JPH1181234A - Rigid-frame bridge pier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the collapse of a bridge pier by arranging side plate elements easily generating plastic strain via external force at the time of an earthquake at the side plate sections of beam members. SOLUTION: A portal rigid-frame bridge pier 1 is constituted of foundation sections 2, leg sections 3, a first beam member 5, column sections 7, and a second beam member 9. The first beam member 5 is constituted of an upper plate, a lower plate, and multiple diaphragms installed at the prescribed distances in the longitudinal direction of the beam member 5, and a front side plate and a back side plate are connected to the upper plate, lower plate, and diaphragms by multiple bolts. When an earthquake occurs, the front side plate and back side plate of the beam member 5 are plastically deformed to absorb earthquake energy at a high ratio, thereby the energy absorbed quantity by corner sections 15 and bridge pier base sections 17 can be reduced. The loads applied to the important corner sections 15 and bridge pier base sections 17 at the time of the earthquake are reduced, the earthquake energy can be concentrically absorbed by the plastic deformations of the side plates of the beam member 5, thus the collapse of the bridge pier 1 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bridge pier of a viaduct.

[0002]

2. Description of the Related Art FIG. 6 is a view showing a conventional viaduct ramen pier that may collapse due to a horizontal load during an earthquake. FIG. 6 (a) is a front view and FIG. 6 (b) is a side view. .
In the ramen pier shown in Fig. 6, shear buckling occurred at the center three panels of the side plates (webs) of the beam members in the Great Hanshin Earthquake. Haruyuki, Akinori Mori: Simulation of shear buckling damage of web members of steel pier bridge members due to huge earthquakes, Non-linear Numerical Analysis of Steel Piers and Seismic Design, JSCE / Structural Engineering Committee, Structural Engineering Earthquake Special Committee on Disaster Investigation, pp. 223-230, 1997 5
The month is more quoted.

[0003] In Fig. 6, reference numeral 1 denotes a gate-shaped ramen pier having a two-layer structure. Reference numeral 2 denotes a base portion provided at a predetermined interval on the ground, 3 denotes a pair of legs erected on the base portion 2, and 5 denotes a pair of legs installed on the upper end side of the pair of legs 3 across the two legs 3. The first beam member 7 is a pair of pillars continuously provided on the pair of legs 3, and the second beam member 9 is provided at the upper ends of the pair of pillars 7 over both of the pillars 7. Beam member.
21 and 23 are a first beam member 5 and a second beam member 9 respectively.
It is a road installed in.

FIG. 7 is an explanatory view for explaining the structure of the beam member 5. The structure of the beam member 5 will be described based on FIG. The beam member 5 is formed by welding and joining steel plates in a box shape, and a diaphragm 5c for increasing rigidity is installed inside the beam member 5 at a predetermined interval.

FIG. 8 is an explanatory view for explaining a mechanism of shear buckling when a shear force acts on a steel plate constituting a side plate of a beam member. When the steel plate 25 receives the shear force Q, the microelements 27 inside the plate receive the shear stress τ (FIG. 8A). When τ reaches the shear buckling stress τcr, FIG.
As shown in (b), wrinkles 29 are formed on the steel plate 25 due to displacement in the direction perpendicular to the plate surface. When such wrinkles 29 are formed, FIG.
As shown in (c), the stress state changes from a shear stress to a stress field of oblique tension P in which oblique stress is remarkable. At this time, when the steel plate 25 yields, a large amount of plastic strain occurs in the oblique direction, but since the oblique tension does not decrease, it has been obtained from many experiments that the steel plate 25 can absorb much energy with respect to the shearing force. . (For example, Hachiro Takeda; Inelastic buckling test of plate girder subjected to repeated shearing force
(1), Bulletin of Tsurumai National College of Technology, NO.26, pp.82-95,1991)

FIG. 9 is an explanatory view for explaining a mechanism of shear buckling occurring in a beam member when the conventional pier shown in FIG. 6 receives seismic force. Fig. 9 (a)
When seismic force 31 from the left side is received as shown in
9 receives a bending moment 33 as shown in FIG. Therefore, three panels at the center of the beam member 5 (FIG. 9B)
(A portion surrounded by a broken line) receives the shearing force Q shown in FIG.
An upward wrinkle 29 and an oblique tension P are generated. Conversely, when seismic force is applied from the right side, a wrinkle 35 rising to the left and an oblique tension R are generated as shown in FIG. As a result, an X-shaped residual deformation as shown in FIG. 9E remains on the side plate of the beam member 5. Nakai and Kitada et al. Reported that the reason why the ramen pier in Fig. 6 did not collapse due to the earthquake was that seismic energy was efficiently absorbed by the remarkable plastic deformation of the shear buckled side plates caused by the oblique tension field. Are listed.

