JP2014058820A - Composite column structure and construction method for composite column - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a sectional area of a column while securing fire-resistance performance and effectively preventing generation of a crack.SOLUTION: A composite column 1 comprises: a column central portion 2 which is made of high-strength concrete having a predetermined water cementitious material ratio as well as predetermined strength and is arranged in a central portion of a column section; and a column peripheral portion 3 which is made of concrete having lower water cementitious material ratio as well as strength than the high-strength concrete and is arranged at a peripheral portion of the column section in a manner that covers whole side faces of the column central portion 2. In the composite column 1, column main reinforcement 4 is arranged only in the column peripheral portion 3.

Description

  The present invention relates to a composite column structure and a method for constructing a composite column using different-strength concrete in which the central portion of the cross section is made of high-strength concrete and the outer peripheral portion of the cross-section is made of relatively low strength concrete.

  In recent years, research and development on increasing the strength of concrete has been actively conducted, and concrete strength has been dramatically increased by reducing the water cement ratio with high-performance AE water reducing agents and reducing the water binder ratio by blending various admixtures. It has become. The strength of high-strength concrete generally depends on the type of cement and admixture, but generally increases as the water binder ratio decreases. Such high strength of concrete makes it possible to increase the height of buildings and reduce the cross section of columns, and is now widely used in high-rise buildings.

  On the other hand, it has been pointed out that the surface of high-strength concrete tends to explode in the event of a fire due to the dense structure. The mechanism of the explosion is not necessarily clear, but the increase in thermal stress and the increase in water vapor pressure due to fire are thought to be the main cause of the explosion. Therefore, when using high-strength concrete for the building frame, cover the surface of the frame with fireproofing to mitigate thermal stress during a fire, or mix synthetic fibers into the concrete to mitigate water vapor pressure during a fire. It is necessary to take measures such as.

  Although not considering such fireproof performance, precast concrete members that use high-strength concrete for the core of the frame and the surface of the frame made of materials other than high-strength concrete constitute the core of the frame A composite reinforced concrete structure has been proposed in which the main bars are arranged outside the main frame and the outer part of the frame is constructed by cast-in-place concrete so as to cover the main bars and the precast concrete members (see Patent Document 1). In this composite reinforced concrete structure, in addition to using high-strength concrete for the precast concrete member of the core part, the main reinforcement made of high-strength rebar is placed on the precast concrete member to further increase the strength of ordinary reinforced concrete structures. Yes.

  Similarly, refractory performance is not considered, but as an example of adopting a similar structure to reduce the cross-sectional area of the column, a reinforced concrete column for high axial force in which a precast high-strength concrete core is placed inside the reinforced concrete column Has been proposed (see Patent Document 2). In this reinforced concrete column, the tensile stress is mitigated by arranging a PC cable and a PC steel bar on a precast high-strength concrete core material.

JP 58-199957 A JP 61-49051 A

  By the way, in high-strength concrete, as the strength increases, the elastic strain, creep strain, and drying shrinkage strain tend to decrease, while the self-shrinkage strain tends to increase. Therefore, high-strength concrete is more likely to crack when compared with normal concrete when self-shrinkage is restricted. That is, as in Patent Documents 1 and 2, when main bars and PC steel materials extending in the material axis direction are arranged in the core portion of the frame made of high-strength concrete, these cause self-shrinkage in the material axis direction of the high-strength concrete. It will be restrained and it will become easy to generate | occur | produce a crack.

  The present invention has been made in view of such a background, and provides a column structure that can reduce the cross-sectional area of a column and that can effectively prevent the occurrence of cracks while ensuring fire resistance and a method for constructing the column structure. Is the purpose.

  In order to solve the above-described problem, according to one aspect of the present invention, a column center portion (2) made of high-strength concrete having a relatively high water binder ratio and disposed at a center portion of a cross section of the column, A column outer peripheral portion (3) made of a relatively low strength concrete having a lower water binder ratio than that of high strength concrete and arranged on the outer peripheral portion of the cross section of the column so as to cover the entire side surface of the central portion of the column. It is a composite pillar (1), Comprising: It is set as the structure by which the column main reinforcement (4) is arrange | positioned only at the said column outer peripheral part. Here, the high-strength concrete is concrete that realizes high strength by having a relatively high water binder ratio, and does not include concrete that realizes high strength by mixing substances other than the binder.

