JP2015218478A - Staircase - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a staircase that can obtain spaciousness in a depth direction in a front view without deteriorating designability of an appearance.SOLUTION: A staircase includes a treadboard member and a load bearing member for supporting the treadboard member. The load bearing member comprises a treadboard support part that is formed of a steel plate and to which the treadboard member is fixed, and a pair of bridgeboard parts for supporting a width-direction central part of the treadboard support part, which is formed of the steel plate, from vertically below.

Description

  The present invention relates to a staircase, and in particular, to a staircase having a spar section.

  2. Description of the Related Art Conventionally, there is known a staircase in which a force girder type that does not cover the side surface in the width direction of a step plate is provided, a kick plate is not provided, and a handrail is made of a crosspiece or a transparent panel member. As such a staircase, as disclosed in Patent Document 1, a step plate made of a steel girder formed of a steel hollow square member or the like, and a step plate support plate made of steel and a step plate cover formed of plywood or the like. , Are disclosed.

JP 2006-009358 A

  By the way, as a device for obtaining a feeling of openness in a narrow building constructed in an urban area, there is a case where a line of sight is removed without surrounding a staircase with a partition wall or the like. The staircase disclosed in Patent Document 1 can be configured to have a feeling of opening when the staircase is viewed from the side by applying such a device. However, when this staircase is viewed from the front, the hollow square material is easily noticeable, and the effect on the aesthetics due to mismatch with the step board and other interior materials and the effect on the sense of openness in the depth direction become large. There is.

  In particular, in the case of a building with standardized parts, such as an industrialized house, if there are many variations in finish (such as color) to reduce the impact on aesthetics, there is a risk of high costs and management There is a risk that labor will increase.

  In view of the above problems, an object of the present invention is to provide a staircase that can provide a sense of openness in the depth direction when viewed from the front without impairing the design of the appearance.

  The staircase as one aspect of the present invention includes a step plate member and a load support member that supports the step plate member, and the load support member is formed of a steel plate and the step plate support to which the step plate member is fixed. And a pair of spar girders that are formed of a steel plate and support the central portion in the width direction of the corrugated plate support portion from below in the vertical direction.

  As one embodiment of the present invention, it is preferable that the corrugated plate support portion is joined to each of the pair of spar girder portions by welding.

  As one embodiment of the present invention, a plurality of the step plate members and the step plate support portions to which the step plate members are fixed are provided, and the step plate members are provided on the upper surface of the step plate support portions. A rectangular plate-like stepped plate portion to be placed; and a rectangular plate-like standing portion that stands up vertically from a rear end portion in the depth direction of the stepped plate portion, and among the plurality of stepped plate members The upper end of the upright portion of one first corrugated plate member, the lower end of the second corrugated plate member located one step higher than the first corrugated plate member, and the corrugated plate support to which the second corrugated plate member is fixed It is preferable that a gap is formed between the lower end of the part.

  As one embodiment of the present invention, it is preferable that the gap is not more than half of the kick-up dimension.

  As one embodiment of the present invention, it is preferable that the back surface of the upright portion is in contact with the vertical portion on the long side on the upper side in the vertical direction of the spar.

  As one embodiment of the present invention, at the lower end in the vertical direction of the spar girder, the spar girder is fixed to a concrete foundation beam that supports the building frame or the building frame and transmits the load to the ground. It is preferable that a portion is provided, and the fixing portion is located below a floor finish surface located above the casing in the vertical direction.

  According to the present invention, it is possible to provide a staircase that provides a sense of openness in the depth direction when viewed from the front without impairing the design of the appearance.

It is a perspective view which shows the staircase as one Embodiment of this invention. It is the elevation which looked at the stairs shown in FIG. 1 from the front. It is the elevation which looked at the stairs shown in FIG. 1 from the side. It is a perspective view which shows the load support member in the stairs shown in FIG. 5a and 5b are detailed views showing the attachment details of the lower end portion in the vertical direction of the staircase shown in FIG. 6a and 6b are detailed views showing the attachment details of the upper end portion in the vertical direction of the staircase shown in FIG.

  Hereinafter, the staircase 1 as one embodiment of the staircase according to the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the common member in each figure.

