JP2012202134A - Structure of concrete placing joint surface, and construction method, shear capacity evaluation method and design method for the structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of concrete placing joint surface which can secure high shear stiffness, and a construction method, a shear capacity evaluation method and a design method for the structure.SOLUTION: A structure 100 of the placing joint surface between existing concrete 10 and new concrete 12 successively joined thereto, comprises an inverted cone-shaped concavity 14 provided on an existing concrete front face 10a and an anchor bar 16 of which one end 16a is embedded in the existing concrete 10 through the concavity 14 and the other end 16b is embedded in the new concrete 12.

Description

  The present invention relates to a structure of a concrete joint surface between an existing concrete and a new concrete to be jointed thereto, a construction method of this structure, a shear strength evaluation method, and a design method.

  Conventionally, in seismic retrofitting and the like, it is known to perform the joint surface treatment before placing the new concrete in order to ensure the integrity of the existing concrete and the new concrete that is handed over to the existing concrete ( For example, see Patent Document 1). As a typical joining surface treatment, as shown in FIG. 12, post-construction anchor bars 1 and the like are embedded in existing concrete 2. The shear rigidity and shear strength of the joining surface are exhibited by the dowel effect of the anchor bars, the frictional force, and the like.

  Further, as another structure of the connecting surface, as shown in FIG. 13, a recess 3 is formed on the surface of the concrete 2 immediately after placement by an air bag or the like (not shown), and the projecting member 4 extends from the bottom of the recess 3. A structure for projecting is known (see, for example, Patent Documents 2 and 3). Further, as shown in FIG. 14, a structure is known in which a fixing member 7 having an annular convex portion 6 and an anchor bolt 8 are arranged in a concave portion 5 provided on the surface of an existing concrete 2 (see, for example, Patent Document 4). ).

JP 2009-263156 A JP-A-7-180352 JP-A-7-180353 JP 2010-59717 A

  By the way, in the conventional joint surface of FIG. 12 and the like, once a shear slip occurs, the slip is suppressed to some extent by the dowel effect of post-installed anchor bars, etc., but the apparent shear rigidity is difficult to ensure. There was a problem above. This apparent shear stiffness is defined by the amount of slip, but it is usually difficult to control the bonding force (adhesive force) of the joint surface because it is difficult to control. Quantification of this apparent shear stiffness There was also an aspect that was difficult to evaluate.

  In addition, in order to ensure the integrity between concrete, it is common to roughen the joint surface of existing concrete by chipping, etc., but the cracking occurs in the existing concrete due to the impact of this chipping, etc. There is a problem that solid noise and noise occur during construction.

  The present invention has been made in view of the above, and an object of the present invention is to provide a concrete joint surface structure capable of ensuring high shear rigidity, a construction method for the structure, a shear strength evaluation method, and a design method. And

  In order to solve the above-described problems and achieve the object, the structure of the concrete connection surface according to claim 1 of the present invention is the structure of the connection surface between the existing concrete and the new concrete to be transferred to this. It is characterized by comprising an inverted conical recess provided on the surface of an existing concrete, and an anchor bar having one end embedded in the existing concrete and the other end embedded in the new concrete through the recess.

  Moreover, the construction method of the structure of the concrete joint surface which concerns on Claim 2 of this invention is a method of constructing the structure of the concrete joint surface of Claim 1 mentioned above, Comprising: The cutting blade for drilling | piercing at the front-end | tip And drilling the existing concrete surface with a drill having a frustoconical cutting blade on the outer periphery, thereby simultaneously forming a hole for embedding anchor bars and an inverted conical recess.

  A method for evaluating the shear strength of a concrete joint surface structure according to claim 3 of the present invention is a method for evaluating the shear strength of a concrete joint surface structure according to claim 1 described above. The first step to determine the shear strength according to the embedding length of the anchor bars in the new concrete, assuming that the surface structure is shear fractured at the assumed fracture surface assumed on the new concrete side, and the structure of the joint surface is The second step is to obtain the shear strength when assuming bearing failure by the least square method based on the force balance formula at the joint surface, and the shear strength obtained by the first step and the second step. It is characterized in that the smaller one of them is obtained.

