JPS648146B2 - - Google Patents

Description

[Detailed description of the invention]

This invention uses a flat bar (flat steel) between the base material (column or beam) facing the steel structure and the base material.
This invention relates to a structure for attaching this flat bar to a predetermined position on a base material when reinforcing it with a tensile brace consisting of. There are two types of braces made of flat bars: a single-piece type that uses one flat bar, and a two-piece type that uses two flat bars. Conventionally, both of these types used a flat gusset plate as the base material. It is welded and attached to this gusset plate via a fastener. This type of bracing is generally used as the most economical and effective method for improving the seismic performance of steel structures, but in recent years there have been a number of accidents in which the mounting parts of the braces break during earthquakes. I'm awake. For this reason, the revision of the Building Standards Act, which came into effect in June 1981, required (1) consideration of the fracture situation at the brace attachment part, (2) confirmation of safety by calculation in the case where an eccentric moment occurs, and (3) ) It is requested that braces consisting of a single angle or reinforcing bar should not be used in large buildings as much as possible. Therefore, when considering the conventional braces mentioned above, in the case of tension braces in which a flat bar is attached to the base material using a gusset plate, an eccentric moment (M) occurs at the joint due to the structure, as shown in Figure 4. Therefore, the stress due to the eccentric moment (M) acts together with the tensile force, and the flat bar 5 and the gusset plate 8 are also affected by the eccentric moment (M).
It is thought that it broke at the joint, as it has a very weak shape. Furthermore, if the braces in the conventional structure were designed with sufficient consideration for eccentric moments, the overall size would increase, resulting in considerable loss of steel material. 2 more
The material clamping type brace is advantageous because eccentric moments are less likely to occur compared to the single material type, but on the other hand, the work is complicated because it is necessary to attach two flat bars to the gusset plate to sandwich it. There were flaws. This invention was made in view of the above points, and when one flat bar is used as a tension brace, a unique channel member is used in place of the conventional gusset plate, and the cross-sectional center of gravity of the flat bar and this channel member is By aligning the axes to minimize the eccentric moment, the aim is to achieve safety standard strength and reduce the thickness of the material. Embodiments of the present invention will be described below based on the drawings. In Figures 1 to 3, 1 is a column of a steel structure, 2 is a beam stretched between these columns 1 and 1, and a channel member is attached at the corner where column 1 and beam 2 are connected. 3 is fixed by welding. The web 3a of the channel member 3 is provided with an insertion hole 4 for a stopper, and the flat bar 5 has an insertion hole 6 and an insertion hole 4 for a stopper provided at both ends thereof.
It is attached to the inner surface of the web 3a of the channel member 3 by a fastener 7, such as a stud, bolt, or nut, which passes through the channel member 3. By the way, the channel member 3 has a U-shaped cross section as shown in FIG. 2, and its inner corner portions are thickly reinforced in an arc shape, and flanges 3b, 3b protrude at right angles from the web 3a and both ends thereof. The flat bar 4 is a bar-shaped steel material with a rectangular cross section and is usually a JIS standard product. Moreover, the channel member 3 is
In the cross section of the flat bar 5 at the stop 7 penetration position, the center of gravity axis Y3 parallel to the web 3a of the channel member ₃ and the center axis Y5 of the flat bar ₅ parallel to the web 3a are configured so as to substantially coincide with each other. . Here, to explain the structure of the channel member 3, the center of gravity axis of the channel member 3 is shown in FIG.
The distance e ₃ from the Y-Y line of Y ₃ is C = web 3a
length, f = length of flange 3b, t = web 3
a and the thickness of the flange 3b, SY=first moment of area with respect to the Y-Y line, R=diameter of the insertion holes 4 and 6 for the stopper 7, h=width of the flat top 5, A=
Assuming the cross-sectional area of the channel member 3, A=t(C+2f-R) SY=(C-R)×(f+t)×(f+t)/2 −(C-R-2t)×f×f/2 =( C-R) (f+t) ² /2-(C-R-2t)f ² /
2 SY=A×e ₃ , so e ₃ =SY/A= (C-R)(f+t) ² -(C-R-2t)f ₂ /2t(C-
R+2f)=f+t(C-R) ^-2f2 /2(C-R+2f). Further, the distance e ₅ of the center of gravity axis Y ₅ of the flat bar 5 from the Y-Y line is e ₅ =fh/2, and the center of gravity axes Y ₃ and Y 5 of the channel member 3 and the flat bar ₅ are aligned. For example, since the eccentric moment (M) shown in FIG. 4 does not occur, the length f of the flange 3b of the channel member 3 may be designed to meet the following conditions. That is, from e ₃ = e ₅ , f+t(C-R) ^-2f2 /2(C-R+2f)=f-h/
2 ∴t(C-R)-2f ² /2(C-R+2f)+h/2=0 ∴2f ₂ -2hf-(C-R)(h+t)=0, so

Design so that [Formula] is satisfied. Next, a specific example of a channel member that satisfies the above conditions for a predetermined flat bar will be shown.

【table】

[Table] In addition, in the specific example of the channel member mentioned above, the center of gravity axes of the flat bar and the channel member in the effective cross section (the cross section at the stopper penetration position) are completely aligned, but the center of gravity axes of both may be slightly shifted. Since the eccentric moment is also small, it is good if the stress due to the eccentric moment and tensile force is less than the allowable stress of the channel member and the flat bar. As explained above, the tensile brace of this invention is
The channel member consists of a channel member with a U-shaped cross section whose end is attached to the base material of the reinforcing steel structure, and a flat bar as a tension brace that is attached with a stopper that penetrates the inner surface of the web of the channel member. In the cross section of the stopper penetration position, the center of gravity axis of the channel member parallel to the web and the center of gravity axis of the flat bar are configured so as to substantially coincide with each other to prevent eccentric moment from acting on the channel member and the flat bar as much as possible. Therefore, the channel member and the flat bar only have to bear the tensile force of the base material of the steel structure, making it easier to achieve the safety standard strength, and also reducing the amount of steel used, which allows the material to be thinner. In addition, the center of gravity axis of the channel member and flat bar is set to the cross section of the stopper penetration position because the cross-sectional area at the stopper position is the smallest and the strength is the minimum, so the strength at the stopper position cannot exceed the safety standard strength. Furthermore, in the above embodiment, the inner corner portion of the channel member was reinforced with a thick wall so that the center of gravity axis could be determined as a cross section of the entire channel member in which the web and flange were integrated. This is to do so.

[Brief explanation of the drawing]

Fig. 1 is an overall front view showing an embodiment of the present invention, Fig. 2 is an enlarged view of the mounting part of the channel member and flat bar, and Fig. 3 is a sectional view of the stop mounting part of the channel member and flat bar, and a diagram of the eccentric moment. FIG. 4 is a cross-sectional view of the attachment portion of a conventional single-piece tensile brace between a gazette plate and a flat bar, and an explanatory diagram showing the relationship in which an eccentric moment occurs. 1... Column, 2... Beam, 3... Channel member,
3a...web, 3b...flange, 4,6...
Insertion hole, 5... Flat bar, 7... Stop, 8...
...gusset plate.

Claims (1)

[Claims] 1 Consisting of a channel member with a U-shaped cross section whose end is attached to the base material of a steel structure, and a flat bar as a tension brace that is attached with a stopper that penetrates the inner surface of the web of the channel member, the channel member A tensile brace for a steel structure, characterized in that the member is constructed such that the center axis of the channel member parallel to the web and the center axis of the flat bar substantially coincide with each other in a cross section at a position where the stopper passes through the member.