JP4113458B2 - Bridge structure - Google Patents

Description

【００２２】
上記の固有周期を用いて、道路橋の設計水平震度算定式より各地震時ごとの設計水平震度を算定した結果を以下に示す。なお、本解析においては設計上最も堅い地盤である地盤種別Ｉ種の地盤を対象とする。
【００２３】
大規模地震（タイプＩ地震）の設計水平震度の算定式を（２）、（３）に示す。
【００２４】
【数２】
Ｔ＜１．４秒の場合 ｋ＝０．７・・・・・・・・・・（２）
Ｔ≧１．４秒の場合 ｋ＝０．８７６Ｔ^−２／３ ・・・ （３）
【００２５】
ここで、Ｔは固有周期（秒）を、ｋは設計水平震度を示す。
【００２６】
大規模地震（タイプII地震）の設計水平震度の算定式を（４）〜（６）に示す。
【００２７】
【数３】
Ｔ＜０．３秒の場合 ｋ＝４．４６Ｔ^２／３ ・・・・・（４）
０．３秒≦Ｔ≦０．７秒の場合 ｋ＝２．０ ・・・・・・・・・（５）
Ｔ＞０．７秒の場合 ｋ＝１．２４Ｔ^４／３ ・・・・・（６）
【００２８】
上記（２）〜（６）式より構造物の固有周期が長周期化するにつれて設計水平震度（地震時外力）も小さくなる傾向にある。
【００２９】
【表２】

【００３０】
解析結果より、タイプＩ地震、タイプII地震ともに構造物の固有周期を長周期化することができ、地震時外力（設計水平震度）を低減することが可能となる。
【００３１】
【発明の効果】
本発明の橋梁の構造は以上説明したようになるから次のような効果を得ることができる。
＜イ＞大規模地震に対するラーメン構造の橋梁の靭性性能の向上を安価に実現できる。
＜ロ＞大規模地震後の橋梁の損傷箇所の補修や復旧が比較的容易となる。
【図面の簡単な説明】
【図１】本発明の橋梁の構造の実施例の正面図。
【図２】本発明の橋梁の構造の実施例の縦断図。
【図３】（ａ）橋脚とブレス材の連結部の実施例を示した説明図。（ｂ）橋脚とブレス材の連結部の実施例を示した説明図。（ｃ）ブレス材の交差部の実施例を示した説明図。
【図４】構造解析で使用した橋軸方向の４径間連続ラーメンモデルを説明した図であり、（ａ）平常時及び中規模地震時のモデル図。（ｂ）大規模地震時のモデル図。
【符号の説明】
１・・・上部工
１１・・橋桁
１２・・床版
２・・・橋脚
３・・・ブレス材
４・・・橋軸直角方向
５・・・橋軸方向
７１・・連結部
７２・・格点部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of a bridge composed of a bridge pier, a floor slab, and a brace material that connects the piers.
[0002]
[Prior art]
Since the Hyogoken-Nanbu Earthquake, the structure has been required to have a high level of seismic performance due to the review of seismic standards. The structure with seismic performance can resist the external force at the time of a medium-scale earthquake by the rigidity of the structure (stiffness within the elastic range of the members constituting the structure), and the earthquake at the time of a large-scale earthquake It is a structure that can follow the external force by the toughness performance of the structure (performance considering the non-linear range of the members constituting the structure). In other words, when trying to resist the external force at the time of a large-scale earthquake with only the rigidity (elastic range) of the structure, the scale of the structure becomes large at each stage, which is uneconomical. The toughness performance of the structure is positively taken into account, and the design and construction based on economical and valid structural property evaluation is performed.
Here, a medium-scale earthquake is an earthquake motion that has a high probability of occurring during, for example, a bridge service period. On the other hand, a large-scale earthquake is a strong ground motion with a low probability of occurring during the in-service period of a bridge, for example.
[0003]
In the conventional bridge, the bridge pier is constructed on the footing in either the pile foundation type or the direct foundation type, and the superstructure such as the bridge girder and the floor slab is constructed on the bridge pier. Moreover, in order to absorb the external force (earthquake energy) at the time of the above-mentioned large-scale earthquake, there may be a case where a seismic isolation bearing using high-damping rubber is provided between the pier (or abutment) and the superstructure. Such a seismic isolation bearing is composed of, for example, laminated rubber containing lead plugs, and normal traffic loads and superstructure loads are transmitted to the pier via the highly rigid lead plugs. Also, for seismic forces above a certain level, laminated rubber absorbs earthquake energy based on principles such as hysteresis damping and viscous damping, and the seismic force is reduced by extending the natural period of the bridge. .
