JP7351759B2 - Connection structure of exposed column base - Google Patents

Description

The present invention relates to a joint structure for exposed column bases.

Conventionally, an exposed column pedestal is known in which a substantially rectangular base plate is joined to the lower end of the exposed column pedestal, and an anchor bolt is inserted through the base plate to fix it to a foundation. For these exposed column bases, the anchor bolt yield type, column yield type, base plate yield type, and composite type (anchor bolt yield type + base plate yield type) have been proposed as yield types to cope with earthquakes.

The anchor bolt yield type is a type in which the base plate is strengthened and the anchor bolt yields first, and has excellent elongation ability. The column yielding type is a type in which the base plate and anchor bolts are made strong and the deformation capacity is borne by the column, and it has excellent seismic energy absorption ability. The base plate yielding type is a type in which the columns and anchor bolts are strengthened and the base plate is yielded.

The composite type has a yielding anchor bolt and a base plate arranged in parallel, and a non-yielding anchor bolt and base plate, and is said to have excellent deformation ability and seismic energy absorption ability. On the other hand, the composite yield mechanism (load-bearing mechanism) is complex and difficult to use in design from the viewpoint of deformation control.

The present applicant has proposed a joint structure with a composite yield type, which includes a first base plate to which the lower end of the exposed column leg is connected as a base plate, and a second base plate that extends outward from the first base plate. A joint structure for column bases has been proposed (Patent Document 1). In this joint structure, the yield strengths of the first base plate, the second base plate, the first anchor bolt that fixes the first base plate, and the second anchor bolt that fixes the second base plate are determined in advance. By setting it in a relationship, it is designed to absorb earthquake energy. According to this joint structure, excellent seismic energy absorption capacity can be ensured.

Patent No. 6140209

However, even in the bonding structure of Patent Document 1, further improvements have been desired in order to fully exhibit the energy absorption ability. In addition, in the case of the joint structure of Patent Document 1, the second base plate extends outward from the periphery of the first base plate, so the second base plate becomes larger and the foundation column shape also becomes larger. There was a problem that it became. Furthermore, in the case of the joint structure of Patent Document 1, there is a problem that the action of the axial force becomes complicated depending on the position of the first anchor bolt, and it takes time and effort to design the base plate.

The present invention has been made in view of the above-mentioned circumstances, and is a composite type exposed column base joint structure that has excellent seismic energy absorption efficiency and can reduce the size of the base plate. The objective of the present invention is to provide a joint structure for exposed column bases that can simplify the design.

In order to solve the above-mentioned problems, the present invention provides an exposed column pedestal joint structure in which an anchor bolt is inserted into a base plate which is connected to the lower end of the exposed column pedestal and has a substantially square shape when viewed from above, and is fixed to the foundation. hand,
The base plate is
a first base plate to which the lower end of the column is connected;
a second base plate located at the four corners and having a substantially right-angled isosceles triangular shape in top view, including an apex, an opposite side opposite the apex, and two short sides forming the apex;
has
The second base plate has the apex corner portion and the short side portion located on the outside,
The first base plate is located inside the second base plate and is joined to the opposite side of the second base plate,
Furthermore, the first base plate has a higher yield strength than the second base plate,
A first anchor bolt is inserted into a column width region of the first base plate located between the adjacent second base plates,
A second anchor bolt having a higher yield strength than the first anchor bolt is inserted into the second base plate,
The second base plate and the first anchor bolt are capable of yielding when an earthquake occurs.

The exposed column base joint structure of the present invention has excellent seismic energy absorption efficiency, can reduce the size of the base plate, and can simplify the design.

