JP3690247B2 - H-shaped steel with protrusion - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projecting H-shaped steel used when a civil engineering or building structure is constructed with a composite structure of a steel material and a solidified material with time.
[0002]
[Prior art]
In the case of a composite structure in which steel and a solidified material over time (concrete, mortar, soil cement, etc. are often used in civil engineering and building structures, these are represented by concrete) are combined in the cross section. It is desirable that the steel material and the concrete are integrated from the viewpoint of performance and deformability.
[0003]
However, when using shape steel as a steel material, ordinary steel has poor adhesion performance compared to deformed reinforcing bars, so if the external force acting on the structure increases, the gap between the shape steel and concrete increases, and only mechanical performance is achieved. In other words, there is a problem that the crack durability is lowered.
[0004]
As a technique for solving the above-mentioned problems, Japanese Utility Model Publication No. 56-54245 discloses adhesion strength by setting the contact area between the steel frame and the concrete to 8 to 20 times the total projected area in the shear direction of the protrusions, and A steel frame having improved deformability with respect to adhesion is described.
[0005]
[Problems to be solved by the invention]
However, within the scope of the technique disclosed in the above publication, the projection distribution ratio between the flange surface and the web surface of the H-shaped steel is actually unbalanced, and when used as an axial steel material such as a column member, the H-shaped steel There is a problem that the axial stress distribution in the cross section of the steel becomes non-uniform, and the load bearing performance and adhesion performance that should be originally obtained by integrating the H-shaped steel and the concrete are lowered.
[0006]
The present invention is for projection with H-beams for use as an axial steel embedded in concrete, a uniform axial stress distribution in the steel section, including aging hardening material such as concrete on the side which receives the force due to adhesion transfer The purpose is to improve the load bearing performance and adhesion performance.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 of the present application is a H-shaped steel with projections that is used by embedding in a solidified material as a member axial direction steel material in a composite structure, and is provided with a plurality of projections on the flange outer surface and both surfaces of the web. In the H-shaped steel with protrusions, the total sum of the cross-sectional areas of the flange portions is A _f , the cross-sectional area of the web portions is A _w , and the projection of each protrusion in the longitudinal direction of each protrusion with respect to each of the flange portion and the web portion within a certain length When the total area is expressed as a _f and a _w respectively,
a _f / a _w = α (A _f / A _w )
0.7 ≦ α ≦ 1.3
It is characterized by having become.
[0008]
When embossed steel is embedded in concrete and bonded by adhesion, if the concrete is at a stress level that does not cause adhesion failure, the adhesion strength, which is the resistance to the deviation between both, and the adhesion stress divided by the adhesion area is It is known that it increases in proportion to the amount of deviation.
[0009]
Also, when using steel materials with different projection shapes such as height and spacing, or when the adhesion area of the steel materials is different, the adhesion force is known to increase in proportion to the total projection projection area in the displacement direction. Yes.
[0010]
The present invention has taken into account these points, directed to H-shaped steel having a protrusion on the flange outer surface and the web both surfaces APPLICATIONS of that is an axial steel in composite structure.
[0011]
In addition, here, a steel material in which a plurality of members are discretely arranged in the member cross section is mainly assumed, and a state in which a tensile force or a compressive force acts as an axial force is assumed.
[0012]
The basic concept of the present invention is that, in an H-shaped steel having protrusions on the outer surface of the flange and on both sides of the web, the projected area ratio a _f / _aw of the flange and web and the cross-sectional area ratio A _f / A _{w of the} flange and web are The protrusion is arranged so as to satisfy the relationship of the following formula.
[0013]
0.7 ≦ α = (a _f / a _w ) / (A _f / A _w ) ≦ 1.3 (1)
here,
a _f : Sum of projected areas in the longitudinal direction of protrusions on the flange outer surface obtained for a certain length of H-section steel a _w : Longitudinal direction of protrusions on both sides of the web determined for a certain length of H-section steel Of total projected area A _f : Sum of effective area of H-section steel flange (excluding protrusions)
A _w : Effective sectional area of H-shaped steel web part (including fillet) (excluding protrusions)
This eliminates the problem of bias of axial stress in the cross section of the shaped steel that occurs when the shaped steel with protrusions is used as the axial steel material of the composite structure.
[0014]
When using H-shaped steel with protrusions as an axial steel material with a composite structure, the adhesion performance is high. It is desirable that there is no bias in the axial stress distribution.
