JPH0512501U - Pillar hardware - Google Patents

Abstract

(57) [Summary] [Purpose] No matter what high strength material is used for the pillar,
Make sure that the anchor bolts of the column bases and the concrete foundations do not receive more momentum than expected in the design. [Structure] The upper part is welded to the lower end of the pillar 1, and the bottom plate portion 23
Is a column pedestal 2 fixed by anchor bolts 4 projecting from the base portion 3, and has a flange portion 21 rising from the bottom plate portion 23 upward in a shape corresponding to the column member 1,
A cross-section defective portion 22 is formed in the vicinity of the center of the flange portion, and the yield strength of the cross-sectional defective portion 22 is made equal to the designed yield strength of the pillar material 1.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a metal fitting used for a column base in a building having a steel structure or a steel reinforced concrete structure.

[0002]

[Prior Art]

 Usually, the column base in a building of steel structure or steel reinforced concrete structure is fixed to an underground beam or foundation concrete through a metal member called a column base metal member. FIG. 6 shows an example of a typical fixing structure disclosed in Japanese Patent Application Laid-Open No. 2-256741 as a conventional technique. A column base metal member 2 is welded to a lower end portion of a column 1 and an anchor bolt 4 is used to dig it into the ground. It is tightly connected to the beam 3, and after the column is erected, the filling mortar 5 is placed over the entire lower surface of the column base metal 2.

Although this structure is effective for fixing the column base, it is not sufficiently compatible with the recent design method that assumes the limit state of the structure, that is, the so-called “limit state design method”. That is, various materials such as cold rolled material, welded assembly material, and shaped steel are currently used as column members, and all of these materials are the lower limit of the design allowable stress level referred to in the Building Standards Act, the so-called “F value”. Although there is a considerable difference in the actual mechanical properties, the actual proof stress has an F-value of around 10 kgf / mm ² May exceed.

When the column base is regarded as a pin in the limit state of the structure such as an extremely large earthquake and the strength level of the column material is too high, the deformation of the column material falls within the elastic range. The result is that an excessive load will be transmitted as it is to the column base where there is no room in the design, which may cause a situation such as separation between the column base and foundation concrete, yielding of anchor bolts, or collapse of concrete. ..

FIG. 3 shows a moment distribution diagram acting on the steel column / beam structure. In the usual design, the maximum value of the moment applied to the column material occurs at the column base. As shown in Fig. 6, the momentum of ordinary pillar pedestals inevitably has a large thickness compared to the flange thickness of the pillar material, and the bending moment acting on the pillar base and the rotation angle of the pillar base are As for the relationship, as shown in Fig. 4, stable characteristics within the elastic range can be obtained. However, assuming a case where an excessive horizontal force such as a large earthquake acts on the structure and the column base yields due to the design, the total plastic moment of the column is composed of the column base metal and anchor bolts. If the total plastic moment of the column base is exceeded, the yield phenomenon of either the column base metal or the anchor bolt will occur prior to the column yield. Regardless of whether the column pedestal or anchor bolt yields, the relationship between the moment generated in the column pedestal and the rotation angle is a slip type as shown in Fig. 5, and the energy absorption characteristics deteriorate and the moment transmission capability also decreases. There is a problem that the performance as a structure deteriorates.

As a means for avoiding such a drawback of the column base, according to Japanese Patent Laid-Open No. 1-97740, a position where the column action moment due to the horizontal force is minimized, that is, the height to the beam is about 1/2 It is proposed to place the column base at a height of ~ 1/3. FIG. 7 is a conceptual diagram and bending moment diagram of the entire building, and FIG. 8 is an enlarged view of part A of FIG. According to this idea, the structure of the column base becomes rational, but the dimension of the column on the first floor becomes large, which is a problem in terms of aesthetics, and it is not practical and practical as a building.

[0007]

[Problems to be solved by the device]

 The present invention eliminates the above-mentioned drawbacks, and the position of the column base is set to the normal ground height, and even if any high strength material is used for the column, the anchor bolt of the column base or the foundation concrete is The objective is to provide a structure for the column base that does not apply a moment more than expected in the design.

[0008]

[Means for Solving the Problems]

 The present invention relates to a pillar pedestal in which an upper surface portion is welded to a lower end of a pillar material and a bottom plate portion is fixed by anchor bolts projecting from a foundation portion, and the pillar material is upward from a bottom plate portion in contact with the foundation portion. It is characterized in that it has a flange portion that rises in a shape, and a cross-section defect portion is formed near the center of this flange portion.

[0009]

[Work]

 According to the present invention, a cross-section defect is formed near the center of the flange in the column base metal, and plastic deformation is generated in this part where stable hysteresis characteristics including recovery can be expected, and any high-grade column is obtained. Even if a material is used, the anchor bolts of the column base and the concrete concrete parts are prevented from exerting a moment more than expected in the design.

[0010]

【Example】

 FIG. 1 shows an embodiment of the present invention. Reference numeral 1 is a pillar, 2 is a column foot metal fitting, 3 is an underground beam on which these are erected, and 4 is an anchor bolt. 5 is a filling mortar that is filled in the middle between the column base metal and the underground beam. In the actual construction, place the level adjustment mortar or leveling block in this part and fill the mortar after the construction is completed. Although weirs and the like are also used, illustration of these is omitted.

