Calculation method of variable cross-section water retaining dam load effect caused by earthquake

Abstract

The invention discloses a calculation method of a variable cross-section water retaining dam load effect caused by an earthquake. The calculation method comprises the following steps: firstly, determining the beam depth h, the reservoir water height Z, the slope coefficient b and the checking point height L0 of a water retaining dam, wherein the linear change of the cross section area L of the water retaining dam along with the reservoir water height Z meets L=L0(1-b[Eta]), and [Eta] is equal to Z / L; then, according to the shape and the material characteristics of the water retaining dam, determining the mass M, the rigidity matrix K and the damping matrix C of a solid; and according to the shape and the compression characteristics of a water stream, determining the mass S, the damping matrix and the rigidity matrix H of fluid. In conclusion, the values of the displacement, the speed and the accelerated speed of the water retaining dam are calculated so as to judge the safety performance of the water retaining dam. The calculation method is high in calculation accuracy, numerical calculation damping generated by the calculation method is not in the presence, equation solving does not use numerical integration operation, a big step size can be taken without losing calculation accuracy, and calculation efficiency is improved.

Description

technical field [0001] The invention relates to a method for calculating the load effect of a variable-section retaining dam caused by earthquakes. Background technique [0002] When dams and water transfer projects vibrate under dynamic loads, changes in the fluid field in contact with the structure will be caused, and changes in the fluid field will in turn lead to changes in the stress on the structure, forming a fluid-solid coupling problem. The characteristics of the fluid-solid coupling problem are: the calculation domain includes not only the solid domain but also the fluid domain, and the solution of the equation cannot be carried out only in the solid domain or the fluid domain; Expressed in the form of speed and acceleration, the load effect is used to judge the safety performance of the water deflector, and better serve engineering design, construction and safe operation; [0003] Westergaard believes that assuming that the dam surface is vertical, the depth of t...

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Problems solved by technology

[0003] Westergaard believes that assuming that the dam surface is vertical, the depth of the reservoir water is fixed and extends infinitely upstream, and the seismic load it receives can be simplified to simple harmonic vibration, then the compressibility of the fluid and the fluctuation of the free surface of the fluid can be ignored, and the pressure of the fluid on the solid can be simplified Considering the equivalent mass; Housner ignores the compressibility of the fluid, and obtains the equivalent mass and spring model of the pulse pressure and convective pressure of the fluid per unit thickness on the wall of the rectangular container according to the potential flow theory. The Housner method is suitable for the fluid-solid of the closed container Coupling problems are obviously not suitable for fluid-solid coupling problems like dams. Both the Westergaard method and the Housner method can only calculate the first-order effect of fluid pressure on solids, and cannot consider the influence of solid deformation on fluids;

[0004] The fluid-solid coupling solution method divides the fluid domain and the solid domain into finite element grids, and the finite element solution usually has two forms: displacement-displacement mode and displacement-pressure format ; The advantage of the displacement-displacement model is that the unknowns are unified, and the boundary is easy to handle. The disadvantage is that there are many unknowns to be obtained, and it is easy to generate pseudo-modes; the displacement-pressure model only has one pressure unknown on each node of the fluid domain, and the calculation The efficiency is high, so the finite element analysis based on the displacement-pressure format is often used in the fluid-solid coupling analysis; and there are many finite element methods for solving the fluid-solid coupling problem based on the displacement-pressure format, and the implicit-implicit Newmark method and the implicit - Explicit Newmark method, the disadvantage of these methods is that the calculation step is limited, and algorithm damping will be generated during calculation, which reduces calculation efficiency and calculation accuracy

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