JP2014231726A - Column-beam structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a column-beam structure capable of reducing stress acting on a column from a steel beam in the case of fire, even when thick fire resistive covering is not applied to the steel beam.SOLUTION: A column-beam structure includes a beam that has a steel member erected between columns, a buckling guide part that is provided at an end of the beam and that makes the steel member generate local buckling when the beam is heated, and a concrete floor slab that is provided on the beam.

Description

  The present invention relates to a column beam structure in which steel beams are installed between columns.

  A steel beam installed in a steel structure building and spanned between columns has high thermal conductivity, and thus expands due to thermal expansion in a fire. Due to this, it is conceivable that excessive deformation occurs in the column on which the steel beam is installed, and additional stress is generated.

  On the other hand, a steel frame or a steel beam provided in a steel structure building is generally provided with a fireproof coating on the surface for providing fire resistance. For example, Patent Document 1 discloses a fireproof coating material in which hydraulic cement, water glass, and a hydroxide compound are mixed.

  However, when it is intended to reduce the thermal expansion of the steel beam using such a fireproof coating material, it is necessary to coat the surface of the steel beam with a thick fireproof coating material, which takes time and effort.

JP-A-6-32664

  In view of such a fact, an object of the present invention is to provide a column beam structure capable of reducing the stress acting on the column from the steel beam in the event of a fire without applying a thick fireproof coating to the steel beam.

  The invention according to claim 1 is a seat having a steel member erected between columns, and a seat provided at an end of the beam and causing local buckling of the steel member when the beam is heated. It is a column beam structure which has a bending induction part and a concrete floor slab provided on the beam.

  In the first aspect of the invention, when the beam is heated in the event of a fire, the steel member expands due to thermal expansion and the portion of the steel member provided with the buckling induction portion is in a high temperature state. Local buckling occurs at the site. Further, the locally buckled portion is in a hinge state, and the downward bending of the steel member is allowed.

  As a result, the extension of the steel member due to thermal expansion is absorbed, and the stress acting on the column from the steel member is reduced. Moreover, the member angle which arises in a pillar by the extension by the thermal expansion of a steel frame member can be reduced. Therefore, even if a thick fireproof coating is not applied to the steel member (steel beam), the stress acting on the column from the steel member (steel beam) can be reduced during a fire.

  In addition, when local buckling occurs in the part of the steel member where the buckling induction part is provided, the bending moment generated at the end of the beam becomes small because the locally buckled part becomes a hinge state, and the beam The shear force generated at the end is borne by the shear strength of the floor slab. The bending moment of the central part of the beam, which increases due to local buckling in the part of the steel member where the buckling induction part is provided, is borne by the central part of the beam that has a margin of bending strength due to the effect of combining with the floor slab. Is done. As a result, even if local buckling occurs in a portion of the steel member where the buckling guide portion is provided, the beam is held between the columns without collapsing.

  According to a second aspect of the present invention, in the column beam structure according to the first aspect, the surface of the steel member is covered with a fireproof coating, and the fireproof coating located at the end of the beam is thinned or eliminated. And constitutes the buckling guide portion.

  In the invention according to the second aspect, the buckling induction portion can be configured without making much effort by thinning or eliminating the fireproof coating.

  According to a third aspect of the present invention, in the column beam structure according to the second aspect, the steel member is a shaped steel including an upper flange, a web, and a lower flange, and the upper flange located at an end of the beam. The surface is covered with the fireproof coating.

  In the invention according to claim 3, even if local buckling occurs in the part of the steel member provided with the buckling induction portion, the upper flange can bear the tensile force generated in the beam, and the structural strength of the beam Can be maintained. Therefore, in the event of a fire, even if local buckling occurs in a portion of the steel member where the buckling guide portion is provided, the beam is not collapsed and is held between the columns.

  Since the present invention has the above-described configuration, it is possible to reduce the stress acting on the column from the steel beam in the event of a fire without applying a thick fireproof coating to the steel beam.

