US20060248840A1

US20060248840A1 - Section steel and wall body using the section steel

Info

Publication number: US20060248840A1
Application number: US10/547,984
Authority: US
Inventors: Kunihiko Onda; Yuichi Tatsumi; Yasushi Wakiya; Akira Yamaguchi; Takeshi Ishizawa; Atsushi Takeda; Mitsuo Higashino; Jyunichi Hirao; Toshinobu Kawakami
Original assignee: JFE Steel Corp; Obayashi Corp
Current assignee: JFE Steel Corp; Obayashi Corp
Priority date: 2003-03-18
Filing date: 2004-03-17
Publication date: 2006-11-09
Also published as: JP2005098059A; WO2004083533A1; KR100752618B1; CN100439606C; CN1745219A; KR20050109991A; TW200500537A; EP1605102A1; EP1605102A4; JP4278149B2; TWI271465B

Abstract

An object of the present invention is to obtain a shaped steel beam having a strong bonding force with respect to concrete, and to obtain a wall with a reduced thickness. An H-beam has a plurality of projections on an inner face, and satisfies the conditions P/h≦10 and P/b₂≧4, where b₂represents the upper-side width of the projections, h represents the projection height, and P represents the projection pitch in a cross section perpendicular to the inner face having the projections. A wall uses the H-beam as a structural member. In the wall, H-beams stand at a plurality of positions in the longitudinal direction of the wall with outer faces of flanges pointing toward the surface of the wall.

Description

TECHNICAL FIELD

The present invention relates to a shaped steel beam that is applicable to the fields of civil engineering and construction, and to a wall using the shaped steel beam.

BACKGROUND ART

As a composite steel-concrete structure, for example, projections are provided on the surface of an H-beam, and concrete is provided around the H-beam. As such an H-beam with projections, an H-beam having projections on inner faces of flanges is known (for example, Japanese Examined Patent Application Publication No. 1-55042).
As a wall using shaped steel beams as core materials, for example, an SRC wall using H-beams 101 is known, as shown in FIG. 27. The wall shown in FIG. 27 includes horizontal reinforcements 104 extending on both sides of concrete 103 in the horizontal direction of the wall, and main reinforcements 105 extending in the vertical direction of the wall so as to cross the horizontal reinforcements 104. H-beams 101 are provided in the center of the wall.
While the concrete 103, the horizontal reinforcements 104, and the main reinforcements 105 are combined to constitute a steel-concrete structure in this wall, the H-beams 101 and the concrete 103 are not bonded and combined.

DISCLOSURE OF INVENTION

The above patent document 1 mentions only that it is preferable to provide projections on inner faces of the H-beams in order to increase the bonding force to concrete, but does not disclose what projections should be provided and how to arrange the projections in order to increase the bonding force to concrete. By study, the present inventor found that, even when projections are provided on inner faces of a shaped steel beam, a sufficient bonding force cannot always be obtained depending on the size and arrangement of the projections.
Accordingly, a first object of the present invention is to obtain a shaped steel beam that provides a strong bonding force to concrete by specifying the size and arrangement of projections.
In the wall shown in FIG. 27, the horizontal reinforcements 104, the main reinforcements 105, and the concrete 103 constitute the steel-concrete structure, and a fixed amount of concrete 103 needs to be disposed around the horizontal reinforcements 104 and the main reinforcements 105. For this reason, a predetermined distance B10 in FIG. 27 is necessary, and as a result, the thickness A10 of the wall is increased.
In the fields of civil engineering and construction, the thicknesses of underground walls and structural walls of buildings have recently been reduced in order to increase an effectively usable area. However, in the wall shown in FIG. 27, it is difficult to reduce the thickness of the wall while maintaining the bearing force of the wall.
Accordingly, a second object of the present invention is to obtain a wall having a reduced thickness.
(1) In order to increase the bonding force to a shaped steel beam, an aspect of the present invention relates to a shaped steel beam having a plurality of projections on an inner face, and satisfying the following expressions:
P/h≦10 and P/b₂≧4
where b₂represents the upper-side width of the projections, h represents the projection height, and P represents the projection pitch in a cross section perpendicular to the inner face having the projections.
Grounds for the above expressions will be described below. Grounds for P/h≦10 will be described first, and grounds for P/b₂>4 will be described next.
(a) Grounds for P/h≦10
FIGS. 18(a) and 18(b) show examples of cross sections of projections perpendicular to a face of a shaped steel beam on which the projections are provided. FIG. 18(a) shows a projection of trapezoidal cross section, and FIG. 18(b) shows a projection of rectangular cross section.
In order to achieve strong bearing force and high rigidity in a steel-concrete structure, it is essential to obtain a composite structure of steel and concrete so that the steel and concrete bear acting external force in a well-balanced manner. The composite structure of steel and concrete means a structure that allows stress to be distributed between steel and concrete. For that purpose, a sufficient bonding force (performance) is required between the steel and concrete.
The above-described bonding force between a shaped steel beam with projections and concrete is produced by biting between the projections provided on the inner face of the shaped steel beam, and concrete, and depends on bearing failure τ₁or shear failure τ₂of the concrete. Herein, the bearing failure τ₁refers to the shearing strength determined by the bearing failure of the concrete at the front of the projection, and τ₂refers to the shearing strength determined by the shear failure at an interface surface between the projection and concrete.
The bearing failure τ₁and shear failure τ₂are expressed by the following general model expressions: $\begin{matrix} τ_{1} = \frac{h \times L \times σ_{c}}{P \times L} = \frac{h \times σ_{c}}{P} & (1) \\ τ_{2} = \frac{P \times L \times τ_{c}}{P \times L} = τ_{c} & (2) \end{matrix}$

- P: projection pitch
- h: projection height
- L: projection length (distance from the root to the leading end of the projection)
- σ_c: uniaxial compressive strength of concrete
- τ_c: shearing strength of concrete

