A three-dimensional isolation bearing with variable stiffness and vertical limit friction

Abstract

The present invention discloses a variable-stiffness three-dimensional isolation bearing with vertical limit friction, which comprises a thick-layer rubber bearing, a lead-core rubber bearing and a limit decoupling system. The thick-layer rubber bearing, the limit friction device and the external lateral resistance groove form a vertical isolation system, and its vertical deformation mainly occurs in the thick-layer rubber bearing; the lead-core rubber bearing, the upper and lower connecting plates and the external lateral resistance groove form a horizontal isolation system, and its horizontal deformation mainly occurs in the lead-core rubber bearing. The limit decoupling system includes a limit friction device and an external lateral resistance groove. The limit friction device consists of a middle connecting plate, an upper connecting plate, a lower connecting plate, a pre-tightening disc spring and a friction strip. For the variable-stiffness three-dimensional isolation bearing with vertical limit friction of the present invention, the horizontal mechanical properties are similar to those of a conventional lead-core rubber bearing, while there is a second-order stiffness vertically, achieving low stiffness at small displacements and high stiffness at large displacements, and with obvious energy dissipation, enabling the bearing to fully exert its performance under different seismic action stages.

Description

Technical Field

[0001] The present invention relates to the technical field of seismic isolation, and particularly to a variable-stiffness three-dimensional seismic isolation bearing with vertical limit friction. Background Art

[0002] The seismic isolation technology sets a flexible seismic isolation layer to extend the period of the superstructure, which will greatly reduce the seismic response of the superstructure and ensure that the superstructure can still be in the elastic state during a major earthquake or remain in the initial state of the elastoplastic deformation state. At present, the research, development and application of horizontal seismic isolation devices have been relatively mature, but their seismic isolation effect on vertical ground motion is poor, and even the vertical seismic response may be amplified. Compared with the mature horizontal seismic isolation system, the research on three-dimensional seismic isolation needs to be further developed.

[0003] The main problems existing in the three-dimensional seismic isolation bearing are as follows: First, it is necessary to reduce the vertical stiffness of the three-dimensional seismic isolation bearing and ensure the vertical bearing capacity of the three-dimensional seismic isolation bearing; second, the low vertical stiffness of the three-dimensional seismic isolation bearing results in a relatively high height of the three-dimensional seismic isolation bearing, and the vertical displacement of the three-dimensional seismic isolation bearing is relatively large under seismic action; third, the three-dimensional seismic isolation bearing lacks vertical damping, and dampers need to be additionally added. Therefore, it is necessary to study a three-dimensional seismic isolation bearing with low vertical stiffness, certain energy dissipation capacity and the ability to limit excessive vertical displacement of the three-dimensional seismic isolation bearing. Summary of the Invention

[0004] The purpose of the present invention is to provide a variable-stiffness three-dimensional seismic isolation bearing with vertical limit friction, which can achieve high load-bearing, low stiffness and damping energy dissipation capacity of the three-dimensional seismic isolation bearing, and limit excessive vertical displacement.

[0005] To achieve the above object, the present invention adopts the following technical solutions.

[0006] A variable-stiffness three-dimensional seismic isolation bearing with vertical limit friction, characterized in that it includes a vertical seismic isolation system at the upper part, a horizontal seismic isolation system at the lower part and a decoupling system in the middle;

[0007] The vertical seismic isolation system includes a thick-layer rubber bearing (1) at the upper part, a limit friction device in the middle and an external lateral groove (8); the horizontal seismic isolation system includes a lead core rubber bearing (2) at the lower part, an upper connecting plate (4), a lower connecting plate (5) and an external lateral groove (8); the decoupling system includes a limit friction device and an external lateral groove (8);

[0008] The described limit friction device includes: a middle connecting plate (3), an upper connecting plate (4), a lower connecting plate (5), a pre-tightening disc spring (6), and a friction strip (7). The middle connecting plate (3) transmits the vertical axial force; the height of the friction strip (7) is less than that of the middle connecting plate (3), so there is a reserved clearance between it and the upper connecting plate (4) and the lower connecting plate (5); the middle connecting plate presses the friction strip against the external lateral resistance groove (8) through a number of pre-tightening disc springs (6); the friction strip (7) can move up and down with the external lateral resistance groove within the reserved clearance range and maintain balance through the vertical static friction force. The upper connecting plate (4) and the lower connecting plate (5) are the upper and lower boundaries for the movement of the friction strip.

