Building foundation structure

Abstract

The objective is to reduce the vertical acceleration that occurs in the building when it re-grounds after it has been lifted, without installing a vibration isolation device between the underside of the building's foundation and the ground. [Solution] The building foundation structure comprises a foundation on the ground provided for the building, a protruding portion that projects laterally from the periphery of the foundation, and a damping device that extends vertically, with its upper end attached to the protruding portion and its lower end attached to the ground, and which exerts damping force by expanding and contracting vertically.

Description

Technical Field

[0001] This disclosure relates to building foundation structures.

Background Art

[0002] In the seismic isolation support method described in Patent Document 1, in a seismic isolation support method for a building in which the building is supported on the ground by a laminated rubber body formed by alternately stacking a large number of thin metal plates and rubber sheets, a laminated rubber body for preventing overturning is installed downward at a site where a negative axial force is likely to occur in the building receiving seismic input to bear the negative axial force, so that the negative axial force does not act on the laminated rubber body for long-term load.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a building that floats during an earthquake, an impact vertical acceleration occurs in the building along with the re-grounding after floating. As a countermeasure for reducing this vertical acceleration, a vibration isolation device may be installed between the lower surface of the building foundation and the ground. However, with such a structure, it is difficult to construct the vibration isolation device after the completion of the building.

[0005] The problem of this disclosure is to reduce the vertical acceleration that occurs in the building along with the re-grounding after the building floats without installing a vibration isolation device between the lower surface of the building foundation and the ground.

Means for Solving the Problems

[0006] The building foundation structure according to the first embodiment is characterized by comprising a foundation on the ground provided for the building, a projection that protrudes laterally from the periphery of the foundation, and a damping device that extends in the vertical direction, with its upper end attached to the projection and its lower end attached to the ground, and which exerts a damping force by expanding and contracting in the vertical direction.

[0007] According to the above embodiment, a damping device that exerts damping force by expanding and contracting in the vertical direction is arranged between the protruding portion that projects laterally from the periphery of the foundation provided on the ground and the ground.

[0008] This design allows the building to lift during an earthquake, and the damping device exerts a damping force when it re-grounds after lifting. In this way, it is possible to reduce the vertical acceleration that occurs in the building when it re-grounds after lifting, without installing a vibration isolation device between the underside of the building's foundation and the ground.

[0009] The building foundation structure according to the second embodiment is characterized in that, in the building foundation structure described in the first embodiment, the protruding portion is provided so as to protrude in all four directions from the foundation, and a plurality of damping devices are provided and each is attached to the protruding portion that protrudes in all four directions.

[0010] According to the above embodiment, the damping devices are attached to the protrusions that extend outwards from the foundation in all four directions. By arranging the damping devices to surround the foundation in this way, the vertical acceleration that occurs in the building when it re-grounds after floating can be effectively reduced.

[0011] The building foundation structure according to the third embodiment is characterized in that, in the building foundation structure described in the first or second embodiment, the damping device is a viscous damper.

[0012] According to the above embodiment, by using a viscous damper as a damping device, the vertical acceleration generated in the building when it re-grounds after floating can be reduced.

[0013] The building foundation structure according to the fourth embodiment is characterized in that, in the building foundation structure described in any one of the first to third embodiments, the upper end of the damping device is pin-connected to the protruding portion, and the lower end of the damping device is pin-connected to the ground.

[0014] According to the above embodiment, the upper and lower ends of the damping device are pin-connected to the mounting target. This allows the damping device to easily follow the horizontal movement of the foundation. [Effects of the Invention]

[0015] According to this disclosure, it is possible to reduce the vertical acceleration that occurs in the building when it is re-grounded after it has been lifted, without installing a vibration isolation device between the lower surface of the building's foundation and the ground. [Brief explanation of the drawing]

[0016] [Figure 1] This is a front view showing the building foundation structure according to the first embodiment of this disclosure. [Figure 2] This is a plan view showing the building foundation structure according to the first embodiment of this disclosure. [Figure 3] (A)(B) These are operation diagrams showing the operation of the building foundation structure according to the first embodiment of this disclosure. [Figure 4] This is a drawing showing an analytical model for a building foundation structure according to the first embodiment of this disclosure. [Figure 5] This diagram shows the analysis results for the building foundation structure according to the first embodiment of this disclosure in table format. [Figure 6] (A)(B) This is a diagram showing the analysis results for the building foundation structure according to the first embodiment of this disclosure in graph form. [Figure 7] This is a front view showing a building foundation structure according to a second embodiment of this disclosure. [Figure 8] This is a plan view showing the building foundation structure according to the second embodiment of this disclosure. [Figure 9] This is a perspective view showing a damping member used in a building foundation structure according to a second embodiment of this disclosure. [Figure 10] It is a front view showing the building foundation structure according to the third embodiment of the present disclosure.

