JP2009275470A - Base plate for column base - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base plate for an exposed-type steel column base, which can adapt even to an increase in the size of a steel column by enhancing flexural rigidity without increasing the plate thickness of a base plate body portion. <P>SOLUTION: In this flat plate-like base plate 1, the base plate body portion 2 is fixed to a lower end of the steel column 4 on a top surface side; anchor bolts 6 protruding from foundation concrete 5 are inserted through a plurality of bolt insertion holes which are provided in the column outside portion 2b of the base plate body portion 2, and tightened with nuts 7 from above, respectively, so that the steel column 4 can be fixed to the foundation concrete 5. A plurality of plate-like portions 3 are erected astride a virtual borderline on the undersurface side of the base plate body portion 2, while leaving spaces among one another along the virtual borderline on which a fixing portion of the steel column 4 is projected. Thus, the column outside portion 2b of the base plate body portion 2, in which the anchor bolt 6 is arranged, is effectively reinforced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is fixed to the lower end of a steel column as an intermediate material for fixing the steel column to the foundation concrete in an exposed type column base structure such as a steel frame, a steel reinforced concrete structure, and a filled steel pipe concrete structure. The present invention relates to a column base plate.

  The column base plays an important role in transmitting axial force, shearing force and bending moment acting on the lower end of the column material to the foundation concrete. In the exposed steel column base, the compressive axial force is stress-transmitted from the steel column through the base plate to the foundation concrete, and the tensile axial force is transmitted from the steel column through the base plate to the anchor bolt and the foundation concrete. The bending moment transmits the compressive force from the steel column through the base plate on the one hand to the foundation concrete and, on the other hand, the tensile force from the anchor bolt to the foundation concrete. Further, transmission of shear force is generally classified into the following three types.

First, there is a method of transmitting by friction between the lower surface of the base plate and the surface of the foundation concrete. In this case, the shear strength depends on the column axial force, but the tensile strength of the anchor bolt does not decrease. Next, a washer having a hole substantially the same diameter as the anchor bolt diameter is welded to the upper surface of the base plate and transmitted from the base plate to the anchor bolt. In this method, the shear force does not depend on the column axial force, but the tensile strength of the anchor bolt is reduced. Furthermore, there is a method in which a shear key is welded to the lower surface of the base plate and transmitted from the steel column to the foundation concrete via the base plate (shear key). In this case, the shearing force does not depend on the column axial force, and the tensile strength of the anchor bolt does not decrease. Thus, the base plate is an important member for transmitting various forces acting from the steel column to the foundation concrete.

By the way, for a steel column with a relatively small column size, a base plate in which a standard rolled steel plate is cut into a rectangular plate of an appropriate size and a required number of bolt insertion holes are provided in the peripheral portion is easy to manufacture. For reasons such as this, it surpasses that of cast steel. On the other hand, since the anchor bolt is also increased in diameter as the column size of the steel column is increased, a base plate applied to a large-sized steel column is required to have high bending rigidity and yield strength. In the base plate made of rolled steel plate, the increase in the thickness of the column corresponds to the increase in the column size. However, the rolled steel plate for the base plate having a plate thickness exceeding 100 mm currently has the standard strength in the Building Standard Law. There is no setting and it cannot be used as a structural material. For this reason, even if productivity is sacrificed, it is the actual situation that it is unavoidable that it is made of cast steel. In addition, even if an extremely thick rolled steel sheet can be used, some problems are concerned when this is actually used. One of them is that the difference between the thickness of the steel column to be applied and the thickness of the base plate is too wide. This point affects weldability and can cause serious problems in the joint strength between the two. Under such circumstances, methods for dealing with an increase in the column size without increasing the thickness of the base plate have been studied. Specifically, a base plate in which a plurality of ribs are arranged on the upper surface side of a rectangular steel plate serving as a main body (Patent Document 1), and a two-stage base plate in which a plurality of ribs are arranged between two steel sheets (Patent Document 2) ), And the base plate (Patent Document 3), which has been integrally provided with a few millimeters of protrusions such as weld beads on the lower surface of the steel plate, has been proposed so far, both of which add rib-shaped stiffening means to the main body of the base plate It is what.
Japanese Utility Model Publication No. 61-33761 (see FIG. 2) JP 11-159007 A (see FIG. 6) Japanese Patent No. 3391438 (see FIG. 1)

