AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Standard Patent Applicant (s) SEKISUI HOUSE, LTD Invention Title: FLOOR STRUCTURE FOR WOODEN BUILDING The following statement is a full description of this invention, including the best method for performing it known to me/us: Floor Structure for Wooden Building TECHNICAL FIELD The present device relates to a floor structure for a wooden building that is provided with a horizontal floor structural plane bounded by girders or the like. BACKGROUND ART A typical floor structure in accordance with conventional wood frame construction has been constituted such that a plurality of bridging members are arranged in mutually parallel fashion in a floor structural plane in which girders, beams, and so forth are assembled into a rectangular shape, flooring being laid over these bridging members. Furthermore, as shov A in FIG. 18, the constitution may also be such that a plurality of bridging members 103 are assembled over a floor structural plane comprising girders 101 and beams 102, flooring 104 being laid over these bridging members 103, and ALC panels 105 being fastened by screws over this flooring 104. As such conventional floor structures have employed a multiplicity of bridging members 103, the task of installing bridging members 103 has involved much time and trouble, and fabrication of bridging members 103 has required the sort of technical knowledge that is only gained from long years of experience. Furthermore, in conventional floor structures, the flooring and the frame containing girders and so forth have not constituted an integral structure. This being the case, external forces due to earthquakes, wind pressure, and so forth have been borne entirely by the frame, it being only the live load that has been borne by the flooring and ALC panels. Accordingly, there has been the disadvantage that the in-plane shear strength possessed by flooring and ALC panels has not been allowed to function effectively, with the result that there has been a tendency for rigidity of the floor structural plane to be insufficient with respect to lateral sway due earthquakes and storms. Furthermore, due to the high parts count and the many operations involved in constructing a conventional wooden building, slight dimensional errors at the various parts have had an effect on construction precision, and have been responsible for dimensional errors in the finished building. SUMMARY OF DEVICE PROBLEM TO BE SOLVED BY DEVICE lA The present device was conceived in light of problems such as the foregoing, it being an object thereof to provide a floor structure for a wooden building that allows reduction in the number of parts required for the floor structure of the wooden building, while at the same time permitting effective exploitation of the in-plane shear strength possessed by subfloor boards or the like, and that allows increased rigidity in the floor structural plane, and also excels in ease of construction and affordability. MEANS FOR SOLVING PROBLEM To achieve the foregoing object, in the context of a floor structure for a wooden building provided with a floor structural plane in which one or more girders and one or more beams are assembled into a rectangular shape, a floor structure for a wooden building in accordance with the present device has a constitution in which the floor structural plane is formed such that a height of a top surface of at least one of the girder or girders and a height of a top surface of at least one of the beam or beams are aligned so as to be at the same level; at least one subfloor board rests on the floor structural plane, at least one edge region of said at least one subfloor board being secured to at least one of the girder or girders and/or at least one of the beam or beams; and flooring is laid over a top surface of the at least one subfloor board. By adopting such a constitution, because subfloor board(s) is/are made to constitute an integral structure in combination with girder(s) and beam(s) making up the floor structural plane, the in-plane shear strength possessed by subfloor board(s) can be made to function effectively. Furthermore, in the context of a floor structure for a wooden building provided with a floor structural plane in which one or more girders and one or more beams are assembled into a rectangular shape, a floor structure for a wooden building in accordance with the present device has a constitution in which the floor structural plane is formed such that a height of a top surface of at least one of the girder or girders and a height of a top surface of at least one of the beam or beams are aligned so as to be at the same level; a plurality of ALC panels rest on the floor beam structural plane, edge regions of the respective ALC panels being secured to at least one of the girder or girders and/or at least one of the beam or beams by means of nails and/or screws; at least one subfloor board rests on top surfaces of at least a portion of the ALC panels such that a plurality of the ALC panels are straddled thereby, at least one 2 edge region of said at least one subfloor board being secured to at least a portion of the ALC panels; and flooring is laid over a top surface of the at least one subfloor board. By adopting such a constitution, in-plane shear force(s) transmitted to ALC panel(s) will spread through such ALC panel(s) in planar fashion, and will further travel from ALC panel(s) to subfloor board(s) as such force(s) propagate from plane(s) to plane(s). This makes it possible to cause shear stress(es) to be transmitted in planar fashion at ALC panel(s) and subfloor board(s), making it possible to prevent occurrence of stress(es) that might otherwise act in local fashion. In-plane shear strength possessed by ALC panel(s) and so forth is therefore allowed to function effectively, permitting formation of a floor structural plane having high rigidity. Furthermore, in the context of a floor structure for a wooden building provided with a floor structural plane in which a plurality of girders and one or more beams are assembled into a rectangular shape, a floor structure for a wooden building in accordance with the present device has a constitution in which the floor structural plane is constituted such that a height of a top surface of at least one of the beam or beams, the at least one beam being installed so as to span at least two of the girders, is lower than a height of the top surfaces of the at least two girders; a plurality of ALC panels are fitted within the floor structural plane and are supported by the