JP7083105B2 - Column base joint structure - Google Patents

Description

The present disclosure relates to a column base joint structure of a reinforced concrete building having multiple layers.

In a reinforced concrete building whose skeleton is composed of columns and beams, the column-beam joints are generally rigidly joined. In such a building, the bending stress during an earthquake is concentrated at the joint between the column base and the foundation structure such as footings, piles, and foundation beams, so it was necessary to increase the cross section of the column bottom and the foundation structure. ..

In recent years, it has been proposed to make a semi-rigid joint for joining the bottom layer column base to the foundation structure. For example, in Patent Document 1, by not connecting a part of the main bar of the column to the foundation structure, the bending rigidity of the column base joint is reduced to avoid stress concentration on the bottom layer of the building, and the column By reducing the cross section of the lower end part from the cross section of the middle part of the column, the outer peripheral surface of the lower end of the column, which is the fulcrum when a horizontal load is applied, is brought closer to the central axis of the column, and the concrete part around the fulcrum. It is described that the amount of deformation of the concrete portion is reduced, thereby suppressing the damage of the concrete part.

Japanese Unexamined Patent Publication No. 2016-173007

As shown in FIG. 8, the inventors of the present invention have a step in which a pillar 2 is erected on the foundation structure 1 between the side surface of the lower end portion 3 of the pillar 2 and the side surface of the intermediate portion 4. An experiment was conducted in which a test piece was prepared in which the width of the lower end portion 3 was about 0.7 times the width of the middle portion 4 and the height of the lower end portion 3 was about 100 mm so as to occur, and the seismic force was applied. As a result, a large local stress is generated at the joint portion between the lower end portion 3 and the intermediate portion 4, the lower end portion 3 is sunk into the intermediate portion 4, and the intermediate portion 4 is further joined with the outer edge of the lower end portion 3. I found a problem that vertical cracks occur from.

Therefore, the present invention reduces the bending rigidity of the column base joint in order to avoid stress concentration on the lowest layer at the time of an earthquake in the column base joint structure of a reinforced concrete building having a plurality of layers, and concrete. It is an object of the present invention to provide a column base joint structure capable of suppressing damage to the column base. In at least some embodiments of the present invention, it is an object of the present invention to provide a column base joint structure capable of suppressing the occurrence of the above-mentioned indentation and vertical cracking.

At least some embodiments of the present invention are column base joint structures (10, 30, 40, 50, 60) formed to avoid stress concentration on the bottom layer in a multi-story building. The foundation structure (11) made of reinforced concrete, the first main reinforcement (18, 32, 42, 68) erected on the foundation structure and connected to the foundation structure, and the foundation structure. It is equipped with a reinforced concrete column (12,31,41,51,61) having a second main bar (19,33,43,69) that is not connected, and the column has a constant cross-sectional contour in the vertical direction. It has an extending intermediate portion (14, 52, 62) and a lower end portion (15, 53, 63) extending downward from the intermediate portion and having a smaller cross section than the intermediate portion. The height of the portion is characterized by being 0.3 to 1.5 times the width or diameter of the intermediate portion.

According to this configuration, since the second main bar is not connected to the foundation structure, the bending rigidity between the column and the foundation structure is reduced, and stress concentration on the bottom layer of the building during an earthquake is avoided. Can be done. Further, since the height of the lower end portion is 0.3 times or more the width of the middle portion, the bending moment generated at the boundary portion between the intermediate portion and the lower end portion is lower than the height of the lower end portion. It is reduced compared to the case, and damage to the concrete at the boundary between the middle part and the lower end part is suppressed. Further, since the height of the lower end portion is 1.5 times or less the width of the middle portion, the appearance is not impaired.

In the column base joining structure (10, 30, 40, 60) according to at least some embodiments of the present invention, the lower end portion (15, 63) is the intermediate portion (14, 62) in the above configuration. It is characterized by having a tapered portion (16, 64) that tapers downward from the lower end of the.

According to this configuration, a tapered portion is provided so that a step does not occur between the side surface of the intermediate portion and the side surface of the lower end portion, so that the lower end portion is prevented from being sunk into the middle portion and vertical cracks caused by squeezing are suppressed. Will be done.

In the above-mentioned configuration having a tapered portion, the column base joining structure according to at least some embodiments of the present invention has the lower end portion downward from the lower end of the tapered portion so that the side surface extends in the vertical direction. It is characterized by having a rising portion that extends and joins to the foundation structure.

According to this configuration, the force generated at the boundary between the foundation structure and the column is dispersed at the rising portion, so that damage to the concrete around the boundary can be suppressed.

In the column base joint structure (10, 30, 40) according to at least some embodiments of the present invention, in the above configuration, the side surface of the tapered portion is the horizontal length with respect to the vertical length as a whole. It is characterized in that the gradient represented by the ratio of the vertical is inclined so as to be 1/6 to 1/2. Preferably, the gradient is 1/6 to 1/3.

