JP6934323B2 - Beam buckling suppression structure - Google Patents

Description

The present invention relates to a beam buckling suppression structure.

Generally, in the event of a fire or the like, a metal beam such as a steel beam expands and expands thermally as the temperature rises. As a result, stress may be generated in structural members such as columns joined to the ends of the beam, buckling such as local buckling may occur in the beam, and the load bearing capacity of the beam itself may decrease.

In order to solve this problem, for example, in Patent Document 1, a buckling guide portion is provided on the steel beam, and the steel beam is buckled by the buckling guide portion to absorb the extension of the steel beam to absorb the extension of the steel beam. A beam-column structure that reduces the stress acting on a column joined to an end is disclosed. However, in the column-beam structure of Patent Document 1, it was not possible to suppress the buckling of the steel frame beam at the time of fire and the decrease in proof stress due to the buckling.

Japanese Unexamined Patent Publication No. 2014-231726

In view of the above facts, an object of the present invention is to provide a beam buckling suppression structure capable of suppressing buckling such as local buckling due to thermal expansion of the beam. Another object of the present invention is to provide a beam buckling suppression structure capable of suppressing compression buckling of a beam in the event of a fire or lateral buckling accompanied by bending or twisting by shortening the buckling length. ..

The beam buckling suppression structure according to the first aspect is a metal beam having an end joined to a structural member, a beam length of D (mm), a beam length of L (mm), and a beam width of B (mm). And a buckling suppressing member provided on the beam, which has a larger thermal capacity than the beam and suppresses buckling due to thermal expansion of the beam, and the buckling suppressing member is L / 3 from the end of the beam. It is provided at a position within (mm) and at a position separated from the end of the beam by D (mm) or more.

In a metal beam whose end is joined to a structural member, the beam length is D (mm), the beam length is L (mm), and the beam width is B (mm). Local buckling is likely to occur at a position within L / 3 (mm) from the end of the beam and at a position more than D (mm) away from the end of the beam.

Here, according to the above configuration, a buckling suppressing member having a larger heat capacity than the beam is provided at a position within L / 3 (mm) from the end of the beam and at a position D (mm) or more away from the end of the beam. Since it is provided, the buckling suppressing member can suppress local buckling due to thermal expansion of the beam.

The beam buckling suppression structure according to the second aspect is the buckling suppression structure of the beam according to the first aspect, and the width of the buckling suppression member along the material axis direction of the beam is B (mm). That is all.

In general, local buckling of a beam tends to occur in a range of about 1 to 2 times the beam width B. Here, according to the above configuration, by setting the width of the buckling suppressing member along the material axis direction of the beam to be equal to or larger than the beam width B, the buckling suppressing member can cover the range in which the beam is likely to be locally buckled. ..

The beam buckling suppression structure according to the third aspect is a beam buckling suppression structure according to the first or second aspect, and the buckling suppression member is concrete.

According to the above configuration, by forming the buckling suppressing member with concrete having a higher rigidity than that of a metal beam, local buckling due to thermal expansion of the beam can be efficiently suppressed. Further, for example, when a concrete slab is placed on the upper part of the beam, a buckling suppressing member can be formed at the same time as the construction of the slab.

According to the present invention, buckling such as local buckling due to thermal expansion of the beam can be suppressed. In addition, the buckling length can be shortened, and compression buckling of the beam at the time of fire or lateral buckling accompanied by bending or twisting can be suppressed.

It is an elevation view of the column beam frame which shows the buckling suppression structure of a beam in 1st Embodiment. FIG. 5 is a cross-sectional view taken along the line AA in FIG. (A) is a partially enlarged view of a column-beam frame showing a beam buckling suppression structure in the second embodiment, and (B) is a sectional view taken along line CC in (A). (A) is a cross-sectional view showing a beam before the buckling suppressing member is provided in the modified example, and (B) is a cross-sectional view showing the beam after the buckling suppressing member is provided.

