Patent Publication Number: US-9422717-B2

Title: Column structure and base member

Description:
TECHNICAL FIELD 
     The present invention relates to a column structure with a column member joined to the upper side of a base member, and to a base member that has an upper side for joining to a column member. 
     BACKGROUND ART 
     Japanese Patent Application Publication (JP-B) No. H6-19147 discloses a column base structure. In this column base structure, a base plate is joined to anchor bolts that are buried in a concrete foundation. A column is joined to the base plate, and the center of a projected outline of the column with respect to the horizontal plane is offset with respect to the center of a projected outline of the base plate with respect to the horizontal plane. In this column base structure, an out-of-plane deformation prevention means is provided to the base plate on the opposite side to the side to which the column is offset. The out-of-plane deformation prevention means is configured by washers, anchor bolts, or ribs. When bending moment arises in the column, the out-of-plane deformation prevention means prevents the base plate from undergoing out-of-plane deformation so as to deform such that the upper face projects out. 
     In the above column base structure, the column is offset and joined to the base plate, necessitating the out-of-plane deformation prevention means. The column base structure becomes more complicated as a result, leaving room for improvement. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     In consideration of the above circumstances, an object of the present invention is to obtain a column structure and a base member capable of raising column seat bending strength with a simple configuration. 
     Solution to Problem 
     A column structure of a first aspect of the present invention includes: a column member that is integrally provided with a flange at each of two width direction sides of a web; a base member that has the column member joined to an upper side of the base member; a first anchor member including a lower end side that is fixed to a foundation, and including an upper end side to which the base member is fixed at one width direction end side of the web, or at one width direction end side of the flange; and a second anchor member including a lower end side that is fixed to the foundation, and including an upper end side to which the base member is fixed at the other width direction end side of the web, or at the other width direction end side of the flange, the second anchor member having higher tensile strength than the first anchor member. 
     A column structure of a second aspect of the present invention is the column structure of the first aspect, wherein a shaft diameter of the second anchor member is formed larger than a shaft diameter of the first anchor member. 
     A column structure of a third aspect of the present invention is the column structure of the first aspect, wherein the second anchor member is formed from a material with higher tensile strength than the first anchor member material. 
     A column structure of a fourth aspect of the present invention is the column structure of the first aspect, wherein there are a greater number of the second anchor member formed than that of the first anchor member. 
     A column structure of a fifth aspect of the present invention is the column structure of the first aspect, wherein the first anchor member or the second anchor member includes: a first anchor bolt including an upper end side to which the base member is fixed at the opposite side of the flange to the web side; and a second anchor bolt including an upper end side to which the base member is fixed further toward the web width direction inside than the first anchor bolt, and that is disposed closer to the flange than the first anchor bolt. 
     A column structure of a sixth aspect of the present invention is the column structure of the first aspect, wherein the first anchor member is disposed at the inside of a building, and the second anchor member is disposed at the outside of the building. 
     A column structure of a seventh aspect of the present invention includes: a column member that is integrally provided with a flange at each of two width direction sides of a web; a base member that has the column member joined to an upper side of the base member, with a center position of the column member offset in the web width direction, or in the flange width direction, with respect to a center position of the base member; a first anchor member including a lower end side that is fixed to a foundation, and including an upper end side to which the base member is fixed at one width direction end side of the web; and a second anchor member including a lower end side that is fixed to the foundation, and including an upper end side to which the base member is fixed at the other width direction end side of the web, or at the other width direction end side the flange, the second anchor member having equivalent tensile strength to the first anchor member. 
     A column structure of an eighth aspect of the present invention is the column structure of the seventh aspect, wherein: the first anchor member upper end side is fixed to the base member at the opposite side of the flange to the web side, and the second anchor member upper end side is fixed to the base member at the web side of the flange. 
     A column structure of a ninth aspect of the present invention is the column structure of either the first aspect or the seventh aspect, wherein the base member includes a cutaway portion including a portion along the web that is cut away. 
     A column structure of a tenth aspect of the present invention is the column structure of either the first aspect or the seventh aspect, wherein the base member includes: a first base member that has one of the flanges joined to an upper side of the first base member, and that has the first anchor member upper end side fixed to the first base member; and a second base member that has the other of the flanges joined to an upper side of the second base member, and that has the second anchor member upper end side fixed to the second base member, with the second base member provided at a separation to the first base member. 
     A base member of an eleventh aspect of the present invention includes: a base body that has an upper side for joining to a column member integrally provided with a flange at each of two width direction sides of a web; a first fixing portion that is fixed to an upper end side of a first anchor member, the first anchor member being provided to the base body at one width direction end side of the web, or at one width direction end side of the flange, and including a lower end side that is fixed to a foundation; and a second fixing portion that is fixed to an upper end side of a second anchor member, the second anchor member being provided to the base body at the other width direction end side of the web, or at the other width direction end side of the flange, including a lower end side that is fixed to the foundation, and having higher tensile strength than the first anchor member. 
     A base member of a twelfth aspect of the present invention includes: a base body that has an upper side for joining to a column member integrally provided with a flange at each of two width direction sides of a web, with a center position of the column member offset in the web width direction, or in the flange width direction; a first fixing portion that is fixed to an upper end side of a first anchor member, the first anchor member being provided to one web width direction end side of the base body and including a lower end side that is fixed to a foundation; a second fixing portion that is fixed to an upper end side of a second anchor member, the second anchor member being provided to the web width direction other end side of the base body and including a lower end side that is fixed to the foundation, and having equivalent tensile strength to the first anchor member. 
     A base member of a thirteenth aspect of the present invention is the base member of either the eleventh aspect or the twelfth aspect, wherein the base body includes a cutaway portion including a portion along the web that is cut away. 
     A base member of a fourteenth aspect of the present invention is the base member of either the eleventh aspect or the twelfth aspect, wherein the base body includes: a first base body that has one of the flanges joined to an upper side of the first base body, and that has the first anchor member upper end side fixed to the first base body; and a second base body that has the other of the flanges joined to an upper side of the second base body, and that has the second anchor member upper end side fixed to the second base body, with the second base body provided at a separation to the first base body. 
     Advantageous Effects of Invention 
     In the column structure of the first aspect of the present invention, the column member that is integrally provided with the flanges at each of two width direction sides of the web is joined to the upper side of the base member. The lower end sides of the first anchor member and the second anchor member are fixed to the foundation, and the base member is fixed to the upper end sides of the first anchor member and the second anchor member. 
