JPH09302620A - Base-isolation stacked rubber bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flange for a bride beam, which can withstand a direct onslaught of a disastrous earthquake. SOLUTION: Rubber boards 3 and metal boards 4 are alternately stacked one upon another between upper and lower flanges 1, 2, and PC steel wires 5 are extended through the entire stack of the boards and are fixed to the upper and lower flanges 1, 2, the positions and the sizes of the wires 5 being calculated so as to withstand a vertical load caused by a disastrous earthquake. Further, the opening ends of inner peripheral surfaces of fitting holes 12, 22 are preferably formed by conical surfaces 12, 22 which are enlarged by an angle α which is obtained from a formula; tanα=1/5 to 1/10. The tension of the PC steel wires 5 which is strong against vertical wave motion copes with the earthquake. The upper and lower flanges l, 2 cannot be separated from the stacked robber boards 3, thereby it is possible to inhibit the bridge beam from being broken.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing for supporting a bridge structure, and more particularly to a novel structure of a base-isolated laminated rubber bearing capable of withstanding a direct impact of the largest earthquake.

[0002]

2. Description of the Related Art Bearings arranged at both ends of a bridge structure are supported so that the structure can be expanded and contracted in accordance with changes in temperature, and are temporarily used when heavy objects such as automobiles pass through. It must withstand various live loads, and must be securely connected so that the bridge body does not separate from the foundation floor that supports it in the event of an earthquake. In recent years, laminated rubber bearings have been widely used as the most general form to meet these demands.

The laminated rubber bearing is between a lower shoe which is embedded in the foundation floor (bridge pier structure, so-called substructure) together with anchor bolts, and an upper shoe which is attached to the lower flange of the bridge structure (bridge girder structure, so-called superstructure). In addition, multiple flat plates of elastic material such as neoprene rubber are stacked and laminated, and a laminated body in which metal flat plates are alternately sandwiched between the layers to improve reinforcement and slidability is integrally molded. Refers to. In addition, a considerable number of prior arts in which any of various required functions are strengthened by further improving the basic form of the laminated rubber bearing can be recognized.

In Japanese Utility Model Publication No. 3-52809, Kamitsuku 1
a, a rubber laminated plate to be attached between the lower shoe 2a,
3 pieces 1 as shown in FIG.
It is characterized in that it is formed of a pair of rubber grits 101, 102, 103, and a friction plate 104 is incorporated on the upper surface of the central rubber grove 102. With this structure, the rubber crates 101 and 103 located on the left and right sides of the laminated rubber bearing have a cushioning function similarly to the conventional rubber crates, and the rubber crud 102 located at the center is
Since the friction plate 104 is provided on the upper surface of the girder, it has a damping function, so that it is possible to reduce the resistance force when the girder expands and contracts, and to exert the damping function at the time of an earthquake.

According to the prior art disclosed in Japanese Utility Model Laid-Open No. 2-109817, as shown in FIG. 6, an upper shoe 1b and a lower shoe 2b.
The laminated rubber bearing sandwiched between the two is integrally formed by the rubber bearings 106 and 107 with the lateral movement prevention plate 105 sandwiched therebetween, and is arranged so as to be close to both ends of the metal base plate 108 in the longitudinal direction of the bridge girder. The structural feature is that a stopper 109 for preventing movement of the bridge girder in the longitudinal direction is provided upright.
With this configuration, when a large horizontal seismic force in the longitudinal direction of the bridge girder is applied, the lateral movement prevention plate 105 abuts on the bridge girder longitudinal movement prevention stopper 109 to prevent shear deformation of the lower rubber bearing 107, and at the same time, the upper rubber bearing is supported. Since only 106 is sheared and deformed, it is stated that the stability of the bridge girder in the longitudinal direction of the bridge can be improved by a simple means.

