Damping control method based on dam vibration table dynamic model test

Abstract

The invention discloses a damping control method based on a dynamic model test of a dam vibration table, and belongs to the field of anti-seismic tests, and the method comprises the following steps: S1, processing basic boundary conditions: simulating an artificial tangential damping boundary by using viscous damping liquid; s2, constructing the relationship among the shear viscosity of the viscous damping fluid when the viscous damping fluid is subjected to shear deformation, the thickness of the viscous damping fluid and the damping coefficient of the artificial tangential damping boundary; and S3, calculating the thickness of the viscous damping fluid based on the basic medium parameters and the shear viscosity of the viscous damping fluid. According to the damping control method based on the dam vibration table dynamic model test, the viscous damping liquid is used for simulating the manual tangential damping boundary, the dynamic reaction of the dam under the actual working condition can be more accurately reproduced in the test, especially the damping effect under the action of earthquakes or other dynamic loads, and the test accuracy is improved. And the accuracy and practicability of the model test are improved.

Description

Technical Field

[0001] The invention relates to the field of earthquake resistance tests, and in particular to a damping control method based on a dam shaking table dynamic model test. Background Art

[0002] The dynamic interaction between structure and foundation is one of the important factors in the evaluation of seismic response of large structures. In the interaction, the influence of foundation elasticity can be effectively reflected by including a certain range of foundations around the structure in the calculation or test model. On the other hand, seismic waves transmit vibration energy to the structure through the foundation medium, and the vibration energy of the structure is also transmitted to the far field through the foundation medium. This phenomenon of the transmission of structural vibration energy to the far field is called energy radiation in dynamic analysis. Since energy radiation reduces the vibration of the structure, it is similar to the damping effect of the structure, so energy radiation is also called radiation damping effect.

[0003] The existence of radiation damping effect causes the following problems in most analysis and test methods that only consider a limited range: only by effectively simulating the vibration energy radiation on the artificially intercepted limited range foundation boundary, that is, effectively avoiding the vibration energy from being reflected by the artificial boundary, can the dynamic response of the structure be accurately obtained.

[0004] At the same time, under indoor test conditions, the test model can only select a limited range of dam-foundation systems. The simulation of radiation damping effects has not been fully solved. Therefore, the simulation of geological and topographic conditions in dam model tests is limited.

[0005] Moreover, some dynamic model tests are carried out using a rigid foundation, which limits the experimental research to some influencing factors, such as the transverse joints between reservoir water and dam body, and dam body structure. Summary of the invention

[0006] To solve the above problems, the present invention provides a damping control method based on a dam shaking table dynamic model test. By using viscous damping fluid to simulate an artificial tangential damping boundary, the dynamic response of the dam under actual working conditions can be more accurately reproduced in the test, especially the damping effect under earthquake or other dynamic loads, thereby improving the accuracy and practicality of the model test.

[0007] To achieve the above object, the present invention provides a damping control method based on a dam shaking table dynamic model test, comprising the following steps:

[0008] S1. Processing basic boundary conditions: using viscous damping fluid to simulate artificial tangential damping boundary;

[0009] S2, constructing the relationship between the shear viscosity of the viscous damping fluid when it is subjected to shear deformation, the thickness of the viscous damping fluid and the damping coefficient of the artificial tangential damping boundary;

[0010] S3. Calculate the thickness of the viscous damping fluid based on the basic medium parameters and the shear viscosity of the viscous damping fluid.

[0011] Preferably, in step S1, the viscous damping fluid is a polymer silicone rubber, and the shear viscosity η of the polymer silicone rubber is a 7.0×10 3 Pa.S.

[0012] Preferably, step S2 specifically includes the following steps:

[0013] S21. When the viscous damping fluid is subjected to shear deformation, the shear viscosity η is calculated based on the shear stress and shear strain rate. a :

[0014]

[0015] In the formula, τ a is the shear stress, γ a is the shear strain rate;

[0016] The shear strain rate γ a The calculation formula is as follows:

[0017]

[0018] In the formula, is the particle velocity tangential to the boundary, ΔL is the thickness of the viscous damping fluid;

[0019] S22. Based on formula (1) and formula (2), the shear viscosity η of the viscous damping fluid when subjected to shear deformation is constructed: a , thickness ΔL and the damping coefficient c of the artificial tangential damping boundary t The relationship between:

[0020]

[0021] Where ρ is the density of the base medium and v is the shear wave velocity of the base medium.

[0022] Preferably, in step S22, the displacement continuity condition is used to derive that the velocity on the interface is equal, and the stress continuity condition is used to obtain that the force in the semi-infinite space is proportional to the velocity on the interface, and the proportionality coefficient between the force in the infinite space and the velocity on the interface is regarded as equivalent proportional damping, and the equivalent proportional damping is regarded as the damping coefficient c t , and get c t =ρv.

