JP2021085168A - Steel beam having floor slab with step - Google Patents

Abstract

To provide a steel beam having a floor slab with steps capable securing enough deformability by restricting deformation outside the structure plane of an upper flange of the steel beam caused by lateral buckling, without providing a lateral buckling preventive beam or a sub-beam, even when the floor slab has steps.SOLUTION: A steel beam 1 having a floor slab with steps comprises: a steel beam 5 with an H-section with both ends rigidly jointed to columns 3 and having no lateral buckling stiffening member; and a concrete floor slab 13 having jointed steps via headed stubs 11 provided over the whole length of an upper flange 7 of the steel beam 5. The headed stub 11 is set with a top part thereof to be positioned above a lower face of a side positioned vertically above an upper face of the upper flange 7 of the steel beam 5 in the concrete slab 13 having steps.SELECTED DRAWING: Figure 1

Description

The present invention relates to a steel beam with a floor slab in which a concrete floor slab exists on the upper part of the beam and the concrete floor slab and the beam are joined, and particularly a steel beam with a floor slab having a step on the floor slab. It is about.

In a steel structure building, a phenomenon called lateral buckling during an earthquake may cause the steel beam to deform in the direction perpendicular to the beam axis, and may not exhibit the specified strength and deformation ability. By arranging it, lateral buckling is prevented by restraining the movement of the steel beam in the direction perpendicular to the material axis.
At that time, it is customary to restrain the out-of-structure deformation of the lower flange by joining the member such as an angle joined to the beam or the grandchild beam and the lower flange of the steel frame beam.

11 and 12 show a conventional form in which a steel beam is joined to a concrete floor slab via a headed stud.
The conventional steel beam 41 with a floor slab includes a steel beam 5 having an H-shaped cross section whose both ends are rigidly joined to a pillar 3, and a concrete floor slab 13 joined to the upper part of the steel beam 5 via a headed stud 51. A gusset plate 49 was provided on the side surface of the steel beam 5, the beam 45 was bolted to the gusset plate 43 at the upper part of the steel beam 5, and the angle 47 was provided at the lower part of the beam 45. It is joined so as to straddle the gusset plate 43 and the lower part of the gusset plate 49 on the side surface of the steel beam 5. As a result, the out-of-plane deformation due to the lateral buckling of the steel beam 5 is restrained.
Further, the concrete floor slab 13 is provided with reinforcing bars 31 so that cracks do not occur with respect to a fixed load or a loaded load. Further, a deck plate 25 for placing concrete is provided so as to hang on the upper flange 7 of the steel frame beam 5.
The web 19 of the steel beam 5 is welded to the column 3 or bolted to the shear plate 21 welded to the column 3.

In the examples shown in FIGS. 11 and 12, both sides of the steel beam 5 in the concrete floor slab 13 in the direction orthogonal to the beam axis are both on the upper flange 7 of the steel beam 5, but the concrete floor slab 13 is the beam axis. There may be steps on both sides in the orthogonal direction. In this way, the concrete floor slab 13 is provided with a step, and only one side of the concrete floor slab 13 in the direction perpendicular to the beam material axis is located at the same height as the upper flange 7 of the steel beam 5, and the concrete floor slab on the other side. 13 and 14 show conventional forms in which the lower surface of 13 is located vertically above the upper surface of the upper flange 7 of the steel beam 5.

In the case of the embodiment shown in FIGS. 13 and 14, as shown in FIG. 14, the angle 23 (or channel steel) is welded to the side surface of the upper flange 7 of the steel beam 5 on the side where the concrete floor slab 13 is located above. By joining and placing concrete 29 on the angle 23 (or channel steel) with the deck plate 25, only one side of the concrete floor slab 13 in the direction perpendicular to the beam axis is the upper flange 7 of the steel beam 5. The structure is located above. At this time, the height of the headed stud 51 is generally determined with respect to the thickness of the concrete floor slab 13, and is not adjusted according to the step height.

Recently, as shown in Non-Patent Document 1, when a steel beam is joined to a concrete floor slab via a headed stud, the out-of-plane deformation of the upper flange is restrained, and a beam for preventing lateral buckling, a grandchild. The idea that beams and angles can be omitted is widespread.
Based on this idea, in Patent Document 1, the torsional rigidity of the concrete floor slab joined to the steel beam is set to 10 times the torsional rigidity of the steel beam, so that lateral buckling can be performed even without the lateral buckling stiffener. Design methods that can be prevented have been proposed.

