Patent Publication Number: US-2005120658-A1

Title: Joint structure of building using thin and lightweight shaped-steel

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a joint structure of a building using thin and lightweight shaped-steel, particularly a joint structure of an earthquake-resistant and wind-resistant building made of steel, for fastening a frame member made of thin and lightweight shaped-steel and a steel sill, and a bolt-joint truss structure constituting a main structure of a roof.  
      2. Description of the Related Art  
      Recently, earthquake-resistant and wind-resistant steel building are in demand. These steel buildings are constructed by shaped-steel members obtained by roll-forming a thin steel sheet, of 2.3 mm thickness or less, which members are used as frame members, sills or roof members as they are roll-formed or after being bent, wherein the respective members are fastened together directly or via a reinforcement member by screws to form a building frame. In the prior art, there are a number of joints in steel buildings for fastening and joining the respective members to each other. For example, these joints exist in a portion for fastening upper story sills and lower story sills with the frame members, a portion for fastening the frame members with each other, a portion for fastening the frame members with a steel or concrete base, a portion for fastening upper chord members with lower chord members, and a portion for fastening lattice members for joining the upper and lower chord members. In most of these fastening portions, reinforcing metallic members or joint metallic members are used for the reinforcement. In the roof structure, when a chevron type roof truss formed of shaped-steel members of approximately  1  mm thick is used two upper chord members and one lower chord or lattice member are disposed to form a triangle. They are then temporarily fixed by jigs and connected together in a joint area between the respective chord members by drilling-tapping screws.  
      A joint structure for fastening and fixing the above-mentioned members with each other will be described with reference to the prior art joint structure shown in  FIG. 1 .  
      First, in a portion for fastening the sill with the frame member, the joint structure between the respective members is that, as shown in  FIG. 1 , a frame member  1  constitutes a pillar for the upper story and a frame member  2  constitutes a pillar for the lower story. Ends of these frame members are orthogonally joined to tracks  3 ,  4  to define a T-shape. Also, a sill  5  is interposed between the tracks  3  and  4 , and another sill  6  is attached to the sill  5  in the vertical direction. A floor  7  is placed on the sill  6 . On the lateral side of the sill  5 , side wall members  8  are mounted to form a wall.  
      As the frame members  1  and  2  do not constitute an integral structure passing through the upper and lower stories but constitute an assembled structure, a space exists between both the frame members, for accommodating the sills  5  and  6 . In this space, the sills  5  and  6  are orthogonally brought into contact and joined with each other at a position directly beneath the frame member  1  and directly above the frame member  2 . As the joint in this contacting portion naturally requires reinforcement, a steel sheet member  9  formed merely by bending a steel sheet at a right angle is attached thereto with screws or rivets in the prior art.  
      However, for the purpose of weight reduction, the cross-section of the member  9  is as small as at most 50% of the joint area, resulting in a lack of strength. Particularly, when a large earthquake occurs or a strong wind blows, a considerable force is applied to the building, whereby a tensile force or a compressive force acts on the frame members to deform the sills  5  and  6 . This locally deforms the floor member or the ceiling member to incline the building and deteriorate the living environment.  
      On the other hand, as shown in FIGS.  2 ( a ) and  2 ( b ), a hold-down member  21  is used for securing the frame member to a steel or concrete base  10 . This hold-down member  21  is joined to the frame member  2  via a steel back plate  22  by fastener means such as screws. This hold-down member  21  includes steel side plates  23 ,  24  and a bottom plate  25  disposed between these side plates and attached thereto. A bolt hole  26  is provided in the vicinity of a center of the bottom plate  25 , into which a anchor bolt hole of the steel or concrete base  10  is inserted to fasten the anchor bolt and the hold-down member  21 . Since a diameter of the bolt hole provided in the bottom plate  25  is the same as or only slightly larger than that of the anchor bolt in many cases, it is difficult to align the hole provided in advance in the factory in the hold-down member  21  with the anchor bolt hole, whereby the assembly may often be disturbed. Also, as shown in  FIG. 2 ( b ), if the bottom plate  21  is provided above the hold-down member  21 , there is a risk in that the hold-down member  21  may be deformed when the anchor bolt is tightly fastened.  
      Next, a joint for a roof structure will be described. In the prior art roof structure, as shown in  FIG. 5 ( a ), upper chord members  50 ,  51  and opposite ends of a lower chord member  52  are connected to each other at the ends of the upper chord members to define a chevron shape. After attaching a lattice member  53 , disposed in a slanted manner if necessary, the chord members are temporarily fixed by a jig, and the joints between the respective chord members are joined together by drilling-tapping screws  54 . In this roof structure, a jig is necessary for temporarily fixing the upper chord members  50 ,  51  and the lower chord member or the lattice member  53 . To install the jig and the respective chord members, a space larger than a roof truss and having a horizontal plane with a high accuracy is required. As it is difficult to obtain such a space in situ, the roof truss is completed on a ground surface and is raised and transported to a ceiling surface before the installation in the actual assembly. However, the completed roof truss is very large in size and heavy in weight, and therefor is difficult to handle.  
