Research On The Stable Ultimate Load Of High Piers And Long-Span Continuous Rigid-Frame Bridge With Initial Imperfections

With the progress of science and technology, the transport undertakings developing rapidly, the highway construction is spread continuously to the western mountains at a breathtaking speed. Due to topographical terms, highway building tends to be crossed in the mountains that continuous rigid frame bridges with high piers are widely used in mountainous areas. Due to the high pier, the stability problems become especially remarkable. This thesis aims at the stability of Yesanhe Bridge in its construction stage, a long-span continuous rigid frame bridge with high piers in the west of Hubei province, which is situated in the national highway from Shanghai to Chengdu City. The main research works are summarized as follows:1. According to the first instability modal and the limitation of standard, considering the initial geometric imperfections, the stability of single-leg high pier that has both in-plane and out-plane initial geometric imperfections is studied in this paper by means of the non-linear finite element method (FEM), which will reduce greatly its stability of the bearing capacity as a result, especially in the case of double geometry. The stability of high pier with the local material imperfections in the framework is computed for the location where the most harmful material defects happen, and the relationship between the stability of bearing ability and the strength of local materials.2. By means of Ritz method, the critical load formulation under the high cantilever state of thin-walled high piers is deduced, and the structure stability in the high cantilever state is also computed. The combined model by the space entities and beam units is built for analyzing the stabilities of thin-walled high piers under the high cantilever state with various constructions by ANSYS, such as wind load, the initial deflection on a stump, hanging basket falling and various unfavorable load combination. As a result, load safety factor of the framework with initial geometric imperfections, and the differences between the first and second category of stability considering double nonlinear characteristic are obtained in this paper.3. The imperfections of the structure with initial geometric imperfections change constantly in the construction, so this thesis makes that as a basis for the whole bridge stability analysis. Based on the measured temperature taken in the health monitoring, effects on the stability of the structure with initial imperfections in the local and overall temperature load are discussed respectively. And the effects of auto-load on the framework with initial imperfections are also computed and analyzed.This study will provide the theory instruction for the problem of stability of the Yesanhe Bridge and the reference to the research for this kind of bridge stability which considers the initial imperfections.