  FIG. 1 is a perspective view of a staircase 1 installed in a building (house) having a steel frame. FIG. 2 is an elevation view of the stairs 1 as seen from the front. FIG. 3 is an elevation view of the stairs 1 as seen from the side. FIG. 4 is a perspective view of the load support member 3 of the stairs 1. 5a and 5b are detailed views showing the attachment details of the lower end portion of the staircase 1 in the vertical direction A and the housing. 6a and 6b are detailed views showing the attachment details of the upper end of the staircase 1 in the vertical direction A and the housing. 5a and 6a are detailed views when the staircase 1 is viewed from the front side, and FIGS. 5b and 6b are detailed views when the staircase 1 is viewed from the side surface side.

  As shown in FIGS. 1 to 6, the staircase 1 includes a plurality of step plate members 2 and a load support member 3 that supports the plurality of step plate members 2, and connects between the levels of the building. The staircase 1 of the present embodiment is a staircase that connects the first floor and the second floor of the building, and the lower end side in the vertical direction A of the staircase 1 supports the building frame and transmits the load to the ground. In addition, the position of the staircase 1 is fixed by fixing the upper end side in the vertical direction A of the staircase 1 to a steel beam 5 as a building frame. Further, the staircase 1 includes a handrail wall 20 having a handrail portion 21 at one end in the width direction C. The step plate member 2 and the load support member 3 of the staircase 1 have a handrail wall 20 and an inner wall in the width direction C. 30. 2 and 3 show the concrete foundation beam 4 to which the stairs 1 are fixed in addition to the stairs 1. In FIG. 1, for convenience of explanation, the handrail wall 20 and the inner wall 30 of the staircase 1 are indicated by a two-dot chain line, and also in FIGS. 2, 3, and 5, the handrail wall 20 is indicated by a two-dot chain line.

  As shown in FIGS. 1 to 3, the step plate member 2 includes a rectangular plate-like step plate portion 6 having a tread surface, and a depth direction of the step plate portion 6 (the same direction as the depth direction B of the stairs 1). And a rectangular plate-like standing portion 7 that is continuously raised from the rear end portion upward in the vertical direction A. In other words, the corrugated plate member 2 has a substantially L-shaped cross section (cross section orthogonal to the width direction C). The step plate portion 6 is placed on the upper surface 11 (see FIG. 4 and the like) of the step plate support portion 8 described later in the load support member 3. The upright portion 7 is disposed so as to abut on a vertical portion 15 (see FIG. 4 and the like) in the long side 12 of the load supporting member 3 on the upper side 12 in the vertical direction A of the later-described saddle girder portion 9. Functions as a board. The corrugated board member 2 is formed of a woody material such as a laminated material.

  As shown in FIGS. 2 to 5, the load support member 3 is formed of a steel plate, and is formed of a steel plate and a step plate support portion 8 on which the step plate member 2 is mounted and the step plate member 2 is fixed. And a pair of spar girders 9 for supporting the central portion 10 in the width direction C of the corrugated plate support portion 8 from below the vertical direction A.

  A plurality (13 in the present embodiment) of the corrugated plate support portions 8 are provided corresponding to the number of the corrugated plate members 2 installed, and each corrugated plate member 2 is mounted on the upper surface 11 of each corrugated plate support portion 8. And is fixed to each step plate support portion 8 by fastening means such as screws or bolts screwed from below the vertical direction A of each step plate support portion 8. As shown in FIG. 4, the corrugated plate support portion 8 is formed of a rectangular plate-shaped steel plate in which a portion on which the corrugated plate member 2 is placed is not bent. The corrugated plate support 8 is bridged between the pair of spar girders 9 and fixed to each of the pair of spar girders 9. In addition, as a steel plate in which the bending process is not performed in the part in which the corrugated board member 2 is mounted, it is not restricted to a simple flat steel plate in which the bending process is not performed at all as shown in FIG. For example, it is a position other than the part on which the step plate member 2 is placed, such as a part of the step plate support portion 8 to which a flange portion 26 (see FIGS. 2 and 5) described later is attached. The steel plate in which the bending process for forming the junction part of another member in the position where the lower surface of the step board part 6 of the step board member 2 does not contact may be given. However, it is preferable that the position of the flange portion 26 is a position that is not visually recognized by the standing portion 7 of the corrugated plate member 2 from the front direction or is hardly visible.

  As shown in FIG. 3, the pair of cage girders 9 extends obliquely from the first floor to the second floor, and a plurality of long girder portions 9 on the upper long side 12 in the vertical direction A of the pair of cage girders 9. By placing the step plate support portion 8, the step plate support portion 8 and the step plate member 2 placed on the step plate support portion 8 are supported. In the stairs 1, the bottom end in the vertical direction A of the pair of spar girders 9 is fixed to the concrete foundation beam 4 with screws, and the top end in the vertical direction A of the pair of spar girders 9 is bolted to the steel beam 5. The position is fixed by being fixed by the nut. Details of this will be described later (see FIGS. 5 and 6). The “longer side 12 on the upper side of the vertical direction A of the spar girder 9” means a stepped end surface formed on the upper side of the vertical direction A of the spar girder 9.