     The upper end side of the first anchor member is fixed to the base member at one width direction end side of the web, or at one width direction end side of the flange. The upper end side of the second anchor member is fixed to the base member at the other width direction end side of the web, or at the other width direction end side of the flange, and the tensile strength of the second anchor member is higher than the tensile strength of the first anchor member. For example, when horizontal direction force acts on the column member from the other end side toward the one end side of the base member, a larger vertical direction tensile axial force arises at the other end side of the base member than at the one end side of the base member. Such a large tensile axial force is effectively suppressed by the second anchor member that has higher tensile strength. The column seat bending strength of the column structure can accordingly be raised by the simple configuration in which the tensile strength of the second anchor member is raised. 
     In the column structure of the second aspect of the present invention, the shaft diameter of the second anchor member is formed larger than the shaft diameter of the first anchor member. The tensile strength of the second anchor member can accordingly be raised, and the column seat bending strength of the column structure can be raised, by the simple configuration in which the shaft diameter is increased. 
     In the column structure of the third aspect of the present invention, the second anchor member is formed from a material with higher tensile strength than the first anchor member material. The tensile strength of the second anchor member can accordingly be raised, and the column seat bending strength of the column structure can be raised, by the simple configuration in which a material with higher tensile strength is employed. 
     In the column structure of the fourth aspect of the present invention, there is a greater number of the second anchor member formed than that of the first anchor member. The tensile strength of the second anchor member can accordingly be raised, and the column seat bending strength of the column structure can be raised, by the simple configuration in which the number of the second anchor member is increased. 
     In the column structure of the fifth aspect of the present invention, the first anchor member or the second anchor member includes the first anchor bolt and the second anchor bolt. The upper end side of the first anchor bolt is fixed to the base member at the opposite side of the flange to the web side. The upper end side of the second anchor bolt is fixed to the base member further toward the web width direction inside than the first anchor bolt. Since the second anchor bolt is disposed closer to the flange than the first anchor bolt, the distance between the column member and the second anchor bolt is reduced. The thickness of the base member is determined by the tensile strength of the second anchor bolt and the distance between the second anchor bolt and the column member. The thickness of the base member can accordingly be reduced due to reducing the distance between the second anchor bolt and the column member. 
     In the column structure of the sixth aspect of the present invention, the first anchor bolt is disposed at the inside of the building, and the second anchor member is disposed at the outside of the building. For example, when horizontal direction force acts on the column member from the building outside toward the building inside, a larger vertical direction tensile axial force arises in the second anchor member that is at the building outside. Such a large tensile axial force is effectively suppressed by the second anchor member that has high tensile strength. The column seat bending strength of the column structure can accordingly be raised by the simple configuration in which the strength of the second anchor member is raised. 
     In the column structure of the seventh aspect of the present invention, the column member that is integrally provided with the flange at each of two width direction sides of the web is joined to the upper side of the base member. The lower end sides of the first anchor member and the second anchor member are fixed to the foundation, and the base member is fixed to the upper end sides of the first anchor member and the second anchor member. 
     The first anchor member and the second anchor member have equivalent tensile strength to one another, the upper end side of the first anchor member is fixed to the one end side of the base member, and the upper end side of the second anchor member is fixed to the other end side of the base member. The center position of the column member is offset in the web width direction, or in the flange width direction, thereby reinforcing the base member with the column member at the offset location of the column member. For example, when horizontal direction force acts on the column member from the opposite side to the offset direction of the column member, a large vertical direction tensile axial force arises in the column member at the base member at the column member offset location. Such a large tensile axial force is effectively suppressed by the reinforced location of the base member where the column member is offset. The column seat bending strength of the column structure can accordingly be raised by the simple configuration in which the column member is offset and joined to the base member. 
     In the column structure of the eighth aspect of the present invention the second anchor member upper end side is fixed to the base member at the web side of the flange, thereby enabling a location on the opposite side of the flange to the web side to be omitted at the other end side of the base member. The center position of the column member can accordingly be simply offset with respect to the center position of the base member, since the center position of the base member is moved toward the one end side of the base member with respect to the center position of the column member. 
     The column member of the ninth aspect of the present invention the base member includes the cutaway portion, thereby enabling a location of the base member corresponding to the cutaway to be omitted, enabling a reduction in weight of the base member. 
     In the column structure of the tenth aspect of the present invention, the base member includes the first base member that is joined to one of the flanges and the second base member that is joined to the other of the flanges, and the first base member and the second base member are at a separation to each other. A location of the base member between the first base member and the second base member can accordingly be omitted, reducing the weight of the base member. 
     In the base member of the eleventh aspect of the present invention the column member that is integrally provided with the flange at each of two width direction sides of the web is joined to the upper side of the base body. The lower end sides of the first anchor member and the second anchor member are fixed to the foundation, and the upper end side of the first anchor member is fixed to the first fixing portion of the base body, and the upper end side of the second anchor member is fixed to the second fixing portion of the base body. 
     The upper end side of the first anchor member is fixed to the first fixing portion at one width direction end side of the web, or at one width direction end side of the flange. The upper end side of the second anchor member is fixed to the second fixing portion of the base body at the web other width direction end side, or at the flange other width direction end side, and the tensile strength of the second anchor member is higher than the tensile strength of the first anchor member. For example, when horizontal direction force acts on the column member from the other end side toward the one end side of the base body, a larger vertical direction tensile axial force arises on the column member at the other end side than at the one end side of the base body. Such a large tensile axial force is effectively suppressed by the second anchor member that is fixed to the second fixing portion and has high tensile strength. The column seat bending strength of a column structure can accordingly be raised by the simple configuration in which the second anchor member with high tensile strength is fixed to the second fixing portion of the base body. 
     In the base member of the twelfth aspect of the present invention, the column member that is integrally provided with the flanges at each of two width direction sides of the web is joined to the upper side of the base body. The lower end sides of the first anchor member and the second anchor member are fixed to the foundation, and the upper end side of the first anchor member is fixed to the first fixing portion of the base body, and the upper end side of the second anchor member is fixed to the second fixing portion of the base body. 
     The first anchor member and the second anchor member have equivalent tensile strength to one another, the upper end side of the first anchor member is fixed to the first fixing portion of the base body, and the upper end side of the second anchor member is fixed to the second fixing portion of the base body. The center position of the column member is offset in the web width direction, or in the flange width direction, and the base body is reinforced by the column member at the offset location of the column member. For example, when horizontal direction force acts on the column member from the opposite side to the offset direction of the column member, a large vertical direction tensile axial force arises on the column member at the base body at the offset location of the column member. Such a large tensile axial force is effectively suppressed by the location of the base body reinforced by the offset column member. The column seat bending strength of the column structure can accordingly be raised by the simple configuration in which the column member is joined to the base body at an offset. 
