All publications and patent applications mentioned in this specification are herein incorporated by reference in their entirety to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
The present invention relates to a steel-framed concrete beam and a method for constructing a steel-framed concrete beam.
Proposed in the related art is a method for forming a web opening for passing a duct or the like through an RC beam. According to a proposed example of the method, a decline in the proof stress of the beam during web opening formation is suppressed by penetration reinforcement being performed with a reinforcing member attached to the outer shell of the beam, and then the web opening penetrating the beam and the reinforcing member is formed (see, for example, Patent Document 1).
According to the method described in the Patent Document 1, the reinforcing member needs to be separately attached to a side surface of the beam after RC beam building for the web opening to be formed, and then an increase in work man-hours arises. Besides, the web opening can be formed only in the range of reinforcing member attachment, and thus the degree of freedom is low in terms of the position and size of the web opening. Desired in this regard are a steel-framed concrete beam and a method for constructing a steel-framed concrete beam allowing a reduction in the labor and cost entailed by separate reinforcing member attachment for web opening formation and allowing enhancement of the degree of freedom in terms of web opening position and size.
It is an object of the present invention to solve the problems of the above mentioned prior arts.
One aspect of the present invention provides a steel-framed concrete beam comprises: a steel form having a bottom plate portion and a pair of side plate portions extending upward from both ends of the bottom plate portion; and concrete placed in a groove portion configured by the bottom plate portion and the pair of side plate portions of the steel form.
Embodiments of a steel-framed concrete beam according to the invention will be described in detail below with reference to accompanying drawings. The basic concepts of the embodiments ([I]) will be described first, and then details of the embodiments ([II]) will be described. Modification examples regarding the embodiments ([III]) will be described last. The invention is not limited by the embodiments.
The basic concepts of the embodiments will be described first.
The embodiments relate to a steel-framed concrete beam constituting a building. The “steel-framed concrete beam” is a beam provided with at least a steel frame and concrete. The steel-framed concrete beam may be provided with a component other than the steel frame and the concrete. For example, the embodiments illustrate an example in which the steel-framed concrete beam is configured as a steel-framed reinforced concrete beam that has a rebar in addition to a steel frame and concrete. Although the steel-framed reinforced concrete beam may be provided with, for example, a main bar and a stirrup as the rebar, a case where the steel-framed reinforced concrete beam is provided with a main bar and no stirrup will be described below. The steel-framed concrete beam may be provided with, for example, a stirrup and no main bar, both a main bar and a stirrup, or no main bar and no stirrup.
The steel frame is capable of having any shape insofar as the steel frame functions as a form allowing concrete placement. A case where the steel frame has an axial cross section in a hat shape (a shape obtained by joining a pair of Z-steels to each other) will be described below.
The steel-framed concrete beam according to the embodiments is applicable to any installation floor. Although a case where the steel-framed concrete beam is a second floor beam will be described below, the steel-framed concrete beam is applicable to beams of other floors as well. Although a case where the steel-framed concrete beam is a binding beam will be described below, the steel-framed concrete beam may be a girder as well.
Details of the embodiments will be described below.
The steel-framed concrete beam according to Embodiment 1 will be described first.
(Configuration)
(Configuration-Steel Form)
The steel form 10 is a steel form that has a groove portion (described later) for placing the binding beam concrete 20. This steel form 10 is provided in each binding beam 1 constituting a building and is disposed so as to cover the binding beam 1 from below. As illustrated in the drawing, the steel form 10 of Embodiment 1 is formed by a pair of (that is, two) Z-steels 11 being mutually joined in bottom plate portions 12 (described later) at a construction site. The invention is not limited thereto, and the steel form 10 may be integrally formed with a single member or may be formed by three or more members being combined. In a case where three or more members are combined as described above, for example, the integrally formed members (the bottom plate portion 12, a side plate portion 13, a flange portion 14, and a reinforcing portion 15 to be described later) that constitute the Z-steel 11 may be formed separately. Each of the pair of Z-steels 11 can be substantially similar in configuration to the other, and thus only one of the Z-steels 11 will be described below. In a case where the Z-steels 11 need to be distinguished from each other, the Z-steel 11 that is positioned on the right of the binding beam 1 (in the +X direction) will be referred to as “right Z-steel” and the Z-steel 11 that is positioned on the left of the binding beam 1 (in the −X direction) will be referred to as “left Z-steel”. A specific method for forming the steel form 10 will be described later.
