JPS61130536A - Iron pillar leg - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steel column base in which a steel column of a steel frame building is fixed to foundation concrete via a base plate F.

[Conventional technology]

Conventionally, steel frame column bases for buildings have been constructed using a base plate 1 in which a steel plate is welded to the lower end of the steel frame column 2, as shown in Figure 7 (diagonal lines indicating the cross section of the foundation concrete are omitted. The same applies to the diagram of the pond). Exposed column bases that are easy to construct are used, which are fastened to anchor bolts 3 fixed in foundation concrete 4. However, this column base suffered from large rotational deformation of the column base in response to external force (bending moment generated on the column base), which resulted in the defect that the upper frame of the Mi-dyed fabric had to bear a large amount of stress. .

Therefore, recently, as an improved construction method for this column base, the anchor bolt 3 is fixed to the foundation concrete 4 at the lowermost part 77 of the anchor bolt 3, etc., as shown in FIG. Tsumugi % above b 3 a
Axial direction unrestrained 55 which eliminates adhesion with concrete 4
3C Set the base plate 1 on the anchor bolt 3 and the foundation concrete 4, tighten the base plate with nuts 5, and tighten the anchor bolt 3.
Steel column bases 6 with tension applied to them have come to be used1.

[Problem that the invention seeks to solve, α]

However, although the fixity (rotational rigidity) of this steel column base increases to some extent and the stress borne by the upper frame of the building can be reduced to some extent, it has the following drawbacks as shown in FIG. 9.

(1) When an external force (bending force 1M) is applied to the column 51, the base plate 1 deforms locally and in a complicated manner.

(2) The value of the tension to be introduced into the anchor bolt 3 has not been clarified, and the value of this tension varies for each building, and at the same time, the method for evaluating performance (fixation degree) has not been determined. The conventional improved steel column base is as described above (]
) Due to (2), not only is it not possible to obtain a high degree of fixation that takes full advantage of the performance of the anchor bolt, but it is also difficult to accurately grasp the degree of fixation when designing a building. ! In terms of ensuring the safety of dyed products, there remains great anxiety.6 The present invention is one of the first steps to solve these problems. We provide steel column bases with a clear evaluation of the degree of fixation, and are rated 11! The purpose is to ensure the safety of dyed products.

[Means for solving problems]

As shown in Fig. 1, the steel frame column base of the present invention has the following major points. It is lJt.

(a) The base plate 1 has a protruding portion 1a that connects with the steel column 2, a slope from the base 1b to the end 1c to make the base 1b medium and high, and is made of a highly rigid cast or plated material that can be welded or bolted to the column 2. (b) The anchor bolt 7 is anchored to the foundation concrete 4 using forged column base hardware in an unrestrained state where the shaft portion 7a of the anchor bolt 7 and the unrestrained portion 7b are free from adhesion to the concrete. , using an anchor frame or anchor plate 8.

(c,) Foundation concrete 41 of base plate 1
To fix the base plate to the anchor bolt 7, attach the yield value of 0.15 to 1 to the anchor bolt 7.
．． Twice the tension was introduced.

[For production]

In the steel frame column base according to the present invention, since the base plate 1 has very high rigidity, its deformation can be extremely reduced, and the rotational deformation of the column base caused by the base plate 1 can be reduced to almost zero. In addition, by using a highly rigid base plate 1 and at the same time introducing a predetermined tension to the anchor bolts 7, the mechanical mechanism of the column base can be simplified, and the rotational rigidity of the column base can be evaluated accurately. This is what I did.

According to experiments, the rotational deformation behavior of the steel column base according to the present invention in response to external force (bending moment) has a simplified shape as shown by the solid line in FIG. 2 (al).

In other words, the rotational rigidity (M/θ) of the column base is
In (b), the bottom surface 1e of the base plate 1 at the tension side anchor bolt position and the top surface 4a of the foundation concrete are separated from each other up to point A (FIG. 2(a)), and the point B (second point) where the tension side anchor bolt 7 yields. It changes in three categories: up to (a) in Figure (a) and after that.

The rotational rigidity indicated by dashed lines in Figure 2 (aJ) is the theoretical value of rotational rigidity when the base plate 1 is a completely rigid body and no tension is introduced into the anchor bolt 7, and geometrically (1) It is given by Eq.

Ko: Rotational rigidity of the column base when no tension is introduced into the anchor bolt (Lm/rad) E: Young's modulus of the anchor bolt (L/cm') AB: Total cross-sectional area of the tension-side anchor bolt group (cm') ! : Distance between anchor bolts R (a
m) L: Anchor bolt effective embedment depth (am 1) In the present invention, the eave rigidity of the steel column base between 0 and A is based on the same theory as that of tensile joints, as shown in equation (2), where tension is applied to the anchor bolt. (1+α) times as much as when not introducing.

In this case, α is the constant ratio of the anchor bolt to the foundation concrete and is given by equation (3).