A method for evaluating the shear strength of the structure of the concrete joint surface according to claim 4 of the present invention is a method for evaluating the shear strength of the structure of the concrete joint surface according to claim 1 described above. The shear strength is obtained from a relational expression.
Qu / Qst = β1 · [β2 + β3 · Q + β4 · Q ² ]
However, Q = γ1 + γ2 · σB ′ + γ3 · d0 ′ + γ4 · dp ′ + γ5 · α
σB ': Compressive strength ratio between existing concrete and new concrete
d0 ': Ratio of the diameter of the bottom surface of the recess to the diameter of the anchor bar
dp ′: ratio of the depth of the recess to the diameter of the anchor bar
α: Tapered angle of the recess
β1 to β4: Coefficients determined based on the force balance formula on the joint surface
γ1 to γ5: Coefficients determined based on the balance equation of force on the joint surface
Qst: Shear strength neglecting the effect of recesses
Qu: Shear strength

  A concrete joint surface design method according to claim 5 of the present invention is a method for designing a concrete joint surface structure according to claim 1 described above, wherein the shear structure of the joint surface is sheared. The proof strength is obtained by the method according to claim 3 or 4, and the embedding length of the anchor bars in the newly installed concrete is designed based on the obtained shear strength.

According to a sixth aspect of the present invention, there is provided a method for designing the structure of a concrete connection surface according to the first aspect of the present invention. It is characterized by designing the length and diameter of the anchor bars embedded in, the size of the recesses, and the strength of the new concrete.
hst ′ = δ1 · [δ2 + δ3 · σB ′ + δ4 · d0 ′ + δ5 · dp ′ + δ6 · α]
However, hst ': Ratio of anchor bar embedding length and diameter in new concrete
σB ': Compressive strength ratio between existing concrete and new concrete
d0 ': Ratio of the diameter of the bottom surface of the recess to the diameter of the anchor bar
dp ′: ratio of the depth of the recess to the diameter of the anchor bar
α: Tapered angle of the recess
δ1 to δ6: Coefficients determined based on the balance equation of force on the connecting surface

  According to the structure of the concrete connection surface according to the present invention, it is a structure of the connection surface between the existing concrete and the new concrete to be transferred to this, the inverted conical recess provided on the surface of the existing concrete, It is composed of anchor bars with one end embedded in the existing concrete and the other end embedded in the new concrete through this recess, so that the new concrete can be placed in the recess reliably and the shearing force of the joint surface is efficient. Can be transmitted, and high shear rigidity can be secured.

  Moreover, according to the construction method of the structure of the concrete joint surface according to the present invention, by drilling the existing concrete surface with a drill having a cutting blade for drilling at the tip and a frustoconical cutting blade on the outer periphery, Since the hole for embedding the anchor muscle and the inverted conical recess are formed at the same time, there is an effect that the drilling operation can be easily performed with a small number of steps.

  Further, according to the method for evaluating the shear strength of the structure of the concrete joint surface according to the present invention, the shear strength in the case where it is assumed that the structure of the joint surface is subjected to shear failure at the assumed fracture surface assumed on the side of the newly installed concrete, The first step, which is determined according to the embedding length of the anchor bar, and the shear strength when assuming that the structure of the joint surface is fractured by bearing are calculated by the least square method based on the force balance equation at the joint surface. And determining the shear strength of the smaller one of the shear strengths determined by the first step and the second step, so that the shear strength of the structure of the joint surface can be evaluated. There is an effect.

Further, according to the method for evaluating the shear strength of the structure of another concrete connection surface according to the present invention, the shear strength is obtained by the following relational expression.
Qu / Qst = β1 · [β2 + β3 · Q + β4 · Q ² ]
However, Q = γ1 + γ2 · σB ′ + γ3 · d0 ′ + γ4 · dp ′ + γ5 · α
σB ': Compressive strength ratio between existing concrete and new concrete
d0 ': Ratio of the diameter of the bottom surface of the recess to the diameter of the anchor bar
dp ′: ratio of the depth of the recess to the diameter of the anchor bar
α: Tapered angle of the recess
β1 to β4: Coefficients determined based on the force balance formula on the joint surface
γ1 to γ5: Coefficients determined based on the balance equation of force on the joint surface
Qst: Shear strength neglecting the effect of recesses
Qu: Shear strength By using this relational expression, there is an effect that the shear strength of the structure of the joining surface can be obtained easily and quickly.

  Further, according to the method for designing the structure of the concrete joint surface according to the present invention, the shear strength of the structure of the joint surface is obtained by the method according to claim 3 or 4, and the new concrete is based on the obtained shear strength. Since the length of the anchor muscle to be embedded is designed, there is an effect that the length of the anchor muscle having the structure of the connecting surface can be designed.

