JP7495309B2 - Ladder-type load-bearing wall structure and portal structure - Google Patents

Description

The present invention relates to ladder-type bearing wall structures and portal structures.

For example, in a steel-framed house, columns made of square steel pipes and beams made of shaped steel such as H-shaped steel form the frame structure as the primary members, and a certain level of earthquake resistance is ensured by arranging various types of bearing walls, including brace-embedded bearing walls, in a balanced manner relative to this frame structure.

Because each structural surface of a house with a frame structure requires a required number of bearing walls, design freedom tends to be low, and therefore construction on small or irregularly shaped sites is often difficult. For this reason, a method is applied in which narrow bearing walls are placed in appropriate locations within the structural surface of the frame structure. Here, a narrow bearing wall refers to a bearing wall that is 0.5P or 0.25P wide, as opposed to the usual 1P-wide (P indicates the module, and can be set arbitrarily between 800mm and 1100mm, for example 910mm wide, depending on the module design specifications) bearing wall.

As one form of the narrow shear wall described above, a ladder-type shear wall frame has been proposed that can form a shear wall with excellent energy absorption during an earthquake. Specifically, this ladder-type shear wall frame has two parallel metallic vertical members and a number of horizontal members that are spaced apart between the two vertical members in the longitudinal direction of the vertical members and connected to each of the vertical members. In this ladder-type shear wall frame, the horizontal members have connecting parts made of two metallic web plates and metallic dampers that are arranged between the two connecting parts and connected to each connecting part, and the height of the web plates increases in a fan-shaped manner from the connecting end with the dampers toward the connecting end with the vertical members (see, for example, Patent Document 1).

JP 2019-157518 A

When a ladder-type bearing wall structure having two vertical members, such as the ladder-type bearing wall structure described in Patent Document 1, is incorporated into the vertical structural plane of a building, the cross-sectional force due to the axial force and bending moment generated in one vertical member (hereinafter referred to as the combined cross-sectional force) may be larger than that of the other vertical member, and it may become necessary to increase the cross-section of the steel material (such as a square steel pipe) that constitutes that one vertical member.

The present invention was made in consideration of the above problems, and aims to provide a ladder-type bearing wall frame with two vertical members that can solve the problem of having to increase the cross section of the vertical members due to a relatively large composite sectional force occurring in one of the vertical members, and a portal frame equipped with this ladder-type bearing wall frame.

In order to achieve the above object, one aspect of the ladder-type bearing wall structure according to the present invention is as follows:
Two parallel metal vertical members;
A ladder-type bearing wall structure having a plurality of horizontal members disposed at intervals between the two vertical members in the longitudinal direction of the vertical members and connected to each of the vertical members,
the cross member has a metal tie and a metal damper connected to the tie;
The present invention is characterized in that one end of the damper is connected to one of the vertical members, and one end of the connecting member is connected to the other vertical member.

According to this embodiment, the horizontal member has one metal connecting member and one metal damper, so that when the ladder-type bearing wall frame is incorporated into the vertical structural plane of a building, for example, by connecting the damper to one vertical member where the axial force acting is relatively large, and connecting the connecting member to the other vertical member, the bending moment generated in one vertical member can be reduced and the composite section force can be reduced. This makes it possible to avoid increasing the cross section of one vertical member. In other words, in the horizontal member of the ladder-type bearing wall frame described in Patent Document 1, since there are connecting members (connecting parts in Patent Document 1) on the left and right of the damper, the damper is arranged in the center of the horizontal member, whereas the horizontal member of this embodiment is formed of one damper and one connecting member, so the damper is arranged eccentrically on the side of one vertical member, which is a major difference between the two. Here, it is preferable for the connecting material to have rigidity, and this allows the shear force caused by the horizontal force during an earthquake (or a major earthquake) to be concentrated on the dampers that make up the horizontal material while increasing the stiffening effect of the vertical material (columns).

The vertical members can be made of square steel pipes, etc., and the connecting members that make up the horizontal members can be made of steel plates, etc. Furthermore, various types of dampers can be used, including shaped steel materials such as channel steel and H-shaped steel, as well as viscoelastic dampers, viscous dampers, and elastoplastic dampers.

In another aspect of the ladder-type bearing wall structure according to the present invention, the connecting member has a web plate, and the wide surface of the web plate is arranged parallel to the structural surface formed by the two vertical members,
The web plate is characterized in that the height of the web plate increases in a divergent manner from the connection end with the damper toward the connection end with the vertical member.

