Patent Publication Number: US-2019195255-A1

Title: Accessory attachment structure for steel plate-reinforced concrete structure, design system and design method of steel plate-reinforced concrete structure, consruction method of steel plate-reinforced concrete structure, and steel plate-reinforced concrete structure

Description:
TECHNICAL FIELD 
     The present invention relates to an accessory attachment structure which attaches an accessory such as a support for supporting a long object, for example, piping, a duct, a cable tray and an electrical wire conductor to a steel plate-reinforced concrete structure (hereinafter, referred to as an SC structure) in which concrete is surrounded by a plurality of outside steel plates, a plurality of bars are disposed inside the concrete and also fixed on the outside steel plate. 
     The present invention also relates to a design system and a design method of an SC structure, a construction method of an SC structure and an SC structure. 
     The present application claims the right of priority to Japanese Patent Application No. 2010-213808 filed on Sep. 24, 2010, in Japan, Japanese Patent Application No. 2010-235468 filed on Oct. 20, 2010, in Japan, Japanese Patent Application No. 2010-280561 filed on Dec. 16, 2010, in Japan, Japanese Patent Application No. 2011-040004 filed on Feb. 25, 2011, in Japan, Japanese Patent Application No. 2011-040006 filed on Feb. 25, 2011, in Japan, Japanese Patent Application No. 2011-040007 filed on Feb. 25, 2011, in Japan, and Japanese Patent Application No. 2011-040009 filed on Feb. 25, 2011, in Japan, with the contents cited herewith. 
     BACKGROUND ART 
     A reinforced concrete structure (hereinafter, referred to as an RC structure) in which reinforcing steel is used as a tension member is known as a general concrete structure. In recent years, attention has been given to a steel plate-reinforced concrete structure which uses steel plates as the tension members, in addition to the RC structure. 
     The SC structure is described, for example, in Patent Document 1 and Patent Document 2. The SC structure includes a steel plate frame formed with a plurality of outside steel plates, a tie bar which connects a plurality of outside steel plates with each other, a stud fixed on an inner face of each outside steel plate, and concrete installed inside the steel plate frame. 
     The SC structure is advantageous over the RC structure in the following points of (1) to (3). 
     (1) Reduction in Construction Schedule 
     Outside steel plates used in the SC structure also function as a frame for installing concrete, thereby eliminating the need for reinforcement work and frame work as required in the RC structure. Therefore, site work is drastically reduced to shorten the construction schedule. 
     (2) Reduction of Adverse Effects on Environment 
     Since outside steel plates used in the SC structure also function as a frame and ultimately remain in the structure, thus eliminates the need for discarding the frame as required in the RC structure. Therefore, it is possible to reduce waste and lower adverse effects on the environment. 
     (3) Improvement in Attachment and Construction Properties of Accessory 
     In the RC structure, on attachment of an accessory such as a support for supporting piping to the RC structure, a bolt or the like is disposed at a predetermined attachment position of the accessory and concrete is thereafter installed. After the concrete is hardened, the accessory is connected to a part of the bolt which protrudes from a wall surface of the RC structure. In contrast, in the SC structure, an accessory can be directly joined on an outside steel plate by welding and others. Therefore, it is not necessary to determine in advance an attachment position of the accessory. Further, the accessory can be attached, irrespective of concrete hardening time. Thus, in the SC structure, it is possible to freely decide timing of attaching the accessory and an attachment position thereof and also improve the attachment and construction properties of the accessory. 
     Further, a general method for reinforcing an anchorage zone of an accessory includes a method for welding a reinforcing member consisting of a steel member at an appropriate site of the anchorage zone for reinforcement and a method for fixing a reinforcing member through bolt holes, as disclosed in Patent Document 2. Specifically, in Patent Document 2, a metal plate unit is formed in advance in which a duct for electrical wiring is attached inside one metal plate in a pair of metal plates disposed so as to be opposed to each other, and concrete is installed inside the metal plate unit. In this case, the pair of metal plates are connected with a tie bar installed therebetween. Further, a stud for reinforcement is installed so as to protrude on an inner face of the pair of the metal plates. This stud is embedded into the concrete, thereby preventing the metal plate from peeling off from the concrete. 
     Still further, for example, as shown in Patent Document 2 and Patent Document 3, the SC structure is constituted with a steel plate frame which is formed with a plurality of outside steel plates, a tie bar which connects a plurality of outside steel plates together, a stud which is fixedly installed on an inner face of each outside steel plate, and concrete which is installed inside the steel plate frame. 
     In designing the above-described SC structure, as a failure mode of a stud  902  embedded into concrete  901 , evaluation is made for two types of failure mode, that is, cone failure which is carried out at an angle of 45° at the center of the stud shown in  FIG. 26( a )  and  FIG. 26( b )  and steel member failure (stud breakage). In this evaluation, in a currently available method for evaluating the load-bearing capacity (strength) of the stud in cone failure, the load-bearing capacity of one stud  902  is in general evaluated on the basis of the following formula (1). Here, in  FIG. 26( b )  and in the formula (1), Le is the embedded depth of stud; D, the diameter of stud; φ, the reduction coefficient (safety coefficient); Ac, the projection area; and Fc, the concrete strength. 
       [Formula 1] 
         F=ϕ×Ac ×√{square root over ( Fc )}  (1)
 
     As shown in the above-described formula (1), the load-bearing capacity of the stud  902  in cone failure depends on the projection area Ac. As shown in  FIG. 27( a ) , where one stud  902  is provided, a circular area having the embedded depth of Le as a radius is given as an effective projection area Ac. As shown in  FIG. 27( b ) , where a plurality of studs  902  are disposed in a group and also an interval between the studs  902  is narrow and a circular area having the embedded depth of Le as a radius of each of the studs  902  is overlapped with another, a rectangular area in which an interval between mutually adjacent studs  902  is given as one side is given as an effective projection area Ac. As shown in  FIG. 27( c ) , where the plurality of studs  902  are disposed in a group but an interval between the studs  902  is sufficiently wide, a circular area having the embedded depth of Le as a radius is given as an effective projection area Ac. In addition, where the studs  902  are disposed in a group so that the effective projection areas Ac are overlapped with each other and a pull-out load is applied uniformly (uniform loading condition), a large effective projection area Ac is set to evaluate the load-bearing capacity of the stud in cone failure as shown in  FIG. 27( d ) . 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         
           
             Patent Document 1: Japanese Patent Application, First Publication No. 2001-248246 
             Patent Document 2: Japanese Patent Application, First Publication No. 2003-328433 
             Patent Document 3: Japanese Patent Application, First Publication No. 2007-169968 
           