In addition, according to the design method for the structure of another concrete connection surface according to the present invention, the length and diameter of anchor bars embedded in the new concrete, the size of the recess, and the strength of the new concrete are designed by the following relational expressions. .
hst ′ = δ1 · [δ2 + δ3 · σB ′ + δ4 · d0 ′ + δ5 · dp ′ + δ6 · α]
However, hst ': Ratio of anchor bar embedding length and diameter in new concrete
σB ': Compressive strength ratio between existing concrete and new concrete
d0 ': Ratio of the diameter of the bottom surface of the recess to the diameter of the anchor bar
dp ′: ratio of the depth of the recess to the diameter of the anchor bar
α: Tapered angle of the recess
δ1 to δ6: Coefficient determined based on the balance formula of force on the joining surface By using this relational expression, there is an effect that the structural specifications of the joining surface can be designed easily and quickly. It is also possible to compare and examine a plurality of design proposals by substituting various values into this relational expression. For this reason, the optimization design of the structural specifications of the joining surface can be easily performed.

FIG. 1 is a side sectional view showing an embodiment of a concrete joint surface structure according to the present invention. FIG. 2 is a plan sectional view showing an example of the structure of the concrete connection surface according to the present invention. FIG. 3 is a diagram illustrating a state of the acting force on the joining surface. FIG. 4 is a diagram showing an embodiment of a construction method for a concrete joint surface structure according to the present invention. FIG. 5 is a diagram showing the reaction force and dimensions on the joining surface. FIG. 6 is a diagram showing a supporting stress acting region in the recess (shear cotter). FIG. 7 is a relationship diagram (case 1) between the shear strength and the embedding length of the anchor bars. FIG. 8 is a relationship diagram (case 2) between the shear strength and the embedding length of the anchor bars. FIG. 9 is a relationship diagram (case 3) between the shear strength and the embedding length of the anchor bars. FIG. 10 is a relationship diagram (case 4) between the shear strength and the embedding length of the anchor bars. FIG. 11 is a diagram in which the accuracy of the evaluation formulas for the anchor muscle embedding length and shear strength is verified. FIG. 12 is a cross-sectional view illustrating the structure of a conventional concrete joining surface. FIG. 13 is a cross-sectional view illustrating the structure of a conventional concrete joining surface. FIG. 14 is a cross-sectional view illustrating the structure of a conventional concrete joining surface.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a concrete joint surface structure, a construction method, a shear strength evaluation method, and a design method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

[Concrete joint surface structure]
First, an embodiment of the structure of a concrete connecting surface according to the present invention will be described with reference to FIGS.

  As shown in FIGS. 1 and 2, a concrete joint surface structure 100 according to the present invention is a structure of a joint surface between an existing concrete 10 and a new concrete 12 to be handed over to the existing concrete 10. After the inverted cone-shaped concave portion 14 provided on the surface 10a (hereinafter sometimes referred to as a joint surface), the lower end 16a is embedded in the existing concrete 10 and the upper end 16b is embedded in the new concrete 12 via the concave portion 14. It consists of construction anchor bars 16.

  The concave portion 14 has a bottom surface 14a and a tapered surface 14b, and anchor muscles 16 are embedded in holes drilled in the bottom surface 14a. The taper angle α of the tapered surface 14b can be an inclination angle of about 30 to 60 °. Thus, by forming the concave portion 14 serving as a shear key in the shape of an inverted cone, it becomes easy to fill the material of the newly-installed concrete, which can be placed later, and the placement can be performed reliably. Transmission can be performed efficiently.

  A fixing hardware such as a nut 18 can be mounted on the upper end 16 b side of the anchor bar 16. The mounting position of the fixing hardware is set to a position higher than the joining surface 10a (new concrete 12 side). By doing so, as shown in FIG. 3, the vertical component Pv of the supporting pressure P due to the shearing force acting on the joining surface 10 a is easily borne on the anchor muscle 16.

  In this joining surface structure 100, since shear slip hardly occurs due to the recess 14 and the anchor reinforcement 16, the shear stiffness (initial stiffness) in the joining surface 10a is almost equal to the shear stiffness of the base material (concrete). The same level.

  As described above, according to the concrete joining surface structure 100 of the present invention, the new concrete can be reliably placed in the recess 14, and the shearing force of the joining surface 10a can be efficiently transmitted, resulting in high shear. Rigidity can be ensured.

  It should be noted that the shear strength at the joint surface 10a depends on the control area and depth of the cone-shaped sheer key formed by the newly-installed concrete 12 entering the concave portion 14, the pull-out strength of the anchor bars 16, etc. It is possible to evaluate by the method.

[Construction method]
Next, an embodiment of a method for constructing a concrete joint surface according to the present invention will be described with reference to FIG.

  As shown in FIGS. 4 (a) and 4 (b), the method for constructing a concrete joint surface of the present invention has a cutting blade 20a for drilling at the tip and a truncated cone-shaped cutting blade 20b at the outer periphery. The existing concrete surface 10 a is drilled with a drill 20. Thereby, as shown in FIG.4 (c), the hole 22 for embedding an anchor reinforcement and the recessed part 14 of an inverted cone shape are formed simultaneously in the existing concrete 10. As shown in FIG. The existing concrete surface 10a (joint surface) need not be subjected to surface treatment such as roughening.