As described above, the bonding force depends on τ₁, τ₂. Since a smaller one of τ₁and τ₂bottlenecks the bonding strength between the steel and concrete, it serves as the bonding stress τ_maxbetween the steel and concrete. Therefore, it is necessary to find the bonding stress τ_maxin order to examine the condition for increasing the bonding strength.
In order to find the bonding stress τ_max, it is necessary to compare τ₁and τ₂. For that purpose, the following assumption will be made.
(Assumption 1)
The following expression is assumed as the relationship between the uniaxial compressive strength σ_cand shearing strength τ_cof concrete that is generally used as a construction material (for example, approximating to a design basis):
τ_c−0.1×σ_c (3)
FIG. 19 shows the relationship formed among τ₁and τ₂, and P/h on the above assumption. A smaller one of the failures serves as the bonding stress τ_maxbetween the steel and concrete. Referring to the graph., when P/h is approximately 10 or less, the concrete fracture is given as shear failure (depending on τ₂), and τ_maxdoes not substantially change. In contrast, when P/h is approximately 10 or more, the concrete fracture is given as bearing failure (depending on τ1), and τ_maxremarkably decreases. Therefore, in order to ensure a strong bonding force, it is preferable that the concrete fracture be given as shear failure.
Accordingly, the following expression is satisfied by the projection pitch that ensures a stable bonding stress τ_max, in consideration of variations in the relationship between the uniaxial compressive strength σ_cand shearing strength τ_cof the concrete.
P/h≦10 (4)
(b) Grounds for P/b₂≧4
Shear failure between steel and concrete mainly occurs on a borderline between the concrete and an upper side b₂of a projection (see FIG. 20). In general, the shearing strength increases as the proportion of concrete on the borderline increases (that is, the proportion of the upper side b₂decreases).
The influence of the ratio of the projection pitch P and the projection upper-side width b₂on the shearing strength τ₂between the steel and concrete can be evaluated by the following expression:
τ₂=(P−b ₂)/P·τc (5)
τc: shearing strength of concrete
Expression (5) indicates the shearing strength τ₂in consideration of a decrease in the strength due to the loss of a length of a concrete shear failure face by the projection upper-side width b₂. The product of the concrete shearing strength τc and the rate of loss of the shear failure face length (P−b₂)/P can be expressed by τ₂.
In Expression (5), when τc is transposed to the left side, τ₂/τc=(P−b₂)/P. This relationship is shown in a graph in FIG. 21. FIG. 21 reveals that the shearing strength τ₂rapidly decreases when P/b₂falls below 4.
The relationship between the increment rate (first-order differentiation) of τ₂/τc and P/b₂is shown in FIG. 22. FIG. 22 reveals that the increment rate is saturated when P/b₂is 4 or more.
From the above, the relationship between the projection pitch P and the projection upper-side width b₂needs to satisfy the following expression in order to maintain a stable bonding stress:
P/b₂≧4 (6)
(2) Another aspect of the present invention relates to a shaped steel beam having a plurality of projections on an inner face, and satisfying the following expressions:
2 mm≦h≦50 mm and 4b ₂ ≦P≦10h
where b₂represents the upper-side width of the projections, h represents the projection height, and P represents the projection pitch in a cross section perpendicular to the inner face having the projections.
The projection height h is set to be within the above range for the following reason.
In a case in which the height is smaller than 2 mm, when the concrete is placed in water, as in an underground wall, it is difficult to ensure reliable bonding to the concrete, for example, because of adhesion of impurities, called slime, to the projections and corrosion of the projections. Therefore, the lower limit is set at 2 mm.
In contrast, when the projection height exceeds 50 mm, the probability that the projections will obstruct insertion and pulling up of tremie tubes is increased. Therefore, the upper limit is set at 50 mm.
When projections are formed by rolling, it is preferable that the upper limit of the projection height be 5 mm. In order to form projections having a height of 5 mm or more by rolling, an excessive rolling load is required, and this is not economic. When projections are formed, for example, by welding a steel bar or a square bar, it is preferable that the lower limit of the projection height be 9 mm. When the projection height is less than 9 mm, the welding operation is troublesome and the number of pieces required to be welded is increased. This is not practical.
When the expression 4b₂≦P≦10h for defining the range of the projection pitch P is divided into two and rearranged, P/h≦10 and P/b₂≧4. Grounds for this relationship are as described in the above (1).
(3) A further aspect of the present invention relates to a shaped steel beam having a plurality of projections on an inner face, and satisfying the following expressions:
2 mm≦h≦50 mm and 4b₁≦P≦10h
where b₁represents the lower-side width of the projections, h represents the projection height, and P represents the projection pitch in a cross section perpendicular to the inner face having the projections.
In the above relationship, 4b₁≦P for the following reason. In consideration of the strength of the projections, it is preferable that the relationship between the upper-side width b₂and the lower-side width b₁of the projections satisfy 1≦b₁/b₂. In this case, the lower limit of b₁/b₂is 1. The upper-side width b₂of the projections in 4b₂≦P in the above (2) can be replaced with the lower-side width b₁of the projections. By replacing the upper-side width b₂of the projections in the above (2) with the lower-side width b₁of the projection, 4b₁≦P is obtained.
When the cross section of the projections is rectangular, as shown in FIG. 18(b), b₂=b₁=b.
The projections can be formed, for example, by rolling. In this case, however, the cross section is not always shaped like an ideal trapezoid or rectangle, as shown in FIG. 18(a) or 18(b). For example, when the cross section is substantially shaped like a curved triangle whose height decreases toward the leading end, as in projections shown in FIG. 23, the shape of the cross section sometimes varies from place to place.
In this case, representative values are provided for evaluation, and are applied to the conditional expressions of the present invention described in the above (1) to (3). For example, in the example shown in FIG. 23, the following representative values are provided (see FIG. 24).
(a) projection height h:: height from the projection root (web-side) to a point 1/2L
(L: projection length (distance from the root to the leading end of the projection)
(b) projection width b1: lower side from the projection root (web-side) to the point 1/2L
(c) projection width b2: upper side from the projection root (web-side) to the point 1/2L
(d) projection pitch P: distance between the projection centers from the projection root (web-side) to the point 1/2L
The projection height h is evaluated as the lower side between the projection root (web-side) and the point 1/2L because the effective bearing area (projection area of a side face of the projection) between the concrete and steel is equal to that in a square shape at this point.
The projection widths b1 and b2 and the projection pitch P are thus evaluated because the effective concrete shearing length (the length of concrete between adjacent projections) between the concrete and steel is equal to that in a square shape between the projection root (web-side) and the point 1/2L.
(4) A further aspect of the present invention relates to a shaped steel beam having an H-shape and standing as a structural element of a steel-concrete wall at each of a plurality of positions in a longitudinal direction of the wall with surfaces of webs of adjacent shaped steel beams opposing one another. The shaped steel beam includes a plurality of projections on an inner face of a flange, and satisfies the following expressions:
P/h≦40 and P/b ₂≧4
where b₂represents the upper-side width of the projections, h represents the projection height, and P represents the projection pitch in a cross section perpendicular to the inner face having the projections,.
Among the above numerical restrictions, grounds for P/b₂≧4 are as described in the above (1). Grounds for P/h≦40 will be described below.
The bonding stress τ_maxbetween the steel and concrete in the projections of the H-beam is defined by a smaller one of the strength with respect to the concrete bearing failure (τ₁) and the strength with respect to the concrete shear failure (τ₂). Here, τ₁and τ₂are expressed by the following general model expressions, as described above: $τ_{1} = \frac{h \times L \times σ_{c}}{P \times L} = \frac{h \times σ_{c}}{P} (bearing failure of concrete)$ $τ_{2} = \frac{P \times L \times τ_{c}}{P \times L} = τ_{c} (shear failure of concrete)$
P: projection pitch
h: projection height
L: projection length (distance from the root to leading end of projection)
τc: uniaxial compressive strength of concrete
τC: shearing strength of concrete
When H-beams with projections are actually buried in the concrete to form a wall, they are continuously spaced with their web surfaces opposing one another (see FIG. 25).
Since adjacent H-beams constrain the inner concrete from deformation by their web surfaces and flange faces in this structure, extra strength is provided. Therefore, the bonding stress τ′_maxbetween the steel and concrete actually used is defined as a smaller one of the product α₁·τ₁and the product α₂ τ₂.
