JP7674106B2 - Composite slab edge structure - Google Patents

Description

The present invention relates to a composite slab end structure.

A conventional composite slab end structure is described in Patent Document 1. This composite slab end structure comprises a composite slab having a deck plate and concrete, and a beam that is joined to the end of the composite slab. Mesh-like crack prevention bars are arranged inside the composite slab.

JP 2020-41348 A

Here, the composite slab as described above may be designed as a fire-resistant structure. In this way, when designed as a fire-resistant structure, it is desirable to ensure sufficient heat insulation even if cracks occur in the composite slab. Heat insulation is an important performance for the composite slab end structure, as the evaluation method is stipulated in the "Fire Resistance Testing and Evaluation Service Manual" of the General Building Research Corporation of Japan. This is to ensure that the temperature above the floor does not rise to the ignition temperature of combustible materials even if a fire occurs on the lower floor, and if cracks occur on the upper surface of the composite slab, the ignition temperature may be reached early. Heat insulation is an important indicator for preventing the spread of fire. However, in the above-mentioned composite slab end structure, cracks that occur on the beam side may reach the upper surface of the composite slab. In this case, when the lower surface is heated, the temperature of not only the lower surface, which is the heated surface, but also the upper surface may rise.

The present invention was made to solve these problems, and aims to provide a composite slab end structure that can improve heat insulation.

The composite slab end structure of the present invention is a composite slab end structure that includes a composite slab having a deck plate and concrete, and a beam that is joined to the end of the composite slab on its underside, and the end of the composite slab is provided with a crack direction control structure that prevents cracks from moving toward the upper side of the composite slab.

In the composite slab end structure of the present invention, a crack direction control structure is provided at the end of the composite slab to prevent cracks from moving toward the upper side of the composite slab. Therefore, even if a crack occurs, the crack direction control structure controls the crack direction, preventing the crack from moving toward the upper side of the composite slab. Therefore, the crack is prevented from reaching the upper surface of the composite slab, and even if the lower surface of the composite slab becomes a heated surface, the temperature of the upper surface is prevented from rising through the crack. As a result, the thermal insulation properties of the composite slab end structure can be improved.

The crack direction control structure comprises an L-shaped reinforcement provided inside the composite slab, the long side of the L-shaped reinforcement being arranged along the horizontal direction at least at a position higher than the deck plate, and the short side of the L-shaped reinforcement may extend downward from the long side on the outer peripheral edge side of the composite slab. In this case, the long side reinforcement can prevent cracks from progressing toward the upper surface by reinforcing a position higher than the deck plate. Furthermore, the short side reinforcement can reinforce the composite slab in the vertical direction near the outer peripheral edge of the composite slab. Therefore, cracks guided toward the outer peripheral edge side by the long side can be prevented from progressing upward near the outer peripheral edge.

Inside the composite slab, crack prevention bars are provided above the deck plate, and the long sides of the L-shaped bars can be placed on the crack prevention bars. In this case, the L-shaped bars can be positioned simply by placing the long sides on the crack prevention bars, making construction easier.

Inside the composite slab, crack prevention bars are provided above the deck plate, and the long side of the L-shaped bars may be connected to the crack prevention bars at a position below the crack prevention bars. In this case, the L-shaped bars can be easily positioned at a position below the crack prevention bars.

Inside the composite slab, crack prevention bars are provided above the deck plate, and the crack direction control structure may have mesh-like crack direction control bars provided inside the composite slab that control the direction of cracks. In this case, the crack direction control bars reinforce the composite slab at a different position from the crack prevention bars, thereby preventing cracks from moving upward.

The crack direction control bars may be placed on the deck plate. In this case, the crack direction control bars can be positioned simply by placing them on the deck plate, making construction easier.

The crack direction control reinforcement may be connected to the crack expansion prevention reinforcement at a position below the crack expansion prevention reinforcement. In this case, the crack direction control reinforcement can be easily positioned at a position below the crack expansion prevention reinforcement.

