main lines of communication usually. Since the application of high strength materials in engineering, the structure of piles-high pier are tending to a towering and thin-wall changed state, bringing about the stiffness of structure dropping, and the stability issue of the system is particularly outstanding, it turns into the topic of important theoretical and practical significance in the area of bridges with high piers.Currently, due to the stress situation of high piers and pile group structure being complicated, its buckling analysis of research is still not perfect, most of existing research results use the buckling stability of pile and pure pier (assuming the pier bottom fixed supported) to evaluate that of the high piers of pile foundation system, but this method can't reflect common working principle of pile foundation and pier upper structure, it is difficult to reflect the actual bearing buckling characteristic of system in project. Based on this background, this paper on the basis of predecessors' achievements, and combining with the structural characteristics of high piers which Located in a mountainous region of western China, to high piers pile group buckling stability theory and methods for calculating system is studied. The main achievements are as follows:(1) Through related research achievements in domestic and international of comprehensive analysis, the paper deeply discusses and summarizes the load-bearing mechanism of high piers–piles structure, at the same time, it reviews and summarizes the buckling stability analysis of high piers , the present situation and development level of pile buckling research .(2) For pile foundation - single limb high piers structure, firstly based on force method principle, according to the principle of equivalent stress exchange, Will pile foundation into "column + level spring-loaded" structure, then will bridge pier and pile group foundation structure simplified as "second steps column (Several steps column) + level spring-loaded" stressed body. Then put forward a simplified calculation of buckling analysis of pile foundation- high piers, and with the calculation example, it proves that this method is practical.(3) In view of the actual project of pile foundation - both limbs pier to structure, according to the principle of equivalent stress exchange, Will the pile foundation into "∏" frame, and the whole high piers - pile foundation system is simplified to single span with double or multilayer frame structure. The paper adopts corner - displacement method, and deduces the analytical solution of the critical load calculation. Combining a practical example to analyze the rationality of this method, analyzes the influencing of the stability on the factors of the system parameters, obtained some qualitative conclusions.(4) Adopting finite element numerical simulation method by ADINA analysis program, calculates the buckling load of pile foundation-high piers system which under vertical load, and analyzes the internal force and displacement when the System presents a critical buckling condition.(5) Through changing the related parameters of the system, comparing the calculation result, analyzes the influence of system stability that under different structure stiffness, soil parameters, pier and pile length etc, to provide some reference for structural design and construction.