     In the base member of the thirteenth aspect of the present invention, the base body includes the cutaway portion, thereby enabling a location of the base body corresponding to the cutaway to be omitted, and reducing the weight of the base body. 
     In the base member of the fourteenth aspect of the present invention, the base body includes the first base body that is joined to the one of the flanges, and the second base body that is joined to the other of the flanges. The first base body and the second base body are disposed at a separation to each other. A location of the base member between the first base body and the second base body can accordingly be omitted, reducing the weight of the base member. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-section of a column structure and base member according to a first exemplary embodiment of the present invention, as viewed along a flange width direction (taken along line A-A in  FIG. 2 ). 
         FIG. 2  is a plan view of a column structure and a base member according to the first exemplary embodiment of the present invention. 
         FIG. 3  is a schematic side view of a building applied with a column structure and a base member according to the first exemplary embodiment. 
         FIG. 4  is an enlarged side view of relevant portions of the building illustrated in  FIG. 3 . 
         FIG. 5  is a drawing illustrating a relationship between axial force of a column member and column seat bending strength in a column structure and a base member according to the first exemplary embodiment. 
         FIG. 6  is a plan view corresponding to  FIG. 2  of a column structure and a base member according to a second exemplary embodiment of the present invention. 
         FIG. 7  is a plan view corresponding to  FIG. 2  of a column structure and a base member according to a third exemplary embodiment of the present invention. 
         FIG. 8  is a plan view corresponding to  FIG. 2  of a column structure and a base member according to a fourth exemplary embodiment of the present invention. 
         FIG. 9  is a plan view corresponding to  FIG. 2  of a column structure and a base member according to a fifth exemplary embodiment of the present invention. 
         FIG. 10  is a plan view corresponding to  FIG. 2  of a column structure and a base member according to a sixth exemplary embodiment of the present invention. 
         FIG. 11  is a plan view corresponding to  FIG. 2  of a column structure and a base member according to a seventh exemplary embodiment of the present invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     First Exemplary Embodiment 
     Explanation follows regarding a column structure and a base member according to a first exemplary embodiment of the present invention, with reference to  FIG. 1  to  FIG. 5 . Note that in the present exemplary embodiment an H-section structural steel column (H-section steel column) is employed as a column member, and in the drawings the arrow WH direction indicates a width direction of a web of the column member, and the arrow FH direction indicates a width direction of flanges of the column member as appropriate. The arrow UP direction indicates upwards. 
     Column Structure and Base Member Configuration 
     As illustrated in  FIG. 1  and  FIG. 2 , a column structure  10  according to the present exemplary embodiment is placed on a foundation  12 . The foundation  12  is, for example, concrete, and an upper face of the foundation  12  is formed as a horizontal and flat plane shape. Although not illustrated in the drawings, reinforcement is laid inside the foundation  12 , raising the strength of the foundation  12 . 
     Mortar  14  is provided as a fixing member on the upper surface of the foundation  12 . The mortar  14  is formed, for example, in a rectangular shape in plan view. 
     A base member  16  is fixed to an upper face of the mortar  14 . The base member  16  is provided with a base plate  16 A, as a base body. The mortar  14  is disposed across the entire lower side of the base plate  16 A. The base plate  16 A is configured in a rectangular flat plate shape with its length direction along the arrow WH direction and its short direction along the arrow FH direction. More specifically, the base plate  16 A is formed from a metal material, for example SN490B hot-rolled structural steel plate for construction according to Japanese Industrial Standard (JIS) specification G3136, or cast steel. 
     Two first fixing holes, a first fixing hole  18 A, a first fixing hole  18 B, and two second fixing holes, a second fixing hole  18 C and a second fixing hole  18 D are provided as first fixing portions at one length direction end portion of the base plate  16 A, illustrated on the right hand side in  FIG. 1  and  FIG. 2 . The first fixing hole  18 A and the first fixing hole  18 B are provided at intermediate portions in the base plate  16 A short direction. The second fixing hole  18 C and the second fixing hole  18 D are provided at both end portions in the base plate  16 A short direction. The first fixing hole  18 A, the first fixing hole  18 B, the second fixing hole  18 C and the second fixing hole  18 D are formed as circular shaped through holes having the same diameter in plan view. 
     The position of the center axis of the first fixing hole  18 A and the position of the center axis of the first fixing hole  18 B are aligned with each other along the arrow FH direction. The position of the center axis of the second fixing hole  18 C and the position of the center axis of the second fixing hole  18 D are aligned with each other along the arrow FH direction. In addition, the positions of the center axes of the second fixing hole  18 C and the second fixing hole  18 D are configured more toward a length direction central portion of the base plate  16 A so as to be further toward the arrow WH direction inside than the positions of the center axes of the first fixing hole  18 A and the first fixing hole  18 B. Moreover, the position of the center axis of the second fixing hole  18 C is further to the arrow FH outside than the position of the center axis of the first fixing hole  18 A. The position of the center axis of the second fixing hole  18 D is further to the arrow FH direction outside than the position of the center axis of the first fixing hole  18 B. 
     The other length direction end portion of the base plate  16 A illustrated on the left hand side in  FIG. 1  and  FIG. 2  is provided with two first fixing holes, a first fixing hole  20 A and a first fixing hole  20 B and two second fixing holes, a second fixing hole  20 C and a second fixing hole  20 D, respectively serving as second fixing portions. The first fixing hole  20 A and the first fixing hole  20 B are provided at a short direction intermediate portion of the base plate  16 A. The second fixing hole  20 C and the second fixing hole  20 D are provided at both end portions in the base plate  16 A short direction. The second fixing hole  20 C and the second fixing hole  20 D are formed as circular shaped through holes having the same diameter in plan view, and are configured with the same diameter as the first fixing holes  18 A to  18 D. The first fixing hole  20 A and the first fixing hole  20 B are formed as circular shaped through holes having the same diameter in plan view, and are configured with a larger diameter than the second fixing hole  20 C and the second fixing hole  20 D in the present exemplary embodiment. In other words, the diameters of the first fixing hole  20 A and the first fixing hole  20 B are formed larger than the diameters of the second fixing hole  20 C and the second fixing hole  20 D. 
     The position of the center axis of the first fixing hole  20 A and the position of the center axis of the first fixing hole  20 B are aligned with each other along the arrow FH direction. The position of the center axis of the second fixing hole  20 C and the position of the center axis of the second fixing hole  20 D are aligned with each other along the arrow FH direction. In addition, the positions of the center axes of the second fixing hole  20 C and the second fixing hole  20 D are configured further toward a length direction central portion of the base plate  16 A so as to be further toward the arrow WH direction inside than the positions of the center axes of the first fixing hole  20 A and the first fixing hole  20 B. The position of the center axis of the second fixing hole  20 C is further to the arrow FH direction outside than the position of the center axis of the first fixing hole  20 A. Moreover, the position of the center axis of the second fixing hole  20 D is further toward the arrow FH direction outside than the position of the center axis of the first fixing hole  20 B. 
     The position of the center axis of the first fixing hole  20 A is aligned with the position of the center axis of the first fixing hole  18 A along the arrow WH direction, and the position of the center axis of the first fixing hole  20 B is aligned with the position of the center axis of the first fixing hole  18 B along the arrow WH direction. The position of the center axis of the second fixing hole  20 C is aligned with the position of the center axis of the second fixing hole  18 C along the arrow WH direction, and the position of the center axis of the second fixing hole  20 D is aligned with the position of the center axis of the second fixing hole  18 D along the arrow WH direction. 
     The base plate  16 A is thereby provided with the four fixing holes of the first fixing hole  18 A, the first fixing hole  18 B, the second fixing hole  18 C, and the second fixing hole  18 D, and the four fixing holes of the first fixing hole  20 A, the first fixing hole  20 B, the second fixing hole  20 C, and the second fixing hole  20 D, to give a total of eight fixing holes. 
