JPH05302397A - Reinforcing structure of beam - Google Patents

Abstract

PURPOSE:To remarkably increase the torsion rigidity of a beam and obtain a reasonable reinforcing structure in which the lateral buckling is hardly brought in the beam, by devising the shape and the arrangement of stiffeners in the beam having flanges at the upper and lower parts and also an opening in the section. CONSTITUTION:Vertical stiffeners 4 are provided every specified distance on the web 2 of a H-shaped steel beam 1. The stiffener is made of a semi-circular steel pipe and jointed to the web of beam 1 to form a closed section. As a result, the torsion rigidity is remarkably increased. The distance of respective stiffeners is made narrower at the end of the member and gradually wider in the middle. The stiffeners 4 are jointed to the web 2 by welding or so. The upper and lower ends of the stiffeners 4 are preferably jointed to the flanges 3.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an H-shaped steel beam, a channel steel beam, and an I-shaped steel beam.
The present invention relates to a reinforcing structure for improving the torsional rigidity of a beam having flanges above and below a web, such as a plate girder having a cross section, and preventing lateral buckling of the beam.

[0002]

2. Description of the Related Art In columns or beams constituting a frame of a structure, or piles used as a foundation, stiffeners or reinforcing ribs are provided at portions receiving a large bending moment to stiffen or buckle as a member. When there is a risk, it is common practice to provide reinforcing ribs or the like to increase the rigidity. In such conventional buckling stiffening by the reinforcing ribs, the reinforcing ribs are provided at required intervals and the buckling length is shortened to improve the strength against buckling.

[0003]

The conventional buckling stiffening is designed mainly for the bending moment acting on the member, and the torsional rigidity has not been studied so much.
That is, the conventionally used plate-shaped stiffener is
Although it contributes to the improvement of bending rigidity, it hardly contributes to twisting, and in the case of an open cross-section member such as an H-shaped steel beam or an I-shaped plate girder having a small torsional rigidity, the cross-sectional dimension and Depending on the load conditions, there is a risk of lateral buckling due to bending moments.

In the above case, the present invention uses a stiffener that forms a closed cross section together with the beam web.
The purpose of the present invention is to provide a rational beam reinforcement structure in which the torsional rigidity of the beam is significantly improved and lateral buckling is less likely to occur by devising its arrangement.

[0005]

According to the present invention, a stiffener made of a half steel pipe or the like is vertically attached to a web such as an H-shaped steel beam so that a closed cross section is formed by the web and the stiffener. ..

The stiffener of the present invention functions similarly to the conventional plate-shaped stiffener with respect to the bending moment acting on the beam, and improves the bending rigidity and shortens the buckling length according to its cross section. In addition, by forming the closed cross section, the torsional rigidity of the beam member can be significantly improved, as will be described in detail in the section of action.

Beams to which the present invention is applied include H-shaped steel beams, grooved steel beams, I-shaped plate girders, and other beams having flanges above and below the web, and the material is not limited to steel. Instead, it can be applied to a beam of aluminum alloy, for example.

The stiffener may have a semi-circular cross section such as a half-section steel pipe, a mountain cross section (angle, etc.), a rectangular cross section (channel steel, hat steel, etc.). Provide on both sides or one side.

The upper and lower ends of the stiffener may be in close contact with the beam flange or separated from each other depending on application conditions. Note that the vertical direction is not necessarily limited to the vertical direction and may include an oblique direction, and may be arranged in a truss shape at predetermined intervals.

[0010]

By providing a closed cross-section element in the intermediate portion of the member for an H-section beam having a small torsional rigidity such as an H-section steel beam, the torsional rigidity can be greatly increased and lateral buckling can be made difficult.

In the present invention, a longitudinal stiffener forming a closed cross section is used together with the beam web, but twisting about the material axis (torsion moment T) as shown in FIG.
Corresponding to twisting about the axis perpendicular to it through the flange 3 (torsion moment T '), the stiffener 4 arranged in the vertical direction is directly involved in the torsional rigidity of the beam 1 and is close to the case where it is arranged in the material axis direction. Has a torsional reinforcement effect.

Further, in many cases, a part of the cross section of the beam is constrained by a purlin, a slab or the like against lateral deformation. Even in this case, if the opposite flange receives a bending moment that causes compression, there is a risk of lateral buckling. On the other hand, as shown in FIG. 3, if the vertical stiffener 4 according to the present invention is used, the restraint of the slab 12 and the like is also transmitted to the lower flange 3b side, and the effect of lateral buckling is exhibited. Also, with a closed cross section,
The effect of increasing the torsional rigidity is that the compression flange (lower flange 3b) between the stiffeners 4 arranged at a predetermined interval is deformed in the lateral direction, and the stiffener 4 position is constrained to be close to the end fixing so that the lateral seat Makes it hard to give in.

