JP2014122504A - Reinforcing fitting and reinforced concrete perforated beam comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reinforcing fitting which further suppresses a crack caused in a reinforced concrete perforated beam and which makes workability excellent by suppressing product weight.SOLUTION: A reinforcing fitting 1 includes: an outside reinforcement 2 which is formed in an annular shape; an inside reinforcement 3 which is formed in an annular shape and arranged inside the outside reinforcement 2; and an auxiliary reinforcement 4 which is formed in an annular shape, which is arranged further inside the inside reinforcement 3, and which is nearer to a through-hole (opening) 12 than the outside and inside reinforcements 2 and 3. The auxiliary reinforcement 4 is formed of a reinforcing bar larger in diameter than the inside reinforcement 3.

Description

  The present invention relates to a reinforcing metal fitting provided with an outer reinforcing bar and an inner reinforcing bar and arranged around the opening in a building having an opening, and a reinforced concrete perforated beam including the reinforcing metal fitting.

Reinforced concrete building beams may be provided with piping, wiring, or through-holes for personal use, and cracks that can be generated from the through-holes of such perforated beams, in particular, oblique shearing forces are applied. In order to prevent shear cracks at the time, reinforcing metal fittings as shown in Patent Documents 1 to 5 are conventionally provided around the through hole.
The term “reinforced concrete” described in the present specification includes steel reinforced concrete, and is used to include all structures in which concrete is reinforced with reinforcing bars.

Japanese Patent Publication No. 8-3236 JP 2003-20755 A JP 2005-180175 A JP 2005-320687 A JP 2007-162360 A

  By the way, in recent years, more and more earthquake resistance has been demanded for buildings, and the meaning of the earthquake resistance is not only from serious events such as damage to building structures, Although it does not lead to damage, the state before that, for example, the remarkable crack which arises in concrete is also included. That is, while maintaining the shear strength at a high level, further suppression of cracks generated in concrete due to an earthquake is required.

  Although the length of the crack generated in the through hole in the reinforced concrete perforated beam can be suppressed to a certain degree by using the reinforcing metal fittings described in Patent Documents 1 to 5 described above, while maintaining the high shear strength as described above. However, it was not always sufficient for the demand to further suppress cracks generated in concrete due to earthquakes.

  In recent years, reinforcing metal fittings that reinforce the periphery of the through hole are often formed of high-strength reinforcing bars. High-strength reinforcing bars have a high yield point, can provide high shear strength, and can reduce the diameter of the reinforcing bars, resulting in weight reduction and good workability. However, on the other hand, from the viewpoint of further limiting the cracks around the through-hole, the high-strength rebar has a small diameter, so the elongation for a given load increases. This is rather inferior in terms of crack control.

  In order to make up for such drawbacks, it is conceivable to use a plurality of reinforcing metal fittings.

  Accordingly, the present invention has been made in view of such a situation, and an object of the present invention is to further suppress cracks generated in a reinforced concrete perforated beam, and to suppress the product weight and to improve the workability, and this It is in providing a reinforced concrete perforated beam provided with.

  A first aspect of the present invention for solving the above-described problem includes an outer reinforcing bar formed in an annular shape, and an inner reinforcing bar formed in an annular shape and disposed inside the outer reinforcing bar. A reinforcing metal fitting arranged around the opening in a building having an opening, and comprising an auxiliary reinforcing bar formed in an annular shape and having a reinforcing bar portion positioned further inside the inner reinforcing bar. It is characterized by.

  According to this aspect, the reinforcing bracket disposed around the opening in the building having the opening includes the outer reinforcing bar formed in an annular shape and the inner reinforcing bar disposed inside thereof, and further includes the inner reinforcing bar. An auxiliary reinforcing bar having a reinforcing bar portion located inside is provided. Therefore, the amount of reinforcing bars (reinforcing bar cross-sectional area) around the opening can be increased, the extension of the reinforcing bar can be further suppressed, and cracks generated in the opening can be more effectively suppressed.

  Moreover, in addition to being able to suppress cracking at the time of the occurrence of an earthquake, it will also contribute to suppression of cracks around the opening caused by drying after construction. Furthermore, since it is not necessary to use a plurality of reinforcing metal fittings in order to suppress cracks generated in the opening, it is possible to avoid a significant increase in cost without deteriorating the workability.