     As illustrated in  FIG. 1  and  FIG. 2 , indented portions  22  are formed to the lower face of the base plate  16 A at the periphery of each of the eight fixing holes of the first fixing hole  18 A to the second fixing hole  20 D; the horizontal direction upper face (bottom face of the indented portions  22 ) of each of the indented portions  22  is configured with a flat plane shape. The indented portions  22  are formed in substantially triangular shapes in plan view, and gradually widen on progression toward the outer peripheral side of the base plate  16 A, with the indented portions  22  open to the outside of the outer periphery of the base plate  16 A. At base plate  16 A center side portions, the vertical direction peripheral face of each of the indented portions  22  is configured in the same plane as the inner face of the respective fixing holes of the first fixing hole  18 A to the second fixing hole  20 D. The mortar  14  fills the whole of the indented portions  22 , and the base plate  16 A is fixed by the mortar  14 . 
     A first anchor member is fixed to the foundation  12  at each of the first fixing portions of the base member  16 , and a second anchor member is fixed to the foundation  12  at each of the second fixing portions. The first anchor members include first anchor bolts (anchor locks)  24  and second anchor bolts (anchor locks)  24 . The second anchor members include first anchor bolts (anchor locks)  28  and second anchor bolts (anchor locks)  26 . 
     The first anchor bolts  24  and the second anchor bolts  24  of the first anchor members are each equipped with a circular rod shaped anchor body  24 A, with the anchor body  24 A disposed with its axial direction along the up-down direction. Except for an upper end portion  24 C, most of the anchor body  24 A, including a lower end portion  24 B, pierces through the mortar  14  and is buried in the foundation  12 . The first anchor bolts  28  of the second anchor members are each equipped with a circular rod shaped anchor body  28 A, with the anchor body  28 A disposed with its axial direction along the up-down direction. Except for an upper end portion  28 C, most of the anchor body  28 A, including a lower end portion  28 B, pierces through the mortar  14  and is buried in the foundation  12 . The second anchor bolts  26  of the second anchor members are each equipped with a circular rod shaped anchor body  26 A, with the anchor body  26 A disposed with its axial direction along the up-down direction. Except for an upper end portion  26 C, most of the anchor body  26 A, including a lower end portion  26 B, pierces through the mortar  14  and is buried in the foundation  12 . 
     A male thread is provided to the lower end portion  24 B of the anchor body  24 A of each of the first anchor bolts  24  and the second anchor bolts  24  of the first anchor members. Two nuts, a nut  24 D and a nut  24 E, are provided screwed onto the male thread in the up-down direction. A circular ring flat plate shaped fixing plate  24 F configuring an anchor portion is interposed between the nut  24 D and the nut  24 E, so as to project further to the outside than the shaft diameter of the anchor body  24 A. The fixing plate  24 F is fixed by tightening of the nut  24 D and the nut  24 E. The nut  24 D, the nut  24 E and the fixing plate  24 F are buried in the foundation  12 , and are configured to prevent the first anchor bolt  24  from being pulled out. 
     The upper end portions  24 C of the anchor bodies  24 A are respectively configured so as to pierce through and project out from the first fixing hole  18 A, the first fixing hole  18 B, the second fixing hole  18 C, and the second fixing hole  18 D of the base plate  16 A. A male thread is provided to the upper end portion  24 C, and a nut  24 G for fixing the base plate  16 A is screwed onto the male thread. A circular ring flat plate shaped washer  24 H is interposed between the base plate  16 A and the nut  24 G. 
     In the first anchor bolts  28  of the second anchor members, two nuts, a nut  28 D and a nut  28 E, are provided screwed onto a male thread provided to the lower end portion  28 B of the anchor body  28 A. A circular ring flat plate shaped fixing plate  28 F is interposed between the nut  28 D and the nut  28 E. The fixing plate  28 F is fixed by tightening of the nut  28 D and the nut  28 E. The nut  28 D, the nut  28 E and the fixing plate  28 F are buried in the foundation  12 , and are configured to prevent the first anchor bolt  28  from being pulled out. The upper end portions  28 C of the anchor bodies  28 A are respectively configured so as to pierce through and project out from the first fixing hole  20 A and the first fixing hole  20 B serving as second fixing portions of the base plate  16 A. A male thread is provided to the upper end portion  28 C, and a nut  28 G for fixing the base plate  16 A is screwed onto the male thread. A circular ring flat plate shaped washer  28 H is interposed between the base plate  16 A and the nut  28 G. 
     Similarly, in the second anchor bolts  26  of the second anchor members, two nuts, a nut  26 D and a nut  26 E, are screwed onto a male thread provided to the lower end portion  26 B of the anchor body  26 A. A circular ring flat plate shaped fixing plate  26 F is interposed between the nut  26 D and the nut  26 E. The fixing plate  26 F is fixed by tightening of the nut  26 D and the nut  26 E. The nut  26 D, the nut  26 E and the fixing plate  26 F are buried in the foundation  12 , and are configured to prevent the second anchor bolt  26  from being pulled out. The upper end portions  26 C of the anchor bodies  26 A are respectively configured so as to pierce through and project out from the second fixing hole  20 C and the second fixing hole  20 D of the base plate  16 A. A male thread is provided to the upper end portion  26 C, and a nut  26 G for fixing the base plate  16 A is screwed onto the male thread. A circular ring flat plate shaped washer  26 H is interposed between the base plate  16 A and the nut  26 G. 
     In the present exemplary embodiment, the first anchor bolts  24  and the second anchor bolts  24  of the first anchor members and the second anchor bolts  26  of the second anchor members are formed with the same diameters as each other, and with the same axial direction lengths. The first anchor bolts  28  of the second anchor members are for example configured with a larger axial diameter than the first anchor bolts  24  of the first anchor members, and are formed with high tensile strength. More precisely, the first anchor bolts  24 , the second anchor bolts  24 , the first anchor bolts  28  and the second anchor bolts  26  are for example formed from a carbon steel material having a tensile strength such as 400 N/mm 2 , or 490 N/mm 2  as defined by JIS specification G3138. An anchor bolt formed from stainless steel having a tensile strength of 520 N/mm 2  as defined by JIS specification G4321 may also be employed therefor. The diameter of the first anchor bolts  24 , the second anchor bolts  24 , and the second anchor bolts  26  is for example set at 30 mm (“M30” in screw terms), and the diameter of the first anchor bolts  28  is for example set at 36 mm (“M36” in screw terms). 
     At a center portion on the upper face of the base plate  16 A, a steel column  30  is provided as a column member, with its length direction extending in the up-down direction. A lower end of the steel column  30  is joined, for example by arc welding, to the upper face of the base plate  16 A. 
     The steel column  30  is, in the present exemplary embodiment, formed from H-section steel, and includes a web  30 A and a pair of flanges  30 B that are integrally provided at the two width direction ends of the web  30 A. The web  30 A of the steel column  30  is formed in an elongated rectangular flat plate shape with its width direction running along the arrow WH direction and its length direction running along the arrow UP direction. The pair of flanges  30 B are each formed in an elongated rectangular flat plate shape with their width directions running along the arrow FH direction and with their length directions running along the arrow UP direction. The two ends of the web  30 A are integrally joined to width direction central portions of the flanges  30 B. The steel column  30  is, for example formed from a rolled structural steel for use in construction as defined by JIS specification G3136, a rolled steel for use in welded structures as defined by JIS specification G3106, or a rolled steel for use in general purpose structures as defined by JIS specification G3101. 
     Note that normally there are plural of the column structures  10  provided in a building. Although not illustrated in the drawings, foundation beams span across between lower end portions of the steel columns  30  of adjacent column structures  10 , so as to arrange the main foundation beam layout. 
     Building Structure 
       FIG. 3  is a schematic side view illustrating a structure of a building constructed using the column structure  10  and the base member  16  according to the present exemplary embodiment.  FIG. 4  is a side view illustrating a structure of relevant portions of the building. 
     In the column structure  10  illustrated on the left hand side in  FIG. 3  and  FIG. 4 , the first fixing hole  18 A, the first fixing hole  18 B, the second fixing hole  18 C and the second fixing hole  18 D (see  FIG. 1  and  FIG. 2 ) serving as the first fixing portions of the base member  16  are disposed on the building inside (on the right hand side). The first anchor bolts  24  and the second anchor bolts  24  serving as the first anchor members are fixed to the base plate  16 A on the building inside. The first fixing hole  20 A, the first fixing hole  20 B, the second fixing hole  20 C and the second fixing hole  20 D (see  FIG. 1  and  FIG. 2 ) serving as the second anchor members of the base member  16  are disposed on the building outside (left hand side). The first anchor bolts  28  and the second anchor bolts  26  serving as the second anchor members are fixed to the base plate  16 A on the building outside. 