K; (1+α)Ko ・・・・・・・・・・・・ (
2) Effective cross-sectional area of Ac two foundation concrete (Cl3)A
b: Cross-sectional area of the anchor bolt (cs+”) n: The value of the Young's modulus ratio (1+α) between the anchor bolt and the foundation concrete is approximately 5 to 6 for the commonly used anchor bolt 7 such as 5S41 material, which is 0. - A, significantly higher rotational rigidity can be obtained by introducing tension to the anchor bolt 7. However, between A and B, the bottom surface of the base plate 1 touches the top surface of the foundation concrete 4a.
When the anchor bolts are separated further apart, the anchor bolt changes to a state of simple tension, which is the same as when no tension is introduced, so the rotational rigidity becomes the same value as 0 in equation (1), and is less than the value of 0 to AIIIT.

Here, in the construction industry, the allowable proof stress of a column base is generally determined by the yield value of the entire column base, so the allowable proof stress of the column base of the present invention is shown in Fig. 2 (My (the bending angle at which the anchor bolt 7 yields) Therefore, if the allowable strength of the column base is My and the separation moment Ms is less than My, the rotational stiffness of the column base must be evaluated as It becomes difficult to secure K.

On the other hand, in order to guarantee a high rotational rigidity K, the allowable strength of the column base must be evaluated by lowering it from MP to Ms, resulting in a strength disadvantage.

Therefore, in order to guarantee a high rotational rigidity K and a high allowable strength My of the main column base, Ms is set to M.
It may be set to the same value as y.

By the way, the separation force Ms is related to the value of the tension introduced into the anchor bolt, and is given by equation (4).

Ms Gaku To・l・・・・・・・・・・・・・
... (4) To: 7 ton force - bolt introduction tension (a
(L/c+*”) 1: Distance between anchor bolts 1% Cc) Also, the allowable strength of the column base is given by formula (5).

M, : T, -p = σy-AB-1 ・
・・・・・・・・・ (5) Ty: 7 Anchor bolt yield tensile force (t/cm') σy: Anchor bolt yield stress (L/Cm'') Therefore, in order to set Ms=My, T0= 77=σF'AB, and this is the method to maximize the performance of the anchor bolt both in terms of allowable strength and in terms of strength.

Therefore, basically, the effect of applying tension to the anchor bolt occurs between 0 and 1 times the anchor bolt yield stress.

However, it has been known that the tension introduced into the 77 car bolt is released by drying shrinkage and creep of the concrete.

The results of the anchor bolt tension unloading test conducted by the inventors are shown in FIG. 10.

The test shown in Figure 10 investigated changes in anchor bolt tension over time (the ratio of the tension after a predetermined time of 11!! to the initially introduced tension).
An actual steel frame, as shown in Figure 11, consisting of anchor bolts! The test was carried out using a specimen corresponding to a steel column base of a building (specimen No. 015 in Table 1 below).

From this disaster, it was discovered that there is a certain regularity in the stress release of the Ajiker bolt when the introduced tension of the anchor bolt is around σy. That is, base 1i! which has been used for more than 4 weeks after pouring in normal use! When tension is increased in concrete anchor bolts, the stress release stabilizes in about 4 days and reaches about 20%. This corresponds well with the amount of tightening of the anchor bolts after the above-mentioned 1 hour has elapsed after the foundation concrete is cast, which the inventors usually experience.

Therefore, from the above experimental results, the anchor bolt has σy of 2
If an introduction tension of 1.2σy, which is an increase of 0%, is applied, the value will eventually become 1, Ofy, after aging, which is ideal.

Therefore, in the present invention, 1.2σy was set as the upper limit of the introduced tension.

However, according to the ``Structural Calculation Guidelines and Explanations'' published by the Japan Building Center on February 1, 1981, from the standpoint of maintaining a high level of safety, the tension introduced into anchor bolts (allowable stress) is set according to JIs standards. When using anchor bolts made of other materials, 1.1σy is set as the upper limit allowable value.

Therefore, as long as the upper limit tolerance of the above guideline is not revised, in actual construction, it is desirable to apply an introductory tension of up to 1.1σy to the anchor bolt in order to efficiently and safely demonstrate the performance of the anchor bolt.

Further, the lower limit value of the anchor bolt introduction tension according to the present invention was set to 0.15 fy for the following reason.

In other words, it is clear from numerous experimental results that when the tension introduced into the anchor bolt is 0, the column base assumes a slip type as shown in Figure 3, and the bending moment generated in the column base changes in positive and negative directions. By the way, even if a large bending moment does not occur in the column base, the column base undergoes extensive rotational deformation. It is a well-known fact that this can have a negative impact on the superstructure.

In order to make the column base have good performance (spindle-shaped restoring force characteristics) as shown in FIG. 4, it is necessary to prevent the anchor bolt from completely releasing the introduced tension.

