JP4545987B2 - Direct foundation structure of a building on a steep slope with a different level of foundation - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of the direct foundation structure of a building that is built on a steep slope as shown in FIG. 1 and has a large foundation level and several floors (high difference in elevation). And a foundation structure for preventing deterioration of the seismic safety of the building.
[0002]
[Prior art]
Conventionally, when building foundations of buildings with steep slopes with different foundation levels and up and down a few floors are directly constructed with foundation structures, the deterioration of seismic safety of slopes and buildings due to differences in foundation levels is prevented. I have not heard the basic technology to do.
[0003]
However, as similar techniques, there are known techniques shown below.
(1) The base structure in the seismic isolation structure described in JP-A-10-184090 has a seismic isolation pit formed by digging the ground, and the lower end of the pillar of the structure (building) is the base isolation pit. It extends to the bottom and its lower end is slidable.
[0004]
(2) The basic structure of a building described in Japanese Examined Patent Publication No. 4-61934 is a structure in which a low-rise building and a high-rise building having different vibration properties at the time of an earthquake are integrally formed. It is set as the structure which reduces.
[0005]
By the way, when building foundations 2 and 3 of a building that is built on a steep slope as shown in FIG. The rigidity difference between the rigidity of the building frame 1a composed of columns and beams below the foundation level K on the higher side and the rigidity of the foundation 3 on the slope causes various problems in seismic safety. Incidentally, the rigidity of the base portion 3 on the slope is much larger than that of the frame 1a.
[0006]
Therefore, when a horizontal force perpendicular to the slope 6 is input to the building 1, the foundation 3 on the slope having a high rigidity against the horizontal force strongly resists, and as a result, there is a risk of causing the slope 6 to collapse. is there. Further, when a horizontal force parallel to the slope 6 is input to the building 1, the foundation 3 on the slope with high rigidity strongly resists, whereas the structure 1 having the frame 1a with low rigidity twists and vibrates. When this occurs, a corner force acts on the foundation portion 3 on the slope due to the torsional vibration, and there is a risk that the slope 6 will collapse.
[0007]
If the stability of the slope 6 decreases as the risk of collapse increases, the seismic safety of the building 1 also decreases, and there is a risk that the building 1 will collapse.
[0008]
[Problems to be solved by the present invention]
However, the prior arts (1) and (2) are not constructed under the condition that the difference in height of the foundations 2 and 3 is several floors, and is not a technique for utilizing slopes. Therefore, it is built on a steep slope and corresponds to a technology that reduces the rigidity difference between the rigidity of the frame 1a composed of columns and beams below the foundation level K on the higher side and the rigidity of the foundation 3 on the slope. do not do.
[0009]
On the other hand, when the foundations 2 and 3 that are built on the slope and have different foundation levels are directly installed on the ground surfaces 4 and 5 as the foundation, the ground anchor 7 is placed on the slope 6 as shown in FIG. It is also conceivable to increase the seismic safety of the building 1 by securing the safety of the slope 6 by strongly reinforcing 6. However, this method is not a technique for reducing the above-described rigidity difference, and there is a problem that the cost increases due to the construction of the earth anchor 7.
[0010]
Further, as shown in FIG. 5, a measure for reducing (adjusting) the rigidity difference by installing a seismic isolation device (laminated rubber) 8 on the upper and lower base portions 2 and 3 of the slope 6 can be considered. However, in order to install the seismic isolation device 8 on the foundation 2 below the slope, it is necessary to dig the ground surface 4 below the slope and construct the seismic isolation pit 9. When the ground surface 4 is dug down in order to construct the seismic isolation pit 9, the shoulder of the slope 6 retreats by the dimension L as shown by the dotted line, so that the position of the foundation 3 on the slope becomes the shoulder. There is a drawback that the risk of the slope 6 collapsing becomes high due to being too close.
[0011]
Although not shown in the figure, it is also conceivable to use a base part directly below the slope and install a seismic isolation device on the intermediate floor column above the base part. However, installing seismic isolation devices on intermediate floor pillars is difficult to implement because there are many restrictions on the functions and applications of the building.
[0012]
Therefore, the object of the present invention is to improve the rigidity of the building frame composed of the following pillars and beams from the higher side foundation level in the building with the foundation level greatly different up and down on the steep slope, and on the slope. A stiffness adjustment mechanism that can reduce the stiffness difference from the stiffness of the foundation is prepared and the stiffness value is set (adjusted) appropriately to ensure the stability of the slope and, in turn, improve the seismic safety of the building. It is to provide the basic structure directly.