According to this embodiment, the connecting member connected to one end of the damper is formed of a web plate whose wide surface increases in a divergent manner from the damper side to the vertical member side, so that the stiffening effect of the column is further enhanced, and the shear force caused by the horizontal force during an earthquake can be more concentratedly borne by the horizontal member damper. In particular, in this embodiment, the bending rigidity of the connection between the vertical member and the horizontal member, where the bending moment is dominant, and its surroundings are increased by the divergent region of the metal (particularly steel) web plate that forms the horizontal member, so that the bending strength of the connection and its surroundings is improved, and bending deformation of the vertical member can be effectively suppressed. Here, examples of the form in which the "height of the web plate increases in a divergent manner" include a form in which both the upper and lower sides of the wide surface of the web plate are trapezoidal and tapered, and a form in which the upper and lower sides of the wide surface of the web plate have a curved linear shape, and the curved linear shape approaches the longitudinal direction of the vertical member toward the connection end with the vertical member.

In this embodiment, the increased bending rigidity of the vertical members also means that the flared region of the web plate expands the rigidity area of the vertical members. This makes it possible to suppress out-of-plane deformation of the web plate due to bending, and allows the shear force caused by horizontal forces during a major earthquake to be concentrated on the damper without damaging the web plate. This makes it possible to effectively absorb earthquake energy, especially during major earthquakes, while shearing the damper, without causing bending yield or shear yield of the web plate that forms the vertical members and horizontal members. As a result, it is possible to impart high earthquake resistance to the vertical structural plane of a building in which this ladder-type bearing wall frame is incorporated, especially during major earthquakes, without damaging the constituent members of the ladder-type bearing wall frame.

In another aspect of the ladder-type bearing wall structure according to the present invention, the connecting material is characterized by having the web plate and flange plates connected to the upper and lower ends of the web plate.

In this embodiment, by connecting flange plates to the top and bottom of the web plate, the bending rigidity and shear rigidity of the connecting material are increased, and the shear force caused by the horizontal force during a major earthquake can be more concentrated on the damper.

Moreover, one aspect of the portal frame according to the present invention is as follows:
A portal frame having a beam and two of the ladder-type load-bearing wall frames connected to the beam,
The dampers constituting the two ladder-type load-bearing wall structures are eccentrically positioned on the inside of the portal structure relative to the corresponding connecting members.

According to this aspect, the dampers that make up the two ladder-shaped bearing wall frames are eccentrically positioned inside the portal frame relative to the corresponding connecting members, which reduces the bending moment caused by the horizontal force during an earthquake that acts on the inner vertical member, which has a relatively large axial force (compressive force). This makes it possible to suppress the cross-sectional force (composite cross-sectional force) of the inner vertical member, eliminating the need to increase the cross-section of the inner vertical member.

In another aspect of the portal frame of the present invention, both of the two vertical members that make up the ladder-shaped bearing wall frame are pin-jointed to the beam, and the ladder-shaped bearing wall frame as a whole is rigidly joined to the beam.

According to this embodiment, the two vertical members that make up the ladder-type bearing wall frame are pin-jointed to the beam, and the two vertical members as a whole are rigidly joined to the beam. This makes it possible to form a portal frame with relatively easy joining construction using, for example, medium-sized bolts, without using high-tension bolts to join the beams and vertical members. The portal frame of this embodiment is suitable for built-in garages that have a relatively long span (wide opening) and can store multiple vehicles.

As can be understood from the above explanation, the ladder-type bearing wall structure of the present invention and the portal structure equipped with this ladder-type bearing wall structure can solve the problem of having to enlarge the cross section of the vertical members due to a relatively large composite sectional force occurring in one of the vertical members of a ladder-type bearing wall structure equipped with two vertical members.

FIG. 2 is a front view of an example of a ladder-type bearing wall structure according to an embodiment. 2A is an enlarged perspective view of a portion II in FIG. 1, and FIG. 2B is a view taken along the line bb in FIG. FIG. 2 is a front view of an example of a portal frame according to an embodiment of the present invention. FIG. 1 is a diagram for explaining an overview of load sharing between inner and outer vertical members due to a vertical load acting on a beam that constitutes a portal frame. FIG. 1 shows the bending moment generated in a ladder-type load-bearing wall structure due to horizontal forces during an earthquake, where (a) is a diagram showing the configuration of a gate-type structure of a comparative example and the bending moment of the gate-type structure, and (b) is a diagram showing the configuration of a gate-type structure of an embodiment and the bending moment of the gate-type structure.

Below, an example of a ladder-type bearing wall structure according to an embodiment and an example of a portal structure equipped with this ladder-type bearing wall structure will be described with reference to the attached drawings. Note that in this specification and the drawings, substantially identical components may be designated by the same reference numerals to avoid redundant description.