  Each of the pair of spar girders 9 is formed of a long flat steel plate that is not bent as shown in FIGS. 2 and 3. As shown in FIG. 2, the pair of spar girder portions 9 are arranged in parallel so that the thickness direction of the steel plate is the width direction C and the side surfaces 13 that are vertical planes face each other in the width direction C. Further, as shown in FIG. 3, the long side 12 on the upper side in the vertical direction A of the pair of spar girder portions 9 includes a horizontal portion 14 extending in the horizontal direction when the stairs 1 is viewed from the side, and a vertical direction. And a vertical portion 15 extending in the direction. The corrugated plate support 8 is installed between the pair of spar girders 9 with the thickness direction of the steel plate as the vertical direction A, and the upper surface 11 thereof is horizontal on the horizontal part 14 of each slat girder 9. Are joined. Note that the step plate portion 6 of the step plate member 2 described above is placed on the upper surface 11 of the step plate support portion 8, and the upright portion 7 of the step plate member 2 is the back surface in the depth direction B (surface on the rear end side). ) Is arranged so as to contact the vertical portion 15 of the long side 12.

  Further, the pair of countersink portions 9 support the central portion 10 in the width direction C of the corrugated plate support portion 8 from below the vertical direction A. Specifically, as shown in FIG. 2, when the staircase 1 is viewed from the front, the pair of spar girder portions 9 are located in the central portion 10 that is near the center in the width direction C of the stepboard support portion 8. As shown in FIG. 3, the corrugated plate support portion 8 is supported on the pair of spar 9 by being installed on the horizontal portion 14 of the pair of spar 9.

  Here, as shown in FIG. 2, the counter girder portion 9 is a flat steel plate having a dimension (thickness) of 12 mm in the width direction C, and this width is the width of the step plate member 2 and the step plate support portion 8. Very small (thin) compared to dimension in direction C. Therefore, when the spar girder 9 is viewed from the front of the staircase 1, only the vertical part 15 of the long side 12 is visually recognized in the kicked portion of the stairs 1, and it is difficult to hinder the visibility of the space behind. Do not disturb the feeling of opening in the depth direction B of the stairs 1. Further, even when the staircase 1 is viewed from an oblique direction (when the staircase 1 is viewed from a position between the front surface and the side surface), the sacrificial girder portion 9 is in the width direction C of the stepped plate support portion 8. It is not located at the end 16 (which is also in the vicinity of the end of the step plate member 2 in this embodiment), but at the central portion 10 of the step plate support portion 8 (which is also the central portion of the step plate member 2 in this embodiment). Since it is located, it is difficult to visually recognize the pair of countersink portions 9. Thus, the finishing girder portion 9 is finished with a different texture from the finishing material such as the stepped plate member 2 and other interior materials in the vicinity of the stairs 1 (for example, the finishing girder portion 9 of the steel plate Even if the finish is woody, the aesthetic appearance of the staircase 1 can be reduced.

  The corrugated plate support portion 8 is joined to each of the pair of spar girders 9 by welding (in this embodiment, fillet weld), and is fixed to the pair of spar girders 9. The joining of the step plate support portion 8 and the pair of spar girders 9 is not limited to welding, and for example, joining by fastening means such as bolts and nuts is also possible. However, as in the present embodiment, the step plate support portion 8 and the pair of spar girders 9 are joined by welding, so that the step plate support portion 8 and the pair of spar girders are compared with the joints using bolts and nuts. By increasing the integrity with the portion 9, the rigidity of the load supporting member 3 as a structure is increased, and the structural stability can be improved. Also, in the case of joining with bolts and nuts, there is a risk that the members will be displaced at the joint and unpleasant squeak noise may occur, but in the case of joining by welding, squeak noise will occur because there is no displacement at the joint. There is nothing. Furthermore, if no joining piece or joining member is required, the number of parts constituting the staircase 1 can be reduced, and the structural stability is improved by welding as described above. The structure of the load supporting member 3 that is simpler and more sophisticated in design can be realized, for example, the thickness of the steel plate can be reduced as compared with the case of bolt and nut joining. In addition, by reducing the thickness of the step board support portion 8, it is possible to further emphasize the feeling of opening in the depth direction B of the stairs 1.