The Z-steel 11 is a frame member that constitutes the steel form 10. As illustrated in
The bottom plate portion 12 is a steel plate positioned on the bottom surface of the steel form 10. The bottom plate portion 12 has a joining surface 16 for mutually joining the respective bottom plate portions 12 of the pair of Z-steels 11. The pair of Z-steels 11 are joined to each other on the joining surface 16. For example, in Embodiment 1, a part of the bottom plate portion 12 of the right Z-steel is superposed on a part of the bottom plate portion 12 of the left Z-steel and each of the parts where the pair of Z-steels 11 are in contact with each other (the upper surface of the bottom plate portion 12 of the left Z-steel and the lower surface of the bottom plate portion 12 of the right Z-steel) is the joining surface 16. The joining on the joining surface 16 can be performed by any specific method. For example, in Embodiment 1, a plurality of bolt holes (not illustrated) are spaced apart along the longitudinal direction (+Y-Y direction) of the beam in the joining surfaces 16 of both Z-steels 11 and both Z-steels 11 are joined by bolt fastening by means of the bolt holes. Specific joining methods are not limited thereto. For example, welding-based joining and screw penetration-based joining may be performed instead.
The side plate portion 13 is a steel plate extending in the upward direction from the bottom plate portion 12. Specifically, the side plate portion 13 is a part that is folded back from the outer end of the bottom plate portion 12 and extends to the upper end of the beam and is positioned so as to cover the left and right sides of the binding beam 1. The length of the side plate portion 13 in the height direction (+Z-Z direction) is longer, by the thickness of the bottom plate portion 12, in the left Z-steel than in the right Z-steel. This is for the upper end positions of the side plate portions 13 of both Z-steels 11 (that is, the height positions of the flange portions 14) to coincide with each other when the pair of Z-steels 11 are overlapped.
In the following description, the part that is formed by the side plate portions 13 and the bottom plate portions 12 of a pair of the steel forms 10 and has a U-shaped axial cross section will be referred to as groove portion as necessary. Concrete can be placed in the groove portion by the steel form 10 forming the groove portion as described above. The lower and side parts of the binding beam 1 are covered with a steel plate by the groove portion, and thus it is possible to deter steam from escaping from the lower and side parts of the binding beam concrete 20 during a fire, it is possible to deter a temperature rise in the room below the binding beam 1, and it is possible to improve the fire resistance performance of the binding beam 1.
The flange portion 14 is a steel plate extending in the outward direction from the upper end of the side plate portion 13. Specifically, the flange portion 14 is a part that is folded back in the outward direction from the upper end of the side plate portion 13 and extends along a horizontal plane, and a deck plate 3 is placed and screwed on the flange portion 14. Although a case where this deck plate 3 is a known corrugated steel plate will be described, the invention is not limited thereto and a flat plate may be used as the deck plate 3. Although illustration is omitted, the binding beams 1 are arranged side by side at intervals along the longitudinal direction of a girder 2, one end portion of the deck plate 3 is placed in the flange portion 14 of one binding beam 1 as illustrated in
The reinforcing portion 15 is a steel plate extending in the downward direction from the outer end of the flange portion 14. By the reinforcing portion 15 being provided as described above and thickness being given to the outer end of the flange portion 14, the local buckling of the outer end of the flange portion 14 that pertains to a case where the slab concrete 4 is placed and the flange portion 14 receives the load of the slab can be deterred. In addition, it is possible to reduce the overall thickness of the steel form 10 by locally reinforcing only a low-strength part by means of the reinforcing portion 15. The reinforcing portion 15 of Embodiment 1 extends in the downward direction from the outer end of the flange portion 14. The invention is not limited thereto and the reinforcing portion 15 may extend in, for example, the upward direction.
(Configuration-Binding Beam Concrete)
The binding beam concrete 20 is concrete placed in the groove portion that the pair of side plate portions 13 and the bottom plate portion 12 of the steel form 10 constitute. The binding beam concrete 20 is known concrete solidified after filling in the groove portion, and the plurality of web openings 40 are formed in the binding beam concrete 20 as described above. The slab concrete 4 for forming an upper floor slab is formed along a horizontal plane above the binding beam concrete 20. Girder concrete (reference numeral omitted) for forming the girder 2 is formed, so as to be orthogonal to the binding beam 1, at the front and rear ends of the binding beam concrete 20. Although the binding beam concrete 20, the slab concrete 4, and the girder concrete are given different names and reference numerals, the binding beam concrete 20, the slab concrete 4, and the girder concrete are simultaneously placed and formed in Embodiment 1. The binding beam concrete 20, the slab concrete 4, and the girder concrete will be simply referred to as “concrete” when no distinguishment among them is necessary.
