Spatial Stability Analysis of Long Span CFST Arch Bridges ZHAO Changjun, WANG Fengjun, CHEN Qiang, XU Xing (Department of Civil Engineering, Zhejiang University, Hangzhou, China) The elastic and geometric nonlinear calculations of Hangzhou line have obtained some important conclusions. It has certain reference for the construction of such bridges. effect.
0 Overview Compared with the reinforced concrete arch bridge and the completed arch bridge, the concrete-filled steel tube arch bridge is made of high-strength materials such as steel pipe, which makes the self-importance greatly reduced and the span is large. The other steel pipe is used as a stiff skeleton, which is a self-erecting system and can be manufactured at the factory. In the construction site erection and erection, the construction is convenient and the cost is reduced. Therefore, the concrete-filled steel tube arch bridge has developed rapidly in recent years, but with the large span, the stability problem has become one of the main factors restricting its development. Reinforced concrete arch bridges and completed arch bridges. Generally, due to the small span, the arch ribs are relatively large, and the stability problem is not outstanding. The strength and erection method of the material is the control factor. Usually, the arch rib is equivalent to a compression rod. Stability check For long-span CFST arch bridges, this method can only be used as a simple estimation of the preliminary design stage. Only by using the finite element method for spatial analysis can the true stability of the structure be reflected. 1 Calculate the stability problem of the theoretical arch bridge from space. The instability characteristics are divided into two types: in-plane instability and out-of-plane instability. The first type is the equilibrium branch problem, and the second type is the extreme point problem. The arch bridge is under pressure. The main compression-bending structure, strictly speaking, the instability of the arch is the second type of instability but the first type of stability problem of the arch. The mechanical condition is pure and clear, and its critical load approximation represents the upper limit of the second type of stability problem. Therefore, it plays an important role in both theoretical analysis and engineering application. 1.1 Pure compressive arch space stability analysis line elasticity, pure pressure arch under critical load The equilibrium equation is: matrix, which is only related to the axial force of the member; W is the displacement of the unit node; V is the load stability factor.
Equation (1) is a eigenvalue problem, and its minimum eigenvalue is meaningful in engineering. It can be applied to various iterative methods, such as inverse vector iteration method, subspace iteration method, etc. It can be easily solved for 1.2 compression arch space geometry. Linear Stability Analysis The geometric nonlinearity of an arch bridge mainly refers to the deviation of the arch axis from the load pressure line under load, because this deviation is unavoidable. For example, during the construction phase, the pressure line changes continuously with the erection process, the construction pre-camber setting, various construction deviations, and elastic compression of the arch axis. Therefore, strictly speaking, the instability of the arch belongs to the geometric nonlinearity of the second type of unstable arch, which belongs to the problem of large elastic deformation. It is solved by the full-scale method, and the concept is clear and easy to understand. The configuration of the object before deformation is known, and is taken as a configuration. The deformed configuration is to be sought. The metric used for the meter is the Kirchhoff stress and the nonlinear equilibrium equation of the Green strain arch bridge structure can be written as: load; W, is a function of W, so; When the safety factor (heart 6) is stabilized, it is considered safe and reasonable.
Concrete-filled steel tubular arch bridges are the development trend of long-span arch bridges. Nowadays, there are many arch bridges built in China, but there are many experiences of bridge-like types. This practice of advanced theoretical research can not be solved in a short time. It will leave unpredictable hidden dangers, resulting in unpredictable loss problems that have not yet been resolved, such as the interaction between steel pipes and concrete. At present, it is simply to superimpose the compressive and bending resistance properties of the elastic phases of the two materials, which cannot be considered. Its advantageous interaction, so that the superiority of the composite material is not fully applied. For this new bridge type, there is a lack of corresponding design and construction specifications, such as full bridge stability analysis.
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