     The column structure  10  illustrated on the right hand side in  FIG. 3  and  FIG. 4  is configured so as to be rotated through 180 degrees with respect to the left hand side column structure  10  about a center axial line, not illustrated in the drawings, that runs in the arrow UP direction of the building. Namely, in the right hand side column structure  10 , the first fixing hole  18 A, the first fixing hole  18 B the second fixing hole  18 C, and the second fixing hole  18 D serving as the first fixing portions of the base member  16  are disposed on the building inside (left hand side). The first anchor bolts  24  and the second anchor bolts  24  serving as the first anchor members are fixed to the base plate  16 A on the building inside. The first fixing hole  20 A, the first fixing hole  20 B, the second fixing hole  20 C and the second fixing hole  20 D serving as the second fixing portions of the base member  16  are disposed on the building outside (right hand side). The first anchor bolts  28  and the second anchor bolts  26  serving as the second anchor members are fixed to the base plate  16 A on the building outside. 
     Note that as illustrated in  FIG. 3 , a first beam member  32 , a second beam member  34 , and a third beam member  36  are provided between the left hand side column structure  10  and the right hand side column structure  10  so as to partition each story. One end portion on the left side of the first beam member  32  is joined to the steel column  30  of the left hand side column structure  10  using arc welding or bolt fastening, and the other end portion on the right side of the first beam member  32  is joined to the steel column  30  of the right hand side column structure  10  by similar joining means. In the present exemplary embodiment, an H-section steel beam integrally provided with flanges  32 B at both width direction (arrow UP direction) ends of a web  32 A is employed as the first beam member  32 . Both end portions of the second beam member  34  are similarly joined to the respective steel columns  30  of the left and right side column structures  10 , and both end portions of the third beam member  36  are joined to the respective steel columns  30  of the left and right side column structures  10 . An H-section steel beam with a web  34 A and flanges  34 B is employed for the second beam member  34 , and an H-section steel beam with a web  36 A and flanges  36 B is employed for the third beam member  36 . Note that the first beam member  32 , the second beam member  34 , and the third beam member  36  may also be formed from beam members such as I-section steel beams or square section steel beams. 
     Operation and Advantageous Effects of the First Exemplary Embodiment 
     As illustrated in  FIG. 1  and  FIG. 2 , in the column structure  10  and the base member  16  according to the present exemplary embodiment, the steel column  30  integrally provided with the flanges  30 B at both width direction end portions of the web  30 A is joined to the upper side of the base plate  16 A. The lower end sides of the first anchor members and the second anchor members are fixed to the foundation  12 , and the base plate  16 A is fixed to the upper end sides of the first anchor members and the second anchor members. 
     The upper end sides of the first anchor bolts  24  and the second anchor bolts  24  serving as the first anchor members are fixed to the base plate  16 A at one width direction end side of the web  30 A. The upper end sides of the first anchor bolts  28  and the second anchor bolts  26  serving as the second anchor members are fixed to the base plate  16 A at the other width direction end side of the web  30 A. The tensile strength of the first anchor bolts  28  of the second anchor members is higher than the tensile strength of the first anchor bolts  24  of the first anchor members. 
     As illustrated in  FIG. 1 ,  FIG. 3  and  FIG. 4 , when a force F due to an earthquake or the like acting from the left hand side toward the right hand side in the arrow WH direction (horizontal direction) arises at the outer periphery of the building, at the left hand side column structure  10  of the building on which the force F acts, the greatest tensile axial force St arises at the flange  30 B on the steel column  30  outside. At the right hand side column structure  10  of the building, the greatest compression axial force Sp arises at the flange  30 B on the steel column  30  outside. In the event of an earthquake, the direction of the force F alternates back and forth, such that the tensile axial force St and the compression axial force Sp act alternately at the flange  30 B of the left hand side column structure  10  as the compression axial force Sp and the tensile axial force St act alternately at the flange  30 B of the right hand side column structure  10 . 
       FIG. 5  illustrates a relationship between the axial force (N) arising in the steel column  30  and column seat bending strength (N) in the column structure  10 . As illustrated in  FIG. 5 , the column seat bending strength with respect to compression axial force arising in the steel column  30  is high, however the column seat bending strength with respect to tensile axial force in the steel column  30  is weak. There is accordingly a need to increase the column seat bending strength with respect to tensile axial force. Note that the region B surrounded by the broken line is the range of axial forces arising in a typical building, and there is a tendency toward weak column seat bending strength with respect to tensile axial force even within the region B. 
     In the column structure  10  and the base member  16  according to the present exemplary embodiment, the first fixing hole  20 A and the first fixing hole  20 B serving as the second fixing portions in the base plate  16 A on the building outside are configured with enlarged diameters. In addition, the first anchor bolts  28  serving as second anchor members configured with greater tensile strength than the first anchor members are provided through the first fixing hole  20 A and the first fixing hole  20 B. Namely, second fixing portions of the base plate  16 A are provided with the second anchor members that have high tensile strength, the second anchor members thereby effectively suppressing a large tensile axial force from acting in the steel column  30 . The column seat bending strength of the column structure  10  can accordingly be raised by the simple configuration in which the tensile strength of the second anchor members, and in particular of the first anchor bolts  28 , is raised. 
     As illustrated in  FIG. 1  and  FIG. 2 , in the column structure  10  and the base member  16  according to the present exemplary embodiment the shaft diameter of the first anchor bolts  28  of the second anchor members is formed larger than the shaft diameter of the first anchor bolts  24  of the first anchor members. The tensile strength of the first anchor bolts  28  can accordingly be raised, and the column seat bending strength of the column structure  10  can be raised, by the simple configuration in which the shaft diameter of the first anchor bolts  28  is increased. 
     As illustrated in  FIG. 1 , in the column structure  10  and the base member  16  according to the present exemplary embodiment, the base plate  16 A is fixed to the upper end portions  24 C of the second anchor bolts  24  of the first anchor members provided on the width direction inside of the web  30 A. Similarly, the base plate  16 A is fixed to the upper end portions  26 C of the second anchor bolts  26  of the second anchor members provided on the width direction inside of the web  30 A. As illustrated in  FIG. 1  and  FIG. 2 , the second anchor bolts  24  are brought closer to the flange  30 B of the steel column  30 , to give a small separation distance L between the flange  30 B and the second anchor bolts  24 . There is similarly a small separation distance between the flange  30 B and the second anchor bolts  26 . Explanation here focuses on the first anchor member side only. Increasing the total number of the first anchor bolts  24  and the second anchor bolts  24  provided to the base plate  16 A (or increasing the total number of the holes of the first fixing hole  18 A, the first fixing hole  18 B, the second fixing hole  18 C and the second fixing hole  18 D) necessitates an increase in the thickness (up-down direction thickness dimension) t of the base plate  16 A. 
     The total number of the first anchor bolts  24  and the second anchor bolts  24  provided at the periphery of one of the flanges  30 B of the base plate  16 A is denoted n. In the present exemplary embodiment, n equals 4. The yield tensile strength in the axial direction of the i th  first anchor bolt  24  or the second anchor bolt  24  in the arrow FH direction is denoted Ti. The arrow WH direction separation distance between the center axis of the i th  first anchor bolt  24  or second anchor bolt  24  and the flange  30 B is denoted Li. Moreover, the arrow FH direction dimension of the base plate  16 A (width dimension) is denoted B, the thickness of the base plate  16 A is denoted t, and the yield point of the base plate  16 A material is denoted σ. In this case, the base plate  16 A conforms to the following relationship expression (1). 
     