  Subsequently, an anchor bar is inserted and disposed in the hole 22, and an adhesive is filled in the gap between the anchor bar and the existing concrete 10. A fixing metal such as a nut is attached to the upper end side of the anchor bar. Finally, the new concrete 12 is placed on the existing concrete surface 10a. With the above construction procedure, a joint surface structure 100 as shown in FIG. 1 is obtained.

  For this reason, according to the construction method of the present invention, the inverted cone-shaped recess 14 can be formed using the drill 20 having the truncated cone-shaped cutting blade 20b, so that the recess 14 is formed alone. No process occurs. Therefore, drilling can be easily performed with a small number of processes.

  Instead of simultaneously drilling the recess 14 and the hole 22 as described above, the hole 22 may be drilled in advance, and the recess 14 may be drilled separately after the drilling of the hole 22 is completed. .

  In the embodiment of the concrete joint surface structure and construction method described above, the case where the joint surface 10a is a horizontal plane has been described. However, in addition to the horizontal plane, if it is a boundary surface between the existing concrete 10 and the new concrete 12 It may be a vertical surface or a surface inclined with respect to the horizontal.

[Shearing strength evaluation method]
Next, an embodiment of the method for evaluating the shear strength of the structure of the concrete joint surface according to the present invention will be described.

The method for evaluating the shear strength of the concrete joint surface structure of the present invention comprises a first step and a second step.
In the first step, the shear strength Qu (qu1 described later) when assuming that the structure of the joint surface is shear fractured at the assumed fracture surface assumed on the new concrete side is set to the embedding length hst of the anchor bar in the new concrete. It is what you ask for.

  In the second step, the shear strength Qu (described later, qu2) is calculated by the least square method based on the force balance equation on the connecting surface when it is assumed that the structure of the connecting surface is subjected to bearing failure.

  Then, the smaller one of the shear strengths qu1 and qu2 determined in the first step and the second step is determined. Thereby, the shear strength of the structure of this joint surface can be evaluated.

Hereinafter, the procedure of this shear strength evaluation method will be described more specifically with reference to FIG. 5 and FIG.
FIG. 5 is a diagram showing the reaction force and dimensions on the joining surface, and FIG. 6 is a diagram showing the supporting stress acting region in the recess (shear cotter).

About the symbol showing the dimension etc. in FIG. 5, the following is shown, respectively.
d0: Diameter of the bottom surface of the concave portion dp: Depth of the concave portion de: Rb action position (horizontal distance from the anchor muscle center)

hst: Anchor projection length (embedding length of anchor bars in new concrete)
dst: Diameter of anchor muscle Qu: Shear transmission force (Min (qu1, qu2))
qu1: Shear strength when fractured at the assumed fracture plane qu2: Strength when fractured under pressure Min (d0 / 2, hst / 2): Ra action position (horizontal distance from anchor muscle center)
e: Qu action position (vertical distance from the assumed fracture surface)

In this example, the following assumptions are made in this shear strength evaluation.
That is, the friction is considered only on the tapered surface, and the proof strength qu1 due to the destruction of the newly installed concrete is assumed to increase the proof strength of the assumed fracture surface. The proof strength qu2 due to the bearing pressure or the like is obtained by the least square method based on the formula of force balance. As for the rigidity, it is assumed that high rigidity can be ensured in the case of high proof stress.

(Balance of vertical force)
5 and FIG. 6, the balance formula of the force in the vertical direction is expressed by the following formula (1).
−T + Ra + Rb · cos α−Sb · sin α = 0 (1)
Here, T: Support pressure acting on the bottom surface of the recess
Ra: Reaction force at the bottom of the recess
Rb: Bearing pressure reaction force of tapered surface
Sb: Friction force of tapered surface
α: Taper angle

(Moment balance)
The moment balance equation is as shown in the following equation (2).
−qs · (e + dp) + Ra · Min (d0 / 2, hst / 2)
+ Rb · {de · cos α− (e + dp / 2) · sin α}
−Sb · {de · sin α + (e + dp / 2) · cos α} = 0 (2)
Here, qs is a shearing force.
Min is an operator that takes the smaller of the arguments. For example, Min (x, y) takes the smaller value of either x or y.

