Reinforced concrete beam

Abstract

To provide a reinforced concrete beam provided with a beam reinforcement having high strength and excellent workability, and hardly causing cracks.SOLUTION: Provided is a reinforced concrete beam 200 including a beam reinforcement 100 inside the concrete. The beam reinforcement 100 includes a lower stirrup unit 50 in which a plurality of first stirrups 10 are arranged at a predetermined pitch and upper main reinforcements 30 are fully welded, an upper stirrup unit 60 in which a plurality of second stirrups 20 are arranged at a predetermined pitch and are not integrated with each other, and lower main reinforcements 70 connected to the inside of the first stirrups 10. The cross section perpendicular to the longitudinal direction thereof has an inverted T shape consisting of a lower rectangular portion 150 having a first width w1 and an upper rectangular portion 160 having a second width w2 narrower than the first width w1. The lower part of a hanging reinforcement 22 is located in the lower rectangular portion 150.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to reinforced concrete beams. [Background technology]

[0002] When arranging beam reinforcement for beams that connect foundation beams or columns of a building, a construction method using so-called welded reinforcing bars is sometimes applied to streamline the work of arranging multiple stirrups on-site while measuring the pitch between the stirrups along the longitudinal direction of the beam reinforcement, attaching horizontal reinforcement (abdominal reinforcement) to the vertical reinforcement that constitutes the stirrups by bundling, etc., and connecting multiple main reinforcement bars to the top and bottom inside of the stirrups. This welded reinforcing bar is, for example, formed into a unit by welding the stirrups and horizontal reinforcement in advance in a factory, etc. Such welded reinforcing bars are delivered to the construction site, and closed stirrups are arranged by connecting, for example, the upper unit and the lower unit on-site. Then, upper and lower main reinforcement bars are arranged on the top and bottom inside of the closed stirrups, and the beam reinforcement is arranged by bundling, etc.

[0003] Here, a reinforcement structure and reinforcement method for beam reinforcement has been proposed, in which a lower unit in which multiple stirrups are unitized by upper end main reinforcement and lower end main reinforcement is covered with a cap tie that does not have a hook and reinforced (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-29249 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the beam reinforcement described in Patent Document 1, the upper stirrups, which are cap ties, do not have hooks, and the cap ties are only slightly wrapped around the lower stirrups, so it is unclear whether the beam reinforcement has sufficient strength.

[0006] According to the 2021 Guidelines and Commentary for Reinforcement Arrangements in Reinforced Concrete Structures (Architectural Institute of Japan), the cap-tie reinforcement specification described above calls for, for example, a 135-degree hook to be attached to the upper end of the lower stirrup, and for the lower stirrup and cap tie to overlap with a lap splice length of 6d (d is the name for deformed reinforcing bars). Considering these general specifications, it must be said that it is unclear whether the strength of the cap-tie beam reinforcement described in Patent Document 1 is sufficient, in other words, whether the upper and lower stirrups form a closed reinforcing bar with sufficient strength.

[0007] In particular, with closed-type reinforcing bars having a small beam width, it is difficult to ensure a sufficient lap splice length as described above, making it difficult to form closed-type reinforcing bars with sufficient strength.

[0008] Therefore, in such a closed type reinforcing bar with a small beam depth, a plurality of U-shaped lower stirrups that are open upward are arranged so as to cover a plurality of U-shaped upper stirrups that are open downward, and then multiple stages (for example, two stages) of horizontal bars are welded to a plurality of downward hanging reinforcing bars that constitute the upper stirrups, and the horizontal bars are used as hook substitutes for the upper stirrups, thereby making it possible to shorten the length of the lap splices between the upper and lower stirrups as much as possible and to form a closed type reinforcing bar with a small beam depth that has sufficient strength.

[0009] However, since multiple rows of horizontal reinforcement are arranged protruding from the sides of the upper stirrups, there is a risk that the horizontal reinforcement may become the starting point of cracks and accelerate the cracks.