  In the present embodiment, the width in the width direction C of the step plate member 2 is about 800 mm, whereas the width (thickness) in the width direction C of each of the spar girders 9 is 12 mm. The thickness in the vertical direction A is 6 mm. Further, in the width direction C, the position of each sheathing girder portion 9 to support the step plate support portion 8 from below the vertical direction A, that is, the position of each sheathing girder portion 9 in the width direction C when the stairs 1 is viewed from the front. Is a position separated from the center in the width direction C of the corrugated plate support 8 by 100 mm. In other words, in the present embodiment, the distance between the center lines in the width direction C of the pair of spar girders 9 is 200 mm.

  Further, as shown in FIG. 4, the corrugated plate support portion 8 is formed of a rectangular plate-shaped steel plate that is not subjected to bending processing on the portion on which the corrugated plate member 2 is placed. The entire upper surface 11 of 8 is in surface contact with the lower surface of the step plate member 2 to support the step plate member. In the case of the configuration in which the step plate cover as the step plate member has the engagement groove as in Patent Document 1 described above, since the cross-sectional defect occurs due to the engagement groove and the strength decreases, the step plate cover in the vertical direction A In some cases, it is necessary to increase the overall thickness or use a high-strength material. On the other hand, since the cross-sectional defect does not occur in the step plate member 2 of the present embodiment, the entire thickness can be reduced or a low-strength material can be used. Therefore, it becomes easy to increase variations in the thickness and material in the vertical direction A of the step plate member 2 as the finishing material.

  Here, the saddle girder part 9 of the present embodiment includes a horizontal part 14 extending in the horizontal direction on the long side 12 on the upper side in the vertical direction A and the vertical direction extending when the saddle girder part 9 is viewed from the side. However, the shape is not limited to such a shape.For example, when viewed from the side, the horizontal portion extends in the horizontal direction. You may comprise the inclination part inclined with respect to the perpendicular direction, and the long side of the vertical direction upper side of the baffle part.

  By joining the step plate support portion 8 to the horizontal portion 14 of the spar girder 9 by welding, the rigidity of the spar girder portion 9 that is formed of a thin steel plate and easily deforms in the width direction C can be compensated. Waves can be suppressed.

  In the present embodiment, the upper end of the upright portion 7 of the first step plate member 2a, which is an arbitrary one of the plurality of step plate members 2, is positioned one step higher than the first step plate member 2a. The lower surface as the lower end of the second step plate member 2b and the lower surface as the lower end of the step plate support portion 8 to which the second step plate member 2b is fixed are separated from each other, and a gap is formed between them. (See FIG. 2 etc.). Moreover, the standing part 7 in the step board member 2 of this embodiment is comprised so that the length in the perpendicular direction A may become half or less of the kick-up dimension.

  By providing the standing portion 7, the foot slips on the stairs 1 and the foot slips through the gap between the step board members 2, and the infant slips through the gap between the step board members 2 and falls. Can be suppressed. As shown in FIG. 2, the pair of spar girders 9 according to the present embodiment is located in the center portion 10 in the width direction C of the step plate support portion 8 and in the vicinity of the back surface of the step plate member 2 in the depth direction B. Since the vertical part 15 of the long side 12 is located at the top, the resident may step on the toe against the vertical part 15 having a small width (thickness) of the spar girder part 9 when stepping up the stairs 1. However, by providing the standing portion 7, the resident's toe hits a wide surface of the standing portion 7, so that pain can be reduced as compared with the case where it hits the vertical portion 15. Further, since the back surface of the upright portion 7 is in contact with the vertical portion 15, the vertical portion 15 functions as a reinforcing member against horizontal shearing force and bending moment acting on the cantilevered upright portion 7. Therefore, it is not necessary to make the connection between the step plate portion 6 and the upright portion 7 in the step plate member 2, the manufacturing cost can be reduced, and the choice of the material and thickness of the step plate member 2 is expanded. You can also. Moreover, since the clearance gap is provided above the vertical direction A of the standing part 7, the feeling of opening in the depth direction B of the stairs 1 can also be maintained. Note that the gap in the present embodiment is set to be 110 mm or less in the vertical direction A.