α₁: extra coefficient of the strength with respect to the bearing failure because of a constraint effect between the flanges
α₂: extra coefficient of the strength with respect to the shear failure because of the constraint effect between the flanges
When the H-beams are used in the wall, and the extra strength is calculated on the basis of experimental results, the extra coefficients α₁of approximately 10 and α₂of approximately 3 are derived. In order to compare α₁·τ₁and α₂·τ₂, the above-described assumption τc=0.1×σc is made. The relationship between α₁×τ₁and α₂×τ₂obtained on the assumption is shown in FIG. 26.
A smaller one of the values for the failures serves as the bonding stress τ′_maxbetween the steel and concrete. Referring to the above graph, the concrete fracture is given as shear failure (depending on τ₂), and τ′_maxdoes not substantially change when P/h is approximately 42 or less. When P/h is approximately 42 or more, the concrete fracture is given as bearing failure (depending on τ1), and τ′_maxremarkably decreases. Therefore, in order to ensure a strong bonding force, it is preferable to determine the projection pitch so that the concrete fracture is given as shear failure.
From this relationship and in consideration of variations in the relationship between the uniaxial compressive strength σc and shearing strength τc of the concrete, P/h≦40 is set for the projection pitch that achieves a stable bonding stress τ′_max.
(5) A still further aspect of the present invention relates to a shaped steel beam having an H-shape and standing as a structural element of a steel-concrete wall at each of a plurality of positions in a longitudinal direction of the wall with surfaces of webs of adjacent shaped steel beams opposing one another. The shaped steel beam includes a plurality of projections on an inner face of a flange, and satisfies the following expressions:
2 mm≦h≦50 mm and 4b₂≦P≦40h
where b₂represents the upper-side width of the projections, h represents the projection height, and P represents the projection pitch in a cross section perpendicular to the inner face having the projections.
The projection height is set at 2 mm≦h≦50 mm for the reason described in the above (2). When the expression 4b₂≦P≦40h for defining the projection pitch P is divided into two and rearranged, P/h≦40 and P/b₂≧4. Grounds for P/h≦40 are as described in the above (4), and grounds for P/b₂≧4 are as described in the above (1).
(6) A still further aspect of the present invention relates to a shaped steel beam having an H-shape and standing as a structural element of a steel-concrete wall at each of a plurality of positions in a longitudinal direction of the wall with surfaces of webs of adjacent shaped steel beams opposing one another. The shaped steel beam includes a plurality of projections on an inner face of a flange, and satisfies the following expressions:
2 mm≦h≦50 mm and 4b₁≦P≦40h
where b2 represents the lower-side width of the projections, h represents the projection height, and P represents the projection pitch in a cross section perpendicular to the inner face having the projections.
The projection height h is set at 2 mm≦h≦50 mm for the reason described in the above (2). Further, 4b₁≦P≦40h is obtained by replacing the upper-side width b₂of the projections in the above (5) with the lower-side width b₁, and grounds for the replacement are as described in the above (3).
(7) In the shaped steel beam described in the above (1) to (6), a bonding-force increasing means is provided on a surface of a web.
The bonding-force increasing means provided on the web surface may be a projection or a recess. When the means is a projection, the projection may satisfy the conditions described in the above (1) to (6), or may not satisfy the conditions. In any case, the bonding-force increasing means provided on the web surface can increase the bonding force in correlation with the projections provided in the above (1) to (6).
(8) In the shaped steel beam described in the above (1) to (7), the following condition is satisfied:
h≦b₁
where b₁represents the width of lower sides of the projections.
Regarding h≦b₁, when the projection lower-side width b₁is too small, the projections may deform and reduce the effect of preventing displacement of the concrete. Therefore, the width b₁is set to be at least equal to or larger than the projection height h.
The above description is given of the projection lower-side width b₁. When the projection upper-side width b₂is too large, this also reduces the shearing area (reduces the shearing stress) with respect to the concrete. Therefore, it is necessary to impose a certain limitation to the width b₂. However, this limitation does not need to be added because 4b₂≦P is given in the above (2) as the restrictive expression for preventing the shearing stress τ₂from decreasing.
(9) In the shaped steel beams described in the above (1) to (8), the projections are provided on an inner face of a flange and a surface of a web, and the projections provided on the inner face and the web surface are combined.
(10) A still further aspect of the present invention relates to a wall using, as a structural element, the shaped steel beam described in any of the above (1) to (9) the shaped steel beam stands at each of a plurality of positions in the longitudinal direction of the wall with an outer face of a flange pointing toward a surface of the wall.
(11) In the wall described in the above (10), adjacent shaped steel beams are coupled by a coupling member.
(12) In the wall described in the above (10), horizontal reinforcements are provided at a plurality of positions in the height direction of the wall so as to be in contact with the outer faces of the flanges of the shaped steel beams.
(13) In the wall described in the above (12), a main reinforcement is provided between the adjacent shaped steel beams and inside the horizontal reinforcements so as to cross the horizontal reinforcements in contact therewith.
(14) In the wall described in the above (12) or (13), the horizontal reinforcements are fixed to the outer faces of the flanges of the shaped steel beams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and 1(b) are explanatory views of an H-beam 1 with projections according to a first embodiment of the present invention, FIG. 1(a) is a schematic plan view, and FIG. 1(b) is a sectional view taken along line X-X.
FIGS. 2(a) and 2(b) are explanatory views of an H-beam 11 with projections according to a second embodiment of the present invention, FIG. 2(a) is a schematic plan view, and FIG. 2(b) is a sectional view taken along line Y-Y.
FIG. 3 is a schematic plan view of an H-beam 21 with projections according to a third embodiment of the present invention.
FIGS. 4(a), 4(b), and 4(c) are explanatory views of a wall according to a fourth embodiment of the present invention.
FIG. 5 is an explanatory view showing the advantage of the fourth embodiment of the present invention.
FIGS. 6(a) and 6(b) are schematic views showing an example of a wall forming method according to the present invention.
FIGS. 7(a) and 7(b) are explanatory views showing a test for measuring the bonding force of the H-beam with projections in examples, FIG. 7(a) is a side view, and FIG. 7(b) is a front view.
FIG. 8 is a graph showing the advantage of H-beams with projections in Example 1.
FIG. 9 is a graph showing the influence of the projection pitch in Example 2.
FIG. 10 is a graph showing the influence of the projection height in Example 2.
FIGS. 11(a) and 11(b) are explanatory views showing the orientation of the projections in Example 2.
FIG. 12 is a graph showing the influence of the orientation of the projections in Example 2.
FIG. 13 is an explanatory view showing the shape of the projections in Example 2.
FIGS. 14(a), 14(b), and 14(c) are views showing a simulated wall structure in Example 3, FIG. 14(a) is a front view, FIG. 14(b) is a side view, and FIG. 14(c) is a Z-Z sectional view.
FIG. 15 is a graph showing the advantage of the H-beam with projections in the simulated wall in Example 3.
FIG. 16 is an explanatory view of a sample in Example 4.
FIG. 17 is a graph showing the advantage of Example 4.
FIGS. 18(a) and 18(b) are explanatory views showing the cross-sectional shapes of the projections in the present invention.
FIG. 19 is an explanatory view showing grounds for numeric restriction in the present invention.
FIG. 20 is an explanatory view showing shear failure.
FIG. 21 is an explanatory view showing grounds for numeric restriction in the present invention.
FIG. 22 is an explanatory view showing grounds for numeric restriction in the present invention.
FIG. 23 is an explanatory view showing the shape of the projections in the present invention.
FIG. 24 is an explanatory view showing the shape and arrangement of the projections in the present invention.
FIG. 25 is an explanatory view showing a wall structure according to the present invention.
FIG. 26 is an explanatory view showing grounds for numeric restriction in the present invention.
FIG. 27 is a transverse sectional view of a conventional SRC wall.
Reference numerals in the drawings have the following meanings:
1, 11, 21 H-beam with projections
2 projection
3, 31, 32 concrete (solidification soil)
4 horizontal reinforcement
5 main reinforcement
h, h1, h2 projection height
b projection width of projection of rectangular cross section
b1 lower-side width of projection in cross section
b2 upper-side width of projection in cross section
L, L1, L2, L3 projection length: distance from root to leading end of projection
P projection pitch
A1, A2, A3, A10 wall thickness
B1, B2, B3, B10 distance from outer surface of flange to wall surface
H web height
Wf flange width