at least one beam which is installed so as to span at least two of the girders; at least one subfloor board rests on top surfaces of at least a portion of the ALC panels such that a plurality of the ALC panels are straddled thereby, at least one edge region of said at least one subfloor board being secured to at least a portion of the ALC panels; and flooring is laid over a top surface of the at least one subfloor board. By adopting such a constitution, this will make it possible for ALC panel(s) to be arranged within a floor structural plane through employment of a simple procedure; moreover, this will make it possible to cause shear stress(es) to be transmitted in planar fashion at ALC panel(s) and subfloor board(s), preventing occurrence of stress(es) that might otherwise act in local fashion; and make it possible for the in-plane shear strength possessed by ALC panel(s) and so forth to function effectively. Furthermore, in the context of a floor structure for a wooden building provided with a floor structural plane in which a plurality of girders and one or more beams are assembled into a rectangular shape, a floor structure for a wooden building in accordance with the present device has a constitution in which the floor structural plane is provided with at least 3 one cleat along at least one side face of at least one of the girder or girders and/or at least one of the beam or beams; a plurality of ALC panels are fitted within the floor beam structural plane and are supported by the at least one cleat; at least one subfloor board rests on top surfaces of at least a portion of the ALC panels such that a plurality of the ALC panels are straddled thereby, at least one edge region of said at least one subfloor board being secured to at least a portion of the ALC panels; and flooring is laid over a top surface of the at least one subfloor board. This will make it possible for ALC panel(s) to be arranged within a floor structural plane through employment of a simple operation; moreover, this will make it possible to cause shear stress(es) to be transmitted in planar fashion at ALC panel(s) and subfloor board(s), preventing occurrence of stress(es) that might otherwise act in local fashion; and make it possible for the in-plane shear strength possessed by ALC panel(s) and so forth to function effectively. The floor structure for a wooden building may be constituted such that at least one constraining member is provided over at least one top surface of at least one of the girder or girders; wherein the at least one constraining member corresponds in size to at least one of the ALC panels; and wherein the at least one constraining member constrains at least a portion of the plurality of ALC panels which are fitted within the floor structural plane from being displaced in at least one horizontal direction. This will make it possible to prevent joint(s) between ALC panels from becoming loose and/or misaligned when the ALC panel(s) is/are acted upon by in-plane shear force(s), and will make it possible for ALC panels to be secured at the floor structural plane in such fashion that they are in intimate contact. Furthermore, the floor structure for a wooden building may be constituted such that the at least one subfloor board is placed so as to straddle a plurality of the ALC panels and at least one of the girder or girders, is secured to at least a portion of these ALC panels and girder or girders, and constrains at least a portion of the ALC panels from being displaced in at least one horizontal direction. Because subfloor board(s) is/are secured so as to straddle joint(s) between ALC panels, this will make it possible to constrain ALC panel(s) from becoming misaligned in the joint direction, permitting improvement in proof stress and/or rigidity with respect to in-plane shear forces. 4 Furthermore, it is preferred that the floor structure for a wooden building be constituted such that, in at least one location where a column extending in upright fashion above at least one of the girder or girders would otherwise interfere with the at least one subfloor board, at least one cutout conforming to a cross-sectional shape of the column is provided at at least one edge of the at least one subfloor board so as to permit the column to pass therethrough uninterrupted by the at least one subfloor board. Moreover, it is preferred that the floor structure for a wooden building be constituted such that at least one column foot fixture having at least one planar plate portion is secured to at least one of the girder or girders and/or at least one of the beam or beams; the at least one subfloor board is laid so as to be backed away from the centerline of at least one of the girder or girders and/or at least one of the beam or beams by an amount corresponding to a thickness of the at least one plate portion; at least one column having at least one slit at an end thereof is made to stand upright above a top surface of the at least one subfloor board; and the at least one plate portion is inserted in the at least one slit of the at least one column so as to form a connection therebetween. Furthermore, the floor structure for a wooden building may be constituted such that at least one of the beam or beams is an I-beam having a pair of wooden flanges that are mutually opposed such that one is an upper flange and the other is a lower flange, and a wooden web linking the two flanges. Not only will an I-beam be lighter as compared with beam stock having rectangular cross-section, but it will also have high strength, so it may be utilized to good effect as beam(s) making up the floor structural plane. Furthermore, because use of I-beam(s) permits flooring and ceiling material to be applied directly thereover, this will make it possible for the floor structure to be formed extremely simply. Furthermore, in the context of a floor structure for a wooden building provided with a floor structural plane in which one or more girders and a plurality of beams are assembled into a rectangular shape, a floor structure for a wooden building in accordance with the present device has a constitution in which ceiling material for a lower-story living space is laid at a top face of at least one of the beams; flooring for an upper-story living space is laid, by way of bridging, over a top surface of said ceiling material; and at least a portion of the plurality of beams are exposed at a ceiling surface of the lower-story living space. By adopting such a constitution, this will make it possible to achieve a finishing method in which beam(s) remain