Wing wall extension reinforcing structure and wing wall extension reinforcing method

Abstract

To provide a wing wall extension reinforcing construction method and a wing wall extension reinforcing structure used therefor, capable of exhibiting the same effect as satisfying an RC holding yield strength standard on a lateral reinforcing bar ratio of a column-beam joining part by installation of a wing wall.SOLUTION: When a horizontal load is applied to the rigid-frame structure in which the four wing walls 5 are installed so as to surround the 3a of the cross-shaped joint, the wing walls 5 receive a tensile force Tg and a compressive force Cg from the beams 2, and the lateral reinforcing bar ratio of the 3a of the cross-shaped joint, which receives a shearing force Vc ' from the column 1, is multiplied by the current k2, a force Δ T borne by the wing walls 5 is set to (1-1 / k2) times or more the tensile force Tg.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to the seismic reinforcement design of reinforced concrete buildings (hereinafter referred to as RC buildings), and in particular to a sleeve wall addition reinforcement method that can achieve the same effect as satisfying the RC bearing capacity standards regarding the lateral reinforcement ratio of column-beam joints by installing a sleeve wall inside a frame (hereinafter referred to as RC frame) consisting of a pair of columns and a pair of beams, and to a sleeve wall addition reinforcement structure used therein. [Background technology]

[0002] Since the new earthquake resistance standards were established in 1981, the design of column-beam joints in reinforced concrete buildings has been carried out in accordance with the "Reinforced Concrete Structural Calculation Standards and Commentary" (hereinafter referred to as the "RC Standards") published by the Architectural Institute of Japan. However, the "Reinforced Concrete Structural Horizontal Strength Calculation Standards and Commentary 2021" (hereinafter referred to as the "RC Strength Standards") published by the Architectural Institute of Japan in 2021 has strengthened the design standards for column-beam joints (for example, the requirement for the transverse reinforcement ratio in column-beam joints has been changed from 0.2% or more to 1.5 times 0.3% or more) in a way that reflects previous damage conditions and research results for column-beam joints during earthquakes. According to this "RC Strength Standard," even existing buildings designed after 1981 may have column-beam joints that are at risk of damage during an earthquake. If column-beam joints, which constantly support the building's load like columns, are severely damaged during an earthquake, there is a risk that the building will collapse or tip over due to aftershocks that occur following the main earthquake. In the future, in parallel with the earthquake resistance of buildings designed in accordance with the old earthquake resistance standards, the reinforcement of column-beam joints will also become an issue for existing buildings designed after 1981. Therefore, in recent years, there has been a demand for earthquake-resistant reinforcement structures and earthquake-resistant reinforcement construction methods that can be applied to these buildings.

[0003] As an example of a technology for increasing the earthquake resistance of a building by adding sleeve walls, Patent Document 1 discloses an invention entitled "Column structure and column reinforcement method" that relates to a method for reinforcing columns with sleeve walls and the column structure. The invention disclosed in Patent Document 1, which relates to a method for reinforcing columns, is characterized by the following steps: protruding anchor bars from the side of an existing column, arranging spiral anti-splitting bars in these anchor bars, a precast sleeve wall with a joint groove on the joint surface with the column, abutting the side of the column so that the anchor bars and anti-splitting bars are housed inside the joint groove, inserting the front half of the stirrup bars exposed inside the joint groove into the anchor bars, and then injecting mortar into the joint groove from the top of the sleeve wall. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3444785 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while the invention disclosed in Patent Document 1 has the advantage that by using precast sleeve walls, no curing period is required for the sleeve walls and they can be added in a short period of time, there is a possibility that the sleeve walls will not meet the performance requirements for column-beam joints in the ``RC Strength Standards'', and the building including the column-beam joints will not exhibit sufficient earthquake resistance, and because the sleeve walls are not appropriately designed to improve the earthquake resistance performance of the column-beam joints, they will be over-specified and the costs for earthquake-resistant construction of the building may increase.

[0006] The present invention has been made in response to such conventional circumstances, and aims to provide a sleeve wall addition reinforcement method and a sleeve wall addition reinforcement structure used therein that can achieve the same effect as satisfying the RC strength standards regarding the lateral reinforcement ratio of column-beam joints by installing sleeve walls. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the first invention is a sleeve wall addition reinforcement structure in which a sleeve wall is added for the purpose of reducing the shear force generated at the column-beam joint formed by the beam and column in an RC building, characterized in that, when the tensile force T and compressive force C that the column-beam joint receives from the beam or column are respectively taken as ΔT and ΔC, and the forces that flow to the sleeve wall through the joint surface between the sleeve wall and the beam or column and are borne by the sleeve wall (hereinafter referred to as "forces borne by the sleeve wall"), the sleeve wall is installed so that at least one of ΔT / T or ΔC / C is 1 / 3 or more.

