Method for manufacturing column-beam joint structure and the column-beam joint structure

Provided is a column-beam joint structure 1, wherein a plurality of thick-walled portions 3, notches 7, and narrow-width portions 9a on a central side of a flange plate 5 are formed integrally, cutting (dividing) is effected at a cut line 8, and the thick-walled portion 3 is welded and joined to a column 2a.

This application is the U.S. national phase of International Application No. PCT/JP2017/006017 filed Feb. 17, 2017, the entire contents of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a method for manufacturing a column-beam joint structure of steel structure which has a column and a beam and sets a yield point at a portion of the beam apart from a column-beam joint part, and to the column-beam joint structure.

BACKGROUND ART

As a column-beam joint structure to which the so-called RBS (Reduced Beam Section Connections) method for setting a yield point at a position apart from a column-beam joint part is applied, a column-beam joint structure60has been proposed in which a flange65and notches67are formed in a beam62distantly from a column-beam joint part62b, as shown inFIG. 15, for example.

PRIOR ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Problems that the Invention is to Solve

In Patent Document 1, a column-beam joint structure1is proposed in which notches7are provided in a beam flange plate5, and, in Patent Document 2, a column-beam joint structure is proposed in which notches7are formed in a reinforced plate5at positions apart from a column1.

Such a column-beam joint structure is adapted such that, when a large external force is applied due to an earthquake or the like, a ductile fracture or a brittle failure is prevented from occurring at a column-beam joint part owing to the external force.

However, with the column-beam joint structure1in Patent Document 1, it is necessary to secure an allowable value by more enlarging the beam width in order to prevent the fracture of the beam flange plate5at the column surface. As a result, there arises the need to more enlarge the column width, which makes economical design difficult, so that there is room for further improvement.

In addition, with the column-beam joint structure in Patent Document 2, since a method is adopted in which heating and the like are provided by applying a compressive force in a material axis direction (beam longitudinal direction) of a beam2, the manufacture becomes complicated, so that there is room for further improvement.

The present invention has been devised in view of the above-described aspects, and its object is to provide a method for manufacturing a column-beam joint structure and the column-beam joint structure which make it possible to reduce the weight of the steel material and are more inexpensive by preventing the enlargement of a column cross section owing to an increase in the bending width of the beam by making it unnecessary to form large notches in the flange plate for the beam. In addition, another object of the invention is to provide an inexpensive method for manufacturing a column-beam joint structure and the column-beam joint structure which ensure the weld strength of an end portion of the beam without needing to greatly enlarge the width of the flange plate and make it unnecessary to enlarge the column cross section, to thereby make it possible to prevent the occurrence of a ductile fracture and a brittle failure at a column-beam joint part due to a seismic force and maintain desired bending resistance of the beam.

Means for Solving the Problems

In accordance with the present invention, there is provided a column-beam joint structure wherein, at a column-beam joint part of a steel structure joining a column and a beam and having at least one first flange plate and at least one second flange plate for the beam, the first flange plate is joined through the joint part to a column surface at one end thereof with a substantially horizontal surface and is joined at another end thereof to the second flange plate opposing the column surface, and wherein the first flange plate and the second flange plate are joined to a web plate for the beam having a substantially vertical surface, and the first flange plate has a notch at a position apart from the column surface and at least one thick-walled portion in a vicinity of the joint part.

According to the column-beam joint structure in accordance with the present invention, since at least a thick-walled portion is provided in the first flange plate where a notch is formed, it is possible to further enlarge the welded joint cross section with respect to the column.

According to the present invention, it becomes possible to make smaller the width of the flange plate at a beam end portion in a widthwise direction of the beam, and it is unnecessary to make the column cross section large, so that economical design is made possible.

The column-beam joint structure in accordance with the present invention may have at least one pair of notches, and the at least one pair of notches are disposed at symmetrical positions in the widthwise direction of the beam.

According to the present invention, it is possible to simultaneously manufacture a plurality of flange plates for a beam having notches and at least one thick-walled portion.