(1) The upper limit of the load bearing capacity of the H-shaped steel with protrusions that receives axial force can be calculated as the total plastic axial force of the H-section steel cross section. If the axial stress in the cross section is uneven, the total plastic axial force Before reaching, some area in the cross section becomes plastic, and the H-section steel does not show elastic behavior. This apparently corresponds to a decrease in yield strength and yield point of the H-section steel.
(2) Furthermore, it is known that the bond strength decreases significantly in the vicinity of the yielded steel (Island, Shu, Okamura: Bond characteristics of deformed bars after yielding, JSCE Proceedings, 378 / V-6, pp 213-220, 1987). From this, if the steel material partially yields as shown in (1), the relative deviation between the concrete and the steel material increases rapidly. Also, a problem related to adhesion performance that the fixing strength of the H-shaped steel is lowered is expected.
[0015]
On the other hand, the cause of the bias in the axial stress generated in the cross section of the H-section steel with protrusions embedded in the concrete is that the flange and web cross-sectional area ratios A _f / A _w which are constituent elements of the H-section steel, It can be mentioned that there is a large gap between the projected area ratios a _f / _aw of the flange and web. To eliminate the bias of axial stress, A _w / A _f and a _f / a _w should be close to each other. good.
[0016]
The reason for this will be described with reference to the models shown in FIGS. When the axial force acting on the protruding portion is P, the axial force of two flanges is N _f , and the axial force of the web is N _w , the following relationship is established.
[0017]
P = N _f + N _w (2)
The axis z is taken in the embedding direction of the H-shaped steel, the average axial stress of the flange at the position of the depth z is represented by σ _f (z), and similarly the average axial stress of the web is represented by σ _w (z). The state in which the stress distribution in the cross section of the H-section steel is uniform for an arbitrary depth is represented by the following equation.
[0018]
σ _f (z) = σ _w (z) (3)
The axial forces N _f and N _{w of the} protrusion and the average axial stress are expressed as follows. Here, A _f and A _w are the cross-sectional areas of the flange (for two sheets) and the web, respectively.
[0019]
N _f = A _f · σ _f (0) (4)
N _w = A _w · σ _w (0) (5)
The fact that the stress distribution of the H-section steel cross section of the protrusion is uniform
σ _f (0) = σ _w (0)
In view of this, when σ _f (0) and σ _w (0) are eliminated from the equations (4) and (5), the following relationship is obtained.
[0020]
N _f / N _w = A _f / A _w (6)
Next, consider the embedded portion. As described above, the adhesion of the steel material with protrusions increases in proportion to the amount of deviation and the projected area of the protrusions. Therefore, in the embedded portion, the sum of the adhesive forces generated on the outer surfaces of the two flanges is F _f , the adhesive force generated on both surfaces of the web is F _w , the amount of H-shaped steel extracted is δ, the projected area of the flange protrusion is a _f , and the web protrusion If the projected area is expressed as a _w , the following relationship is derived.
[0021]
F _f = β · a _f · δ (7)
F _w = β · a _w · δ (8)
Here, β is a proportional coefficient, and is related to the strength of concrete and the binding pressure of concrete. The value of β can be specified from an adhesion experiment or the like.
[0022]
From the equations (7) and (8), the following relationship is obtained.
_Ff / _Fw = _af / _aw ... (9)
Next, from FIG. 2, when considering the balance of force for each of the flange and web, which are constituent elements of H-section steel,
N _f / 2 = F _f / 2-S (10)
N _w = F _w + 2S (11)
S in the equations (10) and (11) is a shearing force generated at the connection portion between the flange and the web.
[0023]
Here, in order for Formula (3) to be satisfied over the entire embedded length of the H-section steel, shear stress must not occur in the cross section regardless of the depth z, so S = 0 must be satisfied. is there.
[0024]
When S = 0, the following relationship is derived from the equations (6), (9), (10), and (11).
α = (a _f / a _w ) / (A _f / A _w ) = 1 (12)
From the above, conditions for uniforming the axial stress distribution in the H-section steel cross section were derived for an arbitrary depth.
[0025]
Expression (12) represents the most ideal state, and corresponds to the case where the axial stresses of the flange and the web completely coincide with an arbitrary depth z. Further, as α is away from 1, the shearing force S generated at the connecting portion between the flange and the web increases, and the difference between the average axial stress of the flange and the average axial stress of the web increases.