(Configuration-Main Bar)
The main bars 30 are rebars extending along the axial center direction of the beam. Although two upper end bars and four lower end bars are illustrated as an example in Embodiment 1, the number and disposition of the main bars 30 are not limited thereto.
(Configuration-Web Opening)
The web opening 40 is a hole formed so as to penetrate the side plate portion 13 and the binding beam concrete 20. The web opening 40 is formed by, for example, the side plate portion 13 and the binding beam concrete 20 being drilled with a drill after the binding beam concrete 20 placed in the steel form 10 is solidified. By the web opening 40 being formed as described above, a duct or piping for air conditioning, electrical equipment, and so on can be passed through the web opening 40 (a case where a duct for air conditioning is passed through the web opening 40 will be described below). Accordingly, the duct can be extended from one of spaces sandwiching the beam 1 (such as the space to the right of the binding beam 1) to the other thereof (such as the space to the left of the binding beam 1) and the degree of freedom of duct disposition is improved.
The web opening 40 is formed in the web opening forming portion of the binding beam 1. The “web opening forming portion” is a part where the web opening 40 penetrating the side plate portion 13 and the binding beam concrete 20 can be formed. Specifically, the “web opening forming portion” is a part where no rebar (main bar 30 in Embodiment 1) is arranged (part where the drill does not interfere with the rebar when the web opening 40 is drilled with the drill). For example, in Embodiment 1, the “web opening forming portion” is a part above the lower main bar 30 (lower end bar) in the binding beam 1. The number of the web openings 40 is six and the web openings 40 are along the axial center direction of the beam in the illustration. The number of the web openings 40 is not limited to six.
(Configuration-Girder Joining Portion)
The joining portion between the binding beam 1 and the girder 2 according to Embodiment 1 will be described below.
Temporary supports (not illustrated) may support the binding beam 1 until concrete placement. The positions and number of the temporary supports may be appropriately changed in accordance with the length and weight of the binding beam 1. For example, one temporary support may be provided in one axial end portion, one temporary support may be provided in the other axial end portion, and one temporary support may be provided in the axial middle portion. The steel form 10 is higher in proof stress than the wooden form 2a, and thus the temporary supports may be omitted if the temporary supports are unnecessary in view of the length and weight of the binding beam 1.
(Method for Designing Steel Form)
Next, an example of a method for designing the steel form 10 according to Embodiment 1 will be described. In the present embodiment, the allowable bending moment or the allowable shear force of the binding beam 1 is calculated by the following Equation (1).
Fa=FRC+β·FS (Equation 1)
Fa: allowable bending moment or allowable shear force of binding beam 1
FRC: allowable bending moment or allowable shear force of binding beam concrete 20 (hereinafter, referred to as reinforced concrete (“RC”) as necessary)
β: burden factor of allowable bending moment or allowable shear force of steel form 10, which is 0.5 or less
FS: allowable bending moment or allowable shear force of steel form 10
(Method for Designing Steel Form-Method for Designing Allowable Bending Moment)
This design method will be divided into an allowable bending moment design method and an allowable shear force design method and described in further detail below. The allowable bending moment design method will be described first. The allowable bending moment is designed after division into a long-term allowable bending moment and a short-term allowable bending moment. The long-term allowable bending moment is calculated by the following Equation (2). The short-term allowable bending moment is calculated by the following Equation (3).
LMa=LMRC+LβM·LMS (Equation 2)
SMa=SMRC+SβM·SMS (Equation 3)
An ultimate bending strength Mu is calculated by the following Equation (4).