[0008] The second invention is characterized in that in the first invention, the joint between the beam or column and the sleeve wall is joined using a post-installed anchor.

[0009] The third invention is the first or second invention, wherein the sleeve wall has a resistance of 1.5N / mm 2 The present invention is characterized in that the reinforced concrete is formed using non-shrinkage mortar or non-shrinkage concrete having the above adhesive strength.

[0010] The fourth invention is a sleeve wall addition reinforcement method for reducing the shear force generated at the beam-column joint formed by the beam and column in a reinforced concrete building. When the tensile force T and compressive force C that the beam-column joint receives from the beam or column are respectively ΔT and ΔC, the forces that flow to the sleeve wall through the joint surface between the sleeve wall and the beam or column and are borne by the sleeve wall, the sleeve wall is installed so that at least one of ΔT / T or ΔC / C is 1 / 3. [Effects of the Invention]

[0011] According to the first invention, even if the design standards for the lateral reinforcement ratio of column-beam joints are increased to 1.5 times the current standards, it is possible to obtain the same or greater effect as that of the new design standards.

[0012] According to the second invention, the joining force of the sleeve wall to the beam or column is determined by the cross-sectional area and yield stress of the post-installed anchor, so that the force to be borne by the sleeve wall out of the tensile and compressive forces that the column-beam joint receives from the beam or column can be easily set.

[0013] In the third invention, the adhesive strength at the interface between the beam / column and the sleeve wall is strong, so they are nearly formed simultaneously, mitigating the approximately 20% reduction in shear strength required with conventional sleeve wall reinforcement. Furthermore, because the sleeve wall is formed from non-shrink mortar or non-shrink concrete, unlike sleeve walls formed from ready-mixed concrete, the two steps of pouring ready-mixed concrete and filling with non-shrink mortar are not required during sleeve wall construction. This shortens construction time and reduces manufacturing costs, so according to the third invention, sleeve walls can be installed efficiently, inexpensively, and in a short period of time, while mitigating the reduction in shear strength.

[0014] The fourth invention is a method invention, whereas the first invention is a product invention, and therefore has the same effect as the first invention. [Brief explanation of the drawings]

[0015] [Figure 1] (a) is a front view showing the rigid frame structure of a reinforced concrete building, and (b) is a diagram showing the state in which a sleeve wall has been constructed inside the reinforced concrete frame in (a). [Figure 2] (a) and (b) are diagrams showing the stress generated at the cross-shaped joint. [Figure 3] FIG. 2(b) is a diagram showing a schematic diagram of the stress generated in the cross-shaped joint surrounded by four sleeve walls. [Figure 4] (a) and (b) are diagrams showing the stress generated at the cross-shaped joint. [Figure 5] FIG. 4(b) is a diagram showing a schematic diagram of stress occurring in the cross-shaped joint surrounded by four sleeve walls. [Figure 6](a) and (b) are diagrams showing the stress generated in a T-shaped joint when sleeve walls are installed above and below the beam. [Figure 7] (a) and (b) are diagrams showing the stresses generated in a T-shaped joint when sleeve walls are installed on both sides of the column. [Figure 8] (a) and (b) are diagrams showing the stress generated at the L-shaped joint where the sleeve wall is installed. [Figure 9] (a) and (b) are diagrams showing the stress generated at the cross-shaped joint. [Figure 10] 1(a) is an enlarged view of the part surrounded by the dashed line in FIG. 1(b), and FIG. 1(b) is a cross-sectional view taken along line AA in FIG. 1(a). [Figure 11] In Figure 10(b), the main reinforcement and horizontal reinforcement of the column, the main reinforcement, end reinforcement, spiral reinforcement and post-installed anchors of the sleeve wall are not shown. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0016] The design standards for beam-column joints in reinforced concrete buildings will be explained using Figs. 1 to 11. In the rigid frame structure of a reinforced concrete building, as shown in Figure 1(a), four types of column-beam joints 3 called cross joints 3a, T-shaped joints 3b, T-shaped joints 3c, and L-shaped joints 3d are formed by rigidly joining columns 1 and beams 2. Also, as shown in Figure 1(b), sleeve walls 5 are often installed in reinforced concrete frames 4 made up of a pair of columns 1, 1 and a pair of beams 2, 2 to increase earthquake resistance. The area surrounded by the pair of beams 2, 2 and the pair of sleeve walls 5, 5 forms an opening 6. When the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and the beams 2 arranged on both sides of the beam-column joint 3 are deformed as shown in Figure 2(a), stresses as shown in Figures 2(a) and 2(b) are generated in the cross-shaped joint 3a. Note that the deformed state of the beam 2 is the same in Figures 2(a) and 2(b), but in Figure 2(a) the deformed state of the beam 2 is exaggerated more than in Figure 2(b) to make it easier to intuitively visualize the deformed state. Furthermore, in Figure 2(a), the reinforcing bars shown in Figure 2(b) are omitted, and the outlines of the column 1 and beam 2 are shown with dashed lines in Figures 2(a) and 2(b).