In the base plate described in Patent Document 1, a nut screwed into an upper end portion of an anchor bolt protruding from a bolt insertion hole of the base plate main body portion is formed from both sides by a plurality of ribs integrally standing on the upper surface of the base plate main body portion. Since it is the structure enclosed, the operation space which does not prevent the rotation operation | movement of a spanner is required between the adjacent ribs, when tightening | tightening a nut. However, when multiple anchor bolts are arranged in the middle part of each side, such as a large base plate with a large number of anchor bolts, the interval between the ribs on those sides is set. It becomes difficult to secure enough. Therefore, it is conceivable to reduce the thickness of individual ribs or simply increase the total width of the base plate. However, both methods lead to a decrease in the bending rigidity of the base plate. Is not a good idea to increase the size of the base plate.

On the other hand, in the base plate described in Patent Document 2, since there is no rib on the upper surface side, there is no need to consider the operation space of the tightening tool, which was a problem of the former base plate, and the box shape allows the rib to be There is an advantage that a large bending rigidity and proof stress can be obtained as compared with the case where the stiffening is performed alone. In this case, since each member is integrated by welding work, the interval between the upper and lower two steel plates and the interval between the plurality of ribs arranged between them are important requirements in terms of productivity. It becomes. If productivity is prioritized and the gap between ribs is large, the stiffening effect for bending is reduced as in the former, so the thickness of the upper steel plate needs to be increased, and eventually it is large. The structure is not suitable for a size base plate. Furthermore, since the welding amount is increased as compared with the former base plate and the welding work is performed in a narrow space, there are problems such as poor workability.

Next, in the base plate described in Patent Document 3, the rigidity is intended to be improved by providing a plurality of ridges on the lower surface. However, the ratio between the thickness of the base plate body and the height of the ridges, or the base plate body Even from the ratio of the plate thickness of the part and the outer diameter of the anchor bolt (see FIG. 1), the effect is clearly secondary. That is, the original purpose of the ridge is to prevent relative displacement between the base plate and the mortar packed bed when a large lateral force (shearing force) acts on the column base due to an earthquake or the like. Is for. The main purpose of the ridges in this case is to increase the coefficient of friction between the bottom surface of the base plate and the mortar layer. Therefore, the pattern in which the compressive force is applied to the radial mortar packed layer is given priority. Is selected. In this prior art, the arrangement form from the viewpoint of improving the bending rigidity of the base plate and the shape of the ridge are not particularly taken into consideration. Accordingly, there is a lot of room for examination as to whether or not such ridges can be directly applied to a large-sized base plate.

  In view of these problems of the prior art, the present inventors have intensively studied the stiffening means to be added to the base plate body, and have arrived at the present invention. In other words, in the present invention, an effective arrangement form of the stiffening member is found, thereby increasing the bending rigidity without increasing the thickness of the base plate main body, increasing the outer diameter of the anchor bolt, and increasing the size of the steel column. The purpose is to provide a base plate for a column base that has become possible.

In order to solve the above-described problem, in the invention according to claim 1 of the present application, the base plate main body is fixed to the lower end of the steel column on the upper surface side, and the plurality of bolt insertion holes provided in the peripheral portion are provided with basic concrete. In a base plate for a column base for inserting a plurality of anchor bolts protruding from the surface and fixing the steel column to the foundation concrete by tightening a nut from above, the base plate main body portion is a plate smaller than the outer diameter of the anchor bolt A plurality of plate-like portions that are formed in a thick flat plate shape and are erected on the lower surface side in a state of straddling the line while being spaced apart from each other along a virtual contour line projected by the fixing portion of the steel column. The technical means was adopted. Thereby, a baseplate main-body part can be stiffened effectively.