(Relationship between each constitutive equation and strength)
From the above formulas (1) and (2), the following formulas (3) to (5) are obtained.
T = Ra + Rb · cos α−Sb · sin α ≦ Ast · σy
^{≡ (π · dst 2/4} ) · σy ··· (3)

qs = {Min (d0 / 2, _hst / 2) / (e + dp)} · Ra
+ [{De · cos α− (e + dp / 2) · sin α} / (e + dp)] · Rb
− [{De · sin α + (e + dp / 2) · cos α} / (e + dp)] · Sb
≦ 0.5Ast · √ (σB · Ec)
^{≡0.5 (π · dst 2/4} ) · √ (σB · Ec) ··· (4)
Here, the right side 0.5Ast · √ (σB · Ec) of the inequality sign in the above equation (4) is the shear strength (Qst described later) ignoring the influence of the recess.

Sb ≦ μ · Rb + S0, Rb ≦ αp · σB · S (5)
Where μ: coefficient of friction (= 0.4)
αp: bearing pressure strength coefficient (= 2.0)
S: Effective area for bearing the concave portion (shear cotter)
S0: Adhesive force
Ast: Cross section of anchor muscle
σy: Anchor muscle tensile yield strength
σB: Compressive strength of existing concrete
Ec: elastic modulus of existing concrete S = (π / 4) · dp · (d0 + dp · tan α) / cos α,
de = (8 / 3π) · (d0 / 2 + dp · tan α)

(Shear transmission strength evaluation formula)
The equation for evaluating the shear transmission resistance Qu is as the following equation (6).
Qu = Min (qu1, qu2) (6)
Here, qu1 is calculated according to the value of the anchor muscle embedding length hst.
(I) When hst ≦ dp qu1 = Ac · τc

(Ii) dp <For hst ≦ dp + 4 · dp qu1 = Ac · τc + {0.5 (π · dst 2/4) · √ (σB · Ec)}
・ {(Hst-dp) / (4 · dst)}

(Iii) When hst> dp + 4 · dp qu1 = Ac · τc + 0.5 Ast · √ (σB · Ec)
However, Ac = (π / 4) · (d0 + 2 · dp · tan α) ²
Ac: Cross-sectional area at the assumed fracture surface
τc: Shear strength of new concrete

  Further, qu2 = qs + Rb · sin α + Sb · cos α

(Shearing strength evaluation method by bearing pressure etc.)
Next, the reaction force vector R is obtained by the least square method so that each element of the objective function G represented by the following equation (7) is 0 or less from the conditions of the above equations (3) to (5).
G (R) = B · R−f (7)
here,
B = (B1 B2 B3)
R = (Ra Rb Sb) ^T
f = (Ast · σy 0.5 As · √ (σB · Ec) S 0 αp · σB · S) ^T

The matrix elements B1, B2, and B3 are as follows.
B1 = (1 qs1 0 0) ^T
B2 = (cosα qs2 −μ 1) ^T
B3 = (− sin α qs3 0 0) ^T
However,
qs1 = Min (d0 / 2, h _st / 2) / (e + dp)
qs2 = {de · cos α− (e + dp / 2) · sin α} / (e + dp)
qs3 = − [{de · sin α + (e + dp / 2) · cos α} / (e + dp)]

From the above equation (7), an optimal vector Ropt that minimizes the sum of squared residuals Δ shown in the following equation (8) is obtained, and a solution satisfying each condition is defined as a final solution Rans.
Δ = G (R) ^T • G (R) = [B • R−f] ^T • [B • R−f] (8)
∴ Ropt = [B ^T B] ⁻¹ B ^T · f (9)
Based on the final solution Rans obtained by the above equation (9), T and qs can be obtained from the equations (3) and (4). Thereby, the shear strengths qu1, qu2, and Qu can be calculated according to the embedding length hst of the anchor muscle and the taper angle α.

FIG. 7 to FIG. 10 illustrate relationship diagrams between the shear strength obtained by the above calculation and the anchor muscle embedding length. All of these figures were calculated with e = 10 mm, d0 = 100 mm, dp = 10 mm, dst = φ19 mm, σy = 235 N / mm ² , and the compressive strength ratio between the existing concrete and the new concrete is shown in each figure. It has changed with. In each figure, α is 30 °, 45 °, and 60 °, and a plot with a solid line indicates qu1 and a plot with a broken line indicates qu2. Qu takes the smaller value of either qu1 or qu2. In addition, 0.5 As · √min (σB · Ec) is indicated by a broken line as a shear strength neglecting the influence of the recess.

