Junction structure of prestressed concrete (PC) column and steel beam

Abstract

A structure enables free and reasonable designing of a cross section of an end of a steel beam in accordance with bending stress and a housed state of a PC steel, thereby providing an economic and reasonable building as a whole. A beam end block includes end plates and an anchor plate. The end plates are fixed at an end surface of an H-section steel in a direction substantially perpendicular to the longitudinal direction of the beam. The anchor plate is fixed to the H-section steel separately from the end plates, on a side opposite to a column, in a direction substantially perpendicular to the longitudinal direction of the beam. An end of the steel beam has an upper part and a lower part. The upper part protrudes toward the column more than the lower part and is mounted on a cogging. The beam end block has a height dimension larger than the height dimension of the H-section steel and has a lower end that is disposed at substantially the same height as a lower end of a side surface of the cogging facing the lower part of the end of the steel beam.

Claims

1. A column-beam junction structure composed of a prestressed concrete (PC) column and a steel beam that are integrally jointed to each other, the steel beam including an H-section steel as a beam main body and a beam end block that is provided at an end of the H-section steel, the steel beam being disposed in a state in which the end is mounted on a cogging provided to a side surface of the column, the beam end block including an end plate and an anchor plate, the end plate being fixed at an end surface of the H-section steel in a direction substantially perpendicular to a longitudinal direction of the steel beam, the anchor plate being fixed to the H-section steel separately from the end plate, on a side opposite to the column, in the direction substantially perpendicular to the longitudinal direction of the steel beam, the end of the H-section steel including an upper part and a lower part, the upper part protruding toward the column more than the lower part and being mounted on the cogging, the end plate including an outer end plate and an inner end plate, the outer end plate being fixed at an end surface of the upper part of the H-section steel and facing the side surface of the column via a first joint, the inner end plate being fixed at an end surface of the lower part of the H-section steel and facing the cogging via a second joint, the beam end block having a height dimension larger than a height dimension of the H-section steel, the beam end block having a lower end that is disposed at substantially the same height as a lower end of a side surface of the cogging facing the lower part, the column and the beam end block being penetrated by a PC tendon, the PC tendon being tensioned and anchored to a surface on a side opposite to the column of the anchor plate to perform the integral jointing, wherein a space between the end plate and the anchor plate is filled with a filler material.

2. The column-beam junction structure according to claim 1, wherein the filler material is at least one of mortar or concrete.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a sectional view illustrating an upper 1A-1A cross section and a lower 1A-1A cross section of a column-beam junction structure according to an embodiment of the present application in FIG. 1B; FIG. 1B is a sectional view illustrating an 1B-1B cross section of the column-beam junction structure according to the embodiment of the present application in FIG. 1A;

(2) FIG. 2A is a perspective view of a beam end of the column-beam junction structure according to the embodiment of the present application; FIG. 2B is a sectional view illustrating a 2B-2B cross section of the beam end of the column-beam junction structure according to the embodiment of the present application in FIG. 2C; FIG. 2C is a sectional view illustrating a 2C-2C cross section of the beam end of the column-beam junction structure according to the embodiment of the present application in FIG. 2B; and

(3) FIG. 3 is a sectional view illustrating a 3-3 cross section of the column-beam junction structure according to the embodiment of the present application in FIG. 1A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) A column-beam junction structure 1 according to an embodiment of the present application will be described with reference to FIG. 1A to FIG. 3. FIG. 1A is a sectional view illustrating cross sections of the column-beam junction structure 1 according to the embodiment of the present application, which are cut in a horizontal direction. The cross section on the left of the center line is an upper 1A-1A cross section illustrated in FIG. 1B. The cross section on the right of the center line is a lower 1A-1A cross section illustrated in FIG. 1B. The right-left direction is defined as a span direction, whereas the up-down direction is defined as a ridge direction, in FIG. 1A. FIG. 1B is a sectional view illustrating an 1B-1B cross section of the column-beam junction structure 1 according to the embodiment of the present application in FIG. 1A. Note that, for clearness of the drawings, hatching of cross sections, such as of a cross section of a column 2, is partially omitted in the cross sectional drawings of the present application.

(5) FIG. 1A illustrates an example using the column-beam junction structure 1 according to the embodiment to joint four steel beams and a concrete column 2 that is disposed as a middle column. The steel beam includes an H-section steel 3 and a beam end block 4. Each of the H-section steels 3 has an upper flange 3a, a web 3b, and a lower flange 3c. The H-section steel 3 has an end to which the beam end block 4 is fixed. The beam end block 4 is formed into a box shape from multiple plates. The beam end block 4 will be detailed later. The member for constituting a main part of the steel beam is not limited to an H-section steel and can use other section steel, such as an I-section steel.