Further, in Patent Document 2, a floor slab that is continuously present only on one side of the upper part of the steel beam and the horizontal direction perpendicular to the material axis of the steel beam is joined via a headed stud arranged on the upper surface of the steel beam. It has been proposed to provide a reinforcing reinforcing bar for reinforcing the shearing force in the horizontal direction perpendicular to the beam material axis of the headed stud in the steel frame beam. In Patent Document 2, by doing so, even when the distance between the headed stud and the concrete edge of the floor slab is short, the headed stud has sufficient yield strength, and the floor slab provides an upper flange. It is said that the horizontal displacement in the direction perpendicular to the material axis is sufficiently constrained.

Further, in Patent Document 3, as in Patent Document 2, in the steel frame beam with a floor slab in which the floor slab is continuously present only on the upper part of the steel frame beam and one side in the horizontal direction perpendicular to the material axis of the steel frame beam, the drawing is performed. The projected area of the headed stud is specified.

Japanese Patent No. 5885911 Japanese Unexamined Patent Publication No. 2018-135668 Japanese Unexamined Patent Publication No. 2018-204425

Architectural Institute of Japan "Various Composite Structure Design Guidelines / Explanation, 2010"

As described above, the idea that the small beam 45, the grandchild beam, and the angle 47 for preventing lateral buckling can be omitted by restraining the out-of-planning deformation of the steel frame beam 5 by the concrete floor slab 13 is widespread. It is essential that the out-of-concrete deformation of the upper flange 7 of 5 is sufficiently restrained.
However, in the conventional form in which the concrete floor slab 13 having a step is provided as shown in FIGS. 13 and 14, the distance between the headed stud 51 and the edge portion of the concrete floor slab 13 is short. Therefore, when the lateral buckling stiffening member is omitted, the headed stud 51 does not have sufficient proof stress against the force that the steel beam 5 tends to deform out of the structure due to lateral buckling during an earthquake. There is a risk that the headed stud joint will break and the steel beam 5 will not be able to exert sufficient deformation ability. At this time, at the headed stud joint, the concrete 29 located between the headed stud 51 and the edge of the concrete floor slab 13 is broken into a cone shape.

In this regard, Patent Document 1 describes the required performance of the floor slab for sufficiently restraining the out-of-structure deformation of the upper flange of the steel frame beam even when there is no lateral buckling stiffening member. However, it is not mentioned when the floor slab has a stepped shape, and the headed stud that joins the floor slab and the steel beam is not specified.

Further, in Patent Document 2, when the floor slab such as the outer periphery of the building is continuous only on one side in the horizontal direction perpendicular to the material axis of the steel frame beam, the distance between the headed stud and the edge of the floor slab becomes short and the headed stud Reinforcement around the headed studs with reinforcing bars is described for the possibility that the yield strength of the slab may decrease. Therefore, it is conceivable to apply this idea to floor slabs having steps.
However, providing reinforcing bars on the headed studs requires a great deal of time and effort in the implementation work.

According to Patent Document 3, when the floor slab is continuous only on one side in the horizontal direction orthogonal to the material axis of the steel frame beam, the torsional deformation becomes large and the headed stud may be pulled out. The required projected area is specified so that a sufficient amount of headed studs are placed for pulling out.
However, if a step is provided on the floor slab with the vicinity of the steel beam as the boundary and the height direction position of the floor slab is different on one side and the other side in the horizontal direction perpendicular to the material axis of the steel beam, the stud with the head and the edge of the floor slab are reached. There is a risk that the distance between the heads will be shortened and the strength of the headed studs will be reduced.

The present invention has been made to solve such a problem, and even if there is a step on the floor slab, a steel frame beam due to lateral buckling is provided without providing a beam for preventing lateral buckling, a grand beam, or the like. It is an object of the present invention to provide a steel beam with a floor slab having a step that can restrain the out-of-structure deformation of the upper flange and secure a sufficient deformation ability.

(1) The steel beam with a floor slab having a step according to the present invention includes a steel beam having an H-shaped cross section in which both ends are rigidly joined to the column and no lateral buckling stiffening member is provided, and a steel beam having an H-shaped cross section. It has a concrete floor slab joined via a headed stud provided over the entire length of the flange, and the lower surface on one side of the concrete floor slab in the direction perpendicular to the beam axis is the upper surface of the upper flange of the steel beam. A steel frame with a floor slab that is located at the same height as the concrete floor slab and has a step so that the lower surface of the concrete floor slab on the other side in the direction perpendicular to the beam axis is located vertically above the upper surface of the upper flange of the steel beam. It ’s a beam,
The headed stud is characterized in that its top is installed so as to be located above the lower surface of the other side of the concrete floor slab.