exposed at ceiling surface(s) of living space(s), and will 5 make it is possible to engender a feeling of spacious expansiveness in living space(s), permitting improvement in design characteristics. Furthermore, in the context of a floor structure for a wooden building provided with a floor structural plane in which one or more girders and one or more beams are assembled into a rectangular shape, a floor structure for a wooden building in accordance with the present device has a constitution in which, where there is a difference in combined thickness of subflooring and flooring between a first and a second mutually adjacent living space, a height of a top surface of at least one of the beam or beams is adjusted so as to be lower than a height of a top surface of at least one of the girder or girders at the first living space, so as to cause a level of a floor surface in the first living space to be even with a level of a floor surface in the second living space. By adopting such a constitution, this will make it possible, even where floor specifications differ between two adjoining living spaces, to cause the heights of the floor surfaces at the two living spaces to become mutually aligned so as to be at the same level, without production of a step between the respective floor surfaces. BENEFIT OF DEVICE Because a floor structure for a wooden building in accordance with the present device and having constitution as described above will permit effective exploitation of in-plane shear strength possessed by subfloor board(s) and/or the like, this will allow increased rigidity in the floor structural plane as well as reduced horizontal deformation of the building, and will make it possible to achieve prolongation of building life. Furthermore, a floor structure for a wooden building in accordance with the present device permits reduction in constituent parts, permits provision of tolerance for dimensional errors as well as construction-related errors, and makes it possible to achieve a wooden building excelling in ease of construction, affordability, and design characteristics. BRIEF DESCRIPTION OF DRAWINGS FIG. I is a perspective view showing a floor structure for a wooden building associated with a first embodiment. FIG. 2 is a partial sectional view of the floor structure shown in FIG. 1. 6 FIG. 3 is an exploded perspective view illustrating an example of how a post might be made to stand in upright fashion at the foregoing floor structure. FIG. 4 is a perspective view showing a floor structure for a wooden building associated with a second embodiment. FIG. 5 is a partial sectional view of the floor structure shown in FIG. 4. FIG. 6 is an exploded perspective view illustrating an example of how a post might be made to stand in upright fashion at the foregoing floor structure. FIG. 7 is a partial sectional view showing a floor structure for a wooden building associated with a third embodiment. FIG. 8 is a perspective view showing a floor structure for a wooden building associated with a fourth embodiment. FIG. 9 is a partial sectional view of the floor structure shown in FIG. 8. FIG. 10 is a partial sectional view showing a variation on the floor structure associated with the fourth embodiment. FIG. 11 is a perspective view showing a floor structure for a wooden building associated with a fifth embodiment. FIG. 12 is a partial sectional view of the floor structure shown in FIG. 11. FIG. 13 is a partial sectional view showing a floor structure for a wooden building associated with a sixth embodiment. FIG. 14 is a perspective view showing a floor structure for a wooden building associated with a seventh embodiment. FIG. 15 is a sectional view showing a floor structure for a wooden building associated with an eighth embodiment. FIG. 16A is a partial sectional view showing a floor structure for a wooden building associated with a ninth embodiment, and FIG. 16B is a partial sectional view in a direction perpendicular to that of FIG 16A. FIG. 17 is a partial sectional view showing a floor structure for a wooden building associated with a tenth embodiment. FIG. 18 is a perspective view showing a conventional wooden building floor structure. EMBODIMENTS FOR CARRYING OUT DEVICE 7 Below, embodiments of the present device are described with reference to the drawings. EMBODIMENT I First, referring to FIGS. I through 3, basic constitution of a floor structure in a wooden building associated with the present device is described. At wooden building 1, girders and beams are joined and assembled in rectangular fashion to form a structural plane. Girders, which are directly joined to structurally important columns to constitute a frame, are horizontal structural members that bear the load from the beams. Beams, which are horizontal structural members that are joined to girders and/or columns, serve to support bridging, subflooring, and so forth. Girders and beams are joined by way of beam bearing fixtures. At the floor structural plane shown in FIG. 1, these girders and beams 22 are joined such that the heights of their top surfaces are even. At the floor structural plane, a plurality of beams 22 are arranged with prescribed spacing therebetween. Between pairs of these beams 22, a plurality of bridging members are installed with constant spacing therebetween in a direction perpendicular to beams 22. Subflooring is provided over this floor structural plane. Structural plywood 32 or similar board-like material or the like is used as subflooring. Subflooring may be arranged on top surfaces of bridging installed between beams 22; or as shown in FIG. 1, subflooring may be provided in integral fashion with bridging 24. In an exemplary embodiment, structural plywood 32 serving as subflooring is constituted by modular panels in the form of floor panels 30. Floor panel 30, formed by attaching bridging 24 comprising squared wood timber with constant spacing therebetween to one face of rectangular structural plywood 32, permits simplification of field operations. Channel-shaped bearing fixtures 71 for supporting bridging 24 are attached to side faces of beams 22 in such fashion as to correspond to the spacing of bridging 24. These bearing fixtures 71 are attached at heights such as will cause the top surfaces of bridging 24, which is supported thereby, and the top surfaces of beams 22 to be coplanar. Floor panel 30 is dropped into place between side faces of beams 22 arranged in mutually parallel fashion. At such time, as shown in FIG. 2, floor panels 30 are such that edges of structural plywood 32 are placed so as to