The present invention provides a composite slab end structure that can improve heat insulation.

FIG. 2 is a view of a composite slab end structure according to an embodiment of the present invention as viewed from the width direction. This is a view of the composite slab end structure seen from the span direction. FIG. 13 is a view of a composite slab end structure according to a modified example, viewed from the width direction. FIG. 1 is a view of a composite slab end structure according to a comparative example viewed from the width direction. FIG. 2 is a diagram showing the state of cracks in the composite slab end structure shown in FIG. 1 . FIG. 1 is a view of a composite slab end structure according to a comparative example viewed from the width direction. FIG. 13 is a view of a composite slab end structure according to a modified example, viewed from the width direction. FIG. 13 is a view of a composite slab end structure according to a modified example, viewed from the width direction. FIG. 13 is a view of a composite slab end structure according to a modified example, viewed from the width direction. FIG. 13 is a view of a composite slab end structure according to a modified example, viewed from the width direction. FIG. 13 is a view of a composite slab end structure according to a modified example, viewed from the span direction.

A preferred embodiment of the present invention will be described below with reference to the drawings.

Figure 1 is a view of a composite slab end structure 100 according to an embodiment of the present invention, viewed from the width direction D2. Figure 2 is a view of the composite slab end structure 100 viewed from the span direction. However, in Figure 1, the cross section of the concrete 2 is shown at an arbitrary position so that the internal structure of the composite slab 1 can be seen. As shown in Figure 1, the composite slab end structure 100 comprises a composite slab 1 having a deck plate 10 and concrete 2, and a beam 3 joined to the end 1a of the composite slab 1 on the underside 1d side. The composite slab 1 is a flat plate-like structure. The beam 3 supports the underside 1d of the end 1a of the composite slab 1 with its upper surface 3a.

As shown in FIG. 2, the deck plate 10 has a peak 10e that protrudes upward and a groove 10d between a pair of peaks 10e. The upper end 10c of the peak 10e spreads out like a flat plate. The lower end of the groove 10d also spreads out like a flat plate. The lower surface of the groove 10d is placed on the upper surface of the beam 3. The direction in which the peaks 10e and the grooves 10d extend is referred to as the span direction D1, and the direction in which the peaks 10e and the grooves 10d are aligned is referred to as the width direction D2.

The concrete 2 is filled inside the groove 10d of the deck plate 10 up to a position higher than the upper end 10c of the peak 10e. The concrete 2 has an upper surface that extends horizontally at a position spaced a predetermined distance upward from the upper end 10c of the deck plate 10. The upper surface 1b of the composite slab 1 is formed by the upper surface of the concrete 2. As shown in FIG. 1, the end of the concrete 2 in the span direction D1 is disposed on the outer periphery side of the end 10a of the deck plate 10 in the span direction D1. Therefore, the outer periphery 1c of the composite slab 1 is formed by the end of the concrete 2 in the span direction D1. The part of the concrete 2 that is on the outer periphery 1c side of the end 10a of the deck plate 10 is joined to the upper surface 3a of the beam 3.

The internal structure of the composite slab 1 will be described. Inside the composite slab 1, a stud 11 is provided that extends upward from the upper surface 3a of the beam 3. The stud 11 has a shaft portion 11a that extends in the vertical direction and a head portion 11b provided at the upper end of the shaft portion 11a. The head portion 11b is a portion formed with an outer diameter larger than that of the shaft portion 11a. The stud 11 is provided on the outer peripheral edge 1c side of the end portion 10a of the deck plate 10 in the span direction D1. In this embodiment, the stud 11 is provided in a position, for example, 4 cm inside from the beam end in the span direction D1 of the beam 3. The head portion 11b of the stud 11 is located at a position higher than the upper end 10c of the deck plate 10. The stud 11 is located at the center position of the groove portion 10d of the deck plate 10 in the width direction D2 (see FIG. 2).