  According to a second aspect of the present invention, in the first aspect, the auxiliary reinforcing bar is formed of a reinforcing bar having a diameter larger than that of the inner reinforcing bar.

  According to this aspect, since the auxiliary reinforcing bars are formed by reinforcing bars having a diameter larger than that of the inner reinforcing bars, the amount of reinforcing bars (rebar cross-sectional area) around the opening can be effectively increased. Elongation can be further suppressed, and cracks generated in the opening can be suppressed more effectively. The “large diameter” means that the cross-sectional area of the auxiliary reinforcing bar is larger than the inner reinforcing bar regardless of the cross-sectional shapes of the inner reinforcing bar and the auxiliary reinforcing bar.

  The third aspect of the present invention is characterized in that the outer reinforcing bar and the inner reinforcing bar are formed by reinforcing bars having higher strength than the auxiliary reinforcing bar.

  According to this aspect, since the outer reinforcing bar and the inner reinforcing bar are formed of a reinforcing bar having a strength higher than that of the auxiliary reinforcing bar, the above-described first reinforcing bar is obtained while obtaining a high shear strength as a whole reinforcing bracket. It is possible to obtain the operational effects obtained in the aspect, that is, the further suppression effect of cracks generated in the opening, good workability, and avoidance of cost increase.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the inner reinforcing bar has a substantially square shape having four sides orthogonal to a direction of a shearing force applied to the opening. It is characterized by.

  According to this aspect, the inner reinforcing bar has a substantially square shape having four sides orthogonal to the direction of the shearing force applied to the opening, and thus more reliably against the shearing force applied to the opening. Can be countered.

  According to a fifth aspect of the present invention, in the fourth aspect, the auxiliary reinforcing bar has a polygon having more corners than the inner reinforcing bar and a side perpendicular to the direction of the shear force, or It is characterized by a circular shape.

  According to this aspect, the auxiliary reinforcing bar has a polygonal shape having more corners than the inner reinforcing bar and a side perpendicular to the direction of the shear force, or a circular shape. The distance from the opening to the auxiliary reinforcing bar can be shortened, and cracks generated in the opening can be more effectively suppressed.

  A sixth aspect of the present invention is a reinforcing bracket arranged around the opening in a building having an opening, and has a plurality of reinforcing bars arranged so as to surround the through hole, and the plurality of reinforcing bars are The reinforcing bar is provided with a reinforcing bar close to the through hole and a reinforcing bar far from the through hole, and the reinforcing bar close to the through hole is larger in diameter than the reinforcing bar far from the through hole.

  According to this aspect, the reinforcing metal fitting arranged around the opening in the building having the opening has a plurality of reinforcing bars arranged so as to surround the through hole, and the plurality of reinforcing bars are arranged in the through hole. The rebar is composed of a close rebar and a rebar far from the through hole, and the rebar close to the through hole has a larger diameter than the rebar far from the through hole, so the amount of rebar around the opening (rebar cross-sectional area) is effective. Thus, the elongation of the reinforcing bars can be further suppressed, and cracks generated in the openings can be suppressed more effectively. The “large diameter” means that the cross-sectional area of the auxiliary reinforcing bar is larger than the inner reinforcing bar regardless of the cross-sectional shapes of the inner reinforcing bar and the auxiliary reinforcing bar.

  Moreover, in addition to being able to suppress cracking at the time of the occurrence of an earthquake, it will also contribute to suppression of cracks around the opening caused by drying after construction. Furthermore, since it is not necessary to use a plurality of reinforcing metal fittings in order to suppress cracks generated in the opening, it is possible to avoid a significant increase in cost without deteriorating the workability.

  A seventh aspect of the present invention is a reinforced concrete perforated beam including a reinforcing metal fitting according to any one of the first to sixth aspects. According to this aspect, in the reinforced concrete perforated beam, it is possible to obtain the same effect as any of the first to sixth aspects described above.

