Steel material for composite beam or composite girder

Abstract

Provided is a steel material for a composite beam or a composite girder which can significantly improve the effect of integration with concrete and with which improvements in lateral buckling strength and earthquake resistance can be expected.　The present invention is characterized by being configured from a vertical web 2, a horizontal upper flange 3 and lower flange 4, and a steel rib 5 that is vertically fixed to the upper surface of the upper flange 3 or the lower surface of the lower flange 4, wherein: the rib 5 has a base part on the lower side thereof and an projection part on the upper side thereof; the projection part has a thickness dimension that is greater than that of the base part and is shaped such that both the right and left side parts thereof bulge outward further than both side parts of the base part; a taper part is formed at the boundary between the projection part and the base part; and node projections extending in the vertical direction are formed on both side surfaces of the base part so as to be arranged in parallel and at intervals in the longitudinal direction of the steel material.

Description

Steel for composite beams or composite girders

[0001] The present invention relates to a steel material used as a beam material for a building, a girder material for a bridge, etc., and more particularly to a steel material for a composite beam or a composite girder that is integrated with concrete.

[0002] As shown in Figure 11, conventional steel materials (shaped steel or welded steel) used to form composite beams or composite girders are composed of a vertical web 72, horizontal upper and lower flanges 73 and 74, and a number of headed studs 75 fixed (welded) to the upper surface of the upper flange 73 (or the lower surface of the lower flange 74). The headed studs 75 are arranged in parallel at intervals in the longitudinal and width directions of the steel material, and as shown in Figure 7, the steel material 71 and the concrete 76 can be integrated by pouring concrete 76 so that the headed studs 75 are embedded.

[0003] JP 2002-004475 A JP 2017-072018 A

[0004] In steel materials for composite beams or composite girders, improvements in the integration effect with concrete are desired. The present invention aims to provide a steel material for composite beams or composite girders that can be expected to not only significantly improve the integration effect with concrete, but also to improve lateral buckling strength and earthquake resistance.

[0005] The steel material for composite beams or composite girders according to the present invention is composed of a vertical web, horizontal upper and lower flanges, and a steel rib fixed perpendicular to the upper surface of the upper flange or the lower surface of the lower flange, the rib having a lower base and an upper protrusion, or an intermediate base and upper and lower protrusions, the protrusions having a thickness greater than that of the base, with both left and right sides bulging outward more than both sides of the base, a tapered portion formed at the boundary between the protrusions and the base, and nodular protrusions extending in the vertical direction formed on both sides of the base so as to be parallel to each other at intervals in the longitudinal direction of the steel material.

[0006] In this steel material for composite beams or composite girders, two or more ribs are preferably arranged parallel to the longitudinal direction of the steel material and spaced apart in the width direction of the steel material. Furthermore, the tapered portions preferably have an angle of 50 to 80 degrees with respect to the horizontal when the rib is upright, and the spacing between the nodal projections is preferably set to a dimension within the range of 20 to 100 mm.

[0007] The composite beam or composite girder of the present invention is characterized in that the steel material and the concrete are integrated by pouring concrete so that the ribs of the steel material for the composite beam or composite girder are buried.

[0008] The steel material for composite beams or composite girders according to the present invention can significantly improve the integration effect with concrete in both the horizontal and vertical directions compared to conventional techniques. Furthermore, in composite beams or composite girders formed using this steel material, the lateral buckling strength of the steel material is improved, which may allow lateral stiffeners to be omitted. Furthermore, during earthquakes, the inter-story drift angle can be reduced, which is expected to improve seismic resistance.