[0017] As shown in Figure 2(b), multiple main reinforcements 1a are arranged parallel to the axial direction in the column 1, and multiple transverse reinforcements 1b are arranged horizontally to surround these main reinforcements 1a. Additionally, multiple upper end main reinforcements 2a and lower end main reinforcements 2b and web reinforcements 2c are arranged parallel to the longitudinal direction in the beam 2, and multiple stirrups 2d are arranged to surround these reinforcing bars. The upper end main reinforcements 2a and lower end main reinforcements 2b are arranged above and below the beam 2, respectively, and the web reinforcements 2c are arranged between these main reinforcements. As shown in Figures 2(a) and 2(b), the cruciform joint 3a receives a compressive force Cg and a tensile force Tg from the upper and lower parts of the beam 2 located on one side of the column 1, respectively, and also receives a tensile force Tg and a compressive force Cg from the upper and lower parts of the beam 2 located on the other side of the column 1. Furthermore, the cruciform joint 3a receives a shear force Vc from the columns 1 located above and below the beam 2, respectively. As a result, a shear force Vj1 is generated in the cruciform joint 3a as shown in the following equation (1).

[0018]

number

[0019] When a horizontal load is applied to a rigid frame structure with four sleeve walls 5 surrounding the cruciform joint 3a as shown in Figure 3, stresses are generated in the cruciform joint 3a as explained above using Figures 2(a) and 2(b). Since the sleeve walls 5 bear part of the tensile force Tg and compressive force Cg from the beam 2 as shown in Figure 3, the actual force the cruciform joint 3a receives from the beam 2 is reduced by the amount of the force borne by the sleeve walls 5. Furthermore, the cruciform joint 3a receives a shear force Vc' instead of the shear force Vc from the column 1 reinforced by the sleeve walls 5. Therefore, if the tensile force Tg and compressive force Cg borne by the sleeve walls 5 from the beam 2 are ΔT and ΔC, respectively, a shear force Vj1' is generated in the cruciform joint 3a as shown in the following equation (2):

[0020]

number

[0021] When the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and column 1 is deformed as shown in Figure 4(a), stresses as shown in Figures 4(a) and 4(b) are generated in the cross-shaped joint 3a. Note that the deformed state of column 1 is the same in Figures 4(a) and 4(b), but in Figure 4(a) the deformed state of column 1 is exaggerated more than in Figure 4(b) to make it easier to intuitively visualize the deformed state. Furthermore, in Figure 4(a), the reinforcing bars shown in Figure 4(b) are omitted, and in Figures 4(a) and 4(b) the outlines of column 1 and beam 2 are shown with dashed lines. As shown in Figures 4(a) and 4(b), the cruciform joint 3a receives a compressive force Cc and a tensile force Tc from the column 1 located above the beam 2, and also receives a tensile force Tc and a compressive force Cc from the column 1 located below the beam 2. Furthermore, the cruciform joint 3a receives a shear force Vg from the beams 2 located on both sides of the column 1. As a result, a shear force Vj2 is generated in the cruciform joint 3a as shown in the following equation (3).

[0022]

number

[0023] When a horizontal load is applied to a rigid frame structure with four sleeve walls 5 surrounding the cruciform joint 3a as shown in Figure 5, stresses are generated in the cruciform joint 3a as explained above using Figures 4(a) and 4(b). Since the sleeve walls 5 bear part of the tensile force Tc and compressive force Cc from the column 1 as shown in Figure 5, the actual force the cruciform joint 3a receives from the column 1 is reduced by the amount of the force borne by the sleeve walls 5. Furthermore, the cruciform joint 3a receives a shear force Vg' instead of the shear force Vg from the beam 2 reinforced by the sleeve walls 5. Therefore, if the tensile force Tc and compressive force Cc borne by the sleeve walls 5 are ΔT and ΔC, respectively, the shear force Vj2' is generated in the cruciform joint 3a as shown in the following equation (4):

[0024]

number

[0025] When the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and the beam 2 is deformed as shown in Figure 2(a), the T-shaped joint 3b, where two sleeve walls 5 are installed above and below the beam 2, is subjected to compressive force Cg and tensile force Tg from the top and bottom of the beam 2, respectively, as shown in Figure 6(a), and is also subjected to shear force Vc' from the column 1, which is reinforced by the sleeve walls 5. At this time, since part of the tensile force Tg and compressive force Cg received from the beam 2 is borne by the sleeve walls 5, the forces that the T-shaped joint 3b actually receives from the beam 2 are reduced by the forces ΔT and ΔC borne by the sleeve walls 5, respectively. As a result, shear forces Vj3' and Vj4' are generated in the T-shaped joint 3b as shown in the following equations (5) and (6).