Here, Case 1 in FIG. 7 is a case where the existing concrete compressive strength is 13.5 N / mm ² and the newly installed concrete compressive strength is 24 N / mm ² .
Case 2 in FIG. 8 is a case where the existing concrete compressive strength is 13.5 N / mm ² and the new concrete compressive strength is 30 N / mm ² .
Case 3 in FIG. 9 is a case where the existing concrete compressive strength is 13.5 N / mm ² and the newly installed concrete compressive strength is 36 N / mm ² .
Case 4 in FIG. 10 is a case where the existing concrete compressive strength is 30 N / mm ² and the new concrete compressive strength is 30 N / mm ² .

Further, the shear strength of the concrete joint surface structure 100 of the present invention can be obtained by the following relational expression (10) in addition to the above embodiment. If the dimensions of the recesses, the diameter of the anchor bars, the strength of the concrete, etc. are input into this relational expression (10), the shear strength Qu of the structure 100 of the concrete joint surface can be obtained simply and quickly.
Qu / Qst = β1 · [β2 + β3 · Q + β4 · Q ² ] (10)
However, Q = γ1 + γ2 · σB ′ + γ3 · d0 ′ + γ4 · dp ′ + γ5 · α
σB ': Compressive strength ratio between existing concrete and new concrete
d0 ': Ratio of the diameter of the bottom surface of the recess to the diameter of the anchor bar
dp ′: ratio of the depth of the recess to the diameter of the anchor bar
α: Tapered angle of the recess
β1 to β4: Coefficients determined based on the force balance formula on the joint surface
γ1 to γ5: Coefficients determined based on the balance equation of force on the joint surface
Qst: Shear strength neglecting the effect of recesses
Qu: Shear strength

Here, σB ′ = σB0 / σB1
(However, σB0: Existing concrete strength, σB1: New concrete strength)
d0 '= d0 / dst
dp ′ = dp / dst
The value of Qst, Qst = 0.5 (π · dst 2/4) · √ ( may be used .sigma.B · Ec.

When the calculation is performed under the conditions of σy = 295 N / mm ² and e = 10 mm, the coefficients β1 to β4 and γ1 to γ5 are β1 = 0.9, β2 = 1.74, β3 = −1.54, Values of β4 = 0.89, γ1 = 1.33, γ2 = −0.31, γ3 = 0.08, γ4 = 0.60, and γ5 = −0.009 can be used.

  In this case, in order to increase the shear strength, (1) σB1 is increased, (2) dp is increased, (3) d0 is increased, and (4) α is decreased in this order. It is effective.

The above relational expression (10) is obtained as an approximate expression of the plot shown in FIG. 11 (dashed line expression Y = 0.9 · X in the figure) (correlation coefficient R ² = 0.892). ). Each plot is obtained under the following conditions based on the calculation process of the above equations (1) to (9). Therefore, for β1 to β4 and γ1 to γ5, in addition to the above numerical values, the coefficient values can be used when different approximate expressions are obtained depending on the calculation conditions.

(Plot calculation conditions)
σB0: 13.5, 18, 21 N / mm ²
σB1: 24, 30, 36 N / mm ²
d0: φ75, φ100, φ125 mm
dp: 5, 10, 20 mm
dst: φ19, φ22mm
α: 75, 45, 30 °

[Design method]
Next, an embodiment of a method for designing a structure of a concrete joint surface according to the present invention will be described.

  The concrete joint surface design method of the present invention determines the shear strength of the joint surface structure by the above-mentioned shear strength evaluation method, and embeds the anchor bars in the new concrete based on the obtained shear strength. Is to design.

  This design method can also be realized as a design apparatus using a computer. That is, this design apparatus is constituted by shear strength evaluation means and design means. Each of these means performs arithmetic processing using a computer. The shear strength evaluation means performs a process for obtaining the shear strength of the joint surface structure by the above-described shear strength evaluation method. The design means performs a process of designing the embedding length of the anchor bars in the newly installed concrete based on the shear strength obtained by the shear strength evaluation means.

  According to this design device, the structural dimensions of the joint surface (dimension dimensions, anchor bar diameter, etc.) are input, and other structural specifications such as the length of the anchor bar embedded in the new concrete are obtained. Can do.

  For example, the shear strength evaluation means creates a relation diagram as shown in FIG. 7, and the design means reads the minimum anchor muscle embedding length hst exceeding 0.5 As · √min (σB · Ec) from this figure. May be. In FIG. 7, it can be seen that when α = 30 °, the design should be about hst = 45 mm or more.