<First Embodiment>
Hereinafter, the buckling suppression structure of the beam according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

(composition)
As shown in FIGS. 1 and 2, the beam 10 of the present embodiment is made of, for example, H-shaped steel having an H-shaped cross section. The beam 10 may be a roll H formed by roll forming, or may be a build H assembled by welding the upper flange 10A, the lower flange 10B, and the web 10C.

Further, the cross section of the beam 10 is not limited to the H shape, and may be a T shape, an L shape, a C shape, or the like. Further, the material of the beam 10 is not limited to steel, and may be made of other metals such as stainless steel and aluminum.

The beam 10 has a beam length of D (mm), a beam length of L (mm), and a beam width of B (mm). It is joined (rigidly joined) to each of the columns 12 as an example. Further, for example, a concrete slab 14 is constructed on the upper part of the beam 10.

The web 10C of the beam 10 is provided with concrete members 16A and 16B as buckling suppressing members having a heat capacity larger than that of the steel constituting the beam 10. One concrete member 16A is provided at a position within L / 3 (mm) from one end of the beam 10 joined to the pillar 12 and at a position D (mm) or more away from one end of the beam 10. The other concrete member 16B is provided at a position within L / 3 (mm) from the other end of the beam 10 joined to the column 12 and at a position D (mm) or more away from the other end of the beam 10. There is.

Further, the concrete members 16A and 16B have a width of B (mm) along the material axis direction of the beam 10. As shown in FIG. 2, the concrete member 16B (and the concrete member 16A) are provided on both sides of the web 10C of the beam 10.

As a method of providing the concrete members 16A and 16B on the beam 10, first, a plurality of studs 18 are welded in advance on the upper surface of the lower flange 10B of the beam 10 and both sides of the web 10C. Then, a formwork for a slab (not shown) is arranged with a gap with respect to the upper flange 10A of the beam 10. Reinforcing bars for reinforcing slabs (not shown) may be arranged in the slab formwork.

Then, a formwork for a buckling suppressing member (not shown) is arranged so as to connect the formwork for the slab and the lower flange 10B of the beam 10, and concrete is poured into the formwork for the slab. At this time, concrete flows into the formwork for the buckling suppressing member from the gap between the upper flange 10A of the beam 10 and the formwork for the slab, and the concrete members 16A and 16B integrated with the slab 14 are formed.

(Action and effect)
Generally, in a beam 10 having a concrete slab 14 constructed on the upper portion as in the present embodiment, when the temperature of the beam 10 rises at the time of a fire, the beam 10 thermally expands and expands, so that the beam 10 is expanded. Local buckling occurs. This local buckling is particularly likely to occur at a position within L / 3 (mm) from the end of the beam 10 fixed to the column 12 and at a position D (mm) or more away from the end of the beam.

Here, according to the present embodiment, the concrete members 16A and 16B are provided at a position within L / 3 (mm) from the end of the beam 10 and at a position D (mm) or more away from the end of the beam 10. Has been done.

Since the concrete members 16A and 16B have a larger heat capacity than the steel constituting the beam 10, the yield strength of the concrete members 16A and 16B is unlikely to decrease due to the heat of a fire. Therefore, it is possible to suppress local buckling due to thermal expansion of the portion of the beam 10 where the concrete members 16A and 16B are provided, that is, a portion where local buckling is likely to occur, and a decrease in proof stress and a decrease in rigidity due to local buckling. ..

Further, in general, the range in which local buckling occurs in the beam 10, that is, the buckling width tends to be about 1 to 2 times the beam width B. Here, according to the present embodiment, since the width of the concrete members 16A and 16B along the material axis direction of the beam 10 is equal to or larger than the beam width B, the concrete members 16A and 16B are likely to cause local buckling of the beam 10. The area can be covered.

Further, according to the present embodiment, since the concrete members 16A and 16B having higher rigidity than the steel constituting the beam 10 are used as the buckling suppressing member, the local buckling due to the thermal expansion of the beam 10 is efficiently suppressed. be able to. Further, since the concrete members 16A and 16B can be formed on the beam 10 at the same time as the construction of the slab 14, the buckling suppressing member can be easily provided on the beam 10 at the site.