[0009] Further, for the variable stiffness three-dimensional seismic isolation bearing with vertical limit friction, it is characterized in that: between the friction strip (7) and the external lateral resistance groove (8), a friction contact surface of stainless steel fiber material against steel or 42CrMo is adopted, and the magnitude of the friction coefficient can be adjusted. The pre-tightening disc spring (6) provides the pre-pressure between the contact surfaces.

[0010] Further, the reserved clearance between the friction strip (7) and the upper connecting plate (4) and the lower connecting plate (5) is determined according to the engineering requirements, and the range is between 1 mm and 10 mm.

[0011] Further, for the variable stiffness three-dimensional seismic isolation bearing with vertical limit friction, it is characterized in that: the sides of the upper connecting plate (4) and the lower connecting plate (5) are treated with a smooth surface and do not generate friction with the external lateral resistance groove.

[0012] Further, for the variable stiffness three-dimensional seismic isolation bearing with vertical limit friction, it is characterized in that: the middle connecting plate (3), the upper connecting plate (4), the lower connecting plate (5), the thick-layer rubber bearing (1), the lead-rubber bearing (2), and the external lateral resistance groove are integrally formed by welding.

[0013] Further, for the variable stiffness three-dimensional seismic isolation bearing with vertical limit friction, it is characterized in that: the first shape factor of the lead-rubber bearing (2) is above 25, and the first shape factor of the thick-layer rubber bearing (1) is below 10; the vertical stiffness of the lead-rubber bearing (2) is more than 10 times that of the thick-layer rubber bearing (1).

[0014] The variable stiffness three-dimensional seismic isolation bearing with vertical limit friction adopts a separated design method. By adjusting the ratio of the vertical stiffness of the thick-layer rubber bearing (1) to the lead-rubber bearing (2), the vertical deformation mainly occurs in the upper thick-layer rubber bearing (1); the external lateral resistance groove (8) is used to limit the relative horizontal movement between the thick-layer rubber bearing (1) and the limit friction device, so that the horizontal deformation occurs in the lower lead-rubber bearing (2). Finally, the decoupling of the deformation in the horizontal and vertical directions is realized.

[0015] Under the vertical load of the vertical limit friction variable stiffness three-dimensional isolation bearing, when a small displacement occurs, under the action of static friction, the friction strip (7) and the external lateral resistance groove (8) move together without relative displacement, and the limit friction device does not play a role. At this time, the vertical isolation performance of the vertical limit friction variable stiffness three-dimensional isolation bearing is determined by the thick rubber bearing (1); when the vertical limit friction variable stiffness three-dimensional isolation bearing has a large displacement, the friction strip (7) contacts the upper connecting plate (4) and the lower connecting plate (5), and a dislocation slip occurs between the friction strip (7) and the external lateral resistance groove (8), resulting in relative displacement, and the static friction is converted into dynamic friction.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1) The vertical limit friction variable stiffness three-dimensional isolation bearing of the present invention has horizontal mechanical properties similar to those of a conventional lead-rubber bearing, while having a second-order stiffness in the vertical direction, improving the deficiency of the traditional isolation bearing having only a first-order stiffness in the vertical direction, achieving low stiffness at small displacements and high stiffness at large displacements, and having obvious energy dissipation, so that the vertical limit friction variable stiffness three-dimensional isolation bearing can give full play to its performance in different earthquake action stages;

[0018] 2) The vertical limit friction variable stiffness three-dimensional isolation bearing of the present invention has a simpler structure, lower cost, and is more convenient for processing and manufacturing compared with the same type of three-dimensional isolation bearing;

[0019] 3) The components of the vertical limit friction variable stiffness three-dimensional isolation bearing of the present invention adopt rubber isolation bearings, steel strips, etc. that are widely used in practice and have mature technologies. The components are simple and reliable in performance, thus ensuring the stability of the overall mechanical properties of the vertical limit friction variable stiffness three-dimensional isolation bearing;

[0020] 4) The vertical limit friction variable stiffness three-dimensional isolation bearing of the present invention can adjust the stiffness of the vertical limit friction variable stiffness three-dimensional isolation bearing under vertical deformation by changing the friction surface characteristics, thereby restricting the vertical displacement; the energy dissipation capacity of the vertical limit friction variable stiffness three-dimensional isolation bearing can be optimized by changing the reserved dead zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the three-dimensional isolation bearing of the present invention: (a) Top view (b) Front view;