[0010] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a reinforced concrete beam that has high-strength beam bars with excellent workability and is less likely to crack. [Means for solving the problem]

[0011] In order to achieve the above object, one aspect of the reinforced concrete beam according to the present invention is as follows: A reinforced concrete beam having beam reinforcement inside the concrete, The beam reinforcement is a lower stirrup unit in which first stirrups are arranged at a predetermined pitch, each having a U-shape that opens upward and having bottom reinforcing bars and rising reinforcing bars rising upward from the left and right ends of the bottom reinforcing bar, and each first stirrup is connected to the corresponding left and right rising reinforcing bars by full-strength welding of the upper end main reinforcing bars at the inside of the upper ends of the rising reinforcing bars; an upper stirrup unit having a U-shape that opens downward, and having a top reinforcement portion and hanging reinforcement portions that hang down from the left and right ends of the top reinforcement portion and extend to the bottom reinforcement portion, and having no hooks at the ends of the hanging reinforcement portions, and each second stirrup is arranged at a predetermined pitch and is not integrated with another; The bottom reinforcement portion forming the first stirrup and the rising reinforcement portion have a lower end main reinforcement connected to the inside of the bent portion at the boundary thereof, When the upper stirrup unit is placed over the lower stirrup unit, the rising portion of the corresponding first stirrup and the hanging portion of the corresponding second stirrup overlap, and the hanging portion extends to the side of the lower end main reinforcement, The cross-sectional shape of the reinforced concrete beam perpendicular to the longitudinal direction is an inverted T shape in which a lower rectangular portion having a first width and an upper rectangular portion having a second width narrower than the first width are connected, The bottom reinforcement section, the lower end main reinforcement section, and the lower part of the hanging reinforcement section are located in the lower rectangular section.

[0012] According to this aspect, the rising reinforcement sections of the lower stirrup unit, in which the first stirrups are integrated at the upper main reinforcement, overlap with the hanging reinforcement sections of the upper stirrup unit, in which the second stirrups are not integrated with each other, and each hanging reinforcement section extends to the side of the lower main reinforcement section. The cross section perpendicular to the longitudinal direction of the reinforced concrete beam has an inverted T-shape consisting of a lower rectangular section with a first width and an upper rectangular section with a second width narrower than the first width, and the lower parts of the hanging reinforcement sections are located in the lower rectangular section, so that the lower parts of the hanging reinforcement sections are restrained by the lower rectangular section. This eliminates the need for both hooks at the ends of the second stirrups and horizontal reinforcements connecting the second stirrups. This makes it possible to form a reinforced concrete beam with excellent deformation performance and high strength, while preventing the horizontal reinforcement sections from becoming crack starting points.

[0013] Here, the "full-strength welding" that connects the first stirrup and the upper main reinforcement in the lower stirrup unit is also called "full-strength rebar cross welding," and refers to spot welding in which the weld has strength equal to or greater than the JIS yield point of the stirrup, the elongation of the main reinforcement is equal to or greater than the JIS value of the rebar before welding, and the shear strength of the weld is equal to or greater than the short-term allowable tensile strength of the stirrup. Note that normal spot welding ensures that the weld is approximately 1 / 3 to 2 / 3 of the JIS yield point of the rebar. This full-strength welding is a welding method in which normal spot welding is repeated two or more times, and a second spot welding is performed after the first spot welding to anneal the weld before it cools rapidly.

[0014] In the lower stirrup unit, each first stirrup does not have a hook, but the upper main reinforcement, which is joined to the rising part of each first stirrup by full strength welding, functions as a hook substitute reinforcement.

[0015] In addition, the lower end main reinforcement, which is not necessarily included in the lower stirrup unit, is connected to the inside of the bend at the boundary between the bottom reinforcement and the rising reinforcement that form the first stirrup. This lower end main reinforcement may also be connected to the first stirrup by full strength welding or tied with a tie wire. On the other hand, the "welding" that connects the multiple second stirrups and transverse reinforcements in the upper stirrup unit means welding in a broad sense, which means not only full strength welding but also general spot welding.