However, these prior arts are related to the improvement before the Great Hanshin Earthquake, and when the connection between the bridge structure and the foundation floor was cut off and the largest earthquake such as this time, which suffered a great deal of damage, was hit directly, The necessity of re-questioning whether or not it could be completely tolerated came to be emphasized. According to the “Ministry of Construction / Seismic Isolation Design Method Manual for Road Bridges (Draft)” being promoted by the Civil Engineering Research Center, the measures proposed by the operating principle are presented as shown in Table 1 below. The specific configuration of is also illustrated, but as you can see from the table,
Mainly reinforced measures are based on laminated rubber bearings and added other requirements.

[0007]

[Table 1]

For example, as shown in FIG. 7, a seismically isolated laminated rubber bearing containing a lead plug has a metal reinforcing plate 110 and a laminated rubber plate between an upper plate 1c on which an anchor bar is erected and a lower plate 2c on which anchor bolts are vertically installed. This is a structure in which a lead plug 112 having a cylindrical shape is internally fitted by forming insertion holes in a laminated structure in which 111 and 111 are alternately stacked and integrally vulcanized and bonded. It also has a function to prevent lateral movement by standing side blocks 113 in the direction perpendicular to the bridge axis. The laminated rubber has a high rigidity in the vertical direction and a small rigidity in the horizontal direction, so it supports a large vertical load. , Make the cycle of the structure longer. That is, the functions of buffering and damping are high. The lead plug undergoes plastic deformation as the laminated rubber deforms, and seismic energy is absorbed. Rigidity of the lead plugs resists daily low level horizontal forces such as wind loads and braking loads, and prevents swinging. Compared to the conventional laminated rubber bearing due to its characteristics,
It is expected that the seismic isolation function will be further strengthened.

[0009]

The typical prior art illustrated here is such that the relative lateral positional fluctuations of the bridge and the bridge pier can connect the two even in an emergency such as an earthquake such as daily temperature change. It is common to point out the possibility of disconnection and disconnection as well as the possibility of falling off, and to propose a solution that focuses on preventing lateral movement of the laminated rubber bearing. Of course, even in the conventional technique of FIG. 5, it is explained that the vertical load is shared by each rubber bearing by adding the damping function by the friction force to the conventional cushioning function, so that the shear resistance can be reduced.
Although it can be evaluated that the insertion of the lead plug has nothing to do with the vertical strengthening even in the conventional technique of FIG. 7, it cannot be said that the configuration is aimed directly at improving the ability to resist the severe vertical movement in the vertical direction. With respect to the earthquake, there is no choice but to judge that the need for strengthening remains.

As a result of a detailed investigation of the actual conditions of damage to rivers and highways after the Great Hanshin Earthquake, the vertical vibration due to the largest earthquake was more severe than expected, and the prior art focused on horizontal oscillation. Attention was paid to the consideration that put a stone in the dogma which has been trying to strengthen. The present invention addresses the newly discovered problems of structures such as bridges, and aims to provide a new seismic isolation laminated rubber bearing that protects public property from a disaster by direct reinforcement means.

[0011]

A base-isolated laminated rubber bearing according to the present invention comprises a plurality of rubber flat plates 3 and metal flat plates which are interposed between a bridge structure and a foundation floor and are interposed between an upper shoe 1 and a lower shoe 2. Based on laminated rubber bearings that are alternately stacked with No. 4, a PC whose position and size have been calculated to withstand the vertical load associated with the largest earthquake
The structural feature is that the steel wire 5 penetrates all the rubber plates 3 and is fixed to the upper and lower shoes respectively. The PC steel wire referred to in the present invention includes not only a stranded wire formed by twisting a steel wire, but also a PC steel rod having a larger diameter formed by a single drawing process.