[0022] Figure 2 Schematic diagram of the A-A cross-sectional elevation of the three-dimensional isolation bearing of the present invention;

[0023] Figure 3 Schematic diagram of the B-B cross-sectional plan of the three-dimensional isolation bearing of the present invention;

[0024] Figure 4 Schematic diagram of the reserved dead zone of the three-dimensional isolation bearing of the present invention;

[0025] Figure 5 Schematic diagram of the vertical compression deformation of the three-dimensional seismic isolation bearing of the present invention;

[0026] Figure 6 Schematic diagram of the compression-shear deformation of the three-dimensional seismic isolation bearing of the present invention;

[0027] Figure 7 Schematic diagram of the horizontal force-displacement constitutive model of the three-dimensional seismic isolation bearing of the present invention under reciprocating loads;

[0028] Figure 8 Schematic diagram of the vertical force-displacement constitutive model of the three-dimensional seismic isolation bearing of the present invention under reciprocating loads;

[0029] Reference numerals: 1 - thick-layer rubber bearing, 2 - lead-core rubber bearing, 3 - middle connecting plate, 4 - upper connecting plate, 5 - lower connecting plate, 6 - pre-tightening disc spring, 7 - friction strip, 8 - external lateral resistance groove. Detailed implementation manners

[0030] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments described by referring to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0031] As Figures 1-3 , a variable-stiffness three-dimensional seismic isolation bearing with vertical limit friction includes an upper vertical seismic isolation system, a lower horizontal seismic isolation system, and an intermediate decoupling system;

[0032] The vertical seismic isolation system includes a thick-layer rubber bearing (1) at the upper part, a limit friction device in the middle, and an external lateral resistance groove (8);

[0033] The horizontal seismic isolation system includes a lead-core rubber bearing (2) at the lower part, an upper connecting plate (4), a lower connecting plate (5), and an external lateral resistance groove (8);

[0034] The decoupling system includes a limit friction device and an external lateral resistance groove (8);

[0035] The limit friction device includes: a middle connecting plate (3), an upper connecting plate (4), a lower connecting plate (5), a pre-tightening disc spring (6), and a friction strip (7). The middle connecting plate (3), the upper connecting plate (4), the lower connecting plate (5), the thick-layer rubber bearing (1), the lead-core rubber bearing (2), and the external lateral resistance groove (8) are integrally formed by welding.

[0036] Referring to Figure 3, a friction strip (7) and an external anti - lateral groove (8) adopt a friction contact surface of stainless steel fiber material for steel or 42CrMo, the magnitude of the friction coefficient can be adjusted, and a pre - tightening disc spring (6) provides a pre - pressure between the contact surfaces. The sides of the upper connecting plate (4) and the lower connecting plate (5) are treated with smooth surfaces and do not generate frictional force with the external anti - lateral groove (8).

[0037] Refer to Figure 4 , the middle connecting plate (3) transmits the vertical axial force. The friction strip (7) is slightly smaller in height than the middle connecting plate (3). Therefore, there is a certain reserved stroke between the friction strip (7) and the upper connecting plate (4) and the lower connecting plate (5). The middle connecting plate presses the friction strip against the external anti - lateral groove (8) through the pre - tightening disc spring (6). It can move up and down with the external anti - lateral groove within the reserved stroke range and maintain balance through the vertical static friction force. The upper connecting plate (4) and the lower connecting plate (5) are the upper and lower boundaries of the friction strip. The reserved stroke between the friction strip (7) and the upper connecting plate (4) and the lower connecting plate (5) is determined according to engineering requirements and ranges from 1 mm to 10 mm.

[0038] Such as Figures 5-6 , the variable - stiffness three - dimensional isolation bearing with vertical limit friction of the present invention adopts a separated design method. By adjusting the vertical stiffness ratio of the thick - layer rubber bearing (1) and the lead - core rubber bearing (2), the vertical deformation mainly occurs in the upper thick - layer rubber bearing (1);

[0039] Such as Figure 6 , an external anti - lateral groove (8) is used to limit the relative horizontal movement between the thick - layer rubber bearing (1) and the limit friction device, so that the horizontal deformation all occurs in the lower lead - core rubber bearing (2);

[0040] Finally, the decoupling of the deformations in the horizontal and vertical directions is realized.

