JP2000291026A - Block layered base isolation footing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a series of layered footings having the control of differential settlement and improvement of load bearing capacity of ground as well as base isolation function for footings of construction and civil engineering building. SOLUTION: A plurality of blocks 1 as a simple substance having a special feature such as a truncated cone or the like on both up and down are arranged to a plurality of layered stages to pile up as a layered footing, blocks 2 are constrainedly fitted between the layered stages, and a stabilized multi-story is constructed. The control of differential settlement and improvement of load bearing capacity of ground by dispersion or the like of load to the ground and, at the same time, in the case f earthquake, the base isolation function damped and relieved by sliding friction or the like of the blocks 2 (base isolation blocks) fitting dynamic response of an upper structure to the inside while following the relative displacement of the structure and the ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foundation of a building and a civil engineering structure, and is used as a seismic isolation mechanism together with a function of improving a bearing capacity.

[0002]

2. Description of the Related Art Conventionally, a foundation for laying natural rock and cobble stone as a foundation of a structure for a sedimentary ground has a function of dispersing a load caused by a non-planar shape of a ground contact surface and a laminated structure and improving a bearing capacity. There has been widely constructed. In recent years, it has become difficult to procure natural materials of appropriate shape and quality due to the progress of river improvement and maintenance and the rise in environmental protection, and the lack of skilled technicians such as masonry has made it difficult to handle construction work. In addition, since these are empty stacked structures, they can slightly reduce the dynamic transmission from the ground during an earthquake, but cannot expect a positive function or effect as a seismic isolation due to the restraint of horizontal displacement.

[0003] The basics of laying the top block
5650054) is also a kind of lamination, and is constructed to suppress uneven settlement and strengthen the ground as well as the Kuriishi lamination. However, due to the instability of the block itself, the implementation of round bars and drilling on the ground and blocks is complicated, and the stacking of multiple steps is unstable. In addition to the difficulty, the function of seismic isolation cannot be expected due to its structure. On the other hand, rubber-laminated seismic isolators and mechanical vibration control devices have been put into practical use for middle- and high-rise buildings, but the structure and construction are simple for relatively low-rise buildings. Inexpensive, low performance degradation, etc., and high durability as a buried structure. There is no seismic isolation mechanism integrated with basic functions.

[0004]

SUMMARY OF THE INVENTION The functions of the conventionally used laminating foundation of marble stones are made more rational, materials are supplied by controlled factory standard products, quality control is streamlined and workability is improved. In addition to the functions of suppressing uneven settlement by rational distribution of load and improving ground bearing capacity, a series of laminated foundations with seismic isolation function at low cost are obtained.

[0005] The seismic isolation function is to attenuate and mitigate the transmission of seismic motion. As an isolator function, it is softly supported in the horizontal direction to reduce the transmission of dynamic energy and lengthen the swing response of the building. , As a damper function,
It limits the response displacement and absorbs and attenuates the dynamic energy. With these functions, it is intended for relatively low-rise buildings with a simple structure, simple construction and low cost, and there is little change in performance due to temperature dependence even in cold regions, An effective seismic isolation mechanism that is unnecessary.

[0006]

In order to solve the above-mentioned problems, a laminated base of the present invention is shown in FIGS. 1, 2 and 3.
A single laminated block (1) is arranged and laid in a plurality of lamination stages on a root excavation ground, and is piled up. The internal space formed between each stacking stage is fitted with a block (2) that conforms to the shape of the space, constructing a stable stack of empty stacks, dispersing the ground transfer of the upper load, and uneven settlement. And improve ground bearing capacity. In the event of an earthquake, a block that fits into the internal space is a pair of upper and lower sliding seismic isolation structures, so that it can follow the relative displacement between the building and the ground within a certain range,
A series of basic mechanisms to provide a seismic isolation function for damping and relaxing the dynamic response of the upper structure.

[0007] In order to enable the function of the above-mentioned laminated foundation,
FIG. 4 shows that the blocks to be fitted are in line with the adjacent laminated blocks in eight vertical directions in conformity with the shape of the internal space of the laminate formed by stacking the laminated blocks.
And (4) a laminated block characterized by a shape having a truncated cone on both the upper and lower sides and having a small step in the middle, and a pair (3) which is a fitting block and has a truncated cone shape as shown in FIG. Use a seismic isolation block. This seismic isolation block enables a certain range of sliding and vertical rotational displacement following the deformation of the internal space during an earthquake.