Further, the plate-like portion in the above-described configuration is advantageously larger than the plate thickness of the base plate main body (Claim 2), and can be cast integrally with the base plate main body (Claim 3). .

In this invention, the following effects are acquired by employ | adopting the above structures.
(1) The stress from the anchor bolt exceeded the imaginary contour line of the base plate main body via a plurality of plate-like parts erected on the outer side of the column (peripheral) of the base plate main body and further on the lower surface thereof. Although transmitted to the inner side of the column, this region has a high bending deformation resistance by being restrained by the steel column on the upper surface side. For this reason, the plate-like portion whose one end side is stably supported by the column inner portion inside the virtual contour line reinforces the column outer portion of the base plate main body portion on the other end side by the rib effect and deforms. It can be effectively blocked. The presence of such a plate-like part (stiffening part) improves the bending rigidity of the base plate main body as a whole, making it possible to reduce the plate thickness of the base plate main body, and an economical column base structure. realizable.
(2) Since the plurality of plate-like parts are positioned on the lower surface side of the base plate main body with a space between each other, the plate-like part can be provided near the anchor bolt without considering any tightening operation of the nut. Thus, a base plate that makes the most of its reinforcing effect can be obtained.
(3) If the height of the plate-like portion is sufficiently larger than the plate thickness of the base plate main body, the reinforcing effect is further enhanced, and the plate thickness of the base plate main body can be further reduced. It is also convenient when an anchor bolt having an outer diameter larger than the plate thickness is used.
(4) If the plate-like portion is cast integrally with the base plate main body portion, the productivity is improved as compared with that by welding, and the degree of freedom in selecting the shape of the base plate main body portion and the plate-like portion is increased.

The base plate for a column base according to the present invention is technical in that it has found an effective shape and arrangement form for plate-like stiffening means such as ribs that have been studied in order to improve bending rigidity and proof stress. There is a special feature. This makes it possible to use anchor bolts with an outer diameter larger than the plate thickness of the base plate main body, and can be applied to steel columns with a large column size or anchor bolts with a large outer diameter while suppressing the plate thickness of the base plate main body. Became possible. The target steel frame column is not limited to a square steel pipe, but may be a round steel pipe or an H-shaped steel. In any case, the overall shape of the base plate body is preferably substantially rectangular in plan view. The material of the base plate body is not limited to a rolled steel plate, and cast steel may be used. In this case, it is possible to cast the plate-shaped part integrally with the base plate main body part. On the other hand, when the rolled steel plate is applied to the base plate main body, the plate-like portion may be integrated with the base plate main body by welding by combining appropriately sized steel plates, and the forming method and procedure thereof are not particularly limited. As for the crossing state of the plate-like portion with respect to the virtual outline of the steel column, not all of them cross each other at a right angle, and depending on the installation location, they may be crossed obliquely. In the present invention, due to the presence of the plate-like portion, the thickness of the base plate main body portion can be suppressed smaller than the outer diameter of the thick anchor bolt used in the column base of the steel column having a large column size. Moreover, if the height of the plate-like portion is ensured appropriately, it is possible to use a base plate body portion whose thickness is not so large. The positions of the bolt insertion holes through which the anchor bolts are inserted may be at least at the four corners of the base plate body. For example, there are various types depending on the number, such as those provided in plural at each corner, those provided at the sides between the corners, or those equally arranged along the four sides. Of course, various modifications can be made within the technical concept of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 1 to 4 show a first embodiment of a column base plate according to the present invention, and FIGS. 1 and 2 are a bottom view and a side view, respectively. The illustrated base plate 1 is intended for a steel column made of a square steel pipe, and is a square base plate main body 2 made of a rolled steel plate and a plurality of plates erected in a radial arrangement with respect to the lower surface thereof. It consists of the shape part 3. Each plate-like portion 3 is made of a small piece of rolled steel plate that is thinner than the plate thickness of the base plate main body portion 2 and has two rectangular corner portions having the same short side length and different long side lengths depending on the arrangement location. Is welded to the base plate main body 2 at the longer side that is not obliquely cut. Therefore, the height of each plate-like part 3 is the same.