According to this configuration, by setting the slope of the side surface of the tapered portion to 1/6 or more, the width of the lower end side of the tapered portion is made narrower than the width of the intermediate portion by a predetermined value or more while suppressing the height of the tapered portion. be able to. Further, if the slope of the side surface of the tapered portion is too large, tensile stress may be generated near the lower end of the intermediate portion and the concrete portion may be damaged. Since the tensile stress can be suppressed and the gradient thereof is 1/3 or less, such tensile stress can be further suppressed or prevented.

Further, in the column base joining structure (10, 30) according to at least some embodiments of the present invention, in the above configuration having a tapered portion, the first main bar (18, 32) is the lower end in a plan view. The second main bar (19, 33) is arranged inside the contour line of the lower end of the portion, and at least a part of the second main bar (19, 33) is arranged outside the first main bar in a plan view.

According to this configuration, it is not necessary to bend the first main bar and the second main bar, and the first main bar and the second main bar can be extended in the vertical direction, so that the bar arrangement work becomes easy.

Further, in the above configuration, the column base joint structure (30) according to at least some embodiments of the present invention is outside the first main bar (32) and at least a part of the second main bar (33). A third main bar (34) which is arranged inside the structure and is not connected to the basic structure is further provided, and the upper end of the third main bar is above the upper end of the first main bar and at least a part of the said. It is characterized in that it is located below the upper end of the second main bar, and the lower end of the third main bar is located below the lower end of the second main bar.

According to this configuration, the first main bar, the third main bar, and the second main bar are arranged stepwise from the inside toward the upper side, so that the bending strength of the region where the main bar at the lower part of the column is divided is stable. Can be made to.

In the column base joint structure (40) according to at least some embodiments of the present invention, the first main bar (42) is the above-mentioned structure having a tapered portion except for the two directly above the structure. In the intermediate portion, at least a part of the main bar arranged outside the lower end of the lower end portion in a plan view is formed, and in the tapered portion, along the side surface of the tapered portion. It is characterized by being inclined.

According to this configuration, since the first main bar connected to the foundation structure is arranged along the side surface of the column, the bending strength of the entire column is stable.

Further, in the column base joint structure (50) according to at least some embodiments of the present invention, in the above-mentioned first configuration, the side surface of the lower end portion (53) is along the vertical direction as a whole. It is characterized by being extended.

According to this configuration, when the pillar is formed of cast-in-place concrete, it is not necessary to incline the formwork, and the installation work of the formwork becomes easy.

Further, in the column base joining structure according to at least some embodiments of the present invention, in the above configuration, the intermediate portion has a steel plate (54) extending in the horizontal direction at the lower end thereof, and is viewed in a plan view. The steel plate is characterized in that it covers the lower end portion.

According to this configuration, there is a step between the side surface of the lower end portion and the side surface of the intermediate portion. It is possible to suppress the occurrence of vertical cracks.

Further, in the column base joint structure (60) according to at least some embodiments of the present invention, in the second or third configuration, the intermediate portion (62) has a prismatic shape and the taper. The portion (64) is characterized in that it has a shape in which at least a part of the corner portion on the lower end side is cut out from the prism corresponding to the intermediate portion.

According to this configuration, since the reduction rate of the effective force with respect to the bending moment of the tapered portion is relatively small, it is suitable for the outer column in which the axial force fluctuates greatly.

Further, in the column base joining structure (60) according to at least some embodiments of the present invention, in the above configuration, the first main bar (68) is the contour of the lower end of the lower end portion (63) in a plan view. The second main bar (69) is arranged inside the line, and at least a part of the second main bar (69) is arranged outside the contour line at the lower end of the lower end portion in a plan view.

According to this configuration, it is not necessary to bend the first main bar and the second main bar, and the first main bar and the second main bar can be extended in the vertical direction, so that the bar arrangement work becomes easy.

According to the present invention, in a column base joint structure of a reinforced concrete building having a plurality of layers, the bending rigidity of the column base joint is reduced in order to avoid stress concentration on the lowest layer at the time of an earthquake, and concrete is used. It is possible to provide a column base joint structure capable of suppressing damage to the column base. According to at least some embodiments of the present invention, it is possible to provide a structure capable of suppressing the occurrence of denting and vertical cracking in the vicinity of the lower end of the column.

Reinforcement diagram of column base joint structure according to the first embodiment (a: front view, b: Ib-Ib cross-sectional view in a view, c: Ic-Ic cross-sectional view in a figure) Schematic vertical cross-sectional view of the column base joint structure according to the first modification of the first embodiment. Reinforcement diagram of column base joint structure according to the second modification of the first embodiment (a: front view, b: cross-sectional view of IIIb-IIIb in the figure a, cross-sectional view of IIIc-IIIc in the figure c: a). ) Reinforcement diagram of column base joint structure according to the second embodiment (a: front view, b: IVb-IVb cross-sectional view in a figure, c: IVc-IVc cross-sectional view in a figure) Perspective view of the column of the column base joint structure according to the third embodiment Reinforcing diagram of column base joint structure according to the third embodiment (a: front view, b: Vb-Vb cross-sectional view in a view, c: Vc-Vc cross-sectional view in a view, d: a view) Vd-Vd sectional view in FIG. E: Ve-Vc sectional view in FIG. A) FEM analysis result of column base joint structure according to comparative example FEM analysis result of column base joint structure according to comparative example FEM analysis result of column base joint structure according to Example FEM analysis result of column base joint structure according to Example FEM analysis result of column base joint structure according to Example FEM analysis result of column base joint structure according to Example FEM analysis result of column base joint structure according to Example FEM analysis result of column base joint structure according to Example FEM analysis result of column base joint structure according to Example FEM analysis result of column base joint structure according to Example Schematic front view of column base joint structure according to the prior art

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the main embodiment of the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a bar arrangement diagram of the column base joint structure 10 according to the first embodiment.