  By setting it as the composite pillar of such a structure, the cross-sectional area of a pillar can be made small, and the fire resistance performance of a pillar can also be ensured. In addition, since the central part of the column is not constrained by the column main reinforcement, the high-strength concrete can be freely self-contracted, and cracks due to self-contraction can be prevented from occurring in the central part of the column.

  Moreover, according to one side of this invention, it can be set as the structure which is the precast concrete in which the said pillar center part (2) has the length (L2) for two layers.

  According to this configuration, the number of products in the central part of the pillar can be reduced, and labor and time required for transportation and installation of the central part of the pillar can be reduced.

  Moreover, according to one side of this invention, it can be set as the structure by which the said column center part and the said column outer peripheral part are integrally connected by the cotter type joint (8) provided in the joint part (2A). .

  According to this configuration, the load transmitted from the beam to the column outer peripheral portion can be reliably transmitted to the column central portion, and the compressive strength of the composite column can be effectively increased.

  Moreover, in order to solve the said subject, according to 1 side surface of this invention, it is a construction method of a composite pillar (1), Comprising: High strength concrete with a comparatively high water binder ratio is laid, and pillar main reinforcement ( 4) the step of constructing the column central portion (2) disposed in the central portion of the cross section of the column where the column is not disposed, the column main reinforcement (4) disposed in the vicinity of the outer peripheral edge of the column, and the belt reinforcing bar surrounding the column main reinforcement ( A step of assembling the reinforcing bar including 5), placing relatively low-strength concrete having a lower water-binding material ratio than that of the high-strength concrete, arranged over the entire circumference of the cross-sectional outer periphery of the column, and And a step of constructing a column outer peripheral portion (3) for embedding the band rebar.

  By constructing the composite column in such a procedure, the cross-sectional area of the column can be reduced, and the fire resistance performance of the column can be ensured. In addition, since the central part of the column is not constrained by the column main reinforcement, the high-strength concrete can be freely self-contracted, and cracks due to self-contraction can be prevented from occurring in the central part of the column.

  Also, according to one aspect of the present invention, the building is a multi-layer building (10), and the step of constructing the column central portion (2) includes the step of manufacturing the column central portion with precast concrete, Placing the manufactured column center in the center of the cross section, repeating the steps of building the column center, placing the reinforcing bar, and building the column outer periphery, It can be set as the structure which construct | assembles the said composite pillar in the several floor of the lower layer of the said multilayer building so that a part (2) may continue over several floors.

  According to this method, since the center part of the column can be manufactured at a factory or the like, quality control of high-strength concrete can be facilitated. In addition, because high strength concrete is limited in terms of supply area and supply time, its use itself may be difficult depending on the location and process of the multi-layer building. The problem can be solved.

  In addition, according to one aspect of the present invention, the column central portion can be manufactured to a length (L2) corresponding to two layers.

  According to this method, the number of products in the central part of the pillar can be reduced, and labor and time required for transportation and installation of the central part of the pillar can be reduced.

  Further, according to one aspect of the present invention, in the step of manufacturing the column central portion, the intermediate strip reinforcing bar (6) is disposed so as to protrude from the side surface of the column central portion (2), and the column central portion is In the arranging step, the middle strip reinforcing bar arranged at the upper portion is locked to lift the central portion of the column, and the lower middle column reinforcing bar (4) is engaged with the middle belt reinforcing rod arranged at the lower portion. It can be set as the structure which positions the said column center part.

  The main cause of cracks at the center of the column is that self-shrinkage in the direction of the material axis is constrained. Therefore, by placing the intermediate strip reinforcing bar extending in the direction perpendicular to the material axis in the center of the column, it is possible to lift and position the central portion of the column using the intermediate strip without causing cracks. Thus, the construction can be facilitated, or the installation of a dedicated hanging jig or positioning jig can be omitted.

  Thus, according to the present invention, it is possible to provide a composite column structure and a method for constructing a composite column that can reduce the cross-sectional area of the column, as well as ensure fire resistance and effectively prevent the occurrence of cracks.