[0023] Preferably, in step S3, the dynamic elastic modulus of the base medium is 128.0 MPa, the Poisson's ratio is 0.35, and the shear wave velocity of the base medium based on elastic mechanics is 140.5 m / s;

[0024] The shear wave velocity is 140.5 m / s and the shear viscosity η a 7.0×10 3 Substituting Pa·S into formula (3), the thickness of the viscous damping fluid ΔL is calculated to be 20.8 mm.

[0025] Preferably, step S3 further includes step S4, verifying:

[0026] Based on the calculation results of step S3, a distributed artificial tangential damping boundary is applied to the basic medium boundary of the vibration table model, and a damping simulation test is performed. The test is compared with the simulation test in which both normal damping and tangential damping are set. The effectiveness of step S3 is verified based on the derived time history curve.

[0027] Preferably, in step S4, one end of the artificial tangential damper is connected to the boundary of the base medium, and the other end is set as a free end.

[0028] The present invention has the following beneficial effects:

[0029] By using viscous damping fluid to simulate the artificial tangential damping boundary, the dynamic response of the dam under actual working conditions can be reproduced more accurately in the test, especially the damping effect under earthquake or other dynamic loads, which improves the accuracy and practicality of the model test.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a flow chart of a damping control method based on a dam shaking table dynamic model test of the present invention;

[0032] Figure 2 It is an artificial tangential damping arrangement diagram of a damping control method based on a dam shaking table dynamic model test of the present invention;

[0033] Figure 3 A time history curve diagram of the dynamic arch stress at the left end of the upstream top arch according to an embodiment of the present invention;

[0034] Figure 4 This is a time history curve diagram of the dynamic beam stress at the bottom of the downstream crown beam according to an embodiment of the present invention.

[0035] Among them, 1. Artificial tangential damping. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0037] It should be noted that the terms "include", "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or devices.

[0038] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0039] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0040] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] like Figure 1 and Figure 2 As shown, a damping control method based on a dam shaking table dynamic model test includes the following steps:

[0042] S1. Processing basic boundary conditions: using viscous damping fluid to simulate artificial tangential damping 1 boundary;

[0043] In step S1, the viscous damping fluid is a polymer silicone rubber, and the shear viscosity η of the polymer silicone rubber is a 7.0×10 3 Pa·S, polymer silicone rubber has the advantages of very good chemical and physical stability at room temperature, liquid viscosity is related to molecular weight and easy to control, the product is safe, non-toxic and easy to use.

[0044] S2, constructing the relationship between the shear viscosity of the viscous damping fluid when it is subjected to shear deformation, the thickness of the viscous damping fluid and the damping coefficient of the artificial tangential damping 1 boundary;

[0045] Step S2 specifically includes the following steps:

[0046] S21. When the viscous damping fluid is subjected to shear deformation, the shear viscosity η is calculated based on the shear stress and shear strain rate. a :

[0047]

[0048] In the formula, τ a is the shear stress, γ a is the shear strain rate;

[0049] The shear strain rate γ a The calculation formula is as follows:

[0050]

[0051] In the formula, is the particle velocity tangential to the boundary, ΔL is the thickness of the viscous damping fluid;

[0052] S22. Based on formula (1) and formula (2), the shear viscosity η of the viscous damping fluid when subjected to shear deformation is constructed: a , thickness ΔL and the damping coefficient c of the artificial tangential damping 1 boundary t The relationship between:

[0053]

[0054] Where ρ is the density of the base medium and v is the shear wave velocity of the base medium.

[0055] In step S22, the displacement continuity condition derives that the velocity on the interface is equal, and the stress continuity condition derives that the force in the semi-infinite space is proportional to the velocity on the interface, and the proportionality coefficient between the force in the infinite space and the velocity on the interface is regarded as the equivalent proportional damping, and the equivalent proportional damping is regarded as the damping coefficient c t , and get c t =ρv.

[0056] S3. Calculate the thickness of the viscous damping fluid based on the basic medium parameters and the shear viscosity of the viscous damping fluid.

[0057] In step S3, the dynamic elastic modulus of the base medium is 128.0 MPa, the Poisson's ratio is 0.35, and the shear wave velocity of the base medium is 140.5 m / s based on elastic mechanics. a 7.0×10 3 Substituting Pa·S into formula (3), the thickness of the viscous damping fluid ΔL is calculated to be 20.8 mm.

[0058] Step S3 is followed by step S4, verification:

[0059] Based on the calculation results of step S3, a distributed artificial tangential damping 1 boundary is applied to the basic medium boundary of the shaking table model, and a damping simulation test is performed. The test is compared with the simulation test in which both normal damping and tangential damping are set. The effectiveness of step S3 is verified based on the derived time history curve.