[0007]

The above facts are based on the analysis after the Great Hanshin Earthquake. However, in the case of conventional ramen piers, measures to prevent the piers from collapsing when subjected to seismic force are: It was not specifically taken. Therefore, the shear buckling of the side plates and the plastic deformation shown in the above analysis do not absorb all the seismic energy, so in the case of a conventional pier where no consideration is given to energy absorption, etc. Naturally the pier base 17
Excessive bending deformation also occurs at the corner 15 (see FIG. 9),
There was a problem that the pier could fall down.

Further, after the earthquake, the beam member 5 of the ramen pier 1
If the side plate undergoes shear buckling and undergoes plastic deformation, plastic strain due to seismic force is accumulated, so if further plastic deformation occurs, the side plate will crack and cannot absorb seismic energy anymore there is a possibility. Therefore, it is necessary to replace the side plate with a new one after the earthquake. However, since conventional side plates are welded and joined, replacing the side plates requires the construction of a scaffold, gas cutting, welding, etc., so that road traffic on the ground must be shut off for a long time. There was also a problem.

The present invention has been made in order to solve such a problem, and even when seismic energy is received,
The aim is to obtain a ramen pier that will not collapse. It also aims to obtain a ramen pier that can be easily repaired after receiving seismic energy.

[0010]

SUMMARY OF THE INVENTION A rigid frame pier according to the present invention is a single-layer or multilayer structure having a beam member formed by joining steel plates in a box shape, and is provided on a side plate portion of the beam member. ,
Side plate elements where plastic strain easily occurs due to external force during an earthquake.

[0011] Further, the mild steel is used as the side plate element, and the side plate element is detachably mounted on the side plate portion.

Further, the side plate element is disposed at an axial center of the beam member.

[0013]

FIG. 1 is a schematic view of a ramen pier according to an embodiment of the present invention, FIG. 2 is an enlarged view of a beam member surrounded by a broken line in FIG. 1, and FIG. Plan view, FIG. 4
Is a sectional view taken along line AA of FIG. 2, and FIG. 5 is an exploded perspective view of the beam member. In FIG. 1, the same or corresponding parts as those in FIG. 6 showing the conventional example are denoted by the same reference numerals. Reference numeral 1 denotes a gate-shaped ramen pier having a two-layer structure as in the prior art. Reference numeral 2 denotes a base portion provided on the ground at a predetermined distance, 3 denotes a pair of legs erected on the base portion 2, and 5 denotes a pair of legs 3 on the upper end side of the pair of legs 3. The first beam member 7 installed is a pair of pillars continuously provided on the pair of legs 3, and 9 is installed at the upper end of the pair of pillars 7 over the pair of pillars 7. A second beam member.

Next, the structure of the first beam member 5 will be described mainly with reference to FIG. 5 and with reference to FIGS. In FIG. 5, 5a is an upper plate, 5b is a lower plate,
Reference numeral c denotes a plurality of diaphragms installed at a predetermined distance in the longitudinal direction of the beam member 5. Upper plate 5a and lower plate 5
A flange portion 5f for attaching a front side plate 5d and a rear side plate 5e, which will be described later, is formed on both side ends of the b and the side end portion of the diaphragm 5c (see FIG. 4). Many holes are provided.

Reference numerals 5d and 5e denote a front side plate and a back side plate made of a plurality of rectangular steel plates constituting side plates of the beam member. The front side plate 5d and the rear side plate 5e are joined to the upper surface plate 5a, the lower surface plate 5b, and the flange 5f of the diaphragm 5c by a plurality of bolts 11 (see FIGS. 2 and 3). In the present embodiment, in order to realize a side plate capable of efficiently absorbing seismic energy, a conventional yield point of 2,400 is used as the front side plate 5d and the back side plate 5e constituting the side plate.
Instead of ordinary steel of kgf / cm ² , so-called ultra-mild steel having a yield point of about half or less of ordinary steel is used.

