Steel materials for composite columns, and composite columns

Abstract

The present invention provides a steel material for composite columns and a composite column that can ensure sufficient shear resistance with a compact cross-section, and can also be expected to have the effect of partially bearing sectional forces and providing a stiffening effect. [Solution] The column has a cylindrical portion 2 and a protruding rib 5, the protruding rib 5 being welded and fixed so as to protrude outward from the outer surface 21 of the side of the cylindrical portion 2 and / or protrude inward from the inner surface 22, and extending in the axial direction of the column, and having a base end joined to the side of the cylindrical portion 2, a tip on the opposite side, and an intermediate portion between them, the base end, tip and intermediate portion extending in the axial direction of the column, the base end and tip have a larger thickness dimension than the intermediate portion and have a shape that bulges outward more than the intermediate portion, and node protrusions are arranged on both sides of the intermediate portion, extending in the horizontal direction and arranged in parallel with spacing in the vertical direction.

Description

[Technical Field]

[0001] The present invention relates to steel materials for forming columns of structures, and more particularly to steel materials for forming composite columns by integrating with concrete, and to composite columns using such steel materials. [Background technology]

[0002] Composite columns, formed by integrating steel and concrete, are used as columns in various structures. Figure 12 is a side view of a conventional steel member 71 for a composite column (structural column), and Figure 13 is a horizontal cross-sectional view thereof. By pouring concrete on the inside and outside of this steel member 71 and allowing it to harden and integrate them, a composite column consisting of steel member 71 and concrete can be formed. As shown in the figures, numerous headed stud dowels 75 are attached to the inner and outer surfaces of the steel member 71 as shear supports to prevent the poured concrete from shearing and integrating with the steel member 71. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-146303 [Patent Document 2] Japanese Patent Application Publication No. 6-101273 [Patent Document 3] Japanese Patent Publication No. 2017-72018 [Overview of the project] [Problems that the invention aims to solve]

[0004] In conventional steel members 71 for composite columns, as shown in Figures 12 and 13, stiffeners (e.g., plate ribs) may be attached to the inner and / or outer surfaces to improve buckling resistance. However, in this case, the mounting positions of the headed stud dowels 75 may be limited (for example, to positions between multiple stiffeners placed at intervals), and if the cross-section is narrow, it becomes difficult to install the required number of headed stud dowels 75.

[0005] Furthermore, there is a need for steel materials for composite columns that can ensure sufficient shear resistance with a more compact cross-section. The present invention aims to solve the problems of the conventional technology described above, and aims to provide steel materials for composite columns and composite columns that can ensure sufficient shear resistance with a compact cross-section and can also be expected to have a stiffening effect. [Means for solving the problem]

[0006] The steel material for composite columns according to the present invention has a cylindrical portion and a projection rib, the projection rib is welded and fixed so as to protrude outward from the outer surface of the side of the cylindrical portion and / or protrude inward from the inner surface, and extends in the axial direction of the column, the projection rib has a base end joined to the side of the cylindrical portion, a tip on the opposite side, and an intermediate portion between them, the base end, tip, and intermediate portion extend in the axial direction of the column, the base end and tip have a greater thickness dimension than the intermediate portion and have a shape that bulges outward more than the intermediate portion, tapered portions are formed at the boundaries between the base end and tip and the intermediate portion, and nodal projections are arranged on both sides of the intermediate portion, extending horizontally from the tapered portion on the base end side to the tapered portion on the tip end side, and arranged in parallel with spacing in the vertical direction.

[0007] Furthermore, it is preferable that the dimensions of the steel material for this composite column are set such that the ratio of the installation length to the height of the protruding rib is 1.5 or more, and that the ratio of the width of the nodal protrusion to the total throat thickness of the welded parts of the protruding rib is greater than 5.

[0008] Furthermore, it is preferable that the structure further includes a bottom portion that closes the lower opening of the cylindrical portion, and a cross portion positioned on the bottom portion, formed by joining four steel plates so that their horizontal cross-section is cross-shaped, with the protruding ribs welded and fixed to each side of the cross portion in a direction extending in the axial direction of the column.

[0009] The composite column according to the present invention is characterized by being formed from the steel material for the composite column and concrete poured inside and / or outside its cylindrical portion. [Effects of the Invention]

[0010] The steel material for composite columns according to the present invention has projections at the base and tip (parts that bulge outward relative to the intermediate section) and projection ribs with nodal projections in the intermediate section that are fixed to the base and tip. As a result, it can be expected to have high adhesion strength to concrete and high shear rigidity, and can secure sufficient shear resistance with a compact cross-section compared to conventional headed stud dowels. For this reason, even when the column cross-section is small, the projection ribs that act as shear stoppers can be efficiently arranged and the embedding length in concrete can be shortened.

