JP2002180418A - Base isolation structure system in bridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base isolation system losing no merit of a base isolation support, causing no harmful action such as impact according to a linear characteristic of a bridge such as a straight line bridge and a curved bridge, and capable of effectively checking excessive displacement at earthquake time in a bridge structure supporting a bridge girder by the base isolation support displaceable in the whole horizontal directions. SOLUTION: In the bridge structure composed of a curved bridge girder having a displacement component in the bridge axis right-angled direction, a frictionally damping damper is interposed in the bridge axis right-angled direction between a lower structure and an upper structure for restricting the excessive displacement of the base isolation support at one or plural support points supported by the base isolation support.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seismic isolation structure system for a bridge, and more particularly to a seismic isolation structure for a continuous girder bridge in which a bridge girder is continuously supported by an elastic bearing capable of being displaced horizontally in all directions. About the system. More particularly, the present invention relates to a bridge having a curved or inclined bridge girder.

[0002]

2. Description of the Related Art In a curved bridge, a diagonal bridge, or a substructure, that is, a bridge having a narrow top portion of a pier, a structure (device) for limiting abrupt horizontal displacement generated in a bridge girder at the fulcrum in a direction perpendicular to the bridge axis at the time of an earthquake. That is, a displacement limiting structure is provided, but in the conventional displacement limiting structure, the moving body and the non-moving body (restricted body) limit the horizontal displacement by an abutting action with a certain play space, and It has a structure that responds to displacement in only one direction.Therefore, there is no resistance effect during displacement and a large impact is caused during operation, and the adverse effect of the impact cannot be ignored. is there. Bridges that require a displacement limiting structure in the direction perpendicular to the bridge axis may require a bridge with a small number of bearings on one support line, or the pier may move in the direction perpendicular to the bridge axis due to fluidization of the ground, in addition to the above structure. Bridges are also covered. In the above-mentioned bridge structure, the curvilinear bridge and the diagonal bridge have a displacement limiting structure at the end fulcrum, and the other bridges have a displacement limiting structure at the intermediate fulcrum in addition to the end fulcrum. Things. Furthermore, when a so-called rigid displacement limiting structure of the above structure is used at the end of a girder in a curved bridge, the expansion and contraction of the bridge girder due to a temperature change is restricted, and the bridge girder is likely to be caused by a sudden displacement during an earthquake. There is a concern that the inertia of the upper structure in the direction perpendicular to the axis is concentrated at the end of the girder. If the clearance of the displacement limiting structure is widened to avoid this, the impact force will increase during an earthquake.

On the other hand, recently, a so-called seismic isolation-type bridge using a seismic isolation bearing mainly composed of an elastic body for the support of the bridge is being adopted. That is, according to this seismic isolation system,
The seismic motion propagated from the substructure is prolonged with the seismic isolation bearing, and harmful vibration (particularly, resonance) is not transmitted to the superstructure, thereby preventing damage to the structure due to the seismic motion. As this seismic isolation bearing, a rubber bearing (laminated rubber) or a rubber bearing (LRB) with a lead plug in which a lead body is sealed in the rubber bearing is employed. Even for curved bridges and diagonal bridges with seismic isolation bearings, it is necessary to install a displacement limiting structure in order to cope with excessive displacement from the above point of view. In addition to this, the seismic isolation bearing has the feature of being able to perform functions in all horizontal directions. However, depending on this displacement limiting structure, the displacement in one direction is forcibly limited. The characteristics of the seismic bearing will be lost. In addition, this seismic isolation structure has been analyzed in a continuous bridge (curved bridge), where the variance of the inertial force in the direction perpendicular to the bridge axis tends to be unbalanced at each pier position. It is one of the technical issues. Therefore, in this seismic isolation system, a new displacement limiting structure that can limit harmful displacement without losing the characteristics of the seismic isolation bearing that functions in all directions has been developed and applied. It is desired to improve the characteristics of.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and relates to a seismic isolation support for a bridge structure in which a bridge girder is supported by an elastic seismic isolation bearing capable of being displaced in all directions in a horizontal direction. It is an object of the present invention to provide a new seismic isolation system capable of effectively preventing excessive displacement during an earthquake according to the linear characteristics of a bridge such as a straight bridge or a curved bridge without losing the features of the above. The present invention therefore does not forcibly limit the displacement of the bridge,
This is based on the knowledge that the purpose can be achieved by adding a friction damping type displacement limiting structure that reduces the displacement by applying a damping force in the direction in which the displacement is to be limited during an earthquake. Another object of the present invention is to apply the present invention to an earthquake horizontal dispersion structure using rubber bearings based on this finding.