[0009] FIG. 1 is a cross-sectional perspective view, a partial plan view, and a partial side view of a steel material 1 for a composite beam or composite girder according to a first embodiment of the present invention. FIG. 2 is a vertical cross-sectional view of a rib 5 shown in FIG. 1. FIG. 3 is a partial horizontal cross-sectional view of the rib 5 taken along line A-A in FIG. 2. FIG. 4 is a cross-sectional view of a composite beam or composite girder formed using the steel material 1 shown in FIG. 1. FIG. 5 is a diagram showing the dimensions of the headed stud 75 and the rib 5 used in a bending pull-out test conducted on a specimen of the present invention and a specimen of the comparative example. FIG. 6 is a graph showing the results of a bending pull-out test conducted on a specimen of the present invention and a specimen of the comparative example (the relationship between the bending moment M and the rotation angle θsc). FIG. 7 is a graph showing the results of a bending pull-out test conducted on a specimen of the present invention and a specimen of the comparative example (the value of initial rotational rigidity). FIG. 8 is a graph showing the results of a bending pull-out test conducted on a specimen of the present invention and a specimen of the comparative example (the relationship between the bending moment M and the rotation angle θsc due to slippage of the shear stop). Fig. 9 is a diagram showing an example of the configuration of a rib 5 used in a steel material for a composite beam or composite girder according to a second embodiment of the present invention. Fig. 10 is a cross-sectional view showing an example of the configuration of a steel material 1 for a composite beam or composite girder according to a third embodiment of the present invention. Fig. 11 is a cross-sectional perspective view of a conventional steel material 71 used when forming a composite beam or composite girder. Fig. 12 is a cross-sectional view of a composite beam or composite girder formed using the steel material 71 of Fig. 11.

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a cross-sectional perspective view, a partial plan view, and a partial side view of a steel material 1 for a composite beam or composite girder according to a first embodiment of the present invention. As shown in Fig. 1, the steel material 1 is composed of a vertical web 2, horizontal upper and lower flanges 3 and 4, and two steel ribs 5 fixed (welded) perpendicularly to the upper surface of the upper flange 3. The ribs 5 are arranged parallel to each other along the longitudinal direction of the steel material 1 and at a predetermined interval in the width direction of the upper flange 3. Note that both end surfaces of the steel material 1 have the same cross-sectional shape as the steel material 1 shown in Fig. 1 (1).

[0011] 2 is a vertical cross-sectional view of the rib 5 shown in FIG. 1. As shown in the figure, the rib 5 is basically composed of a lower base 51 and an upper protrusion 52. The protrusion 52 is thicker than the lower base 51, and both left and right sides bulge outward from both sides of the base 51. The protrusion 52 is formed so as to be continuous over the entire length of the rib 5.

[0012] A tapered portion 53 is formed at the boundary between the protrusion 52 and the base 51 to fill in the step or to smooth out the step (to make the included angle at the step obtuse). This tapered portion 53 is set so that the angle R with respect to the horizontal line is 60° (preferably in the range of 50 to 80°) when the rib 5 is upright.

[0013] Figure 3 is a partial horizontal cross-sectional view of the rib 5 taken along line A-A in Figure 2. As shown, protrusions 54 (protrusions) are formed on both side surfaces of the base 51. These protrusions 54 extend vertically from the tapered portion 53 (see Figure 2) to the lower end of the base 51, and as shown in Figure 1, are arranged in a large number in parallel with intervals in the longitudinal direction. In this embodiment, the spacing between the protrusions 54 is set to 33.3 mm (preferably within the range of 20 to 100 mm).

[0014] Figure 4 is a cross-sectional view of a composite beam or girder formed using the steel material 1 of Figure 1. As shown in the figure, concrete 6 is poured onto the upper flange 3 so that the rib 5 is embedded, thereby allowing the steel material 1 and the concrete 6 to be integrated.

[0015] A composite beam or girder formed using steel members 1 having ribs 5 as in this embodiment can significantly improve the effect of integrating the steel members and concrete compared to a composite beam or girder formed using conventional steel members 71 having headed studs 75 as shown in Figure 11. This has been confirmed by the following tests conducted by the inventors of the present invention.