Further, according to the present embodiment, the concrete members 16A and 16B and the beam 10 are tightly connected by the stud 18 welded to the beam 10. Therefore, the concrete members 16A and 16B further suppress the local buckling of the lower flange 10B and the web 10C of the beam 10 in the out-of-plane direction as compared with the configuration in which the concrete members 16A and 16B and the beam 10 are not tightly connected. can do.

<Second Embodiment>
Hereinafter, the buckling suppression structure of the beam according to the second embodiment of the present invention will be described with reference to FIGS. 3 (A) and 3 (B). The same configuration as that of the first embodiment will be described by adding the same reference numerals and omitting the description, focusing on the differences.

(composition)
As shown in FIG. 3A, the beam 20 of the present embodiment is a protruding beam in which one end in the timber axial direction is joined (rigidly joined) to the column 12. Further, the web 20C of the beam 20 is provided with refractory coated ribs 22A and 22B as buckling suppressing members having a heat capacity larger than that of the steel constituting the beam 20.

The fireproof coating ribs 22A and 22B are composed of, for example, ribs 24A and 24B made of the same steel plate as the beam 20, and fireproof coating members 26 coated on the outer surfaces of the ribs 24A and 24B, respectively.

The refractory coated ribs 22A and 22B (ribs 24A and 24B) are welded to the web 20C of the beam 20, respectively, and are located within L / 3 (mm) from one end of the beam 20 joined to the column 12 and the beam. They are provided at positions separated from one end of 20 by D (mm) or more. Further, as shown in FIG. 3B, the fireproof coating ribs 22B (and the fireproof coating ribs 22A) are provided on both sides of the web 20C of the beam 20.

In the present embodiment, two fireproof coating ribs 22A and 22B are provided on one side of the web 20C of the beam 20, but only one or three or more fireproof coating ribs 22A and 22B are provided on the beam 20. It may have been. Further, the materials of the ribs 24A and 24B are not limited to steel, and may be made of other metals.

Further, the outer surfaces of the beam 20 and the fireproof coating member 26 are covered with a fireproof coating member 28 having a predetermined thickness required by law. In the present embodiment, the fireproof coating member 28 is made of the same material as the fireproof coating member 26 that covers the ribs 24A and 24B, but may be made of a different material.

As a method of coating the fireproof coating members 26 and 28, a method of spraying rock wool, a method of wrapping a dry coating member whose main material is inorganic fiber felt, a method of applying fireproof paint, and a board-shaped coating material are used. Examples include a method of mounting.

As a method of providing the fireproof coating ribs 22A and 22B and the fireproof coating member 28 on the beam 20, first, the ribs 24A and 24B are welded to the beam 20, and the outer surfaces of the ribs 24A and 24B are coated with the fireproof coating member 26. By coating the outer surfaces of the beam 20 and the fireproof coating member 26 with the fireproof coating member 28 at the same time as the coating of the fireproof coating member 26 or after the coating of the fireproof coating member 26, the beam 20 is coated with the fireproof coating ribs 22A and 22B and the fireproof coating. A member 28 is provided.

(Action and effect)
According to the present embodiment, the fireproof coating ribs 22A and 22B are provided at a position within L / 3 (mm) from the end of the beam 20 and at a position D (mm) or more away from the end of the beam 20. There is.

Since the fireproof coating ribs 22A and 22B have a larger heat capacity than the steel constituting the beam 20, the proof stress is unlikely to decrease due to the heat of a fire. Therefore, it is possible to suppress local buckling due to thermal expansion of the portion of the beam 20 where the fireproof coating ribs 22A and 22B are provided, that is, a portion where local buckling is likely to occur, and a decrease in proof stress and a decrease in rigidity due to local buckling. can.