  In the base plate main body 2, two bolt insertion holes 2 a are arranged at the four corners, and two bolt insertion holes 2 a are arranged at each corner so as to be parallel to a 45-degree tangent line drawn at the corner of the base plate main body 2. Furthermore, two pieces are also arranged in the middle part of each side, and a total of 16 bolt insertion holes 2a are provided. And between each of these bolt insertion holes 2a, each plate-like part 3 is in the center of the baseplate main-body part 2 in the state straddling the virtual outline 4a which the steel column 4 fixed to the upper surface side projects. One by one is arranged radially. Each plate-like part 3 does not necessarily need to intersect the virtual contour line 4a at the center in the long side direction, but rather it is preferable to bring it closer to the peripheral side of the base plate body part 2 from the viewpoint of the stiffening effect. In the embodiment, the length of the long side portion of the plate-like portion 3 arranged at the center of each side of the base plate main body portion 2 is the longest, but it is also possible to make them all the same length regardless of the arrangement location.

  3 and 4 are an explanatory view showing an assembling procedure of the column base plate 1 according to the present invention and a perspective view of the bottom side in a state of being fixed to the steel column. As shown in FIG. 3, the bolts are inserted so that each plate-like portion 3 straddles the virtual contour line 4 a projected on the lower surface side of the welding position 4 b of the steel column 4 set on the upper surface of the base plate main body portion 2. It arrange | positions between the holes 2a and welds. Next, welding is performed with the end surface of the steel column 4 in contact with the welding position 4b. The assembly procedure is not particularly limited.

  FIG. 5 is an explanatory diagram of a load bearing mechanism when a bending moment is applied in the column base structure using the column base plate 1 according to the present invention. In addition, about a construction method, the box-shaped recessed part which can accommodate the baseplate 1 in the surface part of the foundation concrete 5 is formed previously. In this recess, an upper end portion of an anchor bolt 6 having an outer diameter larger than the plate thickness of the base plate main body 2 and having a fixing plate (not shown) attached to the lower end portion protrudes by a predetermined length. Then, the upper end portion of each anchor bolt 6 is inserted into the bolt insertion hole 2a of the base plate 1 fixed to the lower end of the steel column 4, and the plate-like portion is inserted into the bottom surface of the concave portion of the foundation concrete 5 via an appropriate spacer or the like. After placing with a gap below 3, the nut 7 screwed into the anchor bolt 6 is tightened, and non-shrink grout mortar is injected into the space on the lower surface of the base plate body 2 by appropriate means. The non-shrink grout mortar is filled between the plate-like portions 3 without any gap. As a result, the steel column 4 is fixed to the foundation concrete 5 via the base plate 1. It should be noted that the steel column 4 or the like is placed as it is without providing a concave portion on the surface portion of the basic concrete 5, and the entire side surface of the base plate 1 is surrounded by an appropriate formwork, and in this state, the non-shrink grout mortar is filled. May be.

  Next, the mechanism of load resistance will be described. As shown in FIG. 5A, the tensile stress from the steel column 4 based on the bending moment M is transmitted to the anchor bolt 6 via the base plate 1. As shown in FIG. 5 (b), in the base plate main body 2, the column outer portion 2 b located outside the side surface of the steel column 4, that is, outside the virtual contour line 4 a is bent and deformed by the anchor bolt 6. Receive the stress to try. The stress is transmitted to the column inner portion 2 c of the base plate main body 2 by the plate-like portion 3 disposed on the lower surface of the base plate main body 2. Since the column inner portion 2c is restrained by the steel column 4 welded to the upper surface side of the base plate main body portion 2, the resistance to bending deformation is large, and thus the column outer portion 2b is effectively supported (stiffening). ) And no bending deformation.