Mu=MuRC+MuS (Equation 4)
MuRC: ultimate bending strength of RC cross section part (MuRC=0.9·at·1.1·Sft·d)
The long-term allowable bending moment is an allowable bending moment over a relatively long time (such as several years to several decades). The short-term allowable bending moment is an allowable bending moment over a relatively short time (such as several hours to several days). The allowable bending moment is calculated after the division into the two periods as described above so that an allowable bending moment suitable for each load bearing ratio is designed in view of the fact that the load bearing ratio of the RC and the steel form 10 in the binding beam 1 can vary as the situation of loading on the binding beam 1 can vary with the lengths of the periods. In other words, it is assumed that the loading on the binding beam 1 is relatively small in a relatively long time, and thus it is assumed that the RC of the binding beam 1 is maintained without breaking (see the lower left cross section in
The steel frame bending burden effective factor βM can be calculated from a bending rigidity ratio ζM(=ESIS/ECIC) of the RC and a bending rigidity ESIS of the steel form 10. The bending rigidity ratio ζM can vary with the plate thickness of the steel form 10 and the thickness of the slab concrete 4 attached to the binding beam 1 (hereinafter, referred to as “slab” as necessary), and thus an application restriction range is set for each of the plate thickness of the steel form 10 and the thickness of the slab, the bending rigidity ratio ζM is calculated on the premise of the application restriction range, and the steel frame burden effective factor βM is determined from the calculated bending rigidity ratio ζM. Specifically, the plate thickness of the steel form 10 has an application restriction range of 3.2 mm or more. The load bearing ratio of the steel form 10 increases as the plate thickness of the steel form 10 increases, and thus a lower limit value of “3.2 mm” and application restriction range setting “at or above” the lower limit value allow the steel frame burden effective factor βM to remain above it insofar as the plate thickness of the steel form 10 is determined in the application restriction range. The thickness of the slab has an application restriction range of 200 mm or less. The ratio of load bearing by the slab increases as the thickness of the slab increases, and then the load bearing ratio of the steel form 10 decreases. Accordingly, an upper limit value of “200 mm” and application restriction range setting “at or below” the upper limit value allow the steel frame burden effective factor βM to remain above it insofar as the thickness of the slab is determined in the application restriction range.
(Method for Designing Steel Form-Method for Designing Allowable Shear Force)
Next, the allowable shear force design method will be described. The allowable shear force is designed after division into a long-term allowable shear force and a short-term allowable shear force similarly to the above idea related to the allowable bending moment. The long-term allowable shear force is calculated by the following Equation (5) and the short-term allowable shear force is calculated by the following Equation (6). The relationship between the cross section of the binding beam 1 and calculation parameters is as illustrated in
LQa=α·AC·LfS+βQ·SAW·LσS (Equation 5)
SQa=α·AC·SfS+βQ·SAW·Sσs (Equation 6)
The shear effective cross-sectional area AC of the RC portion used in the shear force calculation is the same cross section as the binding beam 1 used in the experiment as illustrated in
As described above, the long-term steel frame bending burden effective factor LβM is 0.1 and the short-term steel frame bending burden effective factor SβM is 0.4 in the design of the allowable bending moment. In the design of the allowable shear force, the steel frame shear burden effective factor βQ is 0.2. Although the burden factor β of the steel form 10 may be another value, the upper limit of the load bearing ratio of the steel form 10 is set to 50% and the burden factor β of the steel form 10 is set to 0.5 or less for safety enhancement. The lower limit of the load bearing ratio of the steel form 10 can be at least 10% in view of the graphs in
(Steel Form Forming Method)
Next, an example of the method for forming the steel form 10 according to Embodiment 1 will be described. First, the Z-steel 11 is manufactured at a factory. The Z-steel 11 can be manufactured by any specific method. For example, the Z-steel 11 can be formed by bending of one flat thin steel plate. Subsequently, the manufactured Z-steel 11 is transported to a construction site. At this time, a plurality of the Z-steels 11 can be transported in an overlapping manner, and thus it is possible to transport more Z-steels 11 at one time than in the case of transporting the pair of mutually joined Z-steels 11. Transport efficiency enhancement can be achieved as a result.
The sealing material (small piece) 2d described with reference to
Next, the pair of Z-steels 11 transported to the construction site are joined together and the steel form 10 is formed. Specifically, as illustrated in
(Binding Beam Construction Method)
A method for constructing the binding beam 1 according to Embodiment 1 will be described below.
First, the steel form installation step is performed as illustrated in
Subsequently, the main bar arrangement, deck plate installation, and placement steps are performed as illustrated in
The main bars 30 are arranged in the steel form 10 in the main bar arrangement step. Specifically, the main bars 30 are assembled, lifted by means of a heavy machine or the like, and dropped into and disposed in the groove portion. Likewise, the main bars 30 (not illustrated) of the girder 2 are dropped into and disposed in the wooden form 2a of the girder 2. Then, the main bars 30 of the binding beam 1 are bent in, for example, end portions and fixed to the main bars 30 of the girder 2.