         
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     As so far described, the SC structure is advantageous in having a high degree of freedom in terms of attachment of an accessory. However, depending on an attachment position of the accessory, a load applied to each one of the studs (and tie bar) will vary, by which it is necessary to decide the attachment position of the accessory so as to be in alignment with a position of the stud. 
     For example, as shown in  FIG. 39( a ) , where an accessory  803  such as a piping support is joined to an outside steel plate  805  so as to be positioned at the center of four studs  804 , these four studs  804  receive a tension load, etc., from the accessory  803 . As shown in  FIG. 39( b ) , where the accessory is joined between two studs  804 , these two studs receive a tension load, etc., from the accessory  803 . As shown in  FIG. 39( c ) , where the accessory is joined directly to one stud  804 , one stud  804  receives a tension load, etc., from the accessory  803 . Therefore, the stud  804  varies in load bearing depending on an attachment position of the accessory  803 , thus resulting in a different load being applied to each one of the studs. Therefore, where an SC structure  801  receives a great load, it is necessary to attach and construct the accessory  803  in such a manner that the accessory  803  is not joined to a position directly on one stud  804  for the purpose of reducing a load applied to each one of the studs. As a result, there is a restriction on an attachment position of the accessory  803 . Further, where the accessory is attached to any given place on an outside steel plate, it is necessary to keep a load applied to the SC structure  801  down to an allowable load which can be received by one stud  804 . 
     The present invention has been made in view of the above-described problems, a first object of which is to provide an accessory attachment structure which is capable of attaching an accessory to any given position even where an SC structure receives a great load of the accessory. 
     Further, in the SC structure, as described above, a load applied to each one of the studs or each one of the tie bars will vary depending on an attachment position of the accessory. It is therefore necessary to decide the attachment position of the accessory so as to be in alignment with a position of the stud or the tie bar. 
     However, since the stud  804  is disposed on an inner face  805   a  of the outside steel plate  805  (inner face of the steel plate frame  806 ) and also embedded into concrete  807 , it is difficult to locate the position of the stud. Therefore, on attachment of the accessory  803 , the position of the stud  804  needs to be confirmed by referring to a design drawing or the like, which requires time for construction. Time is also required in designing the attachment position of the accessory  803 . 
     Therefore, the present invention has been made in view of the above-described problem, a second object of which is to provide an accessory attachment structure which makes it possible to easily decide an attachment position of an accessory. 
     Further, a third object of the present invention is to provide an accessory attachment structure which is increased in rigidity by a simple and lightweight structure and in which an accessory can be attached on confirmation of the strength of an attachment position of the accessory. 
     Still further, in a conventional method of designing the SC structure, as shown in  FIG. 27( b ) , where a great pull-out load is applied to one stud  902  at the center in a state that a uniform load is applied to the studs  902  disposed in a group, an effective projection area Ac is made smaller than a case shown in  FIG. 27( a )  where one stud  902  is pulled out. As a result, the load-bearing capacity is evaluated to be smaller in cone failure. That is, in a conventional method for designing the SC structure, on the evaluation, no consideration is given to the pull-out capacity associated with pulling out of the stud  902  in a case where a body load (a load conceivable in design such as its own weight of the SC structure and seismic load other than a load of an accessory) is applied to the SC structure in which the studs  902  are disposed in a group. 
     Therefore, a fourth object of the present invention is to provide a design system of an SC structure and a design method of an SC structure in which a stud can be rationally evaluated for load-bearing capacity thereof by reviewing a method for determining an effective projection area in cone failure for a conventional design method of an SC structure. 
     Further, a fifth object of the present invention is to provide an SC structure in which a stud can be rationally evaluated for the load-bearing capacity thereof, as compared with a case in which a plurality of studs are disposed so as to be arranged vertically and transversely (a case where they are arranged in a lattice form). 
     Still further, a sixth object of the present invention is to provide a construction method of an SC structure and an SC structure which are capable of attaching and constructing an accessory, with a load applied to each one of the studs reliably kept low, and also capable of shortening the time necessary for constructing the accessory and time necessary for designing an attachment position of the accessory, as compared with a conventional case. 
     In addition, in a conventional SC structure, a stud is joined to an inner face of an outside steel plate by fillet welding. Construction of the stud by welding partially contributes to an increase in construction man-hours and also an increase in construction costs. 
     Therefore, a seventh object of the present invention is to provide an SC structure which is capable of reducing man-hours on construction of a stud and construction costs and also capable of reducing the time necessary for constructing an accessory and time necessary for designing an attachment position of the accessory. 
     Means for Solving the Problems 
     In order to attain the above-described first object, the accessory attachment structure of the present invention is an accessory attachment structure for attaching an accessory to an SC structure which is provided with a steel plate frame formed with a plurality of outside steel plates, a plurality of bars fixedly installed on an inner face of the outside steel plate, and concrete installed inside the steel plate frame. The accessory attachment structure is provided with an attachment plate in which one face thereof is attached to the outside steel plate and the accessory is attached to the other face thereof, the size of the other face of the attachment plate is larger than that of a whole attachment face to be attached to the attachment plate of the accessory, and the size of the one face of the attachment plate is equal to or greater than the other face. And, the length of the attachment plate in any direction along the one face of the attachment plate is at least two times greater than a mutual interval between the plurality of bars. 
     According to the present invention, on attachment of an attachment plate to any position of the outside steel plate, at least two bars are to be present in a region where the attachment plate is attached. Therefore, in the attachment structure, where the accessory is disposed at any position of the outside steel plate, tension load, etc., from the accessory can be received by two or more bars. In other words, it is possible to reduce a bearing load received by each one of the bars. Thus, according to the attachment structure, even where the SC structure receives a relatively great load of the accessory, it is possible to attach the accessory to any given position. 
     In the accessory attachment structure, it is acceptable that a plurality of the accessories be attached to the attachment plate and the size of the other face of the attachment plate be larger than that of attachment faces of each of the plurality of accessories where the plurality of accessories are attached to the attachment plate. 
     In this case, the attachment plate can be reduced in the number thereof in relation to a plurality of accessories and thereby man-hours on attachment can also be reduced. Further, in the attachment structure, the attachment plate can be further increased in area of one face per accessory, as compared with a case where the attachment plate is installed for each of the plurality of accessories. It is thus possible to further increase the load of the accessory received by the SC structure. 
     In the accessory attachment structure, it is acceptable that the accessory be provided with the plurality of attachment faces which are spaced apart from each other, and the size of the other face of the attachment plate be larger than that of the plurality of attachment faces of the accessory where the accessory is attached to the attachment plate. 
     In this case, as with the above-described attachment structure, it is possible to reduce the number of attachment plates in relation to a plurality of attachment faces of the accessory. Thereby, man-hours on attachment can be reduced. Further, in the attachment structure, the attachment plate can be increased in area of one face per attachment face of the accessory, as compared with a case where the attachment plate is installed for each of a plurality of attachment faces. It is therefore possible to increase the load of the accessory received by the SC structure. 
     In the above-described accessory attachment structure, it is acceptable that the attachment plate be gradually decreased in area of a cross-section perpendicular to a direction from the one face to the other face in moving along the direction. Further, in the accessory attachment structure, it is also acceptable that the attachment plate be provided with a plurality of plates which are stacked in a direction from the one face to the other face and also joined together, and the plurality of plates be such that a plate on the other face is smaller in area of a cross-section perpendicular to the above-described direction than a plate on the one face. 
     In this case, where the other face of the attachment plate is made smaller in area than the one face thereof, it is possible to reduce the weight of the attachment plate without reducing the load of the accessory received by the SC structure. 
     In the above-described accessory attachment structure, it is acceptable that the attachment plate be joined to the outside steel plate by welding. 
     In the attachment structure, the accessory can be attached to any given position on the outside steel plate without installing in advance a bolt or the like on the outside steel plate. 
     In order to attain the above-described second object, the accessory attachment structure of the present invention is an accessory attachment structure for attaching an accessory to an SC structure which is provided with a steel plate frame formed with a plurality of outside steel plates, concrete installed inside the steel plate frame, and a plurality of tie bars passing through the outside steel plate and the concrete. The accessory attachment structure is provided with an attachment plate in which one face thereof is attached to an outer face of the outside steel plate and the accessory is attached to the other face thereof, and an external thread portion or an internal thread portion which is exposed on an outer face of the outside steel plate, and provided with the tie bar. The attachment plate is fastened and fixed to the outside steel plate by a nut or a bolt which is screwed into the external thread portion or the internal thread portion of at least one of the plurality of tie bars. 
     The present invention is a structure such that the attachment plate is directly fixed to the tie bar. Therefore, stress resulting from a load of the accessory can be applied to the tie bar via the attachment plate. Further, an end of the tie bar is exposed and the external thread portion which is screwed into a nut is installed at the end. And, the attachment plate can be attached to any given tie bar after visual observation is made for a site at which the tie bar is installed. Therefore, on attachment of the accessory, it is possible to easily decide an attachment position and also reduce a load received by each one of the tie bars. 
     The accessory attachment structure may be such that both ends of the tie bar are screwed into the outside steel plate and integrally joined to the attachment plate. 
     In this case, since a welding process is not required, it is possible to construct the SC structure easily. 
     In order to attain the above-described third object, the accessory attachment structure of the present invention is an accessory attachment structure in which a support member is attached via an attachment plate to the surface of an SC structure to which concrete is installed between a pair of outside steel plates opposed to each other at a predetermined interval. The pair of outside steel plates are connected only by a tie bar, the both ends of which are fixed to each of the outside steel plates, and the attachment plate is attached to a region to which at least a plurality of the tie bars are attached. 
     According to the present invention, the attachment plate of the support member can be attached after confirmation of the presence of the tie bar. It is therefore possible to easily disperse a load of the attachment plate to the plurality of tie bars substantially in a uniform manner. 
     The accessory attachment structure may be such that on the inner face of the outside steel plate, a rib extending along the inner face thereof is fixed. 
     In this case, unlike narrow and exact reinforcement by using a tie bar or a stud, a plurality of ribs are used to realize at least linear reinforcement. Thus, it is possible to efficiently disperse the load on installation of the attachment plate. 
     The accessory attachment structure may be such that an inner steel plate parallel to the outside steel plate is fixed to the leading end of the rib. 
     In this case, it is possible to secure a greater strength. In this case, it is preferable that consideration be given to positions of the inner steel plate so as to be along the rib in such a manner that concrete can be evenly installed between the outside steel plates without preventing the influx of ready-mixed concrete on installing the concrete. 
     The accessory attachment structure may be such that the rib arranges a plurality of flat plate members in a lattice form. 
     In this case, the flat plate members are arranged in a lattice form to constitute the rib, thus making it possible to improve the strength of the rib to a greater extent. Further, the rib is less likely to prevent the influx of ready-mixed concrete. 
     The accessory attachment structure may be such that the rib arranges a plurality of angle bars, each of which has an approximately L-shaped cross-section, in a lattice form. 
     In this case, one side of an approximately L-shaped cross-section is allowed to come into contact with the outside steel plate and be fixed. Thereby, the rib can be fixed to the outside steel plate simply and rigidly. 
     The accessory attachment structure may be such that the rib arranges a plurality of channel bars, each of which has an approximately C-shaped cross-section, in a lattice form. 
     In this case, one side of the channel bar is allowed to come into contact with the outside steel plate and be fixed. Thereby, the rib can be fixed to the outside steel plate simply and rigidly. 
     In order to attain the above-described fourth object, the design system of the SC structure of the present invention is a design system of an SC structure which is provided with a steel plate frame formed with a plurality of outside steel plates, a stud fixedly installed on an inner face of the outside steel plate, and concrete installed inside the steel plate frame. The design system of the SC structure is provided with a structure condition input device which inputs structure conditions including a stud interval and a stud length, a body load-calculating device which calculates a body load on the basis of the structure conditions input by the structure condition input device, a reference load-calculating device which calculates a reference load which can be supported by each one of the studs where supported by a plurality of studs as a whole, a load ratio-calculating device which calculates a load ratio of body load to reference load, a storage device which stores a relationship between the load ratio and an effective projection area, an effective projection area-calculating device which calculates the effective projection area from the load ratio by referring to a relationship between the load ratio and the effective projection area stored by the storage device, and an load-calculating device which calculates a load including an accessory load which can be supported by one stud on the basis of the effective projection area calculated by the effective projection area-calculating device. 
     The design method of the SC structure of the present invention is a design method of an SC structure which is provided with a steel plate frame formed with a plurality of outside steel plates, a stud fixedly installed on an inner face of the outside steel plate, and concrete installed inside the steel plate frame. The design method includes: calculating a body load which is determined on the basis of structure conditions including a stud interval and a stud length; calculating a reference load which can be supported by each one of the studs is determined where the load is supported by the plurality of studs as a whole; calculating a load ratio of body load to reference load which is determined; calculating an effective projection area which is determined from the load ratio by referring to a relationship between a predetermined load ratio and the effective projection area; and calculating a load including an accessory load which can be supported by each one of the studs is determined on the basis of the thus determined effective projection area. 
     In order to attain the above-described fifth object, the SC structure of the present invention is an SC structure which is provided with a steel plate frame formed with a plurality of outside steel plates, a plurality of studs fixedly installed on an inner face of the outside steel plate and concrete installed inside the steel plate frame, in which the plurality of studs are arranged in a zigzag form. 
     In order to attain the above-described sixth object, the construction method of the SC structure of the present invention is a construction method of an SC structure which is provided with a steel plate frame formed with a plurality of outside steel plates, a stud installed in a protruded manner from an inner face of the outside steel plate to the inside of the steel plate frame, concrete installed inside the steel plate frame, and an attachment device installed on an outer face of the outside steel plate to attach an accessory. The construction method includes: a stud-attaching step in which fixedly installed the stud on the inner face of the outside steel plate; an attachment device-preparing step in which disposed at least apart of the attachment device at a plurality of attachment positions on the outer face of the outside steel plate to which the accessory is attached via the attachment device; a steel plate-installing step in which disposed the outside steel plate at a predetermined position to form the steel plate frame; a concrete-installing step in which installed concrete into the steel plate frame; and an accessory-installing step in which installed the accessory. 
     According to the present invention, in the attachment device-preparing step, at least a part of the attachment device is disposed at a plurality of attachment positions on the outer face of the outside steel plate to which an accessory can be attached. It is therefore possible to easily confirm a position of the stud and dispose at least a part of the attachment device. Next, in the accessory-installing step, the accessory is attached and installed on the attachment device, by which the accessory can be attached and constructed in a state that a load received by each one of the studs is reliably kept low. 
     The SC structure of the present invention is an SC structure which is provided with a steel plate frame formed with a plurality of outside steel plates, a stud installed in a protruded manner from an inner face of the outside steel plate to the inside of the steel plate frame, concrete installed inside the steel plate frame, and an attachment device which is installed on an outer face of the outside steel plate to attach the accessory. The attachment device is provided with an attachment plate which attaches and supports the accessory and a locking portion which is installed at a plurality of attachment positions on an outer face of the outside steel plate to which the accessory can be attached. And, the attachment device is constituted in such a manner that the attachment plate can be selectively locked to any of the locking portions installed at the attachment positions and be fixed accordingly. 
     According to the present invention, since the attachment plate is selectively locked to any of the locking portions installed at a plurality of attachment positions on the outer face of the outside steel plate to which an accessory can be attached, it is possible to attach the accessory via the attachment plate to the outer face of the outside steel plate. Accordingly, a simple operation is employed in which a plurality of attachment positions are set so as to keep low a load received by each one of the studs and the attachment plate is locked to the locking portion of the attachment device installed at the attachment position, thereby reliably attaching and constructing the accessory in a state that the load received by each one of the studs is kept low. Further, at this time, a main body thereof can be selectively locked to any of the plurality of locking portions. It is therefore possible to attach the attachment plate and also the accessory to any given attachment position. 