In addition, according to the design method for the structure 100 of the concrete joint surface of the present invention, the embedding length and diameter of the anchor bars in the new concrete, the concave portion, according to the following relational expression (11), in addition to the above embodiment. The dimensions of new concrete can be designed.
hst ′ = δ1 · [δ2 + δ3 · σB ′ + δ4 · d0 ′ + δ5 · dp ′ + δ6 · α]
(11)
However, hst ': Ratio of anchor bar embedding length and diameter in new concrete
σB ': Compressive strength ratio between existing concrete and new concrete
d0 ': Ratio of the diameter of the bottom surface of the recess to the diameter of the anchor bar
dp ′: ratio of the depth of the recess to the diameter of the anchor bar
α: Tapered angle of the recess
δ1 to δ6: Coefficients determined based on the balance equation of force on the connecting surface

Where hst ′ = hst / dst
σB ′ = σB0 / σB1
(However, σB0: Existing concrete strength, σB1: New concrete strength)
d0 '= d0 / dst
dp ′ = dp / dst

When the calculation is performed under the conditions of σy = 295 N / mm ² and e = 10 mm, the coefficients δ1 to δ6 are δ1 = 1.1, δ2 = 1.42, δ3 = 2.77, δ4 = −0. .24, δ5 = 0.46, and δ6 = 0.09 can be used.

  In this case, in order to shorten the embedding length of the anchor muscle, (1) σB1 is increased, (2) dp is decreased, (3) d0 is increased, and (4) α is decreased. Are effective in this order.

The above relational expression (11) is obtained as an approximate expression of the plot shown in FIG. 11 (solid line expression Y = 1.1 · X in the figure) (correlation coefficient R ² = 0.936). ). Each plot is obtained under the above-mentioned conditions based on the calculation processes of the above formulas (1) to (9). From this, for δ1 to δ6, in addition to the above numerical values, the coefficient values can be used when different approximate expressions are obtained depending on the calculation conditions.

  By using the above relational expression (11), the structural specifications of the joining surface can be designed easily and quickly. It is also possible to compare and examine a plurality of design proposals by substituting various values into this relational expression. For this reason, the optimization design of the structural specifications of the joining surface can be easily performed.

  As explained above, according to the structure of the concrete connection surface according to the present invention, it is the structure of the connection surface between the existing concrete and the new concrete to be connected to the concrete, and the reverse surface provided on the surface of the existing concrete. Consisting of a conical recess and anchor bars with one end embedded in the existing concrete and the other end embedded in the new concrete through the recess. Surface shear force can be transmitted efficiently, and high shear rigidity can be ensured.

  Moreover, according to the construction method of the structure of the concrete joint surface according to the present invention, by drilling the existing concrete surface with a drill having a cutting blade for drilling at the tip and a frustoconical cutting blade on the outer periphery, Since the hole for embedding the anchor muscle and the concave portion having the inverted conical shape are formed at the same time, the drilling operation can be easily performed with fewer steps.

  Further, according to the method for evaluating the shear strength of the structure of the concrete joint surface according to the present invention, the shear strength in the case where it is assumed that the structure of the joint surface is subjected to shear failure at the assumed fracture surface assumed on the side of the newly installed concrete, The first step, which is determined according to the embedding length of the anchor bar, and the shear strength when assuming that the structure of the joint surface is fractured by bearing are calculated by the least square method based on the force balance equation at the joint surface. And determining the shear strength of the smaller one of the shear strengths determined by the first step and the second step, so that the shear strength of the structure of the joint surface can be evaluated. .

Further, according to the method for evaluating the shear strength of the structure of another concrete connection surface according to the present invention, the shear strength is obtained by the following relational expression.
Qu / Qst = β1 · [β2 + β3 · Q + β4 · Q ² ]
However, Q = γ1 + γ2 · σB ′ + γ3 · d0 ′ + γ4 · dp ′ + γ5 · α
σB ': Compressive strength ratio between existing concrete and new concrete
d0 ': Ratio of the diameter of the bottom surface of the recess to the diameter of the anchor bar
dp ′: ratio of the depth of the recess to the diameter of the anchor bar
α: Tapered angle of the recess
β1 to β4: Coefficients determined based on the force balance formula on the joint surface
γ1 to γ5: Coefficients determined based on the balance equation of force on the joint surface
Qst: Shear strength neglecting the effect of recesses
Qu: Shear strength By utilizing this relational expression, the shear strength of the structure of the joining surface can be obtained simply and quickly.

  Further, according to the method for designing the structure of the concrete joint surface according to the present invention, the shear strength of the structure of the joint surface is obtained by the method according to claim 3 or 4, and the new concrete is based on the obtained shear strength. Since the embedding length of the anchor muscle is designed, the length of the anchor muscle of the joint surface structure can be designed.