[0004]
[Problems to be solved by the invention]
The above-described conventional bridge structure has the following problems.
It is uneconomical to install expensive seismic isolation bearings as a countermeasure for large-scale earthquakes with a very low probability of occurrence during the in-service period of the bridge.
[0005]
OBJECT OF THE INVENTION
The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a bridge structure that does not require a seismic isolation support as a countermeasure for a large-scale earthquake. Another object of the present invention is to provide a bridge structure in which the structure does not break brittlely even in a large-scale earthquake motion.
The present invention achieves at least one of these objects.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the bridge structure of the present invention is a bridge structure composed of a superstructure consisting of a bridge girder and a floor slab and a bridge pier, and is spaced in the direction of the bridge axis and the direction perpendicular to the bridge axis. A bridge having a ramen structure is constituted by the bridge pier provided in a plurality, the superstructure composed of the bridge girder and the floor slab provided on the upper part of the pier, and a brace material for connecting the bridge piers in parallel, the bridge axis perpendicular direction of the pier between the breath was ligated into material provided non damage for the seismic force of the earth Shinji, the breath material was ligated into the piers between the bridge axis direction the earthquake It is a bridge structure characterized by being able to break against external forces during an earthquake.
[0007]
Further, the structure of the bridge described above is a connecting portion between the brace material provided in the bridge axis direction and the bridge pier, or a breakage point that can be damaged when an external force at the time of a large-scale earthquake is applied to the bridge. It is possible to use a bridge structure characterized by a grading part between the brace materials.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0009]
<A> Large-scale earthquakes A large-scale earthquake is an earthquake with a high intensity but a low probability of occurring during the in-service period of a structure (bridge). Large-scale earthquakes can be broadly divided into plate boundary earthquakes (type I earthquakes) and inland earthquakes (type II earthquakes). A typical example of Type I ground motion is the Kanto Earthquake around Tokyo, and a typical example of Type II ground motion is the Hyogo-ken Nanbu Earthquake.
A type I earthquake is an earthquake in which a large amplitude repeatedly acts for a long time, and a type II earthquake is an earthquake having a very large intensity although its duration is short.
In seismic design, the external force during an earthquake (horizontal design during an earthquake) acting on the structure based on the relationship between the natural period of the structure and the frequency characteristics of the ground motion (acceleration response value calculated for each natural period for a specific ground motion) It is common to calculate seismic intensity. Although type II earthquakes have a larger acceleration response value than type I earthquakes, the rate of decrease in acceleration response values is high when the natural period extends to a long period (for example, the natural period is 1.0 seconds or more) from the ground motion characteristics described above. . However, both Type I and Type II earthquakes have the common point that the external force during an earthquake decreases as the natural period of the structure becomes longer.
Therefore, by extending the natural period of the structure, the external force acting on the structure can be reduced, and the structure of the structure can be slimmed.
The structure of the bridge of the present invention provides a structure capable of increasing the natural period of the structure (bridge) at a low cost as described above.
A medium-scale earthquake is an earthquake (approximately an acceleration of about 200 gal) that has a high probability of occurring during the in-service period of the bridge but is not large.
[0010]
<Ro> Ramen bridge (Figs. 1 and 2)
The structure of the bridge targeted by the present invention is a ramen structure. A plurality of bridge piers 2 arranged in parallel in the bridge axis direction 5 and the bridge axis perpendicular direction 4 are connected at the upper part by a bridge girder 11, and the bridge girder 11 is integrated with the floor slab 12, whereby the bridge axis direction 5 and the bridge axis right angle are integrated. A ramen structure in direction 4 is formed.
