JPH02510B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a super high-rise building that has high proof strength and is rich in toughness, is resistant to cracking even when subjected to severe repeated loads due to earthquakes, and does not cause shear failure. This is a slip shear wall with a new mechanism suitable for flexible structures such as buildings.

[Conventional technology]

The most effective and economical way to withstand the horizontal loads caused by earthquakes and typhoons is to install shear walls and braces at important points in a building. In conventional reinforced concrete shear walls, the boundaries between columns, beams, or foundation beams around the wall slab are always rigidly connected through wall vertical and horizontal reinforcements, and precast reinforced concrete (hereinafter abbreviated as "PC") shear walls In this case, by creating unevenness around the PC wall slab and burying the convexity in the surrounding concrete cast on site, it will work as a solid reinforced concrete structure against the horizontal shearing force caused by earthquakes. That's what I do.

[Problem to be solved by the invention]

Conventional reinforced concrete shear walls have higher rigidity and lower toughness than rigid frames made of columns and beams, in other words, they are hard and brittle, so they are susceptible to damage or damage due to the large input that occurs to the building during an earthquake. This is disadvantageous because the building is prone to overturning, and stress is excessively concentrated on the shear wall, which cannot follow the deformation and breaks first, which reduces the overall strength and causes the building to collapse. It happens. In other words, as shown in Figure 5a, in the case of ordinary reinforced concrete shear walls, the maximum strength is reached with only a small amount of deformation, and if the deformation continues further, shear failure will occur and the strength will suddenly be lost. In combination with , the time point at which the maximum strength is reached is different for both, and the maximum strength cannot be added.

Furthermore, as mentioned above, even slight inter-layer deformation causes frequent cracking and reaches the maximum yield strength, and if the deformation progresses further, the yield strength decreases significantly, and the concrete may begin to break and fall under repeated loads due to earthquakes. This results in a rapid loss of strength. This is because ordinary shear walls rely on shear failure and crushing of concrete and plastic deformation of wall reinforcing bars to absorb seismic energy, so they cannot withstand large deformations or repeated loads.

The purpose of the present invention is to overcome the problems of concrete walls, that is, the inevitable drawbacks of being hard and brittle, and to provide reinforced concrete buildings with unprecedented tenacity.

[Means to solve the problem]

In order to solve the above-mentioned problems of shear walls, in the present invention, the lower end of the reinforced concrete or precast reinforced concrete wall plate is connected to the lower floor beam or the foundation beam using a flat concrete layer that does not pass through the wall longitudinal reinforcement. The wall slab will rub against the lower floor beam or foundation beam when an earthquake horizontal force is applied to the boundary surface.
One or more X-shaped steel braces are built into or attached to the wall slab with their ends fixed to the beams above and below the wall slab or to the foundation beam.

As a result, when an earthquake horizontal force is applied, the wall slab can slip at the boundary with the lower floor beam or foundation beam without causing damage to the concrete wall slab while taking advantage of the horizontal strength of the brace. ,
The initial stiffness is slightly lowered, which delays reaching the maximum yield strength, and furthermore, even after the maximum yield strength, shear failure of the wall slab does not occur, thereby preventing a decrease in yield strength. In other words, it becomes a tough shear wall as shown in Fig. 5b, and when combined with a rigid frame, the maximum yield strength of both can be synergized, and high yield strength can be maintained until large inter-story deformation occurs.

〔Example〕

Fig. 1 is a view of an example of an earthquake-resistant frame using the shear wall of the present invention, and Fig. 2 is a cross-sectional view thereof. 1 is a wall slab made of reinforced concrete or precast reinforced concrete, and the foundation beam 4 at the lower end or the lower There are no vertical wall reinforcements on the boundary with the floor beams 5, and even in the case of PC wall slabs, there are no uneven sheath stones, and the cast-in-place or precast wall slabs are simply placed on a flat concrete pouring surface. Leave it in a state where it is only attached.
This boundary thereby becomes the sliding surface 6 of the wall slab. Next, one or more steel braces 2 are placed in an X shape toward the four corners of the wall slab 1, either buried in the concrete of the wall slab 1 or placed along both sides of the wall slab 1. The lower end is fixed in the foundation or foundation beam 4 by use of anchoring fittings 2a or by other methods, and its upper end is fixed in the same manner in the beam 5 directly above the wall slab 1.