In accordance with the present invention, there is provided a method for manufacturing a flange plate for the beam for a column-beam joint structure, comprising: a first step of forming in a steel plate for a beam a thick-walled portion and a thin-walled portion in a portion in a material axis direction of the steel plate excluding the thick-walled portion by rolling; a second step of forming a notch in the thin-walled portion apart from the thick-walled portion by rolling; and a third step of forming a narrow-width portion in the thin-walled portion by rolling.

According to the method for manufacturing a flange plate for a column-beam joint structure in accordance with the present invention, it is possible to efficiently manufacture thick-walled portions at beam end portions, notches, and narrow-width portions by rolling.

Accordance with the present invention, there is provided a method for manufacturing an H-shaped steel for a column-beam joint structure, which is a method for manufacturing an H-shaped steel for a beam in a column-beam joint structure constituted by a flange plate and a web plate, the H-shaped steel constituted by a thick plate being formed by the method comprising: a first step of forming in the flange plate of the H-shaped steel a thick-walled portion and a thin-walled portion in a portion in a material axis direction of the beam excluding the thick-walled portion by rolling; a second step of forming a notch in the thin-walled portion apart from the thick-walled portion by rolling; and a third step of forming a narrow-width portion in the thin-walled portion by rolling.

According to the present invention, it is possible to efficiently manufacture thick-walled portions at beam end portions, notches, and narrow-width portions by rolling.

Advantages of the Invention

According to the present invention, it is possible to ensure the weld strength of the beam end portion without enlarging the width of the flange plate. Consequently, since it is unnecessary to enlarge the width of the column, it becomes possible to suppress the weight of the steel material of the column, thereby making it possible to provide a method for manufacturing a column-beam joint structure and the column-beam joint structure which are inexpensive.

MODE FOR CARRYING OUT THE INVENTION

Next, a more detailed description will be given of the mode for carrying out the invention on the basis of preferred embodiments illustrated in the drawings. It should be noted that the present invention is not limited to these embodiments.

First Embodiment

InFIGS. 1 to 6, a column-beam joint structure1includes a column2aand a beam2joined to the column2a. One end51of a flange plate5has a substantially horizontal surface and is joined to a column surface of the column2aby welding at a column-beam joint part2b. A thick-walled portion (bulged portion)3is present at this welded portion. A web plate4of the beam2is joined to the column2aby welding. The beam2is a built-up H-shaped beam assembled by welding. The other end52of the flange plate5is butt-welded to a flange plate5aat a central portion in a material axial direction A (longitudinal direction of the beam2) of the beam2by a weld zone6. The flange plate5and the flange plate5aat the central portion are joined to the web plate4by welding6ato form the built-up H-shaped beam. Preferably, the flange plate5, the flange plate5aat the central portion, and the web plate4are joined in the form of the beam2by welding at a factory and is joined to the column2aat the time of steel frame erection.

In the column-beam joint structure1, although the web plate4of the beam2is welded and joined to the column2a, the web plate4of the beam2may alternatively be joined to the column2athrough a gusset plate and bolts (not shown).

When an external force generated in the beam2is applied to the column-beam joint structure1at the time of an earthquake, bending stress occurring in the beam2is large at the column-beam joint part2band becomes gradually smaller with an increasing distance from the column-beam joint part2b. Larger bending stress is applied to the column-beam joint part2bthan at a position distant from the column-beam joint part2b. However, with the column-beam joint structure1, since the one end51of the flange plate5is reinforced at the column-beam joint part2bby the thick-walled portion (bulged portion)3which is formed to be wider than the width of the other end52of the flange plate5in a widthwise direction of the beam2and to be thicker than the thickness of the other end52of the flange plate5in a vertical direction V, and a notch7is formed in the flange plate5at a position apart from the column2a, even if a large external force which is of such a measure that a ductile fracture or a brittle failure can occur is applied to the column-beam joint part2b, plastic deformation is made to occur at the notch7so as to form a yield hinge before a ductile fracture or a brittle failure occurs at the column-beam joint part2b.