[0005]

The present invention employs the following constitution in order to achieve the above object. The seismic isolation structural system of the bridge according to the first invention (first invention) of the present invention is provided by an elastic bearing capable of being displaced in all directions in the horizontal direction and having or not having damping performance, as described in claim 1. In a continuous girder curved bridge structure in which a curved / slanted bridge girder is continuously supported, excessive displacement of the bridge girder in a direction perpendicular to a bridge axis is limited at one or a plurality of support points supported by the elastic bearing. To this end, a friction-attenuating displacement limiting device that operates uniaxially is interposed between the substructure and the bridge girder so as to operate substantially in a direction perpendicular to the bridge axis. In the present invention, the friction damping type displacement limiting device has a characteristic described later (FIG. 5).
(b)), and is specifically shown in the following embodiments. In the above configuration, at least the support point at the end of the bridge girder is selected as a support point at which the friction damping type displacement limiting device is disposed, the elastic bearing is a lead plug-containing elastic bearing, and the friction damping type displacement limiting device is a bridge. Arrangement so as to allow displacement in the axial direction is a matter selected as appropriate. In the first invention, a seismic isolation structure system for a bridge which is a continuous girder bridge structure having a bridge girder which is likely to be displaced in the direction perpendicular to the bridge axis instead of the curved / slanted bridge girder constitutes another invention. Also in the present invention, the support point of the friction damping type displacement limiting device is selected at least at the end of the bridge girder, the elastic bearing is a lead plug-containing elastic bearing, and the friction damping type displacement limiting device is Arrangement so as to allow displacement in the bridge axis direction is a matter selected as appropriate.

(Operation) In normal operation, the slow expansion and contraction displacement of the bridge girder due to the temperature change is such that the displacement in the bridge axis direction is more prominent than in the bridge width direction (direction perpendicular to the bridge axis) and the rotational displacement is caused by the elastic deformation of the elastic bearing. Absorbs telescopic displacement. A friction-attenuated displacement limiting device arranged in the direction perpendicular to the bridge axis follows this displacement without interference and without resistance. When the pier vibrates due to the occurrence of an earthquake, this vibration propagates to the upper structure. However, in the elastic bearing, the short-period component is removed due to its elastic function, and the long-period component remains. Do not tell). The upper structure vibrates with its natural period (long period). When the elastic bearing has a damping performance, the vibration is quickly damped. At the same time,
The displacement limiting mechanism arranged in the direction perpendicular to the bridge axis also operates and contributes to its damping. When an excessive seismic force is input and sudden displacement in the direction perpendicular to the bridge axis appears at the support point of the bridge girder, the displacement limiting mechanism starts from the start of this displacement, continues to operate with the displacement, and sets the maximum value To prevent displacement exceeding a specified distance. This operation is continuous and there is no impact at the maximum. Furthermore, in the continuous girder curved bridge, the lateral displacement of the bridge girder at each support point can be minimized by increasing the resistance of the displacement limiting device at each support point. That is, in the seismic isolation system, the inertial force at the support points is dispersed and equalization is achieved.