In addition, according to the design method for the structure of another concrete connection surface according to the present invention, the length and diameter of anchor bars embedded in the new concrete, the size of the recess, and the strength of the new concrete are designed by the following relational expressions. .
hst ′ = δ1 · [δ2 + δ3 · σB ′ + δ4 · d0 ′ + δ5 · dp ′ + δ6 · α]
However, hst ': Ratio of anchor bar embedding length and diameter in new concrete
σB ': Compressive strength ratio between existing concrete and new concrete
d0 ': Ratio of the diameter of the bottom surface of the recess to the diameter of the anchor bar
dp ′: ratio of the depth of the recess to the diameter of the anchor bar
α: Tapered angle of the recess
δ1 to δ6: Coefficients determined on the basis of the force balance formula on the joining surface By using this relational expression, the structural specifications of the joining surface can be designed easily and quickly. It is also possible to compare and examine a plurality of design proposals by substituting various values into this relational expression. For this reason, the optimization design of the structural specifications of the joining surface can be easily performed.

  As described above, the structure of the concrete connection surface according to the present invention, the construction method, the shear strength evaluation method and the design method of this structure ensure the integrity of the existing concrete and the newly-placed new concrete in seismic retrofitting work, etc. In particular, it is suitable for ensuring high shear rigidity.

DESCRIPTION OF SYMBOLS 10 Existing concrete 12 New concrete 14 Recessed part 14a Bottom surface 14b Tapered surface 16 Anchor reinforcement 16a Lower end (one end)
16b Upper end (other end)
18 Nut 20 Drill 20a Cutting blade for drilling 20b Frustum-shaped cutting blade 22 Hole α Taper angle 10a Joint surface (existing concrete surface)
100 Structure of concrete connection surface

Claims (6)

  It is a structure of the joint surface between the existing concrete and the new concrete to be jointed to it, and a reverse cone-shaped recess provided on the surface of the existing concrete, and one end is embedded in the existing concrete through this recess, and the other end The structure of the jointing surface of the concrete, characterized by comprising anchor bars embedded in the newly installed concrete. A method for constructing the structure of the concrete connection surface according to claim 1,
By drilling the existing concrete surface with a drill that has a cutting blade for drilling at the tip and a frustoconical cutting blade on the outer periphery, a hole for embedding anchor bars and an inverted conical recess are simultaneously formed The construction method of the structure of the concrete joint surface characterized by this. A method for evaluating the shear strength of the structure of the concrete joint surface according to claim 1,
A first step of determining the shear strength when assuming that the structure of the joint surface is shear fractured at the assumed fracture surface assumed on the new concrete side according to the embedding length of the anchor bar in the new concrete;
A second step of determining the shear strength when assuming that the structure of the joining surface is subjected to bearing failure by the least square method based on a force balance equation on the joining surface;
A method for evaluating the shear strength of a structure of a concrete joint surface, wherein the smaller one of the shear strengths obtained in the first step and the second step is obtained. A method for evaluating the shear strength of the structure of the concrete joint surface according to claim 1, wherein the shear strength is obtained by the following relational expression.
Qu / Qst = β1 · [β2 + β3 · Q + β4 · Q ² ]
However, Q = γ1 + γ2 · σB ′ + γ3 · d0 ′ + γ4 · dp ′ + γ5 · α
σB ': Compressive strength ratio between existing concrete and new concrete
d0 ': Ratio of the diameter of the bottom surface of the recess to the diameter of the anchor bar
dp ′: ratio of the depth of the recess to the diameter of the anchor bar
α: Tapered angle of the recess
β1 to β4: Coefficients determined based on the force balance formula on the joint surface
γ1 to γ5: Coefficients determined based on the balance equation of force on the joint surface
Qst: Shear strength neglecting the effect of recesses
Qu: Shear strength A method for designing the structure of a concrete connecting surface according to claim 1,
A concrete jointing characterized in that the shear strength of the structure of the joint surface is determined by the method according to claim 3 or 4, and the embedding length of the anchor bar in the newly installed concrete is designed based on the determined shear strength. How to design the surface structure. A method for designing the structure of a concrete connecting surface according to claim 1,
A method for designing the structure of a concrete connection surface, characterized in that the length and diameter of anchor bars embedded in the new concrete, the dimensions of the recesses, and the strength of the new concrete are designed by the following relational expression.
hst ′ = δ1 · [δ2 + δ3 · σB ′ + δ4 · d0 ′ + δ5 · dp ′ + δ6 · α]
However, hst ': Ratio of anchor bar embedding length and diameter in new concrete
σB ': Compressive strength ratio between existing concrete and new concrete
d0 ': Ratio of the diameter of the bottom surface of the recess to the diameter of the anchor bar
dp ′: ratio of the depth of the recess to the diameter of the anchor bar
α: Tapered angle of the recess
δ1 to δ6: Coefficients determined based on the balance equation of force on the connecting surface

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