The column base joint structure 10 is a structure in which a reinforced concrete column 12 is erected on a footing 11, and is applied to the lowest layer of a building having a plurality of layers.

The footing 11 is a reinforced concrete member that transmits the load from the column 12 to the ground, and extends in the horizontal direction. The footing 11 includes a footing main bar 13 extending in the horizontal direction, a fixing bar (not shown) extending in the vertical direction and the lower end side plunging into a pile (not shown) to fix the footing 11 to the pile, and a stirrups. Has (not shown). Instead of the footing 11, the pillar 12 may be erected on another foundation structure such as a pile or a foundation beam.

The pillar 12 is a reinforced concrete member that supports the load of the superstructure of the building and transmits the load to the footing 11, and is erected on the footing 11. The pillar 12 has a square contour in a plan view, but may be changed to a rectangle or a contour such as another polygon, a circle, an ellipse, or an ellipse. The pillar 12 has an intermediate portion 14 extending in the vertical direction with a constant cross-sectional contour, and a lower end portion 15 having a cross section extending downward from the lower end of the intermediate portion 14 and having a smaller cross section than the intermediate portion 14. ..

The lower end portion 15 has a tapered portion 16 that tapers downward from the lower end with the intermediate portion 14. That is, the cross section of the upper end of the tapered portion 16 matches the cross section of the intermediate portion 14, and the side surface of the tapered portion 16 is inclined inward as it goes downward. Each of the side surfaces of the tapered portion 16 is formed so that the downward extension surface of the side surface of the intermediate portion 14 is bent inward at the lower end of the intermediate portion 14. The ratio of the horizontal length to the vertical length indicating the slope of the four inclined side surfaces (horizontal length / vertical length) is 1/6 to 1/2. The slopes of the four sloping sides are preferably equal to each other, but may be different. FIG. 1 illustrates the case where the slopes of the four sides are equal to each other and 1/3. The width of the lower end of the tapered portion 16 is 0.5 to 0.9 times the width of the intermediate portion 14, preferably about 0.7 times (when converted to the cross-sectional area, the cross-sectional area of the lower end of the tapered portion 16 is It is 0.25 to about 0.8 times, preferably about 0.5 times the cross-sectional area of the intermediate portion 14.

The lower end portion 15 has a rising portion 17 that extends downward from the lower end of the tapered portion 16 so that the side surface extends in the vertical direction and is joined to the footing 11. The cross section of the rising portion 17 matches the cross section of the lower end of the tapered portion 16. The alternate long and short dash line in FIG. 1B shows the outline of the rising portion 17. The height of the rising portion 17 is preferably about 100 mm to about 0.6 times the width of the intermediate portion 14, and more preferably about 100 mm. The rising portion 17 may be omitted, and the lower end portion 15 may have a structure consisting of only the tapered portion 16.

The height of the lower end portion 15 is the shortest of the width of the intermediate portion 14 (the width in the short side direction when the shape of the cross section of the intermediate portion 14 is rectangular, and the width passing through the center of the polygon when the shape of the intermediate portion 14 is polygonal). Width, diameter for circles, minor diameter for ellipses and ellipses) about 0.3 times (for example, the width of the lower end of the tapered portion 16 is 0.7 times the width of the intermediate portion 14, and the gradient is 1/2. (In the case of no rising portion 17) to 1.5 times (for example, the width of the lower end of the tapered portion 16 is 0.7 times the width of the intermediate portion 14, the gradient is 1/6, and the height of the rising portion 17 is the intermediate portion 14. It is preferably about 0.45 times (for example, the width of the lower end of the tapered portion 16 is 0.7 times the width of the intermediate portion 14, the gradient is 1/3, and the rising portion). (Without 17) to about 1.0 times (for example, the width of the lower end of the tapered portion 16 is 0.7 times the width of the intermediate portion 14, the gradient is 1/6, the height of the rising portion 17 is 100 mm, and the intermediate portion 14 When the width of is 1000 mm).