[0011] Furthermore, in addition to its shear-preventing effect, this protruding rib can also be expected to partially bear the sectional forces of the base material (steel) and provide a stiffening effect, effectively preventing buckling even when using steel with a small plate thickness as the base material. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a side view of a steel material 1 for a composite column according to the first embodiment of the present invention. [Figure 2]Figure 2 is a horizontal cross-sectional view of the steel material 1 shown in FIG. 1, taken along line I-I. [Figure 3] Figure 3 is a horizontal cross-sectional view of the steel material 1 shown in FIG. 1, taken along line II-II. [Figure 4] Figure 4 is a perspective view of the steel material 1 shown in FIG. 1. [Figure 5] Figure 5 is a cutaway perspective view showing the internal structure of the steel material 1 shown in FIG. 1. [Figure 6] Figure 6 is a perspective view of the protruding rib 5 fixed to the steel material 1 shown in FIG. 1. [Figure 7] Figure 7 is a plan view of the protruding rib 5 shown in FIG. 6, and a vertical cross-sectional view taken along line III-III. [Figure 8] Figure 8 is a side view of the protruding rib 5. [Figure 9] Figure 9 is a graph showing the relationship between the ratio (L / H) of the installation length L to the height H of the protruding rib 5, and the term in the parentheses of "Equation 2". [Figure 10] Figure 10 is a perspective view of the protruding rib 5. [Figure 11] Figure 11 is a graph showing the relationship between the ratio (B / t) of the width B of the nodal projection 54 of the protruding rib 5 to the total throat thickness t of the welded portions 56, and the designed concrete compressive strength Fc. [Figure 12] Figure 12 is a side view of a steel material 71 for a conventional composite column (construction core column). [Figure 13] Figure 13 is a horizontal cross-sectional view of the steel material 71 shown in FIG. 12. DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiments of the present invention will be described below with reference to the attached drawings. Figure 1 is a side view of a steel material 1 for a composite column according to the first embodiment of the present invention, Figure 2 is a horizontal cross-sectional view of the steel material 1 shown in Figure 1 along line II, Figure 3 is a horizontal cross-sectional view of the steel material 1 shown in Figure 1 along line II-II, Figure 4 is a perspective view of the steel material 1 shown in Figure 1, and Figure 5 is a cutaway perspective view showing the internal structure of the steel material 1 shown in Figure 1. The steel material 1 shown in these figures is for forming a structural column (a column embedded in the ground when constructing the basement floors of a high-rise building, etc., using the inverted construction method), and is composed of a cylindrical part 2, a bottom part 3, a cross part 4, and a protruding rib 5.

[0014] As shown in Figure 2, the cylindrical portion 2 is a rectangular tube with a square horizontal cross-section, formed by welding the long sides of four rectangular steel plates together. As shown in Figure 5, the bottom portion 3 is formed from a single square steel plate and is welded to the cylindrical portion 2 so as to close its lower opening. As shown in Figure 3, the cross portion 4 is formed by joining four steel plates so that the horizontal cross-section is cross-shaped, has a height dimension of approximately 1 / 5 of the height dimension of the cylindrical portion 2, and is positioned on top of the bottom portion 3 (inside the cylindrical portion 2).

[0015] As shown in Figure 4, the lower part of the cylindrical portion 2 has slits 23 that extend vertically at the center of the width direction of the four sides, and the cross portion 4 is positioned so that its four outer ends 42 protrude slightly to the outside of the cylindrical portion 2 through the slits 23 on each side of the cylindrical portion 2. The lower end of the cross portion 4 is welded to the upper surface of the bottom portion 3, and the outer ends 42 are welded to the slits 23 of the cylindrical portion 2.

[0016] As shown in Figures 1 to 5, projection ribs 5 are fixed (welded) to the cylindrical portion 2 and the cross portion 4. All of these projection ribs 5 protrude perpendicularly to the sides of the cylindrical portion 2 and the cross portion 4, and are arranged to extend in the axial direction (up and down direction) of the column.