[Ladder-type bearing wall structure according to the embodiment]
First, an example of a ladder-type bearing wall structure according to an embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a front view of the ladder-type bearing wall structure according to an embodiment. Fig. 2(a) is an enlarged perspective view of part II in Fig. 1, and Fig. 2(b) is a view taken along the line bb in Fig. 2(a).

The ladder-type bearing wall structure 10 has two vertical members 1 that are parallel to each other, and a number of horizontal members 4 (three in the illustrated example) that are arranged at intervals between the two vertical members 1 in the longitudinal direction of the vertical members 1 and are connected to each of the vertical members 1. The width B1 of the ladder-type bearing wall structure 10 is a narrow width of, for example, 0.5P width (P indicates the module, e.g., 910 mm width) or 0.25P width.

The vertical member 1 is made of a square steel pipe, and at its lower end a base plate 1a that is fixed to the foundation is fixed to the square steel pipe by welding or other means.

The horizontal member 4 has one connecting member 3 including at least a steel web plate, and a steel damper 2 connected to the connecting member 3. The connecting member 3 forming the horizontal member 4 is connected to a backing plate 5a by welding, and the backing plate 5a is connected to one of the vertical members 1A by welding. The damper 2 is connected to a separate backing plate 5b by welding, and the backing plate 5b is connected to the other vertical member 1B by welding. In this way, the multiple horizontal members 4 arranged at intervals in the vertical direction between the vertical members 1 can also be called a binding member. The vertical member 1 can also be called an assembled column. In this specification, "welding" refers to appropriate welding selected according to the strength required for the connection part and the joining mode (rigid connection, pin connection), such as groove welding (full penetration welding, partial penetration welding) and fillet welding.

As shown in FIG. 2, the connecting member 3 has a web plate 3a and a flange plate 3b that is connected by welding at the upper and lower ends of the web plate 3a so as to protrude to the left and right sides of the web plate 3a. The wide surface of the web plate 3a is arranged parallel to the structural surface formed by the two vertical members 1. Also, as shown in FIG. 1 and FIG. 2, the shape of the wide surface of the web plate 3a is such that the height of the web plate 3a increases in a tapered manner from the connection end with the damper 2 toward the connection end with the vertical member 1. In the illustrated example, both the upper and lower sides of the wide surface of the web plate 3a are trapezoidal in shape, tapering toward the end. The connection plate 2a at the end of the damper 2 is connected by welding to the upper base (the short side of the parallel sides) of the trapezoid. Also, it is preferable that the flange width of the flange plate 3b of the connecting member 3 is set to be approximately the same as or less than the width of the square steel pipe that forms the vertical member 1. Furthermore, the connecting material used may have only a web plate, without a flange plate.

As shown in Fig. 2(a) and Fig. 2(b), the damper 2 in the illustrated example is a damper made of steel material with a Σ-shaped cross section perpendicular to the longitudinal direction of the horizontal member 4. Such a Σ-shaped damper 2 (Σ-shaped device) has a diagonal member (an intermediate member between a vertical member and a horizontal member) in the center, so this diagonal member has both the vertical rigidity of the vertical member and the horizontal deformation performance of the horizontal member. Therefore, it can effectively absorb earthquake energy with its strength and flexibility against excessive horizontal forces during a major earthquake. In particular, because the damper is made by bending steel material to give it a Σ-shaped cross section, its manufacturing costs are significantly cheaper than various dampers such as viscoelastic dampers, viscous dampers, and elastoplastic dampers.

When horizontal forces during an earthquake act on the ladder-type bearing wall frame 10, a large bending moment can occur at the ends of both the vertical members 1 and the horizontal members 4, which are the joints between the two. For example, during a major earthquake, which rarely occurs, the magnitude of the bending moment occurring in each member is much larger than during a general earthquake, and the vertical members can bend excessively and reach a plastic range. In the ladder-type bearing wall frame 10, the connecting members 3 that form the horizontal members 4 have a wide surface that widens toward the connection with the vertical members 1, increasing the rigidity of the joint between the vertical members 1 and the horizontal members 4. In this way, the rigidity of the vertical members 1 from the connection with the web plate 3a is expanded, shortening the bending span of the vertical members 1 and increasing the bending rigidity of the vertical members 1.