According to a second aspect of the present invention, there is provided a continuous girder bridge structure in which a bridge girder is continuously supported by a rubber elastic bearing capable of being displaced in all directions in a horizontal direction. At one or a plurality of supporting points supported by a friction damping type damper interposed in the bridge axis direction between a lower structure and the bridge girder to limit excessive displacement of the elastic bearing. Features. This continuous girder bridge structure adopts a horizontal dispersion structure during an earthquake. (Operation) At a relatively small value of the resistance of the damper,
The response acceleration takes a minimum value, and the response acceleration increases as the resistance increases. Focus on reducing the response acceleration by adjusting the magnitude of the resistance of the damper,
It is possible to adjust whether emphasis is placed on reducing the response displacement, and the degree of freedom in design is increased.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a base isolation system for a bridge according to the present invention will be described with reference to the drawings. (First Embodiment) FIGS. 1 to 5 show a seismic isolation system for a bridge according to one embodiment (first embodiment), and show an example of application to a continuous girder curved bridge. That is, FIG. 1 shows the entire configuration of the fulcrum of the seismic isolation system, and FIGS. 2 to 5 show the partial configuration thereof. In the figure, B is a substructure such as a pier / abutment,
G is an upper structure such as a bridge girder. This bridge forms a multi-span continuous girder curved bridge. The bridge girder G has a linear (planar shape) curve shape with a predetermined curve radius and a predetermined cross slope. Apply load to B.

As shown in FIG. 1 in its entirety, the present seismic isolation system includes a seismic isolation support 1 mainly composed of a support S and a damper D between the lower structure B and the upper structure G. It is mainly composed of a displacement limiting mechanism 2 which is interposed with a predetermined arrangement relationship and exhibits a predetermined seismic isolation function. That is, the seismic isolation bearing 1 has at least a support function and a seismic isolation function, the displacement limiting mechanism 2 adopts a friction damping type that operates at the start of displacement, and the displacement limiting mechanism 2 is at right angles to the bridge axis. Arranged in the direction.

Hereinafter, the detailed structure of each part will be described. Seismic Isolation Bearing 1 (See FIGS. 1 to 4) In the present embodiment, the seismic isolation bearing 1 is mainly composed of a laminated rubber bearing S containing a lead plug. The laminated rubber bearing body (hereinafter, simply referred to as a bearing body) S including the lead plug has a rectangular shape as a whole, and has a laminated rubber body 10 having a predetermined thickness and a lead plug 11 sealed in the center of the laminated rubber body 10. These are sandwiched between the upper and lower mounting steel plates 12 and 13 and the upper structures G and
It is fixed to the lower structure B. In addition, the support body S is installed on the lower structure B via a leveling platform 14 that leveles the upper surface of the lower structure B. The leveling platform 14 may be integral with the pier B or may be separate. Further, the laminated rubber body 10 of the support body S includes a steel plate 15 and a rubber plate or rubber layer 1.
6 are laminated with each other and integrated by vulcanization bonding, and have characteristics of being easy to be horizontally deformed and having large vertical rigidity. 12a and 13a are mounting steel plates 12 and 1
3 through which an anchor bolt (not shown) embedded and fixed in the upper structure G and the lower structure B (leveling platform 14) is inserted and tightened with a nut (not shown). Is done. If the upper structure G and the lower structure B are made of steel, the support body S can be fixed by welding. The bearing body S of the seismic isolation bearing part 1 is
Two are juxtaposed. However, the number of installations is not limited to two, and an additional number is added to stably install the upper structure G. And this seismic isolation bearing 1
Is the support function of the superstructure (bridge girder) G and the substructure (pier)
It plays the seismic isolation function of the ground motion propagated through B.

Displacement limiting mechanism 2 (see FIGS. 1, 2 and 5) In this embodiment, the displacement limiting mechanism 2 is a friction damping type lead extrusion damper (hereinafter simply referred to as "a") having a function of adding damping force. D) (referred to as “lead damper”).
As shown in FIG. 5 (a), the lead damper D has a cylindrical cylinder portion 20, a piston rod portion 21 which is moved into and out of the cylinder 20, and a lead body sealed in the cylinder portion 20. 22. The piston rod 21 is a lead 2
2 has a raised portion 21a and a stopper portion 21b at the tip thereof, and keeps a gap distance between a and b before and after the stopper portion 21b. The protrusion 21a plastically fluidizes the lead body 22 by moving through the lead body 22 with a forcing force, and absorbs the forcing force with its deformation energy. At the tip of the cylinder part 20 and the tip of the piston rod part 21, there are provided attachment parts 23A and 23B, respectively. The lead damper D has a very clear hysteresis characteristic as shown by a hysteresis curve in FIG. 5 (b) by plasticizing the lead body 22, and has a friction damping characteristic. That is, a fixed horizontal resistance to the displacement appears. High energy absorption efficiency. The stroke of the lead damper D is more restricted by the plastic flow resistance of the raised portion 21a than by the restriction of the stopper portion 21b.