[0016] On the other hand, there are no hooks in the hanging parts of the second stirrups constituting the upper stirrup unit, and there are no horizontal bars connecting the hanging parts. In this embodiment, the second stirrups are separated from each other without being connected by horizontal bars, but the embodiment in which multiple second stirrups are arranged at a predetermined pitch is called an "upper stirrup unit."

[0017] When a tensile force acts on the second stirrups, the hanging reinforcement tends to open to the side. Conventional hanging reinforcement with hooks is based on a design concept that prevents the hanging reinforcement from opening to the side by the restraining effect of the hooks, and the configuration in which multiple hanging reinforcement sections are connected by horizontal reinforcement as hook substitutes is also based on a design concept that prevents the hanging reinforcement from opening to the side by the restraining effect of the hook substitutes. In contrast, the hanging reinforcement section that forms the second stirrups that make up the reinforced concrete beam of this embodiment does not require hooks or horizontal reinforcement, and is based on a design concept that prevents the hanging reinforcement from opening to the side by the restraining effect of the lower rectangular section by positioning the lower part of the hanging reinforcement section in a lower rectangular section with a relatively wide first width.

[0018] In this embodiment, the rising reinforcement of the corresponding first stirrup and the hanging reinforcement of the corresponding second stirrup overlap, but the overlap length does not need to satisfy the specified lap joint length, and in principle there is no restriction on the lap length. For example, in a beam with a low beam depth, if a specified lap joint length is required for the overlap point between the rising reinforcement and the hanging reinforcement, there may be cases where the specified lap joint length is not satisfied. Therefore, in this embodiment, although the overlap point between the rising reinforcement and the hanging reinforcement does not have the specified lap joint length, the lower part of the hanging reinforcement is located at the lower end position of the beam reinforcement height (beside the bottom reinforcement and the lower end main reinforcement), thereby integrating the corresponding first stirrup and second stirrup.

[0019] Another aspect of the reinforced concrete beam according to the present invention is A reinforced concrete beam having beam reinforcement inside the concrete, The beam reinforcement is a lower stirrup unit in which first stirrups are arranged at a predetermined pitch, each having a U-shape that opens upward and having bottom reinforcing bars and rising reinforcing bars rising upward from the left and right ends of the bottom reinforcing bar, and each first stirrup is connected to the corresponding left and right rising reinforcing bars by full-strength welding of the upper end main reinforcing bars at the inside of the upper ends of the rising reinforcing bars; an upper stirrup unit that has a generally U-shape that opens downward, and has a top reinforcement section and first and second hanging reinforcement sections that hang downward from both ends of the top reinforcement section, the first hanging reinforcement section having a first vertical section and a 90-degree hook at the lower end of the first vertical section, the second hanging reinforcement section having a second vertical section that is longer than the first vertical section and does not have a hook at its end, and the second stirrups are arranged at a predetermined pitch and are not integrated with each other; The bottom reinforcement portion forming the first stirrup and the rising reinforcement portion have a lower end main reinforcement connected to the inside of the bent portion at the boundary thereof, When the upper stirrup unit is placed over the lower stirrup unit, the rising reinforcement part of the corresponding first stirrup overlaps with the first vertical part and the second vertical part of the corresponding second stirrup, and the second vertical part extends to the side of the lower end main reinforcement, The cross-sectional shape of the reinforced concrete beam perpendicular to the longitudinal direction is an inverted T shape in which a lower rectangular portion having a first width and an upper rectangular portion having a second width narrower than the first width are connected, The bottom reinforcement portion, the lower end main reinforcement, and the lower part of the second vertical portion are located in the lower rectangular portion.