overlap beams 22 for approximately half of their widths, and are secured such that bridging 24 respectively engages with bearing fixtures 8 71. Structural plywood 32 is secured to beams 22 by means of nailing, screws, or the like. Flooring is laid over the top surface of structural plywood 32. Furthermore, ceiling material 41 is applied to the bottom faces of beams 22, forming a ceiling surface and concealing beams 22 and bridging 24. As a result, bridging 24 is formed such that the top surfaces thereof are coplanar with the top surfaces of beams 22. Bridging 24 and beams 22 constitute a floor structural plane, subflooring (structural plywood 32) being arranged over the top surfaces thereof. Furthermore, structural plywood 32 constitutes an integral structure together with the girders 21 and beams 22 that make up the floor structural plane. As a result, the in-plane shear strength possessed by structural plywood 32 can be made to function effectively, making it possible to improve rigidity of the floor structural plane with respect to lateral sway and so forth. Furthermore, describing the situation in which a post 27 is made to stand in upright fashion at such floor structural plane, as shown in FIG. 2, beam 22 is joined to beam 22 (or girder) by way of column foot fixture 73. Column foot fixture 73 might, for example, be such that tenon pipe 731, and planar joint plate 732 which is linked to one end thereof, are welded integrally together in strap bolt fashion. Column foot fixture 73 is provided with a plurality of dowel holes into which dowel pins and/or bolts may be inserted. As shown in FIG. 3, column foot fixture 73 is installed such that tenon pipe 731 is inserted in a mortise formed in beam 22 (or girder), and joint plate 732 is made to protrude from the top surface of beam 22. Column foot fixture 73 is linked to beam 22 by means of dowel pins or the like, not shown. Structural plywood 32 is placed on beam 22 such that the edge of the former overlaps the latter by an amount corresponding to approximately half of the beam width. Describing this in more detail, the edge of structural plywood 32 is placed so as to be backed away from the centerline of beam 22 by an amount corresponding to half of the thickness of joint plate 732. Because joint plate 732 is a thin plate, even where the edge of structural plywood 32 has not been provided with a cutout, it is nonetheless possible to arrange the edge of structural plywood 32 so that it is extremely near to the centerline of beam 22. Structural plywood 32 is thus provided over the top surface of beam 22, and post 27 is linked to joint plate 732, which protrudes in upright fashion from the joint between sheets of structural plywood 32. Slit 271 is formed at the bottom of post 27, a plurality of dowel holes 9 being formed so as to extend through this slit 271. Post 27 is made to stand in upright fashion over structural plywood 32 such that joint plate 732 is inserted into slit 271. In addition, dowel pins (and/or bolts) 81 are inserted into dowel holes from a side face of post 27, linking causing post 27 and column foot fixture 73 in integral fashion. EMBODIMENT 2 Next, a floor structure for a wooden building associated with a second embodiment is described with reference to FIGS. 4 through 6. Note that, at the descriptions of the respective embodiments below, components that have been previously covered are assigned like reference numerals and detailed description thereof will be omitted. In the present second embodiment, ALC panels 34 are placed over the floor structural plane, subflooring and flooring being laid over the ALC panels 34. As shown in FIG. 4, ALC panels 34, which are slab panels, are placed over a floor structural plane comprising girders 21 and beams 22. Heights of top surfaces of girders 21 and beams 22 are aligned so as to be at the same level. ALC panel 34 is formed such that the dimension in the long direction thereof is approximately equal to the spacing of beams 22. ALC panel 34 is placed such that either end in the long direction thereof is on a top surface of a beam 22. In addition, screws 85 are driven into both ends in the long direction of ALC panel 34 so as to secure ALC panel 34 to the horizontal structural members. As shown in FIG. 5, reinforcing bar(s) 342 are set into ALC panel 34 at location(s) on the order cof 15 to 30 mm toward the interior from the ends thereof in the long direction. Screw(s) 85 are driven thereinto at location(s) toward the interior from said reinforcing bar(s) 342. Furthermore, as shown in FIG. 4, cotters 35 are inserted at a plurality of locations along long edges of adjacent ALC panels 34. Cotters 35 are hollow or solid cylindrical members. Respective cotters 35 are secured such that they engage with cylindrical holes, not shown, formed so as to straddle mutually adjacent ALC panels 34. Cotters 35 prevent in plane shear forces that act on ALC panels 34 from causing displacement of ALC panels 34 and misalignment ofjoints at the long edges thereof. This makes it possible to ensure that ALC panels 34 will have high in-plane shear strength and in-plane shear rigidity. 10 Particle boards 36 serving as subflooring are arranged over the top surfaces of ALC panels 34. Particle boards 36 are formed by adding adhesive to wood shavings, chips, or the like, and hot-pressing this to obtain single-ply or multi-ply boards. Particle boards 36 are laid so as to be oriented perpendicularly with respect to ALC panels 34, and such that each sheet of particle board 36 straddles a plurality of ALC panels 34. A portion of the joints at long edges of particle boards 36 coincide with joints at short edges of ALC panels 34; furthermore, a portion of the joints at short edges of ALC panels 34 coincide with joints at long edges of particle boards 36. Screws 85 are driven into these particle boards 36 in uniform fashion to secure particle boards 36 to ALC panels 34. Because ALC panel 34 has reinforcing bar(s) 3b at end(s) thereof, even where screw(s) 85 is/are driven into an end thereof and in-plane shear forces act thereat, this will not fail easily. Because there is a large ratio between the length and width of ALC panel 34, there is a much greater tendency for in-plane shear forces to cause relative displacement between ALC panels 34 to occur at joints between long edges thereof than at joints between short edges thereof. However, in the present embodiment, joints at long edges of ALC panels 34, which mutually adjoin in their width direction, are constrained such that they do not become misaligned by particle boards 