FIG. 1 is a cross-sectional view illustrating an embodiment of the exposed column base joint structure of the present invention. FIG. 2 is a top view of the joint structure of the exposed column base shown in FIG. 1; FIG. 3 is a cross-sectional view illustrating a yield state when an earthquake occurs in the joint structure of exposed column bases in FIGS. 1 and 2. FIG. FIG. 3 is a cross-sectional view illustrating a yield state when an earthquake occurs in the joint structure of exposed column bases in FIGS. 1 and 2. FIG. It is a top view which illustrated another embodiment of the joint structure of the exposed column base of this invention. FIG. 3 is a cross-sectional view illustrating another embodiment of the exposed column pedestal joint structure of the present invention. FIG. 6 is a top view showing an embodiment in which a yield hinge line is formed on the second base plate in the exposed column pedestal joint structure of the present invention. FIG. 3 is a cross-sectional view illustrating variations in the connection form of the first base plate and the second base plate in the exposed column base joint structure of the present invention. FIG. 3 is a cross-sectional view illustrating variations in the connection form of the first base plate and the second base plate in the exposed column base joint structure of the present invention. It is a top view which illustrated the variation of the base plate (1st base plate and 2nd base plate) in the joint structure of the exposed column base of this invention. It is a top view which illustrated another variation of the base plate (1st base plate and 2nd base plate) in the joint structure of the exposed column base of this invention.

An embodiment of the exposed column pedestal joint structure of the present invention will be described. FIG. 1 is a cross-sectional view illustrating an embodiment of the exposed column base joint structure of the present invention. FIG. 2 is a top view of the joint structure of the exposed column base shown in FIG. 1. 3 and 4 are cross-sectional views illustrating a yield state when an earthquake occurs in the exposed column base joint structure illustrated in FIGS. 1 and 2.

In the exposed column pedestal joint structure of the present invention, an anchor bolt 3 is inserted into a base plate 2 joined to the lower end of the exposed column pedestal 1, and is fixed to a concrete foundation 4.

Examples of the exposed column base 1 include a square steel pipe column and a round steel pipe column.

The base plate 2 has a substantially square shape when viewed from above, and is composed of a first base plate 21 and a second base plate 22. As shown in FIG. 1, a base mortar 41 is constructed below the second base plate 22.

The lower end portion of the column is joined to the first base plate 21 . In this embodiment, the planar outline of the first base plate 21 is approximately octagonal, and includes two sets of opposing short sides 21a and two sets of opposing long sides 21b. The lengths of the respective short sides 21a are designed to be equal to each other. Further, the lengths of the long sides 21b are also designed to be equal.

The second base plate 22 is located at the four corners of the base plate 2, and the first base plate 21 is located inside this second base plate 22. In this embodiment, the second base plate 22 is formed one step lower than the first base plate 21.

Each of the second base plates 22 located at the four corners has a substantially right-angled isosceles triangular shape when viewed from above, and has an apex portion 22a, an opposite side portion 22b opposite to the apex portion 22a, and two portions forming the apex portion 22a. It has a short side portion 22c. The apex portion 22a and the short side portion 22c are located on the outside of the base plate 2.

In this embodiment, the long side 21b of the first base plate 21 and the opposite side 22b of the second base plate 22 are designed to have equal lengths, and are joined to each other. Furthermore, the short side 21a of the first base plate 21 and the short side 22c of the second base plate 22 are joined in the same straight line at the outer edge of the base plate 2.

The first base plate 21 has a higher yield strength than the second base plate 22. Thereby, when an earthquake occurs, the second base plate 22 is relatively easily deformed elastically or plastically, and can absorb earthquake energy.

The yield strength of the first base plate 21 and the second base plate 22 can be set as appropriate depending on the scale of the expected earthquake, the structure of the building, etc., but for example, as a rough guide, the yield strength of the second base plate 22 is 15. It is preferably 500 kNm. Further, the difference in yield strength between the first base plate 21 and the second base plate 22 is preferably about 20 to 300 kNm. Thereby, it is possible to more effectively increase the absorption efficiency of earthquake energy.

Although the method of adjusting the yield strength of the first base plate 21 and the second base plate 22 is not particularly limited, for example, when the first base plate 21 and the second base plate 22 are made of the same material, A method of making the thickness thicker than the second base plate 22 can be exemplified.