     In order to attain the above-described seventh object, the SC structure of the present invention is an SC structure which is provided with a steel plate frame formed with a plurality of outside steel plates, a stud which is fixed to the outside steel plate and installed in a protruded manner to the inside of the steel plate frame, and concrete installed inside the steel plate frame, in which a through-hole is formed on the outside steel plate so as to pass through from the inner face of the outside steel plate to the outer face, a shaft portion of the stud is inserted to the through-hole, and the stud is fixed to the outside steel plate so that the outside steel plate is held between a pair of holding portions integrally formed on the shaft portion. 
     Effects of the Invention 
     According to the accessory attachment structure of the present invention, it is possible to reduce a load received by each one of the bars. Thus, the accessory can be attached to any given position even where a load of the accessory received by the SC structure is relatively great. 
     Further, according to the accessory attachment structure of the present invention, stress resulting from a load of the accessory is allowed to act on a tie bar via the attachment plate. Still further, according to the accessory attachment structure of the present invention, it is possible to easily decide an attachment position on attachment of the accessory and also reduce a load received by each one of the tie bars. 
     Further, according to the accessory attachment structure of the present invention, it is possible to increase rigidity by a simple and lightweight structure and also attach an accessory after confirmation is made for the strength of an attachment position of the accessory. 
     According to the design system of the SC structure and the design method of the SC structure of the present invention, a stud can be rationally evaluated for load-bearing capacity thereof by reviewing a method for determining an effective projection area in cone failure for a conventional design method of an SC structure. 
     According to the SC structure of the present invention, a plurality of studs are disposed so as to be arranged in a zigzag form, thus making it possible to evaluate each stud as an individually independent stud. Further, according to the SC structure of the present invention, the stud can be evaluated rationally for load-bearing capacity thereof, as compared with a case where a plurality of studs are disposed so as to be arranged vertically and transversely (arranged in a lattice form). 
     According to the construction method of the SC structure and the SC structure of the present invention, a plurality of attachment positions are set so as to keep low a load received by each one of the studs, while a position of the stud is confirmed easily, and an accessory can be attached to the attachment position. Thereby, the accessory can be attached and constructed, with a load received by each one of the studs reliably kept low. It is also possible to reduce the time necessary for constructing the accessory and time necessary for designing an attachment position of the accessory, as compared with a conventional case. 
     According to the SC structure of the present invention, of the pair of holding portions, one of them is disposed on an outer face of the outside steel plate. Therefore, on attachment of an accessory, a position of the stud can be located from outside of the outside steel plate. Thereby, it is possible to reduce the time necessary for constructing the accessory and time necessary for designing an attachment position of the accessory. 
     Further, the stud is attached to the outside steel plate by using a rivet structure, a bolt and a nut, by which man-hours for constructing the stud can be reduced to attain reduction of construction costs, as compared with a case where the stud is fixed to the outside steel plate by a conventional welding. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an SC structure and an attachment structure of a First Embodiment of the present invention, in which (a) is a sectional view of the SC structure and the attachment structure and (b) is a front view of the SC structure and the attachment structure. 
         FIG. 2  shows an SC structure and an attachment structure of a Second Embodiment of the present invention, in which (a) is a sectional view of the SC structure and the attachment structure and (b) is a front view of the SC structure and the attachment structure. 
         FIG. 3  shows an SC structure and an attachment structure of a Third Embodiment of the present invention, in which (a) is a sectional view of the SC structure and the attachment structure and (b) is a front view of the SC structure and the attachment structure. 
         FIG. 4  shows an SC structure and an attachment structure of a modified example of the Third Embodiment of the present invention, in which (a) is a sectional view of the SC structure and the attachment structure and (b) is a front view of the SC structure and the attachment structure. 
         FIG. 5  is a front view of an SC structure and an attachment structure of a First Modified Example of each embodiment of the present invention. 
         FIG. 6  shows an SC structure and an attachment structure of a Second Modified Example of each embodiment of the present invention, in which (a) is a sectional view of the SC structure and the attachment structure and (b) is a front view of the SC structure and the attachment structure. 
         FIG. 7  shows an SC structure and an attachment structure of another modified example of the above Second Modified Example, in which (a) is a sectional view of the SC structure and the attachment structure and (b) is a front view of the SC structure and the attachment structure. 
         FIG. 8  shows an accessory attachment structure of a Fourth Embodiment of the present invention, in which (a) is a sectional view thereof and (b) is a front view thereof. 
         FIG. 9  is an enlarged view of the sectional view of  FIG. 8 . 
         FIG. 10  shows an accessory attachment structure of a Fifth Embodiment of the present invention, in which (a) is a sectional view thereof and (b) is a front view thereof. 
         FIG. 11  is an enlarged view of the sectional view of  FIG. 10 . 
         FIG. 12  shows an accessory attachment structure of a Sixth Embodiment of the present invention, in which (a) is a sectional view thereof and (b) is a front view thereof. 
         FIG. 13  is an enlarged view of the sectional view of  FIG. 12 . 
         FIG. 14  is a detailed view which shows a tie bar of the Sixth Embodiment. 
         FIG. 15  is a detailed view which shows a tie bar of a Seventh Embodiment. 
         FIG. 16  shows an accessory attachment structure  310 A of an Eighth Embodiment of the present invention, in which (a) is a front view of major parts and (b) is a longitudinal sectional view of the major parts. 
         FIG. 17  shows an accessory attachment structure  310 B of a Ninth Embodiment of the present invention, in which (a) is a front view of major parts and (b) is a longitudinal sectional view of the majors part taken along the line of  2 B to  2 B in (a). 
         FIG. 18  shows an accessory attachment structure  310 C of a Tenth Embodiment of the present invention, in which (a) is a front view (partially broken) of major parts and (b) is a longitudinal sectional view of the major parts taken along the line of  3 B to  3 B in (a). 
         FIG. 19  shows an accessory attachment structure  310 D of an Eleventh Embodiment of the present invention, in which (a) is a front view (partially broken) of major parts and (b) is a longitudinal sectional view of the major parts taken along the line of  4 B to  4 B in (a). 
         FIG. 20  is a sectional view which shows an SC structure of a Twelfth Embodiment of the present invention. 
         FIG. 21  shows a schematic view which shows studs disposed in the SC structure of the Twelfth Embodiment of the present invention, in which (a) is a front elevational view thereof and (b) is a plane cross-sectional view thereof. 
         FIG. 22  is a block diagram which shows a design system of the SC structure of the Twelfth Embodiment of the present invention. 
         FIG. 23  is a drawing which shows how to determine an effective projection area in the design method of the SC structure of the Twelfth Embodiment of the present invention. 
         FIG. 24  is a graph which shows one example of a relationship between a load ratio and an effective projection area in the design method of the SC structure of the Twelfth Embodiment of the present invention. 
         FIG. 25  is a graph which shows an example of a relationship between the load ratio and the load-bearing capacity of a stud in the design method of the SC structure of the Twelfth Embodiment of the present invention. 
         FIG. 26  is a drawing which shows cone failure of a stud in the SC structure. 
         FIG. 27  is a drawing which shows how to determine an effective projection area in a conventional design method of the SC structure. 
         FIG. 28  is a sectional view which shows an SC structure of the Thirteenth Embodiment of the present invention. 
         FIG. 29  is a plan view which shows a plurality of studs disposed in a zigzag form in the SC structure of the Thirteenth Embodiment of the present invention. 
         FIG. 30  is a sectional view which shows a stud of an SC structure of the Thirteenth Embodiment of the present invention. 
         FIG. 31  is a drawing which shows a difference in load transfer to the SC structure of the Thirteenth Embodiment of the present invention, depending on an attachment position of an accessory (attachment plate). 
         FIG. 32  is a drawing which shows a modified example where studs of the SC structure of the Thirteenth Embodiment of the present invention are disposed. 
         FIG. 33  is a sectional view which shows schematically the SC structure of the Thirteenth Embodiment of the present invention. 
         FIG. 34  is a sectional view which shows an SC structure of a Fourteenth Embodiment of the present invention. 
         FIG. 35  is a sectional view which shows the SC structure of the Fourteenth Embodiment of the present invention. 
         FIG. 36  is an arrow view taken along the arrow of X 1  to X 1  shown in  FIG. 35  or a front elevational view which shows the SC structure of the Fourteenth Embodiment of the present invention. 
         FIG. 37  is a sectional view which shows a modified example of the SC structure of the Fourteenth Embodiment of the present invention. 
         FIG. 38  is an arrow view taken along the arrow of X 1  to X 1  shown in  FIG. 37  or a front elevational view which shows a modified example of the SC structure of the Fourteenth Embodiment of the present invention. 
         FIG. 39  is a drawing which describes a difference in attachment position of an accessory. 
         FIG. 40  is a sectional view which shows an SC structure of the Fifteenth Embodiment or Sixteenth Embodiment of the present invention. 
         FIG. 41  is a drawing which shows studs used in the SC structure of Fifteenth Embodiment of the present invention. 
         FIG. 42  is a drawing which shows one example of an AR machine used in constructing a stud used in the SC structure of Fifteenth Embodiment of the present invention. 
         FIG. 43  is a drawing which shows one example of procedures in which the stud used in the SC structure of the Fifteenth Embodiment of the present invention is constructed by using an AR machine. 
         FIG. 44  is a drawing which shows a stud used in the SC structure of a Sixteenth Embodiment of the present invention. 
         FIG. 45  is a drawing which shows a modified example of the SC structure (stud) of the Fifteenth Embodiment or Sixteenth Embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a description will be given of individual embodiments of the accessory attachment structure of the present invention by referring to drawings. 
     First, a description will be given of an accessory and an SC structure (steel plate-reinforced concrete structure) to which the accessory is attached, prior to a description of an accessory attachment structure. 
     As shown in  FIG. 1 , the accessory is, for example, a piping support  20 . This piping support  20  is formed with one H-steel member. The H-steel member is available in size, for example, 100 (H)×100 (B). In the present invention, the accessory is not necessarily a piping support and fundamentally includes anything such as a support of ducts and a rack. 
     As shown in  FIG. 1 , an SC structure  10  is provided with a plurality of outside steel plates  11  which forms a steel plate frame, a plurality of bars  12  disposed into the steel plate frame and fixed to the steel plate frame, and concrete  15  installed inside the steel plate frame. The bar  12  includes a tie bar  13  for connecting a pair of outside steel plates  11  which are opposed to each other in a plurality of outside steel plates  11  which form the steel plate frame and a stud  14  for increasing connection of the outside steel plate  11  with the concrete  15 . The tie bar  13  is provided such that one end thereof is joined to one outside steel plate  11  of the pair of outside steel plates  11  and the other end thereof is joined to the other outside steel plate  11 . Further, only one end of the stud  14  is fixed to the outside steel plate  11 . 
     Here, for convenience of the following description, of the pair of outside steel plates  11 , a direction from the one outside steel plate  11  to the other outside steel plate  11  is given as the Z direction, a direction perpendicular to the Z direction is given as the Y direction, a direction perpendicular to the Z direction and the Y direction is given as the X direction. The pair of outside steel plates  11  are parallel to an XY plane. 
     In the SC structure  10 , a mutual interval Ps between two studs  14  adjacent both in the X direction and the Y direction is, for example, 200 mm. A mutual interval Pt between two tie bars  13  adjacent both in the X direction and the Y direction is, for example, 600 mm. A mutual interval Pst between the stud  14  and the tie bar  13  adjacent both in the X direction and the Y direction is, for example, 200 mm. That is, in this SC structure  10 , a mutual interval P between the bars  12  in the X direction and the Y direction is 200 mm. 
     First Embodiment 
     Next, a description will be given of an accessory attachment structure of a First Embodiment of the present invention by referring to  FIG. 1 . 
     An attachment plate  30  is used when the piping support  20 , which is an accessory, is attached to the surface of an SC structure  10 , that is, an outer face  11   a  of an outside steel plate  11 . The attachment plate  30  is formed, for example, with a single steel plate such as an SS (steel structure) material and an SM (steel marine) material. 
     The attachment plate  30  is a rectangular-shaped plate, that is, 200 mm in length of the transverse direction that is equal to a mutual interval between studs and 400 mm in length of the longitudinal direction that is twice as long as the mutual interval between studs. The attachment plate  30  is such that, with the longitudinal direction kept in alignment with the Y direction, one face thereof (hereinafter, referred to as steel plate joint face  32 ) is attached to the outer face  11   a  of the outside steel plate  11  of the SC structure  10 . Further, the piping support  20 , which is an accessory, is attached to the other face of the attachment plate  30  (hereinafter, referred to as accessory joint face  31 ). 
     On attachment of the piping support  20 , first, the attachment plate  30  is joined to the piping support  20  by welding. Specifically, the accessory joint face  31  of the attachment plate  30  is allowed to come into contact with an attachment face  21  which is a face on the attachment plate  30  of the piping support  20 , by which a border portion between these faces  31  and  21  is joined together by welding. Connection of the attachment plate  30  with the piping support  20  may include any form of connection such as connection by welding, soldering and connecting fittings such as screws. As described previously, the piping support  20  is an H-steel member of 100 (H)×100 (B) mm, while the attachment plate  30  is a single steel plate (400×200 mm). Thus, there is no chance that the attachment face  21  of the piping support  20  will run off from the accessory joint face  31  of the attachment plate  30 . 
     Next, the attachment plate  30  to which the piping support  20  has been joined is joined to the outside steel plate  11  of the SC structure  10  by welding. In this case, the attachment plate  30  is disposed on the outside steel plate  11  of the SC structure  10  in such a manner that the piping support  20  which has been joined to the attachment plate  30  assumes an intended position on an XY plane by making the longitudinal direction of the attachment plate  30  in alignment with the Y direction. Next, in a state that the steel plate joint face  32  of the attachment plate  30  is in contact with the outer face  11   a  of the outside steel plate  11 , an outer-circumference edge of the steel plate joint face  32  of the attachment plate  30  is joined to the outside steel plate  11  by welding. In addition, connection of the attachment plate  30  with the outside steel plate  11  may be carried out by welding or soldering. 
     The attachment plate  30  is a steel plate with sizes 400 mm×200 mm and a maximum length thereof (400 mm) is twice as long as a mutual interval P (200 mm) of bars  12  of the SC structure  10 . Therefore, if the attachment plate  30  is attached to any position on the outer face  11   a  of the outside steel plate  11 , at least two bars  12  are present in a region where the attachment plate  30  has been attached. 
     The piping support  20  is attached, for example, at the center of the attachment plate  30  (at the center in the X direction and the Y direction). As shown in the case of a in  FIG. 1( b ) , where the piping support  20  is positioned in the X direction on a line of a certain bar  12  and positioned in the Y direction at the center of two bars  12  adjacent in the Y direction, two bars  12  are present in a region in the X direction and the Y direction where the attachment plate  30  of the piping support  20  has been attached. 
     Further, as shown in the case of b in  FIG. 1( b ) , where the piping support  20  is positioned in the X direction at the center of two bars  12  adjacent in the X direction and positioned in the Y direction on a line of a certain bar  12 , six bars  12  are present in a region in the X direction and the Y direction where the attachment plate  30  of the piping support  20  has been attached. 
     Still further, as shown in the case of c in  FIG. 1( b ) , where the piping support  20  is positioned in the X direction at the center of two bars  12  adjacent in the X direction and positioned in the Y direction at the center of two bars  12  adjacent in the Y direction, four bars  12  are present in a region in the X direction and the Y direction where the attachment plate  30  of the piping support  20  has been attached. 
     That is, in the present embodiment, even where the attachment plate  30  is attached to any position of the outside steel plate  11 , at least two bars  12  are present in a region of the attachment plate  30  in the X direction and the Y direction. Therefore, in the present embodiment, where the piping support  20  is disposed at any position on the outside steel plate  11 , it is possible to receive tension load, etc., from the piping support  20  by two or more bars  12 . In other words, it is possible to reduce a load received by each one of the bars  12 . 
     Therefore, in the present embodiment, the piping support  20  can be attached to any given position, even where the SC structure  10  receives a relatively great load from the piping support  20 . 
     Second Embodiment 
     Next, a description will be given of a Second Embodiment of an accessory attachment structure of the present invention by referring to  FIG. 2 . 
     The attachment structure of the First Embodiment is an attachment structure which is the piping support  20  with one leg. The attachment structure of the present embodiment is an attachment structure which is a piping support  22  with a plurality of legs. 
     Specifically, the piping support  22  of the present embodiment is provided with a beam  22   a  which directly supports a piping  25  and a reinforcing member  22   b  which supports the beam  22   a . The beam  22   a  is installed so as to run along the Z direction. The reinforcing member  22   b  is joined to one end of the beam  22   a  and installed obliquely relative to the beam  22   a  from there, that is, so as to run along the YZ directions. The beam  22   a  and the reinforcing member  22   b  constitute respectively the legs of the piping support  22 . Therefore, the attachment face which is a face on the attachment plate  30  of the piping support  22  is given as a face  21   a  at the other end of the beam  22   a  and also a face  21   b  at the other end of the reinforcing member  22   b.    
     The attachment plate  30  of the present embodiment is made to a size such that on attachment of the piping support  22 , these two attachment faces  21   a ,  21   b  of the piping support  22  are both placed inside an accessory joint face  31  of the attachment plate  30 , specifically, the sizes of 400 mm×200 mm. The attachment plate  30  of the present embodiment is equal in sizes (400 mm×200 mm) to the attachment plate  30  of the First Embodiment to which the piping support  20  with one leg is attached. However, where a distance between the respective attachment faces  21   a  and  21   b  of the beam  22   a  and the reinforcing member  22   b  which constitute the piping support  22  is relatively great, it is necessary to make the attachment plate  30  greater in sizes so that the two attachment faces  21   a  and  21   b  are both placed inside the accessory joint face  31  of the attachment plate  30 . 
     As described so far, in the present embodiment as well, as with the First Embodiment, the attachment plate  30  is a steel plate with sizes of 400 mm×200 mm and a maximum length (400 mm) is twice as long as a mutual interval (200 mm) between bars  12  of the SC structure  10 . It is therefore possible to attach the piping support  22  to any given position even where a load of the piping support  22  received by the SC structure  10  is relatively great. 