Inside the composite slab 1, crack expansion prevention bars 12 are provided above the deck plate 10. The crack expansion prevention bars 12 are mesh-like members formed by crossing and joining multiple reinforcing bars 13 together. The crack expansion prevention bars 12 are members for preventing cracks from expanding when cracks occur in the concrete 2 of the composite slab 1. The crack expansion prevention bars 12 are the same as the "crack expansion prevention bars" disclosed on pages 26 and 27 of the "Deck Plate Floor Structure Design and Construction Standards 2018 Revised in December 2018 by the Japan Steel Construction Association". The crack expansion prevention bars 12 are located higher than the upper end 10c of the deck plate 10 and extend in the span direction D1 and width direction D2 over almost the entire area of the concrete 2. In the figure, the crack expansion prevention bars 12 are located higher than the studs 11, but may be located lower than the heads 11b of the studs 11. The crack expansion prevention bars 12 are positioned at a position spaced downward from the top surface 1b of the composite slab 1 (although not limited to a position about 30 mm below the top surface 1b). The end 12a of the crack expansion prevention bars 12 is positioned closer to the outer peripheral edge 1c than the studs 11, and positioned inward from the outer peripheral edge 1c (although not limited to a position about 30 mm inside the outer peripheral edge 1c).

At the end 1a of the composite slab 1, a crack direction control structure 20 is provided to prevent cracks from moving toward the upper side (top surface 1b side) of the composite slab 1. The crack direction control structure 20 controls the crack direction so that the cracks move toward the outer peripheral edge 1c and do not reach the top surface 1b. In this embodiment, the crack direction control structure 20 includes an L-shaped reinforcement 30 provided inside the composite slab 1.

The L-shaped bar 30 has a long side portion 31 and a short side portion 32. The short side portion 32 is shorter than the long side portion 31 and is joined so as to be perpendicular to the long side portion 31. The L-shaped bar 30 is formed by bending a single reinforcing bar. Alternatively, the L-shaped bar 30 may be formed by joining multiple reinforcing bars together using a joining method such as welding.

The long side 31 of the L-shaped bar 30 is arranged along the horizontal direction at a position at least higher than the deck plate 10. The long side 31 extends parallel to the span direction D1. The horizontal dimension of the long side 31 may be 200 mm or more. The short side 32 of the L-shaped bar 30 extends downward from the long side 31 on the outer peripheral edge 1c side of the composite slab 1. The short side 32 extends parallel to the up-down direction from the end of the long side 31 on the outer peripheral edge 1c side. The vertical dimension of the short side 32 may be 100 mm or more. In addition, the outer diameter of the reinforcing bar constituting the L-shaped bar 30 may be D10 or more. In this embodiment, the L-shaped bar 30 is arranged at the same position as the stud 11 in the width direction D2, but the position in the width direction D2 is not particularly limited.

In this embodiment, the long side 31 of the L-shaped reinforcement 30 is placed on the crack expansion prevention reinforcement 12. Therefore, the long side 31 is located between the upper surface 1b of the composite slab 1 and the crack expansion prevention reinforcement 12, directly above the crack expansion prevention reinforcement 12. The short side 32 is located in the area between the outer peripheral edge 1c of the composite slab 1 and the end 10a of the deck plate 10. Here, the short side 32 is located adjacent to the reinforcing bars 13 located closest to the outer peripheral edge 1c side among the reinforcing bars 13 extending in the width direction D2 of the crack expansion prevention reinforcement 12 on the outer peripheral edge 1c side. The lower end of the short side 32 is located lower than the upper end 10c of the deck plate 10 and the head 11b of the stud 11, and is located above the upper surface 3a of the beam 3.