Mode for Carrying Out the Invention

[0017] <First Embodiment> An example of the building foundation structure according to the first embodiment of the present disclosure will be described with reference to FIGS. 1 to 6. The arrow H shown in each figure indicates the vertical direction, which is the up-and-down direction of the building foundation structure, the arrow W shown in each figure indicates the width direction of the building foundation structure, which is orthogonal to the arrow H and is in the horizontal direction, and the arrow D shown in each figure indicates the depth direction of the building foundation structure, which is orthogonal to the arrows H and W and is in the horizontal direction.

[0018] (Building Foundation Structure 10) As shown in FIG. 1, the building foundation structure 10 according to the first embodiment includes a foundation 12 provided in a building 100, a protruding portion 22 protruding laterally (horizontally) from the foundation 12, and a damping device 32.

[0019] 〔Foundation 12, Protruding Portion 22〕 The foundation 12 is a direct foundation without piles and is made of reinforced concrete installed on the ground G as shown in FIGS. 1 and 2. In this embodiment, the foundation 12 is rectangular when viewed from above. The foundation 12 is formed with a pair of side surfaces 12a facing the outside in the width direction and a pair of side surfaces 12b facing the outside in the depth direction. Here, the installation of the foundation 12 on the ground G means that the foundation 12 is directly supported by the ground G, and it means that no vibration isolation device is installed between the lower surface of the foundation 12 and the ground.

[0020] The protruding portion 22 is made of reinforced concrete and protrudes in all directions from the side surfaces 12a and 12b of the foundation 12 as shown in FIGS. 1 and 2. That is, the protruding portion 22 protrudes in a pair from the side surface 12a to the outside in the width direction and protrudes in a pair from the side surface 12b to the outside in the depth direction.

[0021] Specifically, a space R is formed between the foundation 12 and the ground G, surrounding the foundation 12 from the horizontal direction. The protruding portion 22 extends into space R from the upper parts of the sides 12a and 12b, and the protruding end (tip) of the protruding portion 22 is separated from the ground G in the horizontal direction.

[0022] Furthermore, the projection 22 that protrudes in the width direction from the side surface 12a extends in the depth direction. The projection 22 that protrudes in the depth direction from the side surface 12b extends in the width direction. The projection 22 has a downward-facing lower surface 22a.

[0023] [Damping device 32] The damping device 32 is located below the protrusion 22, as shown in Figures 1 and 2. The damping device 32 comprises a resistance rod 34 and a viscous liquid tank 38 in which a viscous substance V is stored.

[0024] -Resistance rod 34- The resistance rods 34 are attached to the lower surface 22a of the protruding portion 22 and extend downward from the lower surface 22a. Furthermore, the resistance rods 34 attached to the lower surface 22a of the protruding portion 22 that protrudes from the side surface 12a extend in the depth direction, and the resistance rods 34 attached to the lower surface 22a of the protruding portion 22 that protrudes from the side surface 12b extend in the width direction. In this way, four resistance rods 34 are provided.

[0025] Specifically, each resistance rod 34 has a base end portion 34a attached to the lower surface of the protruding portion 22, and an extension portion 34b extending downward from the base end portion 34a. The width of the extension portion 34b is narrower than the width of the base end portion 34a, and the cross-section of the extension portion 34b is a downward-extending rectangular shape.

[0026] -Viscous liquid tank 38- Four viscous liquid tanks 38 are provided, positioned below each of the protruding portions 22, with the tops of the viscous liquid tanks 38 being open. As mentioned above, the viscous substance V is stored inside the viscous liquid tanks 38. The extended portion 34b of the resistance rod 34 is immersed in the viscous substance V. Here, the viscous substance V is a fluid similar to the viscous substance V used in seismic damping walls.

[0027] The viscous liquid tank 38 is supported from below by a support 46 provided in the ground G. This support 46 has an L-shaped cross-section and comprises a vertical portion 46a that faces the tip of the protruding portion 22 in the horizontal direction, and a horizontal portion 46b to which the viscous liquid tank 38 is attached and which supports the viscous liquid tank 38 from below.

[0028] (action) Next, the function of the building foundation structure 10 will be explained. When an earthquake occurs, the building 100 equipped with the building foundation structure 10 may vibrate in the vertical direction.