In addition, because the web plate 3a flares out toward the connection with the vertical member 1, the bending rigidity of the web plate 3a is increased and out-of-plane deformation of the web plate 3a caused by the horizontal force acting during an earthquake is also suppressed. This makes it possible to concentrate the shear force caused by the horizontal force during a major earthquake on the damper 2 without damaging the web plate 3a. For these reasons, the ladder-type load-bearing wall structure 10 can effectively absorb seismic energy during a major earthquake while causing concentrated shear deformation of the damper 2, without causing bending yield or shear yield of the vertical member 1 and the web plate 3a.

As is clear from Figures 1 and 2, the rigidity of the vertical member 1 can be freely adjusted by adjusting the inclination angle of the upper and lower sides of the web plate 3a, which flares out toward the vertical member 1, as desired. As the inclination angle of the upper and lower sides of the web plate 3a from the horizontal direction increases, the area of the wide surface of the web plate 3a increases and the rigidity of the vertical member 1 also increases, but at the same time, the material cost of the web plate 3a increases. Therefore, it is preferable to set the area of the wide surface of the web plate 3a (the inclination angle of the upper and lower sides) taking into account both the material cost of the web plate 3a and the stiffening effect of the vertical member 1 and the cross member 4.

Although not shown, the shape of the web plate may have a curved linear shape, in addition to the tapered shape shown in the example, and this curved linear shape may be asymptotic in the longitudinal direction of the vertical member 1 toward the connection end with the vertical member 1. In this shape, upper and lower flange plates are attached that show a planar shape (curved shape) complementary to the curved linear shape of the upper and lower edges of the web plate. A connecting material having a web plate of this shape can widen the rigid area of the connection with the vertical member 1 without making the area of the wide face of the web plate too large.

[Gate-type frame according to the embodiment]
Next, an example of a portal frame according to an embodiment in which the ladder-type bearing wall frame 10 is incorporated will be described with reference to Fig. 3 to Fig. 5. Here, Fig. 3 is a front view of the example of the portal frame according to the embodiment.

The portal frame 40 has a beam 20 and two ladder-shaped bearing wall structures 10 joined to the lower ends of the beam 20. The width B2 of the central span of the portal frame 40, which has a narrow ladder-shaped bearing wall structure 10 with a width B1 of 0.5P or 0.25P, can be set to a long width of, for example, about 6m to 8m, since both ends of the beam 20 are supported by the ladder-shaped bearing wall structure 10. Such a portal frame 40 with a wide opening area can be applied to the vertical structural surface of the main structure of a steel-framed building, and can also be applied, for example, to a built-in garage that stores multiple vehicles.

As shown in FIG. 3, in the portal frame 40, the dampers 2 of the horizontal members 4 that make up the two ladder-shaped bearing wall frames 10 are joined to the inner vertical members 1B, and are therefore eccentrically positioned on the inside of the portal frame relative to the connecting members 3 that are joined to the outer vertical members 1A.

For example, an end plate (not shown) is fixed to the upper end of the vertical member 1 of the ladder-type bearing wall frame 10, and the end plate and the beam 20 are pin-jointed via a number of center bolts 11. In this way, although one vertical member 1 is pin-jointed to the beam 20, the two vertical members 1 and beams 20 that make up the ladder-type bearing wall frame 10 have the same effect as if they were rigidly joined, that is, the end of the beam 20 is restrained by the two vertical members 1, and therefore the portal frame 40 becomes a portal-type rigid frame.

Meanwhile, the base plate 1a at the lower end of each vertical member 1 forming the ladder-type bearing wall frame 10 is placed on a concrete foundation 30, and anchor bolts 31 protruding upward from the foundation 30 are inserted into bolt holes (not shown) opened in the base plate 1a, and the ladder-type bearing wall frame 10 is fixed to the foundation 30 by tightening nuts.

Now, referring to Figures 4 and 5, the effect of eccentrically arranging the damper 2 on the inside of the portal in each ladder-type bearing wall frame 10 constituting the portal frame 40 will be described. Here, Figure 4 is a diagram outlining the load sharing between the inner vertical member and the outer vertical member due to the vertical load acting on the beams constituting the portal frame. Also, Figure 5 is a diagram showing the bending moment generated in the ladder-type bearing wall frame by the horizontal force during an earthquake, Figure 5(a) is a bending moment diagram of the configuration of the portal frame of the comparative example and the portal frame, and Figure 5(b) is a bending moment diagram of the configuration of the portal frame of the embodiment and the portal frame.

Figure 4 shows a case where a vertical load P1 acts on the center of the beam 20 of the portal frame 40. The acting vertical load P1 is divided into two, one for the left and one for the ladder-shaped bearing wall frames 10, but structural analysis by the inventors and others has shown that in the ladder-shaped bearing wall frames 10, the load P2 borne by the inner vertical member 1B is significantly larger than the load P3 borne by the outer vertical member 1. In some cases, a pull-out load P3' may act on the outer vertical member 1A, as shown by the dotted line in Figure 4.