In the vertical direction, the long side portion 31 may be located between the crack expansion prevention bar 12 and the upper end 10c of the deck plate 10, or at a higher position than the crack expansion prevention bar 12. The long side portion 31 may be located at the same position as the head 11b of the stud 11 (long side portion 31 in FIG. 3) or at a higher position than the head 11b, or may be located at a lower position than the head 11b of the stud 11. In the horizontal direction, the short side portion 32 may be located at a position closer to the outer periphery 1c than the end 10a of the deck plate 10. In the horizontal direction, the short side portion 32 may be located at the same position as the stud 11 (short side portion 32 in FIG. 3) or at a position closer to the outer periphery 1c than the stud 11, or may be located closer to the end 10a than the stud 11. In addition, when the long side portion 31 is located below the crack expansion prevention bar 12 as in FIG. 3, it may be connected to the crack expansion prevention bar 12. The long side 31 may be connected to the crack expansion prevention bars 12 by tying them together with a cable tie or the like.

Next, we will explain the action and effect of the composite slab end structure 100 according to this embodiment.

First, the composite slab end structure 200 according to the comparative example will be described with reference to FIG. 4. The composite slab end structure 200 differs from the composite slab end structure 100 according to the present embodiment in that it does not have a crack direction control structure 20. As shown in FIG. 4(a), in the composite slab end structure 200, when a high load and a long span load are applied, the crack CR generated on the beam 3 side may reach the upper surface 1b of the composite slab 1. In this case, when the lower surface 1d side is heated, the temperature of not only the lower surface 1d, which is the heated surface, but also the upper surface 1b may rise. Thus, there is a problem that sufficient heat insulation cannot be ensured. In addition, in the composite slab end structure 200, there is a possibility that a crack CR that breaks the edge between the composite slab 1 and the beam 3 may occur, and in this case, there is a problem that the original rotational rigidity cannot be exhibited. To ensure the heat insulation and non-damage properties of the composite slab end structure 200, it is preferable that the joint between the composite slab 1 and the beam 3 is destroyed, as shown in Figure 4(b), or that the crack CR deviates to the outer periphery 1c without reaching the upper surface 1b, as shown in Figure 4(c).

In contrast, in the composite slab end structure 100 according to this embodiment, a crack direction control structure 20 is provided at the end 1a of the composite slab 1 to prevent cracks from moving toward the top surface 1b of the composite slab 1. Therefore, even if a crack occurs, the crack CR is prevented from moving toward the upper side of the composite slab 1 by controlling the crack direction by the crack direction control structure 20. Therefore, the crack CR is prevented from reaching the top surface 1b of the composite slab, and even if the bottom surface 1d of the composite slab 1 becomes a heated surface, the temperature of the top surface 1b is prevented from rising through the crack CR. As a result, the thermal insulation properties of the composite slab end structure 100 can be improved.

The crack direction control structure 20 includes an L-shaped reinforcement 30 provided inside the composite slab 1, and the long side 31 of the L-shaped reinforcement 30 is arranged along the horizontal direction at least at a position higher than the deck plate 10, and the short side 32 of the L-shaped reinforcement 30 may extend downward from the long side 31 on the outer peripheral edge 1c side of the composite slab 1. In this case, the long side 31 can suppress the crack CR from progressing toward the upper surface 1b side by reinforcing a position higher than the deck plate 10. Furthermore, the short side 32 can reinforce the composite slab 1 in the vertical direction near the outer peripheral edge 1c of the composite slab 1. Therefore, the crack CR guided toward the outer peripheral edge 1c side by the long side 31 can be suppressed from moving upward near the outer peripheral edge 1c. Specifically, as shown in FIG. 5, the joint between the composite slab 1 and the beam 3 is destroyed, or even if a crack CR occurs, it is controlled so that it does not reach the upper surface 1b.

Inside the composite slab 1, crack expansion prevention bars 12 are provided above the deck plate 10, and the long side 31 of the L-shaped bars 30 may be placed on the crack expansion prevention bars 12. In this case, the L-shaped bars 30 can be positioned simply by placing the long side 31 on the crack expansion prevention bars 12, making construction easier.