(6) The steel beam is abutted and jointed to a side surface of the column 2, in a direction substantially perpendicular to the longitudinal direction of the column 2. The four steel beams and the column 2 are jointed by using similar column-beam junction structures 1. In consideration of this, corresponding parts of the four steel beams are denoted by the same reference signs in the drawings. The column-beam junction structures 1 in the span direction and in the ridge direction are partially different from each other, and these differences will be described later. The column-beam junction structure 1 of the present application is not limitedly used in a middle column and can be used in an outer column and a corner column.

(7) The column 2 is made of concrete and can be made of, for example, prestressed concrete or reinforced concrete. The column 2 may be formed of precast concrete or cast-in-place concrete. In short, the column 2 and the steel beam are jointed to each other after they are formed separately. The column 2 has a corbel or cogging 2a that is projected or overhangs from a side surface and that is used for mounting a beam end thereon. The cogging 2a can be integrally formed with the column 2 by using concrete. The cogging 2a has an upper surface, three side surfaces, and a tapered lower surface. The upper surface is substantially perpendicular to the longitudinal direction of the column 2. The side surfaces are substantially parallel to the longitudinal direction of the column 2. The lower surface is sloped in such a manner that a protrusion from the side surface of the column 2 is decreased in dimension as it goes downward. The lower surface of the cogging 2a is tapered in order to facilitate removal of forms or molds in manufacturing the column 2. The cogging 2a preferably has the above-described shape, but the shape is not limited to this and can be any shape that is configured to be mounted with a beam end. For example, the lower surface may be a horizontal surface.

(8) A joint is provided between the beam end block 4 and the column 2, and a joint mortar 5 is interposed therebetween. Providing the joint in this manner prevents problems due to dimension errors and facilitates building.

(9) The steel beam is tensioned and anchored to the column 2 by PC tendons 6 and anchoring devices or fasteners 7. The PC tendons 6 are arranged in such a manner as to penetrate the beam end blocks 4 and the column 2. The anchoring devices 7 are respectively disposed to both sides of the PC tendon 6. The PC tendon 6 can use a PC steel, such as a PC steel bar. In a case of using a PC steel bar, the anchoring device 7 includes a bearing plate and a nut. The anchoring device 7 tensions and anchors the PC tendon 6, in a state of being in contact with a surface of the beam end block 4 on a side opposite to the column 2. The tensioning force of the PC tendon 6 is transmitted to the beam end block 4 via the anchoring device 7, and a binding force of the PC tendon 6 is introduced to the jointed surface between the column 2 and the beam end block 4 to joint them. In a case in which the column 2 is an outer column or a corner column, an anchoring device 7 on a side on which a steel beam is not disposed, tensions and anchors a PC tendon 6, in a state of being in contact with a side surface of the column 2.

(10) A PC tendon 6 and a pair of anchoring devices 7 constitute one set, and three sets are arranged on each side of the web 3b. As illustrated in FIG. 1B, in the column-beam junction structure 1 of the column 2 and the steel beams extending in the span direction, among three sets, each constituted of the PC tendon 6 and the pair of the anchoring devices 7, arranged on one side of the web 3b, one set is disposed at a position where the PC tendon 6 penetrates the cogging 2a, and two sets are disposed at positions where the PC tendons 6 penetrate portions of the column 2 above the cogging 2a.

(11) FIG. 2A is a perspective view of a beam end of the column-beam junction structure 1 according to the embodiment of the present application. FIG. 2B is a sectional view of the beam end of the column-beam junction structure 1 according to the embodiment of the present application, which is cut in the horizontal direction, and FIG. 2B illustrates a 2B-2B cross section in FIG. 2C. FIG. 2C is a sectional view of the beam end of the column-beam junction structure 1 according to the embodiment of the present application, which is cut in the gravitational direction, and FIG. 2C illustrates a 2C-2C cross section in FIG. 2B.

(12) As illustrated in FIG. 2C, in the end of the steel beam, an upper part protrudes toward the column 2 more than a lower part. That is, the upper part of the H-section steel 3 and the upper part of the beam end block 4 protrude toward the column 2 more than the respective lower parts. As illustrated in FIG. 1B, the upper part of the steel beam protruding toward the column 2 is mounted on the cogging 2a.

(13) The beam end block 4 has an outer end plate 4a, a bed plate 4b, an inner end plate 4c, a bottom plate 4d, an anchor plate 4e, and a pair of side plates 4f.

