JP3551095B2 - Ramen pier - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a viaduct ramen pier.
[0002]
[Prior art]
FIG. 10 is a diagram illustrating a conventional viaduct ramen pier that may collapse due to a horizontal load during an earthquake. FIG. 10 (a) is a front view, and FIG. 10 (b) is a side view. The ramen piers shown here were caused by shear buckling of the three center panels of the side plates (webs) of the cross beams in the Great Hanshin Earthquake. Papers: Hiroshi Nakai, Toshiyuki Kitada, Keiji Nishioka, Masato Kano, Haruyuki Sakota , Akinori Mori: Simulation of shear buckling damage of steel ramen pier cross beams due to massive earthquake, Non-linear numerical analysis of steel pier and seismic design, JSCE / Structural Engineering Committee, Structural Engineering Earthquake Investigation Special Subcommittee, pp. 223-230, May 1997.
[0003]
In FIG. 10, reference numeral 1 denotes a portal-shaped ramen pier having a two-layer structure. 2 is a base part provided at a predetermined interval on the ground, 3 is a pair of pillars erected on the foundation 2, 5 is installed over both pillars 3 on the upper end side of the pair of pillars 3. The first cross beam 7 is a pair of pillars provided continuously to the pair of pillars 3, and the second cross beam 9 is provided at the upper end of the pair of pillars 7 across both of the pillars 7. It is a cross beam. Reference numerals 21 and 23 denote bridge girders installed on the first cross beam 5 and the second cross beam 9, respectively.
[0004]
FIG. 11 is an enlarged view of a central portion of the first cross beam 5 of the ramen pier 1 shown in FIG. As shown in FIG. 11, the first cross beam 5 is formed by welding and joining a plurality of steel plates to a BOX shape (side plate 5a, top plate 5b, bottom plate 5c), and has therein a diaphragm 5d for increasing rigidity. Ribs (not shown) are appropriately provided.
[0005]
FIG. 12 is an explanatory diagram for explaining the mechanism of shear buckling occurring in the cross beam when the conventional rigid frame pier 1 shown in FIG. 10 receives seismic force. When the ramen pier 1 receives the seismic force 31 from the left side as shown in FIG. 12A, a bending moment 33 as shown in FIG. 12B acts on the end of the first cross beam 5. . Since the bending moment 33 causes a shear force Q to act on the first cross beam 5 as shown in FIG. 12C, the oblique tension P accompanying the shear buckling 29 (oblique wrinkles) is applied to the side plate 5a (web). As a result, plastic deformation occurs in the oblique tension direction.
[0006]
When the seismic force acts from the right side opposite to that of FIG. 12 (a), a diagonal tension field as shown in FIG. 12 (d) is obtained. Such an X-shaped wrinkle results.
Nakai et al. Concluded that the plastic deformation associated with shear buckling effectively absorbed the seismic energy, thereby mitigating the deformation of the pier base 17 and corner 15 and the ramen pier did not collapse. .
The effective energy absorption characteristics of the side plate (web) subjected to the shearing have been experimentally confirmed for a long time (for example, Basler, K .: Strength of plate girder's insear, Journal of the Structure Division, Proceeding Atomization). Society of Civil Engineers, ST7, pp 151-180, October, 1961).
[0007]
[Problems to be solved by the invention]
Certainly, since the deformability of the cross beam with respect to the repeated shearing force is extremely excellent, high energy absorption capacity is expected. However, even if high energy absorption is expected, it may not be large enough to absorb the seismic energy supplied to the entire ramen pier. This is because the members such as the ramen piers are a combination of thin plates, and the energy absorption capacity of the thin plates is limited.
Therefore, in the conventional ramen pier, the seismic energy cannot be sufficiently absorbed, and the base of the pier is damaged. If the damage is large, there is a risk of collapse.
[0008]
In addition, if the shear deformation is excessively concentrated on one part of the cross beam, that part may be damaged, and may not fulfill its original role of supporting the bridge girders 21 and 23. In such a case, the ramen piers cannot be provisionally used after the earthquake, which may cause serious obstacles to society in situations where restoration is urgent.
