Patent Publication Number: US-2005138877-A1

Title: Plane lattice hollow concrete slab and cross arm brace

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a plane lattice hollow concrete slab having a high workability and a high sound insulating property, and a cross arm brace used in the concrete slab.  
      In order to make a building be high-rise or to secure a wide room space, a construction method is realized which increases a strength by increasing a thickness of ferroconcrete slab. In order to accomplish a weight saving and to improve a sound insulating property, another construction method is realized which makes the concrete slab be hollow by burying a buried object in the concrete slab. A hollow pipe, a box shaped artifact, or a water resistant corrugated cardboard is used as such a buried object. The hollow pipe may be, for example, a winding pipe. The box shaped artifact may be made of a bent steel deck or bent keystone plate. In addition, proposal is made in Japanese Patent Publication Tokko Syo 57-47007 or Japanese Patent Publication Tokko Syo 58-20768 about a construction method using a synthetic resin foam as the buried object and using a mold form which is fixedly integrated to a thin PC base plate.  
      Although it is possible to accomplish the weight saving in each of the above-mentioned conventional construction methods, the concrete slab is a unidirectional slab in which a hollow portion continues in a single direction, in each of the conventional construction methods. Inasmuch as the unidirectional concrete slab structurally transmits a load in the single direction, there are architectonic constraints in case of the slab which carries out a support on four sides. In order to dissolve the above-mentioned problem, proposal is made in Japanese Patent Publication Tokko Syo 63-49025 about a bi-directional slab. However, it is necessary for the bi-directional slab using the hollow pipe to take a lot of trouble with design, on carrying out arrangement of the hollow pipe at each of slabs or articles. Furthermore, material management becomes complicate inasmuch as it is necessary to provide various sizes of hollow pipes. In addition, it is necessary to take a lot of trouble with construction.  
      In order to drastically improve the conventional hollow slab construction method, proposal is made in Japanese Unexamined Patent Publication Tokkai Hei 9-250196 about a construction method in which concrete runs in the mold form after a plurality of light weight bodies are located in small spaces compartmentalized on grids by top reinforcements and bottom reinforcements which are positioned at a lattice shape in the mold form. In the bi-directional slab construction method, the light weight body such as plastic foam, which has a die shape, a column shape, or a Japanese lantern shape, is used and is buried in each of the small spaces which are regularly formed at the lattice shape of the slab, in order to form the bi-directional slab having a cross section that beams of I type are met to each other in two directions perpendicular to each other. By the above-mentioned structure, it is easy to carry out the material management. On the execution of construction, the light weight body is only supported in the above-mentioned small space by an auxiliary reinforcing bar. As a result, it is possible to briefly form the bi-directional slab having high accuracy.  
      However, the bi-directional slab described in the above-mentioned Publication has following problems.  
      On forming a slab bone structure A shown in  FIG. 13 , an auxiliary reinforcing bar  24   a  is positioned in a middle of a lower reinforcing bar  22   a  and an auxiliary reinforcing bar  24   b  is positioned in a middle of a lower reinforcing bar  22   b , on a lower mold form  21 . After upper reinforcing bars  23   a  and  23   b  are positioned and a light weight body  25  is positioned, it is necessary to position an auxiliary reinforcing bar  24   c  between the upper reinforcing bar  23   a  and the upper reinforcing bar  23   b . In order to prevent the light weight body  25  from lifting on casting concrete, it is necessary to fix the bottom portion of the light weight body  25  by the auxiliary reinforcing bars  24   a  and  24   b  and to fix the top portion of the light weight body  25  by the auxiliary reinforcing bar  24   c . The auxiliary reinforcing bars hardly contribute to strength improvement of the slab. In addition, orientations occur towards up and down and right and left in the light weight body inasmuch as the light weight body has grooves each of which receives the auxiliary reinforcing bar. As a result, it is necessary to accurately position the light weight body with meeting the orientations, on the execution of construction. Accordingly, expenses are piling up and it is necessary to take a lot of trouble with setting of the light weight body. Cost increases on the execution of construction.  