[0026]

number

[0027]

number

[0028] When the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and column 1 is deformed as shown in Figure 4(a), the T-shaped joint 3b, where two sleeve walls 5 are installed above and below beam 2, receives a compressive force Cc and a tensile force Tc from the column 1 located above beam 2, respectively, as well as a tensile force Tc and a compressive force Cc from the column 1 located below beam 2, respectively, as shown in Figure 6(b). Furthermore, T-shaped joint 3b receives a shear force Vg' from column 1 reinforced by sleeve walls 5. Since the sleeve walls 5 bear a portion of the tensile force Tc and compressive force Cc received from column 1, the actual force received by T-shaped joint 3b from column 1 is reduced by the forces (ΔT and ΔC) borne by the sleeve walls 5. As a result, shear forces Vj5' and Vj6' are generated in T-shaped joint 3b as shown in the following equations (7) and (8).

[0029]

number

[0030]

number

[0031] When the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and the beam 2 is deformed as shown in Figure 2(a), the T-joint 3c, where two sleeve walls 5 are installed on both sides of the column 1, receives a compressive force Cg and a tensile force Tg from the top and bottom of the beam 2, respectively, as shown in Figure 7(a), and also receives a shear force Vc' from the beam 2 reinforced by the sleeve walls 5. At this time, because part of the tensile force Tg and compressive force Cg received from the beam 2 is borne by the sleeve walls 5, the forces that the T-joint 3c actually receives from the beam 2 are reduced by the forces (ΔT and ΔC) borne by the sleeve walls 5. As a result, shear forces Vj7' and Vj8' are generated in the T-joint 3c as shown in the following equations (9) and (10).

[0032]

number

[0033]

number

[0034] When the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and the column 1 is deformed as shown in Figure 4(a), the T-joint 3c, where two sleeve walls 5 are installed on both sides of the column 1, receives a compressive force Cc and a tensile force Tc from the column 1 located below the beam 2 as shown in Figure 7(b), and also receives a shear force Vg' from the column 1 reinforced by the sleeve walls 5. At this time, since part of the tensile force Tc and compressive force Cc received from the column 1 is borne by the sleeve walls 5, the forces that the T-joint 3c actually receives from the column 1 are reduced by the forces (ΔT and ΔC) borne by the sleeve walls 5. As a result, the T-joint 3c receives shear forces Vj9' and Vj as shown in the following equations (11) and (12). 10 ' occurs.

[0035]

number

[0036]

number

[0037] When the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and the beam 2 is deformed as shown in Figure 2(a), the L-shaped joint 3d, where one sleeve wall 5 is installed, receives a compressive force Cg and a tensile force Tg from the top and bottom of the beam 2, respectively, as shown in Figure 8(a), and also receives a shear force Vc' from the beam 2, which is reinforced by the sleeve wall 5. At this time, since part of the tensile force Tg received from the beam 2 is borne by the sleeve wall 5, the force that the L-shaped joint 3d actually receives from the beam 2 is reduced by the force ΔT borne by the sleeve wall 5. As a result, the L-shaped joint 3d receives a shear force Vj as shown in the following equations (13) and (14): 11 ′ and Vj 12 ' occurs.

[0038]

number

[0039]

number

[0040] When the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and column 1 is deformed as shown in Figure 4(a), L-shaped joint 3d, where one sleeve wall 5 is installed, receives a compressive force Cc and a tensile force Tc from column 1 located below beam 2 as shown in Figure 8(b), and also receives a shear force Vg' from beam 2 reinforced by sleeve wall 5. At this time, part of the tensile force Tc received from column 1 is borne by sleeve wall 5, so the force that L-shaped joint 3d actually receives from column 1 is reduced by the force ΔT borne by sleeve wall 5. As a result, shear force Vj as shown in the following equations (13) and (14) is applied to L-shaped joint 3d. 13 ′ and Vj 14 ' occurs.

[0041]

number

[0042]

number

[0043] Here, we will explain the transverse reinforcement ratio of the beam-column joint 3 (see Figure 1(a)). w , the width of column 1 is b c , the distance between the center of gravity of the upper end main reinforcement 2a and the lower end main reinforcement 2b of the beam 2 is j, the horizontal reinforcement ratio p of the column beam joint 3 jwis defined as the following equation (17) in the "RC Bearing Strength Standards." When two or more sets of transverse reinforcement 1b are installed, equation (17) can be rewritten as equation (18) by multiplying the right side of equation (17) by the number of sets of transverse reinforcement 1b, which is calculated by dividing the distance j between the centers of gravity of the upper main reinforcement 2a and the lower main reinforcement 2b of beam 2 by the arrangement pitch S of transverse reinforcement 1b.