It is a side view which shows the column beam structure which concerns on embodiment of this invention. It is AA sectional drawing of FIG. It is a side view which shows the deformation | transformation which arises in a pillar by the expansion | extension of the conventional steel beam at the time of a fire. It is a side view which shows the effect | action of the column beam structure which concerns on embodiment of this invention. It is explanatory drawing which shows the bending moment which acts on the beam which concerns on embodiment of this invention. It is a side view which shows the column beam structure which concerns on embodiment of this invention. It is BB sectional drawing of FIG. 6, and CC sectional drawing of FIG.

  Embodiments of the present invention will be described with reference to the drawings. First, a column beam structure according to an embodiment of the present invention will be described.

  A side view of FIG. 1 shows a column beam structure 10 according to an embodiment of the present invention. The column beam structure 10 includes a beam 20 having a steel member 18, a buckling guide portion 22 provided at an end of the beam 20, and a floor slab made of reinforced concrete supported on the beam 20 and provided on the beam 20. 24. The steel member 18 is an H-shaped steel having an upper flange 12, a web 14, and a lower flange 16.

  Both ends of the steel member 18 are fixed to steel columns 26 and 28, and are laid between the columns 26 and 28. As shown in FIG. 1 and FIG. 2 which is an AA cross-sectional view of FIG. 1, the buckling guide portion 22 covers the entire surface of the upper flange 12 located at the end of the beam 20 with a fireproof coating S. The entire surface of the web 14 and the lower flange 16 located at the end of 20 is exposed without being covered with the fireproof coating S. The steel member 18 positioned other than the end of the beam 20 is covered with the fireproof coating S on the entire surface (the entire surfaces of the upper flange 12, the web 14, and the lower flange 16).

  In this embodiment, since the upper surface of the upper flange 12 is covered with the floor slab 24, “the entire surface of the steel member 18 is covered with the fireproof coating S” or “the entire surface of the upper flange 12 is fireproof. When the expression “covered with the coating S” is used in the description of the present embodiment, the entire surface of the steel member 18 excluding the upper surface of the upper flange 12 or the upper flange 12 excluding the upper surface of the upper flange 12. Means that the entire surface is covered with the fireproof coating S. On the upper surface of the upper flange 12, the floor slab 24 is provided with a fireproof coating to ensure fire resistance.

  That is, with respect to the configuration in which the entire surface of the steel member 18 is covered with the fireproof coating S, the buckling induction portion 22 is configured by eliminating a part of the fireproof coating S located at the end of the beam 20. When the beam 20 is heated in the event of a fire, the buckling induction portion 22 causes a phase buckling to occur at the portion of the steel member 18 where the buckling induction portion 22 is provided (the end of the steel member 18). This part is hinged.

  In the present embodiment, the end portion of the beam 20 is a portion of the beam 20 from a position separated in the beam length direction from the end surface of the beam 20 by a length that is 1/3 times the beam length of the beam 20 to the end surface of the beam 20. Means. When local buckling occurs in the steel member 18 in this portion (this portion is in a hinge state), the bending moment of the joint between the columns 26 and 28 and the beam 20 has a general column beam joint. Below bending strength.

  It should be noted that the beam length direction is separated from the end face of the beam 20 by ¼ times the beam length of the beam 20, and the length of the beam 20 from the end face of the beam 20 by １ ／ times the beam length of the beam 20. It is preferable to place any part of the beam 20 between the positions separated from each other in a hinge state. Therefore, the position separated from the end face of the beam 20 by ¼ times the beam length of the beam 20 in the beam length direction, and the length from the end face of the beam 20 by １ ／ times the beam length of the beam 20 in the beam length direction. If any part of the beam 20 between the positions separated from each other can be hinged, all of the end portions of the beam 20 may be used as the buckling guide portions 22 or a part of the end portions of the beams 20 may be buckled. The guiding unit 22 may be used. For example, when a bolt joint is provided at the end of the beam 20, this portion is bypassed (fireproof coating is applied to this portion). Alternatively, the buckling guide portion 22 may be provided closer to the columns 26 and 28.