     SUMMARY OF THE INVENTION  
      In order to dissolve the problems of the conventional bi-directional slab, it is an object of the present invention to provide a plane lattice hollow concrete slab having a high workability and a high sound insulating property, and a cross arm brace used in the concrete slab.  
      According to the present invention, there is provided a plane lattice hollow concrete slab comprising a light weight body buried in a small space which is partitioned on a grid by an upper reinforcing bar and a lower reinforcing bar positioned on a grid in a slab. The light weight body is a solid-core or a hollow light weight ball body. The light weight body has a diameter which passes through a top surface of the small space and which does not pass through a side surface of the small space. The light weight body is fixed to a predetermined position by a cross arm brace which is positioned on the upper reinforcing bar.  
      In the plane lattice hollow concrete slab of the present invention, a volume ratio of said small space to said light weight ball body may be selected from 10% to 50%.  
      According to the present invention, there is provided a cross arm brace for a plane lattice hollow concrete slab. The cross brace comprises at least two auxiliary reinforcing bars positioned in parallel between upper reinforcing bars adjacent to each other, and a plurality of units each of which is fixed downwardly on the auxiliary reinforcing bar. Each of the units is inserted into a small space formed by upper reinforcing bars which are positioned on a grid. A light weight ball body is fixed to a predetermined position of the small space.  
      In the cross arm brace of the present invention, each of the units is an endless frame reinforcing bar which is bent to a saddle shape. Preferably, each of the units has a leg portion which is bent to an outer side. In addition, each of the units comprises holding reinforcing bars which are bent so as to form a valley. The holding reinforcing bars are positioned one after the other with inclination. Both ends are not connected to each other in each of the holding reinforcing bars. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a plane view for illustrating a slab bone structure of concrete slab according to an embodiment of the present invention;  
       FIG. 2  shows a vertical sectional view along A-A′ line of  FIG. 1 ;  
       FIG. 3  shows a vertical sectional view along B-B′ line of  FIG. 1 ;  
       FIG. 4  shows a prospective view in a condition of cutting off the concrete of  FIG. 1 ;  
       FIG. 5  shows a prospective view for illustrating a cross arm brace according to an embodiment of the present invention;  
       FIG. 6  shows a plane view of the cross arm brace;  
       FIG. 7  shows a front view of the cross arm brace;  
       FIG. 8  shows a plane view of a unit for forming the cross arm brace;  
       FIG. 9  shows a vertical sectional view along A-A′ line of  FIG. 8 ;  
       FIG. 10  shows a vertical sectional view along B-B′ line of  FIG. 8 ;  
       FIG. 11  shows a prospective view for illustrating a cross arm brace according to another embodiment of the present invention;  
       FIG. 12  shows a prospective view for illustrating a cross arm brace according to further another embodiment of the present invention; and  
       FIG. 13  shows a view for illustrating a bone structure of a conventional plane lattice hollow concrete slab. 
    
    
     PREFERRED EMBODIMENT OF THE INVENTION  
      Description will be made as regards a plane lattice hollow concrete slab (which will be merely called a concrete slab hereinafter) according to an embodiment of the present invention. The present invention is not limited to the feature which will be described hereinafter. It is possible to replace each element and to carry out change of design within a range in which the object of the present invention is accomplished.  
       FIG. 1  shows a plane view for illustrating a slab bone structure of the concrete slab.  FIG. 2  shows a vertical sectional view along A-A′ line of  FIG. 1 .  FIG. 3  shows a vertical sectional view along B-B′ line of  FIG. 1 .  FIG. 4  shows a prospective view in a condition of cutting off the concrete of  FIG. 1 .  
      The slab bone structure shown in a reference symbol S comprises lower reinforcing bars  2   a  and  2   b  and upper reinforcing bars  3   a  and  3   b . The lower reinforcing bar  2   b  is positioned perpendicular to the lower reinforcing bars  2   a  which are positioned parallel to each other, on a lower mold form  1  of the slab. Similarly, the upper reinforcing bars  3   a  and  3   b  are positioned perpendicular to the lower reinforcing bars  2   a . As a result, a plurality of small spaces  4 , which are partitioned on grids, are formed in a lattice shape. Light weight ball bodies  5  are positioned in the small spaces  4 , respectively. The cross arm brace  6  is positioned on the upper reinforcing bar  3   b , in order to prevent each of light weight ball bodies  5  from movement. The lower reinforcing bar  2   b  and the upper reinforcing bar  3   b  is fixed by a width stop reinforcing bar  7 .  