[0041] Further explanation of the principle:

[0042] Such as Figure 7 is a schematic diagram of the horizontal force - displacement constitutive model of the variable - stiffness three - dimensional isolation bearing with vertical limit friction of the present invention under cyclic loading. Since the external anti - lateral groove (8) is in close contact with the upper connecting plate (4) and the lower connecting plate (5), no relative horizontal displacement will occur between the top of the external anti - lateral groove (8) and the upper connecting plate (4) and the lower connecting plate (5), thus restricting the horizontal deformation of the thick - layer rubber bearing (1) and the limit friction device. Therefore, the horizontal deformation capacity of the variable - stiffness three - dimensional isolation bearing with vertical limit friction of the present invention is provided by its component lead - core rubber bearing (2), and the overall horizontal force - displacement constitutive model is consistent with its component lead - core rubber bearing (2). Assume that the horizontal shear stiffness of the lead core in the lead - core rubber bearing (2) is K L , and the total horizontal shear stiffness of the rubber layer is K R, then the first-order stiffness of the horizontal force-displacement constitutive model of the present invention: K h1 = K L + K R ; The second-order stiffness: K h2 = K R .

[0043] By changing the characteristics of the friction surface, the stiffness of the bearing under vertical deformation can be adjusted, thereby restricting the vertical displacement; by changing the reserved dead band, the energy dissipation capacity of the bearing can be optimized and adjusted.

[0044] Such as Figure 8 is a schematic diagram of the vertical force-displacement constitutive model of the bearing of the present invention under reciprocating loads. The vertical force-displacement constitutive model of the overall bearing of the present invention is mainly determined by the thick-layer rubber bearing (1) and the limit friction device. Such as Figure 8 , the reserved dead band between the friction strip (7) and the upper connecting plate (4) and the lower connecting plate (5) is marked as U 1, and the overall vertical deformation of the bearing is marked as U 2. When the bearing undergoes small displacements (vertical displacement ≤ U 1), under the action of static friction, the friction strip (7) and the external lateral groove (8) move together without relative displacement, and the limit friction device does not play a role. At this time, the vertical seismic isolation performance of the bearing is determined by the thick-layer rubber bearing (1); when the seismic isolation bearing undergoes large displacements ( U 1 < vertical displacement ≤ U 2), the friction strip (7) contacts the upper connecting plate (4) or the lower connecting plate (5), and frictional sliding occurs between the friction strip (7) and the external lateral groove (8), and the static friction is transformed into dynamic friction. Therefore, the vertical deformation of the seismic isolation bearing has a second-order stiffness and has a certain friction energy dissipation capacity. The vertical stiffness of the thick-layer rubber bearing (1) is k 1, and the vertical stiffness of the lead-core rubber bearing (2) is k 2, and the design control k 1 ≤ 0.1 k 2; A 1, A 2 are the effective cross-sectional areas of the bearings (1) and (2) respectively; E c1 , E c2 are the compression elastic moduli of the bearings (1) and (2) respectively; t R1 , t R2 are the total rubber thicknesses of the bearings (1) and (2) respectively; k f , , F N are respectively the friction stiffness, friction coefficient, and pre-pressure of the contact surface between the friction strip (7) and the external anti-lateral groove (8); U f is the vertical displacement value corresponding to when the frictional force increases to . Thus, in the vertical force-displacement constitutive model of the present invention, the first-order stiffness and the second-order stiffness can be obtained through the following formulas:

[0045] ,

[0046]

[0047]

[0048]

[0049] In this embodiment, the first shape factor of the lead rubber bearing (2) is 25 or more, and the first shape factor of the thick rubber bearing (1) is 10 or less.

[0050] In summary, the horizontal mechanical properties of the variable-stiffness three-dimensional isolation bearing with vertical limit friction of the present invention are similar to those of a conventional lead rubber bearing, while there is a second-order stiffness vertically, improving the deficiency of the traditional isolation bearing with only a first-order stiffness vertically, achieving low stiffness at small displacements and high stiffness at large displacements, and having obvious energy dissipation, enabling the variable-stiffness three-dimensional isolation bearing with vertical limit friction to fully exert its performance under different seismic action stages; compared with the same type of three-dimensional isolation bearing, the vertical stiffness and energy dissipation capacity of the variable-stiffness three-dimensional isolation bearing with vertical limit friction can be flexibly adjusted, with strong self-adaptive ability under seismic action, stable isolation performance, simple structure, low cost, and convenient processing and manufacturing.