[0044]

number

[0045]

number

[0046] Regarding the effect of the lateral reinforcement ratio β in the cross-shaped joint 3a and the L-shaped joint 3d, the following formula (19) is stated in the "RC Strength Standards". However, ΣA jw is the sum of the cross-sectional areas of the transverse reinforcement 1b arranged between the upper end main reinforcement 2a and the lower end main reinforcement 2b of the beam 2, and f jy is the yield stress of the transverse reinforcement 1b, and ΣA t and f y are the cross-sectional area of ​​the upper end main reinforcement 2a or the lower end main reinforcement 2b on the tension side of the beam 2, and the yield stress of those reinforcements. Note that in the cross-shaped joint 3a and the L-shaped joint 3d, two beams 2 are connected to the beam-column joint 3, whereas in the T-shaped joint 3b and the T-shaped joint 3c, only one beam 2 is connected to the beam-column joint 3. Therefore, the effect of the transverse reinforcement ratio in the T-shaped joint 3b and the T-shaped joint 3c is defined as twice the effect β of the transverse reinforcement ratio in the cross-shaped joint 3a and the L-shaped joint 3d.

[0047]

number

[0048] ΣA in equation (19) jw is the number of sets n of horizontal reinforcement 1b existing between the upper end main reinforcement 2a and the lower end main reinforcement 2b of beam 2 Wand the cross-sectional area a of a set of horizontal reinforcement bars 1b w multiplied by ΣA t ·f y corresponds to the tensile force Tg or the compressive force Cg received by the beam-column joint 3 from the beam 2. Further, as shown in Equation (20), the number of sets n of the horizontal reinforcement bars 1b existing between the upper main reinforcement bars 2a and the lower main reinforcement bars 2b of the beam 2 W is obtained by dividing the distance d between the upper main reinforcement bars 2a and the lower main reinforcement bars 2b of the beam 2 g by the arrangement pitch S of the horizontal reinforcement bars 1b. Therefore, if the above-mentioned tensile force Tg is set as T, Equation (19) can be rewritten as Equation (21).

[0049]

Equation

[0050]

Equation

[0051] If the force ΔT borne by the sleeve wall 5 among the tensile force T is set as k1T (where 0 < k1 ≤ 1), the effect β1 of the horizontal reinforcement ratio in the cruciform joint 3a and the L-shaped joint 3d when the sleeve wall 5 is installed is represented by Equation (22). On the other hand, according to the new design standard, when the arrangement pitch of the horizontal reinforcement bars 1b is changed from the current S to S / k2 (where 1 < k2), the effect β2 of the horizontal reinforcement ratio in the cruciform joint 3a and the L-shaped joint 3d is represented as in Equation (23). In order to achieve an effect equal to or greater than the case where the new design standard is satisfied by installing the sleeve wall 5 etc. without changing the arrangement pitch of the horizontal reinforcement bars 1b, it is necessary that the relationship shown in Equation (24) holds between β1 and β2. Note that Equation (25) is obtained from Equations (22) to (24).

[0052]

Equation

[0053]

Equation

[0054]

number

[0055]

number

[0056] According to formula (18), changing the arrangement pitch of the transverse reinforcement 1b from the current S to S / k2 reduces the transverse reinforcement ratio p jw That is, equation (25) is equivalent to multiplying the transverse reinforcement ratio p jw This means that even if the design standards for this are increased to k2 times the current standard, by making the force ΔT borne by the sleeve wall 5 at least (1-1 / k2) times the tensile force T received from the beam 2 at the beam-to-column joint 3, it is possible to obtain the same or greater effect as in the new design standards for the transverse reinforcement ratio.

[0057] As already mentioned, the effect of the transverse reinforcement ratio in the T-shaped joint 3b and the T-shaped joint 3c is twice the effect β of the transverse reinforcement ratio in the cross-shaped joint 3a and the L-shaped joint 3d. However, even if the left-hand sides of the formulas (22) and (23) are doubled, k2 is determined by the ratio of β1 to β2, so the relationship between k1 and k2 shown in formula (25) still holds. Therefore, the transverse reinforcement ratio p of the beam-column joint 3 jw The explanation that when the design criteria for this are multiplied by the current k2, the ratio of ΔT to tensile force T needs to be (1-1 / k2) or more applies to the effect of the transverse reinforcement ratio in the T-shaped joint 3b and the T-shaped joint 3c, just as it applies to the effect of the transverse reinforcement ratio in the cross-shaped joint 3a and the L-shaped joint 3d.