The front view of the beam using the reinforcement metal fitting which concerns on 1st Embodiment of this invention. Sectional drawing of the beam using the reinforcement metal fitting which concerns on 1st Embodiment of this invention. The figure which shows the relationship between the reinforcement metal fitting and stirrup which concern on 1st Embodiment of this invention. The top view of the reinforcement metal fitting which concerns on 1st Embodiment of this invention. The top view of the reinforcement metal fitting which concerns on 2nd Embodiment of this invention. The top view of the reinforcement metal fitting which concerns on 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure in each figure, and the overlapping description will be avoided.
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a front view of a beam using a reinforcing metal fitting 1 according to the first embodiment of the present invention, FIG. 2 is a cross-sectional view thereof, and FIG. 3 is a diagram showing the relationship between the reinforcing metal fitting 1 and a stirrup to which the reinforcing metal fitting is attached. 4 is a plan view of the reinforcing metal fitting 1. FIG. 2 mainly shows the relationship between the main bar 15, the stirrup bar 17, and the reinforcing metal fitting 1, and hatching is omitted to avoid complication of the drawing.

  1 and 2 show concrete beam / floor structures. In this concrete beam / floor structure, a reinforced concrete perforated beam 11 and a floor 10 are integrally formed to have a substantially T-shaped cross section as shown in FIG. In the beam 11, reference numeral 12 indicates a through-hole penetrating in the thickness direction of the reinforced concrete perforated beam 11 (the front and back direction in FIG. 1 and the left-right direction in FIG. 2). An opening is formed. The through hole 12 is formed using a sleeve 13 shown in FIG.

  A reinforcing metal fitting 1 according to the present invention includes an outer reinforcing bar 2 formed in an annular shape, an inner reinforcing bar 3 disposed in the outer reinforcing bar 2 and also formed in an annular shape, and also formed in an annular shape. The reinforcing reinforcement 4 is provided with an auxiliary reinforcing bar 4 having a reinforcing bar portion located further inside the reinforcing bar 3, and is a reinforcing metal fitting disposed around the through hole (opening) 12. The configuration of the reinforcing metal fitting 1 will be described in detail later.

  2 and 3, reference numeral 15 indicates a main bar arranged in the longitudinal direction of the beam 11 (the front and back direction in FIG. 2 and the left and right direction in FIG. 3). As shown in the figure, the main bars 15 are arranged with an appropriate interval in the width direction of the beam 11 (left and right direction in FIG. 2), and further in the height direction of the beam 11 (up and down direction in FIGS. 2 and 3). The bars are arranged with an interval of a part of them, and some of them are arranged in the area of the floor 10.

  Reference numerals 16 and 17 denote shear reinforcement bars (also referred to as hoop bars or ribbed bars) that are engaged with the main bars 15. As shown in FIG. 3, a large number of the shear reinforcement bars 16 and 17 are arranged at an appropriate interval in the longitudinal direction of the beam 11 (left and right direction in FIG. 3). Among these, the shear reinforcing bar 17 is a staggered hole located near the through hole 12, and the shear reinforcing bar 16 is the other staggered bar. In FIG. 3, reference numeral 18 denotes an opening vertical reinforcing bar disposed above and below the through hole 12.

  With respect to the bar arrangement as described above, the reinforcing metal fitting 1 is arranged at both end openings of the through hole 12 as shown in FIG. Specifically, for example, it is bound and fixed to the main muscle 15. The concrete is then cast on it, and a reinforced concrete perforated beam / floor structure is constructed.

  Next, the configuration of the reinforcing metal fitting 1 will be described in detail with reference to FIG. In the reinforcing metal fitting 1, each reinforcing bar is formed by bending a reinforcing bar, and in this embodiment, the outer reinforcing bar 2 and the inner reinforcing bar 3 are formed individually and then the corners (outer side) of the inner reinforcing bar 3 are formed. It is fixed by welding at a contact portion with the reinforcing bar 2). However, the present invention is not limited to this, and the outer reinforcing bar 2 and the inner reinforcing bar 3 may be formed by a single reinforcing bar in the manner of one-stroke writing.

  One end and the other end of the outer reinforcing bar 2 are bent toward the center, and an end cap 5 is attached to the bent end of the outer reinforcing bar 2 to receive (support) the sleeve 13. It is formed to function as. Note that the end cap 5 and the bent portion (of the outer reinforcing bar 2) for attaching the end cap 5 may be omitted.