  Next, the operation and effect of the column beam structure according to the embodiment of the present invention will be described.

  As shown in the side view of FIG. 3, the steel beam 34 provided between the pillar 30 and the pillar 32 provided in the steel building generally expands due to thermal expansion due to high thermal conductivity. To do. Due to this, it is conceivable that excessive deformation occurs in the columns 30 and 32 on which the steel beam 34 is installed, and additional stress is generated.

  On the other hand, in the column beam structure 10 of the present embodiment, as shown in the side view of FIG. 4, when the beam 20 is heated in the event of a fire, the steel member 18 expands by thermal expansion and is buckled. The site | part of the steel member 18 in which the part 22 is provided will be in a high temperature state. As a result, thermal stress (compressive force) is generated in the portion of the steel member 18 where the buckling induction portion 22 is provided, and the rigidity of this portion is reduced, so the steel frame where the buckling induction portion 22 is provided. Local buckling occurs at the site of the member 18 (in the case of this embodiment, the lower flange 16 and the web 14 are deformed in the out-of-plane direction). Further, the locally buckled portion is in a hinge state, and the downward bending of the steel member 18 is allowed.

  As a result, the extension of the steel member 18 due to thermal expansion is absorbed, and the stress acting on the columns 26 and 28 from the steel member 18 is reduced. Moreover, the member angle which arises in the pillars 26 and 28 by the extension by the thermal expansion of the steel frame member 18 can be reduced. Therefore, the stress acting on the columns 26 and 28 from the beam 20 (steel member 18) in the event of a fire can be reduced without applying a thick fireproof coating to the steel member 18.

  Further, as shown in FIG. 5A, the bending moment value 36 generated in the beam 20 in the normal state where the end portion of the beam 20 is not in a hinge state is a joint portion between the columns 26 and 28 and the beam 20. It increases in the vicinity and in the center of the beam 20. On the other hand, as shown in FIG. 5B, when local buckling occurs in the portion of the steel member 18 where the buckling guide portion 22 is provided, the locally buckled portion 38 becomes a hinge state, The bending moment value 40 generated in the beam 20 decreases near the joint between the columns 26 and 28 and the beam 20 and increases at the center of the beam 20.

  Therefore, if the central part of the beam 20 functions as a structural member in the event of a fire (for example, if a sufficient fireproof coating is applied to the central part of the steel member 18), the bending moment generated in the beam 20 will be reduced. This can be borne by the bending strength of the central portion of the member 18. Further, the shear force generated at the end of the beam 20 can be borne by the shear strength of the floor slab 24. As a result, even when local buckling occurs in the portion of the steel member 18 where the buckling guide portion 22 is provided, the beam 20 is not collapsed but is held between the column 26 and the column 28.

  Note that the central portion of the steel member 18 installed between the columns 26 and 28 generally has a sufficient bending strength due to the effect of combining with the floor slab 24. When the distance between the column 26 and the column 28 is long and the total length of the beam 20 is long, the bending of the central portion of the steel member 18 is compared with the bending moment at the end of the steel member 18 in a normal temperature state that is not during a fire. Since the moment is large, the increase in the bending moment at the center of the steel member 18 during a fire is small.

  Furthermore, in the column beam structure 10 according to the present embodiment, the buckling guide portion 22 is configured without a large amount of time and effort by configuring the buckling guide portion 22 without a part of the fireproof coating S located at the end of the beam 20. Can be configured.

  Further, in the column beam structure 10 of the present embodiment, the entire surface of the upper flange 12 located at the end of the beam 20 is covered with a fireproof coating, so that the steel member 18 provided with the buckling induction portion 22 is provided at the site. Even if local buckling occurs, the upper flange 12 can bear the tensile force generated in the beam 20, and the structural strength of the beam 20 can be maintained. Therefore, even if local buckling occurs in the portion of the steel member 18 where the buckling guide portion 22 is provided in the event of a fire, the beam 20 is held between the column 26 and the column 8 without collapsing.