Inside the composite slab 1, crack prevention bars 12 are provided above the deck plate 10, and the long side 31 of the L-shaped bars 30 may be connected to the crack prevention bars 12 at a position below the crack prevention bars 12. In this case, the L-shaped bars 30 can be easily positioned at a position below the crack prevention bars 12.

In the comparative example shown in Fig. 6(a) and (b), the composite slab end structure 300 has a spacer 301 raised upward from the upper surface 3a of the beam 3. The lower end of the spacer 301 is fixed to the upper surface 3a of the beam 3 by welding or the like, and the upper end of the spacer 301 is connected to the crack expansion prevention bar 12 by a tie wire or the like. Such a structure in which the crack expansion prevention bar 12 is simply connected to the beam 3 is not included in the crack direction control structure 20 in this embodiment. The spacer 301 reinforces the end 1a of the composite slab 1, but functions to prevent cracks from occurring, and does not control the direction of the crack when a crack occurs. The crack direction control structure 20 of the present application is composed of a member (here, L-shaped bar 30) arranged in the concrete 2 at a distance from the beam 3.

The present invention is not limited to the above-described embodiments.

For example, a composite slab end structure 400 as shown in FIG. 7 may be adopted. In the composite slab end structure 400, the crack direction control structure 20 is provided inside the composite slab 1, and has mesh-like crack direction control bars 50 that control the direction of cracks. The crack direction control bars 50 are composed of mesh-like members similar to the crack expansion prevention bars 12. The crack direction control bars 50 are arranged at a different height position from the crack expansion prevention bars 12. Furthermore, the range in which the crack direction control bars 50 are provided in the planar direction is a partial area near the end 1a of the composite slab 1.

The rebar diameter and pitch of the crack direction control bar 50 may be 150 mm or less at φ6 mm, and 200 mm or less at D10. In addition, with regard to the horizontal position of the crack direction control bar 50, the end 50a on the outer peripheral edge 1c side of the crack direction control bar 50 may be located closer to the outer peripheral edge 1c side than the end 10a of the deck plate 10. In addition, the opposite end 50b may be located at a position 200 mm or more away from the end 10a of the deck plate 10 toward the inner peripheral side. In addition, the crack direction control bar 50 may be provided in the same range as the crack expansion prevention bar 12 in the width direction D2. The crack direction control bar 50 may be located in a range of 30 mm or more from the upper surface 3a of the beam 3 in the vertical direction. In addition, the crack direction control bar 50 may be located at the same position as the upper end 10c of the deck plate 10 or at a higher position than the upper end 10c. In addition, the crack direction control reinforcement 50 may be placed at the same position as the crack expansion prevention reinforcement 12 or at a lower position than the crack expansion prevention reinforcement 12.

In the example shown in Figure 7, the crack direction control bar 50 is placed on the deck plate 10. That is, the crack direction control bar 50 is supported from below by the deck plate 10 while being placed on the upper end 10c of the deck plate 10. The end 50a on the outer periphery 1c side is positioned at approximately the same position in the span direction D1 as the crack expansion prevention bar 12.

According to this composite slab end structure 400, the crack direction control structure 20 is provided inside the composite slab 1 and has mesh-like crack direction control bars 50 that control the direction of cracks. In this case, the crack direction control bars 50 reinforce the composite slab 1 at a position different from the crack expansion prevention bars 12, thereby preventing the cracks from moving upward. For example, as shown in Figure 7 (b), a crack CR moving upward from the beam 3 is prevented from moving upward at the location reinforced by the crack direction control bars 50, and the crack CR deviates toward the outer peripheral edge 1c and reaches the outer peripheral edge 1c.

The crack direction control bars 50 may also be placed on the deck plate 10. In this case, the crack direction control bars 50 can be positioned simply by placing them on the deck plate 10, making construction easier.