Further, in the case of a beam having a thin web plate,
For the buckling of the web plate, the stiffener of the strip with a small torsional rigidity is a pin-like boundary condition, whereas the stiffener with a closed cross section has an extremely large torsional rigidity and is a boundary condition close to fixed, which is extremely advantageous. Is.

In a plate girder or the like having a web thickness smaller than that of the beam, the tension field balances due to wrinkles diagonally after the local buckling of the web. In this case, the fact that the vertical stiffener corresponding to the truss bundle material has a closed cross section greatly contributes to the subsequent stability.

Further, it is routine to provide a through hole for piping in the beam, but reinforcement for that is troublesome. If the vertical stiffeners according to the present invention are provided at certain intervals in advance, it is possible to make holes to some extent without reinforcement. Considering after the through hole is provided, the closed section stiffener is effective.

[0016]

EXAMPLES Next, the illustrated examples will be described.

FIG. 1 shows an embodiment of the present invention.
This is an example in which the web 2 of the H-shaped steel beam 1 is provided with stiffeners 4 in the vertical direction made of a half-split steel pipe at predetermined intervals. The stiffeners 4 may be arranged at equal intervals, but in the example of FIG.
Shorten the gap at the material end where the bending moment of
The intervals are gradually widened toward the center. Further, although the stiffeners 4 having the same size are used in the present embodiment, for example, the stiffeners 4 having different cross-sectional sizes at the end portion and the central portion may be used.

It is desirable that the stiffener 4 is welded to the web 2 and the flange 3 so as to be in close contact with each other as shown in the figure, but the stiffener 4 can be joined to the flange 3 only at the upper or lower side, or both can be separated. .. Examples of the joining method include continuous welding, spot welding, bolt joining, and joining methods using an adhesive, but are not particularly limited.

FIGS. 4 (a) and 4 (b) show another embodiment of the present invention. In this embodiment, stiffeners 5 made of hat-shaped steel are alternately attached to the web 2 of the beam 1. ..
In the drawing, reference numeral 6 denotes a through hole for piping or the like, and stiffeners 5 in the vertical direction are provided at predetermined intervals, so that the decrease in the yield strength of the web 2 is compensated by the stiffener 5.

FIGS. 5 (a) and 5 (b) show still another embodiment of the present invention, which is an example in which the stiffener 7 made of an angle is arranged not like the vertical direction but obliquely like a truss.
Improving the torsional rigidity of the beam 1 can be considered in the same manner as described in the section of action based on FIG.

[0021]

EFFECTS OF THE INVENTION By providing a stiffener in the vertical direction that forms a closed cross section together with a web of a beam, the torsional rigidity of the beam is significantly improved, and a large reinforcing effect is obtained against lateral buckling due to a bending moment acting on the beam. give.

At the same time, the stiffener also functions as a normal longitudinal stiffener for bending moments acting on the beam.

Particularly, a beam having a small web plate thickness is advantageous because the torsional rigidity is extremely large and the stiffener position becomes a boundary condition close to fixed.

In a plate girder or the like having a small web thickness, the stiffener forming a closed cross section after locally buckling the web functions as a truss bundle material or diagonal material and greatly contributes to the stability thereafter. ..

By providing the vertical stiffeners according to the present invention at a predetermined interval on the web of beams, it is effective for reinforcing the vicinity of the through holes even when the through holes are provided in the web.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is an explanatory view showing the operation of the stiffener of the present invention.

FIG. 3 is an explanatory diagram showing an operation when an upper flange of an H-shaped steel beam is restrained by a slab.

FIG. 4 shows another embodiment of the present invention, in which (a) is a front view and (b) is a horizontal sectional view.

FIG. 5 shows still another embodiment of the present invention,
(a) is a front view and (b) is a horizontal sectional view.

[Explanation of symbols]

1 ... Beam, 2 ... Web, 3 ... Flange, 4 ... Stiffener (half-section steel pipe), 5 ... Stiffener (hat shaped steel) 6 ... Through hole, 7 ... Stiffener (angle), 11 ... Pillar, 12
… Slab,

Claims (4)

[Claims] 1. A reinforcing structure for a beam, wherein a stiffener in a longitudinal direction is attached to the web of a beam having flanges above and below the web, the stiffener providing a predetermined torsional rigidity together with the web. 2. The beam reinforcing structure according to claim 1, wherein the stiffener is a half steel pipe. 3. The beam reinforcing structure according to claim 1, wherein upper and lower ends of the stiffener are in close contact with the flange. 4. The beam reinforcing structure according to claim 1, 2 or 3, wherein the beam is an H-shaped steel beam.