[0029] When building 100 vibrates vertically due to an earthquake, the foundation 12 also vibrates vertically, as shown in Figures 3(A) and 3(B). Furthermore, as the foundation 12 vibrates vertically, the resistance rod 34 vibrates (moves) vertically.

[0030] As the resistance rod 34, immersed in the viscous substance V, moves vertically, a viscous resistance force is generated on the resistance rod 34. In other words, the damping device 32 exerts a damping force by expanding and contracting vertically.

[0031] The damping device 32 exerts a damping force, resulting in lower acceleration when moving upward and downward on the foundation 12 compared to the case where no damping device is provided.

[0032] Thus, in the building foundation structure 10, the vertical acceleration that occurs in the building 100 when the building 100 is re-grounded after floating is reduced without the need to install a vibration isolation device between the lower surface of the foundation 12 of the building 100 and the ground.

[0033] 〔analysis〕 To compare the building foundation structure 10 of this application with conventional foundation structures, an analysis was performed using the finite element method. Specifically, the analysis was used to compare the induced vertical movement that occurs on the central axis of the building due to the uplift of the foundation when horizontal motion is input. More specifically, the minimum ground contact ratio of the building (ground contact ratio: ratio of the contact area to the foundation area) and the vertical response acceleration [gal] of the building were compared between the building foundation structure 10 and conventional foundation structures.

[0034] -Analysis conditions- The analysis was performed using the analysis model M shown in Figure 4. The building to be analyzed had a height of 40 [m], a foundation width of 50 [m], a foundation depth of 50 [m], a building mass of 200,000 [t] (of which the foundation mass was 150,000 [t]), a horizontal natural frequency of 5 [Hz], and a vertical natural frequency of 12 [Hz]. Furthermore, the foundation side of this building was set to 1 [m]. 2 A damping force of 11.2 kNs / mm was applied to the area.

[0035] Then, we analyzed the case where a maximum acceleration of 1000 [gal] was used as the input seismic motion to the building, and the case where a maximum acceleration of 1350 [gal] was used. Furthermore, buildings with conventional foundation structures do not have damping forces applied to the sides of the foundation.

[0036] -Analysis results- The table shown in Figure 5 contains the analysis results for the minimum grounding ratio of the conventional foundation structure and the analysis results for the minimum grounding ratio of the foundation structure of the present invention, respectively.

[0037] As shown in this table, when a maximum acceleration of 1000 [gal] was used as the input seismic motion, the minimum ground contact ratio of the conventional foundation structure was 23.8 [%], while the minimum ground contact ratio of the foundation structure of the present invention was 43.3 [%]. On the other hand, when a maximum acceleration of 1350 [gal] was used as the input seismic motion, the minimum ground contact ratio of the conventional foundation structure was 0.0 [%], while the minimum ground contact ratio of the foundation structure of the present invention was 14.3 [%].

[0038] Furthermore, the graph shown in Figure 6(A) shows the vertical response acceleration [gal] of the building when a maximum acceleration of 1000 [gal] is used as the input seismic motion. Specifically, the horizontal axis of this graph represents the period [s], and the vertical axis represents the response acceleration spectrum [gal]. The dashed line in the graph represents the analysis results of the conventional foundation structure, and the solid line in the graph represents the analysis results of the foundation structure of the present invention.

[0039] This graph shows that the vertical response acceleration of the foundation structure of the present invention is lower than that of the conventional foundation structure.

[0040] Furthermore, the graph shown in Figure 6(B) shows the vertical response acceleration [gal] of the building when a maximum acceleration of 1350 [gal] is used as the input seismic motion. The dashed line in the graph represents the analysis results of the conventional foundation structure, and the solid line represents the analysis results of the foundation structure of the present invention.

[0041] This graph shows that the vertical response acceleration of the foundation structure of the present invention is lower than that of the conventional foundation structure.

[0042] (summary) As explained using the analysis results above, in the building foundation structure 10, the vertical acceleration that occurs in the building 100 when the building 100 is re-grounded after floating can be reduced without installing a vibration isolation device between the lower surface of the foundation 12 of the building 100 and the ground G.

[0043] Furthermore, in the building foundation structure 10, the damping device 32 is arranged to surround the foundation 12 from all four sides. This effectively reduces the vertical acceleration that occurs in the building 100 when it re-grounds after floating.

[0044] <Second Embodiment> Next, an example of a building foundation structure according to the second embodiment will be described using Figures 7 to 9. The second embodiment will mainly be described in terms of the differences from the first embodiment.