[0016] First, a comparative specimen (a composite beam or girder specimen formed by pouring concrete 76 on conventional steel material 71 as shown in FIG. 11 ) and a specimen of the present invention (a composite beam or girder specimen formed by pouring concrete 6 on steel material 1 as shown in FIG. 1 ) were prepared.

[0017] In the test specimen of the comparative example, a steel material 71 was used in which headed studs 75 with standard dimensions (head 77 diameter: 32 mm, thickness (height): 10 mm, shank 78 diameter: 19 mm, height: 100 mm) as shown on the left side of Figure 5 were arranged in two rows across the width of the upper flange 73 at a standard spacing (spacing between adjacent headed studs: 200 mm).

[0018] On the other hand, in the test specimen of the present invention, as shown on the right side of Figure 5, the width of the protrusion 52 was 17 mm, the width of the base 51 was 9 mm, the protrusion amount of the protrusion 52 (the step size from the side surface of the base 51) was 4 mm on each side, the height of the protrusion 52 was 20 mm, the length (height) of the nodular protrusion 54 was 80 mm, the protrusion amount of the nodular protrusion 54 (the size of the protrusion protruding laterally from the side surface of the base 51) was 3 mm, and the spacing between the nodular protrusions 54 in the longitudinal direction of the rib 5 was 33.3 mm. Steel material 1 was used in which two ribs 5 were arranged at a distance in the width direction of the upper flange 3.

[0019] These specimens were then subjected to bending pull-out tests. Specifically, each specimen was turned upside down (so that the concrete 6, 76 shown in Figures 4 and 12 was on the lower side and the bottom flanges 4, 74 were on the upper side), and the concrete 6, 76 was fixed to the floor of the test site. Loads were then repeatedly applied to the bottom flanges 4, 74 from the side (in a direction perpendicular to the girder axis), and the initial rotational rigidity and strength were measured. The results are shown in Figures 6 to 8.

[0020] As shown in the graphs of Figures 6 and 7, the initial rotational rigidity in the horizontal direction of the specimen of the present invention was improved by 1.99 times compared to the specimen of the comparative example, and as shown in the graph of Figure 8, the yield strength of the specimen of the present invention (yield strength at a rotation angle of 0.05 rad after maximum yield strength) was improved by 1.77 times compared to the specimen of the comparative example. These test results confirmed that when a composite beam or composite girder is formed using the steel material 1 of the present invention, the effect of integrating the steel material and concrete can be significantly improved compared to conventional techniques.

[0021] Furthermore, the ribs 5 fixed onto the upper flange 3 can improve the rigidity of the upper flange 3. Furthermore, in a composite beam or composite girder formed using this steel material 1, the restraint effect on the lateral displacement of the horizontal concrete slab is large, and the lateral buckling strength of the steel material 1 is improved, so it may be possible to omit lateral stiffeners. Furthermore, during an earthquake, a reduction in the inter-story deformation angle can be expected, improving seismic resistance.

[0022] Furthermore, in a composite beam or composite girder formed using this steel material 1, among the reinforcing bars placed in the concrete 6 above the steel material 1 (the concrete slab in a composite beam, or the deck in a composite girder), the placement of reinforcing bars extending in the longitudinal direction of the steel material 1 above the steel material 1 can be omitted.

[0023] Furthermore, it is desirable to use a single reinforcing bar design for the reinforcing bars in the direction perpendicular to the longitudinal direction of the steel material 1. Specifically, as shown by the dashed lines in Figure 4, by placing the reinforcing bars 8 in the concrete 6 directly on the ribs 5, spacers for supporting the reinforcing bars 8 at a predetermined height during concrete pouring are no longer necessary, thereby improving the workability of the concrete slab.

[0024] Furthermore, when using shaped steel as the steel material 1, it is preferable to weld a cover plate 9 to the lower flange 4 for economic reasons. Specifically, as shown in Fig. 4, by welding the cover plate 9 to the underside of the lower flange 4 and lowering the neutral axis of the composite cross section toward the lower flange 4, the rigidity of the concrete slab can be increased, and the rigidity of the composite beam or composite girder can be increased.