[0020] According to this aspect, each second stirrup forming an upper stirrup unit has a first hanging reinforcement section and a second hanging reinforcement section, the first hanging reinforcement section has a 90-degree hook at the lower end of its first vertical section, the second hanging reinforcement section is longer than the first vertical section, and the lower part of the second vertical section without a hook at its end is located in the lower rectangular section. This makes it possible to eliminate the need for horizontal reinforcements connecting multiple second stirrups and to prevent the horizontal reinforcements from becoming the starting point of cracks, while at the same time, a high-strength reinforced concrete beam with excellent deformation performance can be formed by the restraining effect of the 90-degree hook of the first hanging reinforcement section and the restraining effect of the lower rectangular section where the lower part of the second hanging reinforcement section is located.

[0021] Here, the term "approximately U-shaped" is used because the first hanging strip has a 90-degree hook at its lower end and therefore cannot strictly be called U-shaped.

[0022] Another aspect of the reinforced concrete beam according to the present invention is The first covering of the hanging rib portion in the lower rectangular portion is at least twice the second covering of the hanging rib portion in the upper rectangular portion.

[0023] According to this aspect, the first cover is set to be twice the second cover, which further enhances the restraining effect of the lower rectangular portion on the hanging portion of the second stirrup and the second hanging portion.

[0024] Another aspect of the reinforced concrete beam according to the present invention is It is characterized by a beam height of 500 mm or less.

[0025] According to this aspect, in a reinforced concrete beam with a beam depth of 500 mm or less, although the lapped portion of the rising reinforcement and the hanging reinforcement do not have the specified lap splice length, the hanging reinforcement of the second stirrup and the lower part of the second hanging reinforcement are located at the lower end positions of the beam reinforcement (side of the bottom reinforcement or side of the lower end main reinforcement), thereby forming a reinforced concrete beam with beam reinforcement in which the first stirrup and the second stirrup are integrated. Here, "a column depth of 500 mm or less" means, for example, a beam depth in the range of 400 mm to 500 mm, and examples include reinforced concrete beams with beam depths of 400 mm or 450 mm. [Effects of the Invention]

[0026] As can be understood from the above explanation, the reinforced concrete beam of the present invention can provide a reinforced concrete beam that is equipped with beam bars that are high in strength and easy to install, and that is less likely to crack. [Brief explanation of the drawings]

[0027] [Figure 1] 1A to 1C are diagrams illustrating an example of a method for forming beam reinforcement to form a reinforced concrete beam according to an embodiment. [Figure 2] 1A to 1C are diagrams illustrating an example of a method for forming beam reinforcement. [Figure 3] 2A to 2C are diagrams illustrating an example of a method for forming beam reinforcement. [Figure 4] FIG. 1 is a perspective view of an example of a reinforced concrete beam according to an embodiment. [Figure 5] 10A to 10C are diagrams illustrating another example of a method for forming beam reinforcement to form a reinforced concrete beam according to an embodiment. [Figure 6] FIG. 10 is a perspective view of another example of a reinforced concrete beam according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, a reinforced concrete beam according to an embodiment will be described with reference to the accompanying drawings, along with its constituent elements, the beam bars, and a method for forming them. Note that in this specification and the drawings, substantially identical components will be designated by the same reference numerals, and redundant explanations may be omitted.

[0029] [Reinforced concrete beam according to the embodiment] An example of a reinforced concrete beam according to an embodiment will be described together with its constituent beam bars and a method for forming them with reference to Figures 1 to 6. Figures 1 to 3 are views illustrating an example of a method for forming beam bars that form a reinforced concrete beam according to an embodiment. Figure 4 is a perspective view of an example of a reinforced concrete beam according to an embodiment.

[0030] As shown in Figure 1, the lower stirrup unit 50 has an upwardly open U-shape, and is formed by arranging first stirrups 10, each having a bottom reinforcement section 11 and rising reinforcement sections 12 rising upward from the left and right ends of the bottom reinforcement section 11, at a predetermined pitch S in the Z direction, which is the longitudinal direction of the beam reinforcement, and connecting each first stirrup 10 to the corresponding left and right rising reinforcement sections 12 at the inside of their upper ends by the upper end main reinforcement 30.