[0009]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a ramen pier that can safely support a bridge girder after an earthquake and can be temporarily used.
[0010]
[Means for Solving the Problems]
The ramen pier according to the present invention, in which the cross beam is supported by the upper end portion of the column material, a shear damper that is installed at the upper end portion of the column material and supports the cross beam, and is installed around the shear type damper. A web material that resists shearing force, and a flange material that is installed around the shear type damper and that resists bending moment.
[0011]
Further, the mild mild steel having a low yield point is used for the web material.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is an explanatory view of one embodiment of the present invention, and schematically shows the front of a ramen pier. 2 is an enlarged view of a portion A surrounded by a circle in FIG. 1, FIG. 3 is a side view of the portion A, FIG. 4 is a cross-sectional view taken along line AA in FIG. 2, and FIG. 5 is a perspective view. . In the figure, the same or corresponding parts as those in FIG. 10 showing the conventional example are denoted by the same reference numerals.
[0013]
First, referring to FIG. 1, the overall configuration is outlined. Reference numeral 1 denotes a gate-shaped ramen pier having a single-layer structure. 2 is a base part provided at a predetermined interval on the ground, 3 is a pair of pillars erected on the base part 2, 5 is installed on both pillars 3 at the upper end of the pair of pillars 3. Reference numeral 21 denotes a bridge girder installed on the cross beam 5.
[0014]
Next, the structure of the joint between the column member 5 and the cross beam 5 will be described with reference to FIGS.
Reference numeral 41 denotes a shear damper installed at the upper end of the pillar 3, and the cross beam 5 is installed at the upper end of the pillar 3 via the shear damper 41.
The shear type damper is a type of a damper that absorbs energy by shear deformation, and is made of various materials such as rubber or a laminated structure of rubber and lead.
[0015]
Reference numeral 43 denotes a web material made of ultra-mild steel having a low yield point, which is installed on the front and rear surfaces of the ramen pier 1 over the column and beam members. Reference numeral 45 denotes a normal material which is installed over the column and beam materials on both side surfaces. It is a flange material made of steel or high-tensile steel.
The web material 43 remains elastic only in a plate-type small earthquake (level 1 earthquake) that occurs relatively frequently and does not undergo plastic deformation, but rarely occurs in a direct-type large earthquake (level 2 earthquake). Is set to such a thickness that shear yield occurs before other parts.
[0016]
As described above, the joint between the column member 3 and the cross beam 5 is constituted by the shear damper 41 installed at the upper end of the column member 3 and the web member 43 and the flange member 45 installed so as to surround the same. I have.
[0017]
Next, the operation of the present embodiment configured as described above will be described.
When a level 1 seismic force 47 acts on the ramen pier 1 from the left in FIG. 6, the web member 43 resists the seismic force 45 by shearing, and the flange member 45 resists the seismic force 47 by bending. In this case, the web material 43 remains in the elastic range and does not plastically deform. The bending moment diagram in this case is as shown in FIG. 6, and the bending moment acting on the base 17 is reduced. This is because the periphery of the shear damper 41 is surrounded by the web member 43 and the flange member 45, so that these members resist the seismic force 47 by shearing and bending.
[0018]
In this regard, when the periphery of the shear damper 41 is not surrounded by the web member 43 and the flange member 45, the cross beam 4 and the column member 3 are joined only by the shear damper 41, and Since the resistance cannot be obtained, the bending moment is as shown in FIG. 7, and a large bending moment acts on the base 17.
[0019]
As shown in FIG. 8, when a level 2 seismic force 49 is applied, the ultra-mild steel web 43 having a low yield point is sheared and yielded earlier than other portions, and the web 43 is shear-deformed as a plate. In addition, the shear-type damper 41 also undergoes shear deformation.