In this joining structure, the angle between the short side 22c and the opposite side 22b of the second base plate 22 is approximately 45°, and the position of the opposite side 22b of the second base plate 22 (the boundary between the first base plate 21 and the second base plate 22) is approximately 45 degrees. ) coincides with the yield line, improving the absorption efficiency of seismic energy. Here, the term "yield line" refers to a line that appears when the second base plate undergoes bending deformation and yields.

The length of the short side 21a of the first base plate 21 can be appropriately designed depending on the size of the exposed column base 1 and the like. Specifically, as a design guideline, for example, if the length of one side of the base plate is B, then the length e of the short side 21a of the first base plate 21 should satisfy 0<e≦B/2. preferable.

The length (mm) of one side of the base plate can be exemplified in the range of 300≦B≦900. Thereby, the absorption efficiency of earthquake energy can be increased.

When the length from the exposed column base 1 to the outer edge of the base plate 2 is b, the length c of the short side portion 22c of the second base plate 22 preferably satisfies b≦c<B/2. Thereby, the absorption efficiency of earthquake energy can be increased.

The length b2 (mm) from the column center line to the outer edge of the base plate can be in the range of 150≦b2≦450.

The first base plate 21 is easily affected by the rotation of the exposed column base 1, but by designing it to have a large thickness, for example, it becomes difficult to deform and becomes difficult to become plastic. On the other hand, the second base plate 22 is not easily affected by the rotation of the exposed column base 1, but if it is designed to have a thinner thickness, for example, it becomes more likely to become plastic.

Anchor bolt 3 includes a first anchor bolt 31 and a second anchor bolt 32.

The first anchor bolt 31 is inserted into a column width region D of the first base plate 21 located between adjacent second base plates 22 . In this embodiment, a total of eight first anchor bolts 31, two each in the column width region D of the first base plate 21, are inserted, and the eight first anchor bolts 31 are aligned with respect to the column center line. arranged symmetrically. Note that the first base plate 21 is provided with a first anchor bolt insertion hole 211, and the first anchor bolt 31 is inserted through the first anchor bolt insertion hole 211 and fastened with a nut.

The second anchor bolt 32 is inserted through the second base plate 22. In this embodiment, one second anchor bolt 32 is inserted inside the apex corner portion 22a of each second base plate 22. The second base plate 22 is provided with a second anchor bolt insertion hole 221 through which the second anchor bolt 32 is inserted, and the second anchor bolt 32 is inserted into the second anchor bolt insertion hole 221 and fastened with a nut. has been done.

Moreover, the length a (mm) from the column center line to the second anchor bolt 32 can be exemplified in the range of 150≦a≦400. Thereby, the absorption efficiency of earthquake energy can be increased.

The second anchor bolt 32 has a higher yield strength than the first anchor bolt 31. Thereby, when an earthquake occurs, the first anchor bolt 31 is relatively easily deformed plastically, and can absorb earthquake energy.

The yield strength of the first anchor bolt 31 and the second anchor bolt 32 can be set as appropriate depending on the scale of the expected earthquake, the structure of the building, etc., but as a rough guide, it is, for example, 15 to 900 kN. It is preferable. Further, the difference in yield strength between the second anchor bolt 32 and the first anchor bolt 31 is preferably about 20 to 800 kN. Thereby, it is possible to more effectively increase the absorption efficiency of earthquake energy.

Further, the yield strength of the first anchor bolt 31 and the second anchor bolt 32 can be set to a desired yield strength by adjusting the thickness (diameter), number, etc., for example.

Note that the forms of the first anchor bolt 31 and the second anchor bolt 32 are not particularly limited, and for example, conventionally known forms such as those illustrated in Patent Document 1 can be used as appropriate.

The first anchor bolt 31 is close to the exposed column base 1. Therefore, since the first base plate 21 does not become plasticized and the second base plate 22 does, the first anchor bolt 31 is easily influenced by the rotation of the exposed column base 1 and becomes easily plasticized.