1, that is, the tension introduced into the anchor bolt is between 〇-1 and 0.
．． At a low level of 2σy, the stress relief of the anchor bolt is approximately 0.05σ above the drying shrinkage of the concrete.
y1 Concrete creep is approximately 0.02σ
y, and a total stress release of 0.07σy was found to occur. Therefore, if the safety factor is set to about 2 and the introduced tension (stress degree) is set to a minimum of 0.15σY, the introduced tension of the anchor bolt will not be completely released over time (0.08σy will remain), and the performance of the column base will deteriorate. Good performance shown in FIG. 4 can be ensured.

Therefore, the present invention provides an introduction tension (stress degree) of the anchor bolt.
The lower limit of is set to 0815σy.

〔Example〕

The rotational rigidity of the steel column base having the dimensions shown in FIGS. 11(a) and 11(b) and Table 1 was measured, and the results are also shown in Table 1.

In Table 1, 0 is the rotational stiffness of the conventional steel column base when no tension is introduced into the anchor bolt, and K is the rotational rigidity of the steel column base according to the present invention when tension is introduced into the anchor bolt. As can be seen from Table 1, the rotational rigidity of the steel column base according to the present invention is extremely high, being 5 to 6 times the rotational rigidity of the conventional one.

In addition, in the base plate 1 of the present invention, the reason why the part 1& that connects with the steel column is made to protrude is to prevent distortion during welding with the base plate 1d from being applied to the bottom surface 1d of the base plate.

Furthermore, the reason why the slope is provided from the base 1b to the end n1e to make the base mid-height is that the effect of the tension introduced by the anchor bolt 7 is increased by 4 mm over the entire area of the rising foundation concrete 4, as shown by the arrow in FIG. It is for the purpose of

However, as a base plate, for example,
-47963, Special Publication No. 52-13642, 433
The effect of the present invention can be fully exhibited by using the column base hardware described in each publication such as No. 30 and Japanese Patent Publication No. 56-30425.

1 The above-described steel frame column base according to the present invention is shown in Fig. 1.5 in which the column and base plate are joined by welding, but as shown in Fig. 6, they can also be joined by bolt connection. .

〔Effect of the invention〕

As described above, the steel column base of the present invention has a tension (stress degree) introduced into the anchor bolt of 0°15 to 1.2σy.
Since the value is set to , the performance of 7 anchor bolts is allowed.
It is possible to exert maximum force in terms of torque, and the rotational rigidity of the column base can also be highly evaluated.

In addition, good performance (spindle-shaped restoring force characteristics) can be ensured against repeated positive and negative stresses (bending moments generated in column bases) such as during earthquakes.

Furthermore, by simplifying the mechanical mechanism of the column base, the performance of the column base (rotational rigidity)
(and yield strength) can be accurately determined, increasing the safety of buildings.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a steel column base showing an embodiment of the present invention;
Figure tA2 (,) is a diagram showing the behavior of rotational deformation of the steel column base according to the present invention in response to external force, Figure fJS2 (b) is also a figure of Mata 2 showing rotational deformation, and Figure 3 is a diagram showing the behavior of rotational deformation of the steel column base according to the present invention. Figure 4 is a restoring force characteristic diagram of a steel column base according to the present invention, Figure 5 is an enlarged view of the base plate portion of a steel column base according to the present invention, and Figure 6 is an enlarged view of the base plate portion of a steel column base according to the present invention. 7 is a cross-sectional view showing an example of a conventional steel column base, FIG. 8 is a cross-sectional view of a conventional steel column base in which tension is introduced into the anchor bolt, and FIG. 9 is a cross-sectional view showing an example of a conventional steel column base. a)
, (b) is a front sectional view and a side sectional view showing the state when an external force (bending moment) is applied to a conventional steel column base in which tension is introduced into the anchor bolt, and Fig. 10 is a change in the tension of the anchor bolt over time. A diagram showing FIG. 11(a),
(b) is a plan view and a side sectional view of a specimen in an example of the present invention. 1: Base plate, 1a: Projection, 1b: Base, 1c: End, 2: Steel column, 4: Foundation concrete, 6: Steel column base, 7: 7-1 car bolt, 7a: Chapter, 7b: Unrestrained Part, 8: Anchor 7 frame (anchor plate) agent patent attorney Hon.
Takashi Ma 1st leap 2nd figure '4.5 Figure 7th 1st leap (a) (b) F/
/hidden (b)

Claims (1)

[Claims] The steel column is joined by welding or bolts to a cast or forged column base hardware in which the part to be connected to the steel column protrudes, and the thickness of the protruding part gradually changes from the base to the end. The column base metal fittings are fixed to the anchor bolts buried in the foundation concrete without being constrained in the axial direction, and the yield point is 0.
A steel column pedestal characterized by being tightened by applying a tensile force of 15 to 1.2 times.