[0058] Also, if the compressive force Cg received by the beam-column joint 3 from the beam 2 is denoted as C, and the force borne by the sleeve wall 5 among this C is denoted as ΔC, then since T and C are in balance and have the same magnitude, and T - ΔT and C - ΔC are also in balance and have the same magnitude, assuming ΔC as k1C (where 0 < k1 ≤ 1), T in equations (22) and (23) can be replaced with C for consideration. In this case, from equations (24) and (25), the transverse reinforcement ratio p of the beam-column joint jw Even when the design standard regarding jw becomes k2 times the current one, by making the force ΔC borne by the sleeve wall 5 be (1 - 1 / k2) times or more of the compressive force C received by the beam-column joint 3 from the beam 2, the conclusion that the effect of the transverse reinforcement ratio equivalent to or greater than that in the new design standard can be obtained is similarly derived. As described above, in the "RC Retained Strength Standard", the design standard for beam-column joints has been strengthened, and a new seismic resistance standard with a transverse reinforcement ratio of 1.5 times is being prepared. In this case, since k2 in equation (25) becomes 1.5, it can be seen that k1 should be 1 / 3 or more. This means that jw Even when the design standard regarding the transverse reinforcement ratio p of the beam-column joint 3 becomes 1.5 times the current one, by making the force ΔT borne by the sleeve wall 5 be 1 / 3 or more of the tensile force T received by the beam-column joint 3 from the beam 2, the effect of the transverse reinforcement ratio equivalent to or greater than that in the new design standard can be obtained. Note that the same effect can also be obtained when the force ΔC borne by the sleeve wall 5 is made 1 / 3 or more of the compressive force C received by the beam-column joint 3 from the beam 2.

[0059] As already described, when the ramen structure shown in Fig. 1(a) receives a horizontal load and the beams 2 arranged on both sides of the beam-column joint 3 are deformed as shown in Fig. 2(a), the cruciform joint 3a receives the compressive force Cg and the tensile force Tg from the beams 2. As a result, as shown in Fig. 9(a), stress that causes diagonal cracks 12 occurs in the cruciform joint 3a. However, since the transverse reinforcement 1b of the column 1 (see Fig. 2(b)) is installed so as to straddle the possible locations where the cracks 12 may occur, even if the cracks 12 occur, the transverse reinforcement 1b acts to connect the parts on both sides of the crack and prevent the expansion of the cracks 12. On the other hand, when the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and column 1 is deformed as shown in Figure 4(a), the cruciform joint 3a receives a compressive force Cc and a tensile force Tc from column 1. As a result, as shown in Figure 7(b), stress that causes a diagonal crack 12 is generated in the cruciform joint 3a, but when crack 12 occurs, the above-mentioned horizontal reinforcement 1b of column 1 (see Figure 4(b)) acts to connect both sides of the crack 12 and prevent the crack 12 from expanding.

[0060] Thus, the transverse reinforcement 1b of the column 1, which is installed assuming that the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and the beams 2 arranged on both sides of the beam-column joint 3 deform as shown in Figure 2(a), also has the effect of preventing the expansion of the crack 12 when the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and the column 1 deforms as shown in Figure 4(a). In other words, the above explanation regarding the effect β of the transverse reinforcement ratio at the beam-column joint 3, assuming that the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and the beams 2 arranged on both sides of the beam-column joint 3 deform as shown in Figure 2(a), also applies when the column 1 deforms as shown in Figure 4(a). Therefore, we will omit the explanation of the effect β of the transverse reinforcement ratio at the beam-column joint 3, assuming that the rigid frame structure shown in Figure 1(a) is subjected to a horizontal load and the column 1 deforms as shown in Figure 4(a).

[0061] Here, a sleeve wall addition reinforcement structure according to an embodiment of the present invention will be explained using Figure 10. To avoid the diagrams becoming too complicated, in Figures 10(a) and 10(b), only some of the main reinforcement bars, end reinforcement bars, post-installed anchors, and ties are labeled. Also, in Figure 10(a), the main reinforcement bars and ties inside the column are not shown, and in Figure 10(b), the sleeve wall to be added is shown with a dashed line, and the hatching indicating a cross section is omitted. As shown in Figures 10(a) and 10(b), in the sleeve wall addition reinforcement structure of the present invention, a sleeve wall 5 made of reinforced concrete 7a is installed inside the RC frame 4 (see Figure 1(b)). The reinforced concrete 7a is formed using non-shrinkage mortar or non-shrinkage concrete with adhesive properties, and a water absorption adjuster is applied to the interface between the column 1 and pair of beams 2, 2 and the sleeve wall 5 (the joint surfaces between the reinforced concrete 7b and reinforced concrete 7c that respectively constitute the column 1 and beam 2 and the reinforced concrete 7a that constitutes the sleeve wall 5).