The deformation caused by the seismic force 49 of level 2 is such that the extremely mild steel web material 43 becomes a fuse and the deformation progresses, and energy is absorbed by the plastic deformation of the web material 43 and the deformation of the shear damper 41. Plastic deformation can be suppressed.
[0020]
As shown in FIG. 9, the shear deformation may remain after the earthquake, but even in such a case, the damage to the cross beam 5 itself is suppressed, and the cross beam 5 is a sound column in which the base 17 is not damaged. Since it is supported by the material 3 via the shear damper 41, it can be temporarily used as a ramen pier.
Further, even when the web member 43 and the flange member 45 are severely damaged, since the shear type damper 41 supports the cross beam 5, the web member 43 and the flange member 45 surrounding the shear type damper 41 are gas-cut and the shear type damper 41 is cut. If the shear deformation of the damper 41 is returned by a jack or the like and is surrounded by a new web material and a flange material, the damper 41 can be returned to the original state, and it can be prepared for a large earthquake again.
[0021]
As described above, according to the present embodiment, the joint between the column member 3 and the cross beam 5 is composed of the shear damper, the ultra mild steel web material, and the ordinary steel flange material, and the deformation is concentrated on this portion. Since the energy is absorbed, the soundness of the entire ramen pier can be maintained without giving excessive plastic deformation to the column members 3 and the cross beams 5, which are the main structures of the ramen pier 1.
[0022]
Note that, in the present embodiment, an example in which extremely mild steel is used as the web material has been described, but the present invention is not limited to this, and a member having a high energy absorbing ability can be used similarly to extremely mild steel. Needless to say, it is also possible to use ordinary steel having lower energy absorption than ultra mild steel.
[0023]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
[0024]
A shear damper installed at the upper end of the column material to support the cross beam; a web material installed around the shear damper to resist shearing force; and a bending material installed around the shear type damper to reduce bending moment. With the provision of a flange material that resists, the shear-type damper, the flange material, and the flange material bear the bending moment and absorb energy, so the base moment is reduced in the event of a level 1 earthquake motion. And in the event of a level 2 seismic motion, plastic deformation of the base and cross beams can be reduced.
As a result, even if there is a level 2 seismic motion, the cross beam can maintain its soundness, can prevent damage to the base of the pillar, and can be temporarily used as a ramen pier.
Further, even when the shear-deformed portion is severely damaged, since the cross beam is supported by the shear-type damper, the web or flange surrounding the shear-type damper can be easily replaced, and quick recovery can be performed.
[0025]
Further, since the mild mild steel having a low yield point is used for the web material, the seismic energy absorbing capacity of the rigid frame pier can be more efficiently increased.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of one embodiment of the present invention.
FIG. 2 is an enlarged view of a portion A in FIG.
FIG. 3 is a side view of a portion A in FIG. 1;
FIG. 4 is a sectional view taken along line AA of FIG. 2;
FIG. 5 is a perspective view of a portion A in FIG. 1;
FIG. 6 is a bending moment diagram according to the embodiment of the present invention.
FIG. 7 is a bending moment diagram in a case where only a shear type damper is used to join a column member and a cross beam.
FIG. 8 is an explanatory diagram of the operation of the embodiment of the present invention.
FIG. 9 is an explanatory diagram of a state in which residual deformation after an earthquake remains in one embodiment of the present invention.
FIG. 10 is an explanatory view of a conventional ramen pier.
FIG. 11 is an explanatory view illustrating the structure of a beam of a conventional ramen pier.
FIG. 12 is an explanatory view of a mechanism of shear buckling of a side plate in a cross beam of a rigid frame pier.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ramen pier 3 Column 5 Cross beam 41 Shear type damper 43 Web 45 Flange

Claims (2)

In the ramen pier supporting the cross beam at the upper end of the column,
A shear damper installed at the upper end of the column material and supporting the cross beam,
A web material installed around the shear damper to resist shearing force,
And a flange member installed around the shear type damper to resist bending moment. 2. The rigid-frame pier according to claim 1, wherein an ultra-mild steel having a low yield point is used for the web material.

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