When the seismic force is applied to the ramen pier constructed as described above, the front side plate 5d and the rear side plate 5d of the beam member 5 are operated by the mechanism described with reference to FIG.
e plastically deforms and absorbs seismic energy at a high rate. For this reason, it is possible to reduce the amount of energy absorbed by the corners 15 and the pier bases 17 (see FIG. 1), which are structurally important and are not easily replaced after an earthquake. That is, the burden on the important corners 15 and the pier base 17 during an earthquake can be reduced, and seismic energy can be intensively absorbed by plastic deformation of the side plate of the beam member 5.

After the earthquake, the bolts 11 may be promptly removed, and the front side plate 5d and the rear side plate 5e having the residual deformation may be replaced with new side plates. At this time, since the front side plate 5d and the rear side plate 5e are not welded as in the conventional example, the work can be performed quickly and the period during which traffic is cut off can be shortened.

In the above-described embodiment, an example in which extremely mild steel is used as the front side plate 5d and the back side plate 5e has been described. However, even if the steel material has a higher yield point than the extremely mild steel, it yields more than the ordinary steel. If the member has a low point, a certain effect can be obtained.

Further, in the above-described embodiment, a member having a lower yield point than ultra-mild steel or normal steel is used for all side plates of the beam member 5, but the beam member 5 having the largest plastic deformation is used. A member having a lower yield point than the mild steel or ordinary steel may be used only in the central portion of the steel. In this way, the absorption of seismic energy can be concentrated and the number of replacements after the earthquake can be reduced,
The replacement work can be performed more quickly.

[0020]

As described above, according to the present invention, since the side plate element which easily generates a plastic strain due to the external force at the time of the earthquake is arranged on the side plate portion constituting the beam member, the side plate element has a high ratio of seismic energy. It is possible to reduce the amount of energy absorbed by corners and pier bases, which are structurally important and are not easily replaced after an earthquake, and can prevent collapse of piers.

Further, since extremely mild steel is used as the side plate element, energy can be absorbed more efficiently. In addition, since the side plate elements are detachably mounted on the side plate portions, it is possible to quickly replace the side plate elements having residual deformation due to shear buckling after an earthquake, thereby shortening a period in which traffic is interrupted.

Furthermore, since the side plate elements are arranged at the axial center of the beam member, the absorption of seismic energy can be concentrated, and the number of replacements after the earthquake can be reduced, so that the replacement work can be performed more quickly. It can be carried out.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a ramen pier according to an embodiment of the present invention.

FIG. 2 is an enlarged front view showing a main part of the embodiment of the present invention shown in FIG.

FIG. 3 is an enlarged plan view showing a main part of the embodiment of the present invention shown in FIG. 1;

FIG. 4 is a sectional view taken along the line AA in FIG. 2;

FIG. 5 is an exploded perspective view of a main part of the embodiment of the present invention shown in FIG.

FIG. 6 is an explanatory view of a conventional ramen pier.

FIG. 7 is an explanatory view illustrating a structure of a beam of a conventional ramen pier.

FIG. 8 is an explanatory view of a mechanism of shear buckling of a plate material.

FIG. 9 is an explanatory view of a mechanism of shear buckling of a side plate in a beam member of a rigid frame pier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ramen pier 3 Leg 5 1st beam member 5d Front side plate 5e Back side plate 9 2nd beam member 11 Bolt 15 Corner 17 Bridge pier base

Claims (3)

[Claims] 1. A single-layer or multi-layer rigid-frame pier having a beam member formed by joining steel plates in a box shape, wherein plastic strain is easily generated in a side plate portion of the beam member due to an external force during an earthquake. A ramen pier with a variety of side plate elements. 2. The ramen pier according to claim 1, wherein extremely soft steel is used as the side plate element, and the side plate element is detachably mounted on the side plate portion. 3. The rigid-frame pier according to claim 1, wherein the side plate element is disposed at an axial center of the beam member.