[0031] Here, the connection between the rising reinforcing bars 12 and the upper main reinforcing bars 30 is made by full-strength welding. This full-strength welding is a welding method in which ordinary spot welding is repeated two or more times, and a second spot welding is performed after one spot welding before the weld is rapidly cooled, resulting in annealing. By this full-strength welding, the weld between the first stirrup 10 and the upper main reinforcing bars 30 has a strength equal to or greater than the JIS yield point of the first stirrup 10, the elongation of the reinforcing bars is equal to or greater than the JIS standard value of the reinforcing bars before welding, and the shear strength of the weld is equal to or greater than the short-term allowable tensile strength of the stirrup, so that both members are connected with high connection strength.

[0032] The predetermined pitch S shown in the figure is determined based on the amount of reinforcing bars required in the concrete, such as 150 mm, 200 mm, etc. The first stirrups 10 are formed, for example, from deformed steel bars, and reinforcing bars with diameters of 10 mm (D10), D13, etc. are applied, which are also determined based on the amount of reinforcing bars required in relation to the predetermined pitch S.

[0033] Deformed steel bars of a predetermined diameter are used for the upper end main reinforcements 30, and since there are two upper end main reinforcements 30 in the illustrated example, their diameters are set to satisfy the design bending moment, design shear force, etc. From the perspective of the required amount of reinforcing bars, one or more additional upper end main reinforcements 30 may be arranged between the two upper end main reinforcements 30 in the final reinforcement arrangement. For example, in the illustrated example, deformed steel bars such as D19 and D22 can be used.

[0034] On the other hand, the upper stirrup unit 60 has a U-shape that opens downwards, and the second stirrups 20, each having a top reinforcement section 21 and hanging reinforcement sections 22 hanging downward from the left and right ends of the top reinforcement section 21, are arranged at a predetermined pitch S in the Z direction, which is the longitudinal direction of the beam reinforcement, just like the first stirrups 10, and the second stirrups 20 are not connected to each other by other members such as horizontal reinforcement, and are therefore formed by a plurality of separate second stirrups 20. In other words, the upper stirrup unit 60 differs from the lower stirrup unit 50 in that it is not an integrated unit.

[0035] Here, the length of the hanging reinforcement portion 22 is L, and when the beam reinforcement intermediate body 100' shown in Figure 2 is formed, its lower end has a length that reaches the bottom reinforcement portion 11 of the first stirrup 10.

[0036] The lower ends of the hanging portions 22 of the second stirrups 20 do not have hooks, and the second stirrups 20 do not have horizontal bars connecting the lower ends of the hanging portions 22 together.

[0037] On the other hand, in the lower stirrup unit 50, the first stirrups 10 do not have hooks at the ends of the rising reinforcing bars 12, but the upper end main reinforcing bars 30 are connected by welding, so that these upper end main reinforcing bars 30 act as hook substitutes. In this way, the upper end main reinforcing bars 30 are connected to the ends of the first stirrups 10 by full strength welding, which ensures good anchorage of the first stirrups 10 in concrete, as expected from hooks.

[0038] In the illustrated example, the lower stirrup unit 50 and the upper stirrup unit 60 each have five first stirrups 10 and five second stirrups 20 at the same pitch S, but from the viewpoint of ease of transport to the site and ease of construction such as transportability on site, the unit may have six or more stirrups and be as long as possible in the Z direction.

[0039] For example, since the lower stirrup unit 50 has only the upper end main reinforcements 30 as main reinforcements and does not have the lower end main reinforcements, the weight of the lower stirrup unit 50 becomes as light as possible compared to a configuration in which the lower stirrup unit already has the lower end main reinforcements. Therefore, the lower stirrup unit 50 can be made longer in the Z direction compared to a configuration in which the lower end main reinforcements are already present. Furthermore, when such a longer lower stirrup unit 50 is prepared, the upper stirrup units 60 are also prepared with a length corresponding to the longer lower stirrup unit 50.