Sectional view of the composite pillar according to the present invention Cross-sectional view of a composite column according to a modification Side view of the column center shown in FIG. Side view of the central part of the column according to the modified example of the composite column shown in FIG. The side view of the column center part which concerns on the other modification of the composite column shown in FIG. Explanatory drawing of the conveyance state of the column center shown in FIG. The side view which concerns on the modification of the pillar center part shown in FIG. Sectional drawing of the compound pillar concerning other modifications Schematic side view of a multi-story building under construction applying the composite pillar according to the present invention The schematic diagram which shows the transmission path of the long-term load in the composite pillar concerning this invention The schematic diagram which shows the compression strut at the time of the earthquake load in the composite pillar based on this invention Schematic side view of a multi-story building under construction applying a composite pillar according to a modification Explanatory drawing of the construction method of the composite pillar concerning the present invention

  Hereinafter, embodiments of a composite column structure according to the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the composite column 1 has a rectangular central portion 2 having a rectangular cross section disposed in the central portion of the cross section, and a rectangular outer edge disposed on the outer peripheral portion of the cross section so as to cover the entire side surface of the central portion 2 of the column. Column outer peripheral part 3. The column central portion 2 is made of high-strength concrete having a relatively high water binder ratio and strength, and is substantially an unreinforced concrete structure. On the other hand, the column outer peripheral portion 3 is a reinforced concrete structure made of concrete (hereinafter referred to as ordinary concrete) having a lower water binding material ratio and strength than the column central portion 2. Here, high-strength concrete means concrete having a higher water binder ratio and strength than ordinary concrete, and does not define the lower limit values of the water binder ratio and strength. Either the high-strength concrete composing the column central portion 2 or the ordinary concrete composing the column outer peripheral portion 3 may be placed first, but it is united by adhesion of the concrete to be placed later. Yes.

The column outer peripheral portion 3 is arranged in the vicinity of the outer peripheral edge of the composite column 1 and has a plurality of (in this case, 24) column main bars 4 extending in the material axis direction and a material shaft so as to surround the plurality of column main bars 4. A plurality of rectangular strip reinforcing bars 5 (shear reinforcement bars) arranged at predetermined intervals in the direction are embedded. That is, the column main reinforcing bars 4 and the band reinforcing bars 5 are arranged only on the column outer peripheral portion 3. The column outer peripheral portion 3 has a thickness capable of securing predetermined cover thicknesses t ₁ and t ₂ on the inside and outside of the column main reinforcing bars 4 and the band reinforcing bars 5.

  As described above, the composite column 1 has a form in which high-strength concrete is not used because the high-strength concrete is used in a part of the cross section (the entire cross-section is configured by ordinary concrete constituting the column outer peripheral portion 3). Compared to the embodiment), the compressive strength can be increased, and the column cross-sectional area necessary for obtaining the same compressive strength can be reduced. In addition, since the column central portion 2 made of high-strength concrete is covered with the column outer peripheral portion 3, the surface portion of the composite column 1 is less likely to explode during a fire, and the fire resistance performance of the composite column 1 is ensured. .

  Furthermore, since the high-strength concrete in the column central portion 2 is not restrained by the column main reinforcing bars 4, it can be freely self-shrinkable and can be prevented from cracking. In addition, the column center part 2 does not need to be perfect unreinforced concrete, and the unreinforced concrete said here does not include the column main reinforcement 4 which restrains the self-shrinkage of the material axis direction of high-strength concrete, and PC steel materials. This means that a reinforcing bar that is embedded in an intermediate band reinforcing bar 6 that will be described later extending in the cross-sectional direction, or a reinforcing bar that is not considered in the structural calculation, such as a set-up reinforcing bar, is extended in the material axis direction. It is not excluded that it is embedded.

  From the viewpoint of preventing cracks, the composite pillar 1 is preferably as follows. That is, when the high-strength concrete of the column central portion 2 is placed inside after placing the normal concrete of the column outer peripheral portion 3 first, the adhesion of the high-strength concrete to the column outer peripheral portion 3 is a material of the high-strength concrete. In order not to restrain the self-shrinkage in the axial direction, the inner surface of the column outer peripheral portion 3, that is, the joint surface between the column outer peripheral portion 3 and the column central portion 2 may be made flat in the material axis direction.