     Third Embodiment 
     Next, a description will be given of a Third Embodiment of an accessory attachment structure of the present invention by referring to  FIG. 3 . 
     The present embodiment relates to a plurality of accessory attachment structures, and the plurality of accessories are all piping supports  22  as with the Second Embodiment. 
     Two piping supports  22  are attached to an attachment plate  33  of the present embodiment. A mutual interval dy in the Y direction between an attachment face  21   a  of a beam  22   a  of one piping support  22  and an attachment face  21   a  of the other piping support  22  is 450 mm, and a mutual interval dx in the X direction is 400 mm. Therefore, the attachment plate  33  of the present embodiment is made to a size such that on attachment of these two piping supports  22 , the attachment faces  21   a ,  21   b  of every two piping supports  22  are both placed inside an accessory, joint face  31  of the attachment plate  33 , specifically, the sizes of 900 mm×650 mm. 
     As described so far, in the present embodiment, a steel plate joint face  32  (900 mm×650 mm) of the attachment plate  33  to which two piping supports  22  are attached is at least two times greater in area than a steel plate joint face  32  (400 mm×200 mm) of the attachment plate  30  to which one piping support  22  is attached. That is, the steel plate joint face  32  is greater in area than a case where one piping support  22  is attached. It is therefore possible to increase a load of the piping support  22  received by an SC structure  10 . Further, in the present embodiment, two piping supports  22  can be attached to the SC structure  10  by using one attachment plate  33  on attachment of two piping supports  22 , thus making it possible to reduce man-hours necessary for attachment work. 
     Incidentally, in the present embodiment, connection of the attachment plate  33  with the outside steel plate  11  is made, as with the embodiments so far described, by joining an outer-circumference edge of the steel plate joint face  32  of the attachment plate  33  to the outside steel plate  11  by welding. However, where the attachment plate  33  is relatively great in size as found in the present embodiment, it is preferable that, as shown in  FIG. 4 , the outer-circumference edge of the steel plate joint face  32  of the attachment plate  33  be joined to the outside steel plate  11  and also the steel plate joint face  32  of the attachment plate  33  be joined at several spots thereinside to the outside steel plate  11  by welding. In this case, it is acceptable that a through-hole  34  be formed in advance inside the attachment plate  33 , and this through-hole  34  be used as a welding groove to weld the outside steel plate  11  to a part of the through-hole  34  of the attachment plate  33  (welded part  34   b ) and also the outer-circumference edge of the steel plate joint face  32  of the attachment plate  33  be welded to the outside steel plate  11  (welded part  34   a ). It is also acceptable that after the outer-circumference edge of the steel plate joint face  32  of the attachment plate  33  is welded to the outside steel plate  11 , a through-hole  34  be formed inside the attachment plate  33  and the through-hole  34  be used as a welding groove to weld the outside steel plate  11  to a part of the through-hole  34  of the attachment plate  33 . 
     Next, a description will be given of various modified examples of the embodiments so far described. 
     First Modified Example 
     The attachment plates  30 ,  33  of the so far-described individual embodiments are both formed in a rectangular shape steel plate, to which the present invention shall not be, however, restricted and is fundamentally applicable to any shape. For example, as shown in  FIG. 5 , the attachment plate may be a regular tetragonal steel plate  35 , a cross-shaped steel plate  36  or a circular steel plate  37 . 
     Second Modified Example 
     In the so far-described individual embodiments, the accessory joint face  31  of the attachment plates  30 ,  33  is equal in area to the steel plate joint face  32 . However, the attachment plate of the present invention may be made to a size such that an attachment face of a piping support as a whole can be placed inside the accessory joint face and the length of the steel plate joint face in any of the directions along the steel plate joint face is at least two times greater than a mutual interval between bars  12 . Therefore, the accessory joint face may be smaller in area than the steel plate joint face. 
     For example, as shown in  FIG. 5 , a cross-sectional shape perpendicular to the X direction of the attachment plate  38  and a cross-sectional shape perpendicular to the Y direction may be formed in the shape of an isosceles trapezoid. In this case, it is acceptable that a face corresponding to an upper bottom of the isosceles trapezoid be given as an accessory joint face  31  and a face corresponding to a lower bottom of the isosceles trapezoid be given as a steel plate joint face  32 . 
     Further, as shown in  FIG. 6 , an attachment plate  40  may be formed with a plurality of steel plates  41 ,  42  which are stacked in the Z direction and joined together. In this case, it is acceptable that the steel plate  41  on the side of an accessory be made smaller than the steel plate  42  on the side of an outside steel plate  11 . It is also acceptable that in the plurality of steel plates  41 ,  42 , a face on the side of the outside steel plate  11  of the steel plate  42  which is closest to the outside steel plate  11  be given as the steel plate joint face  32  and the face of the steel plate  41  on the side of an accessory which is closest to the side of the accessory be given as the accessory joint face  31 . 
     As shown in  FIG. 7 , it is acceptable that an attachment plate  45  which is formed by stacking a plurality of steel plates  46 ,  47  be used as an attachment plate for attaching a plurality of piping supports  20 . In this case, in the plurality of steel plates  46 ,  47 , the steel plate  46  which is closest to an accessory is installed for every plurality of piping support  20  and a face of each steel plate  46  on the side of the accessory is given as an accessory joint face  31 , by which the piping support  20  is fixed to the accessory joint face  31  of each steel plate  46 . Next, one steel plate  47  on which the piping supports  20  fixed to the individual steel plates  46  can be disposed at the respective intended positions in the X direction and the Y direction is given as a steel plate closest to the side of the outside steel plate. Next, the plurality of steel plates  46  are joined to the steel plate  47  on the side of the accessory, and a face of the steel plate  47  on the side of the outside steel plate is given as a steel plate joint face  32  and joined to the outside steel plate  11 . 
     As described so far, when the accessory joint face  31  is made smaller in area than the steel plate joint face  32 , the attachment plates  38 ,  40 ,  45  can be reduced in weight without decreasing a load of the piping support  20  received by the SC structure  10 . Therefore, where the accessory joint face  31  is made smaller in area than the steel plate joint face, it is preferable that an interval between the accessory joint face  31  and the steel plate joint face  32  be kept to a greater extent than a predetermined extent for the purpose of ensuring the strength against the load of the piping support  20  received by the attachment plates  38 ,  40 ,  45 . 
     Other Modified Example 
     In each of the so far-described embodiments and modified examples, a steel plate is used as the attachment plate, to which the present invention shall not be, however, restricted. Various types of plates such as a SUS plate may be used in the present invention. 
     Further, in these embodiments and modified examples, the piping support is joined to an attachment plate and the attachment plate is then joined to the outside steel plate  11 . It is, however, acceptable that an attachment plate be joined to the outside steel plate  11  and the piping support be then joined to the attachment plate. 
     Fourth Embodiment 
     Hereinafter, a description will be given of an accessory attachment structure of a Fourth Embodiment in the present invention by referring to drawings. 
     Prior to a description of the accessory attachment structure, a description will be first given of an accessory and an SC structure (steel plate-reinforced concrete structure)  201  to which the accessory is attached. 
     As shown in  FIG. 8 , the SC structure  201  is provided with two outside steel plates  202 , a plurality of bars  203  and concrete  204 . The outside steel plates  202  are opposed to each other to form a steel plate frame. The plurality of bars  203  are installed inside the steel plate frame and fixed to the steel plate frame. The concrete  204  is installed inside the steel plate frame. The bar  203  includes a tie bar  205  for connecting two outside steel plates  202  which form the steel plate frame and a stud  206  for steadily fixing the outside steel plate  202  to the concrete  204 . 
     Here, as a matter of convenience in giving the following description, in a pair of outside steel plates  202 , a right-hand direction in  FIG. 8( a )  from one outside steel plate  202  to the other outside steel plate  202  is given as the Z direction, an upper direction in  FIG. 8  perpendicular to the Z direction is given as the Y direction, and a backside direction on the page space of  FIG. 8( a )  perpendicular to the Z direction and the Y direction is given as the X direction. Further, the pair of outside steel plates  202  are parallel to an XY plane. 
     In the SC structure  201 , a mutual interval Ps between two studs  206  adjacent both in the X direction and the Y direction is, for example, 200 mm. Further, a mutual interval Pt between two tie bars  205  adjacent both in the X direction and the Y direction is, for example, 600 mm. Still further, a mutual interval Pst between a stud  206  and a tie bar  205  adjacent both in the X direction and the Y direction is, for example, 200 mm. That is, in the SC structure  201 , a mutual interval P between bars  203  in the X direction and the Y direction is 200 mm. 
     One end of each stud  206  is fixed to an inner face of the outside steel plate  202 . The other end of each stud  206  is joined to a cylindrical head  206   a  so as to be steadily fixed to the concrete  204  in an improved manner. 
     Each tie bar  205  passes through the concrete  204  and the outside steel plate  202 , and both ends thereof protrude from an outer face of the outside steel plate  202  by a predetermined length. That is, the tie bar  205  is longer than the thickness of the SC structure  201 . The protruded length is decided depending on the thickness of an attachment plate  209  to be described later and the thickness of a nut  211  for fixing the attachment plate  209  and set so as to be at least longer than a sum of these thicknesses. 
     As shown in  FIG. 9 , a tie bar hole  207  for being passed through by the tie bar  205  is formed at a position corresponding to the tie bar  205  of the outside steel plate  202 . The tie bar  205  is joined to the outside steel plate  202  by welding an inner face of the outside steel plate  202  to the tie bar  205 . Thereby, an interval between the outside steel plates  202  is kept constant. A reference numeral  213  shown in  FIG. 9  is a joint site. 
     An external thread portion  220  is formed on an outer circumference of a protrusion  205   a  at both ends of each tie bar  205 . A pitch of the external thread portion  220  is in agreement with a pitch of the nut  211  to be described later. 
     Next, a description will be given of an attachment structure of a piping support  208  in association with the above-described SC structure  201 . 
     The piping support  208  is formed with two H-steel members. The H-steel member has sizes of, for example, 100 mm (H)×100 mm (B). In addition, in the present invention, an accessory is not necessarily a piping support and may include fundamentally anything such as a support of ducts and a rack. 
     The piping support  208  is attached to the outside steel plate  202  of the SC structure  201  via an attachment plate  209 . The attachment plate  209  is formed, for example, with a single steel plate such as an SS (steel structure) material and an SM (steel marine) material. 
     The attachment plate  209  is a rectangular plate-like member when viewed from above. One side of the attachment plate  209  is, for example, 280 mm in length. An attachment hole  210  is formed at each of the four corners of the attachment plate  209 . The attachment holes  210  are passed by each of four protrusions  205   a  which are positioned so as to correspond thereto. 
     The piping support  208 , which is an accessory, is attached to the surface of the attachment plate  209  (hereinafter, referred to as accessory joint face  209   a ). The piping support  208  is provided with a beam  208   a  which directly supports a piping  225  and a reinforcing member  208   b  which reinforces the beam  208   a . The beam  208   a  is joined, for example, by welding in such a manner that the longitudinal direction thereof is orthogonal to the accessory joint face  209   a  of the attachment plate  209 . In addition, the beam  208   a  is joined to the accessory joint face  209   a  in such a manner that flanges (edges) of the beam  208   a  are positioned above and below. The reinforcing member  208   b  is joined so as to extend obliquely downward from a free-end lower face of the beam  208   a  joined to the attachment plate  209  toward the accessory joint face  209   a  of the attachment plate. Further, connection of the attachment plate  209  with the piping support  208  may be made in any form, for example, by welding, soldering or using connecting fittings such as screws. 
     The attachment plate  209  to which the piping support  208  is joined is attached by inserting the protrusions  205   a  of the tie bars  205  respectively into the four attachment holes  210 . Thereby, a back face of the attachment plate  209  (hereinafter, referred to as a steel plate joint face  9   b ) is allowed to come into contact with the outer face of the outside steel plate  202  of the SC structure  201 . Further, a nut  211  is fastened to an external thread portion of the protrusion  205 , by which the attachment plate  209  is fixed. 
     In the above embodiment, an end of the tie bar  205  is exposed, and an external thread portion  220  which is screwed into a nut is formed at this end. Therefore, it is possible to attach the attachment plate  209  to any given tie bar  205  after visual observation is made for a site at which the tie bar  205  is installed. Further, in terms of structure, the attachment plate  209  is directly fixed to the tie bar  205 . Therefore, stress resulting from a load of the piping support  208  is allowed to act on four tie bars  205  via the attachment plate  209 . It is thereby possible to reduce a load received by each one of the tie bars  205 . 
     Still further, the tie bar  205  protrudes from the outer face of the outside steel plate  202 . Therefore, in a step of fixing the attachment plate  209  to the SC structure  201 , an attachment plate  1  may be hooked to the protrusion  205   a  and retained temporarily. Thereby, fixing work is done more easily. 
     In the present embodiment, the attachment plate  209  can be attached to both sides of the SC structure  201 , to which the present invention shall not be, however, restricted. The attachment plate  209  may be attached to only one side of the SC structure  201 . 
     Fifth Embodiment 
     Next, a description will be given of an accessory attachment structure of a Fifth Embodiment of the present invention by referring to  FIG. 10  and  FIG. 11 . The accessory attachment structure of the Fifth Embodiment is provided such that the tie bar  205  of the above-described accessory attachment structure of the Fourth Embodiment is changed in structure. 
     As shown in  FIG. 11 , in a tie bar  205 A of the Fifth Embodiment, an end face  205 Aa is exposed from an outer face of an outside steel plate  202 . In the present embodiment, the end face  205 Aa is substantially flush with the outer face of the outside steel plate  202 . That is, the tie bar  205 A has a length which is substantially equal to the thickness of an SC structure  201 A. An internal thread hole  214  corresponding to a bolt  212  to be described later is formed on the end face  205 Aa of the tie bar  205 A. 
     As for the tie bar  205 A and outside steel plate  202 , the tie bar  205 A is inserted into a tie bar hole  207  in such a manner that the end face  205 Aa of the tie bar  205 A is disposed to be substantially flush with the outer face of the outside steel plate  202 , and an inner face of the outside steel plate  202  is welded to an outer circumferential face of the tie bar  205 A to fix them. Thereby, the internal thread hole  214  formed at the end face  205 Aa of the tie bar  205 A is fixed in a state of being exposed on the outer face of the outside steel plate  202 . 
     An attachment hole  210 A of an attachment plate  209 A to which a piping support  208  is attached has an inner diameter which allows the bolt  212  to pass therethrough. The attachment hole  210 A is, as with the Fourth Embodiment, formed at a position corresponding to each of the four tie bars adjacent to each other. The attachment plate  209 A is fixed to an SC structure  210 A by screwing four bolts  212  into the internal thread holes  214  and fastening the bolts. 
     In the above-described embodiment, the end  205 Aa of the tie bar  205 A is exposed on the outer face of the outside steel plate  202  and the internal thread hole  214  which is screwed with the bolt  212  is formed at the end  205 Aa. It is therefore possible to attach the attachment plate  209 A to any given tie bar  205 A after a site at which the tie bar  205 A is installed is visually observed. 
     Further, in terms of the structure, the attachment plate  209 A is directly attached to the tie bar  205 A. Therefore, stress derived from a load of the piping support  208  is allowed to act on the four tie bars  205 A via the attachment plate  209 A. 
     Still further, the tie bar  205 A does not protrude on the outside steel plate  202 . As a result, where the attachment plate  209 A is not fixed, the SC structure  201 A has a smoother exposed face. 
     Further, in the present embodiment, the end face  205 Aa is substantially flush with the outer face of the outside steel plate  202 , to which the present invention shall not be, however, restricted. The end face  205 Aa may be positioned inside the outer face of the outside steel plate  202 . Further, a hole may only be formed which can place a protruded part of the tie bar on the attachment plate  209 A, even if the end face  205 Aa is positioned outside the outer face of the outside steel plate  202 . 
     Sixth Embodiment 
     Next, a description will be given of an accessory attachment structure of a Sixth Embodiment of the present invention by referring to  FIG. 12 ,  FIG. 13  and  FIG. 14 . 
     As shown in  FIG. 14 , a tie bar  205 B of the present embodiment is constituted with a tie bar main body  215  and a pair of tie bar-fixing portions  216  which are joined to both ends of the tie bar main body  215 . The tie bar main body  215  is, for example, a 36-mm-across steel rod. The tie bar-fixing portion  216  is, for example, a 45-mm-across steel rod and integrally welded so as to be coaxial with both ends of the tie bar main body  215 . 
     The integrally formed tie bar  205 B has a length which is substantially equal to the thickness of an SC structure  201 B. 
     As shown in  FIG. 13 , each of the tie bar-fixing portions  216  is formed so as to have an outer diameter greater than a tie bar hole  207 B of an outside steel plate  202 B. An internal thread hole  217  corresponding to a bolt  218  to be described later is formed at an end face  216   a  of the tie bar-fixing portion  216 . 
     The tie bar  205 B is fixed to the outside steel plate  202  by screwing the bolt  218  into the internal thread hole  217  of the tie bar-fixing portion  216  in a state that the end face  216   a  of the tie bar-fixing portion  216  is allowed to come into contact with an inner face of an outside steel plate  202 B. That is, unlike the accessory attachment structure of the Fourth Embodiment or Fifth Embodiment, the tie bar  205 B is not welded to the outside steel plate  202 . Thereby, the internal thread hole  217  formed at the end face  216   a  of the tie bar-fixing portion  216  is exposed on an outer face of the outside steel plate  202 B via the tie bar hole  207 B. 
     On attachment of the attachment plate  209 B to the outside steel plate  202 B, the bolt  218  which fixes the tie bar  205 B corresponding to a position at which the attachment plate  209 B is attached is temporarily removed. And, the attachment plate  209 B is disposed on the outside steel plate  202  and again fastened and fixed by means of the bolt  218 . That is, the attachment plate  209 B is placed between the outside steel plate  202  and the bolt  218  and then fixed. 
     In the above-described embodiment, with regard to the tie bar  205 B, the outside steel plate  202  and the attachment plate  209 B, the bolt  218  is screwed into the internal thread hole  217  of the tie bar  205 B to fasten the outside steel plate  202  or fasten the outside steel plate  202  with the attachment plate  209 B. This will eliminate the need for a welding process, by which an SC structure can be constructed more easily. Further, concrete  204  different in thickness can be handled freely only by changing the length of the tie bar main body  215  of the tie bar  205 B. 