       
         
           
             
               
                 ∑ 
                 
                   i 
                   = 
                   1 
                 
                 n 
               
               ⁢ 
               TiLi 
             
             ≤ 
             
               
                 B 
                 ⁡ 
                 
                   ( 
                   
                     
                       t 
                       2 
                     
                     / 
                     6 
                   
                   ) 
                 
               
               ⁢ 
               σ 
             
           
         
       
     
     In the above relationship expression, reducing the separation distance Li on the left side reduces the thickness t on the right side. Namely, in the present exemplary embodiment, by actively reducing the separation distance Li, the thickness of the base plate  16 A can be made thinner. The material costs of the base plate  16 A can be reduced, thereby enabling a saving in material costs and manufacturing costs of the column structure  10 . 
     Moreover, in the column structure  10  and the base member  16  according to the present exemplary embodiment, the first anchor bolts  24  of the first anchor members are disposed on the building inside, and the first anchor bolts  28  of the second anchor members are disposed on the building outside. For example, when a tensile axial force arises in the steel column  30 , the larger tensile axial force arises on the building outside of the steel column  30 . The location (on the second fixing portion side) where tensile axial force acts in the base plate  16 A is fixed by the first anchor bolts  28  of the second anchor members that have high tensile strength. The large tensile axial force is thereby suppressed by the high tensile strength first anchor bolts  28 , thereby enabling the column seat bending strength of the column structure  10  to be raised. 
     Moreover, in the column structure  10  and the base member  16  according to the present exemplary embodiment, the indented portions  22  are provided at the base plate  16 A lower side. The mortar  14  fills the indented portions  22 , and the base plate  16 A is anchored to the foundation  12  through the mortar  14 . Thus when horizontal load arises such as during an earthquake, displacement of the base member  16  with respect to the foundation  12  can be suppressed. This thereby enables the shear capacity of the column structure  10  and the base member  16  to be raised since shear stress is suppressed from being transmitted from the steel column  30  to the foundation  12  through the base plate  16 A and the first anchor members and second anchor members. 
     Note that in the column structure  10  and the base member  16  of the present exemplary embodiment, the tensile strength is raised on the other end side with respect to the one end side in the arrow WH direction (web  30 A width direction) of the base plate  16 A illustrated in  FIG. 2 . In the present exemplary embodiment, the tensile strength may be raised on the other end side with respect to one end side in the arrow FH direction (flanges  30 B width direction) of the base plate  16 A. In such cases, the force F acting on the building acts in the arrow FH direction. 
     Moreover, in the present exemplary embodiment the tensile strength is raised by the first fixing hole  20 A and the first fixing hole  20 B of the second fixing portions and the first anchor bolts  28  of the second anchor members. In addition, the diameter of the second fixing hole  20 C and the second fixing hole  20 D of the second fixing portions may be increased, and the shaft diameter of the second anchor bolts  26  may be increased, thereby increasing the overall tensile strength of the second fixing portions and also of the second anchor members. 
     Second Exemplary Embodiment 
     Explanation follows regarding a column structure and base member according to a second exemplary embodiment of the present invention, with reference to  FIG. 6 . Note that in the present exemplary embodiment, as well as in subsequently described exemplary embodiments, configuration that is the same as configuration of the column structure  10  and the base member  16  according to the first exemplary embodiment is appended with the same reference numerals, and repetition of explanation of such configurations is omitted. 
     Column Structure and Base Member Configuration 
     As illustrated in  FIG. 6 , in a column structure  40  and a base member  16  according to the present exemplary embodiment, configuration of a first fixing hole  20 A and a first fixing hole  20 B of second fixing portions, and configuration of first anchor bolts  42  of second anchor members, respectively shown on the left hand side in the drawing, differ from the configuration of the first exemplary embodiment. Other configurations of the column structure  40  and the base member  16  according to the present exemplary embodiment are similar to configuration of the column structure  10  and the base member  16  according to the first exemplary embodiment. 
     More specifically, the first fixing hole  20 A and the first fixing hole  20 B of the column structure  40  and the base member  16  are formed as circular shaped through holes having the same diameter as the first fixing hole  18 A and the first fixing hole  18 B of the first fixing portions. Note that the first fixing hole  20 A and the first fixing hole  20 B are also formed with the same diameter as the second fixing hole  20 C and the second fixing hole  20 D of the second fixing portions and the second fixing hole  18 C and the second fixing hole  18 D of the first fixing portions. 
     The first anchor bolts  42  serving as second anchor members are configured with the same diameter as the first anchor bolts  24 , and are formed from a material with a higher tensile strength than the first anchor bolts  24 . Upper end portions  42 C of the first anchor bolts  42  are provided with a male thread similarly to the upper end portions  24 A of the anchor bolts  24 . Nuts  42 G are screwed onto the male thread of the first anchor bolts  42  that pierce the first fixing hole  20 A and the first fixing hole  20 B with washers, omitted from illustration, interposed. Similarly to the first anchor bolts  24 , lower end sides of the first anchor bolts  42 , omitted from illustration, are provided with double nuts and fixing plates that are fastened by the double nuts. The upper end sides of the first anchor bolts  42  are thereby fixed to the base plate  16 A. 
     For example, when the anchor bolts  24  are formed from a carbon steel material having a tensile strength of 400 N/mm 2  as defined by JIS specification G3138, the first anchor bolts  42  may be formed from a carbon steel material having a tensile strength of 490 N/mm 2 . The first anchor bolts  42  may also be formed from a stainless steel material with a higher tensile strength than the first anchor bolts  24 . 
     Note that in the present exemplary embodiment, the second anchor bolts  26  serving as the second anchor members may be formed from a material with a high tensile strength similarly to the first anchor bolts  42 . The length of the second anchor bolts  42  and the length of the first anchor bolts  24  may differ from each other under the condition that the tensile strength of the first anchor bolts  42  is higher than that of the anchor bolts  24 . 
     Operation and Advantageous Effects of the Second Exemplary Embodiment 
     As illustrated in  FIG. 6 , in the column structure  40  and the base member  16  according to the present exemplary embodiment, the first anchor bolts  42  of the second anchor members are formed from a material with a higher tensile strength than the anchor bolts  24  of the first anchor members. The tensile strength of the second anchor members can accordingly be raised, and column seat bending strength of the column structure  40  can be raised by the simple configuration in which the first anchor bolts  42  are formed from a material having high tensile strength. 
     In addition to the above operation and advantageous effects, the column structure  40  and the base member  16  according to the present exemplary embodiment can obtain similar operation and advantageous effects to those obtained by the column structure  10  and the base member  16  according to the first exemplary embodiment. 
     Third Exemplary Embodiment 
     Explanation follows regarding a column structure and base member according to a third exemplary embodiment of the present invention, with reference to  FIG. 7 . 
     Column Structure and Base Member Configuration 
     As illustrated in  FIG. 7 , in a column structure  50  and a base member  16  according to the present exemplary embodiment, configuration of first fixing portions and first anchor members illustrated on the right hand side in the drawing, and configuration of second fixing portions and second anchor members illustrated on the left hand side in the drawing differ from the configuration of the first exemplary embodiment. Other configurations of the column structure  50  and the base member  16  according to the present exemplary embodiment are similar to configuration of the column structure  10  and the base member  16  according to the first exemplary embodiment. 
     More specifically, the first fixing portions of the column structure  50  and the base member  16  are configured with the first fixing hole  18 A and the first fixing hole  18 B (see  FIG. 1  and  FIG. 2 ) omitted, with two fixing holes, the second fixing hole  18 C and the second fixing hole  18 D. The second anchor bolts  24  serving as the first anchor members are provided to the second fixing hole  18 C and the second fixing hole  18 D respectively. 
     The second fixing portions are configured by two first fixing holes, the first fixing hole  20 A and the first fixing hole  20 B, and two second fixing holes, the second fixing hole  20 C and the second fixing hole  20 D. The first fixing hole  20 A and the first fixing hole  20 B are formed as circular shaped through holes having the same diameter as the second fixing hole  20 C and the second fixing hole  20 D, similarly to the first fixing hole  20 A and the first fixing hole  20 B (see  FIG. 6 ) of the second exemplary embodiment described above. The first fixing hole  20 A and the first fixing hole  20 B are moreover formed with the same diameter as the second fixing hole  18 C and the second fixing hole  18 D of the first fixing portions. First anchor bolts  26  and second anchor bolts  26  serving as second anchor members are provided to the total of four fixing holes, namely the first fixing hole  20 A, the first fixing hole  20 B, the second fixing hole  20 C, and the second fixing hole  20 D. The first anchor bolts  26  are formed with the same diameter and the equivalent tensile strength to the second anchor bolts  26 . Moreover, the first anchor bolts  26  are formed with the same diameter and the equivalent tensile strength to the first anchor bolts  24  of the first anchor members. 