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment

FIGS. 1(a) and 1(b) are explanatory views of an H-beam 1 with projections according to a first embodiment of the present invention. FIG. 1(a) is a schematic plan view, and FIG. 1(b) is a cross-sectional view taken along line X-X.
In the H-beam 1 with projections of the first embodiment, projections 2 of rectangular cross section are provided at a plurality of positions in the longitudinal direction of the H-beam on four inner faces of flanges so that the longitudinal direction of the projections coincides with the direction of the flange width Wf, as shown in FIGS. 1(a) and 1(b). The projections 2 on the flange inner faces have a projection height h1, a projection width b, and a projection length L1, and are not in contact with the corners defined by the flanges and a web.
Regarding the shape and arrangement of the projections, the projection pitch P is set to be within the range of 4b to 40h1, and the projection height h1 is set to be within the range of 2mm to 50 mm in order to increase the bonding force with respect to concrete or solidification soil. The projections 2 are provided so that the longitudinal direction thereof is parallel to the direction of the flange width Wf.
When the projections 2 are parallel to the flange width direction, the bonding characteristic is similar in the rightward and leftward directions, there is no difference in strength, and stable bonding performance can be achieved. In contrast, when the projections are inclined with respect to the flange width direction, the characteristic may vary depending on the bonding direction. Although projections formed by rolling are shaped to be inclined in one direction, the characteristic rarely varies depending on the bonding direction.