(14) The outer end plate 4a is made of a rectangular steel sheet and is disposed in a direction substantially perpendicular to the longitudinal direction of the H-section steel 3, in a state of being in contact with an upper end surface of the H-section steel 3 protruding toward the column 2. The outer end plate 4a is fixed to the upper end surface of the H-section steel 3 protruding toward the column 2, the bed plate 4b, and the side plates 4f. The outer end plate 4a has a dimension larger than a flange width of the H-section steel 3 in the flange width direction of the H-section steel 3. The outer end plate 4a preferably has a height dimension slightly larger than that of the upper part of the H-section steel 3 protruding toward the column 2, in order to facilitate welding.

(15) The bed plate 4b is made of a rectangular steel sheet and is substantially horizontally disposed in contact with a lower end of the web 3b of the upper part of the H-section steel 3 protruding toward the column 2. The bed plate 4b is disposed at a position substantially the same height as a lower end of the outer end plate 4a. The bed plate 4b is fixed to the H-section steel 3, the outer end plate 4a, the side plates 4f, and the inner end plate 4c. The bed plate 4b has substantially the same dimension as the outer end plate 4a in the flange width direction of the H-section steel 3. The bed plate 4b has substantially the same dimension as the upper part of the H-section steel 3 protruding toward the column 2, in the longitudinal direction of the H-section steel 3.

(16) The inner end plate 4c is made of a rectangular steel sheet and is disposed in a direction substantially perpendicular to the longitudinal direction of the H-section steel 3, in contact with a lower end surface of the H-section steel 3, under the web 3b protruding toward the column 2 at the end of the steel beam. The inner end plate 4c is fixed to the bed plate 4b, the lower end surface of the H-section steel 3, the bottom plate 4d, and the side plates 4f. The inner end plate 4c has substantially the same dimension as the outer end plate 4a in the flange width direction of the H-section steel 3. The inner end plate 4c has a height dimension larger than the length from a lower end of the upper part of the H-section steel 3 protruding toward the column 2 to the lower end of the H-section steel 3 and extends downwardly beyond the lower flange 3c.

(17) The bottom plate 4d is made of a rectangular steel sheet and is disposed under an end of the lower flange 3c. The bottom plate 4d horizontally extends at substantially the same height as a lower end of the inner end plate 4c. The bottom plate 4d is fixed to the inner end plate 4c, the anchor plate 4e, and the side plates 4f. The bottom plate 4d has substantially the same dimension as the outer end plate 4a in the flange width direction of the H-section steel 3.

(18) The anchor plate 4e is formed of a steel sheet and is disposed separately from the end plates 4a and 4c on a side opposite to the column 2, in a direction substantially perpendicular to the longitudinal direction of the H-section steel 3. The H-section steel 3 penetrates the anchor plate 4e. The anchor plate 4e may be formed as separate bodies, and the separate bodies may be disposed at predetermined positions and are integrally joined at both sides of the web 3b, respectively. The distance between the anchor plate 4e and each of the end plates 4a and 4c is determined in accordance with rigidity required for joining the steel beam and the column 2. The anchor plate 4e is fixed to the H-section steel 3, the bottom plate 4d, and the side plates 4f. The anchor plate 4e extends downwardly beyond the lower flange 3c from a lower surface of the upper flange 3a. A lower end of the anchor plate 4e is disposed at substantially the same height as the lower end of the inner end plate 4c.

(19) Each of the paired side plates 4f is formed of a steel sheet and is disposed substantially parallel to the web 3b in the vicinity of an end of the outer end plate 4a, in the flange width direction of the H-section steel 3. The side plate 4f is fixed to the outer end plate 4a, the bed plate 4b, the inner end plate 4c, the bottom plate 4d, and the anchor plate 4e. An upper part of the side plate 4f has a shape protruding toward the column 2 in conformity with the end shape of the H-section steel 3.

(20) As illustrated in FIG. 1B, a space between the end plates 4a and 4c and the anchor plate 4e, that is, a space inside the beam end block 4, can be filled with a filler material 8. This improves rigidity of the beam end block 4. The beam end block 4 opens upward, and therefore, it is easy to fill it with the filler material 8. The filler material 8 can use, for example, shrinkage-compensating or no-contraction mortar or concrete. Filling with the filler material 8 can be performed in a factory or in a construction site. Filling with the filler material 8 in a construction site enables reduction in weight of a steel beam in transporting the steel beam from a factory to the construction site. In a case in which the beam end block 4 has sufficiently high rigidity, filling with the filler material 8 is not necessary.