36. That is, every set of four sheets of ALC paneling 34 forms an integral structure in combination with two sheets of particle board 36. As a result, when in-plane shear forces act on ALC panels 34, ALC panels 34 and particle boards 36 constrain one another in out-of-plane fashion, preventing occurrence of misalignment of joints, and making it possible to ensure adequate proof stress and rigidity with respect to in-plane shear forces. Furthermore, ALC panels 34 and particle boards 36 can be secured in integral fashion by means of a simple operation employing screws 85 or the like, and it is possible form a floor structure having excellent in-plane shear strength and in-plane shear rigidity. An in plane shear force transmitted to ALC panels 34 will spread through said ALC panels 34 in planar fashion, and will further travel from ALC panels 34 to particle boards 36 as it propagates from plane to plane. This makes it possible to cause shear stresses to spread in planar fashion, making it possible to prevent occurrence of large stresses that might otherwise act in local fashion. Thus, the floor structure associated with the second embodiment makes it possible to cause the in-plane shear strength possessed by slab panels to function effectively, and while
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simplifying joining of respective parts, makes it possible to reduce the effect of dimensional errors and installation errors. Note that where wooden building I has two or more stories, as shown in FIG. 6, upper-story column (post 27) is joined to the top surface of girder 21, which is joined to balloon column 26. Post 27 is made to stand in upright fashion above the top surface of girder 21 by way of pipe-like joint fixture 75. Cutouts 341 corresponding to the external shapes of posts 27 and balloon columns 26 are formed in particle boards 36 and ALC panels 34 arranged in abutting fashion with respect to these columns. EMBODIMENT 3 Next, a floor structure for a wooden building associated with a third embodiment is described with reference to FIG. 7. The floor structure associated with the present embodiment is such that, in the context of a floor structural plane comprising a plurality of beams 22 and a plurality of girders 21 arranged in mutually parallel fashion, heights of top surfaces of beams 22 are at a level that is lower than heights of top surfaces of girders 21. As shown in FIG. 7, top surfaces of beams 22 are arranged such that their heights are at a level that is lower than top surfaces of girders 21 by an amount corresponding to the thickness of ALC panels 34. That is, girders 21 are provided in such fashion as to be coplanar with top surfaces of ALC panels 34. ALC panel 34 and girder 21 are such that at one side face of girder 21 the butt end of ALC panel 34 comes in contact with said side face of girder 21. Furthermore, at the other side face of girder 21, clearance 37 on the order of 20 mm is provided between it and the butt end of ALC panel 34. This clearance 37 makes it possible to adjust for errors in respective dimensions of ALC panel(s) 34, girder(s) 21, and beam(s) 22, as well as construction-related errors. Groove 343 is formed at the joint between mutual long edges of adjacent ALC panels 34. Said groove 343 is filled with mortar 345. Besides connecting adjacent ALC panels 34, the mortar 345 which fills this groove 343 also acts to close any gap which would otherwise be detrimental from the standpoints of soundproofing and fireproofing. Furthermore, because one can place one's hand in groove 343 when holding ALC panel(s) 34, this facilitates ALC panel 34 installation operations, and helps prevent damage to ALC panel 34 when it is being 12 dropped into place over the top surfaces of beams 22. Structural plywood 32 is placed over the top surfaces of ALC panels 34 and girders 21 in such fashion as to straddle the joints between ALC panels 34, and is secured thereto by nailing or the like. Structural plywood 32 may be secured using both nails and polyvinyl-acetate-type adhesive, permitting elimination of any slight step(s) that might otherwise arise between/among ALC panel(s) 34, girder(s) 21, and structural plywood 32. EMBODIMENT 4 Next, a floor structure for a wooden building associated with a fourth embodiment is described with reference to FIGS. 8 through 10. In the floor structure associated with this fourth embodiment, heights of top surfaces of beams 22 are lower than heights of top surfaces of girders 21. Furthermore, the top surfaces of ALC panels 34, which are arranged within the floor structural plane, are higher than the top surfaces of girders 21. As shown in FIG. 8, between girders 21 which are spanned by beams 22, four ALC panels 34 are dropped into place over the top surfaces of beams 22 so as to be oriented perpendicularly with respect to said beams 22. The dimension in the long direction of ALC panel 34 is approximately equal to the spacing of beams 22. Furthermore, ALC panel 34 is such that either end in the long direction thereof is secured by means of screw(s) or the like to a top surface of a beam 22. Cotters 35 serving as joint misalignment prevention means are arranged at joints between long edges of ALC panels 34. Cotters 35 prevent misalignment of joints at the long edges of ALC panels 34 due to in-plane shear forces that act on ALC panels 34. Furthermore, when the four ALC panels 34 arranged between girders 21, 21 are acted upon by an in-plane shear force, there is a tendency for the joints between the long edges thereof to become loose. In the present embodiment, constraining member(s) is/are therefore arranged so as to prevent such loosening of joints. Slat(s) 51 comprising particle board might, for example, be used as such constraining member(s). Slat 51 is formed so as to be somewhat shorter than the length of ALC panel 34. Slat 51 is dropped into place in the space between adjacent ALC panels 34, being disposed above the top surface of girder 21. Screws 85 are driven into girder 21 from the top surface of 13 slat 51 to secure slat 51 thereto. Note that it is also possible to secure slat 51 to girder 21 by means of adhesive. Because slat 51 is somewhat shorter than the length in the long direction of ALC panel 34, a crowbar, jack, or the like may be inserted in the space between girder 21 and the butt end along the long edge of ALC panel 34 (the portion thereof that does not abut slat 51). The four ALC panels 34 can then be pressed so that they are made to come in close contact, and while held in this state, slat 51 can be secured to girder 21. Note