Second Embodiment

FIGS. 2(a) and 2(b) are explanatory views of an H-beam 11 with projections according to a second embodiment of the present invention, FIG. 2(a) is a schematic plan view, and FIG. 2(b) is a cross-sectional view taken along line X-X.
In the H-beam 11 with projections of the second embodiment, projections 2 of rectangular cross section are provided on four inner faces of flanges, in a manner similar to that in the projections 2 of the first embodiment, as shown in FIG. 2, and projections 2A serving as bonding-force increasing means are provided at a plurality of positions in the longitudinal direction of the H-beam on both surfaces of a web so that the longitudinal direction thereof coincides with the height direction of the web.
The projections 2A are provided on both surfaces of the web, and have a projection height h2, a projection width b, and a projection length L2. Both the projections 2 on the flange inner faces and the projections 2A on the web surfaces are out of contact with the corners defined by the flanges and the web. The projection height h2, the projection width b, and the projection length L2 of the projections 2A provided on the web surfaces can be determined independently of the projections 2 on the flange inner faces.
Regarding the shape and arrangement of the projections on the web surfaces, in order to increase the bonding force with respect to concrete or solidification soil, it is preferable that the projection pitch P be set to be within the range of 4b to 40h2, and that the projection height h2 be set to be within the range of 2 mm to 50 mm, in a manner similar to that in the first embodiment.
When most of the required bonding force can be ensured by the projections provided on the flange faces, the projections on the web surfaces may function as auxiliary means for increasing the bonding force. In this case, it is not always necessary to satisfy the above-described shape and arrangement requirements.

Third Embodiment

FIG. 3 is an explanatory view of an H-beam 21 with projections according to a third embodiment of the present invention. In the H-beam 21 with projections of the third embodiment, projections 2 having a projection height h1, a projection width b, and a projection length L1 are provided on four inner faces of flanges, and projections 2B having a projection height h2, a projection width b, and a projection length L3 are provided on web surfaces, as shown in FIG. 3. Both the projections 2 on the flange inner faces and the projections 2B on the web surfaces are in contact with the corners defined by the flanges and the web, and the projections 2B are not provided at the centers of the web surfaces.
The above-described contact with the corners can further increase the bonding force with respect to concrete or solidification soil (composition effect). The projection length L3 of the projections 2B provided on the web surfaces of the H-beam 21 with projections in the third embodiment is set to be smaller than the projection length L2 of the projections 2A provided on the web surfaces of the H-beam 11 with projections in the second embodiment.
The shape and arrangement of the projections, that is, the projection pitch P, the projection width b, and the projection heights h1 and h2 are similar to those in the first and second embodiments.
While the longitudinal direction of the projections 2 is parallel to the flange width direction in the H- beams 1, 11, and 21 with projections in the above-described first to third embodiments, the H-beam with projections according to the present invention can provide a certain bonding force even when the projections are inclined with respect to the flange width direction, as described above.
The projections 2 in the first embodiment may be formed on the flange inner faces by rolling, or cutting a projection material, such as a square bar, a round bar, a deformed bar, or a stud, into pieces of a predetermined length and fixing the pieces onto the flange inner faces. When the projections 2 are made from a projection material, it is preferable, for easy fixing, that the projection material be made of steel. The projections 2A and 2B can be formed in a manner similar to that in the projections 2.