     Namely, in the column structure  50  and the base member  16  according to the present exemplary embodiment, there are a greater number of the first anchor bolts  26  and the second anchor bolts  26  of the second anchor members provided than that of the first anchor members. 
     Operation and Advantageous Effects of the Third Exemplary Embodiment 
     As illustrated in  FIG. 7 , in the column structure  50  and the base member  16  according to the present exemplary embodiment, there are a greater number of the second anchor members provided than that of the first anchor members. The tensile strength of the second anchor members can be raised, and the column seat bending strength of the column structure  50  can be raised, by the simple configuration in which the number (quantity) of the second anchor members is varied. 
     In addition to the above operation and advantageous effects, the column structure  50  and the base member  16  according to the present exemplary embodiment can obtain similar operation and advantageous effects to those obtained by the column structure  10  and the base member  16  according to the first exemplary embodiment. 
     Fourth Exemplary Embodiment 
     Explanation follows regarding a column structure and base member according to a fourth exemplary embodiment of the present invention, with reference to  FIG. 8 . 
     Column Structure and Base Member Configuration 
     As illustrated in  FIG. 8 , in a column structure  60  and a base member  16  according to the present exemplary embodiment, the steel column  30  is joined to the base plate  16 A with a flange  30 B width direction (arrow FH direction) center position Wc of the steel column  30  offset with respect to a flange  30 B width direction center position Bc of the base plate  16 A by a distance Los. Note that the center position Bc is a center position on the upper face of the base plate  16 A, and the center position Wc is a center position on a lower face of the steel column  30 . More specifically, in the present exemplary embodiment one end side of the base plate  16 A on the arrow FH direction upper side is disposed at the outside of a building, omitted from illustration, and the other end side of the base plate  16 A on the arrow FH direction lower side is disposed at the building inside. Namely, the steel column  30  is offset toward the side where the greatest tensile axial force arises. 
     In the present exemplary embodiment, two fixing holes of the first fixing hole  18 A and the first fixing hole  18 B serving as first fixing portions, and two fixing holes of the second fixing hole  18 C and the second fixing hole  18 D are provided on one end side of the base plate  16 A. The center axis positions of the first fixing hole  18 A, the first fixing hole  18 B, the second fixing hole  18 C and the second fixing hole  18 D are aligned with each other along the arrow WH direction, and the first fixing hole  18 A to the second fixing hole  18 D are formed with the same diameter as each other. The first fixing hole  18 A is disposed on the opposite side of the flange  30 B to the web  30 A. The first fixing hole  18 B is disposed further to the web  30 A width direction inside than the first fixing hole  18 A, and is disposed on the web  30 A side of the flange  30 B. The second fixing hole  18 D is disposed on the opposite side of the flange  30 B to the web  30 A. The second fixing hole  18 C is disposed further toward the web  30 A width direction inside than the second fixing hole  18 D, and is disposed on the web  30 A side of the flange  30 B. 
     First anchor bolts  24  serving as first anchor members are provided to the first fixing hole  18 A and the first fixing hole  18 B, and second anchor bolts  24  serving as first anchor members are provided to the second fixing hole  18 C and the second fixing hole  18 D. The first anchor bolts  24  and the second anchor bolts  24  all formed with the same diameter, and are all formed with equivalent tensile strength. 
     Two first fixing holes, a first fixing hole  20 A and a first fixing hole  20 B, and two second fixing holes, a second fixing hole  20 C and a second fixing hole  20 D that serve as second fixing portions are provided on the other end side of the base plate  16 A. The center axis positions of the first fixing hole  20 A, the first fixing hole  20 B, the second fixing hole  20 C and the second fixing hole  20 D are aligned with each other along the arrow WH direction, and the first fixing hole  20 A to the second fixing hole  20 D are formed with the same diameter as each other. The first fixing hole  20 A to the second fixing hole  20 D of the second fixing portions are moreover configured with the same diameter as the first fixing hole  18 A to the second fixing hole  18 D of the first fixing portions. The first fixing hole  20 A is disposed on the opposite side of the flange  30 B to the web  30 A, and the center axis position of the first fixing hole  20 A is aligned with the center axis position of the first fixing hole  18 A in the arrow FH direction. The first fixing hole  20 B is disposed further to the web  30 A width direction inside than the first fixing hole  20 A, and is disposed on the web  30 A side of the flange  30 B. The center axis position of the first fixing hole  20 B is aligned with the center axis position of the first fixing hole  18 B in the arrow FH direction. The second fixing hole  20 D is disposed on the opposite side of the flange  30 B to the web  30 A, and the center axis position of the second fixing hole  20 D is aligned with the center axis position of the second fixing hole  18 D in the arrow FH direction. The second fixing hole  20 C is disposed further toward the web  30 A width direction inside than the second fixing hole  20 D, and is disposed on the web  30 A side of the flange  30 B. 
     First anchor bolts  26  serving as second anchor members are provided to the first fixing hole  20 A and the first fixing hole  20 B, and second anchor bolts  26  serving as second anchor members are provided to the second fixing hole  20 C and the second fixing hole  20 D. The first anchor bolts  26  and the second anchor bolts  26  are all formed with the same diameter and the equivalent tensile strength to each other. The first anchor bolts  26  are moreover formed with the same diameter and the equivalent tensile strength to the first anchor bolts  24 . The first anchor bolts  24 , the second anchor bolts  24 , the first anchor bolts  26  and the second anchor bolts  26  are moreover all provided an equal distance from the center position Bc of the base plate  16 A. 
     Operation and Advantageous Effects of the Fourth Exemplary Embodiment 
     As illustrated in  FIG. 8 , in the column structure  60  and the base member  16  according to the present exemplary embodiment, the steel column  30  with the flanges  30 B integrally provided to both width direction sides of the web  30 A is joined to the upper side of the base plate  16 A. The lower end sides of the first anchor members and the second anchor members are fixed to the foundation  12 , and the base plate  16 A is fixed to the upper end sides of the first anchor members and the second anchor members. 
     The first anchor bolts  24  and the second anchor bolts  24  of the first anchor members, and the first anchor bolts  26  and the second anchor bolts  26  of the second anchor members are formed with the equivalent tensile strength to each other. The upper end sides of the first anchor bolts  24  and the second anchor bolts  24  are fixed to the arrow FH direction one end side of the base plate  16 A, and the upper end sides of the first anchor bolts  26  and the second anchor bolts  26  are fixed to the arrow FH direction other end side of the base plate  16 A. The center position Wc of the steel column  30  is offset with respect to the center position Bc of the base plate  16 A in the flanges  30 B width direction, such that the steel column  30  reinforces the location (the other end side of the base plate  16 A) of the base plate  16 A where the steel column  30  is offset. For example, when force (force F illustrated in  FIG. 1 ,  FIG. 3  and  FIG. 4 ) in the horizontal direction is imparted to the steel column  30  from the opposite side to the offset direction of the steel column  30 , a large tensile axial force in the arrow UP direction arises in the steel column  30  at the location of the base plate  16 A where the steel column  30  is offset. This large tensile axial force is effectively suppressed by the location of the base plate  16 A reinforced by the offset steel column  30 . Accordingly, the column seat bending strength of the column structure  60  can be raised by the simple configuration in which the steel column  30  is joined to the base plate  16 A at an offset even when the first anchor members and the second anchor members have the equivalent tensile strength to each other (even without modification). 
     In addition to the above operation and advantageous effects, the column structure  60  and the base member  16  according to the present exemplary embodiment can obtain similar operation and advantageous effects to the operation and advantageous effects obtained by the column structure  10  and the base member  16  according to the first exemplary embodiment. 
     Note that in the column structure  60  and the base member  16  according to the present exemplary embodiment, configuration may be made such that the center position Bc of the base plate  16 A and the center position Wc of the column member are aligned with each other, with both positions being offset in the arrow WH direction. In such a case, the steel column  30  is offset toward the building outside with respect to the base plate  16 A. The first fixing hole  18 A, the first fixing hole  18 B, the first fixing hole  20 A, and the first fixing hole  20 B are disposed on the building inside, and are provided with the first anchor bolts  24  and the first anchor bolts  26 . Moreover, the second fixing hole  18 C, the second fixing hole  18 D, the second fixing hole  20 C, and the second fixing hole  20 D are disposed on the building outside, and are provided with the second anchor bolts  24  and the second anchor bolts  26 . 
     Fifth Exemplary Embodiment 
     Explanation follows regarding a column structure and base member according to a fifth exemplary embodiment of the present invention, with reference to  FIG. 9 . The present exemplary embodiment is a modified example of the column structure  60  and the base member  16  according to the fourth exemplary embodiment. 
     Column Structure and Base Member Configuration 
     As illustrated in  FIG. 9 , in a column structure  70  and a base member  16  according to the present exemplary embodiment, the first fixing portions are configured by two first fixing holes, the first fixing hole  18 A and the first fixing hole  18 B, disposed on the opposite side of the flange  30 B to the web  30 A. The first fixing hole  18 A and the first fixing hole  18 B are provided with the first anchor bolts  24  serving as first anchor members. 