The steel brace 2 can be made of bar steel, stranded wire, flat steel,
Anything such as shaped steel or steel pipes is acceptable, but for example, high-strength PC
Steel rods or prestressed steel wires (PC strands) are efficient, and when buried in the wall slab 1, unbonded tendons, etc. that have been coated with adhesive insulation in advance are suitable because they are easy to install. It is thought that In addition to the material, cross section, and shape, the number of braces can also be freely selected. In addition, when seeking large horizontal deformability, both sides of wall slab 1 and column 3
It is desirable to provide a distance 7 equal to the amount of movement of the wall plate between them. The gap 7 can be easily formed by embedding a compressible filler such as expanded polystyrene in concrete. In the case of a continuous shear wall, the upper floors are constructed using the same method as shown in the diagram, and in the case of a continuous span shear wall, a similar shear wall is installed continuously on the adjacent span.

Another effective method is to use prestressed steel rods or strands as braces and tension the upper ends to give initial tension to the braces, as well as to introduce prestress into the concrete wall slab and surrounding columns and beams. This can further increase seismic strength and toughness.

Figure 4 shows a different embodiment used for a door boundary wall in the beam direction of a high-rise apartment building.In this case, since the wall length is long compared to the floor height, multiple X
A type of steel braces 2 are installed, and multiple floors are connected, and the number of braces is gradually reduced as one goes to the upper floors. In addition, the pillars 3 are arranged outside the corridor 8 and the balcony 9 so that there is a distance between them and the wall slab 1, so that even if the wall slab 1 slips on the sliding surface 6 and moves horizontally due to the earthquake horizontal force, the pillar 3 will remain stable. By taking into consideration the possibility of colliding with the legs and widening the spacing between columns, the pull-out force and increased axial force applied to the columns and foundation piles during an earthquake are reduced, which is advantageous against the building's overturning and shaking. It was planned.

In addition to X-type braces, V-type and Λ-type braces can be inserted.
Various shapes can be considered, such as shapes, and when an earthquake horizontal force is applied, it produces a resistance force due to the horizontal component force, and
Any form that applies a vertical load to the sliding surface is effective.

[Effect]

When an earthquake horizontal force Q is applied to the frame shown in Figures 1 and 2, the frame deforms as shown in Figure 3, causing the column 3 to bend and the wall slab 1 to move horizontally along with the beam 5 directly above it. . The reason for this is that the wall slab 1 and the beam 5 directly above it are connected by wall reinforcements, and in contrast to reinforced concrete wall slabs where the concrete is poured in one piece, the lower end of the wall slab 1 and the foundation beam 4 directly below it, In addition to the fact that there are no vertical wall reinforcements passing through the interface with the beam 5,
Since the upper wall concrete is poured after the lower concrete is poured and hardened, its shear strength is lower than that of the reinforced concrete wall that is cast at the same time, and if horizontal shear force due to an earthquake is applied, this interface will be damaged. breaks off naturally to form the sliding surface 6, and the wall plate 1
This is because it slips.

When horizontal deformation occurs in this way, tension T is generated in the extension side brace, and the following relational expression is established between the tension force T and the seismic horizontal force Q applied to the frame.

Q=T・cosθ+μ(T・sinθ+W)+Qc...(1) Symbol Q: Earthquake horizontal force applied to the shear wall structure T: Tension of extension side brace μ: Friction coefficient on sliding surface W: Building weight applied to the shear wall Qc : Shear force borne by the columns on both sides of the earthquake wall. In other words, the earthquake horizontal force Q is resisted by the horizontal component T・cosθ of the tension T of the extension side brace, and the vertical component T・sinθ and the building in the area The sum of the weight W is applied as a vertical load from the wall slab 1 to the foundation beam 4 or lower floor beam 5 directly below, and at the sliding surface 6 at the boundary, it slips horizontally while being pressed and rubbed by the vertical force of (T・sinθ+W). , in this case, this vertical force multiplied by the friction coefficient μ between the concrete on the sliding surface effectively acts as a horizontal resistance force. Then this μ(T・sinθ+W)
As long as the concrete wall does not exceed the shear strength of the concrete wall, the wall slab will not crack even if it is subjected to severe repeated loads due to an earthquake, and the brace will not fully stretch even if there is a large horizontal deformation as shown in Figure 3. This horizontal resistance force does not decrease until it ruptures. In addition, the friction generated when the building moves back and forth while being pressed against the sliding surface consumes a large amount of energy that enters the building during an earthquake, and this energy absorption ability does not diminish over time. Note that the value of the friction coefficient μ can be increased or decreased to some extent depending on whether the sliding surface is made smooth or slightly rough. All of the above was confirmed through repeated positive and negative loading experiments using a shear wall model.