For these reasons, under normal conditions (peaceful times other than during earthquakes), a larger axial force (compressive force) is generated in the inner vertical member 1B of the ladder-type bearing wall structure 10 than in the outer vertical member 1A.

During an earthquake, on the other hand, horizontal force H acts on the portal frames 40A, 40, as shown in Figures 5(a) and (b). Here, the left diagram in Figure 5(a) shows the right half of the portal frame 40A of the comparative example, and the cross member 4A that constitutes the ladder-shaped bearing wall frame 10A supporting the beam 20 has a damper 2 in the center and connecting members 3 on the left and right of it.

In the comparative portal frame 40A shown in Figure 5(a), the damper 2 is placed at the center of the horizontal member 4A of the ladder-type bearing wall frame 10A, so that the bending moment (maximum bending moment) generated in both the inner vertical member 1B and the outer vertical member 1A is M1, as shown in the bending moment diagram on the right.

As explained with reference to Figure 4, the inner vertical member 1B is subjected to a significantly larger compressive force than the outer vertical member 1A, and during an earthquake, a bending moment M1 similar to that of the outer vertical member 1A is also generated. This causes the combined section forces of the inner vertical member 1B to tend to increase, which may force the cross section (column cross section) of the inner vertical member 1B to be made larger.

In contrast, in the embodiment of the portal frame 40 shown in FIG. 5(b), the connecting members 3 that expand the rigidity area are connected only to the outer vertical member 1A, so that the bending moment M3 generated in the outer vertical member 1A can be made larger than the bending moment M2 generated in the inner vertical member 1B. In other words, a part of the bending moment M1 of the inner vertical member 1B shown in FIG. 5(a) can be shifted to the bending moment of the outer vertical member 1A.

In this way, by eccentrically positioning the damper 2 inside the portal frame 40, it is possible to reduce the bending moment generated in the inner vertical member 1B, and it is possible to suppress the composite section force in the inner vertical member 1B. This eliminates the need to enlarge the cross section (column cross section) of the inner vertical member 1B.

In this way, part of the bending moment M1 of the inner vertical member 1B is shifted to the bending moment of the outer vertical member 1A, so the bending moment M3 of the outer vertical member 1A becomes larger. However, as explained with reference to FIG. 1, the rigidity zone of the outer vertical member 1A is expanded, so the bending moment at the stress inspection position outside the rigidity zone of the outer vertical member 1A is much smaller than the bending moment M3. This makes it difficult to create a situation where the cross section (column cross section) of the outer vertical member 1A must be made larger.

Note that the configurations described in the above embodiments may be combined with other components, and the present invention is not limited to the configurations shown here. In this regard, changes can be made without departing from the spirit of the present invention, and can be determined appropriately according to the application form.

1: Vertical member 1A: Outer vertical member (vertical member)
1B: Inner vertical member (vertical member)
2: Damper 3: Connecting material 3a: Web plate 3b: Flange plate 4: Cross member 10: Ladder-type load-bearing wall structure 11: Center bolt 12: Anchor bolt 20: Beam 30: Foundation 40: Portal structure

Claims (5)

Two parallel metal vertical members;
A ladder-type bearing wall structure having a plurality of horizontal members disposed at intervals between the two vertical members in the longitudinal direction of the vertical members and connected to each of the vertical members,
the cross member has a metal tie and a metal damper connected to the tie;
A ladder-type load-bearing wall structure, characterized in that one end of the damper is connected to one of the vertical members, and one end of the connecting member is connected to the other vertical member. The connecting member has a web plate, and the wide surface of the web plate is arranged parallel to the structural surface formed by the two vertical members,
2. The ladder-type shear wall structure according to claim 1, wherein the height of the web plate increases in a fan-shaped manner from the connection end with the damper toward the connection end with the vertical member. The ladder-type bearing wall structure according to claim 2, characterized in that the connecting member has the web plate and flange plates connected to the upper and lower ends of the web plate. A portal frame having a beam and two ladder-type bearing wall frames according to any one of claims 1 to 3 connected to the beam,
A portal frame, characterized in that each of the dampers constituting the two ladder-type load-bearing wall frames is eccentrically positioned on the inside of the portal frame relative to the corresponding connecting members. The portal frame according to claim 4, characterized in that both of the two vertical members constituting the ladder-type bearing wall frame are pin-jointed to the beam, and the ladder-type bearing wall frame as a whole is rigidly joined to the beam.

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