[0013]
The next object of the present invention is to provide a direct foundation structure of a building that makes it possible to build a building at low cost by sufficiently securing the shoulder of a steep slope with a large difference in height and several floors. It is to be.
[0014]
[Means for Solving the Problems]
As a means for solving the above-described conventional problems, a direct foundation structure of a building that is built on a steep slope according to the invention described in claim 1 and has a significantly different foundation level is:
It is a direct foundation structure of a building that is built on a steep slope and has a very different foundation level.
The foundation on the lower foundation level is installed directly on the ground below the slope, and the foundation on the higher side is installed on the ground on the slope using a stiffness adjustment mechanism.
By setting the stiffness value of the stiffness adjusting mechanism, horizontal force in the direction orthogonal to the slope input to the foundation on the slope is reduced, and torsional vibration of the building due to horizontal force parallel to the slope is prevented. It is characterized by reducing the corner force acting on the foundation on the slope due to vibration.
[0015]
The invention described in claim 2 is a direct foundation structure of a building that is built on a steep slope according to the invention described in claim 1 and has a significantly different foundation level.
The rigidity adjusting mechanism is constituted by a horizontal displacement absorbing mechanism such as a laminated rubber.
[0016]
[Embodiments and Examples of the Invention]
The invention described in claims 1 and 2 is preferably implemented as a direct foundation structure of a building 1 that is built on a steep slope as shown in FIG.
[0017]
As shown in the schematic diagram of FIG. 2, this direct foundation structure is installed as a foundation on the ground surface 4 below the slope, and the foundation part 3 on the higher side is installed on the ground surface 4 below the slope. It is installed on the ground surface 5 on the slope using a stiffness adjusting mechanism 8. The upper and lower foundation parts 2 and 3 each have a direct foundation structure. However, the foundation part 3 on the slope is configured so that a rigidity adjustment mechanism 8 is provided directly on the foundation 10 to adjust the rigidity and allow horizontal displacement. Therefore, it is a so-called mixed direct foundation structure.
[0018]
The rigidity adjusting mechanism 8 is constituted by a horizontal displacement absorbing mechanism such as laminated rubber as an example (the invention according to claim 2). The allowable horizontal deformation is assumed to be about 1/100 or more of the difference in the basic level assuming a large earthquake. The rigidity value is such that torsional vibration does not occur in the building 1 even when a horizontal force in a direction parallel to the slope 6 is input to the building 1, that is, the building 1 may vibrate in parallel at each height level. Set to a possible stiffness value. The allowable vertical axial force is configured to ensure an allowable vertical axial force that is equal to or greater than the axial force generated at the foundation 3 on the slope.
[0019]
By setting the stiffness value of the stiffness adjusting mechanism 8 as described above, the horizontal force in the direction orthogonal to the slope 6 input to the building 1 via the foundation 3 on the slope is reduced, and the horizontal force parallel to the slope 6 is reduced. Since the torsional vibration of the building 1 due to the force is prevented and the corner force acting on the foundation portion 3 on the slope due to the torsional vibration is reduced, the building 1 is horizontal as a whole for each horizontal force in two directions. Vibrates equally in the direction parallel to the force. In this way, the rigidity adjustment mechanism 8 reduces the rigidity of the foundation portion 3 on the slope and lowers the resistance value, so that the slope 6 can be prevented from collapsing.
[0020]
That is, when a horizontal force perpendicular to the slope 6 is input to the building 1, the rigidity adjusting mechanism 8 is horizontally deformed to reduce the apparent rigidity of the foundation portion 3. Therefore, it is possible to reduce (approximate) the rigidity difference between the rigidity of the foundation 3 and the rigidity of the building frame 1a below the foundation level K on the higher side. Does not resist strongly.
[0021]
Even if a horizontal force parallel to the slope 6 is input to the building 1, the rigidity adjustment mechanism 8 is set to a rigidity value that is horizontally deformed to such an extent that the torsional vibration of the building 1 does not occur. 1 vibrates in parallel at each height level. That is, no torsional vibration is generated in the building 1, and as a result, the corner force acting on the foundation portion 3 on the slope due to the torsional vibration can be reduced or solved.
[0022]
Therefore, the stress load of the ground on the slope can be reduced to prevent the slope 6 from collapsing, the stability of the slope 6 can be secured, and the seismic safety of the building 1 can be improved.