(2) Further, in the above (1), the vertical distance between the upper surface of the upper flange of the steel beam and the lower surface of the concrete floor slab on the other side is within 150 mm, and the headed stud. It is characterized in that the vertical distance between the top portion and the lower surface on the other side of the concrete floor slab is 50 mm or more.

(3) Further, in the above (1) or (2), the thickness of the concrete floor slab on the side where the height of the headed stud is the same as the upper surface of the steel beam. It is characterized by being larger than the one.

According to the present invention, the concrete floor slab is provided by installing the top of the headed stud so as to be located above the lower surface of the concrete floor slab on the side vertically above the upper surface of the upper flange of the steel beam. Even if the distance between the headed stud and the floor slab edge is short due to the step, a headed stud joint with sufficient performance to restrain the out-of-concrete deformation of the upper flange of the steel beam is realized. it can. As a result, it is possible to realize a steel beam with a concrete floor slab having a step without a lateral buckling stiffening member without requiring a great deal of labor such as arranging reinforcing bars.

It is explanatory drawing of the steel frame beam with a floor slab having a step which concerns on embodiment of this invention. FIG. 1 is a cross-sectional view taken along the line AA of FIG. It is explanatory drawing of another aspect of the steel frame beam with a floor slab having a step which concerns on embodiment of this invention (the 1). It is explanatory drawing of another aspect of the steel frame beam with a floor slab having a step which concerns on embodiment of this invention (the 2). It is explanatory drawing of the test body A corresponding to the conventional example in an Example. FIG. 5B is an arrow view BB of FIG. It is explanatory drawing of the test body B corresponding to the example of this invention in an Example. It is the arrow BB figure of FIG. It is explanatory drawing of the loading device used in an Example. It is a graph which shows the test result of an Example. It is explanatory drawing of the conventional steel beam with a floor slab. 11 is a cross-sectional view taken along the line AA of FIG. It is explanatory drawing of the steel frame beam with a floor slab having a conventional step. FIG. 13 is a cross-sectional view taken along the line AA of FIG.

The steel beam with a floor slab according to the present embodiment will be described with reference to FIGS. 1 and 2. In addition, in FIGS. 1 and 2, the same parts as those in FIGS. 11 to 14 showing the conventional example are designated by the same reference numerals.
The steel beam 1 with a floor slab having a step according to the present embodiment includes a steel beam 5 having an H-shaped cross section in which both ends are rigidly joined to the column 3 and no lateral buckling stiffening member is provided, and the steel beam 5. It has a concrete floor slab 13 having a step joined via a headed stud 11 provided over the entire length of the upper flange 7, and connects the upper flange 7 and the lower flange 9 of the steel beam 5. A gusset plate 15 is provided on the gusset plate 15.
Hereinafter, each configuration will be described in detail.

<Pillar>
The type of the column 3 is not particularly limited, and examples thereof include a welded assembly box-shaped column, a square steel tube column, an H-shaped column, a CFT column, an RC column, and an SRC column.
The column 3 is provided with a steel plate called a diaphragm 17 in order to transmit the force transmitted from the upper and lower flanges 7 and 9 of the steel frame beam 5 to the column 3. The diaphragm 17 is divided into a through diaphragm type, an inner diaphragm type, and an outer diaphragm type according to the joint type with the column 3.

<Steel beam>
Steel beam 5 has a H-shaped cross section, with design strength 235N / mm ² or more, and a 440 N / mm ² or less of the steel. Steel materials with a design standard strength of over 440 N / mm ² are not suitable for beams because they have high strength and therefore have low elongation and poor deformation ability during an earthquake. The size of the steel beam 5 is as follows: H-shaped steel with a small cross section described in JIS G3192, H-shaped steel with a maximum beam length of 1000 mm, and a welded assembled H-shaped cross-section member with a large cross-section exceeding 1000 mm. Is applicable. Among these, for large cross-section members whose beam length exceeds 1000 mm and ^{H-shaped cross-section members made of high-strength steel with a design standard strength of 355 N / mm 2} or more, angles 47 and the like for suppressing out-of-plane deformation of the lower flange 9 are used. Stiffening members are often required.
The steel beam 5 of the present embodiment is not provided with the beam 45 or the angle 47 for the purpose of restraining the out-of-structure deformation as in the conventional example shown in FIGS. 11 to 14.