The pillar 12 includes a first main bar 18 connected to the footing 11 and extending in the vertical direction, a second main bar 19 not connected to the footing 11 and extending vertically in the intermediate portion 14, and a band bar 20. It has a plumb bob 21. Each of the first main bars 18 is arranged inward from the side surface of the lower end of the lower end portion 15 in a plan view, extends in the vertical direction, extends from the lower end of the column 12 through the middle portion 14 and the lower end portion 15. It reaches the inside of the footing 11. Since the lower end side of the first main bar 18 is inserted into the footing 11, the pillar 12 and the footing 11 are connected to each other. The second main bar 19 is arranged outside the first main bar 18 in a plan view, and the tapered portion 16 is inclined along the side surface of the tapered portion 16 with respect to the vertical direction. The second main bar 19 extends in the vertical direction as a whole, and its lower end is configured to be located at a position where a predetermined cover can be secured, for example, near the boundary between the intermediate portion 14 and the lower end portion 15. May be good. Since the second main bar 19 does not rush into the footing 11, the pillar 12 and the footing 11 are not connected. It is preferable that the total cross-sectional area of the first main bar 18 is smaller than the total cross-sectional area of the second main bar 19. FIG. 1 shows an example in which all the second main bars 19 are arranged at positions along the side surface of the intermediate portion 14, but there may be second main bars 19 arranged at other positions. The band bar 20 is arranged so as to surround the first main bar 18 at the lower end portion 15, and is arranged so as to surround the second main bar 19 arranged outside at the intermediate portion 14. The number and intervals of the band muscles 20 are appropriately changed. The auxiliary band bars 21 are arranged between the band bars 20 so as to be close to the first main bar 18 and the second main bar 19 along the horizontal direction parallel to the side surface of the pillar 12. The number and spacing of the accessory bars 21 are changed as appropriate, and are not installed when unnecessary. In the tapered portion 16, the reinforcing bar 22 is arranged so as to surround the second main bar 19. The second main bar 19 and the reinforcing bar 22 in the tapered portion 16 cooperate with each other to suppress the peeling of concrete in the tapered portion 16.

The first main bar 18 constitutes the main bar of the pillar 12 in that it resists bending and that it is arranged with a predetermined cover along the outer circumference of the pillar 12. However, the first main bar 18 extends from the column 12 to the footing 11, and in the column 12, it suffices to extend in the vertical direction by at least the fixing length, and does not necessarily extend over the entire height of the column 12. You don't have to.

The action and effect of the column base joint structure 10 will be described. Since the second main bar 19 is not connected to the footing 11 and the first main bar 18 is arranged inside the second main bar 19, the column 12 and the structure are compared with the structure in which all the main bars are connected to the foundation. The joint portion with the footing 11 has low rigidity against bending. Therefore, in a building having a plurality of layers, stress concentration on the lowest layer at the time of an earthquake can be avoided, and the cross section of the column 12 or a part of the beam (not shown) can be reduced. In particular, when the total cross-sectional area of the first main bar 18 is smaller than the total cross-sectional area of the second main bar 19, this effect becomes remarkable.

Further, since the height of the lower end portion 15 is 0.3 times or more the width of the intermediate portion 14, the force generated at the boundary portion between the intermediate portion 14 and the lower end portion 15 is dispersed, and the lower end portion 15 The stress is reduced as compared with the case where the height is low, and damage to the concrete at the boundary portion between the intermediate portion 14 and the lower end portion 15 is suppressed. Further, since the tapered portion 16 is provided so that a step does not occur between the side surface of the intermediate portion 14 and the side surface of the lower end portion 15, vertical cracks caused by the lower end portion 15 being recessed into the intermediate portion 14 or being recessed are generated. It is suppressed. Further, since the height of the lower end portion 15 is 1.5 times or less the width of the intermediate portion 14, the appearance is not impaired. Further, by setting the slope of the side surface of the tapered portion 16 to 1/6 or more, the cross section on the lower end side of the tapered portion 16 can be sufficiently reduced while suppressing the height of the tapered portion 16. Further, if the slope of the side surface of the tapered portion 16 is too large, tensile stress may be generated near the lower end of the intermediate portion 14 and the concrete portion may be damaged. Such tensile stress can be suppressed, and when the gradient is 1/3 or less, the tensile stress can be further suppressed or prevented.

Since the first main bar 18 and the second main bar 19 extend in the vertical direction, it is not necessary to bend the first main bar 18, and the bar arrangement work becomes easy.

Further, when the rising portion 17 is provided, the force generated at the boundary portion between the footing 11 and the pillar 12 is dispersed as compared with the case where the rising portion 17 is not provided, so that damage to the concrete portion can be suppressed.

The first embodiment can be modified with respect to the arrangement of the main bar. FIG. 2 shows a first modification of the first embodiment. FIG. 2 shows the reinforcement arrangement state of the first to third main bars 32, 33, 34 in the vertical cross section of the column 31 in the column base joint structure 30 according to the first modification of the first embodiment. Is schematically shown (the zonal muscle and the accessory zonal muscle are not shown). In the description, the same configurations as the above configurations are designated by the same reference numerals, and the description thereof will be omitted.