The bridge girder 11 can be provided only in the bridge axis direction 5 or in both the bridge axis direction 5 and the bridge axis perpendicular direction 4. When the bridge girder 11 is provided only in the bridge axis direction 5, the members constituting the rigid frame structure in the direction perpendicular to the bridge axis 4 are the pier 2 and the floor slab 12. In other cases (when the bridge girder 11 is provided only in the bridge axis direction 5 and when the bridge girder 11 is provided in both the bridge axis direction 5 and the bridge axis perpendicular direction 4), the members constituting the ramen structure are It becomes the pier 2 and the bridge girder 11.
The connecting method of the pier 2 and the bridge girder 11 is preferably a rigid coupling structure constructed by embedding the pier 2 in the bridge girder 11.
[0011]
Moreover, the pier 2 used in the present invention can also be used as a pile foundation. That is, a pile (bridge pier 2) is driven into (or embedded in) the ground and protrudes on the ground, and the bridge girder 11 is constructed on the top of the pile (pier pier 2). According to such a structure, since the time and cost for constructing the footing can be reduced, a significant effect can be expected in terms of construction period and construction cost.
In addition, as a support mechanism of a pile, the friction pile which expects much support force to the surrounding surface friction force other than the support pile which penetrates a pile into a support ground and supports can be used.
Since the pile needs to have the performance as the pier 2, it is necessary to have the required bending rigidity, shear rigidity, and compression characteristics. Considering the strength characteristics and workability described above, it is preferable to use a steel pipe pile as the pile (pier 2). Moreover, in order to ensure a required strength characteristic, it is good also as a pile which filled the concrete in the steel pipe and was reinforced.
[0012]
<C> Breath material The brace material 3 is provided to increase the rigidity of the rigid frame structure by connecting the parallel piers 2 to each other. Various methods of joining the brace material 3 can be selected. For example, a predetermined angle (for example, 45 degrees, 60 degrees, etc.) with respect to the pier 2 so that the two brace members 3 intersect each other in each of the parallel piers 2. ) Is generally used. Such a grading part can be reinforced by using a grading part plate 32 or the like (see FIG. 3C). When a horizontal force or the like during an earthquake acts on the ramen frame, the ramen frame is displaced by the horizontal force, and a tensile force is generated in one of the brace members 3 along with the displacement. However, since the overall rigidity of the frame structure incorporating the brace material 3 is improved compared to the case without the brace material 3, if the brace material 3 has a strength capable of resisting the tensile force, high rigidity is maintained. In this state, the amount of displacement of the entire frame can be kept low. On the other hand, when the brace material 3 breaks without resisting the tensile force, the displacement amount of the entire rigid frame frame increases, and the stress generated in the rigid frame structural members (such as the pier 2 and the bridge girder 11) as the displacement amount increases. Will also increase.
Here, regarding the breakage of the brace material 3, the brace material 3 itself breaks due to insufficient tensile strength, and the connecting portion 71 between the brace material 3 and the pier 2 (or the bridge girder 11) before the brace material 3 breaks. It is conceivable that the rating part 72 between the (joint) or the brace material 3 is broken.
[0013]
The bridge structure of the present invention has a structure in which the brace material 3 in the direction perpendicular to the bridge axis 4 of the bridge can resist external force during the earthquake in the event of a large-scale earthquake, and the brace material 3 in the bridge axis direction 5 is large. It is preferable to adopt a structure that allows damage to the external force during an earthquake during a large-scale earthquake.
In other words, the bridge material 3 in the bridge axis direction 5 and the bridge axis perpendicular direction 4 is not damaged during normal and medium-scale earthquakes, and does not cause excessive displacement in the entire bridge. This is because excessive displacement may interfere with normal use of the bridge.
On the other hand, in the case of a large-scale earthquake, while securing the rigid frame structure in the direction perpendicular to the bridge axis 4, the natural period in the bridge axis direction 5 is lengthened to absorb and relax the energy during the earthquake with the toughness performance in the bridge axis direction 5 The goal is to. In order to make the structure capable of resisting the external force at the time of a large-scale earthquake with the rigidity of the entire rigid frame frame in the direction of the bridge axis 5, it is necessary to use excessive members, and as other measures are expensive This is because it is uneconomical to use any structure, although it is possible to install a seismic isolation bearing. In addition, a decrease in rigidity in the direction perpendicular to the bridge axis 4 will cause instability of the bridge structure, and a span length sufficient to ensure large toughness in the direction perpendicular to the bridge axis 4 is generally not secured. some reason, the bridge axis perpendicular 4 is for a structure such as brace member 3 is not a broken.