  FIG. 6 is a comparative example of a column base plate in which the plate-like portion 3 does not straddle the virtual contour line 4 a of the steel column 4. In this case, since the stress is not sufficiently transmitted to the column inner portion 2c as in the above embodiment, bending deformation occurs near the boundary between the column outer portion 2b and the column inner portion 2c.

  7 to 9 are a bottom view of a column base plate according to a second embodiment of the present invention, a sectional view taken along line AA and a sectional view taken along line BB in FIG. 7, respectively. Note that the description of the same parts as in the above embodiment is omitted. The column base 8 shown in the figure is similar to the first embodiment. The base plate main body 9 is made of a rolled steel plate having a square shape, and the steel plate 11 having a rectangular closed cross section such as a square steel pipe is used as a target. It corresponds to the anchor bolt. In this case, the plate-like portion 10 includes a plurality of plate-like portions 10a formed of small pieces of rolled steel plate similar to the first embodiment, and one plate-like shape installed in the center of the base plate main body portion 9 in a cross shape in plan view. It is comprised with the part 10b. These plate-like parts 10 are installed so as to straddle the virtual contour line 11a projected by the steel column 11 fixed to the upper surface side of the base plate body part 9, and the height thereof is sufficiently larger than the base plate body part 9 It is. The plate-like portion 10b is close to the length of one side of the base plate main body portion 9, and a through hole 10c for facilitating the flow of the non-shrink grout mortar is provided on the side wall thereof. On the other hand, three plate-like portions 10 a are installed between each bolt insertion hole 9 a toward the center of the base plate main body portion 9, each being three in a cross section.

10 to 12 are a bottom view of a column base plate according to a third embodiment of the present invention, a front view of a state where a steel column is fixed, and a cross-sectional view taken along line AA in FIG. The illustrated column base 12 is composed of a square base plate main body 13 made of a rolled steel plate and 16 plate-like portions 14. The two plate-like parts 14a arranged on both sides of each bolt insertion hole 13a located at the four corners are erected toward the center of the base plate main body part 13 in a parallel state. Then, with respect to the bolt insertion hole 13a located at the center of each side portion, the direction in which the plate-like portions 14b slightly longer than the four corner portions are perpendicular to the sides of the base plate main body portion 13 in a state of being parallel to each other. It is erected in. These plate-like portions 14 are installed so as to straddle the virtual contour line 15a projected by the steel column 15 fixed to the upper surface side of the base plate main body portion 13, and are arranged on both sides of all the bolt insertion holes 13a. It will be. In addition, the height is sufficiently larger than the base plate main body 13 as in the above embodiments.

  FIGS. 13 and 14 are a bottom view of a column base plate according to a fourth embodiment of the present invention and a front view of a state where a steel column is fixed, respectively. The illustrated column base 16 for the column base is 45 degrees in which two bolt insertion holes 17a and 17a are drawn at the corners of the base plate main body 17 at the four corners of the square base plate main body 17 made of rolled steel. Two pieces are arranged at each corner so as to be parallel to the tangent line. Between the bolt insertion holes 17 a and 17 a located at the four corners, one plate-like portion 18 a is joined in a state directed toward the center of the base plate main body portion 17. And between the bolt insertion holes 17a located in the middle of each side, the plate-like portions 18b that are slightly shorter than the four corner portions are oriented in a direction perpendicular to the sides of the base plate main body portion 17 in a mutually parallel state. It is erected. These plate-like portions 18 are installed so as to straddle the virtual contour line 19a projected by the steel column 19 fixed to the upper surface side of the base plate body portion 17, and are arranged on both sides of all the bolt insertion holes 13a. It will be.