The first to third main bars 32, 33, and 34 extend in the vertical direction, respectively. The first main bar 32 connected to the footing 11 (see FIG. 1) is located on the innermost side, and is arranged inside the side surface of the lower end of the lower end portion 15 in a plan view. The second main bar 33, which is not connected to the footing 11, is arranged on the outermost side. The third main bar 34 is not connected to the footing 11 and is arranged between the first main bar 32 and the second main bar 33 in the proximity separation direction with respect to the central axis. The upper end of the first main bar 32 is preferably located in the intermediate portion 14, the upper end of the third main bar 34 is located above the upper end of the first main bar 32, and the upper end of the second main bar 33 is the third main bar 34. Located above the top edge of. The lower end of the third main bar 34 is located below the lower end of the second main bar 33, preferably located within the tapered portion 16. Further, the upper end of the first main bar 32 is located above the lower end of the second main bar 33 so that the first to third main bars 32, 33, 34 have sections overlapping each other in the vertical direction. .. In other words, the first to third main bars 32, 33, 34 are arranged stepwise so as to be located lower as they are arranged inward.

In this way, even if the first to third main muscles 32, 33, and 34 are arranged stepwise, the same action and effect as those of the main embodiment of the above-mentioned first embodiment are exhibited, and the first to third muscles separated from each other are exhibited. By arranging the three main bars 32, 33, and 34 in stages, they resist the bending moment like the main bars that are continuous in the vertical direction, and the bending strength of the column 31 is stabilized.

FIG. 3 shows a column base joint structure 40 according to a second modification of the first embodiment. In the description, the same configurations as the above configurations are designated by the same reference numerals, and the description thereof will be omitted.

The first main bar 42 of the column 41 connected to the footing 11 constitutes a part of the main bar arranged on the outermost side, and the intermediate portion 14 of the column 41 extends in the vertical direction and has a tapered portion 16. In, it extends along the sloping sides. The lower end side of the first main bar 42 is fixed to the footing 11 in a state of being bent in the vicinity of the rising portion 17 and extending in the vertical direction, but the footing 11 is in a state of being inclined without bending in the vicinity of the rising portion 17. It may be fixed to.

The second main bar 43 extending in the vertical direction without being connected to the footing 11 is the inner second main bar 43a arranged inside the first main bar 42 in a plan view and the same as the first main bar 42 in a plan view. It includes an outer second main bar 43b that constitutes a part of the main bar arranged on the outside. The lower end side of the inner second main bar 43a extends to a position in the tapered portion 16 that does not hinder the arrangement of the first main bar 42 or a position where a predetermined cover can be maintained. The upper end of the inner second main bar 43a is located lower than the upper end of the first main bar 42. The lower end of the outer second main bar 43b is located near the boundary between the intermediate portion 14 and the lower end portion 15. The upper end side of the outer second main bar 43b extends upward like the first main bar 42. It is preferable that the total cross-sectional area of the first main bar 42 is smaller than the total cross-sectional area of the second main bar 43. The band bar 20 is arranged so as to surround the first main bar 42 at the lower end portion 15, and surrounds the first main bar 42 and the outer second main bar 43b at the intermediate portion 14. As the second main bar 43, only one of the inner second main bar 43a or the outer second main bar 43b may be provided.

Generally, when a reinforcing bar is bent and tilted, it is considered that it can be used without any special consideration if the gradient is 1/6 (horizontal length / vertical length) or less. Therefore, in this modification, the slope of the side surface of the tapered portion 16 and the slope of the first main bar 42 in the tapered portion 16 is preferably 1/6 as shown in FIG.

The column base joining structure 40 according to the second modification also has the same action and effect as the main embodiment of the first embodiment, and the first main bar 42 can be arranged along the side surface of the column 41 over the entire height of the column 41. Therefore, the bending strength of the entire column 41 is stable.

Next, the column base joining structure 50 according to the second embodiment will be described with reference to FIG. In the column base joining structure 50 according to the second embodiment, the configurations of the intermediate portion 52 and the lower end portion 53 of the column 51 are different from those of the first embodiment. The same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The lower end portion 53 of the pillar 51 of the second embodiment has a smaller cross section than the intermediate portion 52, but the side surface is not inclined and the entire side surface extends along the vertical direction. Therefore, a step is formed between the side surface of the intermediate portion 52 and the side surface of the lower end portion 53. The width of the lower end portion 53 is 0.5 to 0.9 times the width of the intermediate portion 52, and is preferably about 0.7 times. The height of the lower end portion 53 is about 0.3 times to 1.5 times the width of the intermediate portion 52, and is preferably about 0.45 times to 1.0 times. The alternate long and short dash line in FIG. 4B shows the outline of the lower end portion 53.

The intermediate portion 52 preferably has a steel plate 54 extending in the horizontal direction at the lower end. In plan view, the steel plate 54 covers at least the lower end portion 53, and preferably the contour of the steel plate 54 coincides with the side surface of the intermediate portion 52.

The operation and effect of the column base joint structure 50 according to the second embodiment will be described. Due to the arrangement of the first main bar 18 and the second main bar 19 and the shape of the cross section of the lower end 53, it is possible to avoid stress concentration on the lowest layer at the time of an earthquake in a building having a plurality of layers, and the columns 51 and Damage to the concrete at the boundary between the intermediate portion 52 and the lower end portion 53 due to the fact that the cross section of some beams (not shown) can be reduced and that the lower end portion 53 has a predetermined range of height. Is suppressed and the appearance is not impaired, which is the same as that of the first embodiment.