[0014]
As for the method of joining the brace members 3 in the bridge axis direction 5 and the bridge axis perpendicular direction 4, for example, as shown in FIGS. 1 and 2, in the bridge axis perpendicular direction 4, the bridge piers 2 connected in parallel cross each other. Two sets (or three or more sets) of the brace members 3 can be installed, and in the bridge axis direction 5, the cross brace members 3 can be provided as one set (or less than the number of sets in the direction perpendicular to the bridge axis 4). Also, the brace material 3 used in the direction perpendicular to the bridge axis 4 selects the brace material 3 that can withstand the external force at the time of the large-scale earthquake, and the brace material 3 used in the bridge axis direction 5 has an external force during the medium-scale earthquake. However, it is possible to select a brace material 3 that can resist the external force during a large-scale earthquake but does not have a proof strength.
Although the material which can ensure desired strength can be selected as the brace material 3, for example, the H-type steel material 33, the L-type steel material 34, the C-type steel material, etc. can be used. It is also good to reinforce it with such as. Further, in the connecting portion 71 between the brace material 3 and the bridge pier 2, the connecting portion 71 is reinforced by performing reinforcement such as welding a stiffening plate to the web and flange of the H-shaped steel material 33 used as the brace material 3. You can also.
[0015]
Further, in the bridge axis direction 5, the breaking strength of the connecting portion 71 such as the brace material 3 and the pier 2 or the grading portion 72 of the brace materials 3 can be designed to be equal to or less than the breaking strength of the brace material 3. . For example, when the plate (gusset plate 31) and the brace material 3 that are welded to the place where the bridge pier 2 and the bridge girder 11 are joined as a structure of the connecting portion 71 are bolted (see FIG. 3B), the bolt 92 to be used is used. By adjusting the specifications and the number of bolts, the shear strength of the bolt 92 can be made equal to or less than the tensile strength of the brace material 3. Further, for example, there is a method of joining the H-shaped steel material 33 to the pier 2 by welding 91 (see FIG. 3A). In addition, various methods can be selected for reducing the tensile strength of the brace material 3 that uses the proof strength of the structure of the connecting portion 71 to be used.
By making the breakage point into the connecting part 71 such as the brace material 3 and the bridge pier 2 or the grading part 72 between the brace material 3 as described above, the breakage point can be easily identified, and restoration and repair after a large-scale earthquake can be performed. Can be easy.
[0016]
<D> Analysis method and analysis results Among the bridge structures in the present invention, the brace material 3 is damaged in the case of a large-scale earthquake in the bridge axis direction, thereby reducing the rigidity of the entire ramen structure and improving the toughness. Structural analysis was performed to demonstrate that the natural period of the structure can be increased. It is verified that the external force (acceleration response spectrum) acting on the structure can be reduced by increasing the natural period.
In the structural analysis, a 4-span continuous ramen model is used. In the embodiment of FIG. 2, the cushioning material 6 is provided between the bridge girder 11 and the floor slab 12 at intervals of 4 spans in the direction of the bridge axis. Therefore, the analysis model is a four-span continuous ramen model corresponding to the embodiment.
[0017]
Fig. 4 (a) shows a model diagram in service and during a medium-scale earthquake. The bridge girder 11, the pier 2, and the brace material 3 are a bridge girder beam model 81, a pier beam model 82, and a brace material beam model 83, respectively, and a portion of the pier 2 (pile) embedded in the ground has a horizontal spring 84 and a vertical The spring 84 is modeled. In this model, since the brace material 3 is not damaged (designed so as not to be damaged), it is a constituent member constituting the rigid frame structure. On the other hand, FIG. 4B shows a model diagram after the brace material 3 (or the connecting portion 71 such as the brace material 3 and the pier 2 or the grading portion 72 between the brace materials 3) is damaged during a large-scale earthquake. Regardless of the location where the breakage occurs, since the brace material 3 no longer functions as a tensile material after the breakage, the brace material 3 is excluded from the constituent members constituting the ramen structure.