Fourth Embodiment

FIG. 4 is an explanatory view of a wall according to a fourth embodiment of the present invention, showing the horizontal cross section of the wall disposed in a standing manner.
The wall of the fourth embodiment uses the H-beams 1 with projections in the first embodiment as structural elements, as shown in FIG. 4. Only the H-beams 1 with projections are used as structural elements (FIG. 4(a)), horizontal reinforcements 4 are used as structural elements, besides the H-beams 1 with projections (FIG. 4(b)), and vertical reinforcements 5 are further provided as structural elements (FIG. 4(c)).
In the wall shown in FIG. 4(a), since the H-beams 1 with projections has a strong bonding force with respect to concrete or solidification soil, they are combined with the concrete or solidification soil, thereby forming a steel-concrete structure in which the H-beams mainly bear the tensile force and concrete or the like bears the compressive force.
In the conventional case in which the H-beams are not bonded to the concrete (see FIG. 27), it is necessary to form the steel-concrete structure by bonding the reinforcements 104 and 105 to the concrete. In contrast, in this embodiment, there is no need to place the reinforcements 104 and 105 and to surround the reinforcements 104 and 105 by concrete having a thickness more than a predetermined thickness in order to ensure bonding to concrete or the like. Moreover, since the projections are provided on the flange inner faces, it is unnecessary to provide concrete or the like on the outer faces of the flanges in order to ensure bonding to the H-beams 1.
As a result, the distance B1 from the flange outer faces of the H-beams 1 with projections to the wall surfaces can be made smaller than the distance B10 from the flange outer faces to the wall surfaces in the conventional case, and the thickness of the wall can be reduced.
Since the bearing force of the structure itself is increased, the thickness of the wall can also be reduced in this respect.
Since a plurality of H-beams 1 are disposed with the web surfaces opposing one another in the wall of this embodiment, an effect of constraining concrete between the flanges of the H-beams 1 can be expected over the entire width of the wall, and the bonding force can be increased further. That is, in a case in which there is no element adjacent to the H-beam 1, as shown in FIG. 5(a), when concrete cracks, the concrete constrained between the flanges separates in the right-to-left directions in the figure, and the bonding force drastically decreases. In contrast, in a case in which the H-beams 1 are disposed with the web surfaces opposing each other, as shown in FIG. 5(b), concrete provided between the flanges of the H-beams 1 is constrained by the adjacent H-beams 1, and is prevented from separating. For this reason, the bonding force can be maintained, and the bearing force of the wall can be prevented from being reduced.
The maximum bonding stress τ′_max(N/mm²) of the wall, in which a plurality of H-beams 1 with projections stand, with respect to concrete is 2.7 to 25 times as strong as in the case in which concrete is not constrained between the flanges (that is, only one beam with projections is provided).
In the wall using the H-beams 1 with projections as structural elements, when the distance between the centers of the adjacent H-beams 1 is excessively long, the bearing force and rigidity extremely decrease. For example, punching shear failure (a kind of brittle fracture) may occur to the concrete in an underground wall, and the effect of reducing the wall thickness is reduced. Accordingly, it is preferable that the distance between the centers of the adjacent H-beams 1 with projections 1 be 1.0 to 2.5 times as long as the flange width, depending on the force applied to the wall.
When an underground wall is built, preferably, the web height of the H-beams 1 with projections is 600 mm or more, the flange width Wf is 300 mm or more, and the steel yield point is 315 N/mm²or more in order to place tubes, called tremie tubes (generally, having a diameter of 200 mm to 250 mm), between the adjacent H-beams 1 and to sufficiently reduce the wall thickness.
A wall structure shown in FIG. 4(b) will now be described. In the wall, horizontal reinforcements 4 are provided at a plurality of positions in the wall height direction so as to be in contact with the outer faces of flanges of H-beams 1 with projections, as described above. In FIG. 4(b), it is possible to increase the resistance to the bending force orthogonal to the horizontal reinforcements 4 acting on the wall.
In the wall structure shown in FIG. 4(b), the horizontal reinforcements 4 are auxiliary structural elements, and the distance B2 from the flange outer faces to the wall surfaces can be made shorter than that in the case in which the concrete 103 and the reinforcements 104 must be bonded, as shown in FIG. 27.
A wall structure shown in FIG. 4(c) will now be described. In this wall, besides the horizontal reinforcements 4, main reinforcements 5 are provided between the adjacent H-beams 1 with projections so as to be in contact with the inner sides of the horizontal reinforcements 4 and to cross the horizontal reinforcements 4, as described above.
In this wall, it is possible to increase the resistance to the bending force orthogonal to the main reinforcements 5 acting on the wall.
In this wall, since the main reinforcements 5 are provided inside the horizontal reinforcements 4, they do not increase the distance B3 between the flange outer faces and the wall surfaces, and the thickness of the entire wall can be reduced.
When the wall of the fourth embodiment is built, the location accuracy of the H-beams 1 with projections can be increased by coupling the adjacent H-beams.
For example, in the wall structure shown in FIG. 4(a), flat bars are used as coupling members. When the wall is built, flat bars are fixed to the flanges of the H-beams 1 with projections by welding, and the adjacent H-beams 1 are coupled by the flat bars fixed thereto.
When the wall structures shown in FIGS. 4(b) and 4(c) are built, the adjacent H-beams 1 with projections in the steel structure can be coupled by welding the horizontal reinforcements 4 onto the flange faces.
In such a wall in which the adjacent H-beams 1 are coupled by the coupling members or the horizontal reinforcements 4, even when uniform force acts in the longitudinal direction of the wall, for example, unsymmetrical pressure acts on an underground wall, the force can be propagated in the horizontal direction by the coupling members, and the force for constraining the concrete disposed in contact with the web surfaces of the adjacent H-beams 1 with projections and between the flange inner faces can be increased further.
It is more preferable to use appropriate deformed reinforcements as the horizontal reinforcements 4 and the main reinforcements 5 because they can increase the bonding force with respect to the concrete or the like.
While the H-beams 1 with projections in the first embodiment are used as an example in the above fourth embodiment, it is needless to say that a wall can be built by using the H- beams 11 and 21 of the second and third embodiments as structural elements.
When a wall is built by using the H- beams 11 or 21 of the second or third embodiments as structural elements, it can have a stronger bearing force because the bonding force between the H- beams 11 or 21 and the concrete or the like is strong.
Although the method for building the wall of the present invention is not particularly limited, for example, an underground wall can be built, as shown in FIGS. 6(a) and 6(b). First, a retaining wall is formed in the ground, the ground on the side of an in-ground space is dug to the retaining wall, and earth and sand are removed. Subsequently, a plurality of H-beams with projections are placed in a standing manner at intervals in the longitudinal direction of the wall so that the outer faces of the flanges oppose the wall surfaces, thereby forming a steel structure. Then, the steel structure is combined with concrete or solidification soil to form a wall by placing the concrete or solidification soil into a form. After that, the space between the wall having the steel structure in which the H-beams with projections are used as structural elements, and the retaining wall is backfilled to obtain an underground wall.

EXAMPLE 1

Advantages of the present invention were verified with samples shown in FIG. 7 for measuring the bonding force between an H-beam and concrete. The samples include an H-beam 1 having a web height H of 588 mm, a flange width Wf of 300 mm, a web thickness of 12 mm, and a flange thickness of 20 mm, and concrete 31 having a compressive strength σc of 29 (N/mm²) after solidification.
Sample 1 uses an H-beam having no projection on flange inner faces (referred to as a “no-projection H-beam), and Samples 2 to 4 use H-beams 2 with projections. In Samples 2 to 4, the projection pitch P, the projection height h, and the projection width b are as follows:
Sample 2: P=50 mm, P/h=17, and b=12.5 mm
Sample 3: P=100 mm, P/h=33, b=12.5 mm
Sample 4: P=150 mm, P/h=50, b=12.5 mm
The projections 2 of the H-beams 1 with projections used in Samples 2, 3, and 4 were made from a square steel bar as a projection material, and were welded to the H-beams 1. In the test, the concrete was clamped and constrained from both sides by a steel jig.
A load in a direction shown by the arrow in FIG. 7 was imposed on each of the obtained sample, and the concrete slip was detected. In FIG. 8, the horizontal axis indicates the concrete slip (mm), and the vertical axis indicates the average bond stress τ(N/mm²). The average bond stress τ(N/mm²) is a value obtained by dividing the load by the sum(sum=(300−12)×500×2=288000 mm²) of the areas of the inner faces of the flanges in contact with the concrete. The load was imposed by a displacement-controlled push-out monotonic loading method.

Table 1 shows the maximum bonding stresses τ′_maxof the above samples, the ratios of the maximum bonding stresses τ′_maxof the samples to the maximum bonding stress τ′_maxof Sample 1, the maximum loads, and the concrete slips under the maximum loads. Since it is assumed that the allowable concrete slip between the steel and the concrete in the steel-concrete wall is approximately 5 mm, comparisons were made within the range.