In the second embodiment, unlike the first embodiment, the side surface of the lower end portion 53 is not inclined, and a step is generated between the side surface of the lower end portion 53 and the side surface of the intermediate portion 52. Therefore, a steel plate 54 is installed at the lower end of the intermediate portion 52 to prevent the lower end portion 53 from being sunk into the intermediate portion 52 and from causing vertical cracks due to the squeezing.

Further, when the pillar 51 is created by casting in the field, it is not necessary to incline the formwork for forming the lower end portion 53, which facilitates the installation work of the formwork.

Next, the column base joining structure 60 according to the third embodiment will be described with reference to FIGS. 5 and 6. In the column base joining structure 60 according to the third embodiment, the configurations of the intermediate portion 62 and the lower end portion 63 of the column 61 are different from those of the first embodiment. The same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The intermediate portion 62 of the pillar 61 has a square contour in a plan view, but may be changed to a rectangular or other polygonal contour.

The lower end portion 63 has a tapered portion 64 that tapers downward from the lower end with the intermediate portion 14. The side surface of the tapered portion 64 includes a triangular first side surface 65 formed by cutting out the lower corner portion of the prism, and a trapezoidal second side surface 66 forming the same plane as the side surface of the intermediate portion 62. The tapered portion 64 is tapered downward due to the inclination of the first side surface 65 with respect to the vertical direction.

The ratio of the length of the lower base of the second side surface 66 (lower base length / vertical length) to the vertical length indicating the slope of the four inclined first side surfaces 65 is 1/3 to 1/2. be. The slopes of the four sloping sides are preferably equal to each other, but may be different. The ratio of the length of the lower side of the first side surface 65 of the tapered portion 64 to the length of the upper side (the boundary between the intermediate portion 62 and the lower end portion 63) is 1:15 to 5: 4.

Similar to the first embodiment, the lower end portion 63 has a rising portion 67 that extends downward from the lower end of the tapered portion 64 so that the side surface extends in the vertical direction and is joined to the footing 11. The rising portion 67 may be omitted, and the lower end portion 63 may have a structure consisting of only the tapered portion 64. The relationship between the height of the lower end portion 15 and the width of the middle portion 14 is the same as that of the first embodiment.

The column 61 has a first main bar 68 connected to the footing 11 and extending in the vertical direction, a second main bar 69 not connected to the footing 11 and extending in the vertical direction, and a band bar 70. The first main bar 68 is arranged inside the contour line of the lower end of the lower end portion 63 in a plan view. Further, the first main bar 68 is vertically extending from the inside of the side surface of the intermediate portion 62 and the first main bar A68a extending vertically along the second side surface 66 of the tapered portion 64 and the vicinity of the lower end of the first side surface 65 of the tapered portion 64. It has a first main bar B68b extending in the direction, and the lower ends thereof plunge into the footing 11. The second main bar 69 is arranged outside the contour line of the lower end of the lower end portion 63 in a plan view, extends vertically along the corner portion and / or its vicinity of the intermediate portion 62, and the lower end thereof is generally. , Located near the boundary between the middle portion 62 and the lower end portion 63. In the intermediate portion 62, the bending strength of the upper side may be lower than that of the lower side, so that the amount of the upper main bar may be smaller than the amount of the lower main bar. For example, as shown in the figure, the upper end of the first main bar B68b may be lower than the upper ends of the first main bar A68a and the second main bar 69.

Since the band bar 70 is arranged so as to surround the first main bar 68, the concrete portion arranged outside the band bar 70 in the tapered portion 64 becomes large. In that portion, a first reinforcing bar 71 arranged along the boundary line between the first side surface 65 and the second side surface 66, and a second reinforcing bar 71 arranged so as to surround the first main bar A68a and the first reinforcing bar 71. Reinforcing is performed by the reinforcing bar 72 to suppress the peeling of the concrete surface of the tapered portion 64. The second reinforcing bar 72 has a common reinforcing bar length as compared with the reinforcing bar 22 of the first embodiment, and the reinforcing bar arrangement is easy.

The column base joint structure 60 according to the third embodiment has substantially the same effect as that of the first embodiment. Further, in the third embodiment, when the height of the first side surface 65 of the tapered portion 64 is set to be about the same as the height of the side surface of the tapered portion 16 of the first embodiment, the cross-sectional area and cross section of the lower end of the tapered portion 64. If the secondary moment is about the same, the effect produced by reducing the bending rigidity of the column base in the third embodiment is the same as that in the first embodiment. However, since the column base joining structure 60 according to the third embodiment has a relatively large effect on the bending moment at the lower end of the tapered portion 64, it is suitable for use on an outer column in which the axial force greatly fluctuates.