  On the other hand, when high-strength concrete in the column central portion 2 is first placed and then normal concrete in the column outer peripheral portion 3 is placed on the outside thereof, the ordinary concrete in the column outer peripheral portion 3 attached to the column central portion 2 is placed in the center of the column. In order not to constrain the self-shrinkage of the high-strength concrete in the part 2, in addition to flattening the joint surface with the column outer peripheral part 3 in the material axis direction, the column outer-periphery part 3 after the self-shrinkage of the high-strength concrete has progressed to some extent It is recommended to cast ordinary concrete.

  In the case where high-strength concrete is placed first, the column central portion 2 may be manufactured in advance at a factory or the like as a precast concrete product. If it does in this way, quality control of high-strength concrete whose quality control is complicated compared with ordinary concrete can be made easy. Moreover, even when the ordinary concrete of the column outer peripheral portion 3 is made on-site, the self-shrinkage of the high-strength concrete can be advanced to a considerable extent without causing a waiting time at the time of on-site construction. On the other hand, it is of course possible to place ordinary concrete on the outer periphery 3 of the column at a factory or the like so that the entire composite column 1 is a precast concrete product.

  On the other hand, even when the ordinary concrete of the column outer peripheral portion 3 is previously placed, both concrete may be pre-fabricated as precast concrete at a factory or the like. In addition, when the normal concrete of the column outer peripheral portion 3 is first placed, only the column outer peripheral portion 3 on which the concrete is first placed may be prefabricated as precast concrete in a factory or the like.

  When high-strength concrete in the center 2 of the column is first placed in a factory or the like, and the ordinary concrete in the outer periphery 3 of the column to be placed later is cast in the field, 2 precast concrete products in the center 2 of the column are further added. It is preferable to have a length L2 (see FIG. 12) for a layer. Since the cross-section of the column central portion 2 is relatively small, the number of products in the column central portion 2 can be reduced by making it possible to carry and lift with a normal transport vehicle or lifting equipment. Therefore, the cost, labor, and time required for transportation and installation of the column central portion 2 are reduced.

  With reference to FIG. 2 and FIG. 3, the modification of the composite pillar 1 shown in FIG. 1 is demonstrated. In addition, the same code | symbol is attached | subjected to the element which overlaps with the said embodiment, and the overlapping description is abbreviate | omitted. The same applies to the following modified examples of the composite column structure and modified examples of the composite column construction method.

  As shown in FIG. 2, this composite column 1 has a rectangular intermediate strip reinforcing bar 6 (shear reinforcement) surrounding only a part of the column main reinforcing bars 4 in addition to the band reinforcing rods 5 surrounding all the column main reinforcing bars 4. doing. The intermediate strip reinforcing bars 6 are arranged so as to extend on a plane orthogonal to the material axis and to protrude from a pair of opposite side surfaces of the column central portion 2 through the column central portion 2 in one direction.

  When constructing this composite column 1, it is preferable that at least the column central portion 2 is manufactured in advance as a precast concrete in a factory or the like, and the ordinary concrete of the column outer peripheral portion 3 is cast later. By doing in this way, even if the reinforcing bar which protrudes from the pillar center part 2 is arrange | positioned, high-strength concrete can be self-shrink freely in a material axial direction. In addition, after placing the high-strength concrete in the central part 2 of the column, in order to avoid that the intermediate strip rebar 6 is restrained by the formwork, it is necessary to remove the mold immediately after the desired strength is developed. preferable.

  As shown in FIG. 3, the column center portion 2 is a precast concrete product having a length L1 (see also FIG. 9) for one layer here. The upper end of the column central portion 2 constitutes a joint portion 2A that is a connection portion between the composite column 1 and the beam 11, and the main beam 13 (see FIG. 9) is inserted into the joint portion 2A. Through-holes 7 are formed, and concave portions 9 constituting the cotter joint 8 are formed on each side surface (four surfaces here) to which the beam 11 is joined. That is, the column outer peripheral portion 3 indicated by an imaginary line is integrally coupled to the column central portion 2 by the cotter type joint 8. The intermediate rebar 6 extends in the vertical direction at the same pitch as the rebar 5 (FIG. 2) to the portion excluding the portion through which the beam main rebar 13 of the joint 2A passes and the column main portion 2B below the joint 2A. A plurality are arranged in one row.