     Further, in this embodiment, a description has been given of a case where the bolt  218  is used to fasten and fix the outside steel plate  202  and the attachment plate  209 B. However, in place of forming the internal thread hole  217  at the tie bar-fixing portion  216 , a method may be used in which a pilot hole of a tapping bolt is provided to fasten and fix them by means of the tapping bolt. This method is applied to at least one side of the tie bar-fixing portion, which will not affect the positional accuracy or others of the tie bar hole  207 B of the outside steel plate  202 . 
     Further, the tie bar main body  215  may be integrally formed with the tie bar-fixing portion  216 . 
     Seventh Embodiment 
     Next, a description will be given of the Seventh Embodiment of the invention by referring to  FIG. 15 . 
     This embodiment is similar to the Sixth Embodiment in basic structure in which the tie bar is fastened and fixed to the outside steel plate  202  and the attachment plate  209  by using the bolt  218 . Therefore, in the following description, the same reference numerals are given to the same parts, with a description thereof omitted. Further, although  FIG. 15  shows only one end of a tie bar  205 C, both ends of the tie bar  205 C are identical in shape. 
     The tie bar  205 C of the present embodiment is constituted with a tie bar main body  215 C and a pair of tie bar-fixing portions  216 C,  216 C which are screwed into the both ends of the tie bar main body  215 C. An external thread is formed at both ends of the tie bar main body  215 C. An internal thread hole corresponding to the external thread of the tie bar main body  215 C is formed at each of the tie bar-fixing portions  216 . They are screwed thereinto to give an integrally formed tie bar  205 C. 
     According to the above-described embodiment, the tie bar  2050  is integrally formed by screwing the tie bar main body  215 C into the tie bar-fixing portion  216 . This will eliminate the need for a process such as welding, thus making it possible to change the length of the tie bar main body  215 C more easily. 
     Next, a description will be given of modified examples of the Fourth Embodiment to Seventh Embodiment so far described. 
     Modified Examples 
     In the individual embodiments so far described, a description has been given of a case where the correspondingly-shaped attachment plates  209 ,  209 A and  209 B are attached to the mutually-adjacent four tie bars  205 ,  205 A and  205 B. The present invention shall not be, however, restricted thereto. The attachment plate may be changed in size according to the size and others of an accessory. In addition to a regular tetragonal attachment plate, a rectangular attachment plate may be attached to each of the six tie bars  205  made up of two upper and lower stages, each containing three tie bars. Alternatively, a rectangular attachment plate with two attachment holes may be attached to two tie bars  205  which are mutually adjacent. 
     In addition, in the embodiments and modified examples so far described, after the piping support  208  is joined to the attachment plate  209 , the attachment plate is joined to the outside steel plate  202 . However, after the attachment plate  209  is joined to the outside steel plate  202 , the piping support  208  may be joined to the attachment plate  209 . 
     Eighth Embodiment 
     Hereinafter, a description will be given of an accessory attachment structure of an Eighth Embodiment of the present invention by referring to drawings. 
     As shown in  FIG. 16 , an accessory attachment structure  310 A of the Eighth Embodiment is provided such that an attachment plate  323  of a support member  322  which supports a duct  321  (long object) is attached to an SC structure (steel plate-reinforced concrete structure)  311 . 
     The SC structure  311  is provided such that concrete  314  is installed between a pair of outside steel plates  312 ,  313  which are opposed to each other at a certain interval. Further, the pair of outside steel plates  312 ,  313  are connected by means of a tie bar  315 , both ends of which are fixed by welding to an inner face of each of the outside steel plates  312 ,  313 . 
     The tie bar  315  connects the outside steel plates  312 ,  313 , thereby keeping an interval thereof constant, irrespective of the load received from the concrete  314 . The tie bars  315  are disposed vertically and transversely on the outside steel plates  312 ,  313 , with a constant interval kept. In the present embodiment, as shown in  FIG. 16 , a total of 100 tie bars  315  consisting of 10 columns in the longitudinal direction and 10 rows in the transverse direction are disposed individually so as to extend in a manner substantially orthogonal to the outside steel plates  312 ,  313 . Further, the tie bars  315  used here are identical in diameter and strength. The outside steel plates  312 ,  313  are connected with the tie bars  315  by stud welding or the like. 
     For example, plug welding is done to fix a head of the tie bar  315  to the outside steel plate  313 . Specifically, after the headed tie bar  315  is melted and settled on one outside steel plate  312  by stud welding, the other outside steel plate  313  on which a hole  313   a  for plug welding has been formed in advance is placed on the headed tie bar  315  and a leading end of a stud as a welding material is fused by arc stud welding to fill the hole  313   a . There is no particular restriction on a method for connecting the tie bars  315 . Any method will do as long as the head of the tie bar  315  is visible (does not protrude) at least on the surface of the outside steel plate  313  to which the support member  322  is attached. 
     On construction of the SC structure  311 , as shown in  FIG. 16 , the pair of outside steel plates  312 ,  313  are disposed so as to be opposed to each other, and both ends of each tie bar  315  are welded and fixed to the inner faces thereof. Such precast structures are produced in a large number, transported to a construction site and connected vertically and transversely. 
     Next, the concrete  314  is installed between the outside steel plates  312 ,  313  and the concrete  314  is hardened to complete the SC structure  311 . In addition, the SC structure  311  is constructed mainly as an external wall, a partition wall, a floor slab (foundation slab) and the like of a building. In general, subsequently attached members such as long objects including various types of machines in a building (hereinafter, a description will be given by referring to a duct  321 ) are installed in a state of being supported by support members (accessories)  322 . 
     An attachment plate  323  is attached to the surface of each of the outside steel plates  312 ,  313  in a region, the back side of which is provided at least with a plurality of tie bars  315 . Here, the tie bars  315  are disposed vertically and transversely at constant intervals in a state that a leading end of each tie bar  315  is exposed on the surface of the outside steel plate  313 . Further, where the attachment plate  323  is mounted on a plurality of tie bars  315 , the tie bars  315  can be fixed by welding at positions where the load is taken into account. 
     The duct  321  is placed for the purpose of evacuation of air at a control room of plant facilities or the like. The duct  321  is extended along the surface of the outside steel plate  313  in a state of being supported by support members  322 . The duct  321  is a round duct, the cross-section of which is circular, and used is a cylindrical duct made with a relatively thin steel plate. There is no restriction on types of long objects, including, for example, a rectangular duct. 
     The support member  322  is made with an H-steel member and fixed to the SC structure  311  via the attachment plate  323 . Specifically, the support member  322  is composed of a beam  324  for supporting the duct  321  and a reinforcing member  325  for supporting the beam  324 . The support member  322  may include an L-steel member and a channel bar in addition to the H-steel member. 
     The attachment plate  323  is a steel plate, the shape of which is rectangular, when viewed from above. The attachment plate  323  is provided such that each side thereof is fixed to the surface of the outside steel plate  313  by welding. The attachment plate  323  is attached to a region where at least a plurality of tie bars  315  is attached. That is, the attachment plate  323  is attached to a region, the back side of outside steel plate  313  is provided with a plurality of tie bars  315 . In the present embodiment, as shown in  FIG. 16 , the attachment plate  323  is fixed to a region which is the surface of the outside steel plate  313  and where a total of four tie bars  315  composed of two columns in the longitudinal direction×2 columns in the transverse direction are positioned on the back side thereof. Next, upper and lower two H-steel members  324 ,  325  are disposed so as to be respectively equal in height to the tie bars  315  which are two rows in the longitudinal direction and positioned substantially at the center of the tie bars  315  which are two columns in the transverse direction. There is no particular restriction on a position at which the attachment plate  323  is fixed to the outside steel plate  313  and positions at which the H-steel members  324 ,  325  are fixed to the attachment plate  323 . And, in the present embodiment, design of the position can be changed, whenever necessary. 
     As described so far, the pair of steel plates  312 ,  313  are connected only by the tie bars  315 . Therefore, loads of the attachment plate  323 , the H-steel members  324 ,  325  and the duct  321  are not supported only by the outside steel plate  313  but also supported by the outside steel plate  312  and the concrete  314  via individual tie bar  315 . 
     Thereby, as compared with a case where loads of the duct  321  and others are shared by studs (not illustrated) installed on the outside steel plates  312 ,  313 , defects and others are less likely to occur at individual portions which constitute the SC structure  311 , thus making it possible to improve the strength of the SC structure  311  as a whole. It is therefore possible to attach the support member  322  to the outside steel plate  313  at any position without restriction. 
     As described so far, in the accessory attachment structure  310 A of the present invention, the attachment plate  323  can be fixed by welding on the basis of the tie bars  315 , the heads of which are exposed on the surface. Therefore, the load of the duct  321  can be dispersed in a substantially uniform manner to the tie bars  315 . 
     Further, since heads of the tie bars  315  are exposed, in doing work for attaching the attachment plate  323  to the outside steel plate  313 , the work can be done, with confirmation made for positions of the tie bars  315 . It is therefore possible to perform construction in a shorter time. 
     Ninth Embodiment 
     As shown in  FIG. 17 , an accessory attachment structure  310 B of a Ninth Embodiment is different from the accessory attachment structure  310 A of the Eighth Embodiment in having a rib  316  and an inner steel plate  317 . Since other constitutions are the same as those of the Eighth Embodiment, the same reference numerals are given thereto, with a description omitted here. 
     The rib  316  is provided such that a plurality of long- and thin-rectangular flat plate members are assembled in a lattice form. The ribs  316  are individually fixed so as to extend all over the inner faces of outside steel plates  312 ,  313 . Further, the inner steel plate  317  is fixed to a leading end of the rib  316  (that is, an end opposite to the outside steel plate  312  or  313 ) and disposed substantially parallel to the outside steel plates  312 ,  313 . 
     According to the accessory attachment structure  310 B of the present ninth embodiment, the rib  316  and the inner steel plate  317  are fixed to the inner faces of the outside steel plates  312 ,  313 , by which the outside steel plates  312 ,  313  can be increased in rigidity. Thereby, as compared with the Eighth Embodiment, it is possible to further improve the strength of an SC structure  311  as a whole. 
     It is preferable that consideration be given to positions of the rib  316  and the inner steel plate  317  so that on installing concrete  314 , the concrete  314  can be installed evenly between the outside steel plates without preventing the influx of ready-mixed concrete. With the same purpose, a hole for the influx of ready-mixed concrete or the like may be formed on the rib  316  and the inner face steel plate  317 . 
     Tenth Embodiment 
     As shown in  FIG. 18 , an accessory attachment structure  310 C of a Tenth Embodiment is different from the accessory attachment structure  310 B of the Ninth Embodiment in constitution of a rib  318 . Since other constitutions are the same as those of the Ninth Embodiment, the same reference numerals are given thereto, with a description omitted here. 
     The rib  318  is provided such that a plurality of angle bars, each of which has an L-shape cross-section, are assembled in a lattice form, and the ribs are fixed individually so as to extend all over the inner faces of the outside steel plates  312 ,  313 . Further, as with the Ninth Embodiment, an inner steel plate  317  is installed which is fixed to the leading end of the rib  318  and disposed substantially parallel to the outside steel plates  312 ,  313 . The rib  318  is assembled in a lattice form by stacking a plurality of angle bars extending in the longitudinal direction and a plurality of angle bars extending in the transverse direction in upper and lower two stages. 
     According to the accessory attachment structure  310 C of the present tenth embodiment, it is possible to further ensure the strength thereof by using the L-shaped rib  318  in place of the rib  316 . It is desirable that the rib  318  which extends horizontally (transversely) face upward for facilitating the influx of ready-mixed concrete. It is also desirable that a rib  318  which extends longitudinally be first installed on the back face of each of the outside steel plates  312 ,  313  and a rib  318  which extends transversely be then disposed so as to be overlaid on the above-described rib  318  (or via the inner face steel plate  317 ) in view of facilitating the influx of ready-mixed concrete. Further, it is preferable that the edge of the rib  318  toward the other side of each of the outside steel plates  312 ,  313  (thickness direction) be overlaid on the tie bar  315 . Still further, in the illustrated example, the inner steel plate  317  is installed on a rib  318  which extends transversely. The inner steel plate  317  may be installed between a rib  318  which extends longitudinally and a rib  318  which extends transversely or may be installed on both of them (two inner steel plates). In addition, according to the present embodiment, one edge of an angle bar having an L-shaped cross-section is allowed to come into contact with the outside steel plates  312 ,  313  and be fixed. Therefore, the present embodiment is advantageous over the rib  316  of the Ninth Embodiment in that the rib  318  can be more simply and more rigidly fixed to the outside steel plates  312 ,  313 . 
     Eleventh Embodiment 
     As shown in  FIG. 19 , an accessory attachment structure  310 D of an Eleventh Embodiment is different from the accessory attachment structures  310 B,  310 C of the Ninth Embodiment and Tenth Embodiment in a constitution of a rib  319 . Since other constitutions are the same as those of the Ninth Embodiment and Tenth Embodiment, the same reference numerals are given to them, with a description omitted here. 
     The rib  319  is provided such that a plurality of C-shaped channel bars, each of which has a C-shaped cross-section, are assembled in a lattice form. The ribs  319  are individually fixed so as to extend all over the inner faces of the outside steel plates  312 ,  313 . Further, as with the Ninth Embodiment, an inner steel plate  317  is fixed to the leading end of the rib  319  and disposed substantially parallel to the outside steel plates  312 ,  313 . In addition, the rib  319  is formed in a lattice form by stacking a plurality of angle bars extending longitudinally and a plurality of angle bars extending transversely in upper and lower two stages. 
     According to the accessory attachment structure  310 D of the present eleventh embodiment, it is possible to further ensure the strength of the structure by using the C-shaped rib  319  in place of the ribs  316 ,  318 . In order to facilitate the influx of ready-mixed concrete, it is desirable that a rib  319  extending horizontally (transversely) face its opening side toward a rib  319  extending longitudinally. It is also desirable that a rib  319  extending longitudinally be first installed on the back face of each of the outside steel plates  312 ,  313  and a rib  319  extending transversely be then disposed so as to be overlaid on the above-described rib  319  in view of facilitating the influx of ready-mixed concrete. In addition, the inner steel plate  317  is not installed on the opening side of the rib  319  extending transversely. Further, in the present embodiment, one edge of the channel bar having a C-shaped cross-section is allowed to come into contact with the outside steel plates  312 ,  313  and be fixed. Therefore, as with the Tenth Embodiment, the present embodiment is advantageous in fixing the rib  319  to the outside steel plates  312 ,  313  more simply and more rigidly. 
     A description has been so far given of the embodiment of the accessory attachment structure of the present invention, to which the present invention shall not be, however, restricted. The present invention may be modified whenever necessary within a scope not departing from the gist of the present invention. 
     In the present embodiment, for example, the duct  321  is given as a long object which is supported by the support member  322 , to which the present invention shall not be restricted. The long object may include, for example, piping, a cable tray, and an electrical wire conductor. 
     Next, in the present embodiment, the support is provided by means of the H-steel members  324 ,  325  for supporting the duct  321  from below. However, the support may be constituted so as to hang down the duct  321 . Further, the support member  322  may include an L-steel member, a channel and a pipe in place of the H-beam member. 
     In the present embodiment, the attachment plate  323  has a substantially square external shape when viewed from above. There is no particular restriction on the outer shape. 
     Further, constituent features of the above-described embodiment may be replaced by known constituent features whenever necessary within a scope not departing from the gist of the present invention. Still further, the above-described embodiment may be combined in an appropriate manner. 
     Twelfth Embodiment 
     Hereinafter, a description will be given of a design system of an SC structure and a design method of an SC structure according to a Twelfth Embodiment of the present invention by referring to  FIG. 20  to  FIG. 25 . 
     First, as shown in  FIG. 20 , an SC structure (steel plate-reinforced concrete structure)  410  of the present embodiment is constituted, for example, with a steel plate frame  405 , a plurality of tie bars  406 , a plurality of studs  402  and concrete  401 . The steel plate frame  405  is formed with a plurality of outside steel plates  403 ,  404 . The plurality of tie bars  406  connect a pair of outside steel plates  403 ,  404  disposed so as to be opposed to each other in a plurality of outside steel plates  403 ,  404  which constitute the steel plate frame  405 . The plurality of studs  402  are fixedly installed on an inner face of each of the outside steel plates  403 ,  404 . The concrete  401  is installed inside the steel plate frame  405 . 
     One end of the tie bar  406  is joined to one outside steel plate  403  of the pair of outside steel plates  403 ,  404 . The other end of the tie bar  406  is joined to the other outside steel plates  404  and placed inside the steel plate frame  405  (embedded into the concrete  401 ). The studs  402  enhance connection of the outside steel plates  403 ,  404  with the concrete  401 , etc. Next, the stud  402  of the present embodiment is a headed stud equipped with a head  2   b  at one end of a shaft portion  402   a . The other end of the shaft portion  402   a  of the stud  402  is joined to an inner face of each of the outside steel plates  403 ,  404  by fillet welding or the like and placed inside the steel plate frame  405  (embedded into the concrete  401 ). Further, in the SC structure  410  of the present embodiment, as schematically shown in  FIG. 21( a )  and  FIG. 21( b ) , the plurality of studs  402  are disposed in a group. 
     Further, as shown in  FIG. 20 , an accessory  407  is attached to the SC structure  410 . In the present embodiment, the accessory  407  is a piping support  407   a  for supporting a piping  408 . The piping support  407   a  is formed, for example, by means of an H-steel member. And, the piping support  407   a  is provided with an attachment plate  407   b  which is a steel plate. The attachment plate  407   b  is joined to the outside steel plate  403  by welding or the like and attached to the SC structure  410 . 
     Next, in the present embodiment, a design system (design system of the SC structure)  420  is used to design the above-constituted SC structure  410 . As shown in  FIG. 22 , the design system  420  is provided with a structure condition input device  411 , a body load-calculating device  412 , reference load-calculating device  413 , load ratio-calculating device  414 , storage device  415 , effective projection area-calculating device  416 , and load-calculating device  417 . 
     In the present embodiment, in designing the SC structure  410 , (in the design method of the SC structure of the present embodiment), the following idea is applied to a case where a large pull-out load is applied to one stud  402  at the center in a state that a uniform load is applied to each of the studs  402  disposed in a group (in a state shown in  FIG. 27( b ) ). 
     First, the stud will be calculated for the load-bearing capacity in cone failure by using the following formula (2). 
     