In the displacement limiting mechanism 2 of this embodiment, two lead dampers D are provided. For this reason, the columnar reaction force receiving member 25 is firmly fixed to the lower structure B at an intermediate portion between the two seismic isolation bearings S arranged side by side.
A is protruded, and a rib 26B is protruded from the upper structure so as to face the rib 26A. Each of the lead dampers D has a mounting portion 23A and a rib 26A, and a mounting portion 23B and a rib 26B between each corresponding seismic isolation bearing S of the corresponding upper structure G and the reaction force receiving member 25. It is swingably attached via 27. The ribs 26A and 26B
May be swingable in the horizontal direction. In this case, the rib 26
A and 26B together with the pin 27 constitute a so-called universal joint that allows rotational displacement in any direction. In the displacement limiting mechanism 2, the lead damper D is arranged on a line including the centers of the two seismic isolation bearings S, that is, in the direction perpendicular to the bridge axis, and corresponds to the displacement in the direction perpendicular to the bridge axis. However, a displacement different from the direction perpendicular to the bridge axis and a slight inclination (shift) are allowed. That is, displacement in installation,
The bridge girder is allowed to displace in the bridge axis direction. Thus, the displacement limiting mechanism 2 has a function of suppressing excessive movement of the upper structure G.

(Displacement Characteristics of Curved Bridge) In a bridge girder having a predominant length in the bridge axis direction, the expansion and contraction in the bridge axis direction is larger than in the direction perpendicular to the bridge axis. The displacement in the direction is also added. Further, a rotational displacement is applied to each fulcrum by a moving load loaded on the bridge girder. In this curved bridge, the above-mentioned fulcrum displacement is absorbed by the elastic deformation of each bearing.

(Operation / Effect of this Embodiment) This seismic isolation structure system is applied to a multi-span continuous girder curved bridge, exhibits the following operation, and has an effect. FIG. 6 shows this multi-span continuous girder curved bridge. Here, B1, B2, B3, and B4 are piers, and the bridge girder G that forms a curve is the pier B1,
Each of the two seismic isolation bearings S is supported on B2, B3, and B4, and a displacement limiting mechanism 2 including a lead damper D is arranged in each pier in a direction perpendicular to the bridge axis. FIG. 1 shows this arrangement in each pier.

Normally, in the slow expansion and contraction displacement of the bridge girder G due to the temperature change, the displacement in the bridge axis direction is more prominent than in the bridge width direction, and the elastic deformation of the seismic isolation bearing S absorbs the expansion and contraction displacement together with the rotational displacement. In addition, the lead plug 11 of each seismic isolation bearing S and the lead body 22 of the lead damper D do not have a particularly large resistance to the gradual displacement, and are allowed. In a continuous girder curved bridge, displacement in the direction perpendicular to the bridge axis appears at the end pier B1 (or B4), and this displacement is permitted by the omnidirectional seismic isolation bearing S and the lead damper D.