  The auxiliary reinforcing bar 4 disposed further inside the inner reinforcing bar 3 is formed by bending a reinforcing bar, and in this embodiment is fixed to the inner reinforcing bar 3 by welding. The auxiliary reinforcing bar 4 may be fixed to the inner reinforcing bar 3 in advance in a factory (other than the construction site of the reinforced concrete beam / floor structure) or at the construction site of the reinforced concrete beam / floor structure. Also good.

  If it is the former, the reinforcing bracket 1 is completed at the factory and is carried to the construction site as a finished product, so the process at the construction site (fixing of the auxiliary reinforcing bar 4 to the inner reinforcing bar 3) becomes unnecessary, and at the construction site. The construction time can be shortened. Moreover, if it is the latter, since the metal fittings which consist of the outer reinforcement bar 2 and the inner reinforcement bar 3, and the auxiliary reinforcement bar 4 can be handled separately in a construction site, the workability in a construction site improves by weight reduction. To do.

  It is not always essential to connect and fix the auxiliary reinforcing bars 4 to the inner reinforcing bars 3. For example, the auxiliary reinforcing bar 4 may not be connected and fixed to the inner reinforcing bar 3 but only fixed to the shear reinforcing bar 17 shown in FIG.

  Hereinafter, the outer reinforcing bar 2, the inner reinforcing bar 3, and the auxiliary reinforcing bar 4 will be described in more detail with reference to FIG. The outer reinforcing bar 2 has a substantially octagonal shape with eight sides (2a to 2h), and is formed such that two adjacent sides form an angle of about 45 °. When the reinforcing metal fitting 1 is attached to the beam 11, these four sides of the sides 2 a, 2 c, 2 e and 2 g form an angle of about 45 ° with respect to the longitudinal direction of the beam 11. The two sides 2d and 2h are substantially parallel to the longitudinal direction of the beam 11, and the two sides 2b and 2f are substantially parallel to the height direction of the beam 11.

  The inner reinforcing bar 3 has a substantially square shape having four sides (3a to 3d), and is formed such that two adjacent sides form an angle of about 90 °. When the reinforcing metal fitting 1 is attached to the beam 11, the sides 3 a to 3 d form an angle of about 45 ° with respect to the longitudinal direction of the beam 11.

  The auxiliary reinforcing bars 4 have a substantially octagonal shape with eight sides (4a to 4h), and are formed so that two adjacent sides form an angle of about 45 °. When the reinforcing metal fitting 1 is attached to the beam 11, these four sides of the sides 4 a, 4 c, 4 e, and 4 g form an angle of about 45 ° with respect to the longitudinal direction of the beam 11. The two sides 4d and 4h are substantially parallel to the longitudinal direction of the beam 11, and the two sides 4b and 4f are substantially parallel to the height direction of the beam 11.

  In this embodiment, among the reinforcing bar portions constituting the auxiliary reinforcing bars 4, the sides 4 a, 4 c, 4 e, and 4 g forming an angle of 45 ° are respectively the same 45 ° angle of the reinforcing bar parts constituting the inner reinforcing bar 3. Are overlapped with the sides 3a, 3b, 3c, and 3d, and are fixed by welding.

  Here, the auxiliary reinforcing bars 4 are formed by reinforcing bars having a diameter larger than that of the inner reinforcing bars 3. As an example, the outer reinforcing bar 2 and the inner reinforcing bar 3 are formed of high-strength deformed reinforcing bars having a nominal name 16 (nominal diameter 15.9 mm, nominal cross-sectional area 1.986 cm 2), and the auxiliary reinforcing bars 4 are named 19 ( It is made of ordinary strength deformed reinforcing bars with a nominal diameter of 19.1 mm and a nominal cross-sectional area of 2.865 cm ^ 2. In the above embodiment, the high strength reinforcing bar has a yield point of 785 N / mm ^ 2, and the normal strength reinforcing bar has a yield point of 345 N / mm ^ 2. In addition, the standard of normal strength rebar is based on JIS G 3112.

  And all sides 4a-4h which constitute auxiliary reinforcing bar 4 are located in the inner side of inner side reinforcing bar 3 (protruded inward from inner side reinforcing bar 3), and constituted the reinforcing bar part near penetration hole 12 It has become. In addition to the form in which all the sides 4 a to 4 h constituting the auxiliary reinforcing bar 4 are positioned further inside the inner reinforcing bar 3, some of the sides constituting the auxiliary reinforcing bar 4 further extend from the inner reinforcing bar 3. It is good also as a form located inside.