[0062] Some of the post-installed anchors 8 are embedded in the pair of beams 2 and the column 1, and the remaining portions of the post-installed anchors 8 are embedded in the reinforced concrete 7a that forms the sleeve wall 5. In the reinforced concrete 7a, a plurality of main reinforcements 9a are arranged parallel to the axial direction of the column 1, and near the opening 6, end reinforcement bars 10 are arranged parallel to the main reinforcement bars 9a. Furthermore, the main reinforcement bars 9a and end reinforcement bars 10 are surrounded by a plurality of horizontally arranged transverse reinforcement bars 9b, and spiral reinforcement bars 11 are arranged parallel to the axial direction of the column 1 and the pair of beams 2. In the reinforced concrete 7b that forms the column 1, a plurality of main reinforcement bars 1a are arranged parallel to the axial direction, and these main reinforcement bars 1a are surrounded by a plurality of horizontally arranged transverse reinforcement bars 1b.

[0063] In this way, when the sleeve wall 5 is formed from non-shrinkage mortar or non-shrinkage concrete, there is an advantage that, unlike when it is formed from ready-mixed concrete, a concrete pump truck or agitator truck is not required. Furthermore, since the processes of pouring ready-mixed concrete and filling with non-shrinkage mortar are not required during construction, the construction period and manufacturing costs for constructing the sleeve wall 5 are shortened. This makes it possible to install the sleeve wall 5 inside the RC frame 4 efficiently in a short period of time at low cost.

[0064] The non-shrinkage mortar or non-shrinkage concrete forming the sleeve wall 5 is selected from commercially available non-shrinkage mortars with an adhesive strength of 1.5 N / mm2 The above materials can be selected and used. In this specification, "non-shrinkage mortar" refers to a material whose expansion rate measured in accordance with the Japan Society of Civil Engineers standard JSCE-F 542-2013 "Test method for bleeding rate and expansion rate of filled mortar" does not show a negative value, and this material is composed of a premix grout composition containing cement, expansive material, aggregate, cement dispersant, thickener, and foaming agent. Specifically, this material contains 15 to 45% by mass of particles exceeding 4 mm and not exceeding 10 mm in size relative to the total mass of the aggregate, and the ratio of aggregate to binder (a / B) is 1.8 to 3.0 by mass. The binder (B) includes cement, gypsum, pozzolans such as silica fume and metakaolin, latent hydraulic substances such as blast furnace slag powder, and expansive agents. Furthermore, this material preferably contains, as aggregate, 40 to 65 mass% of particles larger than 0.3 mm and not larger than 4 mm, 30 to 55 mass% of particles larger than 0.3 mm and not larger than 2.5 mm, 1 to 45 mass% of particles not larger than 0.3 mm, and 10 mass% or less of particles not larger than 0.15 mm, based on the total mass of the aggregate; and preferably contains 1 to 10 mass% of an expanding agent and 0.01 to 5 mass% of a cement dispersant, based on the total mass of the premix grout composition.

[0065] This material does not shrink during construction, has a long-term drying shrinkage rate of 800μ or less, has excellent fluidity, and is resistant to material separation, making it ideal for constructing the sleeve wall 5. Therefore, when the sleeve wall 5 is formed from this material, the aforementioned effect of being able to install the sleeve wall 5 efficiently and in a short period of time at low cost is reliably achieved. In addition, this material has an adhesive strength (a load is applied to two adherends, and the load at which the adhesive breaks is divided by the adhesive area) of 1.5 N / mm 2For the above reasons, when the sleeve wall 5 shown in Figure 10(a) or 10(b) is formed using this material, the adhesive strength at the joint surface between the reinforced concrete 7b and reinforced concrete 7c that respectively constitute the column 1 and the pair of beams 2, 2, and the reinforced concrete 7a becomes strong. As a result, the column 1, the pair of beams 2, 2, and the sleeve wall 5 are formed almost simultaneously, which alleviates the approximately 20% reduction in shear strength required with conventional sleeve wall reinforcement.

[0066] Furthermore, commercially available water absorption control materials such as acrylic resin, epoxy resin, vinyl ester resin, and urethane resin can be used at the interface between the column 1 and pair of beams 2, 2 shown in Figures 10(a) and 10(b) and the sleeve wall 5. When this material is applied to the interface, water absorption into the surfaces of the reinforced concrete 7b, 7c, and 7a that respectively constitute the column 1, beam 2, and sleeve wall 5 is suppressed, thereby further enhancing the adhesive strength at the interface between the column 1 and pair of beams 2, 2 and the sleeve wall 5. This further enhances the effects of installing the sleeve wall 5 efficiently and at low cost in a short period of time, and mitigating the reduction in shear strength.

