JP2011102513A - Anchor bolt for column base - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anchor bolt for a column base, which can make the shaking of a building small during small-and-moderate-sized earthquakes, which can absorb earthquake energy by making a length center portion elongated along with plastic deformation before a male screw portion ruptures during a big earthquake, and which can reduce manufacturing costs. <P>SOLUTION: A screw portion 32, which is formed of a deformed bar having protrusions such as a knot 38 and a rib 36 provided on a peripheral surface and which has a male screw with an outside diameter larger than a nominal diameter set between the height center portions of the protrusion in the diametrical direction of its cross section, is formed in at least one end. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an anchor bolt for a column base that connects a column base metal and a foundation concrete joined to a lower end portion of a column member in a building.

  As a conventional column base anchor bolt, for example, as shown in FIG. 4, there is a column base anchor bolt 2 formed of a deformed steel bar (deformed bar). This conventional anchor bolt 2 for a column base has been used in a column base structure 1 for connecting a column base metal 6 joined to a lower end portion of a column member 4 constituting a part of a building and a foundation concrete 8. .

  That is, the conventional anchor bolt 2 for a column base is embedded in the foundation concrete 8 and is formed in a length portion on the upper end side protruding upward from the foundation concrete 8 and screwed to the male screw portion 10. 12 presses the upper surface of the column base metal 6 through the washer 14 to connect the column base metal 6 and the foundation concrete 8.

  Further, the column base anchor bolt 2 has a male screw portion 16 formed at the lower end thereof, and after fixing a fixing plate 18 projecting horizontally larger than the diameter of the nut 20 to the male screw portion 16, the nut 20 is screwed. It came to unite. Moreover, the column base 6 was arranged on the foundation concrete 8 via the mortar part 15.

  The central portion 22 between the male screw portion 10 and the male screw portion 16 in the above-described conventional column base anchor bolt 2 can be treated as having a nominal diameter DK (see FIG. 5). Moreover, the convex part of the node 23 and the rib 24 is formed in the peripheral part of the deformed steel bar as the center part 22 between the male screw part 10 and the male screw part 16 of the conventional anchor bolt 2 for column base.

  Here, the nominal diameter DK of the central portion 22 shown in FIG. 5 is that a round bar having the same length as the central portion 22 is formed by the same mass as the deformed steel bar as the central portion 22. When hypothesized, it refers to the diameter of such a round bar. The cross-sectional area of the virtual round bar calculated based on the nominal diameter DK is referred to as an effective cross-sectional area AK.

  The nominal diameter DK is larger than the diameter D2 obtained by removing the nodes 23 and the ribs 24 from the deformed steel bar as the center portion 22, and the heights of the nodes 23 and the ribs 24 in the diameter direction of the cross section in the center portion 22. It is set between the central portions (a pair).

  As shown in FIG. 4, the conventional column base anchor bolt 2 formed of the above-described deformed steel bar has a small shaking that does not cause the building to be damaged by a weak earthquake or the like. In order not to impair the habitability of the building, the nodes and ribs are hooked on the foundation concrete 8 to suppress the extension of the anchor bolts 2 for column bases and to act to suppress the shaking of the building. It was suitable for.

  On the other hand, when the conventional anchor bolt 2 causes a large shake that may cause damage to the building due to a large earthquake or the like, in order to prevent the building from being damaged, It is desirable that vibration energy is absorbed by stretching with plastic deformation due to the acting tensile load.

  As conventional anchor bolts 2 described above, conventional anchor bolts formed from deformed steel bars include those described in Patent Documents 1 and 2, for example.

JP 2006-125157 A JP 2006-291627 A

  However, in the above-described conventional column base anchor bolt 2, as shown in FIG. 5, when the male screw portion 10 is formed by thread cutting, the outer diameter D1 of the male screw portion 10 is the deformed steel bar of the central portion 22. It becomes smaller than the diameter D2 when the joint 23 and the rib 24 are removed. Therefore, the outer diameter D1 of the male thread portion 10 is necessarily smaller than the nominal diameter DK of the central portion 22, and thus the conventional column base anchor bolt 2 has the following problems. .