[0017] More specifically, in the upper part (the portion above the lower part where the cross section 4 is located), as shown in Figures 1, 2, and 4, the protruding ribs 5A are arranged to protrude outward from the outer surface 21 of each side of the cylindrical section 2, and as shown in Figures 2 and 5, the protruding ribs 5B are arranged to protrude inward from the inner surface 22 of each side of the cylindrical section 2. The protruding ribs 5A and 5B are located at the center of the width direction of each side of the cylindrical section 2.

[0018] In the lower part where the cross section 4 is located, as shown in Figures 1, 3, and 4, the protruding ribs 5C are arranged so that two ribs protrude outward from the outer surface 21 of each side of the cylindrical section 2. The upper end of the protruding rib 5C is positioned at an intermediate position between the corner 24 of the cylindrical section 2 (see Figure 4) and the outer end 42 of the cross section 4, so that it partially overlaps with the lower end of the protruding rib 5A. Furthermore, as shown in Figures 3 and 5, the protruding ribs 5D are arranged so that one rib protrudes from each of the eight side surfaces 41 of the cross section 4. The protruding ribs 5D are positioned at the center in the width direction of each side surface 41 of the cross section 4 (from the central inner corner 43 to the inner surface 22 of the cylindrical section 2 where the outer end 42 is in contact).

[0019] Figure 6 is a perspective view of the projection rib 5, and Figure 7(1) is a plan view of the projection rib 5. The projection rib 5 is basically composed of a base end 51 joined to the side of the cylindrical part 2 (see Figure 1, etc.), a tip end 52 on the opposite side, and an intermediate part 53 between them. The base end 51, tip end 52, and intermediate part 53 all extend in the axial direction of the column, and the base end 51 and tip end 52 have a greater thickness than the intermediate part 53, with both sides bulging outward more than both sides of the intermediate part 53.

[0020] A tapered portion 55 is formed at the boundary between the base portion 51 and the tip portion 52 and the intermediate portion 53 to fill in the step or smooth out the step (make the inner corner angle of the step obtuse). This tapered portion 55 is set to have an angle of 60° with respect to the direction perpendicular to the protruding direction of the projection rib 5 (the direction parallel to the side surface of the cylindrical portion 2 to be joined) (preferably within the range of 50 to 80°).

[0021] Figure 7(2) is a partial cross-sectional view of the projection rib 5 along the line III-III shown in Figure 7(1). As shown, segmental projections 54 (ridges) are formed on both sides of the intermediate portion 53. As shown in Figure 6, these segmental projections 54 extend horizontally from the tapered portion 55 on the base end 51 side to the tapered portion 55 on the tip end 52 side, and are also formed in a large number of parallel sections spaced apart in the vertical direction. In this embodiment, the spacing dimension of the segmental projections 54 is set to 33.3 mm (preferably within the range of 20 to 100 mm).

[0022] When forming a composite column (structural column) using the steel material 1 shown in Figures 1 to 5, concrete is poured inside the cylindrical portion 2, and formwork is placed outside the cylindrical portion 2 (for example, at the position indicated by the dashed line in Figure 2). Concrete is then poured inside the formwork (between the formwork and the outer surface 21 of the cylindrical portion 2), and the concrete is allowed to harden. This fills the inside of the cylindrical portion 2 with concrete, forming a composite column in which the outside of the cylindrical portion 2 is covered with concrete. Reinforcement bars (not shown) can be placed inside the concrete as appropriate.

[0023] The protruding ribs 5 (5A-5D) fixed to the cylindrical portion 2 and the cross portion 4 have high adhesion strength to concrete and high shear rigidity due to the protrusions at the base portion 51 and tip portion 52 (parts that bulge outward relative to the intermediate portion 53), and the nodal protrusions 54 on the intermediate portion 53. Compared to conventional headed stud dowels 75 (see Figures 12 and 13), sufficient shear resistance can be ensured with a compact cross-section. Therefore, even when the column cross-section is small, the shear stoppers (protruding ribs 5) can be efficiently arranged, and the embedding length in concrete can be shortened.

[0024] Furthermore, since the protruding ribs 5 are continuously arranged in the axial direction (vertical direction) of the column with respect to the steel plate of the cylindrical section 2, a stiffening effect can be expected from the protruding ribs 5, and therefore, buckling can be prevented even when the base material (each side of the cylindrical section 2, etc.) is a thin plate. In addition, because the protruding ribs 5 can partially bear the sectional force of the base material (reducing the sectional force borne by the base material), it becomes possible to use a thinner base material compared to conventional composite columns, thereby reducing the amount of steel used as raw material and the material cost.