[0026]
Equation (12) represents an ideal state, but unless the shearing force generated at the connecting portion of the flange and the web is not so great, the bias of the axial stress distribution in the H-section steel section does not become so large.
[0027]
In addition, it is common that the lateral restraint bars are placed in the concrete surrounding the H-section steel, but depending on the method of the lateral restraint reinforcement, the degree of restraint of the concrete against the H-section steel may be different from that of the flange surface. It may be slightly different on the web. In the present invention, Equation (1) is determined as a practical range of α in consideration of the anisotropy of the amount of lateral constraint muscle.
[0028]
Further, in order to clarify the difference between the H-shaped steel with projections of the present invention and the conventional H-shaped steel with projections represented by the formula (1), A _f / A _w and a FIG. 3 shows the result of _obtaining the relationship of _f / _aw and comparing it with the scope of the present invention.
[0029]
In the figure, the plots of ◯, □, and △ are conventional H-shaped steel with protrusions, but A _f / A _w and a _f / a _w were estimated in the following manner for those with unclear cross-sectional dimensions.
(1) A _w / A _f was calculated for each size (wide series, medium width series, narrow series) of normal H-section steel without protrusions.
(2) For each size selected in (1) above, a _f / a _w = b _f / b _w . However, b _f is the flange width, b _w is a length obtained by subtracting twice the flange thickness from H-shaped steel overall height, the double fillet size.
[0030]
From FIG. 3, the conventional H-shaped steel with protrusions greatly deviates from the range of α of the present invention indicated by the solid line, and it has already been described only by changing the outer diameter dimension and thickness of the H-shaped steel. It is clear that the axial stress bias in the H-section steel cross section cannot be solved.
[0031]
The butt Okoshizuke H-shaped steel, the web thickness of the H-shaped steel is included when it is the flange thickness or more.
[0032]
Claim 2 is the H-shaped steel with protrusions according to claim 1, wherein the protrusions are linear protrusions continuous in the longitudinal direction of the steel material or dotted protrusions arranged at substantially equal intervals in the longitudinal direction of the steel material. The case where the steel material longitudinal direction interval of the web double-sided projection is wider than the steel material longitudinal direction arrangement interval of the flange outer surface projection is limited.
[0033]
In addition, this linear protrusion includes what was divided | segmented into plurality by the steel material longitudinal orthogonal direction other than what was continued in the steel material longitudinal orthogonal direction.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 4 shows one embodiment of the H-shaped steel with projections of the present invention. The H-shaped steel 1 with protrusions in FIG. 4 has a linear protrusion 3 on the outer surface of the flange, and the linear protrusion 3 is provided over the entire width of the flange.
[0037]
Moreover, the linear protrusion 3 is provided also on both surfaces of the web. The arrangement interval of the linear protrusions 3 in the longitudinal direction of the shape steel is changed between the flange surface and the web surface so as to satisfy the relationship of the formula (1).
[0038]
The H-shaped steel 1 with protrusions shown in FIG. 5 is a modification of the one shown in FIG. 4, and the linear protrusions 3 are replaced with square protrusions.
[0039]
FIG. 6 shows an example in which the relationship of the formula (1) is satisfied and the thickness of the web is increased to make it thicker than the flange.
[0040]
Usually, in order to secure the bending strength by increasing the moment of inertia of the H-section steel, most of the web plate thickness is smaller than the flange plate thickness. The web plate thickness may be larger than the flange plate thickness. In this case, by increasing the thickness of the web, the cross-sectional area of the entire H-section steel 1 can be increased, and the amount of protrusion imparted to the web can also be increased.
[0041]
FIG. 7 shows an example in which the projection spacing ratio in the longitudinal direction of the shape steel is the same for the flange and the web, and the projection projected area ratio is adjusted by the projection width of the flange outer surface and the both surfaces of the web in order to satisfy the formula (1).
[0042]
When adjusting the protrusion width, the protrusion width may be too small compared to the plate width. In such a case, it is preferable to divide the protrusion 3 and disperse it in the plate width direction. Further, as a secondary usage between the protrusions 3 in FIG. 7, for example, it is possible to melt stud studs in this portion. In the case of adding a stud gibber to the adhesion surface, the stud gibber suppresses separation between the steel material and the concrete, so that there is an effect that the deformability of adhesion is improved.
[0043]
FIG. 8 shows an example in which the protrusion arrangement of the narrow H-shaped steel is optimized by the equation (1). The present invention can be applied regardless of the dimensions and outer shape of the H-section steel 1.