      A mold form, which is made of wood, plastic or the like, is used as the lower mold form  1 . Instead of the mold form  1 , a deck construction method using a deck plate may be employed. Alternatively, a half PC construction method or a full PC construction method may be employed which uses a precast concrete.  
      It is desired that the interval of main reinforcing bar varies in accordance with a designed thickness of the concrete slab. The interval is indicative of an interval between one lower reinforcing bar  2   a  and an adjacent lower reinforcing bar  2   a  and between one lower reinforcing bar  2   a  and an adjacent lower reinforcing bar  2   a , in case of lower reinforcing bars. When the size of the light weight ball body  5  varies on the basis of the slab thickness, it is advantageous to improve the light weight and the sound insulating property with maintaining the slab rigidity. In addition, the interval between the lower reinforcing bar  2   a  and the upper reinforcing bar  3   a  may be determined on the basis of the slab thickness and the concrete cover thickness.  
      Although the width stop reinforcing bar  7  is not limited which is capable of fixing the upper reinforcing bar and the lower reinforcing bar, it is desired that the width stop reinforcing bar  7  is made of a reinforcing bar having about 10 mmφ-15 mmφ and cut to a predetermined length. One end of the width stop reinforcing bar  7  is bent to an acute angle and another end of the width stop reinforcing bar  7  is bent to about right angle. Alternatively, the width stop reinforcing bar  7  is used which a reinforcing bar cut to a predetermined length. The width stop reinforcing bar  7  may be fixed to the upper reinforcing bar and the lower reinforcing bar by using a fixing means such as a welding, adhesive bonding, branch tying, or the like.  
      The light weight ball body  5  used in the concrete slab according to the present invention has a diameter which is capable of passing through a top surface of the small space  4  and which is not capable of passing through a side surface of the small space  5 . In case where the diameter (φ) of the light weight ball body  5  is not greater than that of the side surface of the small space  4 , the light weight ball body  5  may stick out from one small space  5  to another small space  5  or may move from one small space  5  to another small space  5 . In addition, it is impossible to position the light weight ball body  5  in the small space  4  in case where the diameter p can not pass through the top surface of the small space  4 . As described above, one light weight ball body  5  enters in one small space  4  by defining the size of the light weight ball body in relation to the small space  4 .  
      When the light weight ball body  5  has the above-mentioned conditions, it is sufficient to provide six kinds of light weight ball bodies whose diameters is equal to S(φ125 mm), M(φ150 mm), L(φ175 mm), 2L(φ200 mm), 3L(φ225 mm), and 4l(φ250 mm), respectively. These light weight ball bodies can meet the slab thickness from 225 mm to 350 mm. Using the light weight ball body having an optional diameter, it is possible to meet an optional slab thickness.  
      It is desired that the shape of the light weight ball body has a spherical shape as far as possible. Although it is possible for the shape of the light weight ball body to be somewhat of irregular shape, it is necessary to align the light weight ball body in direction on the execution of construction, inasmuch as an ellipsoid shape or an ovoid shape such as a rugby ball has an orientation. When concavity and convexity or a shallow groove is formed on the surface of the light weight ball body, the light weight ball body makes friends with the concrete. The material of the light weight ball body is not limited in case where the material is light and can be easily worked. For example, it is possible to use a hollow body such as plastic foam or a plastic hollow body. More particularly, it is preferable to use a solid-core body of plastic foam such as polystyrene foam or polyethylene foam which has rigidity.  
      According to the present invention, it is possible to correctly position one light weight ball body  5  in one small space  4  when the light weight ball body only drops in the small space  4 , inasmuch as the light weight ball body has no orientation. On the other hand, efficiency greatly reduces on the execution of construction inasmuch as it is necessary to align each of the light weight bodies in direction, when using the conventional light weight body having the orientation.  