[0067] Next, the projection length of the sleeve wall 5 will be explained using Figure 11. To avoid cluttering the drawing, only some of the post-installed anchors are labeled with reference numerals in Figure 11. Also, hatching indicating a cross section of the sleeve wall 5 has been omitted in Figure 11. In Figure 11, the longitudinal section (cross section perpendicular to the axial direction) of beam 2 is a rectangle with a width of 400 mm and a depth (length perpendicular to the width) of 800 mm, and is called D22 (cross section area 387 mm 2 , yield stress 345N / mm 2 ) are installed in beam 2 as upper main reinforcement 2a, lower main reinforcement 2b, and web reinforcement 2c (see Figure 2(b)), two each. When T (unit: N) shown in equation (21) etc. is calculated using equation (26), it becomes 801090N. Furthermore, when ΔT (unit: N) is calculated using equation (27) with the aforementioned k1 set to 1 / 3, it becomes 267030N.

[0068]

number

[0069]

number

[0070] Equation (28) is known as an example of a formula for calculating the shear strength Q (unit: N) when the concrete part of the sleeve wall 5 in which the post-installed anchor 8 is embedded breaks. However, s a e is the cross-sectional area of ​​the post-installed anchor 8, and σ B and E c are the compressive strength of concrete (for a standard existing beam, 17.6N / mm 2 ) and Young's modulus (for a standard existing beam, 22258N / mm 2 ) The number n of post-installed anchors 8 can be calculated using equation (29).

[0071]

number

[0072]

number

[0073] It is called D16 (cross-sectional area 199 mm 2 ) are placed in the sleeve wall 5 at a pitch of 150 mm, the above-mentioned shear strength Q is calculated as 49,821 N according to formula (28). Substituting this value of Q (49,821 N) and the value of ΔT (267,030 N) into formula (29), the value 5.36 is obtained. Since n is an integer, the number of post-installed anchors 8, n, is 6. Therefore, if the shortest distance between the pair of side surfaces 5a, 5a of the sleeve wall 5 parallel to the joint surface 1c of the column 1 and the center of the post-installed anchor 8 is set to, for example, 1 / 2 of the above-mentioned pitch (150 mm), the projection length L of the sleeve wall 5 will be 450 mm, as shown in Figure 11. [Industrial Applicability]

[0074] The sleeve wall addition reinforcement structure and sleeve wall addition reinforcement method of the present invention can be applied when installing new sleeve walls in reinforced concrete buildings for the purpose of reinforcing the reinforced concrete frame. [Explanation of symbols]

[0075] 1…Column 1a…Main reinforcement 1b…Horizontal reinforcement 1c…Joint surface 2…Beam 2a…Top main reinforcement 2b…Bottom main reinforcement 2c…Abdominal reinforcement 2d…Stirrup 3…Column-beam joint 3a…Cross-shaped joint 3b…T-shaped joint 3c…T-shaped joint 3d…L-shaped joint 4…RC frame 5…Sleeve wall 5a…Side 6…Opening 7a~7c...Reinforced concrete 8...Later installed anchor 9a...Main reinforcement 9b...Horizontal reinforcement 10...End reinforcement 11...Spiral reinforcement 12...Crack Cc, Cg...Compressive force Tc, Tg...Tensile force Vc, Vc'...Shear force Vg, Vg'...Shear force Vj1, Vj2...Shear force Vj1'~Vj 14 '...Shear force ΔC, ΔT...Force borne by sleeve wall

Claims

1. A sleeve wall reinforcement structure in which sleeve walls are added to reduce the shear force generated at the beam-column joints formed by beams and columns in a reinforced concrete building. A sleeve wall addition reinforcement structure characterized in that, when the tensile force T and compressive force C that the column-beam joint receives from the beam or column are defined as ΔT and ΔC, respectively, the forces that flow to the sleeve wall through the joint surface between the sleeve wall and the beam or column and are borne by the sleeve wall, the sleeve wall is installed so that at least one of ΔT / T or ΔC / C is 1 / 3 or more.

2. 2. The sleeve wall extension reinforcement structure according to claim 1, wherein the joint between the beam or the column and the sleeve wall is joined using a post-installed anchor.

3. The sleeve wall is 1.5 N / mm ２ 3. The sleeve wall extension reinforcement structure according to claim 1 or 2, characterized in that it is made of reinforced concrete formed using non-shrinkage mortar or non-shrinkage concrete having the above adhesive strength.

4. This is a sleeve wall reinforcement method for adding sleeve walls in reinforced concrete buildings in order to reduce the shear force generated at the beam-column joints formed by beams and columns. A sleeve wall addition reinforcement method characterized by installing the sleeve wall so that at least one of ΔT / T or ΔC / C is 1 / 3, where ΔT and ΔC are the tensile force T and compressive force C that the column-beam joint receives from the beam or column, and the forces that flow into the sleeve wall through the joint surface between the sleeve wall and the beam or column and are borne by the sleeve wall, respectively.

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