[0044]
In addition, it is preferable that the height of the protrusion 3 provided on the surface of the H-shaped steel with protrusion 1 according to the present invention illustrated in FIGS. 4 to 8 is 2.0 mm or more.
[0045]
In general, the relationship between the protrusion height h of the steel material with protrusions and the protrusion disposition interval p in the direction of action of the adhesion force is often set to about 10 or more in order to ensure toughness related to adhesion. In this case, if the height of the protrusion is 2.0 mm or more, the distance between the protrusions can be secured to 20 mm or more, and it becomes easy to attach an auxiliary member such as a stud gibber or a metal fitting for transportation between the protrusions. . Therefore, from this point, it is more preferable that the height of the protrusion 3 is 2.0 mm or more for both the outer surface of the flange and the both surfaces of the web.
[0046]
FIG. 9 shows an embodiment in which the H-shaped steel 1 with projections of the present invention is applied to a composite structural member. Since the H-shaped steel 1 with protrusions of the present invention is suitable for use as an axial steel material, the load carrying performance of the pier 4 can be enhanced particularly when used for a pier 4 having a large cross-sectional dimension, There is also an advantage that the work of reinforcing bars is reduced in terms of construction.
[0047]
In FIG. 9, reference numeral 2 denotes concrete (hatching is omitted), 5 is a main reinforcing bar, 6 is a belt reinforcing bar (lateral restraint), 7 is an intermediate belt reinforcing bar (lateral restraint), and 8 is a hollow portion.
[0048]
【The invention's effect】
By setting the protrusion arrangement of the H-shaped steel having protrusions on the flange outer surface and the web both sides within the range specified in the present invention, it is possible to eliminate the bias of the axial stress distribution that occurs in the H-shaped steel cross section. It is possible to prevent the load resistance performance and adhesion performance of the H-section steel from being deteriorated due to the uneven distribution.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a balance of forces when a protruding H-shaped steel embedded in concrete receives a pulling force.
FIG. 2 is an explanatory diagram showing balance of individual forces of a flange portion and a web portion when a protruding H-shaped steel embedded in concrete receives a pulling force.
FIG. 3 is a graph showing the relationship between the cross-sectional area ratio of the flange and web and the projected area ratio of the present invention and the conventional example.
FIGS. 4A and 4B show an embodiment of an H-shaped steel with protrusions according to the present invention, in which FIG. 4A is a side view and FIG. 4B is a front view.
FIGS. 5A and 5B show another embodiment of the H-shaped steel with projection according to the present invention. FIG. 5A is a side view and FIG. 5B is a front view.
6A and 6B show still another embodiment of the H-shaped steel with projection according to the present invention, in which FIG. 6A is a side view, and FIG. 6B is a front view.
7A and 7B show still another embodiment of the H-shaped steel with projection according to the present invention, in which FIG. 7A is a side view, and FIG. 7B is a front view.
FIG. 8 shows still another embodiment of the H-shaped steel with protrusions of the present invention, in which (a) is a side view and (b) is a front view.
FIG. 9 is a horizontal cross-sectional view when the H-shaped steel with protrusions of the present invention is applied to a hollow type pier column.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... H-section steel with protrusion, 2 ... Concrete, 3 ... Protrusion, 4 ... Pier, 5 ... Main reinforcement, 6 ... Reinforcement bar (lateral restraint), 7 ... Intermediate reinforcement (lateral restraint), 8 ... Hollow part

Claims (2)

In the H-shaped steel with projections, which is used by embedding in the solidified material with time as the member axial steel material in the composite structure, the H-shaped steel with projections provided with a plurality of projections on the flange outer surface and both surfaces of the web, The sum of the cross-sectional areas is A _f , the cross-sectional area of the web portion is A _w , and the sum of the projected areas in the longitudinal direction of the projections of the projections with respect to each of the flange portion and the web portion within a predetermined length is a _f , a When expressed as _w
a _f / a _w = α (A _f / A _w )
0.7 ≦ α ≦ 1.3
H-shaped steel with protrusions, characterized in that The projection is a steel longitudinal direction perpendicular to the continuous linear projection or arranged point-like projections at substantially equal intervals in the steel longitudinal direction perpendicular, steel web sided protrusions than steel longitudinal arrangement interval of the flange outer surface projections claim 1 Symbol placement of H-beams with the projection, wherein the longitudinal spacing is wide.

Images