  Even if the composite pillar 1 is configured in this way, the same effect as that of the composite pillar 1 shown in FIG. 1 can be obtained. Moreover, handling of the column center part 2 which is a precast concrete product can be made easy. In other words, when transporting the column central part 2, the pair of upper and lower intermediate strip reinforcing bars 6 protruding from one side can be locked to lift the column central part 2, and when the column central part 2 is installed on the site, it is arranged at the upper part. The center part 2 of the column can be lifted by locking both ends (parts protruding from the opposing side surfaces) of the intermediate band reinforcing bar 6 formed, and the column main reinforcing bar 4 on the lower floor is connected to the intermediate band reinforcing bar 6 arranged at the lower part. Can be engaged to position the column central portion 2.

  Or you may comprise the compound pillar 1 shown in FIG. 2 as shown in FIG.4 and FIG.5. In the composite column 1 shown in FIG. 4, the intermediate strip rebar 6 is disposed in an appropriate quantity (three in this case) in a portion excluding the portion through which the beam main reinforcing bar 13 of the joint portion 2A passes, and the column main portion 2B. An appropriate quantity (here, one) is arranged at the bottom. Even if the composite pillar 1 is configured in this way, the same effect as that of the composite pillar 1 shown in FIG. 3 can be obtained.

  In the composite pillar 1 shown in FIG. 5, the intermediate strip reinforcing bars 6 are arranged at three places, the uppermost part of the column main part 2B, the lower center of the column main part 2B, and the lowermost part of the column main part 2B. Even if the composite pillar 1 is configured in this way, the same effects as those of the composite pillar 1 shown in FIGS. 3 and 4 can be obtained. That is, when the column central part 2 is transported, as shown by the solid line in FIG. 6, the upper two intermediate strip reinforcing bars 6 protruding from one side surface are locked by the hanging metal fitting 15 to lift the column central part 2. As shown in phantom lines in FIG. 6, both ends of the intermediate strip rebar 6 arranged at the uppermost portion (portions protruding from the opposite side surfaces) are attached to the suspension bracket 15 when the column central portion 2 is installed in the field. The column central portion 2 can be lifted by being locked, and the column central portion 2 can be positioned by engaging the column main reinforcing bars 4 on the lower floor with the intermediate strip reinforcing bars 6 arranged at the lowermost part.

  3 to 5 show a form in which the through-hole 7 for inserting the beam main reinforcing bar 13 is formed in the column central portion 2 so that the beam main reinforcing bar 13 can be arranged. As shown in FIG. It is good also as a form which arrange | positions the insertion beam main reinforcement 14 of suitable length before placing concrete, and inserts it in the column center part 2. FIG.

  With reference to FIG. 8, another modification of the composite pillar 1 shown in FIG. 1 will be described. This composite column 1 has rectangular intermediate strip reinforcing bars 6 surrounding only some column main reinforcing bars 4 in two directions perpendicular to each other, in addition to the reinforcing bars 5 surrounding all the column main reinforcing bars 4. Each of the intermediate strip reinforcing bars 6 is arranged so as to extend on a plane orthogonal to the material axis and to protrude from a pair of side surfaces of the column central portion 2 facing each other through the column central portion 2 in one direction. .

  The arrangement of both intermediate strip reinforcing bars 6 in the material axis direction may be any one of the forms shown in FIGS. 3 to 5, or other forms. When providing the intermediate band reinforcing bar 6 at the same pitch as the band reinforcing bar 5 as shown in FIG. 3, both the intermediate band reinforcing bars 6 may be arranged at the pitch of the band reinforcing bar 5, and other pitches, for example, both intermediate band reinforcing bars The pitch of 6 may be twice that of the band reinforcing bar 5, and the intermediate band reinforcing bars 6 in each direction may be alternately arranged, or both the intermediate band reinforcing bars 6 may be arranged at the same position.

  Next, the construction procedure of the composite pillar 1 according to the present invention will be described.

  First, one construction procedure of the composite pillar 1 applied to the multi-layer building 10 will be described with reference to FIG. In this example, the column central portion 2 is a precast concrete product having a length L1 (the height from the upper surface of the beam 11 on the lower floor to the upper surface of the beam 11 on the lower floor) for one layer, and the ordinary concrete on the outer periphery 3 of the column. Is on-site.