that it is preferred that slats 51 be arranged such that no single slat 51 straddles a plurality of ALC panels 34 in the long direction of ALC panels 34. This makes it possible to more easily compensate for dimensional errors at ALC panels 34. As shown in FIG. 9, where ALC panel 34 adjoins girder 21, one side face of girder 21 is directly abutted by the butt end of an ALC panel 34. Between this ALC panel 34 and slat 51, clearance 37 is provided. Furthermore, at the other side face of girder 21, the butt end of another ALC panel 34 is arranged such that clearance 37 intervenes between it and girder 21, being provided such that it is abutted by the side face of slat 51. As a result, ALC panels 34 are constrained by slats 51 from being displaced in the horizontal direction. Furthermore, the clearance between girder 21 and ALC panel 34 provides tolerance for construction-related errors as well as errors in dimensions of ALC panel(s) 34 and girder(s) 21. Furthermore, slat(s) 51 constituting constraining member(s) may also be provided as shown in FIG. 10. Here, the top surface at the end of ALC panel 34 which adjoins girder 21 is notched to form recess 346. Slat 51 serving as constraining member is placed so as to straddle the top surface of girder 21 and recess 346 of ALC panel 34, being secured by means of screws 85 to girder 21 and ALC panel 34. As a result, the positions of ALC panels 34 are constrained in the horizontal direction. Furthermore, groove 343 is formed at the joint between mutual long edges of adjacent ALC panels 34. Groove 343 is filled with mortar 345, mutually connecting adjacent ALC panels 34 and preventing formation of gap(s) therebetween Furthermore, threaded round pipe, not shown, might also be driven into groove(s) 343 between ALC panels 34, and this might be filled with mortar so as to connect these in integral fashion. By passing a reinforcing bar through the pipe portion of the threaded round pipe, the threaded round pipe can be made to prevent rotation of ALC panel 34. 14 As shown in FIG. 10, where ALC panel 34 and girder 21 adjoin, one side face of girder 21 is abutted by the butt end of an ALC panel 34. Between this ALC panel 34 and slat 51 at the top surface of girder 21, clearance 37 is provided. Furthermore, at the other side face of girder 21, clearance 37 is provided between it and the butt end of another ALC panel 34, slat 51 being arranged such that it straddles recess 346 of ALC panel 34 and girder 21 in such fashion as to cap this clearance 37. These clearances 37 provide tolerance for construction related errors as well as errors in dimensions of ALC panel(s) 34 and girder(s) 21. Note that it is preferred that slat 51 be a material of higher strength than ALC panel 34; besides particle board, it may be selected as appropriate from among plywood and other such wooden materials; fiber-cement sheeting, calcium silicate board, and other such cement type materials; plastic-type materials; metal-type materials; and so forth. Furthermore, as constraining member for ALC panels 34, besides the foregoing slat 51, it is also possible to use, for example, angle bar stock (angle iron/steel) or the like. EMBODIMENT 5 Next, a floor structure for a wooden building associated with a fifth embodiment is described with reference to FIGS. I I and 12. In the present embodiment, wooden cleat 61 is arranged at the side face of girder 21 in parallel fashion with respect to girder 21. Cleat 61 serves as support member for ALC panel 34. As shown in FIG. 11, the floor structural plane is formed such that the top surfaces of girders 21 and beams 22 are coplanar. Furthermore, ALC panels 34 are fitted within the space between these girders 21 and beams 22, the constitution being such that either end at the underside of each of those ALC panels 34 is supported by a cleat 61. Each ALC panel 34 is arranged such that either end in the long direction thereof rests on a cleat 61. Cleat 61 comprises squared timber of rectangular cross-section; alternatively, this may be squared timber or the like of trapezoidal cross-section having upper width greater than lower width, or may take some other form. In an exemplary embodiment, cleats 61 are secured to girders 21 and beams 22 by means of nailing. Furthermore, cleats 61 are attached such that the heights of the top surfaces thereof are lower than the top surfaces of the girders 21 by an amount corresponding to the thickness of ALC panel 34. 15 The dimension in the long direction of ALC panel 34 is set so as to be a prescribed amount shorter than the space between girder 21 and beam 22, or between adjacent beams 22. As shown in FIG. 12, this permits creation of clearance 37 between the end in the long direction of ALC panel 34 and girder 21 or beam 22. Furthermore, ALC panels 34 are arranged such that the top surfaces thereof are coplanar with the top surfaces of girders 21 and beams 22. A plurality of sheets of structural plywood 32 are placed over the top surfaces of ALC panels 34 and the top surfaces of girders 21 and beams 22. Structural plywood 32 is secured by means of nails 83 to the top surfaces of girders 21 and/or beams 22, and is secured by means of screws 85 to the top surfaces of ALC panels 34. As shown in FIG. 11, at the central region of a sheet of structural plywood 32, screws 85 are driven into ALC panel 34 in parallel fashion with respect to the long direction thereof. Where structural plywood 32 abuts balloon column 26, a cutout 361 similar to that shown in FIG. 6 is provided so that passage of balloon column 26 therethrough can take place in uninterrupted fashion. Thus, to either side across a joint between long edges of structural plywood 32, the structural plywood 32 is secured to the same ALC panel 34; furthermore, to either side across ajoint between short edges of structural plywood 32, the structural plywood 32 is secured to the same girder 21 or beam 22. This makes it possible to greatly reduce joint misalignment between adjacent sheets of structural plywood 32. As a result, a plurality of sheets of structural plywood 32 combine in integral fashion, and provide excellent shear strength and shear rigidity. EMBODIMENT 6 Next, a floor structure for a wooden building associated with a sixth embodiment is described with reference to FIG. 13. In the present embodiment, an example is shown of use of angle bar stock as support member for ALC panel 34. As shown in FIG. 13, long cleats 63 comprising angle bar stock having L-shaped cross-section is attached to side faces of girders 21 and beams 22. These cleats 63 are secured by means