  That is, the external thread portion 10 of the conventional column base anchor bolt 2 is formed so that the outer diameter dimension D1 thereof is smaller than the nominal diameter DK of the central portion 22 as described above. If the diameter D3 of the screw valley that is smaller than the effective diameter is defined as an effective diameter, the effective area A3 determined based on the effective diameter is smaller than the effective area AK of the central portion 22.

  Therefore, the conventional column base anchor bolt 2 works per unit area of the effective cross-sectional area A3 of the male thread portion 10 when it is considered that the tensile load P is uniformly transmitted along the length direction thereof. The tensile stress (P / A3) is always larger than the tensile stress (P / AK) acting per unit area of the effective cross-sectional area AK of the deformed steel bar in the central portion 22.

  Therefore, the conventional column base anchor bolt 2 has a correlation between stress and strain with respect to the material of the deformed steel bar used as the material (hereinafter, referred to as the material of the column base anchor bolt 2). When the tensile load P in FIG. 5 increases, the tensile stress (P / A3) of the male thread portion 10 becomes the tensile force of the central portion 22 when considering the strain-stress diagram of FIG. Prior to the stress (P / AK), the yield stress σy and the tensile strength σu in FIG. 6 are reached in sequence.

  Here, the yield ratio (σy / σu) determined based on the yield stress σy and the tensile strength σu as one of the material properties of the conventional column base anchor bolt 2 is assumed to be as follows. If the value is higher than the cross-sectional area ratio (A3 / AK), the relationship between the yield ratio (σy / σu) and the cross-sectional area ratio (A3 / AK) is as shown in Equation 1 below. Can be represented. Further, the formula 1 can be modified as the formula 2.

  When there is such a relationship between the yield ratio (σy / σu) and the cross-sectional area ratio (A3 / AK) in the conventional column base anchor bolt 2, the conventional column base anchor bolt 2 is added. When the tensile load P increases and the tensile stress (P / A3) of the male thread 10 reaches the tensile strength σu (point U in FIG. 6), that is, (P / A3) = σu Since σu in Equation 2 can be replaced with (P / A3), Equation 2 can be modified as Equation 3 below.

  Equation 3 above shows that the tensile stress (P / AK) of the central portion 22 is still the yield stress even when the tensile stress (P / A3) of the male thread 10 reaches the tensile strength σu (point U in FIG. 6). This means that σy has not been reached (point X in FIG. 6).

  Then, in the conventional column base anchor bolt 2, the central portion 22 is stretched with plastic deformation until the tensile stress (P / A3) of the male thread portion 10 reaches the tensile strength σu and breaks. There will be no. In such a case, the conventional column base anchor bolt 2 cannot exhibit the function of absorbing vibration energy in the event of a large earthquake or the like.

  For this reason, the column base anchor bolt 2 is not a general material that is commercially available in order to be able to exhibit the function of absorbing vibration energy in the event of a large earthquake as described above. It was necessary to use a specially manufactured material so that the yield ratio (σy / σu) was smaller than the numerical value of the cross-sectional area ratio (A3 / AK).

  Accordingly, the column base anchor bolt 2 is, for example, a deformed steel bar having a nominal diameter of D29, D32, D35, D38, and corresponding to each of the nominal diameters of the deformed steel bars. In the case where the male screw portion 10 having M27, M30, M33, and M36 is formed, the yield ratio (σy / σu) smaller than the numerical value of the cross-sectional area ratio (A3 / AK) shown in Table 1 below is set. It was necessary to use a specially manufactured material.

  For this reason, the conventional column base anchor bolt 2 has a specially shaped deformed steel bar whose yield ratio (σy / σu) is smaller than the cross-sectional area ratio (A3 / AK) shown in Table 1. Therefore, there is a problem that the manufacturing cost is increased.

  Further, as shown in FIG. 4, the above-described conventional column base anchor bolt 2 is also formed by screw cutting in the same manner as the male screw portion 10 on the male screw portion 16 at the end opposite to the male screw portion 10. After all, the function of absorbing vibration energy in a large earthquake or the like cannot be exhibited. In order to solve this problem, there is a problem that the manufacturing cost is increased if the steel bar is made of a specially manufactured deformed steel bar as described above.