[0060] In step S4, one end of the artificial tangential damper is connected to the boundary of the base medium, and the other end is set as a free end.

[0061] Example

[0062] In this embodiment, the dynamic arch stress time history curve of the left end of the upstream top arch and the dynamic beam stress time history curve of the bottom of the downstream arch crown beam are used as examples for explanation. In this embodiment, the damping boundary is supported by a steel frame fixed to the vibration table (the outer surface of the foundation is also waterproofed to prevent the leakage of the damping fluid). Therefore, the shear deformation borne by the viscous damping fluid is the relative movement of the artificial boundary of the model foundation to the base.

[0063] Table 1 Displacement and extreme dynamic stress values ​​of some positions of the dam body (calculated by Xiluodu model)

[0064]

[0065]

[0066] like Figure 3 and Figure 4 As shown in the figure, the above comparative calculation results show that boundary damping has a significant energy dissipation effect, and although the structural displacement and stress response of the condition of only taking into account the tangential damping is slightly different from that of taking into account the tangential normal damping at the same time, it is significantly improved compared with the condition of no boundary damping, and the accuracy range of the results is still acceptable in engineering applications. Therefore, the scheme of applying only tangential motion damping as described in the present invention can consume most of the energy transmitted from the boundary, thereby proving the effectiveness of the present invention and greatly reducing the difficulty of model making while maintaining sufficient accuracy.

[0067] Therefore, the present invention adopts the above-mentioned damping control method based on the dam shaking table dynamic model test. By using viscous damping fluid to simulate the artificial tangential damping boundary, it can more accurately reproduce the dynamic response of the dam under actual working conditions in the test, especially the damping effect under earthquake or other dynamic loads, thereby improving the accuracy and practicality of the model test.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A damping control method based on a dam shaking table dynamic model test, characterized in that: The following steps are involved: S1. Processing basic boundary conditions: using viscous damping fluid to simulate artificial tangential damping boundary; S2, constructing the relationship between the shear viscosity of the viscous damping fluid when it is subjected to shear deformation, the thickness of the viscous damping fluid and the damping coefficient of the artificial tangential damping boundary; S3. Calculate the thickness of the viscous damping fluid based on the basic medium parameters and the shear viscosity of the viscous damping fluid.

2. The damping control method based on the dam shaking table dynamic model test according to claim 1 is characterized in that: In step S1, the viscous damping fluid is a polymer silicone rubber, and the shear viscosity η of the polymer silicone rubber is a 7.0×10 3 Pa.S.

3. The damping control method based on the dam shaking table dynamic model test according to claim 2 is characterized in that: Step S2 specifically includes the following steps: S21. When the viscous damping fluid is subjected to shear deformation, the shear viscosity η is calculated based on the shear stress and shear strain rate. a : In the formula, τ a is the shear stress, γ a is the shear strain rate; The shear strain rate γ a The calculation formula is as follows: In the formula, is the particle velocity tangential to the boundary, ΔL is the thickness of the viscous damping fluid; S22. Based on formula (1) and formula (2), the shear viscosity η of the viscous damping fluid when subjected to shear deformation is constructed: a , thickness ΔL and the damping coefficient c of the artificial tangential damping boundary t The relationship between: Where ρ is the density of the base medium and v is the shear wave velocity of the base medium.

4. The damping control method based on the dam shaking table dynamic model test according to claim 3 is characterized in that: In step S22, the displacement continuity condition derives that the velocity on the interface is equal, and the stress continuity condition derives that the force in the semi-infinite space is proportional to the velocity on the interface, and the proportionality coefficient between the force in the infinite space and the velocity on the interface is regarded as the equivalent proportional damping, and the equivalent proportional damping is regarded as the damping coefficient c t , and get c t =ρv.

5. The damping control method based on the dam shaking table dynamic model test according to claim 4 is characterized in that: In step S3, the dynamic elastic modulus of the base medium is 128.0 MPa, the Poisson's ratio is 0.35, and the shear wave velocity of the base medium based on elastic mechanics is 140.5 m / s; The shear wave velocity is 140.5 m / s and the shear viscosity η a 7.0×10 3 Substituting Pa·S into formula (3), the thickness of the viscous damping fluid ΔL is calculated to be 20.8 mm.

6. The damping control method based on the dam shaking table dynamic model test according to claim 5 is characterized in that: Step S3 is followed by step S4, verification: Based on the calculation results of step S3, a distributed artificial tangential damping boundary is applied to the basic medium boundary of the vibration table model, and a damping simulation test is performed. The test is compared with the simulation test in which both normal damping and tangential damping are set. The effectiveness of step S3 is verified based on the derived time history curve.

7. The damping control method based on the dam shaking table dynamic model test according to claim 6 is characterized in that: In step S4, one end of the artificial tangential damper is connected to the boundary of the base medium, and the other end is set as a free end.

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