[0012] In the same manner as in the prior art, an external force that is applied to the bridge on a daily basis is countered by vertical rigidity of the laminated rubber against a vertical load, and shear deformation of the laminated rubber against a horizontal load. And the bending rigidity of PC steel wire. However, when an emergency situation occurs, the vertical wave motion is countered by the extremely strong tensile strength of the PC steel wire, as calculated in advance, so it is possible to withstand even the largest earthquake. It does not allow separation between the upper shoe and the laminated rubber bearings, and between the laminated rubber bearing and the lower shoe, and reliably protects the integrated behavior of the laminated rubber bearings. In addition, since a tensile force component in the lateral direction is applied to the horizontal vibration during an earthquake, the combined tension of horizontal force acts on the PC steel wire in addition to the vertical force. The strength of the highest level counteracts this combined external force, integrally restrains the laminated rubber bearing, prevents the separation of both, and does not allow separation between the bridge and pier.

On the basis of the above construction, the opening ends of the fitting holes 11 and 21 drilled in the upper and lower gears for fitting the PC steel wire 5 fixed in the upper gear 1 and the lower gear 2 in the vertical direction. hand,
An ideal embodiment can be obtained by adding the requirement of forming the conical surfaces 12 and 22 whose diameter is expanded at the inclination angle α included in the range of tan α = 1/5 to 1/10. That is, as described above, the PC steel wire is subjected to an oblique bending stress, which is a combination of a tensile force in the vertical direction and a horizontal roll, during an abnormal vibration such as an earthquake. The end of the PC steel wire is fixedly fixed inside the upper and lower troughs and fitted into the laminated rubber plate of the uppermost layer or the lowermost layer through the fitting holes formed in the upper and lower troughs from the ends. Therefore, the maximum bending stress concentrates on the PC steel wire at the boundary surface where the upper and lower rake surfaces with high rigidity and the rubber flat plate surface with low rigidity are in contact, and the outer circumference of the PC steel wire is sharply bent and can be cut at this position. Sex cannot be denied. For this reason, the inner peripheral surface of the insertion hole near the surface of the upper and lower shoes is formed by a conical surface whose diameter is expanded toward the opening, and the deformation of the PC steel wire is changed to a gentle bending, so that the breaking action based on an acute angle bending is performed. Can be relaxed. Although the inclination angle α is limited as described above, if tan α is larger than ⅕, the fixed restraint action of the laminated rubber bearing by the PC steel wire is excessively lost and the seismic isolation action becomes the largest earthquake. You can't compete and tan α is 1
If it is smaller than / 10, there is a concern that it may hit the side surface of the fitting hole and be subjected to a concentration action of bending stress, resulting in cutting. Therefore, the range of α is limited as described above.

[0014]

1 is a vertical sectional front view showing an embodiment of the present invention, FIG. 1 (A) is an overall view, and FIG. 1 (B) is an enlarged view of an end of a PC steel wire in an upper shoe. FIG. Upper shoe 1
A rubber flat plate 3 such as neoprene rubber between the lower shoe 2 and the lower shoe 2.
And the metal flat plate 4 made of stainless steel are alternately accumulated repeatedly to form a laminated rubber bearing. It goes without saying that the metal flat plate 4 is present for the purpose of reinforcing rigidity and improving slidability in the horizontal direction. In the embodiment shown in this figure, a four-layer rubber flat plate is shown, but selection is made from a wide range of about 2 to 20 layers depending on the scale, size and load amount of the bridge.

Select the necessary number and arrangement of PC steel wires 5 that penetrate all the rubber flat plates 3 and the metal flat plates 4 in common, and the upper end is fixed inside the upper gear 1 and the lower end is fixed inside the lower gear 2. Then install. What is the required number? When a direct earthquake hits one of the largest, the opposing force that can withstand the total absolute tensile force in the vertical direction that is assumed for the entire cross-sectional area of the laminated rubber bearing is PC steel wire ( It can be calculated from the tensile strength per unit cross-sectional area of (high tensile strength steel) and can be calculated from the cross-sectional area of a commercially available PC steel wire single item, and the number is specified by evenly distributing it to the cross section of the laminated rubber bearing and setting the position. To be done.