  The embodiment of the present invention has been described above.

  In this embodiment, the entire surface of the upper flange 12 is covered with the fireproof coating S, and the entire surface of the web 14 and the lower flange 16 is exposed without being covered with the fireproof coating S. Although shown, the buckling induction part 22 should just be able to raise local buckling in the site | part of the steel member 18 in which the buckling induction part 22 is provided, when the beam 20 is heated at the time of a fire, In contrast to the configuration in which the entire surface of the member 18 is covered with the fireproof coating S, the buckling induction portion 22 may be configured by eliminating part or all of the fireproof coating S located at the end of the beam 20. For example, the buckling induction portion 22 may be configured by covering the entire surfaces of the upper flange 12 and the web 14 with the fireproof coating S and exposing the entire surface of the lower flange 16 without covering with the fireproof coating S. 12 and the upper part of the web 14 (a part of the web 14) are covered with the fireproof coating S, and the entire surface of the remaining part of the steel member 18 is exposed without being covered with the fireproof coating S. The buckling guide 22 may be formed by exposing the entire surface of the steel member 18 without being covered with the fireproof coating S, or the fireproof coating covering the entire surfaces of the upper flange 12 and the web 14. Compared to S, the thickness of the fireproof coating S covering the entire surface of the lower flange 16 may be reduced.

  Moreover, the buckling induction part 22 should just be able to raise local buckling in the site | part of the steel member 18 in which the buckling induction part 22 is provided, when the beam 20 is heated at the time of a fire. In contrast to the configuration in which the entire surface of 18 is covered with the fireproof coating S, a part or all of the fireproof coating S located at the end of the beam 20 is made thinner than the fireproof coating S covering the surface other than the end of the beam 20. Therefore, the buckling guide portion 22 may be configured. Further, the cross section of the steel member 18 positioned at the end of the beam 20 (the thickness of the steel material) is changed to the cross section of the steel member 18 positioned other than the end of the beam 20 (the thickness of the steel material) within a range that does not affect the structural yield strength. ) Or by forming a through hole only in the web 14 of the steel member 18 located at the end of the beam 20 to form a buckling induction portion that is locally buckled in stress.

  Furthermore, in the column beam structure 10 of the present embodiment, an example in which the beam 20 having the steel member 18 whose surface is covered with the fireproof coating S is shown, the side view of FIG. 6 and the BB cross-sectional view of FIG. 7 (a), and FIG. 7 (b), which is a cross-sectional view taken along the line C-C of FIG.

  The beam 42 is a side concrete-filled steel beam in which the side surface of the steel member 18 is filled with concrete E, and constitutes the buckling induction portion 46 so that the end portion of the steel member 18 is not filled with the concrete E.

  In this embodiment, the pillars 26 and 28 are made of steel. However, the pillars 26 and 28 may be made of steel, reinforced concrete, steel reinforced concrete, wooden or the like, or CFT (Concrete). -Filled Steel Tube: Filled steel tube concrete structure).

  Furthermore, the column beam structure 10 of the present embodiment can be constructed by new construction work and repair work.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in a various aspect.

DESCRIPTION OF SYMBOLS 10, 44 Column beam structure 12 Upper flange 14 Web 16 Lower flange 18 Steel member 20, 42 Beam 22, 46 Buckling guide part 24 Floor slab 26, 28 Column S Fireproof coating

Claims (3)

A beam having a steel member erected between the columns;
A buckling induction portion provided at an end of the beam and causing local buckling of the steel member when the beam is heated;
A concrete floor slab provided on the beam;
Column beam structure with The surface of the steel member is covered with a fireproof coating,
The column beam structure according to claim 1, wherein the buckling guide portion is configured by thinning or eliminating the fireproof coating located at an end portion of the beam. The steel member is a shaped steel having an upper flange, a web and a lower flange,
The column beam structure according to claim 2, wherein a surface of the upper flange located at an end of the beam is covered with the fireproof coating.

Images