Steel elasto-plastic damper for bridge

Abstract

To provide a steel elasto-plastic damper for a bridge having uniform bending stress over the whole length and capable of efficiently absorbing kinetic energy of an upper structure.SOLUTION: A steel plate damper 10 installed in the vertical direction between the upper and lower structures of a bridge comprises a mounting plate 11 fixed to the lower structure and having two opposing side edges 11a, 11a inclined so that a distance between the side edges widens toward a lower side, and a pair of damper bodies 12, 12 each having an isosceles triangular planar shape with a base 12a continuously provided on the two side edges 11a, 11a of the mounting plate 11, wherein the damper bodies 12, 12 are arranged such that a horizontal load caused by displacement of the upper structure acts on a surface of an apex portion 12b in a normal direction thereof.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a steel elasto-plastic damper for bridges. [Background technology]

[0002] Conventionally, a shear panel type seismic stopper has been known as a steel plate damper that absorbs and attenuates the kinetic energy caused by vibration of the superstructure during an earthquake (see, for example, Patent Document 1). This seismic stopper absorbs the kinetic energy of the superstructure by shearing a low-yield-point steel plate.

[0003] Although this conventional damper exhibits excellent energy absorption capabilities, the stress distribution is complex, resulting in stress concentration, and the amount of displacement cannot be expected to be large. In addition, it cannot be expected to withstand many repeated loads. Furthermore, in order to make this damper work using a cross beam installed between girders, two cross beams are required to sandwich the damper, which inevitably increases the installation cost. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2007-191912 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made based on the above technical background and has the following objectives. The object of this invention is to provide a steel elasto-plastic damper for bridges that uses steel plates shaped to function as beams of uniform strength for the damper body, thereby ensuring that bending stress is uniform throughout the entire length and enabling efficient absorption of the kinetic energy of the superstructure. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention employs the following means. That is, this invention is a damper made of steel plates that is installed vertically between the upper and lower structures of a bridge, a mounting plate fixed to the lower structure, the mounting plate having two opposing sides that are inclined such that the distance between the sides increases toward the lower portion; a pair of damper bodies each having a planar shape of an isosceles triangle whose base is connected to the two side edges of the mounting plate; The damper body is a steel elastic-plastic damper for bridges, characterized in that it is arranged so that a horizontal load caused by displacement of the superstructure acts on the surface of the apex corner of the damper body in the normal direction thereof.

[0007] The damper body is not limited to being provided in pairs on the mounting plate, but may be provided as a single body, in which case the present invention is specified as follows. This invention is a damper made of steel plates that is installed vertically between the upper and lower structures of a bridge, a mounting plate secured to the substructure; a damper body having a planar shape of an isosceles triangle with its base connected to one side of the mounting plate; The damper body is a steel elastic-plastic damper for bridges, characterized in that the apex angle side of the bisector of the apex angle faces diagonally upward, and is positioned so that the horizontal load caused by the displacement of the superstructure acts on the surface of the apex angle of the damper body in the direction normal to the surface.

[0008] More specifically, the apex corner is disposed between a load bearing part provided on the superstructure and having two load bearing surfaces facing both sides of the apex corner. The apex corner of the damper body is provided with a load receiving part having a cylindrical surface that abuts on the load bearing surfaces of the load bearing part. [Effects of the Invention]