The second anchor bolt 32 is far from the exposed column base 1. Therefore, since the first anchor bolt 31 becomes plastic and the second base plate 22 becomes plastic, the second anchor bolt 32 is less affected by the rotation of the exposed column base 1 and becomes less likely to become plastic.

Therefore, as shown in FIG. 9, when an earthquake force of an assumed magnitude is applied, the second base plate 22 and the first anchor bolt 31 undergo elastic-plastic deformation and yield.

Further, as shown in FIG. 4, the second base plate 22 causes bending deformation by rotating around the corner, and the first base plate 21 rotates around the outer surface of the column, causing the first anchor bolt 31 to bend. causes elastic-plastic deformation. When the first base plate 21 tries to rotate in opposite directions, a tensile force is generated in the first base plate 21, thereby increasing the strength even in the large deformation region. Therefore, as the deformation increases, it is possible to compensate for the decrease in proof strength caused by the additional bending moment due to the vertical load.

In this joint structure of the exposed column base 1, the first base plate 21 is located inside the second base plate 22, and the opposite side 22b of the second base plate 22 and the long side 21b of the first base plate 21 are connected. are doing. Furthermore, the short side 21a of the first base plate 21 and the short side 22c of the second base plate 22 are joined in the same straight line at the outer edge of the base plate 2. Therefore, the size of the base plate 2 can be reduced.

Further, the opposite side portion 22b of the second base plate 22 is formed at an angle of approximately 45° with respect to the outer edge of the base plate 2, and the opposite side portion 22b of the second base plate 22 (the boundary between the first base plate 21 and the second base plate 22) ) coincides with the yield line, so it has excellent seismic energy absorption efficiency.

Further, the first anchor bolt 31 is inserted into the column width region D of the first base plate 21 located between the adjacent second base plates 22, and connects the apex corners 22a of the opposing second base plates 22. The first anchor bolt 31 does not exist near the diagonal line (A-A line shown in FIG. 4). Therefore, when designing the base plate 2, it is possible to design the base plate 2 by considering only the axial force of the first anchor bolt 31, thereby simplifying the design work and reducing manufacturing costs.

FIG. 5 is a top view illustrating another embodiment of the exposed column pedestal joint structure of the present invention. FIG. 6 is a cross-sectional view illustrating another embodiment of the exposed column pedestal joint structure of the present invention. Descriptions of parts common to the embodiments shown in FIGS. 1 to 4 will be omitted.

In the exposed column pedestal joint structure of the embodiment shown in FIG. is formed. The thick portion 24 has a substantially pentagonal shape when viewed from above, and includes an upright surface 24a parallel to the opposite side portion 22b of the second base plate 22 (the long side 21b of the first base plate 21). When the thick wall portion 24 has such a configuration, the deformation region f of the second base plate 22 caused by relative displacement becomes longer, so that local deformation of the second anchor bolt 32 becomes less likely to occur, and energy caused by an earthquake can be efficiently used. Can be absorbed.

In the exposed column base joining structure of the embodiment shown in FIG. 6, a thick washer 25 having the same thickness as the first base plate 21 is disposed on the second base plate 22 through which the second anchor bolt 32 is inserted. This thick washer 25 has a substantially pentagonal shape when viewed from above, similar to the thick wall portion 24 shown in FIG. It is equipped with Also in this embodiment, local deformation of the second anchor bolt 32 is less likely to occur, and energy caused by an earthquake can be efficiently absorbed.

Note that the thick wall portion 24 shown in FIG. 5 and the thick washer 25 shown in FIG. 6 can also be formed in an arc shape centered on the apex corner portion 22a.

FIG. 7 is a top view showing an embodiment in which a yield hinge line is formed on the second base plate in the exposed column pedestal joint structure of the present invention.

As illustrated in FIG. 7, in this embodiment, an elastic-plastic region T is formed between a first yield hinge line L1 and a second yield hinge line L2 that are parallel to each other and are spaced apart at a predetermined interval. .