The deck plates 3 are installed on the flange portions 14 of the steel form 10 in the deck plate installation step. In the deck plate installation step, the plurality of deck plates 3 are placed on the flange portions 14 so as to bridge one binding beam 1 and another adjacent binding beam 1 and fixed to the flange portions 14 by bolt fastening or the like.
In the placement step, the binding beam concrete 20 is placed in the groove portion that is configured by the pair of side plate portions 13 and the bottom plate portion 12 of the steel form 10 installed in the steel form installation step. Specifically, in this placement step, concrete is poured into the groove portion of the steel form 10 while a vibrator is used for air bubble mixing prevention. As described above, in Embodiment 1, concrete is simultaneously placed in the wooden form 2a of the girder 2 and on the deck plate 3, and then the binding beam 1, the girder 2, and the slab are integrally formed.
Subsequently, the penetration step is performed as illustrated in
The size and the position of disposition of the web opening 40 can be determined similarly to general RC. For example, it is preferable that the maximum diameter of the web opening 40 is one-third or less of the height of the binding beam 1 (dimension D in
Lastly, a duct is passed through the web opening 40 formed in the penetration step. The passage of the duct (not illustrated) is performed by a known method and will not be described in detail. This is the end of the description of the binding beam construction method according to Embodiment 1.
As described above, in the binding beam 1 of Embodiment 1, the binding beam concrete 20 has an outer shell covered by the steel form 10, and thus it is possible to suppress a decline in proof stress during the formation of the web opening 40 in the side surface of the binding beam 1 and it is possible to reduce the labor and cost entailed by separate reinforcing member attachment for forming the web opening 40.
In addition, it is possible to calculate a complex allowable bending moment and a complex allowable shear force taking the respective bearing ratios of the steel form 10 and the binding beam concrete 20 into account and it is possible to optimize the design of the binding beam 1.
Since the outer shell of the binding beam concrete 20 is covered by the steel form 10, the part where the web opening 40 can be formed is not limited to the part of reinforcing member attachment unlike in the related art. As a result, the degree of freedom of the size and disposition of the web opening 40 can be enhanced.
Since the flange portion 14 is provided, the load of the slab supported by the binding beam 1 can be received by the flange portion 14 and is allowed to smoothly flow to the binding beam 1 and the proof stress of the binding beam 1 is improved.
Since the reinforcing portion 15 is provided at the outer end of the flange portion 14, buckling of the flange portion 14 at a time when the binding beam concrete 20 is placed on the groove portion or the flange portion 14 of the steel form 10 can be suppressed by the reinforcing portion 15 and the proof stress of the binding beam 1 is improved.
Next, a binding beam according to Embodiment 2 will be described. Schematically, Embodiment 2 relates to a construction method in which a cylindrical form is pre-installed in the web opening forming portion and a web opening is formed in the place of cylindrical form installation by post-concrete placement cylindrical form removal. The configuration of the binding beam according to Embodiment 2 after completion is substantially the same as the configuration of the binding beam according to Embodiment 1, and regarding the configuration substantially the same as the configuration of Embodiment 1, the same reference numerals and/or names as those used in Embodiment 1 are attached thereto as necessary, and a description thereof will be omitted. The following description covers a steel form forming method and a binding beam construction method in relation to the binding beam according to Embodiment 2. Description will be appropriately omitted as to procedures similar to those of Embodiment 1.
(Steel Form Forming Method)
First, an example of the method for forming the steel form 10 according to Embodiment 2 will be described. First, the Z-steel 11 is manufactured at a factory. At this time, a circular hole 51 is formed in advance at a position corresponding to the web opening forming portion in the Z-steel 11. In other words, in Embodiment 2, the circular hole 51 is provided at each of the positions (six places in total in the drawing) in the side plate portion 13 of the Z-steel 11 that corresponds to the web opening 40 illustrated in
(Binding Beam Construction Method)
The method for constructing a binding beam 50 according to Embodiment 2 will be described below
First, the steel form installation and cylindrical form installation steps are performed as illustrated in
In the cylindrical form installation step, a cylindrical form 52 is inserted into the circular hole 51 formed in the steel form 10. The axial length of the cylindrical form 52 (length in the +X-X direction) exceeds the width of the groove portion of the steel form 10 (length in the +X-X direction), and thus both end portions of the cylindrical form 52 protrude to the outside from the circular hole 51 as illustrated in the drawing. Although the cylindrical form 52 may be hollow or solid and any material can be used for the cylindrical form 52 insofar as the load of concrete can be withstood, the case of a solid wooden form will be described below. After the cylindrical form 52 is installed as described above, the gap between the outer periphery of the cylindrical form 52 and the inner periphery of the circular hole 51 is filled with a sealing material (not illustrated) such as putty. Concrete leakage is deterred as a result.