[0009] According to this invention, by using a steel plate shaped to function as a beam of uniform strength for the damper body, the bending stress is uniform over the entire length, and the kinetic energy of the superstructure can be efficiently absorbed. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a front view showing an embodiment of the present invention. [Figure 2] FIG. 2 is a view taken along the line AA in FIG. [Figure 3] FIG. 2 is a cross-sectional view in the bridge axis direction showing the state in which the embodiment shown in FIG. 1 is installed between the upper and lower structures. [Figure 4] This is a cross-sectional view perpendicular to the bridge axis showing the same installation state. [Figure 5] 1 is a diagram showing the distribution of bending stress etc. when a bending load F is applied to the free end of a cantilever beam. [Figure 6] 1 is a graph showing load-displacement curves for a rectangular beam and a beam of uniform strength. [Figure 7] FIG. 10 is a diagram showing torsion occurring in a cross beam, which is the superstructure. [Figure 8] FIG. 10 is a front view showing another embodiment. [Figure 9] This is a view showing the same embodiment attached to the substructure, viewed in the bridge axis direction. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a front view showing an embodiment of the present invention. A damper 10 is installed vertically between the upper and lower structures of a bridge and is made of a steel plate having a predetermined thickness. The damper 10 comprises a central mounting plate 11 and a pair of damper bodies 12, 12 connected to both sides of the central mounting plate.

[0012] The mounting plate 11 shown has a planar shape resembling an isosceles triangle with the tips of the apex and base corners of the triangle cut off, but this shape is merely an example. The mounting plate 11 has two opposing side edges 11a, 11a that slope so that the distance between them widens toward the bottom. The damper bodies 12, 12 have a planar shape of an isosceles triangle, and are connected so that their base edges 12a, 12a coincide with (overlap) the two opposing side edges 11a, 11a of the mounting plate 11.

[0013] When manufacturing the damper 10, an integrated unit including the mounting plate 11 and the damper bodies 12, 12 may be machined from steel, or the mounting plate 11 and the damper bodies 12, 12 may be machined from steel as separate bodies, and the damper bodies 12, 12 may be fixed to the mounting plate 11 by welding or the like.

[0014] The chain line indicating the boundary between the mounting plate 11 and the damper bodies 12, 12 is merely an imaginary line indicating the boundary for the sake of convenience, and is not an actual line.

[0015] Since the mounting plate 11 has a shape similar to an isosceles triangle, with the side edges 11a, 11a sloping so that the distance between them widens toward the bottom, when the damper bodies 12, 12 are connected to the mounting plate 11 so that their base edges 12a coincide with the side edges 11a, 11a of the mounting plate 11, the bisector H of the apex angle of the damper bodies 12, 12 has the apex angle pointing diagonally upward. In other words, the bisector H of the apex angle of a pair of damper bodies 12, 12 forms an inverted V shape.

[0016] A knob-shaped load receiving portion 13 is provided at the apex corner 12b of the damper main body 12, 12. The load receiving portion 13 is fixed by welding or the like with the apex corner 12b of the damper main body 12 embedded therein.

[0017] As will be described later, the damper body 12 is positioned so that the load caused by the displacement of the upper structure acts in the normal direction on the surface of the apex corner 12b, and the load of the upper structure is transmitted to the damper body 12 via this load receiving portion 13. Both surfaces 13a, 13a of the load receiving portion 13, on which the load of the upper structure acts, are formed into cylindrical surfaces, as shown enlarged in Figure 2.

[0018] As shown in Figures 3 and 4, the damper 10 is installed, for example, between a cross beam (superstructure) 15 installed between two adjacent I-girders of a bridge and a substructure 16 such as a pier or abutment. Figure 3 is a cross section in the bridge axis direction, and Figure 4 is a cross section perpendicular to the bridge axis. In this embodiment, the cross beam 15 is made of an H-shaped steel having a pair of flanges 15a, 15a and a web 15b between the flanges.

[0019] A mounting portion 17 of the damper 10 is installed on the lower structure 16. The mounting portion 17 includes a base plate 19 fixed to the lower structure 16 via anchor bolts 18, and a pair of clamping plates 20, 20 fixed vertically on the base plate 19.

[0020] The clamping plates 20, 20 are arranged so that their faces face the bridge axis direction and have opposing inner surfaces spaced apart by a distance approximately equal to the thickness of the damper 10. Reinforcing ribs 21 are provided between the outer surfaces of the clamping plates 20, 20 and the base plate 19.