       
         
           
             
               
                 
                   [Formula  2] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       
                         F 
                         = 
                           
                          
                         
                           G 
                            
                           
                             ( 
                             α 
                             ) 
                           
                         
                       
                     
                   
                   
                     
                       
                         = 
                           
                          
                         
                           φ 
                           × 
                           Ac 
                           × 
                           
                             Fc 
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     Where φ is the reduction coefficient (safety coefficient), Ac is the projection area and Fc is the concrete strength. 
     Next, in the present embodiment, the structure condition input device  411  is used to input the stud interval, Ps, the stud embedded depth, Le, and the stud diameter D. Next, on the basis of structure conditions input by the structure condition input device  411 , the body load-calculating device  412  is used to calculate an body load. Here, the body load is a load which can be taken into account in design such as its own weight of the SC structure  410  and seismic loads excluding a load of the accessory  407 . 
     Further, the reference load-calculating device  413  is used to calculate a reference load which can be supported by each one of the studs when supported by all the plurality of studs. Here, the reference load is an allowable load of the stud  402 . Still further, as shown in  FIG. 21( b ) , the reference load is a cone pull-out-bearing capacity where a plurality of studs  402  are disposed in a group, an interval between the studs  402  is narrow, and a circular area in which the embedded depth Le of each stud  402  is given as a radius is overlaid on another circular area and also where an effective projection area is rectangular. In other words, the reference load means how much a cone pull-out force is where the effective projection area is rectangular. 
     Next, the load ratio-calculating device  414  is used to calculate a load ratio α of the body load to the reference load. Further, with reference to a relationship between the load ratio α and the effective projection area Ac stored by the storage device  415 , the effective projection area Ac is calculated from the load ratio α by using the effective projection area-calculating device  416 . 
     For example, in the present embodiment, the storage device  415  stores in advance a relationship between the load ratio and the effective projection area shown in  FIG. 24 . Next, the effective projection area-calculating device  416  determines a circular effective profection area Ac (circle) by means of the formula (3) shown in  FIG. 23( a )  and determines a rectangular effective projection area Ac (square)  shown in  FIG. 23( b )  by means of the formula (4). Further, the effective projection area-calculating device  416  calculates the effective projection area Ac on the basis of the respective areas obtained from the formula (3) and the formula (4) and the load ratio α of the body load to the reference load calculated by the load ratio-calculating device  414  by referring to a relationship between the load ratio α and the effective projection area Ac (formula (5)). 
     
       
         
           
             
               
                 
                   [Formula  3] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     Ac 
                      
                     
                       ( 
                       
                         circle 
                       
                       ) 
                     
                   
                   = 
                   
                     π 
                     × 
                     Le 
                     × 
                     
                       ( 
                       
                         Le 
                         + 
                         D 
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
             
               
                 
                   [Formula  4] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     Ac 
                      
                     
                       ( 
                       
                         square 
                       
                       ) 
                     
                   
                   = 
                   
                     
                       Ps 
                       × 
                       Ps 
                     
                     - 
                     
                       π 
                       × 
                       
                         
                           D 
                           2 
                         
                         / 
                         4 
                       
                     
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
             
               
                 
                   [Formula  5] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       
                         Ac 
                         = 
                           
                          
                         
                           f 
                            
                           
                             ( 
                             α 
                             ) 
                           
                         
                       
                     
                   
                   
                     
                       
                         = 
                           
                          
                         
                           
                             Ac 
                              
                             
                               ( 
                               
                                 circle 
                               
                               ) 
                             
                           
                           - 
                           
                             
                               ( 
                               
                                 
                                   Ac 
                                    
                                   
                                     ( 
                                     
                                       circle 
                                     
                                     ) 
                                   
                                 
                                 - 
                                 
                                   Ac 
                                    
                                   
                                     ( 
                                     
                                       square 
                                     
                                     ) 
                                   
                                 
                               
                               ) 
                             
                             × 
                             α 
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
     On the basis of the effective projection area Ac calculated by the effective projection area-calculating device  416 , the load-calculating device  417  is used to calculate a load which can be supported by one stud including an accessory load. Here,  FIG. 25  shows results covering the load-bearing capacity of a stud preliminarily calculated by the above-described design method under the conditions that the stud interval Ps is 200 mm, the stud diameter D is 35 mm, the stud embedded depth Le is 170 mm and the concrete strength Fc is 30 MPa. 
     As shown in the above preliminary calculation results, according to the design method of the present embodiment, the stud can be determined for the load-bearing capacity in a state of L 0  where no body load is applied (in a state of the circular effective projection area Ac (circle) ). Also, the stud can be determined for the load-bearing capacity in a load state between a state that the body load is not applied at all and a state that an allowable load of the stud  402  (reference load) is applied as the body load (rectangular effective projection area Ac (square) ). The above-described load state includes, for example, a state of L 1/3  that ⅓ of the allowable load of the stud is applied as the body load and a state of L 2/3  that ⅔ of the allowable load of stud is applied as the body load. 
     That is, according to the design system  420  of SC structure  410  and the design method of SC structure  410  of the present embodiment, as compared with a conventional design method of an SC structure, a method for determining an effective projection area in cone failure is reviewed to determine an effective projection area Ac depending on an applied load. Thereby, the stud can be rationally evaluated for the load-bearing capacity. 
     A description has been so far given of one embodiment of the design system of the SC structure and the design method of the SC structure of the present invention. However, the present invention shall not be restricted to the Twelfth Embodiment described above and may be modified whenever necessary within a scope not departing from the gist of the present invention. 
     Thirteenth Embodiment 
     Hereinafter, a description will be given of an SC structure of a Thirteenth Embodiment of the present invention by referring to  FIG. 28  to  FIG. 31 . 
     An SC structure (steel plate-reinforced concrete structure)  510  of the present embodiment is provided, for example as shown in  FIG. 28 , with a steel plate frame  505 , a plurality of tie bars  506 , a plurality of studs  502 , and concrete  501 . The steel plate frame  505  is formed with a plurality of outside steel plates  503 ,  504 . The plurality of tie bars  506  connect a pair of outside steel plates  503 ,  504  disposed so as to be opposed to each other in the plurality of outside steel plates  503 ,  504  which form the steel plate frame  505 . The plurality of studs  502  are fixedly installed on an inner face of each of the outside steel plates  503 ,  504 . The concrete  501  is installed inside the steel plate frame  505 . 
     One end of the tie bar  506  is joined to one outside steel plate  503  of the pair of outside steel plates  503 ,  504 . The other end of the tie bar  506  is joined to the other outside steel plate  504  and placed inside the steel plate frame  505  (embedded into the concrete  501 ). 
     The studs  502  enhance connection of the outside steel plates  503 ,  504  with the concrete  501  or others. Next, the stud  502  of the present embodiment is a headed stud which is provided with a head  502   b  at one end of a shaft portion  502   a . The other end of the shaft portion  502   a  of the stud  502  is joined to an inner face of each of the outside steel plates  503 ,  504  by fillet welding or the like and placed inside the steel plate frame  505  (embedded into the concrete  501 ). 
     In the SC structure  510  of the present embodiment, the plurality of studs  502  are disposed in a group and fixedly installed on the outside steel plates  503 ,  504 . Further, the plurality of studs  502  are not arranged or disposed vertically and transversely (lattice form arrangement) as with a conventional case as shown in  FIG. 29( a )  but arranged in a zigzag form as shown in  FIG. 29( b ) . 
     In the present embodiment, the plurality of studs  502  arranged in a zigzag form are arranged in such a manner that three mutually adjacent studs  502  take the vertexes of an equilateral triangle, as shown in  FIG. 29( b )  and  FIG. 30 . Further, at this time, a length P of one side of the equilateral triangle is set in accordance with the length of the stud. Specifically, in the present embodiment, when the diameter of the stud is given as D and the embedded depth of the stud  502  into the concrete  501  (stud length) is given as Le, the length P of one side of the equilateral triangle is expressed as P=2×Le+D. Further, in the present embodiment, since a headed stud is used, the diameter D of the stud  502  is not the diameter of the shaft portion  502   a  but the diameter of the head  502   b.    
     An idea used in evaluating the pull-out-bearing capacity of the stud  502  assumes cone failure and sets an angle of cone failure surface at 45 degrees. Therefore, where the plurality of studs  502  are arranged so that the three above-described adjacent studs  502  take the vertexes of an equilateral triangle, the interval P of adjacent studs  502 , that is, the diameter of a circular projection plane Ac in cone failure is given as one side of the equilateral triangle, and the circular projection planes Ac of adjacent studs  502  are not overlaid but come in contact with each other. Therefore, the circular projection planes Ac of the plurality of studs  502  are not overlaid but in contact with each other, thereby, reaching a state that the circular projection planes Ac of the plurality of studs  502  are disposed most densely in a plane of the steel plate. 
     Next, in the SC structure  510  of the present embodiment, the plurality of studs  502  are disposed as described above, by which the studs are disposed uniformly and rationally all over on the surface of the SC structure  510 . Further, no projection planes are overlapped between the studs, thereby eliminating the need for taking into account the effects of the studs disposed in a group on evaluation of the load-bearing capacity. 
     Therefore, in the SC structure  510  of the present embodiment, it is possible to evaluate the load-bearing capacity of each stud  502  as an independent stud  502 . As compared with a case where the plurality of studs  502  are arranged and disposed vertically and transversely (lattice form arrangement), the stud can be evaluated rationally for the load-bearing capacity. 
     On the other hand, as shown in  FIG. 28 , an accessory  507  is attached to the SC structure  510  of the present embodiment. In the present embodiment, the accessory  507  is a piping support  507   a  for supporting a piping  508 . The piping support  507   a  is formed, for example, with an H-steel member. Further, the piping support  507   a  of the accessory  507  is provided such that an attachment plate  507   b  which is a steel plate is attached and the attachment plate  507   b  is joined to the outside steel plate  503  by welding and attached to the SC structure  510 . 
     Here, in the SC structure, on joining the attachment plate  507   b  (piping support  507   a ) to the outside steel plate  503 , transfer of loads to as many studs  502  as possible is advantageous in view of the strength. In contrast, in the SC structure  510  of the present embodiment, a plurality of studs  502  are disposed so that as described above, three mutually adjacent studs  502  take the vertexes of an equilateral triangle and the plurality of studs  502  are disposed so that circular projection areas Ac are not overlaid but in contact with each other. 
     In the SC structure  510  of the present embodiment in which the plurality of studs  502  are disposed as described above, as shown in  FIG. 31 , the attachment plate  507   b  can be formed into a circular shape, the radius of which is equal to an attachment interval P between the studs  502 . In this case, it is possible to transfer loads to seven studs  502  in a maximum case and three studs  502  in a minimum case. 
     A description has been so far given of one embodiment of an SC structure of the present invention. The present invention shall not be restricted to the Thirteenth Embodiment described above but may be modified whenever necessary within a scope not departing from the gist of the present invention. 
     For example, in the present embodiment, a plurality of studs  502  are disposed in a zigzag form, that is, disposed so that three mutually adjacent studs  502  take the vertexes of an equilateral triangle, by which circular projection areas Ac are not overlaid but in contact with each other. In contrast, it is acceptable that as shown in  FIG. 32( a ) , the circular projection areas Ac of mutually adjacent studs  502  on cone failure surfaces be overlaid with each other to supply the gap between the circular projection areas Ac. 
     As shown in  FIG. 32( b ) , even where the plurality of studs  502  is disposed in a lattice form, these studs  502  are to supply the gaps between the circular projection areas Ac. However, where the plurality of studs  502  is disposed in a lattice form, it is necessary that the stud embedded depth Le (=1.4141 . . . ) is multiplied by the square root (√2). However, where the plurality of studs  502  is disposed in a triangular form, the stud embedded depth Le is multiplied by the degree of 2/√3 (=1.154 . . . ), thus making it possible to fill a plane of the steel plate. That is, an effect obtained by increasing the stud embedded depth Le (or decreasing the stud interval Ps) in order to increase the strength of attaching the outside steel plates  503 ,  504  to the concrete  501  by means of the studs  502  is made greater when the studs are disposed in an equilateral triangle as described in the present embodiment than when the studs are disposed in a conventional lattice form. Therefore, the present invention is able to effectively increase the strength of attaching the outside steel plates  503 ,  504  to the concrete  501  by means of the studs  502 . 
     In the SC structure  510 , disposal of the studs is decided in general so as not to cause buckling of the steel plates  503 ,  504  of the SC structure  510 . Next, the following formula (2) expressed as a width-to-thickness ratio of the steel plate  503  supported at points by the studs  502  is indicated on page  49 , “Technical Code for Seismic design of Steel Plate-reinforced Concrete Structures” Japan Electric Association Code (Atomic Power Section), JEAC 4618-2009 complied by the Japan Electric Association on Mar. 30, 2010 (refer to  FIG. 33 ). Here, Ps is the stud interval (mm), t is the thickness of the outside steel plate  503  (mm), and F is the reference value (N/mm 2 ) on decision of the allowable stress of the steel plate  503 . 
       [Formula 6] 
         L/t≤ 600/√{square root over ( F )}  (6)
 