The structural analysis was performed by calculating the amount of displacement at the inertial force application position of the structure by applying a predetermined horizontal force (inertial force) during earthquake for each model and obtaining the natural period. This calculation method is based on the Road Bridge Specification / Description (V Japan Earthquake Association, December 1996 Japan Road Association) (hereinafter simply “Road Bridge”).
The formula for calculating the natural period is as follows.
[0018]
[Expression 1]
T = 2.01√δ (1)
[0019]
Here, T represents the natural period (second) of the structure, and δ represents the displacement (m) at the inertial force acting position when a predetermined inertial force is applied to the structure at the inertial force acting position.
[0020]
The results of natural period at the time of medium-scale earthquake and large-scale earthquake are shown below.
[0021]
[Table 1]

[0022]
The results of calculating the design horizontal seismic intensity for each earthquake using the above-mentioned natural period and the design horizontal seismic intensity calculation formula for the road bridge are shown below. In this analysis, the ground of type I, which is the hardest ground in design, is targeted.
[0023]
Calculation formulas for the design horizontal seismic intensity of large-scale earthquakes (Type I earthquakes) are shown in (2) and (3).
[0024]
[Expression 2]
In the case of T <1.4 seconds k = 0.7 (2)
In the case of T ≧ 1.4 seconds k = ^{0.876T -2/3} ··· (3)
[0025]
Here, T represents the natural period (second), and k represents the design horizontal seismic intensity.
[0026]
Calculation formulas for the design horizontal seismic intensity of large-scale earthquakes (type II earthquakes) are shown in (4) to (6).
[0027]
[Equation 3]
In case of T <0.3 seconds k = 4.46T ^2/3 (4)
In the case of 0.3 seconds ≦ T ≦ 0.7 seconds k = 2.0 (5)
When T> 0.7 seconds k = 1.24T ^4/3 (6)
[0028]
From the above formulas (2) to (6), the design horizontal seismic intensity (external force during earthquake) tends to decrease as the natural period of the structure becomes longer.
[0029]
[Table 2]

[0030]
From the analysis results, it is possible to lengthen the natural period of the structure for both Type I and Type II earthquakes, and to reduce the external force during the earthquake (design horizontal seismic intensity).
[0031]
【The invention's effect】
Since the structure of the bridge of the present invention is as described above, the following effects can be obtained.
<I> Improvement in toughness performance of ramen-structured bridges against large-scale earthquakes can be realized at low cost.
<B> Repair and restoration of damaged parts of a bridge after a large-scale earthquake will be relatively easy.
[Brief description of the drawings]
FIG. 1 is a front view of an embodiment of a bridge structure according to the present invention.
FIG. 2 is a longitudinal sectional view of an embodiment of a bridge structure according to the present invention.
FIG. 3A is an explanatory view showing an embodiment of a connecting portion between a bridge pier and a brace material. (B) Explanatory drawing which showed the Example of the connection part of a bridge pier and a brace material. (C) Explanatory drawing which showed the Example of the cross | intersection part of a brace material.
FIG. 4 is a diagram for explaining a four-span continuous ramen model in the bridge axis direction used in the structural analysis, and (a) a model diagram during normal and medium-scale earthquakes. (B) Model diagram during a large-scale earthquake.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Superstructure 11 ... Bridge girder 12 ... Floor slab 2 ... Pier 3 ... Breath material 4 ... Bridge axis perpendicular direction 5 ... Bridge axis direction 71 ... Connection part 72 ... Case Point

Claims (2)

In the structure of a bridge composed of a superstructure consisting of bridge girders and floor slabs and piers,
A plurality of the piers provided at intervals in the bridge axis direction and the bridge axis perpendicular direction; and
The upper work consisting of the bridge girder and the floor slab provided on the upper part of the pier;
A brace material that connects the bridge piers in parallel with each other to form a ramen-structured bridge,
The breath material was ligated into the piers between the bridge axis perpendicular corruption incapable provided for the seismic force of the earth Shinji,
The bridge axis direction of the pier between the breath was ligated into material was arranged to be broken against the seismic force at the time of the earthquake, characterized in that
Bridge structure. A breakable portion that can be damaged when an external force during an earthquake during a large-scale earthquake is applied to the bridge is defined as a connecting portion between the brace material and the bridge pier provided in the bridge axis direction or a grading portion between the brace materials. It is characterized by
The bridge structure according to claim 1.

Images