  Therefore, in view of the above problems, the present invention can reduce the shaking of a building during a small and medium-sized earthquake, and during a large earthquake, the central portion of the length extends with plastic deformation before the external thread breaks. It is an object of the present invention to provide an anchor bolt for a column base that can absorb energy and reduce manufacturing costs.

In order to solve the above problems, the anchor bolt for a column base according to the present invention is:
A threaded portion formed of a deformed steel bar having convex portions such as nodes and ribs on the peripheral surface and having a male screw having an outer diameter larger than the nominal diameter set between the height central portions of the convex portions in the diameter direction of the cross section Is formed at least at one end.

Moreover, the anchor bolt for a column base according to the present invention is:
The male screw is formed by a rolling method so that its outer diameter is larger than the set nominal diameter.

According to such an anchor bolt for a column base of the present invention,
A threaded portion formed of a deformed steel bar having convex portions such as nodes and ribs on the peripheral surface and having a male screw having an outer diameter larger than the nominal diameter set between the height central portions of the convex portions in the diameter direction of the cross section Is formed on at least one end,
During small and medium-sized earthquakes, the shaking of the building can be reduced, and in the case of a large earthquake, the center part of the length is stretched with plastic deformation before the external thread breaks, and the seismic energy can be absorbed and the manufacturing cost can be reduced. Can be reduced.

Moreover, according to the anchor bolt for the column base of the present invention,
The external thread is formed by a rolling method so that the outer diameter is larger than the set nominal diameter,
When the external diameter of the male screw part is larger than the external diameter of the male screw part of the conventional column base anchor bolt and a tensile force is applied, the male screw part extends with plastic deformation until it breaks. It is possible to absorb seismic energy during a large earthquake.

It is a side view which shows the anchor bolt 30 for column bases which concerns on one embodiment of this invention. FIG. 2 is a partially enlarged side view of an end portion on the male screw portion 32 side of the column base anchor bolt 30 shown in FIG. 1. FIG. 3 is a partially enlarged side view showing one step in the middle of forming the male thread portion 32 of the column base anchor bolt 30 shown in FIG. 1. It is a side view which shows the conventional column base structure 1. FIG. FIG. 5 is a partially enlarged side view of an end portion on the male screw portion 10 side of the column base anchor bolt 2 in FIG. 4. It is a strain-stress diagram showing the correlation between strain and stress when a tensile force is applied to the anchor bolt.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing the anchor bolt for column bases which concerns on this invention is demonstrated concretely based on drawing.
FIGS. 1 to 3 are views referred to for explaining a column base anchor bolt 30 according to an embodiment of the present invention.

  As shown in FIG. 1, the column base anchor bolt 30 according to the present embodiment has male screw portions 32 and 33 formed at both ends in the length direction. The column base anchor bolt 30 is formed with a shape as a deformed steel bar used as a material of the column base anchor bolt 30 on the outer periphery of the central portion 34 between the male screw portions 32 and 33 at both ends thereof. .

  That is, the outer periphery of the center portion 34 of the column base anchor bolt 30 is arranged so that the rib 36 formed along the length direction of the bolt and the length direction of the bolt are alternated with the rib 36 interposed therebetween. A plurality of knots 38 are formed in the circumferential direction by a length corresponding to a half circumference.

  As shown in FIG. 2, the external thread portion 32 of the column base anchor bolt 30 has an outer diameter D1 larger than the nominal diameter DK of the central portion 34. This nominal diameter DK has the same meaning as that used in the description of the conventional column base anchor bolt 2.

  The male thread portion 32 is shown in FIG. 3 by slightly scraping off the ribs 36 and the nodes 38 of the end portions of the deformed steel bar (not shown), which will be the material of the anchor bolts 30 for column bases, and the peripheral surface in other places. Thus, after forming the round bar shape part 40 which has the length substantially the same as the length of the external thread part 32, this round bar shape part 40 is formed by performing a thread rolling process.

  As shown in FIG. 2, the male thread portion 32 is formed by using the above-described thread rolling process, so that the top portion of the screw thread protrudes to the outside as much as the thread valley is formed to be recessed. And the outer diameter D1 is rolled so as to be larger than the nominal diameter DK of the central portion 34. Further, as shown in FIG. 1, the male screw portion 33 at the end opposite to the male screw portion 32 is formed in the same manner.