The crack direction control bars 50 may also be arranged as shown in FIG. 8. That is, the crack direction control bars 50 may be connected to the crack expansion prevention bars 12 at a position below the crack expansion prevention bars 12. In this case, the crack direction control bars 50 can be easily positioned at a position below the crack expansion prevention bars 12. The connection method is not particularly limited, but the crack direction control bars 50 may be connected to the crack expansion prevention bars 12 with a tie wire.

In addition, in each of the above-mentioned embodiments, the studs 11 are provided inside the concrete 2, but the studs 11 may be omitted, for example, as shown in FIG. 9. In FIG. 9, the structure in FIG. 1 is omiting the studs 11, but the studs 11 may be omitted from other forms of structures.

Also, the composite slab end structure 500 shown in Figures 10 and 11 may be adopted. In the composite slab end structure 500, the crack direction control structure 20 is provided inside the composite slab 1 and has a U-shaped reinforcement 530 that is provided to extend in the vertical direction. In this case, the U-shaped reinforcement 530 can control the direction of the crack. The position of the U-shaped reinforcement 530 in the span direction is not particularly limited, but may be arranged closer to the outer peripheral edge 1c of the composite slab 1 than the end 10a of the deck plate 10. The length of the U-shaped reinforcement 530 may be set to the same length as the short side portion 32 of the L-shaped reinforcement 30, and may be set to, for example, 100 mm or more. The position of the U-shaped reinforcement 530 in the width direction is not particularly limited and may be the same as the L-shaped reinforcement 30. The U-shaped reinforcement 530 may be provided so as to extend downward while straddling the crack expansion prevention reinforcement 12. The U-shaped bar 530 has sides 531 and 532 that extend downward and are aligned side by side, straddling one of the reinforcing bars of the crack expansion prevention bar 12.

1...composite slab, 2...concrete, 3...beam, 10...deck plate, 12...crack prevention bars, 20...crack direction control structure, 30...L-shaped bars, 31...long side, 32...short side, 50...crack direction control bars, 100, 400, 500...composite slab end structure.

Claims (3)

a composite slab having a deck plate and concrete;
A composite slab end structure comprising an end of the composite slab and a beam joined at the underside,
A crack direction control structure is provided at the end of the composite slab to suppress cracks from moving toward the upper side of the composite slab;
The crack direction control structure includes an L-shaped reinforcement provided inside the composite slab,
The long side of the L-shaped reinforcement extends parallel to the span direction of the deck plate and is disposed along the horizontal direction at least at a position higher than the deck plate,
The short side of the L-shaped reinforcement extends downward from the long side on the outer periphery side of the composite slab,
The horizontal dimension of the long side portion is 200 mm or more, the vertical dimension of the short side portion is 100 mm or more, and the outer diameter of the reinforcing bar constituting the L-shaped bar is D10 or more,
A stud is provided inside the composite slab and extends upward from the beam;
A composite slab end structure , wherein the L-shaped reinforcement is positioned at the same position as the stud in a horizontal direction perpendicular to the direction in which the long side portion extends . Inside the composite slab, crack expansion prevention bars are provided above the deck plate,
The composite slab end structure according to claim 1 , wherein the long side of the L-shaped reinforcement is placed on the crack expansion prevention reinforcement. a composite slab having a deck plate and concrete;
A composite slab end structure comprising an end of the composite slab and a beam joined at the underside,
A crack direction control structure is provided at the end of the composite slab to suppress cracks from moving toward the upper side of the composite slab;
The crack direction control structure includes an L-shaped reinforcement provided inside the composite slab,
The long side of the L-shaped reinforcement extends parallel to the span direction of the deck plate and is disposed along the horizontal direction at least at a position higher than the deck plate,
The short side of the L-shaped reinforcement extends downward from the long side on the outer periphery side of the composite slab,
Inside the composite slab, crack expansion prevention bars are provided above the deck plate,
A composite slab end structure in which the long side of the L-shaped reinforcement is connected to the crack expansion prevention reinforcement at a position below the crack expansion prevention reinforcement.

Images