[0045] (Building foundation structure 110) The building foundation structure 110 according to the second embodiment, as shown in Figure 7, comprises a foundation 12 provided on the building 100, a projection 22 that protrudes laterally (horizontally) from the foundation 12, and a damping device 132.

[0046] [Damping device 132] As shown in Figures 7 and 8, the damping devices 132 are positioned below the protrusion 22 and are arranged in a row in the depth direction or width direction. Each damping device 132 comprises a resistance rod 134 and a viscous liquid tank 138 in which a viscous substance V is stored.

[0047] -Resistance rod 134- As shown in Figures 7 to 9, the resistance rod 134 is a stepped cylindrical shape, attached to the lower surface 22a of the projection 22, and extends downward from the lower surface 22a. Specifically, it has an enlarged diameter portion 134a attached to the projection 22, and a smaller diameter portion 134b that extends downward from the lower surface of the enlarged diameter portion 134a and is smaller in diameter than the enlarged diameter portion 134a.

[0048] -Viscous liquid tank 138- As shown in Figures 7 to 9, the viscous liquid tank 138 is a bottomed cylindrical shape with an open top, and is provided for each resistance rod 134. A viscous substance V is stored inside the viscous liquid tank 138. Furthermore, the small diameter portion 134b of the resistance rod 134 is immersed in the viscous substance V.

[0049] Furthermore, the function of the building foundation structure 110 in the second embodiment is the same as that of the building foundation structure 10 in the first embodiment.

[0050] <Third Embodiment> Next, an example of a building foundation structure according to the third embodiment will be described using Figure 10. The third embodiment will mainly be described in terms of the differences from the second embodiment.

[0051] (Building foundation structure 160) The building foundation structure 160 according to the third embodiment, as shown in Figure 10, comprises a foundation 12 provided on the building 100, a projection 22 protruding laterally (horizontally) from the foundation 12, and a viscous damper 182. The viscous damper 182 is an example of a damping device.

[0052] [Viscous damper 182] The viscous dampers 182 are so-called hydraulic damping dampers, and as shown in Figure 10, they are positioned below the protrusion 22 and are arranged in a row in the depth direction or width direction. Each viscous damper 182 comprises a cylinder 184 filled with a viscous substance V and a piston rod 186, part of which is inserted into the cylinder 184.

[0053] The cylinder 184 is pin-coupled to the lateral portion 46b of the support 46 via the cylinder bracket 184a. Furthermore, the piston rod 186 is pin-coupled to the projection 22 via the rod bracket 186a.

[0054] (summary) As explained above, in the building foundation structure 160, by using a viscous damper as a damping device, the vertical acceleration that occurs in the building 100 when it re-grounds after floating can be reduced.

[0055] Furthermore, in the building foundation structure 160, the upper end of the viscous damper 182 is pin-connected to the protruding portion 22, and the lower end of the viscous damper 182 is pin-connected to the lateral portion 46b of the support 46. This allows the viscous damper 182 to easily follow the horizontal movement of the foundation 12.

[0056] Although this disclosure has described specific embodiments in detail, it will be apparent to those skilled in the art that this disclosure is not limited to these embodiments, and that various other embodiments are possible within the scope of this disclosure. For example, although not specifically described in the first and second embodiments above, the upper and lower ends of the damping devices 32 and 132 may be pin-connected to the mounting portion. By pin-connecting in this manner, the damping devices 32 and 132 can easily follow the horizontal movement of the foundation 12.

[0057] Furthermore, although the projection 22 is made of reinforced concrete in the above embodiment, it is not limited to reinforced concrete and may be made of steel or the like, as long as the projection 22 has the function of supporting the damping device. [Explanation of Symbols]

[0058] 10. Building foundation structure 12 Basics 22 Protrusion 32 Damping device 100 buildings 110 Building foundation structure 132 Damping device 160 Building foundation structure 182 Viscous damper (an example of a damping device) G Ground

Claims

1. The foundation on the ground that is installed in the building, A protruding portion that projects laterally from the periphery of the aforementioned foundation, A damping device that extends vertically, has its upper end attached to the protruding part, and its lower end attached to the ground, and exerts damping force by expanding and contracting vertically, A building foundation structure equipped with the following features.

2. The aforementioned protrusions are provided so as to protrude in all four directions from the foundation. Multiple damping devices are provided and each is attached to the protruding portion that protrudes in all four directions. The building foundation structure according to claim 1.

3. The damping device is a viscous damper. The building foundation structure according to claim 1.

4. The upper end of the damping device is pin-connected to the protruding portion, and the lower end of the damping device is pin-connected to the ground. A building foundation structure according to any one of claims 1 to 3.

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