The first yield hinge line L1 is formed on the opposite side 22b (shown in FIG. 2 etc.) of the second base plate 22, and the second yield hinge line L2 is formed in a straight line passing through the second anchor bolt 32. ing. The first yield hinge line L1 and the second yield hinge line L2 are formed at an angle of approximately 45 degrees with respect to the outer edge of the base plate 2.

The elastic-plastic region T is formed so that the yield strength is partially lower than that of other parts of the second base plate 22. Therefore, when an earthquake occurs, elastic deformation or plastic deformation can be caused in this elastoplastic region T.

8 and 9 are cross-sectional views illustrating variations in the connection form of the first base plate and the second base plate in the exposed column base joint structure of the present invention. In FIGS. 8(a) to (i) and FIGS. 9(j) to (p), the elastic-plastic region T due to the yield hinge line is indicated by diagonal lines.

As illustrated in FIGS. 8(a) to 8(c), the second base plate 22 is formed thinner than the first base plate 21. As shown in FIGS. Further, the vertical position of the second base plate 22 is not particularly limited. Specifically, the second base plate 22 can be joined to the lower side of the first base plate 21 (FIG. 8(a)), and the upper surface of the second base plate 22 may be aligned with the upper surface of the first base plate 21. It can be joined (FIG. 8(b)), and it can also be joined near the vertical center of the first base plate 21 (FIG. 8(c)).

As illustrated in FIGS. 8(d) to (f), the second base plate 22 has a thin elastic-plastic region T formed on the first base plate 21 side. The elastic-plastic region T can have various cross-sectional shapes that are thinner than the thickness of the first base plate 21 or the second base plate 22.
Further, as illustrated in FIGS. 8(d) to 8(f), the first base plate 21 and the second base plate 22 having the thick portions 24 integrally molded at the corners may be made separate members and joined to each other. Can be done.

As illustrated in FIGS. 8(g) to (i), the first base plate 21, the second base plate 22, and the thick portion 24 can be made into separate members and then joined to each other.

As illustrated in FIGS. 9(j) to (l), the first base plate 21 and the second base plate 22 can be integrally molded.

As illustrated in FIGS. 9(m) to (o), the first base plate 21, the second base plate 22, and the thick portion 24 can be integrally molded.

As illustrated in FIG. 9(p), the first base plate 21, the second base plate 22, and the thick washer 25 are each made into separate members, and the first base plate 21 and the second base plate 22 are joined to each other. A thick washer 25 can be disposed at the corner of.

FIG. 10 is a top view illustrating variations of the base plates (first base plate 21 and second base plate 22) in the exposed column base joint structure of the present invention.

In the base plate illustrated in FIGS. 10(A) to 10(D), the first base plate 21 has a substantially octagonal shape, and the first anchor bolt insertion holes are provided at one or two locations in the column width region of the first base plate 21. 211 is provided. Further, second anchor bolt insertion holes 221 are provided in one or two locations in the second base plate 22 .

In the base plate illustrated in FIGS. 10(E) to (H), the planar outline of the first base plate 21 is approximately square, and the short sides 22c of the adjacent second base plates 22 are joined at the outer edge of the base plate 2. There is. Also in this embodiment, the first base plate 21 is located inside the second base plate 22, and the opposite side 22b of the second base plate 22 and one side 21c of the first base plate 21 are connected. Further, the corner portion 21d of the first base plate 21 is located at the outer edge of the base plate 2. Also in this embodiment, the size of the base plate 2 can be reduced.

Also in this embodiment, the angle of the opposite side part 22b with respect to the outer edge of the base plate 2 is approximately 45 degrees, and the position of the opposite side part 22b of the second base plate 22 (the boundary between the first base plate 21 and the second base plate 22) is line (yield hinge line), so it has excellent seismic energy absorption efficiency.