  When the column base anchor bolt 30 in which the male thread portions 32 and 33 are formed in this way is used, for example, in which the nominal diameter as a deformed steel bar as the material is D25, D29, D32, D35, Corresponding to each of these nominal diameters, male thread portions 32, 33 having nominal diameters M27, M30, M33, M36 as male thread portions can be formed. In such a case, the sectional area ratio (A3 / AK) is shown in Table 2 below.

  According to the present embodiment, the column base anchor bolt 30 has the ribs 36 as the deformed steel bars and the projections of the joints 38 formed on the outer periphery of the central portion 34 thereof. Because the amount of deformation is small even if a tensile load is applied to itself, the shaking of the building can be reduced, and in the event of a large earthquake, the central portion 34 extends with plastic deformation before the male screw portions 32, 33 break. Seismic energy can be absorbed.

  Further, according to the present embodiment, the upper limit of the allowable yield ratio (σy / σu) range of the deformed steel bar used as the material of the anchor bolt 30 for the column base can be increased for the following reasons. Therefore, since the seismic energy can be absorbed without forming the anchor bolt 30 for the column base from the specially shaped steel bar, the manufacturing cost of the anchor bolt 30 for the column base can be reduced. .

  That is, the column base anchor bolt 30 according to the present embodiment absorbs seismic energy when the central portion 34 is stretched with plastic deformation before the external thread portions 32 and 33 are broken in the event of a large earthquake or the like. In order that the yield ratio (σy / σu) and the effective area ratio (A3 / AK) must satisfy the relationship of the following formula 4, the anchor bolt 30 for the column base Can increase the numerical value of the effective area ratio (A3 / AK), and accordingly, the upper limit of the allowable yield ratio (σy / σu) range can be increased. .

  Therefore, according to the present embodiment, the yield ratio (σy / σu) is smaller than the effective area ratio (A3 / AK) in Table 2 described above for the deformed bar steel used as the material of the anchor bolt 30 for the column base. Since a material of a certain level is sufficient, it is possible to form the anchor bolt 30 for the column base from a commercially available general material without forming it from a specially manufactured deformed steel bar. Therefore, the manufacturing cost of the column base anchor bolt 30 can be reduced.

  In addition, although the male screw parts 32 and 33 were formed in the both ends of the column base anchor bolt 30 according to the present embodiment, only one of them may be formed.

  Further, as shown in FIG. 1, the column base anchor bolt 30 according to the present embodiment uses a deformed steel bar having a rib 36 and a protrusion of a node 38 formed on the outer periphery thereof. However, it is good also considering the deformed steel bar which has another convex part different from the rib 36 or the node 38 on an outer periphery as a raw material.

  In addition, the column base anchor bolt 30 according to the present embodiment is formed from deformed steel bars having nominal diameters D25, D29, D32, and D35 in Table 2 above. It may be formed from a deformed steel bar having a nominal diameter other than the diameter. In this case, the male screw portions 32 and 33 formed at both ends of the column base anchor bolt 30 are formed so as to have an outer diameter larger than the nominal diameter of the deformed steel bar used as the material. Needless to say.

  Further, in the column base anchor bolt 30 according to the present embodiment, the male screw portions 32 and 33 formed at both ends thereof are metric screws, but other types of screws other than the metric screw may be formed. Good. For example, an inch screw or the like may be formed.

2 Anchor bolt for column base 4 Column member 6 Column base 8 Beam concrete 10 Male thread part 12 Nut 14 Washer 15 Mortar part 16 Male thread part 18 Fixing plate 20 Nut 22 Central part 23 Node
24 Rib 30 Anchor bolt for column base 32,33 Male thread part 34 Center part 36 Rib 38 Section
40 Round bar shape part

Claims (2)

  A threaded portion formed of a deformed steel bar having convex portions such as nodes and ribs on the peripheral surface and having a male screw having an outer diameter larger than the nominal diameter set between the height central portions of the convex portions in the diameter direction of the cross section Is formed on at least one end of the column base anchor bolt.   2. The column base anchor bolt according to claim 1, wherein the male screw is formed by a rolling method such that an outer diameter thereof is larger than the set nominal diameter. 3.

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