FEM analysis was performed on the column base joint structure according to the example of the prior art and the embodiment of the present invention. The width of the middle portion of the pillar was 1000 mm × 1000 mm, and the width of the lower end side of the lower end portion was 700 mm × 700 mm. Examples correspond to the main embodiment of the first embodiment or the second embodiment. The conditions of the conventional example and the embodiment are as follows.
(A) Conventional example 1: Rigid joint, no lower end.
(B) Conventional example 2: Semi-rigid joint, the lower end is upright, and the height is 100 mm.
(C) Example: Corresponding to the second embodiment, there is a steel plate, and the height of the lower end is 500 mm.
(D) Example: An example in which the steel plate is removed from Example C.
(E) Example: Corresponding to the main embodiment of the first embodiment, the gradient (taper) is 1/6, the height of the tapered portion is 900 mm, and the height of the rising portion is 100 mm.
(F) Example: Corresponding to the main embodiment of the first embodiment, the gradient is 1/3, the height of the tapered portion is 450 mm, and there is no rising portion.
(G) Example: Corresponding to the main embodiment of the first embodiment, the gradient is 1/3, the height of the tapered portion is 450 mm, and the height of the rising portion is 100 mm.
(H) Example: Corresponding to the main embodiment of the first embodiment, gradient 3/11, height of tapered portion 550 mm, no rising portion (example where the height of the lower end portion is equal to that of Example G and there is no rising portion). ..
(I) Example: Corresponding to the main embodiment of the first embodiment, the gradient is 1/2, the height of the tapered portion is 300 mm, and there is no rising portion.
(J) Example: Corresponding to the main embodiment of the first embodiment, the gradient is 1/2, the height of the tapered portion is 300 mm, and the height of the rising portion is 100 mm.

As shown in FIG. 7 (B), in the conventional semi-rigid joint type column, unlike the conventional rigid joint type column shown in FIG. 7 (A), the width is narrowed in the lower part of the middle portion. A large tensile stress (stress indicated by minus) is generated in the vicinity of the portion where the upper edge of the lower end portion hits the lower surface of the intermediate portion. In addition, a large compressive stress (stress indicated by plus) is generated on the right side surface of the lower end portion.

As shown in FIGS. 7 (C) and 7 (D), in the example in which the lower end portion narrower than the intermediate portion is made upright and the height thereof is higher than the conventional example, the conventional example shown in FIG. 7 (B) is used. In comparison, the compressive stress is dispersed over a wide range. Therefore, it is considered that damage due to compressive stress can be suppressed. Further, when the steel plate is installed as shown in FIG. 7C, the steel plate can prevent the lower end portion from being sunk into the intermediate portion, thereby suppressing vertical cracks generated from the lower end portion of the intermediate portion.

As shown in FIGS. 7 (E) to 7 (H), when a tapered portion is provided at the lower end portion and the gradient of the side surface of the tapered portion is set to 1/6 to 1/3, a large tensile stress is applied to the lower end of the intermediate portion. It did not occur. Therefore, it is possible to prevent or prevent the lower end portion from being sunk into the intermediate portion and vertical cracks from the boundary between the intermediate portion and the lower end portion upward.

Comparing the case where there is a rising portion (FIG. 7 (G)) and the case where there is no rising portion (FIGS. 7 (F) and (H)), when there is a rising portion, the compressive force generated near the boundary between the footing and the column is generated. Are dispersed in the rising part. Therefore, by providing the rising portion, damage to the concrete near the boundary between the footing and the pillar can be suppressed.

As shown in FIGS. 7 (I) and 7 (J), when the gradient of the side surface of the tapered portion was 1/2, tensile stress was generated near the lower end of the intermediate portion, but the range was small. Therefore, it is possible to prevent the lower end portion from being sunk into the intermediate portion and vertical cracks from the boundary between the intermediate portion and the lower end portion upward.

Although the description of the specific embodiment is completed above, the present invention can be widely modified without being limited to the above embodiment. For example, an edge cutting member such as a steel plate may be arranged at the lower end of the lower end portion to cut the concrete joint between the foundation structure and the pillar. The pillar may be cast-in-place concrete or precast concrete.

10, 30, 40, 50, 60: Column base joint structure 11: Footing (foundation structure)
12, 31, 41, 51, 61: Pillar 15, 52, 62: Intermediate part 16, 53, 63: Lower end part 17, 64: Tapered part 18, 67: Rising part 19, 32, 42, 68: First main bar 20, 33, 43, 69: 2nd main bar 34: 3rd main bar 54: steel plate

Claims (9)