      Also there are a number of other problems. For example, it is necessary to fasten the upper chord members  50 ,  51  and the lower chord member by driving at least four drilling-tapping screws into the respective joint portion; the number of screws may increase in accordance with sizes of the roof truss; since a yield strength of the screw is relatively low, a large number of screws, up to approximately 20, are necessary to guarantee the necessary joint strength; the operation for driving the screws is troublesome and non-efficient; the respective chord members must be accurately disposed for the purpose of positioning the joints; an off-line operation is necessary for providing the screw holes in advance in the respective chord members; or the joint strength may be lowered because more screws are driven in a narrower space at a smaller pitch. Further, as a thickness of the respective chord member is as thin as approximately  1  mm, local buckling may occur.  
     DISCLOSURE OF THE INVENTION  
      The present invention relates to a joint structure for a building using thin and lightweight shaped-steel members, and particularly to providing a joint structure for an earthquake-resistant and wind-resistant steel building, in which thin and lightweight shaped steel is used as frame members or others, capable of effectively solving the above-mentioned problems. That is, the present invention provides a steel reinforcing member for fastening frame members to steel sills, a joint for fastening sills and frame members forming upper and lower stories, and a steel joint structure for fastening a frame member to a steel or concrete base, which take the reinforcement strength into account with reference to the cross-sectional area of the frame member.  
      Further, the present invention provides a bolt joint structure, for a roof truss or others, capable of readily corresponding to the change of the roof inclination, easily forming the truss even if a dimensional error exists, and facilitating the working efficiency due to the improvement in the building construction.  
      To achieve the above object, the present invention is:  
      1. A joint structure of a building using thin and lightweight shaped-steel, characterized in that, in a joint portion for fastening a steel frame member for forming a wall to a steel floor sill, a steel reinforcing member having a cross-sectional area in a range from 70 to 100% of a cross-sectional area of the steel frame member is inserted into the joint portion and fixed thereto.  
      2. A joint structure of a building using thin and lightweight shaped-steel, characterized in that, in a joint portion for fastening a steel frame member for forming a wall to a steel or concrete base by a bolt, a steel joint plate provided with a bolt through-hole having a diameter 1.5 times that of the bolt or more is inserted into the joint portion and fixed thereto.  
      3. A joint structure of a building using thin and lightweight shaped-steel as defined by claim  2 , characterized in that an additional plate with a bolt through-hole having the same diameter as that of the bolt through-hole of the steel joint member or a diameter slightly larger than the bolt diameter is combined with the steel joint member.  
      4. A joint structure of a building using thin and lightweight shaped-steel, characterized in that upper chord members, lower chord members and lattice members of thin and lightweight shaped-steel are combined to form a truss structure, wherein a joint portion of the upper chord member, lower chord member and lattice member has at least one joint through-hole, and wherein the joint portions of the respective members are connected together to form a joint and a fastener is inserted into the joint through-hole to fasten and fix the respective members to each other.  
      5. A joint structure of a building using thin and lightweight shaped-steel, as defined by claim  4 , characterized in that a joint gusset in which at least one joint through-hole is provided to be aligned with the joint through-holes provided in the upper chord member, lower chord member and lattice member is attached to the joint portion and then the respective members are fastened and fixed together.  
      6. A joint structure of a building using thin and lightweight shaped-steel, as defined by claim  5 , characterized in that the gusset is a washer having a thickness of  1 . 6  mm or more.  
      7. A steel house made of thin and lightweight shaped-steel, using the joint structure as defined by any one of claims  1  to  6 . 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  illustrates a joint structure between a vertical frame member and a steel sill in the prior art;  
       FIG. 2  illustrates a joint structure between a vertical frame member and a base in the prior art;  
       FIG. 3  illustrates a joint structure between a vertical frame member and a steel sill according to the present invention;  
       FIG. 4  illustrates a joint structure between a vertical frame member and a base according to the present invention and  
       FIG. 5  illustrates a joint structure of a truss in a steel building according to the prior art and the present invention. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      An embodiment of the present invention will be described below with reference to the drawings.  
      In  FIG. 3 , a joint structure according to the present invention, for fastening and joining the respective frame members with each other, is shown. In the drawing, a frame member  1  constitutes a pillar for an upper story and a frame member  2  constitutes a pillar for a lower story, and the ends of these frame members are orthogonally joined to tracks  3  and  4  to define a T-shape. Between the tracks  3  and  4 , a sill  5  is disposed to be attached thereto, and another sill  6  is attached to the sill  5  and extends in the vertical direction. Directly above this sill  6 , a floor  7  is placed. On the opposite sides of the sill  5 , side wall members  8  are attached. Since the frame members  1  and  2  do not constitute an integral structure passing through the upper and lower stories but are assembled, a space exists between the both, in which the sills  5  and  6  are interposed. In this space, the sills  5  and  6  are orthogonally brought into contact and joined with each other at a position directly below the frame member  1  and directly above the frame member  2 . This structure is the same as that shown in  FIG. 1 .  