Both ends of the steel beam 5 are rigidly joined to the column 3, and in this case, the upper and lower flanges 7 and 9 of the steel beam 5 are welded to the column 3 or the diaphragm 17 provided on the column 3. When the upper and lower flanges 7 and 9 are joined to the diaphragm 17, they are joined in the following manner depending on the type of the diaphragm 17.

In the inner diaphragm type, since the diaphragm 17 is provided inside the column 3, the upper and lower flanges 7 and 9 of the steel beam 5 are joined to the column 3. In the through diaphragm type and the outer diaphragm type, the upper and lower flanges 7 and 9 of the steel frame beam 5 are welded to the diaphragm 17.
The web 19 of the steel beam 5 is welded to the column 3 with high-strength bolts or welded to the column 3.

The angle 23 (or channel steel) is welded and joined only to the side surface of the upper flange 7 of the steel beam 5 where the concrete floor slab 13 is located above due to the step. The angle 23 (or channel steel) is joined to the upper flange 7 of the steel beam 5 by intermittent fillet welding, and is not joined to the column 3.
A deck plate 25 for placing concrete of a concrete floor slab 13 is welded to the upper flange 7 of the steel beam 5 and the angle 23 (or channel steel), and the concrete floor slab 13 is provided on the deck plate 25 for placing concrete.
The deck plate 25 includes a flat deck for a throw-away formwork, a corrugated synthetic deck that behaves integrally with the concrete 29, and a throw-away formwork deck with a reinforcing bar truss with welded reinforcing bars.

The steel beam 1 with a floor slab is not provided with a beam 45 or an angle 47 as a lateral buckling stiffening member, and a beam 27 for preventing the concrete floor slab 13 from bending or installing a deck plate is provided. It is joined. Then, a gusset plate 15 is welded to the side surface of the web 19 in order to join the ends of the beam 27.

<Concrete floor slab>
The concrete floor slab 13 is a concrete floor slab 13 having a step formed in the vicinity immediately above the upper flange 7 of the steel frame beam 5.
More specifically, in the concrete floor slab 13 having a step, the lower surface of the concrete floor slab 13 on one side in the direction perpendicular to the beam axis is located at the same height as the upper surface of the upper flange 7 of the steel beam 5, and the concrete floor slab The lower surface on the other side of the beam 13 in the direction orthogonal to the beam axis is configured to be located vertically above the upper surface of the upper flange 7 of the steel beam 5.

The concrete floor slab 13 has a reinforced concrete structure in which reinforcing bars 31 are arranged inside the concrete 29, and in the stepped portion of the concrete floor slab 13, the reinforcing bars 31 are arranged so as to be continuous above and below the step.
Ordinary concrete and lightweight concrete are used for the concrete 29, and deformed reinforcing bars, round steel bars, and welded wire mesh are used for the reinforcing bars 31. In addition, half PC slabs that use precast concrete plates manufactured at the factory as a formwork that is also used on site, and void slabs that include hollow parts are also applicable.

<Stud with head>
The headed stud 11 is welded and joined over the entire length of the upper flange 7 of the steel frame beam 5, and as shown in FIG. 2, the top thereof is above one side in the direction orthogonal to the beam material axis due to the step. A high-height headed stud 11 is used so as to be located above the lower surface of the concrete floor slab 13 on the side.
As a result, even if the concrete 29 between the headed stud 11 and the edge of the concrete floor slab 13 is broken into a cone shape due to the out-of-plane deformation of the upper flange 7 of the steel beam 5 at the time of an earthquake, the headed stud 11 The vicinity of the top of the building is buried in sound concrete 29. Therefore, it is possible to prevent abrupt deterioration of the yield strength, and it is possible to maintain the performance of the joint portion of the headed stud 11 so that sufficient deformation ability can be expected from the steel frame beam 5.

It is desirable that the headed stud 11 has a shaft diameter of 16 mm or more, which can be expected to have sufficient yield strength. Further, the arrangement shape of the headed stud 11 includes a one-row arrangement, a plurality of rows of two or more rows, a staggered arrangement, and the like.

As shown in FIG. 3, the position of the top of the headed stud 11 is set to be 50 mm or more above the lower surface of the floor slab on the side above one side in the direction perpendicular to the beam axis due to the step. It is preferable that the height of the headed stud 11 is defined, and the vertical distance between the upper surface of the steel beam 5 and the lower surface of the concrete floor slab 13 located on the upper side by the step is within 150 mm.
This makes it more reliable to maintain the performance of the headed stud joint in the event of an earthquake.