[0021] The clamping plates 20, 20 are formed in approximately the same shape as the mounting plate 11 of the damper 10. The mounting plate 11 is placed between the clamping plates 20, 20. The mounting plate 11 is then clamped between the clamping plates 20, 20 by fastening bolts and nuts 22. A plurality of bolt holes 14 provided on both side edges of the mounting plate 11 are holes for passing the bolts of the bolts and nuts 22 through (see FIG. 1).

[0022] The web 15b of the cross beam 15 is provided with loading portions 25, 25 that apply a horizontal load caused by displacement of the superstructure to the damper 10. A pair of the loading portions 25, 25 is provided corresponding to the damper bodies 12, 12.

[0023] The loading section 25 comprises a pair of splice plates 26, 26 fixed by bolts and nuts 27 to the underside of both widthwise sides of the web 15b of the cross beam 15, and a pair of opposing load plates 28, 28 suspended from the splice plates 26, 26. A reinforcing rib 30 is provided between the load plate 28 and the splice plate 26. The load-receiving section 13 of the damper body 12 is sandwiched between the load plates 28, 28, and the opposing inner surfaces of the load plates 28, 28 form the loading surface.

[0024] The damper 10 attached between the upper and lower structures as described above acts as follows: When a horizontal load acts on the upper structure 15 due to an earthquake or other cause, causing displacement, the horizontal load is transmitted from the loading portion 25 to the load-receiving portion 13 of the damper body 12, causing bending deformation of the damper body 12. Because the planar shape of the damper body 12 is an isosceles triangle, it behaves as a beam of equal strength attached to the clamping plate 20 of the mounting portion 17 with the base 12a as the fixed end, and is able to efficiently absorb the kinetic energy of the upper structure and damp vibrations.

[0025] Figure 5 shows the distribution of bending moment M, bending stress σ, and strain rate ε when a bending load F is applied to the free end of a cantilever beam. (a) is for a rectangular beam made of a rectangular plate, and (b) is for a beam with uniform strength made of an isosceles triangular plate with the base as a fixed end.

[0026] The distribution of section modulus Z is as shown in the figure, but in the case of the rectangular beam shown in (a), the section modulus Z is constant from the fixed end to the free end, so the bending stress σ and strain rate ε gradually decrease from the fixed end to the free end. In contrast, in the case of the uniform strength beam shown in (b), the section modulus Z gradually decreases from the fixed end to the free end, so the bending stress σ and strain rate ε become constant (uniform) from the fixed end to the free end.

[0027] Figure 6 is a graph comparing the load-displacement curves of a cantilever rectangular beam and a uniform strength beam of the same volume. With a rectangular beam, the fixed end yields under a small load, and once a certain allowable strain rate is reached, the other parts remain in the elastic range, making almost no contribution to energy absorption. In contrast, a uniform strength beam has a large yield load and continues to deform plastically even after yielding, allowing for a large amount of energy absorption. Therefore, it is desirable for the steel material used in the dampers of this invention to have a high yield point and large elongation.

[0028] As can be understood from the explanation with reference to Figures 5 and 6, when a horizontal load from the superstructure 15 acts on the damper 10, the damper body 12, which is a beam of uniform strength, experiences uniform bending stress and strain rate from its base 12a (see Figure 1) to the apex corner 12b, which is the loading point, and contributes to absorbing vibration energy over its entire length, resulting in good absorption efficiency, i.e., a large amount of energy absorption per unit volume of the damper body 12.

[0029] Furthermore, as shown in Figure 7, when a horizontal load P acts on the apex corner 12b of the damper body 12, a moment M is generated, which results in a torsional stress being generated in the cross beam 15, which is the superstructure, causing deformation as shown by the chain line. However, because the damper bodies 12, 12 are arranged so that the bisector of the apex angle points diagonally upward on the apex side, i.e., forming an inverted V shape, the distance S (see Figures 4 and 7) from the superstructure 15 to the load application point of the damper body 12 can be made as small as possible. This reduces the torsional stress acting on the cross beam 15, which is the superstructure, and allows the size of the cross beam 15 and the load-bearing portion 25 to be made compact.