Subsequently, the main bar arrangement, deck plate installation, and placement steps are performed as illustrated in
Subsequently, the penetration step is performed as illustrated in
Lastly, a duct is passed through the web opening 40 formed in the penetration step. The passage of the duct (not illustrated) is performed by a known method and will not be described in detail. This is the end of the description of the method for constructing the binding beam 50 according to Embodiment 2.
As described above, with the binding beam 50 of Embodiment 2, it is possible to form the web opening 40 simply by removing the cylindrical form 52. Accordingly, it is possible to simplify the work for forming the web opening 40 at a construction site.
The embodiments according to the invention have been described. However, the specific configurations and means of the invention can be modified and improved in any manner within the scope of the technical idea of each invention described in the claims. Such modification examples will be described below.
First of all, the problems to be solved by the invention and the effects of the invention are not limited to the above and may vary with the details of the implementation environment and configuration of the invention, and only some of the problems described above may be solved and only some of the effects described above may be achieved in some cases.
(Inter-Embodiment Relationship)
The features of each embodiment and the features according to each of the following modification examples may be mutually replaced or one feature may be added to another. For example, the web opening 40 may be formed by the method according to Embodiment 1 (with a drill or the like) at the position in the binding beam 50 where the web opening 40 is not formed after the binding beam 50 is formed by the method according to Embodiment 2 (by pre-disposition of the cylindrical form 52 in the web opening forming portion).
(Regarding Dimensions and Materials)
The dimension, shape, material, ratio, and the like of each portion of the binding beams 1 and 50 described in the detailed description of the invention and the drawings are merely examples, and any other dimensions, shapes, materials, ratios, and the like can be used as well. For example, the front-view angle that is formed by the side plate portion 13 and the bottom plate portion 12, the front-view angle that is formed by the side plate portion 13 and the flange portion 14, and the front-view angle that is formed by the flange portion 14 and the reinforcing portion 15 may be obtuse angles or acute angles although each of the angles is a right angle in each of the embodiments as illustrated in
Alternatively, the steel form 10 may be divided in one or more places in the longitudinal direction and joined at an installation site. The position and place of division of the steel form 10 can be determined in any manner. For example, the steel form 10 may be divided into a plurality of units capable of being loaded on a transport vehicle in terms of length. It is preferable that the position of division is a place where the moment that is applied to the post-joining steel form 10 is small. Any joining method is applicable to the steel form 10 after the division. For example, a pair of the steel forms 10 brought in touch with each other in the divided state may be connected via a connection plate (not illustrated) provided on the outside surfaces of the side plate portions 13 of the pair of steel forms 10. A drill screw: a bolt, or the like can be used for fixing of the connection plate to the side plate portion 13. In addition, when the binding beam concrete 20 is placed in the post-joining steel form 10, it is preferable to support the steel form 10 by using a temporary support at the joining point of the steel form 10. By the divided structure being adopted as described above, the manufacturing workability and the transport efficiency of the steel form 10 can be improved. In addition, even the binding beam 1 that has a large span can be built by joining of a plurality of the standard-span binding beams 1.
(Regarding Girder Joining Portion)
Although a case where the girder 2 is a reinforced concrete beam has been described in each embodiment, the invention is not limited thereto and the girder 2 may be, for example, a steel-framed beam.
Alternatively, the swallowing width of the binding beam 1 in the girder 110 may be further increased.
In the example illustrated in
Alternatively, the pair of side plate portions 13 may be simply accommodated in the girder 110 with the height as it is and without the notch 18 being provided.
Alternatively, a part of the pair of side plate portions 13 and a bearing pressure effective part may be swallowed by the girder 110.
Alternatively, the part to be swallowed in the girder 110 may be retrofitted.
The binding beams 1 disposed on both sides of the girder 110 may be connected to each other.