Further, as shown in FIG. 4, the height of the headed stud 11 may be equal to or greater than the thickness of the concrete floor slab 13 on the side that is not raised by the step.
By setting the height of the headed stud 11 to be equal to or greater than the thickness of the concrete floor slab 13, even if cracks occur from the step portion shown in FIG. 4, the presence of the headed stud 11 causes the upper and lower concrete floor slabs 13 to be raised. It is possible to prevent breakage such as separation.

In order to confirm the effect of the present invention, an element experiment was carried out using a test piece imitating a headed stud joint of a steel beam with a floor slab having a step as shown in FIGS. 5 to 8.
There are two test bodies, and the test body A shown in FIGS. 5 and 6 corresponds to the conventional example, and the test body B shown in FIGS. 7 and 8 corresponds to the example of the present invention.

Both of the two test bodies A and B were provided with a step having a height of 150 mm, and the headed studs 11 and 51 were provided with one shaft having a diameter of 19 mm. Further, since the angle 23 and the channel steel provided on the side surface of the upper flange 7 of the steel frame beam 5 are members for hanging the deck plate 25 and not structural members, they are omitted in the test piece.
Further, the concrete 29 was made of ordinary concrete, and deformed reinforcing bars were buried as slab reinforcement. Further, the thickness of the concrete floor slab 13 was set to 150 mm both above and below the step.
Then, in the test body A simulating the conventional form, the headed stud 51 was set to 100 mm, and in the test body B simulating the invention example, the height of the headed stud 11 was set to 200 mm, which was 50 mm higher than the step height.

Forced horizontal displacement was monotonically applied to these test pieces using the loading device shown in FIG. 9, assuming out-of-structure deformation of the upper flange 7 of the steel frame beam 5.
FIG. 10 is a graph showing the test results, in which the vertical axis represents the load [kN] and the horizontal axis represents the horizontal displacement [mm] of the loading point.
In the test body A, the concrete 29 between the concrete edge of the step portion and the stud 51 with the head was broken in a cone shape, so that the yield strength was greatly reduced, whereas in the test body B, the concrete edge and the head of the step portion. Even after the concrete 29 between the concrete 29 and the attached stud 11 was broken into a cone shape, the proof stress did not significantly decrease, and the proof stress was maintained sufficiently.
This is because even if the concrete 29 between the concrete edge and the headed stud 11 is destroyed as described above, the vicinity of the top of the headed stud 11 is buried in the sound concrete 29, so that the yield strength drops sharply. Due to being able to prevent.

From the above results, by making the height of the headed stud 11 higher than the step height, the headed stud joint can maintain sufficient performance against the horizontal displacement perpendicular to the beam axis, thereby causing the head. It has been demonstrated that the steel beam 5 can secure the upper flange restraining effect sufficient to exhibit the required deformation ability without providing a reinforcing member such as a reinforcing bar 31 in the vicinity of the stud joint.

1 Steel beam with floor slab 3 Pillar 5 Steel beam 7 Upper flange 9 Lower flange 11 Headed stud 13 Concrete floor slab 15 Gasset plate 17 Diaphragm 19 Web 21 Shear plate 23 Angle 25 Deck plate 27 Beam 29 Concrete 31 Reinforcing bar <Conventional example ＞
41 Steel beam with floor slab 43 Gusset plate 45 Small beam 47 Angle 49 Gusset plate (steel beam)
51 Stud with head

Claims (3)

Both ends are rigidly joined to the column and joined via a steel beam with an H-shaped cross section that is not provided with a lateral buckling stiffener and a headed stud provided over the entire length of the upper flange of the steel beam. With concrete floor slabs
In the concrete floor slab, the lower surface of one side of the concrete floor slab in the direction orthogonal to the beam axis is located at the same height as the upper surface of the upper flange of the steel beam, and the other surface of the concrete floor slab in the direction orthogonal to the beam axis is located. A floor slab having a step so that the lower surface on the side is located vertically above the upper surface of the upper flange of the steel beam.
The headed stud is a steel beam with a floor slab having a step, wherein the top thereof is installed so as to be located above the lower surface of the other side of the concrete floor slab. The vertical distance between the upper surface of the upper flange of the steel beam and the lower surface of the concrete floor slab on the other side is within 150 mm, and the vertical distance between the top of the stud with a head and the lower surface of the other side of the concrete floor slab is vertical. The steel beam with a floor slab having a step according to claim 1, wherein the direction distance is 50 mm or more. The step according to claim 1 or 2, wherein the height of the headed stud is larger than the thickness of the concrete floor slab on the side where the lower surface is located at the same height as the upper surface of the steel beam. Steel beams with floor slabs.

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