     The second fixing portions are configured by two second fixing holes, a second fixing hole  20 G and a second fixing hole  20 H, disposed on the web  30 A side of the flange  30 B. The second fixing hole  20 G and the second fixing hole  20 H are provided with the second anchor bolts  26  serving as the second anchor members. The second anchor bolts  26  are formed with the same diameter and the equivalent tensile strength to the first anchor bolts  24 . 
     In the base plate  16 A according to the present exemplary embodiment, the second fixing hole  20 G and the second fixing hole  20 H are disposed on the web  30 A side of the flange  30 B, and a region  16 B on the opposite side of the flange  30 B to the web  30 A is omitted. As a result, the steel column  30  is offset with respect to the base plate  16 A toward the left hand side in the web  30 A width direction (in the arrow WH direction). The side to which the steel column  30  is offset is configured at the building outside. 
     Operation and Advantageous Effects of the Fifth Exemplary Embodiment 
     As illustrated in  FIG. 9 , in the column structure  70  and the base member  16  according to the present exemplary embodiment, the upper end sides of the second anchor bolts  26  serving as the second anchor members are fixed to the base plate  16 A on the web  30 A side of the flange  30 B. The region  16 B of the base plate  16 A that is on the opposite side of the flange  30 B to the web  30 A can be omitted as a result. 
     As a result of omitting the region  16 B of the base plate  16 A, the arrow WH direction center position of the steel column  30  moves toward the other end side of the base plate  16 A with respect to the arrow WH center position of the base plate  16 A. The center position of the steel column  30  can thereby be simply configured so as to be offset with respect to the center position of the base plate  16 A. 
     Moreover, in the column structure  70  and the base member  16  according to the present exemplary embodiment, the region  16 B portion of the base plate  16 A is omitted (a building outside portion of the base plate  16 A is reduced), thereby achieving a reduction in weight of the base plate  16 A. Moreover, since the quantity of material required for manufacture of the base plate  16 A can be reduced, a reduction in manufacturing costs of the column structure  70  and the base member  16  is enabled. 
     Moreover, in the column structure  70  and the base member  16  according to the present exemplary embodiment, the region  16 B of the base plate  16 A on the opposite side of the flange  30 B to the web  30 A is omitted, thereby enabling the steel column  30  to be brought closer to an adjacent boundary. Efficient utilization of the building site is thereby enabled. 
     Sixth Exemplary Embodiment 
     Explanation follows regarding a column structure and base member according to a sixth exemplary embodiment of the present invention, with reference to  FIG. 10 . The present exemplary embodiment is a modified example of the column structure  70  and the base member  16  according to the fifth exemplary embodiment. 
     Column Structure and Base Member Configuration 
     As illustrated in  FIG. 10 , in a column structure  80  according to the present exemplary embodiment, a cutaway portion  16 F and a cutaway portion  16 G are provided to the base plate  16 A of the base member  16 . 
     More specifically, the cutaway portion  16 F is formed by cutting away a portion of the base plate  16 A along the web  30 A on one arrow FH direction end side of the base plate  16 A between the pair of flanges  30 B. The cutaway portion  16 F is configured in a U shape (rectangular shape) open toward the one end side of the base plate  16 A in plan view. 
     The cutaway portion  16 G is formed by cutting away a portion of the base plate  16 A along the web  30 A on the arrow FH direction other end side of the base plate  16 A between the pair of flanges  30 B. In plan view, the cutaway portion  16 G is configured in a U shape (rectangular shape) open toward the other end side of the base plate  16 A symmetrically to the cutaway portion  16 F. 
     A location of the base plate  16 A is provided between the cutaway portion  16 F and the cutaway portion  16 G, with the web  30 A joined to this location. In plan view, the overall base plate  16 A has an H shape in the present exemplary embodiment. 
     Operation and Advantageous Effects of the Present Exemplary Embodiment 
     As illustrated in  FIG. 10 , in the column structure  80  and the base member  16  according to the present exemplary embodiment, the base plate  16 A is provided with the cutaway portion  16 F and the cutaway portion  16 G. Locations equivalent to the cutaway portion  16 F and the cutaway portion  16 G can accordingly be omitted from the base plate  16 A, enabling a reduction in weight of the base plate  16 A. 
     In addition to the above operation and advantageous effects, the column structure  80  and the base member  16  according to the present exemplary embodiment can obtain similar operation and advantageous effects to those obtained by the column structure  70  and the base member  16  according to the fifth exemplary embodiment. 
     Note that the present exemplary embodiment may be applied to any out of the column structure  10  and the base member  16  according to the first exemplary embodiment to the column structure  60  and the base member  16  according to the fourth exemplary embodiment. The plan view shapes of the cutaway portion  16 F and the cutaway portion  16 G are not limited to U shapes, and may for example be configured with trapezoidal shapes or circular arc shapes. Moreover, slits may be formed in place of the cutaway portions. 
     Seventh Exemplary Embodiment 
     Explanation follows regarding a column structure and base member according to a seventh exemplary embodiment of the present invention, with reference to  FIG. 11 . The present exemplary embodiment is a modified example of the column structure  70  and the base member  16  according to the fifth exemplary embodiment. 
     Column Structure and Base Member Configuration 
     As illustrated in  FIG. 11 , in a column structure  90  according to the present exemplary embodiment, the base member  16  is configured from a first base member and a second base member. The first base member is provided with a first base plate  16 C serving as a base body, and the second base member is provided with a second base plate  16 D serving as a base body. 
     More specifically, the first base plate  16 C is configured in a rectangular flat plate shape with its length direction along the arrow FH direction and its short direction along the arrow WH direction. One of the flanges  30 B of the steel column  30  is joined to an upper end side of the first base plate  16 C. Moreover, two first fixing holes, the first fixing hole  18 A and the first fixing hole  18 B that serve as first fixing portions are disposed on the first base plate  16 C on the opposite side of the flange  30 B to the web  30 A side. First anchor bolts  24  serving as first anchor members are provided to the first fixing hole  18 A and the first fixing hole  18 B. 
     The second base plate  16 D is configured in a rectangular flat plate shape with its length direction along the arrow FH direction and its short direction along the arrow WH direction. The second base plate  16 D is provided at a separation to the first base plate  16 C. The other of the flanges  30 B of the steel column  30  is joined to an upper end side of the second base plate  16 D. Two second fixing holes, the second fixing hole  20 G and the second fixing hole  20 H, are disposed on the second base plate  16 D on the web  30 A side of the flange  30 B. Second anchor bolts  26  serving as second anchor members are provided to the second fixing hole  20 G and the second fixing hole  20 H. 
     Operation and Advantageous Effects of the Seventh Exemplary Embodiment 
     As illustrated in  FIG. 11 , the column structure  90  and the base member  16  according to the present exemplary embodiment, are provided with the first base plate  16 C serving as the first base member that is joined to the one flange  30 B of the steel column  30 , and the second base plate  16 D serving as the second base member that is joined to the other flange  30 B of the steel column  30 . The first base plate  16 C and the second base plate  16 D are configured at a separation to one another. The surface area of the base member  16  can thereby be reduced by the amount of the separation between the first base plate  16 C and the second base plate  16 D. In  FIG. 11 , the region enclosed by the by the broken line labelled  16 E is omitted. A reduction in weight of the base member  16  equivalent to the region  16 E can accordingly be achieved. Moreover, a reduction in the material required for manufacture of the base member  16  can be achieved. A reduction in the manufacturing costs of the column structure  90  and the base member  16  can also be achieved. 
     Moreover, in the column structure  90  and the base member  16  according to the present exemplary embodiment, a region  16 B of the second base plate  16 D on the opposite side of the flange  30 B to the web  30 A side is omitted, thereby enabling the steel column  30  to be brought closer to an adjacent boundary. Efficient utilization of the building site is thereby enabled. 
     Note that the present exemplary embodiment may be applied to any out of the column structure  10  and the base member  16  according to the first exemplary embodiment to the column structure  60  and the base member  16  according to the fourth exemplary embodiment. More specifically, for example in the column structure  10  and the base member  16  according to the first exemplary embodiment, the base plate  16 A may be split into the first base plate  16 C and a second base plate  16 D. 
     Other Exemplary Embodiments 
     The present invention is not limited to the exemplary embodiments described above, and various modifications are possible within a range not departing from the spirit of the present invention. For example, in the first exemplary embodiment illustrated in  FIG. 2 , four fixing portions or anchor members are respectively provided to the base member along the flange width direction at both width direction end portions of the web. In the present invention, three or more fixing portions or anchor portions may be respectively provided to the one end portion and the other end portion in the base member length direction. When there are a minimum of three fixing portions or anchor members, one fixing portion or anchor member is provided at a flange width direction central portion, and one fixing portion or anchor member is provided at each flange width direction end portion. Moreover, when there are a minimum of three fixing portions or anchor members, configuration may be made such that two fixing portions or anchor members are provided at flange width direction central portions, and one fixing portion or anchor member is provided to one out of two flange width direction end portions. Moreover, in the present invention, one anchor member with high tensile strength may be provided at the building outside, or three or more anchor members may be provided.