Since the flange plate5is formed from a steel plate by roll forming in a state in which the notches7are provided thereon, it is unnecessary to provide reinforcing plates or the like on the flange plate5by welding or the like. In addition, reduction of the amount of steel can be achieved by using a steel plate of a high strength material as the flange plate5corresponding to the beam end portion where the stress is large and by using a steel plate of an ordinary material as the flange plate5acorresponding to the central portion of the beam2awhere the stress is small. Furthermore, the degree of freedom in design is enlarged since it is possible to freely change the amount of notch on the flange plate5constituting the notch7, the enlarged width of the flange plate5at the column-beam joint part2b, and the thickness of the flange plate5.

The followings are formed in a steel plate10for the column-beam joint structure: the thick-walled portion (bulged portion)3provided in the central portion in the material axis direction A; a pair of thin-walled portions9respectively provided on both sides in the material axis direction A of the thick-walled portion3; the two pairs of notches7each pair of which are provided on the respective thin-walled portion9; and a narrow-width portion9aprovided on each thin-walled portion9and formed to be narrow in a widthwise direction B of the beam2, and the pair of flange plates5and5aare formed integrally. A plurality of pairs of flange plates5and5aare formed integrally and are cut off at a cut line8, to thereby form the flange plate5shown inFIG. 2.FIG. 3is an explanatory view of a pair of flange plates5. The flange plate5is formed such that the outer cross-sectional size of the H-shaped steel becomes identical, and the thick-walled portion (bulged portion)3is formed in such a manner as to project from one surface of the flange plate5so as to jut out (bulge) toward the web plate4side.

As shown inFIGS. 7 to 10, the steel plate10(elongated body) is sequentially formed by a flat steel rolling machine20.FIG. 7shows the steel plate10in the state before processing.FIG. 8shows the steel plate10in a state in which the thick-walled portion (bulged portion)3and the thin-walled portions9at portions excluding the thick-walled portion3have been formed.FIG. 9shows the steel plate in a state in which the notches7are further formed by vertical rolls21. After this, the narrow-width portions9aof the flange plate5are formed, and the state shown inFIG. 1is obtained. It should be noted that the notches7and the narrow-width portions9amay be formed simultaneously by making the vertical rolls21horizontally movable.

The thick-walled portions3, the notches7, and the narrow-width portions9aof the thin-walled portions9may be formed gradually by repeatedly performing rolling by the vertical rolls21. Alternatively, however, the notches7and the narrow-width portions9aof the thin-walled portions9may be formed by cutting, grinding, shaving, gas cutting processing, and the like.

Second Embodiment

FIGS. 11 to 14show a method of manufacturing a rolling formed H-shaped steel31for the column-beam joint structure. The thick-plate H-shaped steel31constituted by flange plate portions31aand a web plate portion31bis manufactured by an H-shaped steel rolling machine30after undergoing a process similar to that shown inFIGS. 7 to 10. The thick-plate H-shaped steel31shown inFIG. 12is rolled into flange thick-walled portions (flange bulged portions)33and flange thin-walled portions39, as shown inFIG. 13. Subsequently, notches37and narrow-width portions39aare formed in the same way as the first embodiment. The beam2is manufactured by continuously processing a plurality of parts and is cut at cut lines38.

In the H-shaped steel31shown inFIG. 14, the flange thick-walled portions33, the notches37, and the narrow-width portions39aof the flange thin-walled portions39may be formed gradually by repeatedly performing rolling. Alternatively, however, the notches37and the narrow-width portions39aof the flange thin-walled portions39may be formed by cutting, grinding, shaving, gas cutting processing, and the like.

According to the present invention, the column-beam joint parts2bcan be more uniformly and efficiently in the same way as the first embodiment. In addition, since the flange thick-walled portion (flange bulged portion)33is present at one end portion of the flange plate portion31a, it is possible to obtain high weld joint strength without enlarging the width of the flange plate portion31a.

The flange plates5and5aand the H-shaped steel31in accordance with the present invention may be formed not only by roll forming but by forging. In a case where forming is to be performed by using the flange plates5and5aand the flange plate portions31awhose outer surfaces are constant, the flange plates5and5aand the flange plate portions31aare appropriately formed by being pressurized from one side thereof.

DESCRIPTION OF REFERENCE NUMERALS