Due to the occurrence of the earthquake, the piers B1, B2, B
When B3 and B4 vibrate, the vibration propagates to the upper structure G. However, in the seismic isolation bearing S of the seismic isolation support 1, short-period components are removed by the flexible structure function of the laminated rubber body 10,
Long-period components remain and do not transmit harmful vibrations (resonant vibrations) to the upper structure G. Then, the upper structure G vibrates with its natural period (long period). The seismic isolation bearing S exhibits a large energy absorption characteristic due to the deformation of the lead plug 11, and quickly attenuates the vibration of the upper structure G. At the same time, the lead damper D of the displacement limiting mechanism 2 also operates,
The hysteresis characteristic contributes to the attenuation of the upper structure G. In a continuous girder bridge, large vibrations in the direction perpendicular to the bridge axis also appear at each of the piers B1 to B4. However, the omnidirectional seismic isolation bearing S attenuates this lateral vibration, and a lead damper installed on each pier. The transverse vibration is attenuated more quickly by D. The relationship between the resistance and the lateral displacement of the lead damper D is shown in FIG.
The lateral displacement on each pier hardly appears when the resistance of the lead damper D is set to an appropriate value (for example, about 20 tons).

However, when an excessive seismic force is input, the bridge girder G is further displaced in the lateral direction with respect to the pier B, and together with this displacement, the lead damper D of the displacement limiting mechanism 2 is moved. It reaches the set maximum value and does not move beyond the specified distance. This prevents excessive displacement of the upper structure G, suppresses lateral displacement of the seismic isolation bearing S, and prevents harmful buckling. FIG. 7B shows the displacement of the bridge girders on the piers B1 to B4 in the lateral direction, that is, in the direction perpendicular to the bridge axis, when the set resistance value of the lead damper D is changed. A shows the displacement of each pier when there is no lead damper D, and B, C, and D show the displacement when the set resistance value of the lead damper D is sequentially increased.
In (d), the displacement of the bridge girder on each pier is equalized. That is, the equalization of the inertial force is almost achieved.

As described above, according to the present seismic isolation system, the seismic isolation function of the seismic isolation bearing S is exhibited without any hindrance, and the lateral displacement of the bridge girder G due to excessive earthquake motion is reduced. It does not impact and does not damage the seismic isolation bearing S or the superstructure G because it operates continuously in this blocking process. In addition, by appropriately selecting the set value of the lead damper D on each pier, the displacement on each pier can be freely determined, and the degree of freedom in design is large. Further, the lead damper D is not disposed on all piers, and a suitable effect can be obtained by selecting an appropriate pier (usually an end pier).

(Second Embodiment) FIG. 8 shows still another embodiment (second embodiment) of a base isolation system for a bridge according to the present invention. Here is an application example of. In the figure, G is a continuous digit forming a straight line,
B1 to B8 are piers arranged in series, and a rubber bearing R is disposed on the pier, and a continuous girder G is provided via the rubber bearing R.
Is installed. According to the arrangement of the rubber bearings R, two rubber bearings R are arranged at intervals. In this embodiment, a friction damping type lead damper D is further interposed between the pier B and the bridge girder in each pier B so as to operate in the bridge axis direction.
The structure of the lead damper D conforms to that shown in FIG.

In the seismic isolation system of this embodiment, the rubber bearing R functions as an isolator, that is, a rubber bearing for horizontal force distribution during an earthquake, the lead damper D functions as an energy absorbing device, and the respective functions interfere with each other. It is characterized by adopting a so-called function separation structure.

The seismic isolation system has the following functions and characteristics. As shown in FIG. 9, the relation between the magnitude of the resistance of the lead damper D and the response acceleration at the time of the earthquake shows that the response acceleration takes a minimum value and the resistance increases when the resistance of the lead damper D is relatively small. As the response increases, the response acceleration increases. The relationship between the magnitude of the resistance of the lead damper D and the response displacement is as shown in FIG. Therefore, by adjusting the magnitude of the resistance of the lead damper D, it becomes possible to adjust whether to focus on reducing the response acceleration or the response displacement. The degree of freedom of design is higher than that.

According to this seismic isolation structure system, the seismic isolation structure having a smaller displacement during an earthquake is possible than the conventional seismic isolation bearing of integrated function due to the excellent energy absorption performance of the friction damping type lead damper D. , So the rubber bearing can be designed smaller,
Even if the cost of the lead damper D is added, the cost can be reduced as compared with the conventional seismic isolation bearing of integrated function.

The present invention is not limited to the above embodiment, and various design changes can be made within the scope of the basic technical concept of the present invention.