  In the reinforcing metal fitting 1 having the above configuration, the reinforcing bars intersecting at an angle of about 45 ° with respect to the length direction of the beam 11, specifically, the sides 2 a, 2 c, 2 e, 2 g constituting the outer reinforcing bars 2, When the tensile force or the compressive force is applied in the length direction of the beam 11 of the sides 3a to 3d constituting the inner reinforcing bar 3 and the sides 4a, 4c, 4e, and 4g constituting the auxiliary reinforcing bar 4 Is perpendicular to the shearing force generated in the beam 11 (acting in a direction that forms an angle of 45 ° with respect to the length direction of the beam 11). Can be prevented from spreading).

  In addition, each piece (each side of the outer reinforcing bar 2, the inner reinforcing bar 3, and the auxiliary reinforcing bar 4) that suppresses the spread of the shear crack C does not exist independently, but each reinforcing bar formed in an annular shape. That is, since each piece is joined, the joint effect can more effectively counter the shearing force.

  Further, the distance from the through hole 12 to the inner reinforcing bar 3 can be shortened by the auxiliary reinforcing bar 4. In particular, the auxiliary reinforcing bars 4 (substantially octagonal in the present embodiment) are formed in a shape having more corners than the inner reinforcing bars 3 (substantially quadrilateral in the present embodiment), so that the through holes 12 to the inner reinforcing bars 3 are formed. Can be effectively shortened. Thereby, for example, it is possible to effectively suppress the spread of cracks after construction (cracks as indicated by symbol D in FIG. 4).

  In the reinforcing metal fitting 1 according to the present invention, the auxiliary reinforcing bars 4 are formed by reinforcing bars having a diameter larger than that of the outer reinforcing bars 2 and the inner reinforcing bars 3. Therefore, the amount of reinforcing bars (cross-sectional area) around the opening (through hole 12) can be effectively increased, and the extension of the reinforcing bars to the shearing force can be further suppressed. (Cracking shown) can be suppressed.

  That is, from the viewpoint of improving the shear strength of the reinforced concrete perforated beam 11, it is necessary to increase the yield point of the reinforcing bar, but on the other hand, when receiving damage that does not reach the yield point (for example, when a middle earthquake occurs) From the viewpoint of suppressing the crack width, it is necessary to suppress the amount of elongation of the reinforcing bar, and more specifically, the cross-sectional area of the reinforcing bar is important. This is because the Young's modulus governing the elongation of the reinforcing bar is constant regardless of the yield strength of the reinforcing bar, and the elongation is governed by the cross-sectional area.

  Therefore, in the present invention, the auxiliary reinforcing bar 4 disposed further inside the inner side reinforcing bar 3 has a diameter larger than that of the inner side reinforcing bar 3. As a result, the cross-sectional area of the reinforcing bars around the through-hole 12 can be effectively increased as described above, and the extension of the reinforcing bars to the shearing force can be further suppressed, and cracks can be more effectively suppressed. Become. The “large diameter” means that the cross-sectional area of the auxiliary reinforcing bar 4 is larger than that of the inner reinforcing bar 3 regardless of the cross-sectional shapes of the inner reinforcing bar 3 and the auxiliary reinforcing bar 4.

  Moreover, since the outer reinforcing bar 2 and the inner reinforcing bar 3 are high-strength reinforcing bars, cracks at the time of the occurrence of an earthquake can be effectively suppressed as described above while obtaining high shear strength as the entire reinforcing metal fitting 1. In addition, since it is not necessary to use a plurality of reinforcing metal fittings in order to suppress cracks generated around the through-hole 12, both good workability and prevention of cost increase can be achieved. However, even if normal strength reinforcing bars are used for the outer reinforcing bars 2 and the inner reinforcing bars 3, the above-described effects of the auxiliary reinforcing bars 4 composed of reinforcing bars having a diameter larger than these can be obtained.