[0051] The above description is only a description of the preferred embodiments of the present application, and is not any limitation on the scope of the present application. Any change or modification made by any person skilled in the art according to the technical content disclosed above should be regarded as an equivalent effective embodiment, and all belong to the scope protected by the technical solution of the present application.

Claims

1. A three-dimensional isolation bearing with variable stiffness of vertical limit friction, characterized in that, It includes a vertical isolation system, a horizontal isolation system, a limit friction device, and an external lateral resistance groove (8). The vertical isolation system includes a thick-layer rubber bearing (1) located at the upper part. The horizontal isolation system includes a lead rubber bearing (2) located at the lower part. The limit friction device includes a middle connecting plate (3), an upper connecting plate (4), a lower connecting plate (5), a pre-tightening disc spring (6), and a friction strip (7). Wherein: The external lateral resistance groove (8) is placed outside the whole of the thick-layer rubber bearing (1), the lead rubber bearing (2), and the limit friction device. The middle connecting plate (3), the upper connecting plate (4), the lower connecting plate (5), the thick-layer rubber bearing (1), the lead rubber bearing (2), and the external lateral resistance groove (8) are formed into a whole by welding. The middle connecting plate (3) transmits the vertical axial force; the height of the friction strip (7) is less than that of the middle connecting plate (3), so there is a reserved stroke between the friction strip (7) and the upper connecting plate (4) and the lower connecting plate (5); the middle connecting plate (3) presses the friction strip (7) on the external lateral resistance groove (8) through a plurality of pre-tightening disc springs (6); the friction strip (7) can move up and down with the external lateral resistance groove (8) within the reserved stroke range and maintain balance through the vertical static friction force, and the upper connecting plate (4) and the lower connecting plate (5) are the upper and lower boundaries for the movement of the friction strip (7). The thick-layer rubber bearing (1) and the lead rubber bearing (2) adopt a separated design. By adjusting the vertical stiffness ratio of the thick-layer rubber bearing (1) and the lead rubber bearing (2), the vertical deformation mainly occurs in the upper thick-layer rubber bearing (1); the external lateral resistance groove (8) is used to limit the relative horizontal movement between the thick-layer rubber bearing (1) and the limit friction device, so that the horizontal deformation all occurs in the lower lead rubber bearing (2); finally, the deformation decoupling in the horizontal and vertical directions is realized.

2. The variable-stiffness three-dimensional isolation bearing with vertical limit friction according to claim 1, characterized in that The friction contact surface between the friction strip (7) and the external lateral resistance groove (8) adopts a stainless steel fiber material for the friction between steel or 42CrMo, and the size of the friction coefficient can be adjusted, and the pre-tightening disc spring (6) provides the pre-pressure between the contact surfaces.

3. The three-dimensional isolation bearing with variable stiffness of vertical limit friction according to claim 1, characterized in that, The reserved stroke between the friction strip (7) and the upper connecting plate (4) and the lower connecting plate (5) is determined according to the engineering requirements, and the range is between 1 mm and 10 mm.

4. The three-dimensional isolation bearing with variable stiffness of vertical limit friction according to claim 1, wherein The sides of the upper connecting plate (4) and the lower connecting plate (5) are treated with a smooth surface and do not generate friction with the external lateral resistance groove (8).

5. The three-dimensional isolation bearing with variable stiffness of vertical limit friction according to claim 1, characterized in that, The first shape factor of the lead rubber bearing (2) is more than 25, and the first shape factor of the thick-layer rubber bearing (1) is less than 10; the vertical stiffness of the lead rubber bearing (2) is more than 10 times that of the thick-layer rubber bearing (1).

6. The variable-stiffness three-dimensional seismic isolation bearing with vertical limit friction according to claim 1, characterized in that, Under the vertical load of the lead-rubber bearing, when small displacements occur, under the action of static friction, the friction strip (7) and the external lateral resistance groove (8) move together without relative displacement, and the limit friction device does not play a role. At this time, the vertical seismic isolation performance of the lead-rubber bearing is determined by the thick-layer rubber bearing (1); when large displacements occur in the seismic isolation bearing, the friction strip (7) contacts the upper connecting plate (4) and the lower connecting plate (5), and misalignment sliding occurs between the friction strip (7) and the external lateral resistance groove (8), resulting in relative displacement, and static friction is transformed into dynamic friction.

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