The relationship between the horizontal load Q and the deformation δ, that is, the history curve, is shown in FIGS. 6a and 6b, which were obtained by repeated positive and negative tests of a conventional shear wall and a shear wall of the present invention. This clearly shows the difference in deformation performance and energy absorption ability. In other words, conventional reinforced concrete shear walls believe that it is essential to integrate the surrounding columns and beams, and the pouring interface between the two is designed with enough space to completely transmit shear stress without causing relative displacement. Currently, shear reinforcements and a considerable amount of shear reinforcing bars are constructed at a great deal of effort and expense, but the shear wall according to the present invention breaks through this common sense and completely eliminates these shear reinforcements. When force is applied, as mentioned above, it is made to naturally slip at the boundary surface between the pouring joints at the lower end of the wall slab. This change in thinking led to the creation of a shear wall with a new mechanism that is completely different from conventional shear walls.

〔Effect of the invention〕

The shear wall according to the invention has a number of advantages, including:

(1) Since slips have lower rigidity than monolithic reinforced concrete walls, the natural period of the building becomes longer and the input to the building during an earthquake generally becomes smaller. In other words, it is a flexible shear wall similar to the shear walls with slits that are often used in conventional high-rise buildings, but unlike shear walls with slits, there are no slits in the wall that require special processing.
It is also advantageous in that sense because it only needs to be slipped in an inconspicuous area around the wall.

(2) As is clear from the above experimental results in Figure 6b, the yield strength decreases only slightly after reaching the maximum yield strength, and after that, the yield strength is maintained until large interlaminar deformation occurs, and the plasticity rate is extremely high. Since it has been proven to be a shear-resistant wall, it can be used to increase the toughness of buildings.

(3) General earthquake-resistant walls absorb earthquake energy through cracking, shear failure and crushing of concrete wall slabs, and plastic deformation of reinforcing bars, so if they receive large repeated loads from earthquakes, they will gradually fail. When enlarged, as shown in Figure 6a, it loses its bearing strength and its energy absorption capacity decreases, which is dangerous.In contrast, this earthquake-resistant wall has the aforementioned load-bearing mechanism and sliding surface that presses down on the wall slab when it rubs. Since this method absorbs earthquake energy through the friction of do not have.

(4) Therefore, after a major earthquake, ordinary shear walls will leave large damage marks and require considerable repair work, but even if this shear wall undergoes large interstory deformation, the phenomenon will only occur on the slip surface. Since the wall slab itself moves left and right following the deformation of the frame and does not cause shear failure, it hardly requires repair even after a major earthquake, making it a maintenance-free earthquake-resistant wall.

(5) Also, there is no need for wall reinforcement at the boundary between the wall slab and the foundation beam or beam directly below it, and there is no need to do anything with the flat concrete pouring surface, making construction easy and economical. It is also advantageous in terms of construction period.

(6) As mentioned above, this shear wall is based on a completely new mechanism that overcomes the hardness and brittleness that was the fate of conventional reinforced concrete shear walls, and it exhibits high strength and energy absorption capacity up to large deformations. Therefore, when applied to actual design, it can be used in various ways depending on the scale and purpose of the building. In other words, by appropriately selecting the wall thickness of the shear wall, the type and amount of braces, and the strength of the concrete and steel used, it is possible to adjust the strength, rigidity, and toughness of the entire building as desired. It is possible to construct strong and durable buildings economically.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of the shear wall of the present invention, Figure 2
The figure is a cross-sectional view of the structure, Figure 3 shows the deformation of the frame and the stress generated in the braces when an earthquake horizontal force is applied to it, Figure 4 shows a different embodiment, and Figure 5 a , b represent the relationship between load and deformation in combination with a rigid frame for a general shear wall and a tough type shear wall, respectively. Represents the relationship between horizontal load and deformation when a load is applied. 1 is a wall slab, 2 is a steel brace, 2a is a fixture, 3 is a column, 4 is a foundation beam, 5 is a beam, 6 is a sliding surface, 7 is a floor, 8 is a hallway, and 9 is a balcony.

Claims (1)

[Claims] 1. The boundary between the lower end of a reinforced concrete or precast reinforced concrete wall slab and the lower floor beam or foundation beam is a flat concrete pouring surface that does not pass through wall longitudinal reinforcement, and an earthquake horizontal force is applied to that boundary surface. Sometimes, one or more X-shaped steel braces are fixed at their ends to the upper and lower beams or foundation beams of the wall slab, so that the wall slab rubs while being pressed against the lower floor beam or foundation beam. Slip shear wall with braces built into or attached to the wall slab.