of screws.85 to side faces of girders 21 and beams 22 in such fashion as to cause top surfaces of girders 21 and beams 22, and top surfaces of ALC panels 34 which are 16 supported by these cleats 63, to be approximately coplanar. Nails, anchor bolts, or the like may be used instead of screws 85 to secure this thereto. Furthermore, in an exemplary embodiment, planar intermediate member 38 is laid over the top surfaces of girders 21, beams 22, and ALC panels 34. As intermediate member 38, which is provided for the purposes of level adjustment and improvement of soundproofing characteristics, asphalt-impregnated felt might, for example, be used. Furthermore, especially with regard to improvement of soundproofing characteristics, it can be an effective strategy to achieve increased mass by employing asphalt-impregnated felt that is made to contain mass-increasing material comprising powdered lead, iron, or the like. Besides these, as intermediate member 38, it is also possible to employ material of thickness on the order of 2 to 50 mm comprising rubber sheeting; nonwoven fabric; material having cement-like properties; material having calcium silicate-like properties, material having clay like properties, or other such ceramic-like material; or the like. Structural plywood 32 is placed over the top surface of intermediate member 38, and this is secured by means of screws 85. By varying thickness of intermediate member 38, adjustment of floor surface level can be easily carried out. In the present embodiment, cleat 63 protrudes below the underside of ALC panel 34 only by an amount corresponding to its thickness, which is small compared with that of cleat 61 in the foregoing fifth embodiment. This makes it possible to form a large space without obtrusions beneath ALC panels 34, ensuring availability of adequate room for plumbing or the like. Furthermore, it is preferred that clearance on the order of 10 to 20 mm be established between side faces of ALC panel 34 and girder 21 or beam 22 so as to allow tolerance to be provided for construction-related errors as well as errors in dimensions of ALC panel(s) 34, girder(s) 21, and so forth. Note that it is preferred that the member employed as intermediate member 38, which intervenes between structural plywood 32 and ALC panels 34, possess at least one of the following functionalities: functionality for adjusting minor out-of-level conditions occurring at the surface of ALC panels 34; functionality for soundproofing to reduce impact sounds, airborne sounds, and so forth; functionality for increasing or decreasing in-plane shear rigidity so as to permit adjustment thereof. 17 EMBODIMENT 7 Next, a floor structure for a wooden building associated with a seventh embodiment is described with reference to FIG. 14. In this seventh embodiment, as shown in FIG. 14, beams 22 are arranged at lower heights than girders 21. That is, beams 22 are disposed at locations such that their top surfaces are lower than the top surfaces of girders 21 by an amount equivalent to the thickness of ALC panels 34. Furthermore, each ALC panel 34 spans the top surfaces of a pair of parallel beams 22 that link girders 21. As a result, the top surfaces of a plurality of ALC panels 34, and the top surfaces of girders 21, are coplanar. Moreover, structural plywood 32 is secured by means of screws 85 and adhesive to girders 21 and ALC panels 34. As shown in the drawing, any given ALC panel 34 is constrained from being displaced in the horizontal direction by structural plywood 32, which is secured to other ALC panel(s) 34 and to the top surface(s) of girder(s) 21. Here, because structural plywood 32 is secured to girder(s) 21 as well as other ALC panel(s) 34, this is preferred, since the degree to which it is constrained is greater than would be the case were it only secured to girder(s) 21. Furthermore, because ALC panels 34 arranged to either side of girder 21 in such fashion that girder 21 intervenes therebetween can be linked by a single sheet of structural plywood 32, this permits ALC panels 34 to be combined in integral fashion over a wider area, makes it possible to inhibit rotation of ALC panels 34, and permits improvement in proof stress and rigidity. Furthermore, structural plywood 32 is arranged so as to be oriented perpendicularly with respect to ALC panels 34. This makes it possible for structural plywood 32 to be secured in such fashion that it straddles a plurality of ALC panels 34. That is, because structural plywood 32 is secured such that it straddles joints between ALC panels 34, this makes it possible to constrain the ALC panels 34 to either side of a joint from becoming misaligned in the joint direction, permitting improvement in proof stress and rigidity with respect to in plane shear forces. EMBODIMENT 8 Next, a floor structure for a wooden building associated with an eighth embodiment is described with reference to FIG. 15. 18 In the present eighth embodiment, description is given with respect to a floor structure in which beams 22 are aggressively exposed at the ceiling surface of lower-story living space(s) for the purpose of achieving improved design characteristics in living spaces within wooden building 1. As shown in the drawing, ceiling material 41 is laid at top faces of beams 22 to form the ceiling surface of a lower-story living space 11. Ceiling material 41 might, for example, be formed by applying a finishing layer to structural plywood of thickness 12 mm. Bridging 24 is arranged with appropriate spacing therebetween at the top surface of ceiling material 41. Furthermore, beams 22 are installed such that the top surfaces thereof are lower than the top surfaces of girders 21 by an amount corresponding to the combined height of bridging 24 and thickness of ceiling material 41. Above the top surfaces of bridging 24, structural plywood 32, which serves as subflooring for upper-story living space 12, and flooring 39 are arranged. Moreover, to improve soundproofing between the upper- and lower-story living spaces, the space between adjacent bridging members 24 is filled with sound absorbing material 43. As sound absorbing material 43, glass wool of thickness 50 mm might, for example, be used. Furthermore, also provided in the space formed between bridging members 24 is enclosure 45 for electric cable 49 and/or the like. Enclosure 45 is formed by arranging a portion of the bridging 24 such that there is tighter spacing therebetween. Ceiling material 41 at the bottom of enclosure 45 is provided with a routing hole for guiding electric cable 49 or the like to the ceiling