	TABLE 1


	Test Results

Specifications of Samples

Maximum

					Compressive	Bonding
		Projection	P/h (h:	P/b (b:	Strength of	Stress	Ratio to	Maximum
Shape of	Sample	Pitch	projection	projection	Concrete	τ′_max	τ′_maxof	Load
Projection	No.	P(mm)	Height)	Width)	σc (N/mm²)	(N/mm²)	Sample 1	(kN)

Comparative	Sample	1	No			29	0.19	1	54
Example		Projection
Invention	Sample
2	50	17	4		4.39	23	1264
Invention	Sample	3	100	33	8		3.82	18	1199
Comparative	Sample	4	150	50	12		2.71	14	780
Example

Table 1 shows that the maximum bonding stresses in Samples 2 to 4 having projections are markedly heavier than in Sample 1 having no projection.
The bonding strength required for the wall structure is 3.0 N/mm². While the maximum bonding stresses in Sample 2 (projection pitch P=50 mm) and Sample 3 (Projection pitch P=100 mm) greatly exceeded 3.0 N/mm², the maximum bonding stress in Sample 4 (projection pitch P=150 mm) was less than 3.0 N/mm².
This reveals that the conditions P/h≦40 and P/b≦4 in the present invention must be satisfied in order to ensure the bonding strength required for the wall structure.
That is, a thinner wall having high bearing force and high rigidity can be achieved by using the H-beams 1 having projections on the flange inner faces according to the present invention.

EXAMPLE 2

A test similar to that in Example 1 was made to examine the bonding characteristics of rolled projections (see FIGS. 11(a), 11(b) and 24). In this example,

Samples

5, 9, and 10 are given according to the present invention, Sample 6 is given as a comparative example to verify the influence of the projection pitch, Sample 7 is given as a comparative example to verify the influence of the projection height, and Sample 8 is given according to the present invention to verify the influence of the projection orientation. In the test, the concrete was clamped and constrained from both sides by a steel jig, in a manner similar to that in Example 1.

	TABLE 2


	Test Results(δ = 5 mm)

Specifications of Samples

Maximum

					Compressive	Bonding
		Projection	projection		Strength of	Stress	Ratio to	Maximum
Shape of	Sample	Pitch	Height		Concrete	τ′_max	τ′_maxof	Load
Projection	No.	P(mm)	h(mm)	P/h	σc (N/mm²)	(N/mm²)	Sample 1	(kN)

Comparative

Sample

1

No

—

29

0.19

1

54

Example		Projection
Invention	Sample
5	50	3	17	29	4.38	23	1242
Comparative	Sample	6	150	3	50	29	2.67	14	756
Example
Comparative	Sample 7	50	1.2	42	29	2.21	12	648
Example
Invention	Sample
8	50	3	17	29	4.69	25	1350
			(opposite)
Invention	Sample 9	50	2	25	29	3.95	21	1126
Invention	Sample	10	50	2.5	20	29	4.01	21	1143

(1) Consideration of Influence of Projection Pitch P

In order to consider the influence of the projection pitch, the relations between the average bond stress (N/mm²) and the concrete slip (mm) in Samples 1, 5, and 6 are shown in FIG. 9.
As shown in FIG. 9, when the concrete slip 6 was 5 mm or less, the maximum bonding stress in Sample 5 (projection pitch P=50 mm) greatly exceeded the bonding strength of 3.0 N/mm²required for the wall structure, and the maximum bonding stress in Sample 6 (projection pitch P=150 mm) was less than 3.0 N/mm². This reveals that it is effective to set the projection pitch of the rolled projections so that P/h≦40 in order to obtain the bonding strength required for the wall structure.
(2) Consideration of Influence of Projection Height h
In order to consider the influence of the projection pitch, the relations between the average bond stress (N/mm²) and the concrete slip (mm) in Samples 1, 5, and 7 are shown in FIG. 10.
As shown in FIG. 10, when the concrete slip δ was 5 mm, the maximum bonding stress in Sample 5 (projection height h=3 mm) greatly exceeded the bonding strength of 3.0 N/mm²required for the wall structure, and the maximum bonding stress in Sample 7 (projection height h=1.2 mm) was less than 3.0 N/mm².
The maximum bonding stresses in Sample 9 (projection height h=2 mm) and Sample 10 (projection height h=2.5 mm) were 3.95 N/mm²and 4.01 N/mm², as shown in Table 2, and exceeded the bonding strength of 3.0 N/mm²required for the wall structure.
The above results reveal that it is preferable that the projection height h for obtaining a predetermined bonding strength be set within the range of the present invention (P/h≦40).
(3) Consideration of Influence of Projection Orientation (Curved Shape)
When curved projections were provided, as shown in FIGS. 11(a) and 11(b), a direction of the projections such that concave faces push out the concrete was designated as a reverse direction (FIG. 11(a), Sample 8), and a direction of the projections such that convex faces push out the concrete was designated as a reverse direction (FIG. 11(b), Sample 5).
In order to consider the influence of the projection orientation (curved shape), the relations between the average bond stress (N/mm²) and the concrete slip (mm) in Samples 5 and 8 are shown in FIG. 12.
As shown in FIG. 12, when the concrete slip δ was 5 mm or less, the maximum bonding stresses in both samples greatly exceeded the bonding strength of 3.0 N/mm²required for the wall structure, and no substantial difference in bonding characteristic was found even when the curved shape of the projections for pushing out the concrete was changed. That is, it is shown that the orientation of the projections (curved shape) does not have a great influence on the bonding characteristic, and that the projections may be oriented in any direction.
When projections are formed by rolling, as in this example, protuberances are sometimes formed at the border between the flange and the web. By inspection of the influence of the protuberances on the bonding force, it was confirmed that at least the protuberances did not reduce the bonding force.

EXAMPLE 3

Projections 2 having a projection height of 3 mm, a projection width of 12.5 mm, and a projection length of 50 mm were provided at a projection pitch P of 50 mm on inner faces of flanges of H-beams having the same cross-sectional size as that in Example 1. The projections 2 of the H-beams 1 with projections on the flange inner faces were made from a square steel bar serving as a projection material, and were placed by welding, as shown in FIGS. 1(a) and 1(b).
On a base shaped like a rectangular parallelepiped, a simulated wall was built with the H-beams 1 having projections on flange inner faces used as structural elements, as shown in FIGS. 14(a), 14(b), and 14(c), and was tested by repeatedly applying a load in the direction shown by the arrow in the figure.
As a result, as shown in FIG. 15, the maximum load with respect to the displacement at a load point in the simulated wall using the H-beams having the projections on the flange inner faces according to the present invention was more than 1.3 times the maximum load of a simulated wall having no projections, and a strong bearing force was provided. Furthermore, the rigidity of the simulated wall using the H-beams having projections on the flange inner faces according to the present invention was more than 1.3 times the rigidity of the simulated wall using the H-beams having no projections.