      In the present invention, it is desired that a ratio (volume ratio) of the light weight ball body to the small space is about 10% to 50%. In case where the volume ratio is less than 10%, it is difficult to make the concrete slab be light and it is difficult to improve the sound insulating property. In case where the volume ratio is greater than 50%, the rigidity of the concrete slab reduces. From a balance of the rigidity and lightness of the concrete slab, it is desired for the volume ratio to be from 15% to 35%. Furthermore, it is preferable for the volume ratio to be from 18% to 32%. Although Table 1 shows desired examples of slab thickness, sectional gap (gap between the lower reinforcing bar  2   a  and upper reinforcing bar  3   a ), void diameter, and volume ratio, the present invention is not limited to Table 1.  
                                           TABLE 1                          slab thickness   mm   225   250   275   300   325   350       cross-sectional gap   mm   115   140   165   190   215   240       void diameter Φ   mm   125   150   175   200   225   250       void volume   cm 3     1023   1767   2806   4189   5964   8181       volume ratio   %   20.2   23.1   25.5   27.6   29.4   30.9       the number of   pieces   4444   3265   2500   1975   1600   1322       small spaces                  
 
      After the light weight ball bodies  5  are positioned in a plurality of small spaces  4 , respectively, the cross arm brace  6  is mounted on the upper reinforcing bar  3   b  and is bonded to the upper reinforcing bar  3   a . In case where the light weight ball body  5  is only positioned in the small space  5 , the light weight body  5  floats from the small space  5  on casting a freshly mixed concrete. As a result, the light weight ball bodies  5  may escape from the small spaces to gather on the surface of the slab. Each of the light weight ball bodies  5  may be shifted from a predetermined position. In order to dissolve the above-mentioned problem, each of the light weight ball bodies  5  is fixed by the cross arm brace  6  according to the present invention. It is possible to use the cross arm brace  6  as a scaffold for piping work, wiring work, or the like. Furthermore, it is possible to prevent the light weight ball body from damage by using cross arm brace.  
      Next, description will proceed to an example of the cross arm brace for concrete slab according to the present invention, with reference to drawings.  FIG. 5 ,  FIG. 6 , and  FIG. 7  show a prospective view, a plane view, and a front view each of which shows the cross arm brace according to an embodiment of the present invention.  FIG. 9  shows a plane view for illustrating an unit for forming the cross arm brace.  FIG. 9  shows a vertical sectional view along A-A′ line of  FIG. 8 .  FIG. 10  shows a vertical sectional view along B-B′ line of  FIG. 8 .  
      The cross arm brace  11  comprises two auxiliary reinforcing bars  12  and  12 ′ and a plurality of units  13 ,  13 ′,  13 ″,  13 ′″,  13 ″″, . . . The unit  13  shown in  FIG. 5  has endless box shape in  FIG. 8 . The unit  13  shown in  FIG. 5  has a mount shape such as Mt. Fuji in  FIG. 9 . The unit  13  shown in  FIG. 5  has a box shape having no top portion, in  FIG. 10 . The unit  13  is fixed to the auxiliary reinforcing bars  12  and  12 ′ with straddling to a saddle shape. The unit  13  can be inserted into the small space illustrated in  FIG. 1 . The light weight ball body  14  is held in a space formed by the unit  13  which is for fixing the light weight ball body  14  with no movement. Although it is sufficient to provide two auxiliary reinforcing bars as shown in the drawings, at least three auxiliary reinforcing bars may be provided. In case of using one auxiliary reinforcing bar, the auxiliary reinforcing bar becomes a rotation axis and the cross arm brace rotates around the rotation axis. Therefore, it is necessary to fix the auxiliary reinforcing bar to the upper reinforcing bar by means of welding or the like. Although the auxiliary reinforcing bar is optional in thickness and length, it is easy to carry out the design and the execution of construction inasmuch as it is easy to deal with the auxiliary reinforcing bar, when a reinforcing bar having a diameter of 6 mmφ and a length of about 1.9 m may be used as the auxiliary reinforcing bar.  