     Next, where the stud interval Ps is set on the basis of the above-described formula (6), it is possible to establish the stud embedded depth Le which is more rational than the present embodiment, with the aim of rationally disposing the studs  502  in the form of an equilateral triangle. That is, in reverse to the present embodiment, even where the stud interval Ps is set first, it is possible to decide rationally the stud embedded depth Le on disposal of the studs  502  at the equilateral triangle. 
     Fourteenth Embodiment 
     Hereinafter, a description will be given of a construction method of an SC structure and an SC structure of the Fourteenth Embodiment of the present invention by referring to  FIG. 34  to  FIG. 36 . 
     An SC structure (steel plate-reinforced concrete structure)  610  of the present embodiment is, for example, as shown in  FIG. 34 , provided with a steel plate frame  613 , a plurality of tie bars  614 , a plurality of studs  615 , and concrete  616 . The steel plate frame  613  is formed with a plurality of outside steel plates  611 ,  612 . The plurality of tie bars  614  connect a pair of outside steel plates  611 ,  612  which are opposed to each other in the plurality of outside steel plates  611 ,  612  which form the steel plate frame  613 . The plurality of studs  615  are fixedly installed on inner faces  611   a ,  612   a  of the respective outside steel plates  611 ,  612 . The concrete  616  is installed inside the steel plate frame  613 . 
     One end of the tie bar  614  is joined to one outside steel plate  611  of the pair of outside steel plates  611 ,  612 . The other end of the tie bar  614  is joined to the other outside steel plate  612  and placed inside the steel plate frame  613  (embedded into the concrete  616 ). The studs  615  enhance connection of the outside steel plates  611 ,  612  with the concrete  616 , etc. Next, the stud  615  of the present embodiment is a headed stud equipped with a head  615   b  at one end of a shaft portion  615   a . The other end of the shaft portion  615   a  of the stud  615  is joined to the inner face  611   a  or  612   b  of the outside steel plate  611  or  612  by fillet welding or the like and placed inside the steel plate frame  613  (embedded into the concrete  616 ). 
     As shown in  FIG. 34  to  FIG. 36 , in the SC structure  610 , accessories  617  are attached to outer faces  611   b ,  612   b  of the outside steel plates  611 ,  612 . In the present embodiment, the accessory  617  supports the piping  602 . The accessory  617  is provided with a piping support  617   a  formed by using an H-steel member and a steel-plate made attachment plate  617   b  attached to the piping support  617   a  and thereby attached to the outside steel plate  611 . The attachment plate  617   b  is joined to the outside steel plate  611  by welding or the like. Here, in the present embodiment, the accessory  617  is made up of the piping support  617   a  and the attachment plate  617   b . Further, a raised portion  619  is formed on an attachment face of the attachment plate  617   b  which is in contact with the outer face  611   b  of the outside steel plate  611 . 
     On the other hand, in the SC structure  610  of the present embodiment, a plurality of studs  615  (tie bars  614 ) are arranged and disposed on the inner faces  611   a ,  612   a  of the outside steel plates  611 ,  612  and fixedly installed thereon. Further, on the outside steel plate  611 , a center position surrounded by four studs  615  (and tie bars  614 ) thus arranged and disposed is given as an attachment position to which the accessory  617  can be attached. Still further, a locking portion  620  is installed at a plurality of attachment positions to which the accessories  617  are attached on the outer face  611   b  of the outside steel plate  611 . The locking portion  620  of the present embodiment is an engagement recess portion (recess) with which a raised portion  619  formed on an attachment face of the attachment plate  617   b  is engaged. The attachment plate  617   b  and the piping support  617   a  are locked by the locking portion  620 . In the present embodiment, the attachment device  618  is made up of the raised portion  619  and the locking portion  620  having an engagement recess portion. The raised portion  619  of the accessory  617  is selectively locked to any of the plurality of locking portions  620  installed at each of the plurality of attachment positions, by which the accessory  617  is fixed onto the outer face  611   b  of the outside steel plate  611 . 
     Next, a description will be given of a construction method (production method) of the above-constituted SC structure  610  of the present embodiment. On constructing the SC structure  610  of the present embodiment, first, the plurality of studs  615  are fixedly installed on inner faces  611   a ,  612   a  of the outside steel plates  611 ,  612  (stud-attaching step). 
     Further, at least a part of the attachment device  618  is disposed at a plurality of attachment positions on the outer face  611   b  of the outside steel plate  611  (attachment device-preparing step). Here, in the present embodiment, at the attachment device-preparing step, a locking portion  620  (that is, an engagement recess portion), or a part of the attachment device  618 , is formed at every attachment position which is a center position surrounded by four studs  615  (and the tie bars  614 ). 
     Next, the outside steel plates  611 ,  612  are disposed at predetermined positions to forma steel plate frame  613  (steel plate-installing step). Next, the concrete  616  is installed inside the steel plate frame  613  (concrete-installing step). 
     Next, the accessory  617  having the attachment plate  617   b  and the piping support  617   a  is fixed and attached to the outer face  611   b  of the outside steel plate  611  (accessory-fixing step). At this time, the raised portion  619  installed on the attachment plate  617   b  is selectively engaged with any of the engagement recess portions of the locking portion  620  installed at the plurality of attachment positions on the outer face  611   b  of the outside steel plate  611 , by which the accessory  617  is locked. Further, the attachment plate  617   b  is fixed to the outer face  611   b  of the outside steel plate  611  by welding. Finally, a piping  602  is installed on the piping support  617   a  of the accessory  617  (piping-installing step). Thereby, the accessory  618  is attached to the outer face  611   b  of the outside steel plate  611  and construction is completed. 
     Next, in the construction method of the SC structure  610  of the present embodiment, at the attachment device-preparing step, at least the locking portion  620  (engagement recess portion) or the part of the attachment device  618  is disposed at the plurality of attachment positions on the outer face  611   b  of the outside steel plate  611  to which the accessory  617  can be attached. Therefore, at least a part of the attachment device  618  can be disposed, while the position of the stud  615  can be confirmed easily. 
     In the present embodiment, at the accessory-fixing step, the raised portion  619  of the attachment plate  617   b  of the accessory  617  is engaged with the engagement recess portion of the locking portion  620  to attach the accessory  617 . Thereby, the accessory  617  can be attached, with confirmation given to the position of the stud  615 . It is therefore possible to attach and construct the accessory  617 , while a load applied to each one of the studs can reliably be kept low. 
     Further, the accessory  617  is selectively locked to any of the locking portions  620  installed at the plurality of attachment positions on the outer face  611   b  of the outside steel plate  611 . Thereby, the accessory  617  can be attached at any given position. 
     Therefore, in the construction method of the SC structure  610  of the present embodiment, at the attachment device-preparing step, at least a part of the attachment device  618  is disposed at the plurality of attachment positions on the outer face  611   b  of the outside steel plate  611  to which the accessory  617  can be attached. It is therefore possible to dispose at least a part of the attachment device  618 , while the position of the stud  615  can be confirmed easily. Next, at the piping-installing step, on installation of the piping  602  on the accessory  617 , the piping  602  can be attached and constructed, while a load applied to each one of the studs is reliably kept low. 
     Further, in the SC structure  610  of the present embodiment, the raised portion  619  of the accessory  617  is selectively locked to any of the locking portions  620  installed at the plurality of attachment positions on the outer face  611   b  of the outside steel plate  611 . Therefore, it is possible to attach the accessory  617  to the outer face  611   b  of the outside steel plate  611  via the attachment device  618 . Thereby, such a simple procedure is carried out that the plurality of attachment positions at which a load applied to each one of the studs can be kept low are set and the raised portion  619  of the main body  617  is locked to the locking portion  620  installed at the attachment position, thus making it possible to attach and construct the accessory  617  while the load applied to each one of the studs is reliably kept low. Still further, the raised portion  619  of the accessory  617  can be selectively locked to any of the locking portions  620  installed at the plurality of attachment positions on the outer face  611   b  of the outside steel plate  611 . It is therefore possible to attach the accessory  617  to any given attachment position. 
     Therefore, according to the construction method of the SC structure  610  and the SC structure  610  of the present embodiment, the accessory  617  can be attached and constructed, while a load applied to each one of the studs is reliably kept low. As compared with a conventional case, it is also possible to reduce the time necessary for constructing the accessory  617  and also time necessary for designing the attachment position of the accessory  617 . 
     A description has been so far given of one embodiment of the construction method of the SC structure and the SC structure of the present invention. However, the present invention shall not be restricted to the Fourteenth Embodiment described above but may be modified whenever necessary within a scope not departing from the gist of the present invention. 
     In the present embodiment, the locking portion  620  of the attachment device  618  is given as an engagement recess portion and the raised portion  619  installed on the attachment plate  617   b  of the accessory  617  is engaged with the engagement recess portion. However, it is acceptable that the locking portion  620  be given as an engagement raised portion and a recess portion installed on the accessory  617  be engaged with the engagement raised portion  620 , by which the main body  617  is locked to the locking portion  620 . 
     Further, as shown in  FIG. 37  and  FIG. 38 , it is acceptable that a plurality of studs  615  be fixedly installed on inner faces  611   a ,  612   a  of the outside steel plates  611 ,  612 , and the piping support  617   a  (accessory  617 ) be fixed and attached by welding or the like to a plurality of attachment positions on the outer face  611   b  of the outside steel plate  611 . In this case also, as with the present embodiment, it is possible to attach and construct the accessory  617 , while a load applied to each one of the studs is reliably kept low. Further, as compared with a conventional case, it is possible to reduce the time necessary for constructing the accessory  617  and the time necessary for designing the attachment position of the accessory. 
     Fifteenth Embodiment 
     Hereinafter, a description will be given of an SC structure of a Fifteenth Embodiment of the present invention by referring to  FIG. 40   FIG. 43 . 
     An SC structure (steel plate-reinforced concrete structure)  709 A of the present embodiment is, for example as shown in  FIG. 40 , provided with a steel plate frame  703 , a plurality of tie bars  704 , a plurality of studs  705 , and concrete  706 . The steel plate frame  703  is formed with a plurality of outside steel plates  701 ,  702 . The plurality of tie bars  704  connect one pair of outside steel plates  701 ,  702  which are opposed to each other in the plurality of outside steel plates  701 ,  702  which constitute the steel plate frame  703 . The plurality of studs  705  are fixedly installed on an inner face of each of the outside steel plates  701 ,  702 . The concrete  706  is installed inside the steel plate frame  703 . 
     Further, as shown in  FIG. 40 , an accessory  707  is attached to the SC structure  709 A. In the present embodiment, the accessory  707  is a piping support  707   a  for supporting a piping  708 . The piping support  707   a  is formed, for example, by using an H-steel member. The piping support  707   a  of the accessory  707  is provided with an attachment plate (attachment plate)  707   b  which is a steel plate. The attachment plate  707   b  is joined to the outside steel plate  701  by welding or the like. Thereby, the accessory  707  is attached to the SC structure  709 A. 
     One end of the tie bar  704  of the SC structure  709 A is joined to one outside steel plate  701  of the pair of outside steel plate  701 ,  702 . The other end of the tie bar  704  is joined to the other outside steel plate  702  and placed inside the steel plate frame  703  (embedded into the concrete  706 ). 
     The studs  705  enhance connection of the outside steel plates  701 ,  702  with the concrete  706 , etc. The studs  705  are fixed to the outside steel plates  701 ,  702  and installed so as to protrude into the steel plate frame  703 . On the other hand, the stud  705  of the present embodiment is provided with a cylindrical shaft portion  710 , a first holding portion (the other holding portion)  711  and a head  712 , as shown in  FIG. 41( a ) . The first holding portion  711  is placed to the other side only by a predetermined length from one side of the shaft portion  710  which is fixed to the outside steel plate  701  ( 702 ) and formed integrally. The head  712  is integrally formed on the other side of the shaft portion  710 . Further, the first holding portion  711  and the head  712  are respectively formed in the shape of a circular plate, for example. The first holding portion  711  and the head  712  are placed in such a manner that their respective center axes are made coaxial with the shaft portion  710  and the outer-circumference edge is allowed to protrude radically outward from an outer circumference face of the shaft portion  710 . 
     In the SC structure  709 A, a through-hole  713  which pass through from an inner face  701   a  ( 702   a ) to an outer face  701   b  ( 702   b ) is formed at a predetermined position of the outside steel plate  701  ( 702 ) to which the stud  705  is attached. In the SC structure  709 A of the present embodiment, as shown in  FIG. 41( a ) , one side of the shaft portion  710  is inserted through the through-hole  713  of the outside steel plate  701  ( 702 ) and the first holding portion  711  is allowed to come into contact with the inner face  701   a  ( 702   a ) of the outside steel plate  701  ( 702 ), thereby placing the stud  705 . Next, as shown in  FIG. 41( b ) , one side (end) of the shaft portion  710  protruding beyond the through-hole  713  outside from the outer face  701   b  ( 702   b ) of the outside steel plate  701  ( 702 ) is collapsed to form a second holding portion (one holding portion)  714 , which is then crimped. Thereby, one pair of holding portions  711 ,  714  are used to hold the outside steel plate  701  ( 702 ) between them, by which the stud  705  is fixed to a predetermined position of the outside steel plate  701  ( 702 ) in a manner similar to a rivet structure. 
     Here, it is desirable that the studs  705  be constructed by being attached to the outside steel plates  701 ,  702  with use of an AR machine (automatic studding machine, automatic riveter) in a modified manner. 
     As shown in  FIG. 42 , an AR machine  715  is, for example, provided with a positioning portion  716  and an AR main body  717 . The positioning portion  716  retains the outside steel plates  701 ,  702  and also positions them. The AR main body  717  attaches studs  705  to the outside steel plates  701 ,  702 . Further, the positioning portion  716  is actuated on the basis of triaxial translation (forward and backward movement along the X axis, the Y axis and the Z axis) and biaxial rotation of A axis (around the X axis) and B axis (around the Y axis; movement by a difference in height between the Z axis and the W axis). As shown in  FIG. 42  and  FIG. 43 , the AR main body  717  is provided with a cutter head  718  and a working head  719 . The cutter head  718  drills a through-hole  713  at a predetermined position of the outside steel plate  701 ,  702  decided by the positioning portion  716 . The working head  719  attaches the studs  705  to the outside steel plates  701 ,  702 . 
     On attachment and construction of the studs  705  by using the AR machine  715 , first, positions at which the studs  705  are attached to the outside steel plate  701  ( 702 ) are stored in an NC machine. Next, as shown in  FIG. 42  and  FIG. 43( a ) , the outside steel plate  701  ( 702 ) is set on the positioning portion  716  to start construction. Thereby, the positioning portion  716  is actuated to place the outside steel plate  701  ( 702 ) at a predetermined position. Next, the NC controlled cutter head  718  is used to drill the through-hole  713  at a position to which the outside steel plate  701  ( 702 ) is attached by the stud. Next, as shown in  FIG. 43( b ) , the working head  719  retains the stud  705  and inserts one end of the shaft portion  710  into the through-hole  713 . Herewith, as shown in  FIG. 43( c ) , one end of the shaft portion  710  is crimped to form a second holding portion  714 . 
     Thereby, in the SC structure  709 A of the present embodiment, the AR machine  715  can be used to attach the studs  705  automatically and rationally to the outside steel plates  701 ,  702 . Further, as compared with a conventional case where the studs  705  are fixed to the outside steel plates  701 ,  702  by welding, it is possible to reduce man-hours necessary for constructing the studs and also reduce the construction cost. 
     On the other hand, as shown in  FIG. 40 , the SC structure  709 A is constructed in such a manner that the steel plate frame  703  is formed with the outside steel plates  701 ,  702  to which the studs  705  are attached and connected by the tie bars  704  and then the concrete  706  is installed inside the steel plate frame  703 . When the accessory  707  is attached to the SC structure  709 A of the present embodiment, as shown in  FIG. 40  and  FIG. 41( b ) , the stud  705  of the SC structure  709 A is fixed by holding the outside steel plate  701  by the pair of holding portions  711 ,  714 . Therefore, it is possible to locate a position of the stud  705  from outside of the outside steel plate  701  by means of the second holding portion  714  installed on the outer face  701   b  of the outside steel plate  701 . 
     Thereby, in the SC structure  709 A of the present embodiment, on attachment of the accessory  707 , the position of the stud  705  can be easily located by means of one holding portion  714 . As a result, it is possible to reduce the time necessary for constructing the accessory  707  and the time necessary for designing an attachment position of the accessory  707 . 
     Sixteenth Embodiment 
     Next, with reference to  FIG. 40  and  FIG. 44 , a description will be given of an SC structure of a Sixteenth Embodiment of the present invention. A detailed description will be omitted of the same constitutions as those of Fifteenth Embodiment. 
     As shown in  FIG. 44 , in an SC structure (steel plate-reinforced concrete structure)  709 B of the present embodiment, each stud  720  is constituted with a bolt  721  and three nuts  722 ,  723 ,  724 . Next, in the SC structure  709 B, a through-hole  713  is formed at a predetermined position of an outside steel plate  701  ( 702 ) to which the stud  720  is attached. A shaft portion  721   a  of the bolt  721  of the stud  720  is inserted through the through-hole  713  from an outer face  701   b  ( 702   b ) of the outside steel plate  701  ( 702 ), by which the head  721   b  of the bolt  721  is allowed to come into contact with the outer face  701   b  ( 702   b ) of the outside steel plate  701  ( 702 ). Further, the first nut  722  is screwed into the shaft portion  721   a  of the bolt  721  which protrudes to the inner face  701   a  ( 702   a ) of the outside steel plate  701  ( 702 ). Thereby, the head  721   b  of the bolt  721  (a second holding portion, one holding portion) and the first nut  722  (first holding portion, the other holding portion) are given as a pair of holding portions  721   b ,  722 , thereby holding the outside steel plate  701  ( 702 ) between them. Thereby, the stud  720  is fixed to the outside steel plate  701  ( 702 ) by the head  721   b  of the bolt  721  and the first nut  722 . 
     The second nut  723  is screwed into the shaft portion  721   a  of the bolt  721 , by which the first nut  722  is fastened with the second nut  723 . As a result, the outside steel plate  701  ( 702 ) is fastened by these two nuts of the first nut  722  and the second nut  723 , thereby preventing loosening of the nut  722 . As a result, the stud  720  is reliably fixed to the outside steel plate  701  ( 702 ). 
     Further, the third nut  724  is screwed into the shaft portion  721   a  of the bolt  721 . At this time, the third nut  724  is placed on the other side of the shaft portion  721   a  of the bolt  721 . As a result, the stud  720  of the present embodiment has a head at the other end by the third nut  724  and formed like a headed stud. 
     In the above-constituted SC structure  709 B of the present embodiment, the stud  720  is made up of the bolt  721  and the nuts  722 ,  723 ,  724 . The shaft portion  721   a  of the bolt  721  is inserted through the through-hole  713  on the outside steel plate  701  ( 702 ) to fasten the nut  722 , by which the head  721   b  of the bolt  721  and the nut  722  are given as a pair of holding portions and hold the outside steel plate  701  ( 702 ) between them. As a result, the stud  720  can be fixed to the SC structure  709 B. Thereby, also in the SC structure  709 B of the present embodiment, as compared with a conventional case where a stud is fixed to the outside steel plate by welding, it is possible to reduce man-hours for constructing the stud and also reduce the construction costs. 
     In the SC structure  709 B of the present embodiment, the outside steel plate  701  ( 702 ) is held between a pair of holding portions, that is, the head  721   b  of the bolt  721  and the nut  722  and fixed by the stud  720  of the SC structure  709 B. Therefore, it is possible to locate a position of the stud  720  from outside of the outside steel plate  701  ( 702 ) by means of the head  721   b  of the bolt  721  which is a second holding portion installed on an outer face  701   b  ( 702   b ) of the outside steel plate  701  ( 702 ) on attachment of an accessory  707 . 
     Accordingly, in the SC structure  709 B of the present embodiment as well, as with Fifteenth Embodiment, the position of the stud  720  can be easily located by means of one holding portion  721   b  on attachment of the accessory  707 . Therefore, it is possible to reduce the time necessary for constructing the accessory  707  and also the time necessary for designing an attachment position of the accessory  707 . 
     A description has been so far given of the Fifteenth Embodiment and Sixteenth Embodiment of the SC structures of the present invention. The present invention shall not be, however, restricted to the Fifteenth Embodiment and Sixteenth Embodiment described above and may be modified whenever necessary within a scope not departing from the gist of the present invention. 
     As shown in  FIG. 45 , for example, a recess portion  725  communicatively connected to the through-hole  713  may be formed on the outer face  701   b  ( 702   b ) of the outside steel plate  701  ( 702 ). In this case, as compared with the Fifteenth Embodiment, one end of the shaft portion  710  of the stud  705  is inserted into the through-hole  713  from the inner face  701   a  ( 702   a ) of the outside steel plate  701  ( 702 ) to form a second holding portion  714 , and also the second holding portion  714  can be placed into the recess portion  725 . Further, as compared with the Sixteenth Embodiment, the head  721   b  of the bolt  721  of the stud  720  at the second holding portion can be placed into the recess portion  725 . It is, thereby, possible to prevent formation of irregularities on the outer face  701   b  ( 702   b ) of the outside steel plate  701  ( 702 ) by the second holding portion  721   b.    
     INDUSTRIAL APPLICABILITY 
     The present invention is able to reduce a load which is applied to each one of the bars. Thus, even where a load of an accessory received by the SC structure is relatively great, the accessory can be attached to any given position. 
     According to the present invention, stress resulting from the load of the accessory is allowed to act on a tie bar via an attachment plate. Further, it is possible to easily locate an attachment position of the accessory and reduce a load applied to each one of the tie bars on attachment of the accessory, 
     The accessory attachment structure of the present invention can be increased in rigidity by a simple and lightweight structure and also attach an accessory after confirmation is made for strength of an attachment position. 
     In the design system of the SC structure and the design method of the SC structure of the present invention, as compared with a conventional design method of the SC structure, a stud can be evaluated rationally for the load-bearing capacity thereof by reviewing a method determining an effective projection area in cone failure. 
     In the SC structure of the present invention, a plurality of studs are provided by being arranged in a zigzag form, thus making it possible to evaluate each of the studs as an independent stud. The stud can be evaluated rationally for the load-bearing capacity, as compared with a case where a plurality of studs are arranged and disposed vertically and transversely (where they are arranged in a lattice form). 
     According to the construction method of the SC structure and the SC structure of the present invention, it is possible to set a plurality of attachment positions at which a load applied to each one of the studs can be kept low while a position of the stud is easily confirmed and also attachment device can be installed at the attachment position. It is thereby possible to attach and construct an accessory in a state that a load applied to each one of the studs is reliably kept low. As compared with a conventional case, it is possible to reduce the time necessary for constructing the accessory and also the time necessary for designing the attachment position of the accessory. 
     In the SC structure of the present invention, a shaft portion is inserted through a through-hole formed on an outside steel plate, and a pair of holding portions installed integrally at this shaft portion are used to hold the outside steel plate between them, thereby fixing a stud. It is therefore possible to locate a position of the stud from outside of the outside steel plate by means of one holding portion installed on an outer face of the outside steel plate. Accordingly, on attachment of an accessory, a position of the stud can be easily located by means of one holding portion. It is therefore possible to reduce the time necessary for constructing the accessory and also the time necessary for designing an attachment position of the accessory. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               10 : SC structure (steel plate-reinforced concrete structure) 
               11 : outside steel plate 
               12 : bar 
               13 : tie bar 
               14 : stud 
               15 : concrete 
               20 : piping support 
               22 : piping support 
               21 : attachment face 
               21   a : attachment face 
               21   b : attachment face 
               25 : piping 
               30 : attachment plate 
               33 : attachment plate 
               35 : attachment plate 
               36 : attachment plate 
               37 : attachment plate 
               38 : attachment plate 
               40 : attachment plate 
               45 : attachment plate 
               31 : accessory joint face 
               32 : steel plate joint face 
               201 : SC structure (steel plate-reinforced concrete structure) 
               202 : outside steel plate 
               203 : bar 
               204 : concrete 
               205 : tie bar 
               206 : stud 
               208 : piping support (accessory) 
               209 : attachment plate 
               211 : nut 
               212 : bolt 
               214 : internal thread hole (internal thread portion) 
               217 : internal thread hole (internal thread portion) 
               218 : bolt 
               220 : external thread portion 
               225 : piping 
               310 : accessory attachment structure 
               310 A: accessory attachment structure 
               310 B: accessory attachment structure 
               310 C: accessory attachment structure 
               310 D: accessory attachment structure 
               311 : SC structure (steel plate-reinforced concrete structure) 
               312 : outside steel plate 
               313 : outside steel plate 
               314 : concrete 
               315 : tie bar 
               316 : rib 
               317 : inner steel plate 
               318 : rib 
               319 : rib 
               312 : duct (long object) 
               322 : support member 
               323 : attachment plate 
               401 : concrete 
               402 : stud 
               402   a : shaft portion 
               402   b : head 
               403 : outside steel plate 
               404 : outside steel plate 
               405 : steel plate frame 
               406 : tie bar 
               407 : accessory 
               407   a : piping support 
               407   b : attachment plate 
               408 : piping 
               410 : SC structure (steel plate-reinforced concrete structure) 
               411 : structure condition input device 
               412 : body load-calculating device 
               413 : reference load-calculating device 
               414 : load ratio-calculating device 
               415 : storage device 
               416 : effective projection area-calculating device 
               417 : load-calculating device 
               420 : design system of SC structure 
               501 : concrete 
               502 : stud 
               502   a : shaft portion 
               502   b : head 
               503 : outside steel plate 
               504 : outside steel plate 
               505 : steel plate frame 
               506 : tie bar 
               507 : accessory 
               507   a : piping support 
               507   b : attachment plate 
               508 : piping 
               510 : SC structure (steel plate-reinforced concrete structure) 
           
