Experimental Investigation And Numerical Analysis On Stability Behavior Of Steel Bridge Towers

Steel bridge towers have been used in suspention bridges and cable-stayed bridges for many years in other countries, however, China has been still in the primary stage of practicing this type of towers. With the constuction of long span bridges and new types of bridges, steel bridge towers will have wide application in bridge engineering. But in China, the clauses on the steel bridge towers are still blank in the present steel bridge design code, relevant researches are not enough, and the clauses can be refered to in foreign codes are also limited, which produces a large difficulty to the design and construction of steel bridge towers. Stability is one of the key technologies to determine the ultimate bearing capacity of steel bridge towers, it's necessary to prctice the theory researches and experiment researches for the immature stability theory of steel bridge towers in China. Therefore, stability behavior of steel bridge towers has been studyed in this dissertation, not only practicing the finite element analysis, but also carrying out an experiment on steel bridge tower segment specimen. Based on the researches, the mechanic behavior, local buckling mode and failure mechanism of steel bridge towers's local buckling can be obtained, which can provide references to stabilty researches and project design. In detail, the following aspects are investigated:1. The paper summarizes the historical development, present application and research survey of steel bridge towers in China and other countries, analyses the structure and characteristics of the towers, and proposes the stability research of steel bridge towers.2. A steel bridge tower segment specimen having typical type and structure was designed and fabricated according to the structure and sectional dimension of the established steel bridge towers in the world, the specimen was tested under axial compression with a 20000KN compression testing machine, and the ultimate bearing load was obtained from the test.3. According to the deformantion and stain laws of the specimen before the local buckling and after, the local buckling mode and mechanic behavior of the specimen can be gained, and the local buckling failure mechanism was also presented.4. The finite element model of the steel bridge tower segment which using shell element was built, based on the finite element methods and the stablity theories, the stablity analysis on the first type and the second type were proceed respectively. By comparison of the numerical results and the test results, it shows that the second type of stablity analysis was in good agreement with the test results.5. On the basis of the numerical results and the test results, some suggestions on the stability analysis and stabily design were proposed finally. During the stability analysis of the project, the first type of stability analysis can be proceed due to its fast calculation in the scheme comparison and the conceptual design, but if make accurate analysis and detail design, the second type of stability analysis including both material and geometric nonlinearities, as well as the initial local deformation must be carried out, which can give the actual stability ultimate bearing capacity.