  First, the column center part 2 as shown in FIGS. 2-8 is manufactured in a precast factory. In other words, the intermediate strip rebar 6 is arranged so as to protrude from the side surface of the formwork of the column central part 2 and the strength of the water binder is relatively high in the formwork of the pillar center part 2 without the main reinforcement being arranged. Concrete is placed, and the formwork is quickly disassembled after waiting for the expression of a predetermined concrete strength so as not to restrain the self-shrinkage of the column central portion 2 in the direction of the material axis. The concave portion 9 constituting the cotter type joint 8 is disposed in the vicinity of the upper end of the column central portion 2, but considering that the mold convex portion forming the concave portion 9 restrains the initial self-shrinkage of the column central portion 2. Then, it is good to lay high-strength concrete in the state where the formwork is turned upside down (the state where the concave portion 9 is located near the lower end).

  Next, the manufactured column central part 2 is carried into the site and arranged in the central part of the cross section of the composite column 1. At this time, as described with reference to FIG. 6, the middle strip rebar 6 disposed at the upper portion is locked to lift the column central portion 2, and the lower floor is disposed on the middle strip rebar 6 disposed at the lower portion. The column central portion 2 may be positioned by engaging the column main reinforcing bars 4 extending from the center. In addition, it is good to lay high intensity | strength non-shrink mortar etc. in the surface which mounts the column center part 2. FIG. The column central portion 2 is fixed by fixing the positions of the column main reinforcement 4 and the column mold frame. Until such fixing, the column central portion 2 is fixed by appropriate temporary fixing means such as joining of the beam main reinforcement 13 described later. 2 is temporarily fixed.

Thereafter, the reinforcing bars including the column main reinforcing bars 4 and the band reinforcing bars 5 surrounding the column main reinforcing bars 4 are arranged on the outer periphery of the column central portion 2 and the beam reinforcing bars 12 are assembled, and the composite columns 1 and the formwork (not shown) of the beams 11 are assembled. When the insertion beam main reinforcement 14 having an appropriate length is inserted into the column central portion 2, the beam main reinforcement 13 is joined to the insertion beam main reinforcement 14 through joint means. On the other hand, when the through hole 7 for inserting the beam main reinforcement 13 is provided in the column central portion 2, grout is injected into the through hole 7 in a state where the beam main reinforcement 13 is inserted into the through hole 7. Join the column center 2. The column form frame is provided with a support to prevent tilting, and the cover thicknesses t ₁ and t ₂ between the column form frame and the band reinforcing bar 5 and between the column main reinforcement 4 and the outer side surface of the column central portion ₂ (see FIG. The column central part 2 is fixed by installing a spacer (not shown) for securing 1), and the column central part 2 is prevented from falling when the high-strength concrete is placed.

  Then, ordinary concrete having a lower water binder ratio and strength than that of the column central portion 2 is placed in the formwork, and the column main reinforcement 4 and the belt reinforcing bar 5 are embedded with the ordinary concrete, and the entire side surface of the column central portion 2 is covered. The column outer peripheral portion 3 and the beam 11 are constructed so as to cover them. In addition, it is good to place concrete also about a slab with the beam 11 simultaneously. Thereafter, the formwork is removed, and the above procedure is repeated for the upper floors, and the composite pillar 1 is constructed on at least a plurality of lower floors of the multi-layer building 10 so that the column central portion 2 is continuous over a plurality of floors.

  The load burden on the composite column 1 in which the column central portion 2 is constructed of high-strength concrete having no main reinforcement and the column outer peripheral portion 3 is constructed of relatively low-strength ordinary concrete having the column main reinforcement 4 is shown in FIG. This will be described with reference to FIG.

As shown in FIG. 10, in addition to the load N transmitted from above, the loads Q _R1 , Q _{L1 to} Q _R3 , Q _L3 of the beams 11 transmitted to the column outer peripheral portion 3 are cotters in addition to the load N transmitted from above. It transmits to the column center part 2 through the type | mold coupling 8. FIG. Therefore, the load becomes larger in the lower floor, and the load is N + Σ (Q ₁ + Q ₂ + Q ₃ ) in the lowest floor of the illustrated composite column 1 to which the load N is applied from above. Since the column central portion 2 has a compressive strength greater than that of the column outer peripheral portion 3, the elastic strain and creep strain are small, and the load per unit area is larger than the load per unit area of the column outer peripheral portion 3. That is, the long-term load is mainly borne by the high-strength column central portion 2.