[0023]
FIG. 3 shows the response analysis result at the time of earthquake of the building 1 by the direct foundation structure (so-called mixed direct foundation structure), and the effect of the direct foundation structure is confirmed.
[0024]
Response shear force at each floor level of the building by the conventional direct foundation structure in which the upper and lower foundation parts 2 and 3 are installed directly on the ground surfaces 4 and 5, respectively (the black triangles in FIG. 3 plots) The response shear force at each floor level of the building 1 according to the so-called mixed direct foundation structure of the present invention (the white circles in FIG. 3) was compared. In this case, the building with the conventional direct foundation structure has a sudden change in the response shear force in the vicinity of the higher foundation level, and the value reaches about 4 × 10 ³ ton (4 × 10 ⁶ kg). . It is considered that the rapid change of the response shear force acts on the ground on the slope to reduce the stability of the slope and reduce the seismic safety of the building.
[0025]
On the other hand, since the building 1 with the mixed direct foundation structure of the present invention does not have a sudden change in the response shear force as described above, the stability of the slope 6 is ensured and the earthquake resistance of the building 1 is high. I can confirm. For this reason, it is not necessary to provide a ground anchor on the slope 6 for reinforcement, which greatly contributes to cost reduction.
[0026]
In addition, by using the mixed direct foundation structure, it is not necessary to dig down the ground surface 4 below the slope 6 to construct the seismic isolation pit 9, so that the shoulder of the slope 6 is retreated and the stability of the slope 6 is impaired. There is nothing.
[0027]
In addition, the structure is simple, and the building 1 can be constructed on a steep slope regardless of the difference in level of the foundation level or the structure of the building.
[0028]
[Effects of the present invention]
According to the first and second aspects of the present invention, a direct foundation structure of a building that is built on a steep slope and has a significantly different foundation level can be obtained by installing a stiffness adjustment mechanism on the foundation portion on the slope. By reducing the apparent rigidity of the part, it is possible to reduce (approximate) the rigidity difference between the rigidity of the foundation part and the rigidity of the following building frame from the higher foundation level.
[0029]
Therefore, the stress load of the ground on the slope can be reduced, the slope can be prevented from collapsing, the stability of the slope can be secured, and the seismic safety of the building can be enhanced.
[0030]
In addition, the present invention is simple in construction, easy to implement and inexpensive, and makes it possible to build a building using a steep slope regardless of the difference in level of the foundation level or the structure of the building. .
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an elevational view showing a building having a large foundation level and several floors that is built on a steep slope where the inventions described in claims 1 and 2 are implemented.
FIG. 2 is an elevational view schematically showing a direct foundation structure of a building which is built on a steep slope according to the first and second aspects of the present invention and has a significantly different foundation level.
FIG. 3 shows a response analysis result of a building having a mixed direct foundation structure during an earthquake.
FIG. 4 is an elevational view conceptually showing a conventional building that is built on a steep slope and has a foundation having a foundation level that is different by several floors and is directly installed on the ground surface.
FIG. 5 is an elevation view conceptually showing a building in which seismic isolation devices are installed on the upper and lower foundations of the slope in order to prevent torsional vibrations and the like of the building.
[Explanation of symbols]
1 Building 1a From the foundation level on the higher side to the following frame 2 Foundation part on the lower foundation level (below the slope) 3 Foundation part on the higher foundation level (on the slope) 4 Ground surface under the slope 5 Ground on the slope Surface 6 Slope 8 Stiffness adjustment mechanism 10 Direct foundation K High foundation level

Claims (2)

It is a direct foundation structure of a building that is built on a steep slope and has a very different foundation level.
The foundation on the lower foundation level is installed directly on the ground below the slope, and the foundation on the higher side is installed on the ground on the slope using a stiffness adjustment mechanism.
By setting the stiffness value of the stiffness adjustment mechanism, horizontal force perpendicular to the slope input to the foundation on the slope is reduced, and torsional vibration of the building due to horizontal force parallel to the slope is prevented. A direct foundation structure of a building on a steep slope with significantly different foundation levels, characterized by reducing the corner forces acting on the foundation on the slope due to vibration. 2. The direct foundation structure of a building on a steep slope having a significantly different foundation level according to claim 1, wherein the rigidity adjusting mechanism is composed of a horizontal displacement absorbing mechanism such as laminated rubber.

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