A fitting hole 11 for inserting the PC steel wire 5,
21 is bored in the upper shoe 1 and the lower shoe 2, and conical surfaces 12 and 22 having an outward opening and having an enlarged diameter are formed near the open end of the inner circumferential surface thereof. The inclination angle α for expanding the diameter is tan α = 1/5
A range of 1/10 is appropriate, and 1/8 is the optimum tilt angle. Since this conical surface is formed at the end, sharp bending does not occur even when bending deformation is applied to the PC steel wire, and it is replaced with deformation that draws a gentle bending line, and concentration of external force does not occur. It is possible to prevent the PC steel wire from breaking. In the case of this figure, the PC steel wire belongs to a type called a PC steel rod, and male and female screws are threaded on the upper and lower ends of the PC steel wire, and the fastening nuts 13 and 2 are inserted through the washers 14 and 24 and the hard rubber rings 15 and 25.
It is fastened by 3 and is firmly fixed to the upper shoe or the lower shoe.

When the PC steel wire is formed of twisted steel wire, it is not possible to thread male threads on both ends and fasten it with nuts as in the previous example, and therefore, as shown in FIGS. 2 (A) (B) (C). ) Is applied to fix the upper and lower shoes. That is, for the lower end of the PC steel wire 5A fixed to the lower shoe 2A, a dedicated machine (heading machine) is used to form a spherical head 51 as shown in FIG.
(6) The upper end of the PC steel wire 5A is cut to an appropriate length as shown in FIG. (B) and inserted through the upper shoe 1A, and the wedge 17 is driven in the anchor head 16 Thus, the end portion of the PC steel wire is locked by the wedge action of the inclined surface.

[0018]

FIG. 3 is a vertical sectional front view (A) and a plan view (B) assuming a specific embodiment of the present invention. Upper shoe 1, lower shoe 2
Are SS4 of 750mm x 750mm x 38mm respectively
No. 00 steel plate, the upper shoe 1 is welded to the girder lower flange K, and the lower shoe 2 is welded and fixed to the base plate P of the pier. Between the upper shoe and the lower shoe, four rubber flat plates 3 made of neoprene rubber having a thickness of 22 mm and a stainless flat plate 4 having a thickness of 2 mm are alternately accumulated to form a laminated rubber bearing. The design conditions are: bridge length x width = 50m x 18m (6 main girders) Reaction force per main girder: 15tonf x 50m x 1/2 x 1/6 = 62.5
tonf → 100 tonf shavings used Stress at yield point of PC steel wire: δa ＝ 78.5kgf / mm ² Vertical seismic coefficient of the largest earthquake: 0.4 (not confirmed at present, but considered as 4 times of old standard 1) Earthquake vertical Load Fv = 62.5 × 0.4 = 25tonf Tensile force of PC steel wire f = 78.5 × (π / 4) × 9.2 ² ＝ 78.5 × 6
6.43 = 5214kgf 6 present Use is calculated as _{F 6 = 5.214 × 6 = 31.284tonf} Fv = 25tonf <F 6 = 31.284tonf, the PC steel wire having an outer diameter of 9.2mm at the position of the six shown in FIG. (B) It was confirmed that by strengthening the six vertical penetrations, no division occurs in the laminated rubber bearing even if the largest earthquake hits directly.

As another example, as shown in FIG. 4, the results of calculation of the examination of the stress generated due to daily temperature changes and the material strength of PC steel wire are shown. FIG. 4 is a deformation diagram, and the position 5 '(dotted line) of the PC steel wire before deformation is 5 (actual battle) due to the generated stress
It has been transformed to the position of. Design conditions are: Girder length: L = 40 m Steel linear expansion coefficient: α = 12 × 10 ⁻⁶ Temperature change: Δt = ± 25 ° C. Bearing height: I = 200 mm Young's modulus of PC steel wire: E = 2 × 10 ⁶ The temperature change of the outside air and the strength of the PC steel wire are calculated as Kgf / mm ² .