[0040] As shown in FIG. 1, each second stirrup 20 constituting the upper stirrup unit 60 is placed over the lower stirrup unit 50 in the X1 direction, and the rising reinforcement portion 12 of the corresponding first stirrup 10 and the hanging reinforcement portion 22 of the corresponding second stirrup 20 are overlapped and connected to form a beam reinforcement intermediate body 100' as shown in FIG. 2.

[0041] In forming this beam reinforcement intermediate body 100', since the lower stirrup unit 50 has the upper end main reinforcement 30, when the second stirrup 20 constituting the upper stirrup unit 60 is placed over the lower stirrup unit 50 from above, the second stirrup 20 can be placed on top of the two upper end main reinforcement 30.

[0042] Next, as shown in Fig. 3, the lower end main reinforcement 70 is arranged in the X2 direction inside the bend at the boundary between the bottom reinforcement part 11 and the rising reinforcement part 12 that form each first stirrup 10, and connected to form the beam reinforcement 100. Here, the lower end main reinforcement 70 is connected to the first stirrup 10 by binding with a binding wire or the like, but may also be joined by welding.

[0043] The beam reinforcement 100 in the illustrated example is a beam reinforcement of a reinforced concrete beam with a beam depth of 500 mm or less. More specifically, as shown in Fig. 4, the beam depth H of a reinforced concrete beam 200 is set in the range of 400 mm to 500 mm, and the beam reinforcement 100 shown in Fig. 3 is a beam reinforcement that forms this reinforced concrete beam 200. Therefore, the length of the lap portion between the rising reinforcement portion 12 and the hanging reinforcement portion 22 (the lap length is the length L of the rising reinforcement portion 12 and the hanging reinforcement portion 22) does not have the specified lap splice length (for example, a length of 40d when the nominal diameter of the hanging reinforcement portion 22 and the rising reinforcement portion 12 is d).

[0044] If a specified lap joint length is required at the lap point between the rising reinforcement section 12 and the hanging reinforcement section 22 for a reinforced concrete beam 200 with such a low beam depth, it may often occur that the specified lap joint length is not met.

[0045] Therefore, in the beam reinforcement 100, although the overlap portion of the rising reinforcement portion 12 and the hanging reinforcement portion 22 does not have a specified lap joint length, the height L of the beam reinforcement 100 is secured as the overlap length of the overlap portion, and the lower portion (for example, the lower end) of the hanging reinforcement portion 22 is arranged at the lower end position of the beam reinforcement 100 (to the side of the bottom reinforcement portion 11 and the lower end main reinforcement 70). This makes it unnecessary to use horizontal reinforcements to connect the hanging reinforcement portions 22 of the multiple second stirrups 20, and prevents the horizontal reinforcements from becoming the starting point of cracks, while allowing the lower portion of the hanging reinforcement portion 22 to be restrained by the wide lower rectangular portion 150.

[0046] As shown in Fig. 4, the reinforced concrete beam 200 has a lower rectangular portion 150 with a first width w1 and an upper rectangular portion 160 with a second width w2 narrower than the first width w1, and its cross section perpendicular to the longitudinal direction has an inverted T shape. As described above, the reinforced concrete beam has a small beam depth H of 500 mm or less.

[0047] The lower part of the hanging portion 22 of the second stirrup 20 is located inside the lower rectangular portion 150 having a first width w1, and the first cover t1 of the hanging portion 22 in the lower rectangular portion 150 is set larger than the second cover t2 of the hanging portion 22 and the rising portion 12 in the upper rectangular portion 160.

[0048] Specifically, the first fog t1 is set to about twice the second fog t2, and when the second fog t2 is 50 mm, the first fog t1 is set to about 100 mm to 120 mm.