      The large difference from the prior art shown in  FIG. 1  is as follows. In the prior art structure, a steel member  9  formed by merely bending a flat steel sheet at a right angle is attached to the joint portion in which the sill  6  is brought into contact with the side of the sill . 6  by screws or rivets. As the steel member  9  has a cross-sectional area as small as at most 50% of the joint area for the purpose of weight reduction it is therefore insufficient in strength. Particularly, when a large earthquake occurs or a strong wind blows, a considerable force is applied to the building structure and this generates a tensile force or a compressive force in the vertical frame member to deform the sills  5  and  6 , which causes the local deformation of a floor or roof member to incline the house and deteriorate the living environment.  
      To avoid such a deficiency, according to the reinforced joint structure of the present invention, a steel reinforcing member  9 ′ having a cross-sectional area the same as or 70% or more of that of the frame member of a rectangular or groove-like shape is inserted and fixed. A concrete structure is shown in an enlarged manner in  FIG. 3  as indicated by an arrow, in which a rectangular or groove-shaped steel reinforcing member  9 ′ is attached to the joint portion, whereby the joint structure is sufficiently durable against a large earthquake of the  5 th degree or more on the seismic intensity or a typhoon of the wind velocity at 30 m/sec or more. However, if the cross-sectional area of the steel reinforcing member  9 ′ exceeds 100% of that of the frame member, the weight becomes too heavy or the joint portion is excessively strong. Thus, the cross-sectional area of the steel reinforcing member  9 ′ is preferably in a range from 70 to 100% of the cross-sectional area of the frame member. On the other hand, when the steel building of the present invention is fixed to the steel or concrete base  10 , as shown in  FIG. 4 , the bottom plate  25  constituting the joint portion for fastening the frame member  2  to the steel or concrete base  10  is provided with a bolt through-hole  27  having a diameter 1.5 times a bolt diameter or more. Also, another bolt through-hole  29  having the same diameter as the bolt is provided in an additional plate  28 . In this regard, when the diameter of the bolt through-hole provided in the bottom plate  25  is 1.5 times the bolt diameter or more, for example, when the diameter of the bolt through-hole is 24 mm or more for the bolt diameter of 16 mm, or 28.8 mm or more for the bolt diameter of 19 mm, the error of the building construction will be absorbed. On the contrary, if the diameter of the bolt through-hole is excessively large, the strength is of course unfavorably lowered.  
      As shown in  FIG. 5 ( b ), according to the roof structure of the present invention, a truss structure is assembled by joining upper chord members  50 ,  51  and opposite ends of a lower chord member  52  with ends of the upper chord members  50 ,  51 , each of which members is made of a shaped steel, 2.3 mm thick or less. If necessary, a slanted lattice member  53  is attached thereto. At least one fastener hole  55  is bored in the tip end joining portions of the upper chord member  50  in advance, the lower chord member  52  and the lattice member  53 . The joint portions of the respective members are stacked on each other to form a connecting joint portion  56 , and fasteners  57  such as connecting bolts are inserted into the fastener holes  55  to fasten and join the respective members. Thus, the truss structure is obtained. Further, in the joint portion of the upper chord members  50 ,  51 , the lower chord member  52  and the lattice member  53 , a gusset  56 , preferably a steel member of 1.6 mm thick or more, having at least one fastener hole capable of being joined by a connecting bolt, is located in alignment with a pilot hole provided in advance, and is fastened and fixed to form a truss structure. In this regard, the fastener through-hole in the steel member or the washer has a diameter larger than that of a bolt head in view of the increase in strength.  
      According to the roof structure for the building of the present invention described above, as the members to be joined are accurately located by only positioning the through-holes, it is possible to facilitate the assembling operation in situ to a great extent. Also, as the members are simply connectable together by a single bolt instead of using several screws in the prior art, the joining operation is significantly improved.  
      The present invention is advantageously applicable to a steel house as an earthquake-resistant and wind-resistant building.  
     CAPABILITY OF EXPLOITATION IN INDUSTRY  
      As described hereinabove, the present invention provides a joint structure for a building using thin and lightweight shaped steel members, particularly a joint structure for fastening frame members and steel sills of a building in which thin and lightweight shaped steel is used as the frame members or others and a joint truss structure which is a main structure of a roof. This structure provides a steel building resistant to a large earthquake and a strong wind such as a typhoon. According to the present invention, the workability is also improved to a large extent.