  On the other hand, during an earthquake load, as shown in FIG. 11, an axial force is applied to the composite column 1, and the compression struts 16 have different left and right ends at the stigma (lower end of the joint) and the column base (upper end of the joint). To go through. That is, at the column head and the column base where the bending moment increases, the column outer peripheral portion 3 on the low strength side becomes a bending compression region, and the compressive load at the time of earthquake is mainly borne by the column outer peripheral portion 3.

  As described above, the column central portion 2 made of high-strength concrete is constructed in the central portion of the cross section where the main reinforcement is not arranged, and the column main reinforcement 4 and the like are arranged on the outer periphery of the column central portion 2 and then combined with water compared to the column central portion 2. By constructing the composite column 1 by constructing the column outer peripheral portion 3 made of ordinary concrete having a low material ratio and strength, the cross-sectional area of the column corresponding to a predetermined long-term load and seismic load can be reduced. The fire resistance performance can be ensured. Further, since the column central portion 2 is not constrained by the column main reinforcing bars 4, the high-strength concrete can freely self-shrink and the column central portion 2 does not crack.

  As described above, high-strength concrete is concrete that achieves high strength by having a relatively high water binder ratio, and concrete that achieves high strength by mixing substances other than binder. Since it is not included, mixing and stirring of high-strength concrete and handling are not difficult, and the material cost is not increased unnecessarily.

  Moreover, in the said embodiment, the pillar center part 2 is made as the precast concrete manufactured in a factory etc., and this can make quality control of high-strength concrete easy, and also at the construction site, construction time, etc. of the multilayer building 10 Even if there is a restriction, it is possible to construct the column central portion 2 using high-strength concrete.

  Furthermore, in the above-described embodiment, the intermediate strip rebar 6 is arranged in the column central portion 2, and when the column central portion 2 is arranged as shown in FIG. When the center of the column 2 is positioned, cracks are generated in the center 2 of the column by engaging the lower main column 4 with the intermediate rebar 6 disposed in the lower part. Therefore, it is possible to facilitate the construction or to omit a dedicated hanging jig and positioning jig.

  As a modification of one construction procedure of the composite pillar 1 applied to the multi-layer building 10, as shown in FIG. 12, the pillar center portion 2 is constructed with a length L2 of two layers (from the upper surface of the beam 11 on the lower floor). Precast concrete product of two floors up to the upper surface of the beam 11 on the first floor above the floor to be constructed, and the composite pillar 1 is constructed by using ordinary concrete on the outer periphery of the pillar 3 on-site in each floor Also good. In such a construction method, each procedure may be performed in the same manner as the construction procedure described above, but after the construction of the column outer periphery 3 of the first layer, the columns of the second layer are not performed without the arrangement of the column central portion 2. The outer periphery 3 is constructed. Thus, the number of the precast concrete products which comprise the pillar center part 2 can be reduced by making the pillar center part 2 the precast concrete product of length L2 for two layers, and transportation and installation of the pillar center part 2 are possible. The labor and time required for the process can be reduced.

  Furthermore, as shown in FIG. 13, it can also be set as the form which builds the composite pillar 1 whole as a precast concrete product. In this case, as in the above procedure, in the precast factory, firstly, the intermediate strip rebar 6 is disposed so as to protrude from the side surface of the formwork of the column central portion 2, and high-strength concrete is placed without placing the main rebar. After the column central portion 2 is manufactured, subsequently, in the precast factory, as shown in FIG. 13 (A), the column main reinforcement 4 and the belt reinforcing bars 5 surrounding the column main reinforcement 4 are included on the outer periphery of the column central portion 2. Reinforcing bars are arranged, and a formwork of the column outer peripheral portion 3 (not shown) is assembled. A joint 4 a is attached to the lower end of the column main reinforcement 4, and the upper end of the column main reinforcement 4 protrudes above the upper surface of the column outer peripheral portion 3 so as to be connected to the joint 4 a of the column main reinforcement 4 on the upper floor. Thereafter, ordinary concrete having a lower water binder ratio and strength than the column central part 2 is placed in the formwork, and as shown in FIG. 13B, the entire side surface of the column central part 2 is the outer periphery of the column. The composite pillar 1 covered with 3 is manufactured. When the entire composite column 1 is a precast concrete product, a recess 17 is also formed on the side surface of the column outer peripheral portion 3 in order to join the composite column 1 and the beam 11 (FIGS. 9 to 12) with a cotter joint. To do.