[0049] In this way, the cross section perpendicular to the longitudinal direction of the reinforced concrete beam 200 is made in an inverted T shape, and the first cover t1 on the side of the hanging reinforcement portion 22 of the second stirrup 20 is made sufficiently large and larger than the second cover t2 of the hanging reinforcement portion 22 and the rising reinforcement portion 12 located above it.As a result, even if the hanging reinforcement portion 22 does not have hooks or horizontal reinforcements, when a tensile force acts on the second stirrup 20 and the hanging reinforcement portion 22 tries to open sideways, the sufficiently large restraining effect of the first cover t1 can prevent the hanging reinforcement portion 22 from opening sideways.

[0050] This ensures the integrity of the lower stirrup unit 50, the upper stirrup unit 60, the upper main reinforcement 30, and the lower main reinforcement 70 that constitute the beam reinforcement 100, even if the hanging reinforcement section 22 of the second stirrup 20 that constitutes the upper stirrup unit 60 does not have a hook and does not have a horizontal reinforcement connecting each hanging reinforcement section 22.

[0051] Furthermore, since the upper stirrup unit 60 does not have horizontal bars connecting the hanging bar portions 22 of each second stirrup 20, the horizontal bars are prevented from becoming the starting point of cracks, making it possible to form a reinforced concrete beam 200 that is less susceptible to cracks and has excellent deformation performance.

[0052] Next, another example of a reinforced concrete beam according to the embodiment will be described with reference to Fig. 5 and Fig. 6. Here, Fig. 5 is a diagram for explaining another example of a method for forming beam reinforcement to form a reinforced concrete beam according to the embodiment, and Fig. 6 is a perspective view of another example of a reinforced concrete beam according to the embodiment.

[0053] In the example shown in Fig. 5, the plurality of second stirrups 40 constituting the upper stirrup unit 60A have a top end portion 41 and first hanging end portions 42 and second hanging end portions 43 hanging downward from both ends of the top end portion 41, the first hanging end portion 42 has a first vertical portion 42a and a 90-degree hook 42b at the lower end of the first vertical portion 42a, and the second hanging end portion 43 has a second vertical portion 43 having a length L longer than the length L' of the first vertical portion 42a, and in this respect, the upper stirrup unit 60A is different from the upper stirrup unit 60A formed by the plurality of second stirrups 20 having a U-shape opening downward in that they have an approximately U-shape opening downward.

[0054] When each second stirrup 40 is placed over the first stirrup 10 in the X1 direction, the lower part of the second hanging reinforcement portion 43 is positioned to the side of the bottom reinforcement portion 11 of the first stirrup 10, which is the same as the beam reinforcement 100.

[0055] On the other hand, the first hanging reinforcement section 42 is placed on one of the upper end main reinforcements 30 by inserting a 90-degree hook 42b from below to the inside, and the corner section of the top end reinforcement section 41 and the first vertical section 42a is placed on the upper end main reinforcement 30.

[0056] 6 also eliminates the need for horizontal bars connecting multiple second stirrups, preventing the horizontal bars from becoming crack initiation points. Furthermore, the restraining effect of the 90-degree hooks 42b of the first hanging reinforcement portions 42 and the restraining effect of the lower rectangular portions 150 where the lower parts of the second hanging reinforcement portions 43 are located allows the formation of a high-strength reinforced concrete beam 200A with excellent deformation performance.