surface. At the bottom of the floor structural plane, cover 47 having L-shaped cross-section is provided in such fashion as to cover the side of girder 21. Furthermore, electric cable 49 is threaded into enclosure 45 from the living space by way of a routing hole provided in girder 21, and is guided thereto by means of an appropriate routing hole. Such a floor structure makes it possible to form ceiling surfaces at two levels, there being an upper and a lower ceiling surface, after the fashion of a coved ceiling at the ceiling of lower-story living space 11, allowing ceiling height to be made higher at a portion thereof, and wherein a plurality of beams 22 run in the same direction such that the side surface of each such beam 22 is completely exposed at the upper ceiling surface. This being the case, it is possible to engender a feeling of wooden charm and spacious expansiveness, making it possible to improve the design characteristics of lower-story living space 11. Note that a 19 similar floor structure might also be achieved by arranging, above the top surfaces of beam 22, modular panels in which ceiling material 41 and subflooring (structural plywood 32) together with flooring 39 are combined in integral fashion by way of bridging 24. EMBODIMENT 9 Next, a floor structure for a wooden building associated with a ninth embodiment is described with reference to FIGS. 16A and 16B. Whereas the foregoing respective embodiments have been described in terms of examples in which squared wooden timbers having rectangular cross-section were employed as beams 22, beam 22 is not limited thereto, it being possible to employ I-beams comprising material(s) having wood-like properties therefor. As shown in FIGS. 16A and 16B, I-beam 23 has a pair of wooden flanges 231, 232, these being mutually opposed such that one is an upper flange and the other is a lower flange, and has wooden web 233 linking the two flanges, the I-beam being formed so as to have I shaped cross-section by press-fitting components together with use of adhesive therebetween. At I-beam 23, laminated veneer lumber (LVL), machine stress rated (MSR) lumber, or other such structural lumber may be used as upper and lower wooden flanges 231, 232; and structural plywood, oriented strand board (OSB), or other such laminated board(s) may be used as wooden web 233. Because I-beam 23 has I-shaped cross-section, not only will it be lighter as compared with beam stock having rectangular cross-section, but it will also have high strength due to its large second moment of area. I-beam(s) 23 may therefore be utilized to good effect as beam(s) 22 which will be light in weight and yet high in strength when constituting the floor structural plane. In such case, as shown in FIGS. 16A and 16B, beam 22 is supported at either end thereof by beam bearing fixture 77, which is attached to a side face of girder 21. Beam bearing fixture 77 is provided with channel-shaped support recess 771 that supports the side faces and bottom face of I-beam 23, and with attachment tabs 772 that respectively extend from either side of support recess 771. Beam bearing fixture 77 is secured by means of nailing or the like in such fashion that the two attachment tabs 772 abut the side faces of girder 21. The two ends of each I-beam 23 are dropped into place and secured to beam bearing fixtures 77, which are attached with prescribed spacing therebetween to side faces of 20 girders 21; furthermore, structural plywood 32 or other such subflooring, flooring 39, and so forth are arranged over the top surfaces thereof, such that these are supported thereby. Furthermore, ceiling material may be applied directly over lower flange(s) 232. This will obviate need for any hanger hardware, cross-runners, or other such members for supporting ceiling material, making it possible to reduce cost by means of a simple structure. EMBODIMENT 10 Next, a floor structure for a wooden building associated with a tenth embodiment is described with reference to FIG. 17. At wooden building 1, it may be that mutually different flooring employed at two adjoining living spaces separated by girder(s) 21 or other such horizontal structural member(s) that intervene therebetween causes there to be a large difference in the combined thickness of subflooring and flooring between the two living spaces. In such a situation, it is preferred that there not be a step where the respectively different flooring meets at the interface between the two living spaces. In the floor structure associated with the tenth embodiment, the floor framing of the two adjoining living spaces is therefore adjusted so as to prevent a step from occurring where the respectively different flooring meets at the interface therebetween. As shown in FIG. 17, living space 9A and living space 9B adjoin such that door 91 intervenes therebetween. One living space 9A might have ordinary flooring with a carpet or the like. In contradistinction hereto, the other living space 9B might be a shower, bathroom, or other such room where water is present. The floor structural plane is provided with girder 21 between living space 9A and living space 9B. At the living space 9B side thereof, beams 22 parallel with girder 21 are provided such that heights of the top surfaces thereof are at a level that is lower than the top surfaces of girder 21. Wooden cleat 61 is arranged at the side face of girder 21 in parallel fashion with respect to girder 21. Particle board 36 is arranged above the top surfaces of beam 22 and cleat 61. Cleat 61 supports the end of particle board 36. Above particle board 36, mortar 93 is applied as floor backing layer, and tiles 95 are laid as flooring. On the other hand, at living space 9A, particle board 36 is arranged over the top surface of girder 21, and flooring panels or other such flooring 39 is/are arranged over the top surface of that. As a result, at the boundary between living space 9A and living space 9B, at 21 which tiles 95 have been laid, the two floor surfaces are made to have approximately the same height, permitting formation thereof without production of a step therebetween. That is, by adjusting size(s) (beam depth(s)) of beam(s) 22 and/or the like that constitute the floor structural plane and support particle board 36 and so forth at living space 9B, it is possible to cause the level of the floor surface there to become aligned with that of adjoining living space 9A. INDUSTRIAL UTILITY The present device may be employed in floor structures of a wide variety of wooden buildings, including residential buildings and the like. 22