  In this way, when the entire composite column 1 is precast concrete, the normal concrete of the column outer peripheral portion 3 has a small self-shrinkage, and the upper end of the column main reinforcement 4 protrudes upward. When placing concrete, as shown in FIG. 13 (B), it may be performed in a state in which the joint portion 2A is in the upward direction (direction in the installed state). On the other hand, when placing the high-strength concrete in the column central portion 2 shown in FIG. 13A, the concave portion 9 constituting the cotter joint 8 is in the vicinity of the lower end in order to avoid the self-shrinkage restriction as described above. It is good to carry out in the state (upside down state shown in the figure).

  After the produced composite pillar 1 is carried into the site, the pillar center part 2 is arranged so as to be continuous with the pillar center part 2 of the lower floor, and the column main reinforcement 4 is connected via a joint 4a provided at the lower end thereof. By being connected to the pillar main reinforcement 4 on the lower floor, it is constructed at a predetermined position.

  Even if the composite pillar 1 is constructed in this way, the cross-sectional area can be reduced and fire resistance can be ensured. Further, since the column central portion 2 is not constrained by the column main reinforcement 4, the high-strength concrete can be freely self-shrinked, and the occurrence of cracks in the column central portion 2 can be prevented.

  This is the end of the description of the specific embodiments. However, the present invention is not limited to these embodiments, and the specific shape of each element, the arrangement, the quantity, the order of work procedures, and the like are described in the present invention. Any change can be made without departing from the scope of the present invention. In addition, all the elements of the composite pillar 1 structure according to the present invention and the elements of the construction procedure of the composite pillar 1 according to the present invention shown in the above embodiment are not necessarily essential, and can be appropriately selected.

DESCRIPTION OF SYMBOLS 1 Composite pillar 2 Column center part 2A Joint part 3 Column outer periphery part 4 Column main reinforcement 5 Band reinforcement 6 Middle belt reinforcement 8 Cotter type joint 10 Multi-layer building

Claims (7)

A column central portion made of high-strength concrete having a predetermined water binder ratio and strength, and arranged in the central portion of the cross section of the column,
A column outer peripheral portion that is made of concrete having a low water binder ratio and strength compared to the high-strength concrete, and that is disposed in the outer peripheral portion of the cross section of the column so as to cover the entire side surface of the central portion of the column,
A column structure comprising a column main bar arranged only in the outer periphery of the column.   The composite column structure according to claim 1, wherein the column central portion is precast concrete having a length corresponding to two layers.   The composite column structure according to claim 1, wherein the column central portion and the column outer peripheral portion are integrally coupled by a cotter-type joint provided in a joint portion. A method for constructing a composite pillar,
Placing a high-strength concrete having a predetermined water binder ratio and strength, and constructing a column central portion disposed in a central portion of the cross section of the column where the column main reinforcement is not disposed;
Assembling a reinforcing bar including a column reinforcing bar arranged in the vicinity of the outer periphery of the column and a belt reinforcing bar surrounding the column reinforcing bar;
Placing a concrete having a lower water binder ratio and strength than the high-strength concrete, and constructing a column outer peripheral portion that is arranged over the entire outer periphery of the cross-section of the column and embeds the column main reinforcing bar and the strip reinforcement. A method of constructing a composite pillar characterized by including. The building is a multi-story building;
The step of building the column central portion includes the step of manufacturing the column central portion with precast concrete, and the step of arranging the manufactured column central portion in the cross-sectional central portion of the column,
The steps of constructing the pillar central portion, assembling the reinforcing bars, and constructing the outer periphery of the pillar are repeated, and the pillar central portion is continuous over a plurality of floors, so that the at least a plurality of lower floors of the multi-layered building The method for constructing a composite pillar according to claim 4, wherein the composite pillar is constructed.   6. The method for constructing a composite pillar according to claim 5, wherein the central part of the pillar is manufactured to a length corresponding to two layers. In the step of producing the column central portion, an intermediate strip reinforcing bar is disposed so as to protrude from the side surface of the column central portion,
In the step of disposing the central part of the column, the middle band reinforcing bar arranged at the upper part is locked to lift the central part of the column, and the lower part of the column main reinforcing bar is engaged with the intermediate belt reinforcing bar arranged at the lower part. The column structure according to claim 5 or 6, wherein the column central part is positioned.

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