[0057] It should be noted that the present invention is not limited to the configurations shown here, and other embodiments may be possible in which other components are combined with the configurations described in the above embodiments. In this regard, the present invention can be modified within the scope of the present invention, and can be appropriately determined depending on the application form. [Explanation of symbols]

[0058] 10: First stirrup 11: Bottom reinforcement 12: Standing muscle 20: Second stirrup 21: Top muscle 22: Hanging muscle 30:Top main reinforcement 40: Second stirrup 41: Top muscle 42:First hanging muscle part 42a: 1st vertical section 42b: 90 degree hook 43:Second hanging muscle part (second vertical part) 50: Lower stirrup unit 60, 60A: Upper stirrup unit 70: Bottom main reinforcement 100: Beam reinforcement 150: Lower rectangular part 160: Upper rectangular part 200, 200A: Reinforced concrete beam

Claims

1. A reinforced concrete beam having beam reinforcement inside the concrete, The beam reinforcement is a lower stirrup unit in which first stirrups are arranged at a predetermined pitch, each having a U-shape that opens upward and having bottom reinforcing bars and rising reinforcing bars rising upward from the left and right ends of the bottom reinforcing bar, and each first stirrup is connected to the corresponding left and right rising reinforcing bars by full-strength welding of the upper end main reinforcing bars at the inside of the upper ends of the corresponding left and right rising reinforcing bars; an upper stirrup unit having a U-shape that opens downward, and having a top reinforcement portion and hanging reinforcement portions that hang down from the left and right ends of the top reinforcement portion and extend to the bottom reinforcement portion, and having no hooks at the ends of the hanging reinforcement portions, and each second stirrup is arranged at a predetermined pitch and is not integrated with another; The bottom reinforcement portion forming the first stirrup and the rising reinforcement portion have a lower end main reinforcement connected to the inside of the bent portion at the boundary thereof, When the upper stirrup unit is placed over the lower stirrup unit, the rising portion of the corresponding first stirrup and the hanging portion of the corresponding second stirrup overlap, and the hanging portion extends to the side of the lower end main reinforcement, The cross-sectional shape of the reinforced concrete beam perpendicular to the longitudinal direction is an inverted T-shape in which a lower rectangular portion having a first width and an upper rectangular portion having a second width narrower than the first width are connected, A reinforced concrete beam, characterized in that the bottom reinforcement portion, the lower end main reinforcement, and the lower parts of the hanging reinforcement portion are located in the lower rectangular portion.

2. A reinforced concrete beam having beam reinforcement inside the concrete, The beam reinforcement is a lower stirrup unit in which first stirrups are arranged at a predetermined pitch, each having a U-shape that opens upward and having bottom reinforcing bars and rising reinforcing bars rising upward from the left and right ends of the bottom reinforcing bar, and each first stirrup is connected to the corresponding left and right rising reinforcing bars by full-strength welding of the upper end main reinforcing bars at the inside of the upper ends of the corresponding left and right rising reinforcing bars; an upper stirrup unit having a generally U-shape that opens downward, and having a top end portion and first and second hanging end portions hanging downward from both ends of the top end portion, the first hanging end portion having a first vertical portion and a 90-degree hook at the lower end of the first vertical portion, the second hanging end portion having a second vertical portion that is longer than the first vertical portion and does not have a hook at its end, the second stirrups being arranged at a predetermined pitch and not integrated with each other; The bottom reinforcement portion forming the first stirrup and the rising reinforcement portion have a lower end main reinforcement connected to the inside of the bent portion at the boundary thereof, When the upper stirrup unit is placed over the lower stirrup unit, the rising portion of the corresponding first stirrup overlaps with the first vertical portion and the second vertical portion of the corresponding second stirrup, and the second vertical portion extends to the side of the lower end main reinforcement, The cross-sectional shape of the reinforced concrete beam perpendicular to the longitudinal direction is an inverted T-shape in which a lower rectangular portion having a first width and an upper rectangular portion having a second width narrower than the first width are connected, A reinforced concrete beam, characterized in that the bottom reinforcement portion, the lower end main reinforcement, and the lower part of the second vertical portion are located in the lower rectangular portion.

3. 3. A reinforced concrete beam according to claim 1, wherein the first cover of the hanging reinforcement portion in the lower rectangular portion is at least twice the second cover of the hanging reinforcement portion in the upper rectangular portion.

4. 3. A reinforced concrete beam according to claim 1 or 2, characterized in that the beam depth is 500 mm or less.

Images