In each of the embodiments, the binding beam concrete 20 and the girder concrete are placed at the same time. However, the invention is not limited thereto and the binding beam concrete 20 and the girder concrete may be placed one by one. In a case where the girder concrete is placed first, for example, the side surface of the solidified girder concrete may be chipped into a shape (hat shape) substantially corresponding to the axial cross-sectional shape of the binding beams 1 and 50 and the binding beam concrete 20 may be placed after the end portion of the steel form 10 of each of the binding beams 1 and 50 is installed at the chipped part.
(Regarding Flange Portion)
Although the flange portion 14 is provided in each embodiment, the flange portion 14 may be omitted and the steel form 10 may be configured as a member having a substantially U-shaped axial cross section. Although the flange portion 14 is provided at the upper end of the side plate portion 13, the invention is not limited thereto and the flange portion 14 may be provided at a position other than the upper end (such as a position that is below the upper end by a predetermined distance (such as several centimeters)).
(Regarding Reinforcing Portion)
Although the reinforcing portion 15 is provided at the outer end of the flange portion 14 in each embodiment, the reinforcing portion 15 may be omitted in a case where the flange portion 14 is capable of enduring the load of concrete. In addition, reinforcing means for further reinforcing the flange portion 14 may be provided in addition to or instead of the reinforcing portion 15. For example, reinforcement may be performed by means of a reinforcing steel plate affixed to the upper surface or the lower surface of the flange portion 14. The steel plate may be affixed through the forward-rearward direction of the flange portion 14 or may be intensively affixed only to a part particularly requiring proof stress (such as the vicinity of the middle of the flange portion 14 in the forward-rearward direction).
Alternatively, the shape of the reinforcing portion 15 may be changed.
The second reinforcing portion 216 can be provided in another aspect as well.
(Regarding Z-Steel)
In each embodiment, the pair of Z-steels 11 are overlapped with each other and bolt-joined. Specific methods for the joining are not limited thereto.
(Regarding Non-Opening Member)
A point that has been described in each embodiment is that a temporary member (member removed before concrete placement) such as a batten and a U-shaped veneer board is provided for fixing of the relative positions of the pair of Z-steels 11 during the formation of the steel form 10 (mutual joining of the pair of Z-steels 11). A permanent member for fixing the relative positions of the pair of Z-steels 11 (member embedded without pre-concrete placement removal, hereinafter, referred to as non-opening member) may be provided instead of or in addition to the temporary member.
The non-opening member 522 illustrated in
(Regarding Main Bar Arrangement Step)
In each embodiment, the main bar arrangement step is performed after the steel form installation step. However, the invention is not limited thereto and the steel form installation step may be performed after the main bar arrangement step. At this time, the main bar 30 is disposed first in the main bar arrangement step, the pair of Z-steels 11 are disposed so as to cover the main bar 30 from below, and in a state where the bottom plate portions 12 of the pair of Z-steels 11 overlap each other, a bolt being inserted from below through the bottom plate portion 12 and thereby the pair of Z-steels 11 may be joined to each other.
One embodiment of the present invention provides a steel-framed concrete beam comprises: a steel form having a bottom plate portion and a pair of side plate portions extending upward from both ends of the bottom plate portion: and concrete placed in a groove portion configured by the bottom plate portion and the pair of side plate portions of the steel form.
According to this embodiment, since an outer shell of the concrete is covered by the steel form, it is possible to suppress a decline in proof stress during the formation of a web opening in the side surface of the beam and it is possible to reduce the labor and cost entailed by separate reinforcing member attachment for forming the web opening.
Another embodiment of the present invention provides the steel-framed concrete beam according to the above embodiment, wherein an allowable bending moment or an allowable shear force of the steel-framed concrete beam is calculated by Equation (1) below: (Equation 1) Fa=FRC+β·FS wherein, Fa: an allowable bending moment or an allowable shear force of the steel-framed concrete beam, FRC: an allowable bending moment or an allowable shear force of the concrete, β: a burden factor of an allowable bending moment or an allowable shear force of the steel form, which is 0.5 or less, and FS: an allowable bending moment or an allowable shear force of the steel form.
According to this embodiment, it is possible to calculate a complex allowable bending moment and a complex allowable shear force taking the respective bearing ratios of the steel form and the concrete into account and it is possible to optimize the design of the steel-framed concrete beam.
Another embodiment of the present invention provides the steel-framed concrete beam according to the above embodiment, wherein a part of the steel-framed concrete beam is joined to a girder, and the steel form is provided with an end portion on the girder side in a longitudinal direction of the steel form, accommodated in the girder via a notch formed in a side surface of the girder, and having a length equal to or greater than a cover thickness of the girder.