  Next, the detail of joining with the staircase 1 and the concrete foundation beam 4 is demonstrated. As shown in FIGS. 5 a and 5 b, a first fixing portion 17 as a fixing portion for fixing the weir girder portion 9 to the concrete foundation beam 4 is provided at the lower end portion in the vertical direction A of the weir girder portion 9. The first fixing part 17 is a flat pedestal having a horizontal surface, which is formed integrally with the pair of spar girder parts 9, and the first fixing part 17 is a concrete foundation by fastening means such as screws, screws and bolts. It is joined to the beam 4.

  The first fixing portion 17 is located below the floor finish surface 18 located above the concrete foundation beam 4 in the vertical direction A and is not exposed from the floor finish surface 18. By setting it as such a structure, since the 1st fixing | fixed part 17 is not exposed, the staircase 1 can be comprised in a simple external appearance.

  Next, the detail of joining with the stairs 1 and the steel beam 5 as a building frame is demonstrated. As shown in FIGS. 6a and 6b, a second fixing portion 19 as a fixing portion for fixing the weir girder portion 9 to the steel beam 5 made of H-shaped steel is provided at the upper end portion of the rafter girder portion 9 in the vertical direction A. It has been. The second fixing portion 19 is a flat pedestal having a vertical plane and formed integrally with the pair of spar girders 9, and the second fixing portion 19 is joined to the steel beam 5 by fastening means such as bolts. Is done.

  Here, as shown in FIG. 1, the step plate member 2 and the load support member 3 (see FIGS. 2 to 4) of the staircase 1 are sandwiched between the handrail wall 20 and the inner wall 30 on both sides in the width direction C. . The handrail wall 20 of the present embodiment includes a handrail portion 21 and a wall portion 22 provided with the handrail portion 21, and the wall portion 22 is fixed to the corrugated plate member 2 and extends in the vertical direction A. A strut-shaped reinforcing metal as the reinforcing member 23 is included. As shown in FIGS. 3 and 5, the reinforcing member 23 extends between two adjacent step plate support portions 8, and fastening means such as screws and bolts with respect to the two step plate support portions 8. And a base end portion 24 fixed by the above, and an extension that is fixed to the base end portion 24 by, for example, a fastening means such as a screw or a bolt or welding, and extends above the base end portion 24 in the vertical direction A. Unit 25. Moreover, as shown in FIGS. 2 and 5, the rear end in the depth direction B in the lower step plate support portion 8 of the two step plate support portions 8 to which the base end portion 24 is fastened, And the flange part 26 extended in the perpendicular direction A from the upper surface 11 which is a horizontal surface is attached to the edge part of the width direction C. As shown in FIG. As shown in FIG. 5, the lower end side in the vertical direction A of the base end portion 24 of the reinforcing member 23 is in contact with the back surface of the flange portion 26 and is fixed by fastening means. Further, as shown in FIG. 5, the upper end side in the vertical direction A of the base end portion 24 of the corrugated plate support portion 8 positioned one step higher than the corrugated plate support portion 8 to which the flange portion 26 is attached. It contacts the lower surface and is fixed by fastening means. The load support member 3 shown in FIG. 4 is drawn with the flange portion 26 omitted.

  The wall portion 22 includes a base frame attached around the reinforcing member 23 and a gypsum board attached outside the base frame. The lower end portion of the wall portion 22 in the vertical direction A is fixed to the floor foundation layer made of a floor slab or mortar that is located below the floor finish surface and above the upper end of the concrete foundation beam 4 in the vertical direction A. Has been.

  The staircase 1 according to the present embodiment has a structure including a load support member 3 in which a pair of spar girder portions 9 and a step plate support portion 8 are joined together by welding, and the staircase 1 is provided without the handrail wall 20. It has sufficient strength. Therefore, for example, the handrail wall 20 of the present embodiment can be removed. By setting it as such a structure, it can be set as the staircase which gave the feeling of opening not only in the depth direction B but in the width direction C. In addition, the means for realizing a feeling of opening in the width direction C is not limited to a configuration in which a handrail wall is not provided. For example, a glass plate is provided instead of a gypsum board on the handrail wall, and the depth direction It can also be set as the structure which gave the open feeling in B and the width direction C. FIG. In the width direction C, a gap is formed between the staircase 1 and the inner wall 30 and is structurally separated from each other. Further, the dimension of the step plate member 2 in the depth direction B is configured to be larger than the dimension of the step plate support part 8 in the depth direction B, and the dimension of the step plate member 2 in the width direction C is set to be the step plate support part 8. It is comprised larger than the dimension of the width direction C.