  Each embodiment described above is an example, and it goes without saying that various modifications are possible. For example, although the auxiliary reinforcing bars 4 having a larger diameter than the outer reinforcing bars 2 and the inner reinforcing bars 3 are used in the above-described embodiment, the auxiliary reinforcing bars 4 are not limited thereto, and those having the same diameter or a smaller diameter may be used. In other words, it is only necessary that at least one side of the sides constituting the auxiliary reinforcing bar 4 is located further inside than the inner side reinforcing bar 3 (if it protrudes). Further, it is not always necessary to overlap the side that constitutes the auxiliary reinforcing bar 4 and the side that constitutes the inner side reinforcing bar 3, and the auxiliary reinforcing bar 4 </ b> A is completely connected to the inner side reinforcing bar 3 like the reinforcing metal fitting 1 </ b> A shown in FIG. 5. It may be placed inside.

  As another form, the auxiliary reinforcing bars 4 can be formed in a circular shape instead of a polygonal shape. The reinforcing metal fitting 1B shown in FIG. 5 is a reinforcing metal fitting provided with a circular auxiliary reinforcing bar 4B. Also in such a reinforcing metal fitting 1 ', the same effect as that of the reinforcing metal fitting 1 already described can be obtained.

  In FIG. 2, the auxiliary reinforcing bars 4 are disposed outside (opening outside) the outer reinforcing bars 2 and the inner reinforcing bars 3, but are not limited thereto, and are disposed inside the outer reinforcing bars 2 and the inner reinforcing bars 3. May be.

  Further, the number of reinforcing bars constituting the reinforcing metal fitting 1 is not limited to three as in the present embodiment, and may be constituted by a plurality of reinforcing bars. That is, regardless of the number of reinforcing bars constituting the reinforcing metal fitting 1, the reinforcing bar close to the through hole 12 is larger than the reinforcing bar far from the through hole 12 in the configuration including the reinforcing bar close to the through hole 12 and the reinforcing bar far from the through hole 12. If it is a diameter, it becomes possible to obtain the above-mentioned operational effects of the present invention.

1, 1A, 1B, 1C Reinforcing bracket 2 Outer reinforcing bar 3 Inner reinforcing bar 4, 4A, 4B, 4C Auxiliary reinforcing bar 5 End cap (sleeve holder)
DESCRIPTION OF SYMBOLS 10 Floor slab 11 Reinforced concrete perforated beam 12 Through-hole 13 Sleeve 15 Main reinforcement 16 General part stirrup 17 Perforation stirrup 18 Opening vertical reinforcement

Claims (7)

An outer reinforcing bar formed in an annular shape;
A reinforcing metal fitting arranged around the opening in a building having an opening, the inner reinforcing bar arranged inside the outer reinforcing bar formed in an annular shape,
An auxiliary reinforcing bar formed in an annular shape and having a reinforcing bar portion located further inside the inner reinforcing bar;
Reinforcing metal fittings characterized by that. The reinforcing metal fitting according to claim 1, wherein the auxiliary reinforcing bar is formed of a reinforcing bar having a diameter larger than that of the inner reinforcing bar.
Reinforcing metal fittings characterized by that. The reinforcing metal fitting according to claim 1 or 2, wherein the outer reinforcing bar and the inner reinforcing bar are formed of a reinforcing bar having a strength higher than that of the auxiliary reinforcing bar.
Reinforcing metal fittings characterized by that. The reinforcing metal fitting according to any one of claims 1 to 3, wherein the inner reinforcing bar has a substantially square shape having four sides orthogonal to a direction of a shearing force applied to the opening.
Reinforcing metal fittings characterized by that. 5. The reinforcing metal fitting according to claim 4, wherein the auxiliary reinforcing bar has a polygonal shape or a circular shape having more corners than the inner reinforcing bar and a side perpendicular to the direction of the shearing force. Yes,
Reinforcing metal fittings characterized by that. Reinforcing metal fittings arranged around the opening in a building having an opening,
Having a plurality of reinforcing bars arranged to surround the through-hole,
The plurality of reinforcing bars include a reinforcing bar close to the through hole and a reinforcing bar far from the through hole,
The rebar close to the through hole is larger in diameter than the rebar far from the through hole.
Reinforcing metal fittings characterized by that.   A reinforced concrete perforated beam comprising the reinforcing metal fitting according to any one of claims 1 to 6.

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