[0024]

According to the seismic isolation structure system of the bridge of the present invention, the seismic isolation function is exerted without hindering the omnidirectional displacement function of the seismic isolation bearing, and the lateral displacement of the superstructure due to excessive earthquake motion. , And since it operates continuously at the displacement leading to this inhibition, it does not generate an impact,
Neither the seismic isolation bearing nor the superstructure is damaged. In addition, by appropriately selecting the set resistance value of the displacement limiting device on each substructure, the displacement of the bridge girder on each substructure can be freely determined, and the degree of freedom in design is large. Further, the displacement limiting device is not disposed on all the piers, and a suitable effect can be obtained by selecting an appropriate pier. According to the seismic isolation structure system of the bridge employing the horizontally distributed structure of the present invention, the seismic isolation structure with small displacement during an earthquake is possible due to the energy absorption performance of the lead damper, so that the rubber bearing can be designed to be small and the cost can be reduced. Is achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a base isolation system for a bridge according to the present invention.

FIG. 2 is an enlarged view of a main part thereof.

FIG. 3 is a structural view (a cross-sectional view taken along line 3-3 in FIG. 4) of a bearing of one component of the seismic isolation system.

FIG. 4 is a sectional view taken along line 4-4 in FIG. 3;

FIG. 5 (a) is a configuration diagram of a lead damper as one component of the seismic isolation system. (b) The figure shows the characteristic (history curve).

FIG. 6 is a schematic diagram of a seismic isolation system for a multi-span continuous girder curved bridge.

FIG. 7 (a) is a damper resistance-displacement diagram. (b) Diagram showing horizontal displacement on the pier.

FIG. 8 is a side view of another embodiment of the base isolation system for a bridge according to the present invention.

FIG. 9 is a damper resistance-response acceleration diagram.

[Explanation of symbols]

G: Upper structure (bridge girder), B: Lower structure (pier), S: Seismic isolation bearing, D: Friction damping type damper, R: Rubber elastic bearing,
1 ... seismic isolation bearing section 2 ... displacement limit mechanism section

Continuation of the front page (72) Inventor Hiroe Uno 1-3-2 Shiba-Daimon, Minato-ku, Tokyo Oil industry F-term (reference) 2D059 AA05 AA37 GG05 GG59 3J048 AA02 AC02 AC05 BA08 BD08 BE12 CB06 DA01 EA39

Claims (7)

[Claims] 1. A continuous girder curved bridge structure comprising a curved girder and a bridge girder continuously supported by an elastic bearing capable of being displaced in all directions in a horizontal direction and having or not having damping performance, wherein the elastic bearing is provided. At one or a plurality of support points supported by the bridge girder, a friction damping type displacement limiting device that operates uniaxially between a substructure and the bridge girder to limit excessive displacement of the bridge girder in a direction perpendicular to the bridge axis is substantially provided. A seismic isolation system for a bridge, which is interposed so as to operate in a direction perpendicular to the bridge axis. 2. The seismic isolation system for a bridge according to claim 1, wherein the support point at which the friction damping type displacement limiting device is disposed is at least a support point at an end of a bridge girder. 3. The seismic isolation system for a bridge according to claim 1, wherein the elastic bearing is a lead plug-containing elastic bearing. 4. The seismic isolation system for a bridge according to claim 1, wherein the friction damping type displacement limiting device is arranged to allow displacement in the bridge axis direction. 5. A seismic isolation structure system for a bridge which is a continuous girder bridge structure having a bridge girder which is likely to be displaced in a direction perpendicular to the bridge axis instead of the curved / slanted bridge girder of claim 1. 6. A continuous girder bridge structure in which a bridge girder is continuously supported by a rubber elastic bearing capable of being displaced in all directions in a horizontal direction, wherein at one or a plurality of support points supported by the rubber elastic bearing, A seismic isolation system for a bridge, wherein a friction damping damper is interposed between a lower structure and the bridge girder in a bridge axis direction to limit excessive displacement of a bearing. 7. The seismic isolation system for a bridge according to claim 6, wherein the friction damping type damper employs a plastic flow type lead damper.