EXAMPLE 4

Examples 1 to 3 described above demonstrated that a predetermined bonding strength with respect to the push-out force could be ensured.
However, since a bending force and a shearing force prevailingly act on an actual wall, this proof only of performance with respect to the push-out force is insufficient as a proof of performance of the wall.
Accordingly, in this example, the performance of a steel-concrete wall with respect to the bending and shearing force was verified by using a full-size sample.
FIG. 16 is an explanatory view of the sample of this example having a structure in which an H-beam 1 disposed at the center is surrounded by concrete 31. Protective plates 33 are provided at both ends and at the axial center of the sample to protect the concrete 31, the ends are supported, and a load is applied to the axial center. The specifications of the H-beam are similar to those in Example 1, and the specifications of the projections (including a production method and size) and the specifications of the concrete are similar to those in Sample 5 described in Example 2.
The expected performance the steel-concrete wall was obtained by calculation with FEM analysis. As an analytic model, dynamic characteristics of the concrete and the H-beam in the sample model were modeled by a stress-strain curve (nonlinear model) obtained by component tests, and the bonding characteristic at the interface between the concrete and the H-beam was modeled by an interface element based on a push-out bonding test.
As a test, a load was applied to the center of the sample shown in FIG. 16, and deflection at the load point was detected. FIG. 17 is a graph showing the test results. The horizontal axis indicates the deflection (mm) at the load point, and the vertical axis indicates the load (kN).
As FIG. 17 shows, since the test results coincide with calculated values obtained in consideration of the bonding characteristic, it could be confirmed that the steel-concrete wall had the expected performance with respect to the bending and shearing force.

INDUSTRIAL APPLICABILITY

In the present invention, since a plurality of projections are provided on the inner faces of the shaped steel beam and these projections satisfy predetermined numeric requirements, the bonding force with respect to concrete can be increased. As a result, when such a shaped steel beam is used as a structural element of a wall, the thickness of the wall can be reduced.

Claims

1. A shaped steel beam having a plurality of projections on an inner face, and satisfying the following expressions:

P/h≦10 and P/b₂≧4

where b₂represents the upper-side width of the projections, h represents the height of the projections, and P represents the pitch of the projections in a cross section perpendicular to the inner face having the projections.

2. A shaped steel beam having a plurality of projections on an inner face, and satisfying the following expressions:

2 mm≦h≦50 mm and 4b₂≦P≦10h

3. A shaped steel beam having a plurality of projections on an inner face, and satisfying the following expressions:

2 mm≦h≦50 mm and 4b₁≦P≦10h

where b₁represents the lower-side width of the projections, h represents the height of the projections, and P represents the pitch of the projections in a cross section perpendicular to the inner face having the projections.

4. A shaped steel beam having an H-shape and standing as a structural element of a steel-concrete wall at each of a plurality of positions in a longitudinal direction of the wall with surfaces of webs of adjacent shaped steel beams opposing one another, wherein the shaped steel beam includes a plurality of projections on an inner face of a flange, and satisfies the following expressions:

P/h≦40 and P/b₂≧4

5. A shaped steel beam having an H-shape and standing as a structural element of a steel-concrete wall at each of a plurality of positions in a longitudinal direction of the wall with surfaces of webs of adjacent shaped steel beams opposing one another, wherein the shaped steel beam includes a plurality of projections on an inner face of a flange, and satisfies the following expressions:

2 mm≦h≦50 mm and 4b₂≦P≦40h

6. A shaped steel beam having an H-shape and standing as a structural element of a steel-concrete wall at each of a plurality of positions in a longitudinal direction of the wall with surfaces of webs of adjacent shaped steel beams opposing one another, wherein the shaped steel beam includes a plurality of projections on an inner face of a flange, and satisfies the following expressions:

2 mm≦h≦50 mm and 4b₁≦P≦40h

7. The shaped steel beam according to claim 1, wherein bonding-force increasing means is provided on a surface of a web.

8. The shaped steel beam according to claim 1, wherein the following condition is satisfied:

h≦b₁

where b₁represents the lower-side width of the projections.

9. The shaped steel beam according to claim 1, wherein the projections are provided on an inner face of a flange and a surface of a web, and the projections provided on the inner face and the surface are combined.

10. A wall using, as a structural element, a shaped steel beam according to claim 1, wherein the shaped steel beam stands at each of a plurality of positions in the longitudinal direction of the wall with an outer face of a flange pointing toward a surface of the wall.

11. The wall according to claim 10, wherein adjacent shaped steel beams are coupled by a coupling member.

12. The wall according to claim 10, wherein horizontal reinforcements are provided at a plurality of positions in the height direction of the wall so as to be in contact with the outer faces of the flanges of the shaped steel beams.

13. The wall according to claim 12, wherein a main reinforcement is provided between the adjacent shaped steel beams and inside the horizontal reinforcements so as to cross the horizontal reinforcements in contact therewith.

14. The wall according to claim 12, wherein the horizontal reinforcements are fixed to the outer faces of the flanges of the shaped steel beams.

15. The wall according to claim 13, wherein the horizontal reinforcements are fixed to the outer faces of the flanges of the shaped steel beams.

16. The shaped steel beam according to claim 2, wherein bonding-force increasing means is provided on a surface of a web.

17. The shaped steel beam according to claim 3, wherein bonding-force increasing means is provided on a surface of a web.

18. The shaped steel beam according to claim 4, wherein bonding-force increasing means is provided on a surface of a web.

19. The shaped steel beam according to claim 5, wherein bonding-force increasing means is provided on a surface of a web.

20. The shaped steel beam according to claim 6, wherein bonding-force increasing means is provided on a surface of a web.