In a building with multiple layers, it is a column base joint structure formed to avoid stress concentration on the lowest layer.
Reinforced concrete foundation structure and
It is provided with a first main bar erected on the foundation structure and connected to the foundation structure, and a reinforced concrete column having a second main bar not connected to the foundation structure.
The pillar has an intermediate portion extending in a vertical direction with a constant cross-sectional contour, and a lower end portion extending downward from the intermediate portion and having a smaller cross-sectional section than the intermediate portion. The height of the middle portion is 0.3 to 1.5 times the width or diameter of the middle portion .
The lower end portion has a tapered portion that tapers downward from the lower end portion of the intermediate portion.
The column base joining structure is characterized in that the lower end portion extends downward from the lower end of the tapered portion so that the side surface extends in the vertical direction, and has a rising portion to be joined to the foundation structure. In a building with multiple layers, it is a column base joint structure formed to avoid stress concentration on the lowest layer.
Reinforced concrete foundation structure and
It is provided with a first main bar erected on the foundation structure and connected to the foundation structure, and a reinforced concrete column having a second main bar not connected to the foundation structure.
The pillar has an intermediate portion extending in a vertical direction with a constant cross-sectional contour, and a lower end portion extending downward from the intermediate portion and having a smaller cross-sectional section than the intermediate portion. The height of the middle portion is 0.3 to 1.5 times the width or diameter of the middle portion.
The lower end portion has a tapered portion that tapers downward from the lower end portion of the intermediate portion.
The side surface of the tapered portion is inclined so that the gradient represented by the ratio of the horizontal length to the vertical length is 1/6 to 1/2 over the entire column. Leg joint structure. The column base joining structure according to claim 2 , wherein the side surface of the tapered portion is inclined so that the gradient is 1/6 to 1/3 over the entire surface. The first main bar is arranged inside the contour line of the lower end of the lower end portion in a plan view.
The column base joining structure according to any one of claims 1 to 3 , wherein at least a part of the second main bar is arranged outside the first main bar in a plan view. In a building with multiple layers, it is a column base joint structure formed to avoid stress concentration on the lowest layer.
Reinforced concrete foundation structure and
It is provided with a first main bar erected on the foundation structure and connected to the foundation structure, and a reinforced concrete column having a second main bar not connected to the foundation structure.
The pillar has an intermediate portion extending in a vertical direction with a constant cross-sectional contour, and a lower end portion extending downward from the intermediate portion and having a smaller cross-sectional section than the intermediate portion. The height of the middle portion is 0.3 to 1.5 times the width or diameter of the middle portion.
The lower end portion has a tapered portion that tapers downward from the lower end portion of the intermediate portion.
The first main bar is arranged inside the contour line of the lower end of the lower end portion in a plan view.
At least a part of the second main bar is arranged outside the first main bar in a plan view.
Further comprising a third main bar located outside the first main bar and inside at least a portion of the second main bar and not connected to the foundation structure.
The upper end of the third main bar is located above the upper end of the first main bar and below the upper end of at least a part of the second main bar, and the lower end of the third main bar is the lower end of the second main bar. A column base joint structure characterized by being located below. In a building with multiple layers, it is a column base joint structure formed to avoid stress concentration on the lowest layer.
Reinforced concrete foundation structure and
It is provided with a first main bar erected on the foundation structure and connected to the foundation structure, and a reinforced concrete column having a second main bar not connected to the foundation structure.
The pillar has an intermediate portion extending in a vertical direction with a constant cross-sectional contour, and a lower end portion extending downward from the intermediate portion and having a smaller cross-sectional section than the intermediate portion. The height of the middle portion is 0.3 to 1.5 times the width or diameter of the middle portion.
The lower end portion has a tapered portion that tapers downward from the lower end portion of the intermediate portion.
The first main bar constitutes at least a part of the main bar arranged outside the lower end of the lower end portion in a plan view in the intermediate portion, and the taper is included in the tapered portion. A column base joint structure characterized by being inclined along the side surface of the part. In a building with multiple layers, it is a column base joint structure formed to avoid stress concentration on the lowest layer.
Reinforced concrete foundation structure and
It is provided with a first main bar erected on the foundation structure and connected to the foundation structure, and a reinforced concrete column having a second main bar not connected to the foundation structure.
The pillar has an intermediate portion extending in a vertical direction with a constant cross-sectional contour, and a lower end portion extending downward from the intermediate portion and having a smaller cross-sectional section than the intermediate portion. The height of the middle portion is 0.3 to 1.5 times the width or diameter of the middle portion.
The side surface of the lower end portion extends along the vertical direction throughout.
The intermediate portion has a steel plate extending in the horizontal direction at the lower end thereof.
In a plan view, the steel plate has a column base joint structure characterized by covering the lower end portion. The middle part has a prismatic shape and has a prismatic shape.
The column base joining structure according to claim 1 , wherein the tapered portion has a shape in which at least a part of a corner portion on the lower end side is cut out from a prism corresponding to the intermediate portion. In a building with multiple layers, it is a column base joint structure formed to avoid stress concentration on the lowest layer.
Reinforced concrete foundation structure and
It is provided with a first main bar erected on the foundation structure and connected to the foundation structure, and a reinforced concrete column having a second main bar not connected to the foundation structure.
The pillar has an intermediate portion extending in a vertical direction with a constant cross-sectional contour, and a lower end portion extending downward from the intermediate portion and having a smaller cross-sectional section than the intermediate portion. The height of the middle portion is 0.3 to 1.5 times the width or diameter of the middle portion.
The lower end portion has a tapered portion that tapers downward from the lower end portion of the intermediate portion.
The middle part has a prismatic shape and has a prismatic shape.
The tapered portion has a shape in which at least a part of the corner portion on the lower end side is cut out from the prism corresponding to the intermediate portion.
The first main bar is arranged inside the contour line of the lower end of the lower end portion in a plan view.
A column base joint structure characterized in that at least a part of the second main bar is arranged outside the contour line at the lower end of the lower end portion in a plan view.

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