As is clear from comparison with the conventional one as shown in FIG. 6, this pillar pedestal has a shape corresponding to the pillar material in the middle of standing up from the bottom plate portion 23 and connecting to the pillar material 1. That is, if the pillar material is a rectangular steel pipe, it is characterized by having a flange portion 21 of substantially the same cross-section as that of this and forming a groove portion 22 near the center thereof. The groove 22 is an intentionally formed cross-section defect, and the position where plastic deformation first occurs for the column base metal is specified in this portion when an excessive external force is applied. In order to make the generation position more reliable, a flange part 21 is formed that sandwiches the groove part 22 and becomes a thick and healthy part at the top and bottom, through which the upper and lower pillar materials 1 and the bottom plate part 23 of the metal object are connected. To be done. 24 is a welded joint between the column base metal 2 and the column 1.

The shape of the groove 22 should not cause excessive stress concentration such that it is deformed by normal stress, and a U-shape having no sharp corner is preferable. In order to plastically deform the groove part of the column base metal piece in the entire column-foundation system, the effective sectional area A _e of the column base metal piece in the groove part must satisfy the following equation. F · A _c = σ _y · 1 / α · A _e・ ・ ・ Equation (1) where F is the F value that defines the material of the entire system, A _{c is} the cross-sectional area of the column portion, and σ _{y is the} column base. Yield point stress of the metal, α: Stress concentration factor determined by the shape of the groove, (1) The left side of the formula is the design strength of the column material, and the right side is the proof stress of the cross-section missing part formed on the column base metal flange part. .

Since the stress concentration coefficient α in the equation (1) is a value having a wide range according to experience, the calculation result of the effective sectional area A _e of the column base metal member in the groove portion is also allowed to vary by about ± 10%. However, if the effective area A _e is set to be much larger than the value obtained by Eq. (1), the probability that the first plastic deformation will occur at the defective section will decrease, and the significance of forming the defective section will be significant. If the value is smaller than the value obtained by the equation (1), the possibility that plastic deformation will occur due to the normal horizontal force is increased, which is not preferable.

Since such a cross-section defective portion is provided in the flange portion of the column base metal member, it is a portion only made of metal as a material, and is a portion where stable hysteresis characteristics including recovery can be expected. It is an effective place to cause plastic deformation. As the material of the column base metal, forged steel or cast steel is advantageous because the variation of σ _y is small and the weldability is good.

As a concrete design example, the column material is a square steel pipe made of cold rolled material with a side D = 350 mm and a wall thickness of 12 mm, and the designed F value is 33 kg / mm ² , Is made of cast steel, σ _y = 30-35 kg / mm ² , flange length H = 175 mm, wall thickness 16 mm, groove width 8 mm, depth 4 mm U-shaped, in a load test with a full-scale test piece Plastic deformation occurred in the groove as expected.

In the above formula (1), the shape of the cross-section loss is not limited to the U-shaped groove as long as the shape gives the equivalent effective area. An appropriate number of small holes may be provided in the. FIG. 2 shows an example in which holes are provided. Reference numeral 25 is a hole provided in the flange portion 21 as a cross-section defective portion. The shape of the hole may be a circle, an ellipse, or an ellipse.

Further, when the load condition in the horizontal direction is different depending on the position of the pillar in the building, such grooves or holes may not be made uniform by the surface of the flange but may be changed by the direction of the surface. .. Further, when a hole is provided, it is possible to fill the hole with bolts, pins, concrete or the like from the viewpoint of ensuring the buckling strength and provide a mechanism capable of transmitting only the compressive force.

When a regular section steel pipe or an H-section steel having a circular cross section is used as the column in addition to the square section steel pipe, if the flange portion of the column base metal fitting also has a shape corresponding to these, there is no relation between the formula (1). It is the same.

[0019]

[Effect of the device]

 According to the present invention, no matter what high-strength material is used for the column, the anchor bolts and concrete parts of the column pedestal do not exert a moment more than expected in the design, and the plastic deformation has stable hysteresis characteristics. Since it occurs in existing metal parts, a safe building structure can be realized even in the event of a large earthquake.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of an embodiment of the present invention.

FIG. 2 is a side view showing the configuration of another embodiment of the present invention.

FIG. 3 is a moment distribution diagram of a structure according to the present invention.

FIG. 4 is a graph showing a relationship between a moment and a rotation angle in a column base.

FIG. 5 is a graph showing a relationship between a moment and a rotation angle in a column base.

FIG. 6 is a side view showing an outline of a conventional example.

FIG. 7 is a conceptual diagram and a bending moment diagram showing an outline of another conventional example.

FIG. 8 is an enlarged side view of portion A of FIG.

[Explanation of symbols]

 1 pillar 2 pillar leg hardware 21 flange 22 groove 3 underground beam 4 anchor bolt 5 filled concrete

Claims (3)

[Scope of utility model registration request] 1. A pillar pedestal having an upper portion welded to a lower end of a pillar member and a bottom plate portion fixed by anchor bolts protruding from a base portion, the flange rising up from the bottom plate portion in a shape corresponding to the pillar member. A column pedestal having a portion, a cross-section defective portion being formed in the vicinity of the center of the flange portion, and the proof stress of the cross-sectional defective portion being equal to the design yield strength of the column member. 2. The pillar pedestal according to claim 1, wherein the cross-section defective portion is formed by providing a single or a plurality of U-shaped grooves on the surface of the flange portion or by providing a single or a plurality of holes in the flange portion. 3. The column base metal fitting according to claim 1 or 2, wherein the shape of the cross-section defective portion is different for each flange surface.