According to this embodiment, it is possible to further improve the joining strength of a binding beam and a girder by the girder accommodating the binding beam to the extent of the length, which is equal to or greater than the cover thickness of the girder.
Another embodiment of the present invention provides the steel-framed concrete beam according to the above embodiment, wherein the side plate portion and the concrete have a web opening forming portion allowing formation of a web opening penetrating the side plate portion and the concrete.
According to this embodiment, since the web opening can be formed in the web opening forming portion, piping and wiring and so on can be passed through the web opening, and the convenience of the steel-framed concrete beam can be enhanced. In particular, since an outer shell of the concrete of the steel-framed concrete beam is covered by the steel form, a part where the web opening can be formed is not limited to a part of reinforcing member attachment unlike in the related art, and the degree of freedom of the size and disposition of the web opening can be enhanced
Another embodiment of the present invention provides the steel-framed concrete beam according to the above embodiment, wherein a non-opening member for fixing the pair of side plate portions to each other is provided in a range from an upper end position of the pair of side plate portions to a position below the upper end position by one-third of a height of the pair of side plate portions.
According to this embodiment, since relative positions of the pair of side plate portions can be fixed at a position relatively close to the upper end position of the pair of side plate portions, mutual outward opening of the pair of side plate portions can be more effectively prevented than in a case where the non-opening member is provided at a position below this range.
Another embodiment of the present invention provides the steel-framed concrete beam according to the above embodiment, wherein the steel form is provided with a flange portion extending outward from an upper end of the side plate portion.
According to this embodiment, since the flange portion is provided, load of a slab supported by the steel-framed concrete beam can be received by the flange portion and is allowed to smoothly flow to the steel-framed concrete beam and proof stress of the steel-framed concrete beam is improved.
Another embodiment of the present invention provides the steel-framed concrete beam according to the above embodiment, wherein the steel form is provided with a reinforcing portion extending downward or upward from an outer end of the flange portion.
According to this embodiment, since the reinforcing portion is provided at the outer end of the flange portion, buckling of the flange portion at a time when the concrete is placed on the groove portion or the flange portion of the steel form can be suppressed by the reinforcing portion and the proof stress of the steel-framed concrete beam is improved.
Another embodiment of the present invention provides a method for constructing a steel-framed concrete comprises: a steel form installation step of installing a steel form having a bottom plate portion and a pair of side plate portions extending upward from both ends of the bottom plate portion; and a placement step of placing concrete in a groove portion configured by the bottom plate portion and the pair of side plate portions of the steel form installed in the steel form installation step.
According to this embodiment, since an outer shell of the concrete is covered by the steel form, it is possible to suppress a decline in proof stress during the formation of a web opening in the side surface of the beam and it is possible to reduce the labor and cost entailed by separate reinforcing member attachment for forming the web opening.
Another embodiment of the present invention provides the method for constructing a steel-framed concrete beam according to the above embodiment, wherein an allowable bending moment or an allowable shear force of the steel-framed concrete beam is calculated by Equation (1) below: (Equation 1) Fa=FRC+β·FS wherein, Fa: an allowable bending moment or an allowable shear force of the steel-framed concrete beam, FRC: an allowable bending moment or an allowable shear force of the concrete, β: a burden factor of an allowable bending moment or an allowable shear force of the steel form, which is 0.5 or less, and FS: an allowable bending moment or an allowable shear force of the steel form.
According to this embodiment, it is possible to calculate a complex allowable bending moment and a complex allowable shear force taking the respective bearing ratios of the steel form and the concrete into account and it is possible to optimize the design of the steel-framed concrete beam.
Number | Date | Country | Kind |
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JP2017-036749 | Feb 2017 | JP | national |
This application is a Continuation-In-Part of PCT/W2018/005970 filed Feb. 20, 2018, and claims the priority benefit of Japanese application 2017-036749 filed on Feb. 28, 2017, the contents of which are expressly incorporated by reference herein in their entireties.
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Entry |
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International Preliminary Report on Patentability and Written Opinion in corresponding WIPO Patent Application No. PCT/JP2018/005970, dated Sep. 3, 2019. |
Number | Date | Country | |
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20190376289 A1 | Dec 2019 | US |
Number | Date | Country | |
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Parent | PCT/JP2018/005970 | Feb 2018 | US |
Child | 16549198 | US |