The shift amount ΔL of the digit due to the temperature change is ΔL = L × α × Δt = 40 × 10 ³ × 12 × 10 ⁻⁶ × 2
5 = 12 mm The elongation ΔI of the PC steel wire is ΔI = (I ² + ΔL ² ) ^1/2 −I = (200 ² +12 ² ) ^1/2
-200 = 0.36 mm Working stress σ is σ = E × ΔI / I = 2.0 × 10 ⁶ × 0.36 / 200
= A 36 Kgf / mm ^2, can be cleared with a margin because much lower than 78.5Kgf / mm ² which is standardized as a safety factor of PC steel wire.

[0021]

As described above, the present invention exerts a strengthened function over the prior art with respect to the external force in the horizontal and vertical directions which is constantly loaded in the daily use condition. In addition, when the largest earthquake hits directly, it can withstand not only horizontal resistance, but also the strong vertical tremor that was strongly pointed out again as a result of this disaster investigation. With the addition of new functions, the city's functions are fully prepared, and in that sense, it is clearly superior to the latest conventional technology. Further, the present invention is not limited to the two or three embodiments illustrated as the embodiments, and can be connected to a dramatic improvement in performance by the relatively simple reinforcement work of reinserting the PC steel wire in all the prior art forms. Therefore, for example, the advantage that the disaster prevention function can be remarkably improved by adding the requirement of the present invention to the existing structure shown in FIG. 5, FIG. 6, FIG.

The effect peculiar to the invention according to claim 2 resides in that the reliability is extremely improved for the application of a bridge having a large girder length. As described above, the PC steel wire itself is extremely tough and has a high tensile strength. However, if the bending stress is locally concentrated, there is a possibility that the sharply bent portion will not endure and will be cut. Therefore, for bridges with long girders that have a large girder length and large horizontal movement, it is extremely effective to replace the bending direction with a gentle bend in order to disperse and absorb excessive tension. The effect of significantly improving the reliability of resistance in an overall emergency is remarkable.

[Brief description of drawings]

FIG. 1 is a vertical front view (A) showing an embodiment of the present invention and an enlarged view (B) of a main part.

FIG. 2 is a vertical sectional front view showing another embodiment of the present invention (A), an enlarged view of a fixed portion of an upper shoe and a PC steel wire (B), and an enlarged view of a fixed portion of a lower shoe and a PC steel wire ( C).

FIG. 3 is a vertical front view (A) and a plan view (B) of an embodiment of the present invention.

FIG. 4 is a vertical sectional front view for explaining a calculation procedure of another embodiment.

FIG. 5 is a vertical sectional front view of a conventional technique.

FIG. 6 is a vertical sectional front view of another conventional technique.

FIG. 7 is a perspective view of yet another prior art.

[Explanation of symbols]

 1 Upper shoe 2 Lower shoe 3 Rubber flat plate 4 Metal flat plate 5 PC steel wire 21 Fitting hole 22 Conical surface α Inclination angle

Claims (2)

[Claims] 1. A laminated rubber bearing in which a plurality of rubber flat plates 3 and metal flat plates 4 are alternately stacked between an upper shoe 1 and a lower shoe 2 and interposed between a bridge structure and a foundation floor. A seismically isolated laminated rubber bearing characterized in that a PC steel wire 5 adapted to withstand the vertical load caused by an earthquake penetrates all rubber plates 3 and is fixed to the upper and lower shoes respectively. 2. The inner peripheral surface open ends of the fitting holes 11 and 21 formed in the upper and lower shoes in order to fit the PC steel wire 5 fixed in the upper and lower shoes 1 and 2 in the vertical direction. Against
A seismically isolated laminated rubber bearing characterized by being formed by conical surfaces 12 and 22 that expand in diameter at an inclination angle α included in the range of tan α = 1/5 to 1/10.