      A reinforcing bar is bent to a rectangular shape whose ends are welded to each other, in order to make a rectangular frame bar. The rectangular frame bar is bent to a predetermined shape to be formed to the unit  13 . The unit  13  is mounted on two auxiliary reinforcing bars  12  and  12 ′ so as to direct the bent side of the unit  13  to a lower direction. By welding cross portions between the unit  13  and the auxiliary reinforcing bars  12  and  12 ′, the cross arm brace  11  is manufactured. Although the example is illustrated in which a leg portion  15  of the unit  13  is bent to an outer side, in the above-mentioned embodiment, a cross arm brace  11   a  is used whose unit  13   a  has a leg portion  15   a  which is not bent, as shown in  FIG. 11 . When the cross arm brace  11  has the leg portion  15  which is bent to the outer side, it easy to insert the cross arm brace  11  into the small space. In addition, it is possible for the cross arm brace to make friends with the light weight ball body. Furthermore, it is easy to pile the cross arm braces on storage and transportation.  
      Description will be made as regards another example of the cross arm brace with reference to drawings.  FIG. 12  shows a prospective view for illustrating another example of the cross arm brace. The illustrated cross arm brace  16  a fixed unit  18  instead of the unit  13  of the cross arm brace  11  that is illustrated in  FIG. 5 . The unit  18  is composed of a holding reinforcing bar  19  which is bent to a valley shape. The unit  18  is positioned to auxiliary reinforcing bars  17  and  17 ′ one after the other with inclination. Incidentally, the unit  18  may have a leg portion which is not bent, although the unit  18  has a leg portion  20  which is bent, in the above-mentioned embodiment.  
      The cross arm brace for the concrete slab according to the present invention is not limited to each of the above-mentioned embodiments and it is possible to carry out design variations in the cross arm brace. Incidentally, the light weight ball body moves on the basis of violent flow on casting the concrete when using a mesh shaped reinforcing bar, although the mesh shaped reinforcing bar such as a wire mesh, a metal lath, or the like is used as the cross arm brace. It is difficult for the mesh shaped reinforcing bar does to have a function of the cross arm brace.  
      In a preferred embodiment of the present invention, the small spaces  5  increase in number and proposal is made about concreter slab of a small room type that positions smaller light weight ball bodies  5  in small rooms, respectively. The concreter slab of small room type has a high sound insulating property in comparison to the conventional plane lattice hollow concrete slab (Japanese registered Utility Model Publication No. 3082676). In case of increasing the small rooms in number, the interval between the main reinforcing bars of length and width is reduced. Under the circumstances, the sectional gap between the lower reinforcing bar  2   a  and the upper reinforcing bar  3   a  is reduced (with reference to Table 1). Although it is possible to further increase the small rooms in number, it is desired to determine the number of small rooms with respect to cost effectiveness, inasmuch as cost increases in the execution of construction when the number of small rooms increases.  
      It is possible to form the concrete slab of the present invention by casting the concrete in the mold form having the slab bone structure, and by casting off the concrete slab from the mold form after aging. On forming the plane lattice concrete slab, the slab bone structure may be made on site. Alternatively, the half PC construction method or the full PC construction method is used according to the precast concrete plate.  
      Inasmuch as the light weight body positioned in the small space has a spherical shape in the plane lattice hollow concrete slab, it is unnecessary to align the light weight body in orientation on the execution of construction. In addition, it is very easy to fix the light weight ball body to the predetermined position by using the cross arm brace of the present invention. As a result, it is possible to exercise the slab strength and the sound insulating property based on the design. Furthermore, it is possible to obtain a high balance between lightness and rigidity by reducing the interval between lower reinforcing bars and/or between the upper reinforcing bars and by positioning smaller light weight ball body in the small space. It is possible to interrupt the transmission of sound by a plurality of small spaces and the light weight ball body positioned in each of the small spaces. As a result, it is recognized that sound having a wavelength range is attenuated. More specifically, it is possible to greatly improve the sonic boom of floor that occurs in a collective housing, a hotel, a school, a warehouse, a multilevel car parking tower, or the like.