  FIG. 15: is the perspective view seen from the lower surface side of the base plate for column bases which concerns on 5th Example of this invention. The illustrated column base 20 for the column base is of the type having four anchor bolts in which bolt insertion holes 21 a are formed at the four corners of the base plate main body 21. The plate-like portions 22 are arranged in the same manner as in the third embodiment, and two of them are set as one set so as to straddle the virtual contour line 23a projected by the steel column 23 fixed to the upper surface side of the base plate main body portion 21. It is installed.

  FIG. 16: is the perspective view seen from the lower surface side of the base plate for column bases concerning 6th Example of this invention. The illustrated column base 24 is for a steel column made of H-shaped steel, and is intended for a type with four anchor bolts. The base plate body 25 is made of a rectangular rolled steel plate. On the lower surface, three plate-like portions 26a are spaced apart from each other so as to straddle the virtual contour lines 27a of the pair of flange portions projected by the steel column 27 fixed to the upper surface side of the base plate main body portion 25 in an orthogonal state. A plate-like portion 26b is provided on the virtual contour 27b of the web portion. Each of the four bolt insertion holes 25a is opened between the plate-like portions 26a at a position outside the virtual contour line 27a of both flange portions.

  In each of the above embodiments, a rolled steel plate is used as the base plate main body, and a plate-like portion made of a small steel plate is joined and integrated. However, both may be integrally formed by casting. It is also possible to jointly integrate both of them by making one of them made of cast steel and the other made of steel plate.

It is a bottom view of the column base plate according to the first embodiment of the present invention. It is a front view of the base plate for column bases shown in FIG. It is explanatory drawing which showed the assembly procedure of the base plate for column bases shown in FIG. It is the perspective view which showed the state after the assembly of FIG. It is explanatory drawing which showed the load-bearing mechanism when a bending moment is loaded on the column base structure using the base plate for column bases concerning this invention. It is explanatory drawing which showed the load-bearing mechanism when a bending moment is loaded on the column base structure using the base plate for column bases of a comparative example. It is a bottom view of the column base plate according to the second embodiment of the present invention. FIG. 8 is a cross-sectional view taken along line AA in FIG. 7. It is the BB sectional view in FIG. It is a bottom view of the column base plate according to the third embodiment of the present invention. It is the front view which fixed the steel column to the base plate for column bases shown in FIG. It is an AA line cross section in FIG. It is a bottom view of the base plate for column bases which concerns on 4th Example of this invention. It is the front view which fixed the steel column to the base plate for column bases shown in FIG. It is the perspective view seen from the lower surface side of the base plate for column bases concerning 5th Example of this invention. It is the perspective view seen from the lower surface side of the base plate for column bases concerning 6th Example of this invention.

Explanation of symbols

1, 8, 12, 16, 20, 24... Base plate for column base 2, 9, 13, 17, 21, 25... Base plate body 2 a, 9 a, 13 a, 17 a, 21 a, 25 a. 10b, 14a, 14b, 18a, 18b, 22, 26a, 26b29 ... plate-like part 4, 11, 15, 19, 23, 27 ... steel pillar 5 ... foundation concrete 6 ... anchor bolt 7 ... nut 10c ... through hole

Claims (3)

The base plate main body is fixed to the lower end of the steel column on the upper surface side, and multiple anchor bolts protruding from the foundation concrete surface are inserted into the multiple bolt insertion holes provided in the peripheral portion, and the nut from above In the base plate for the column base for fixing the steel column to the foundation concrete by tightening, the base plate main body is formed in a plate shape having a plate thickness smaller than the outer diameter of the anchor bolt, and the steel column is fixed to the lower surface side thereof A base plate for a column base, comprising: a plurality of plate-like parts that are erected along a virtual contour line projected by the part while being spaced apart from each other. The columnar base plate according to claim 1, wherein the plate-like portion has a height greater than a plate thickness of the base plate main body portion. The base plate for a column base according to claim 1 or 2, wherein the plate-like portion is integrally cast with the base plate main body portion.

Images