(21) As illustrated in FIG. 1B, the height dimension of the beam end block 4 is larger than that of the H-section steel 3. A lower end of the beam end block 4 is disposed at substantially the same height as a lower end of a side surface of the cogging 2a that faces a lower part of the beam end block 4 or of the steel beam.

(22) Next, the column-beam junction structure 1 of the column 2 and a steel beam extending in the ridge direction will be described with reference to FIG. 3. FIG. 3 is a sectional view illustrating a 3-3 cross section of the column-beam junction structure 1 according to the embodiment of the present application in FIG. 1A. The column-beam junction structure 1 in the ridge direction has much in common with the column-beam junction structure 1 in the span direction. For this reason, the common parts are denoted by the same reference signs as those used in the column-beam junction structure 1 in the span direction, and duplicated description is omitted.

(23) The H-section steel 3 of the steel beam extending in the ridge direction has a height dimension smaller than the height dimension of the H-section steel 3 of the steel beam extending in the span direction. The column-beam junction structure 1 in the ridge direction differs from the column-beam junction structure 1 in the span direction in that two PC tendons 6 penetrate the cogging 2a and one PC tendon 6 penetrates a part of the column 2 above the cogging 2a. In accordance with this structure, the cogging 2a is larger in the height direction than in the span direction. In addition, a part of the beam end block 4 that protrudes downwardly from the lower flange 3c is larger in the height direction than in the span direction. Three sets, each constituted of the PC tendon 6 and the pair of the anchoring devices 7, are arranged in the vertical direction, and all of the three sets are arranged between the upper flange 3a and the lower flange 3c in the vertical direction, in the span direction. On the other hand, the lowermost set of the PC tendon 6 and the pair of the anchoring devices 7 is disposed at a position lower than the lower flange 3c in the ridge direction.

(24) The embodiment described above enables determining a cross section of a member of each of an intermediate part and the beam end block 4 of the steel beam. It is possible to constitute the beam main body or the intermediate part by using a conventional H-section steel 3 and to freely set the height dimension of the beam end block 4 in accordance with bending stress at the end of the beam and the number of the PC tendons 6. As a result, flexural rigidity can be increased by increasing the width of the beam end block 4 to be greater than the width of the steel beam, whereby the steel beam can have an economic and reasonable structure.

(25) In consideration that bending stress due to an earthquake load is large at a beam end and that the column 2 and the steel beam are joined by PC binding juncture, it is necessary to arrange multiple PC tendons 6 in the vertical direction. In addition, the PC tendons 6 in the span direction and the PC tendons 6 in the ridge direction must be arranged in such a manner as not to mutually interfere. In view of this, in the foregoing embodiment, the height of the beam end block 4 is made larger than the height dimension of the H-section steel 3, whereby mutual interference of the PC tendons 6 is prevented while the bending stress can be withstood.

(26) In a case in which the cross section of the H-section steel 3 constituting the steel beam can be small, the foregoing embodiment enables arranging the lowermost PC steel bar under the H-section steel 3, as in the column-beam junction structure 1 of the column 2 and the steel beam extending in the ridge direction in the foregoing embodiment. In this manner, in the case in which a necessary number of PC tendons 6 cannot be arranged without making the cross section of the H-section steel 3 larger than necessary in the whole length by a conventional technique, this situation can be coped with by enlarging only the beam end block 4 in this embodiment.

(27) At the end of the steel beam, the upper part protrudes toward the column 2 more than the lower part and the cogging 2a is disposed under the protruded upper part. This allows making an installation line of a ceiling very high so as to effectively make the most of the floor height. In addition, filling the space between the anchor plate 4e and the end plates 4a and 4c with the filler material 8 greatly improves flexural rigidity of the beam end block 4, thereby making it possible to reduce dimensions of the beam end block 4.

(28) Note that the invention of the present application is not limited to the foregoing embodiment and can be variously modified and altered. For example, although not illustrated, it is desirable to fill a cap that is attached to the anchoring device 7, with rust inhibitor, as rustproofing at ends of the anchoring device 7 and the PC tendon 6 that protrude from the surface of the column 2 on an outer periphery of a building. The anchoring device 7 may be covered with, e.g., shrinkage-compensating or no-contraction mortar, so as not to be exposed.

REFERENCE SINGS LIST

(29) 1: column-beam junction structure 2: column 2a: cogging 3: H-section steel 3a: upper flange 3b: web 3c: lower flange 4: beam end block 4a: outer end plate 4b: bed plate 4c: inner end plate 4d: bottom plate 4e: anchor plate 4f: side plate 5: joint mortar 6: PC tendon 7: anchoring device 8: filler material