[0025] In the above embodiment, the rib 5 is fixed to the upper surface of the upper flange 3, but it can also be fixed to the lower surface of the lower flange 4. Furthermore, the number of ribs 5 fixed to the steel material 1 is not limited to two, and one or three or more ribs 5 can also be fixed to the upper flange 3, etc.

[0026] Furthermore, if it is necessary to join a portion of the upper flange 3 to another element and the rib 5 interferes at the joint, a portion of the rib 5 can be appropriately cut vertically and horizontally to form a notch (not shown) that will prevent interference at the joint, and a through hole (not shown) can be formed in the rib 5 to allow the passage of reinforcing bars to be placed inside the concrete 6 (see Figure 4).

[0027] Furthermore, in the above embodiment, the node protrusion 54 extends vertically from the tapered portion 53 to the lower end of the base 51, but as long as it extends in the up-and-down direction (from the tapered portion 53 side to the lower end side of the base 51), it is not necessarily limited to the vertical direction, and it can also be formed to extend diagonally along the side of the base 51.

[0028] In the above embodiment, the rib 5 (see Figure 2) consisting of the lower base 51 and the upper protrusion 52 is fixed to the steel material 1, but as shown in Figure 9, the rib 5 consisting of the intermediate base 51 and its upper and lower protrusions 52 can also be fixed to the steel material 1 (second embodiment).

[0029] In addition, in the example of Figure 4, the ribs 5 are placed only on the upper surface of the upper flange 3 in order to integrate the concrete 6 poured on top of the upper flange 3 with the steel material 1. However, when the concrete 6 is wrapped around the entire steel material 1 (above the upper flange 3, below the lower flange 4, and on both the left and right sides of the web 2) to form a composite beam or composite girder, the ribs 5 can be placed not only on top of the upper flange 3, but also below the lower flange 4 and on both the left and right sides of the web 2, as shown in Figure 10 (third embodiment).

[0030] 1: Steel, 2: Web, 3: Upper flange, 4: Lower flange, 5: Rib, 51: Base, 52: Projection, 53: Tapered portion, 54: Nodal projection, 6: Concrete, 71: Steel, 72: Web, 73: Upper flange, 74: Lower flange, 75: Headed stud, 76: Concrete, 77: Head, 78: Shank, 8: Reinforcing bar, 9: Cover plate,

Claims

1. A steel material for composite beams or composite girders, comprising a vertical web, horizontal upper and lower flanges, and a steel rib fixed perpendicular to the upper surface of the upper flange or the lower surface of the lower flange, wherein the rib has a lower base and an upper protrusion, or an intermediate base and upper and lower protrusions, the protrusions are thicker than the base, and both left and right sides bulge outward from both sides of the base, a tapered portion is formed at the boundary between the protrusion and the base, and nodal protrusions extending in the vertical direction are formed on both sides of the base so as to be parallel to each other at intervals in the longitudinal direction of the steel material.

2. A steel material for composite beams or composite girders as described in claim 1, characterized in that two or more ribs are arranged parallel to each other along the longitudinal direction of the steel material and in parallel with a space in the width direction of the steel material.

3. The steel material for composite beams or composite girders described in claim 1, characterized in that the tapered portion has an angle of 50 to 80 degrees relative to the horizontal when the rib is in an upright position.

4. The steel material for composite beams or composite girders according to claim 1, characterized in that the spacing dimension of the nodal projections is set within the range of 20 to 100 mm.

5. A composite beam characterized in that the steel ribs for the composite beam or composite girder according to any one of claims 1 to 4 are embedded in concrete, thereby integrating the steel and concrete.

6. A composite girder characterized in that the steel material and concrete are integrated by pouring concrete so that the ribs of the steel material for the composite beam or composite girder described in any one of claims 1 to 4 are embedded in the concrete.

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