         
         Ac: effective projection area (projection plane)
         602 : piping     610 : SC structure (steel plate-reinforced concrete structure)     611 : outside steel plate     611   a : inner face     611   b : outer face     612 : outside steel plate     612   a : inner face     612   b : outer face     613 : steel plate frame     614 : tie bar     615 : stud     615   a : shaft portion     615   b : head     616 : concrete     617 : accessory     617   a : piping support     617   b : attachment plate     618 : attachment device     619 : raised portion     620 : locking portion (engagement recess portion)     701 : outside steel plate     701   a : inner face     701   b : outer face     702 : outside steel plate     702   a : inner face     702   b : outer face     703 : steel plate frame     704 : tie bar     705 : stud     706 : concrete     707 : accessory     707   a : piping support     707   b : attachment plate     708 : piping     709 A: SC structure (steel plate-reinforced concrete structure)     709 B: SC structure (steel plate-reinforced concrete structure)     710 : shaft portion     711 : first holding portion (other holding portion)     712 : head     713 : through-hole     714 : second holding portion (one holding portion)     715 : AR machine     716 : positioning portion     717 : AR main body     718 : cutter head     719 : working head     720 : stud     721 : bolt     721   a : shaft portion     721   b : head (second holding portion, one holding portion)     722 : nut (first holding portion, other holding portion)     723 : nut     724 : nut     725 : recess portion