  As an example of the construction method of the building including the stairs 1 of the present embodiment, the load supporting member 3 including the pair of spar girder portions 9 and the plurality of step plate supporting portions 8 is assembled in advance at a manufacturing factory or the like, At the time of construction, this load support member 3 is brought into the construction site and set in the building, and then the wooden work and finishing work inside the building are performed, and then the step plate member 2 is placed on the step plate support portion 8. A method of mounting and fixing can be considered. According to such a construction method, since the step plate member 2 is placed on the step plate support portion 8 after finishing the inner wall 30, for example, the inner wall 30 due to the presence of the step plate member 2. In addition, it is possible to eliminate the deterioration of the workability and to save the trouble of curing the corrugated plate member 2.

  Further, even if the step plate member 2 is not attached, the lifting and lowering can be performed only by the load supporting member 3, so that the construction can proceed smoothly without separately providing a temporary lifting means. Further, when the step plate support portion 8 and the step plate member 2 are fastened by fastening means such as screws or bolts, the operator uses the gap above the lower stand portion 7 without using a stepladder or the like. Thus, the fastening operation between the upper plate support portion 8 and the plate member 2 can be performed.

  The steps according to the present invention are not limited to the present embodiment, and various modifications can be made within the scope according to the claims. For example, although the staircase 1 of this embodiment shows what was provided between the 1st floor and the 2nd floor, it is not restricted to this, It can also be set as the structure provided between another hierarchy. In that case, if the position of the load support member 3 is fixed by fixing the load support member 3 to the housing located on the lower side of the load support member 3 and the housing located on the upper side in the vertical direction A, respectively. Good. Further, the step plate member 2 and the step plate support portion 8 of the present embodiment have a substantially rectangular outline when viewed from above in the vertical direction A, but are not limited to this shape. The shape and the like can be changed as appropriate according to the environment, usage, design, etc. for installing the stairs. Further, in the present embodiment, the center position of the step plate member 2 in the width direction C and the center position of the step plate support portion 8 in the width direction C are substantially the same, but the configuration is limited to such a configuration. Instead, for example, the center position of the step plate member in the width direction C is shifted from the center position of the step plate support portion 8 in the width direction C. Can do.

  The present invention relates to a staircase, and more particularly to a staircase having a spar girder.

1: Step 2: Step plate member 2a: First step plate member 2b: Second step plate member 3: Load support member 4: Concrete foundation beam 5: Steel beam 6: Step plate portion 7: Standing portion 8: Step plate support Part 9: Sagittal girder part 10: Center part in the width direction of the corrugated board support part 11: Upper surface of the corrugated board support part 12: Long side on the upper side in the vertical direction of the corrugated board part (stepped end face)
13: Side surface of the spar girder part 14: Horizontal part 15: Vertical part 16: End part in the width direction of the step board support part 17: First fixing part (fixing part)
18: Floor finish surface 19: Second fixing part (fixing part)
20: Handrail wall 21: Handrail portion 22: Wall portion 23: Reinforcement member 24: Base end portion 25: Extension portion 26: Flange portion 30: Inner wall A: Vertical direction B: Depth direction C: Width direction

Claims (6)

A corrugated plate member;
A load supporting member for supporting the stepped plate member,
The load support member includes a step plate support portion formed of a steel plate to which the step plate member is fixed, and a pair of spar girders formed of a steel plate and supporting a central portion in the width direction of the step plate support portion from below in the vertical direction. And a staircase characterized by comprising a part.   The staircase according to claim 1, wherein the step plate support portion is joined to each of the pair of spar girder portions by welding. A plurality of the step plate members and the step plate support portions to which the step plate members are fixed are provided,
The step plate member includes a rectangular plate-like step plate portion placed on the upper surface of the step plate support portion, and a rectangular plate-like standing upright from the rear end portion in the depth direction of the step plate portion. And comprising
The upper end of the upright portion of one first step plate member among the plurality of step plate members, the lower end of a second step plate member positioned one step higher than the first step plate member, and the second step plate The staircase according to claim 1, wherein a gap is formed between the lower end of the step plate support portion to which the member is fixed.   The staircase according to claim 3, wherein the gap is less than half of the kick-up dimension.   5. The staircase according to claim 3, wherein a back surface of the upright portion is in contact with a vertical portion on a long side on an upper side in a vertical direction of the sagittal girder portion. At the lower end of the vertical direction of the spar girder, a fixing part is provided for fixing the spar girder to a concrete foundation beam that supports the building frame or the building frame and transmits the load to the ground.
The staircase according to any one of claims 1 to 5, wherein the fixing portion is located below a floor finish surface located above the casing in the vertical direction.

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