[0030] Also, installation costs can be reduced because only one cross beam 15 is required to load the damper 10. Furthermore, the damper body 12 is provided with a knob-shaped load receiving portion 13, which has a cylindrical surface 13a that abuts on the loading surfaces of the loading plates 28, 28. Therefore, even if the damper body 12 deflects due to the load, the load receiving portion 13 can always abut on the loading surface.

[0031] 8 is a front view showing another embodiment. In the above embodiment, the damper 10 is shown in which a pair of damper bodies 12, 12 are connected to a single mounting plate 11, but in this embodiment, the damper is formed using only a single damper body.

[0032] The damper 30 of this embodiment comprises a mounting plate 31 and one damper body 32. As in the previous embodiment, the damper body 32 is a steel plate with an isosceles triangular planar shape. The mounting plate 31 is a rectangular steel plate with a predetermined width and the same length as the base 12a of the damper body 32, and is provided with a plurality of bolt holes 14. The apex corner 12b of the damper body 32 is provided with a load receiving portion 13 similar to that shown in the previous embodiment.

[0033] 9, the damper 30 is attached to both sides of the mounting portion 17, which is similar to that shown in the previous embodiment and is installed on the lower structure 16. That is, the mounting plate 31 is sandwiched between the pair of clamping plates 20, 20 so that the bottom side 12a of the damper body 32 coincides with the side side of the clamping plate 20, and is fastened and clamped with bolts and nuts 22.

[0034] The two side edges of the clamping plate 20 are inclined so that the distance between them widens as they go downward, i.e., they are inclined upward, so that in this mounted state the apex side of the bisector H of the apex angle of the damper body 32 faces diagonally upward. As in the above embodiment, a horizontal load is transmitted to the load receiving portion 13 of the damper body 32 from a loading portion similar to the above provided on the upper structure (not shown).

[0035] The above-described embodiments are merely examples, and the present invention can take various forms. For example, the shape of the damper body may be an isosceles triangle, and the sizes of the apex angle and base angle may take various values, and are not limited to the shapes of the embodiments. [Explanation of symbols]

[0036] 10: Damper 11: Mounting plate 11a: Side 12: Damper body 12a: Bottom 12b: Apex corner 13: Load receiving part 14: Bolt hole 15: Cross beam (superstructure) 16: Substructure 17: Mounting part 20: Clamping plate 25: Loading section 28: Loading plate

Claims

1. A steel plate damper installed vertically between the upper and lower structures of a bridge, a mounting plate fixed to the lower structure, the mounting plate having two opposing sides that are inclined such that the distance between the sides increases toward the lower portion; a pair of damper bodies each having a planar shape of an isosceles triangle whose base is connected to the two side edges of the mounting plate, A steel elastic-plastic damper for bridges, characterized in that the damper body is positioned so that the horizontal load caused by the displacement of the superstructure acts on the surface of the apex corner of the damper body in the normal direction.

2. A steel plate damper installed vertically between the upper and lower structures of a bridge, a mounting plate secured to the substructure; a damper body having a planar shape of an isosceles triangle with its base connected to one side of the mounting plate, The damper body is arranged so that the apex angle side of the bisector of the apex angle faces diagonally upward, and so that the horizontal load caused by the displacement of the superstructure acts on the surface of the apex angle of the damper body in the normal direction.

3. The steel elastic-plastic damper for bridges according to claim 1 or 2, characterized in that the apex portion is arranged so as to be sandwiched between a loading portion provided on the superstructure and having two loading surfaces facing both sides of the apex portion.

4. 4. A steel elasto-plastic damper for bridges according to claim 3, characterized in that a load-receiving portion having a cylindrical surface that abuts on the load-bearing surface of the load-bearing portion is provided at the apex corner of the damper body.

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