Furthermore, in this embodiment as well, the first anchor bolt insertion hole 211 is provided in the column width region D of the first base plate 21 located between the adjacent second base plates 22, and The first anchor bolt insertion hole 211 is not provided near the diagonal line connecting the apex corners 22a. Therefore, when designing the base plate, it is possible to design the base plate by considering only the axial force of the first anchor bolt 31, which simplifies the design work and reduces manufacturing costs.

The base plate 2 illustrated in FIGS. 10(I) and 10(J) is provided with a thick wall portion 24 that is approximately pentagonal in top view on the inside of the apex corner portion 22a of the second base plate 22, and will be explained using FIG. This corresponds to the embodiment described above.

In the base plate 2 illustrated in FIGS. 10(K) and 10(L), a thick wall portion 24 having an arcuate shape in top view centered on the apex corner 22a is provided inside the apex corner 22a of the second base plate 22. .

FIG. 11 is a top view illustrating another variation of the base plate (first base plate and second base plate) in the exposed column base joint structure of the present invention.

The base plate 2 illustrated in FIGS. 11(M) to (U) is provided with a rib plate 5 so as to surround the first anchor bolt 31 of the first base plate 21. Specifically, two rib plates 5 extend from each side of the exposed column base 1 toward the outer edge of the first base plate 21 . On each side of the exposed column base 1, adjacent rib plates 5 are parallel to each other, and the first anchor bolt 31 is located between the rib plates 5. By providing the rib plate 5, it is possible to increase the yield strength and rigidity of the first base plate 21 and to make a difference in relative yield strength between the first base plate 21 and the second base plate 22. Therefore, the yield strength of the second base plate 22 can be adjusted to be relatively low with respect to the first base plate 21.

The exposed column base joint structure of the present invention is not limited to the above embodiments. For example, the shape of the first base plate, the size of the second base plate, etc. can be designed as appropriate.

1 Exposed column base 2 Base plate 21 First base plate 21a Short side 21b Long side 22 Second base plate 22a Apex corner 22b Opposite side 22c Short side 3 Anchor bolt 31 First anchor bolt 32 Second anchor bolt

Claims (7)

A joint structure of an exposed column pedestal in which an anchor bolt is inserted through a base plate having a substantially square shape in top view and fixed to the foundation, which is connected to the lower end of the exposed column pedestal,
The base plate is
a first base plate to which the lower end of the column is connected;
a second base plate located at the four corners and having a substantially right-angled isosceles triangular shape in top view, including an apex, an opposite side opposite the apex, and two short sides forming the apex;
has
The second base plate has the apex corner portion and the short side portion located on the outside,
The first base plate is located inside the second base plate and is joined to the opposite side of the second base plate,
Furthermore, the first base plate has a higher yield strength than the second base plate,
A first anchor bolt is inserted into a column width region of the first base plate located between the adjacent second base plates,
A second anchor bolt having a higher yield strength than the first anchor bolt is inserted into the second base plate,
A joint structure for exposed column bases, characterized in that the second base plate and the first anchor bolt are capable of yielding in the event of an earthquake. The planar outline of the first base plate is approximately octagonal, consisting of two sets of opposing short sides and two sets of opposing long sides;
2. The exposed column pedestal joining structure according to claim 1, wherein the short side of the first base plate and the short side of the second base plate are joined in the same straight line at an outer edge of the base plate. The planar outline of the first base plate is approximately square;
2. The exposed column pedestal joint structure according to claim 1, wherein the short sides of the adjacent second base plates are joined to each other at an outer edge of the base plate. 4. The exposed column pedestal joint structure according to claim 1, wherein the position of the opposite side of the second base plate coincides with a yield line. 5. The exposed column pedestal joining structure according to claim 1, wherein the first anchor bolt is not present near a diagonal line connecting the apex corners of the opposing second base plates. 6. The exposed column pedestal joint structure according to claim 1, wherein the second base plate has a yield strength of 15 to 500 kNm. 7. The exposed column pedestal joint structure according to claim 1, wherein the second anchor bolt has a yield strength of 15 to 900 kN.

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