[0025] More specifically, when axial force or bending moment acts on the column cross-section, buckling deformation may occur in the base material subjected to compression. Conventionally, to prevent buckling, stiffeners (e.g., plate ribs) are attached to the inner and / or outer surfaces of the base material to improve buckling resistance. However, when stiffeners are attached to the inner surface of conventional composite column steel members 71 as shown in Figures 12 and 13, the mounting positions of headed stud dowels 75 (slip guards) may be limited (for example, to positions between multiple stiffeners placed at intervals), and if the cross-section is narrow, it becomes difficult to install the required number of dowels.

[0026] In the steel material 1 for composite columns of this embodiment, the protruding ribs 5 are arranged in a continuous shape along the axial direction (vertical direction) of the column, and have the functions of both a shear prevention mechanism and a stiffening mechanism. Therefore, the above-mentioned problems do not occur, and the protruding ribs 5 have high rigidity (approximately 1.6 times that of a typical plate rib) due to the protrusions at the base end 51 and the tip end 52 (the part that bulges outward relative to the intermediate part 53). As a result, a sufficient stiffening effect can be obtained with a compact cross-section.

[0027] Furthermore, when the height of the protruding rib 5 (the dimension of protrusion from the outer surface 21 or inner surface 22 of the side of the cylindrical part 2, or from the side surface 41 of the cross part 4) is "H" and the vertical installation length is "L", it is effective to set the dimensions of the protruding rib 5 such that the L / H value is 1.5 or more (that is, the ratio of the installation length L to the height H of the protruding rib 5 is 1.5 or more). This point will be explained below.

[0028] Due to the adhesive force between the concrete and the protruding rib 5, a shear force acts on the joint between the protruding rib 5 and the base material (cylindrical section 2 or cross section 4). The center of action of this total shear force is thought to be at the intermediate height position (H / 2) of the protruding rib 5 (see Figure 8), and in this case, the bending deformation δ b And, shear deformation δ s The sum of these factors equals the deformation δ of the protruding rib 5. In other words, the protruding rib 5 undergoes the deformation shown in the following equation (Equation 1).

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[0029] In the above equation, "I" is the stiffness (I=t·L). 3 / 12), where "A" is the area (A=t·L), "E" is the Young's modulus of the steel, "G" is the shear modulus of the steel (E=2.6G), and "P" is the applied load. Also, "t" is the plate thickness of the middle part 53 of the protruding rib 5. Transforming the above equation (Equation 1) using these values, we obtain the following equation (Equation 2).

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[0030] Figure 9 is a graph showing the relationship between the ratio of the installation length L to the height H of the protruding rib 5 (L / H) and the term in parentheses in "Equation 2" above. As is clear from this graph, when the value of L / H is set to less than 1.5, the deformation increases rapidly. Therefore, it is effective to set the value of L / H to satisfy the following equation (Equation 3).

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[0031] Furthermore, regarding the protruding rib 5, as shown in Figure 10, when the width of the nodal protrusion 54 is "B" and the total throat thickness of the welded portion 56 (fillet weld) is "t", it is effective to set the dimensions such that the value of B / t exceeds 5 (that is, the ratio of the width B of the nodal protrusion to the total throat thickness t of the welded portion of the protruding rib exceeds 5). This point will be explained below.

[0032] The shear force transmitted by the adhesion force between the projection 54 and the concrete is transmitted to the base material (cylindrical section 2 or cross section 4) by the shear stress of the welded joint 56 of the projection rib 5. If the adhesion stress of the concrete is less than the shear stress of the welded joint 56 of the projection rib 5, the concrete around the projection 54 will be damaged. Conversely, if the adhesion stress of the concrete is greater than the shear stress of the welded joint 56 of the projection rib 5, the welded joint 56 will shear yield. For seismic resistance, a ductile failure mode is required for the structure, and it is desirable that the shear yield stress of the welded joint 56 of the projection rib 5 precedes the failure of the concrete around the projection rib 5.

[0033] The ultimate bond strength of the protruding rib 5 is given by the following equation (Equation 4), based on the tensile test results of the rib.

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[0034] Furthermore, the yield strength of the welded joint 56 is given by the following equation (Equation 5).

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[0035] Furthermore, in the above equations (equations 4 and 5), "F c " is concrete strength, "F s " is the steel strength, "B" is the width of the projection 54, "L" is the installation length of the projection rib 5, "t" is the total throat thickness of the welded joint 56, and "α" is the safety factor (2 / 3 for short term, 1 / 3 for long term).