Further, according to the present embodiment, since the outer surface of the beam 20 is covered with the fireproof coating member 28, it is possible to suppress the temperature rise of the entire beam 20. In particular, the outer surfaces of the ribs 24A and 24B are covered with the refractory coating members 26 and 28, so that the coating thickness is thicker than the other parts of the beam 20. As a result, it is possible to efficiently suppress the temperature rise of the portion of the beam 20 where local buckling is likely to occur.

<Other Embodiments>
Although the first and second embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention.

For example, in the first embodiment, concrete members 16A and 16B as buckling suppressing members are formed by pouring concrete into the formwork at the site. However, as shown in FIGS. 4 (A) and 4 (B), the buckling suppressing member may be configured by a block 32 made of precast concrete manufactured in advance at a factory or the like.

Specifically, as shown in FIG. 4A, a through hole 34 is formed in each of the pair of blocks 32, and a through hole 36 is also formed at a corresponding position of the web 30C of the beam 30. There is. As shown in FIG. 4B, the block 32 can be fixed to the beam 30 by inserting the bolt 38 into the through holes 34 and 36. As a result, on-site work can be reduced as compared with the case of forming the concrete members 16A and 16B.

Further, in the first embodiment, the buckling suppressing member is composed of concrete members 16A and 16B, and in the second embodiment, the buckling suppressing member is composed of fireproof coating ribs 22A and 22B. However, the buckling suppressing member only needs to have a larger heat capacity than the beams 10 and 20 and a rigidity sufficient to suppress the local buckling of the beams 10 and 20, and is composed of, for example, mortar. May be good.

Further, in the first and second embodiments, concrete members 16A and 16B and fireproof coating ribs 22A and 22B as buckling suppressing members are provided on both sides of the webs 10C and 20C of the beams 10 and 20, but the web 10C , 20C may be provided on only one side. By providing a buckling suppressing member on at least one side of the webs 10C and 20C, it is possible to suppress local buckling due to thermal expansion of the beams 10 and 20 as compared with a configuration in which the buckling suppressing member is not provided. can.

Further, the shape and size of the buckling suppressing member are not limited to the above-described embodiment. For example, the buckling suppressing member provided on the webs 10C and 20C of the beams 10 and 20 is extended downward to be under the beams 10 and 20. It may be configured to cover the lower surface of the flange 10B.

Further, the configurations of the first embodiment and the second embodiment can be appropriately combined. For example, in the first embodiment, the outer surface of the beam 10 may be covered with the fireproof coating member 28 as in the second embodiment. Further, in the second embodiment, as in the first embodiment, the outer surface of the beam 20 does not have to be covered with the fireproof coating member 28.

Further, in the first and second embodiments, the beams 10 and 20 are joined to the column 12 as an example of the structural member, but the structural member supports the beams 10 and 20 and acts on the beams 10 and 20. It may be a beam (girder), a wall, or the like as long as it is a member to which the signal is transmitted.

10, 20, 30 beams 12 columns (an example of structural members)
16A, 16B concrete member (example of buckling suppression member)
22A, 22B Fireproof coating rib (example of buckling suppression member)
18 Sleeve tube (example of tubular member)
32 blocks (an example of buckling suppression member)
B Beam width D Beam formation L Beam length

Claims (4)

A metal beam whose ends are joined to the structural member, the beam length is D (mm), the beam length is L (mm), and the beam width is B (mm).
A buckling suppressing member provided on the beam, which has a larger heat capacity than the beam and suppresses buckling due to thermal expansion of the beam, is provided.
One end of the buckling suppressing member on the opposite side to the structural member is arranged at a position within L / 3 (mm) from the end of the beam, and the other end of the buckling suppressing member on the structural member side. The portion is arranged at a position separated from the end portion of the beam by D (mm) or more.
Beam buckling suppression structure. The buckling suppression structure for a beam according to claim 1, wherein the width of the buckling suppression member along the material axis direction of the beam is B (mm) or more. The buckling suppression structure for a beam according to claim 1 or 2, wherein the buckling suppression member is concrete. The buckling suppression structure of the beam according to any one of claims 1 to 3, wherein the end portion of the beam is rigidly joined to the structural member.

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