[0036] The relationship between the allowable bond stress of the concrete and the allowable shear stress of the welded joint 56 can be expressed by the following equation (Equation 6).

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[0037] Transforming the above equation (Equation 6), we obtain the following equation (Equation 7).

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[0038] Assuming an earthquake load and adopting a short-term limit value (α=2 / 3) as the safety factor, the following equation (Equation 8) is obtained.

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[0039] As for steel materials, SN400(F s = 235 N / mm 2 When using ), the maximum value of the relationship (B / t) between the width B of the nodal projection 54 of the projection rib 5 and the total throat thickness t of the welded part 56 is as shown in the graph on the left side of Figure 11. Therefore, it is effective to set the value of B / t to satisfy the following equation (Equation 9).

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[0040] As for steel materials, SN490(F s = 325 N / mm2 When ), the maximum value of the relationship (B / t) between the width B of the nodal projection 54 of the projecting rib 5 and the total throat thickness t of the welded portion 56 is as shown in the graph on the right side of FIG. 11, it is effective to set the value of B / t so as to satisfy the following formula (Equation 10).

Numbered Equation

[0041] Incidentally, in FIGS. 1 to 5, the steel material 1 for forming a built-in column is exemplified as the steel material for a composite column according to the present invention. However, the composite column to which the present invention is applied is not limited to a built-in column, and the present invention can be applied to any type of composite column configured by integrating steel material and concrete, such as root-wrapped pedestal columns, pile heads, and CFT columns. Further, the tubular portion 2 is not limited to a square tubular shape having a square horizontal cross-section as shown in FIG. 2, and can also be applied to a square tubular shape having a rectangular horizontal cross-section and a cylindrical shape having a circular horizontal cross-section.

[0042] Furthermore, in the above embodiment, the projecting ribs 5 are attached to the outer side surface 21 and the inner side surface 22 of the side portion of the tubular portion 2, but they may also be attached only to the outer side surface 21 or only to the inner side surface 22. In addition, in the above embodiment, one upper projecting rib 5A is arranged on each of the outer side surface 21 and the inner side surface 22 of each side portion of the tubular portion 2, but a necessary number (for example, two or more) can be arranged according to the size (cross-section) of the column or the like.

Description of Symbols

[0043] 1: Steel material, 2: Tubular portion, 21: Outer side surface, 22: Inner side surface, 23: Slit, 24: Corner portion, 3: Bottom portion, 4: Cross portion, 41: Side surface, 42: Outer end, 43: Re-entrant corner, 5, 5A to 5D: Projecting rib, 51: proximal end; 52:Tip, 53: Middle section, 54: Articular process, 55: Tapered section, 56: Welded joint, 71: Steel material, 75: Headed stud dowel,

Claims

1. A steel material for a composite column having a cylindrical portion and a protruding rib, The protruding ribs are welded and fixed so as to protrude outward from the outer surface of the side of the cylindrical portion and / or protrude inward from the inner surface, and so as to extend in the axial direction of the column. The projection rib has a base end that is joined to the side of the cylindrical part, a tip on the opposite side, and an intermediate part between them. The base, tip, and intermediate sections extend in the axial direction of the column. The base and tip portions have a greater thickness than the middle portion and have a shape that bulges outward more than the middle portion. Tapered sections are formed at the boundaries between the base end, the tip end, and the intermediate section. A steel material for composite columns, characterized in that nodal protrusions are arranged on both sides of the intermediate section, extending horizontally from the tapered section at the base end to the tapered section at the tip end, and arranged in parallel with spacing in the vertical direction.

2. The steel material for a composite column according to claim 1, characterized in that the dimensions are set such that the ratio of the installation length to the height of the protruding rib is 1.5 or more.

3. The steel material for composite columns according to claim 1, characterized in that the dimensions are set such that the ratio of the width of the nodal projection to the total throat thickness of the welded portion of the protruding rib exceeds 5.

4. It further comprises a bottom portion that closes the lower opening of the cylindrical portion, and a cross portion positioned on the bottom portion, which is formed by joining four steel plates so that their horizontal cross-section is cross-shaped. The steel material for a composite column according to claim 1, characterized in that the protruding ribs are welded and fixed to the side surface of the cross section in a direction that extends in the axial direction of the column.

5. A composite column characterized by being formed of a steel material for composite columns according to any one of claims 1 to 5, and concrete cast on the inside and / or outside of its cylindrical portion.

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