[Structure, Function and Function] The stacking foundation of the present invention is characterized in that, between the stacking stages for stacking the truncated cone-shaped blocks, blocks of matching shape are inserted and sandwiched in the plane row and the internal space of the row, and the empty space is formed. This is to stabilize the stacking structure in a series. Now, when the ground at a certain point and the lower layer of a certain laminated block are about to subside, the downward transmission of the load from the laminated block of the immediately upper layer is carried out through the four embedded blocks at the outer periphery of eight blocks. Is dispersed to other lower step blocks, and thereafter, the load is dispersed over a wide area sequentially in the outer edge direction, and uneven settlement is suppressed.

In general, when the ground is a rigid body and the ground is a viscous soil, the ground reaction force at the ends increases due to plastic deformation in the central ground. On the other hand, in the case of loose sandy ground, the reaction force in the central part tends to increase, and it is known that any of these causes uneven settlement. In these cases or when the ground strength is locally inferior, the laminated foundation of the present invention is effective for dispersing and equalizing the load even if the upper footing is rigid.

[0010] The lower half-cone portion of the lower layer of the laminated block is in contact with the backfill soil (fine-grained gravel) and is in contact with the ground. However, from the vertical load, the component force along the conical surface and the vertical direction to the conical surface are obtained. This vertical component contributes to increase the horizontal compressive principal stress (minimum principal stress) in the ground through the backfill soil, and consequently the maximum vertical force in the ground. The "shear force" generated by the difference from the main stress is reduced. This means that the compressive force in the diagonal direction in the ground by the adjacent blocks restricts the lateral displacement, and the support strength of the ground in view of the shear fracture condition is enhanced. That is, it is possible to expect a bearing capacity under general shear failure conditions (or ultimate shear failure conditions), which are not restricted by local shear fracture conditions such as lateral displacement of the ground and local uplift.

On the other hand, the presence of a rigid block in the internal space impairs the function of seismic isolation which restrains the horizontal displacement of the laminate itself and absorbs and relaxes the relative displacement during an earthquake. This constraint has also been confirmed by a three-dimensional model of the laminate. As a seismic isolation mechanism, the internal space between
The relative displacement between the ground and the upper structure must be allowed to follow the horizontal displacement and the vertical rotational displacement of each surrounding laminated block. As shown by the solid line in FIG. 6, the block stacks stacked in two stages are rotationally displaced within a range of an angle of δ / 2 from the vertical axis, assuming that an inertial force acts on the top during an earthquake. At this time, the cross-sectional profile (the profile connecting the contact lines) of the internal space surrounded by the laminated blocks is changed from a hexagon symmetrical to the center vertical axis of the space in normal times to an asymmetrical hexagon flattened in the oblique direction, At that time, the relative angle of each side in the oblique direction does not change, and the contour cross-sectional area of the space hardly changes even after the displacement.

In view of this, the fitting block to be inserted into the internal space is a seismic isolation device, as shown in FIG. Into two. A slidable bearing ((5) sliding surface) is provided on the upper and lower contact surfaces to secure the required upper and lower gaps and to support the upper seismic isolator with the lower seismic isolator. In the event of an earthquake, as shown by the solid line in the operation comparison diagram in Fig. 6, the vertical axis of each laminated block must be simultaneously and uniformly displaced in the same direction due to the relative displacement between the ground and the upper structure. The pair of seismic isolation blocks works as follows.

First, the pair of upper and lower seismic isolation blocks is limited to Δb determined from the assumed displacement amplitude in accordance with the deformation of the contained space section (the diameter ratio of the seismic isolation block to the basic diameter Φ is also related). ) Follow the relative horizontal sliding of the upper and lower seismic isolation blocks. At the same time, the upper seismic isolation block, with respect to the angular displacement of the contact surface of the peripheral laminated block,
The robot follows the bearing while rotating with the angle of about δ / 2 limited by the clearance Δh around the bearing point (when the lower seismic isolation block does not rotate). At this time, the acting force and acceleration of the dynamic displacement are damped by the sliding friction of the sliding bearings of the upper and lower seismic isolation blocks and the consumption of the lifting gravitational energy, etc., which also contributes to a longer response swing period. It functions as a so-called isolator and as a damper.

Further, in the case of wind force or micro-vibration at any time, the friction acts as an appropriate resistance to suppress unnecessary movement. At the end of the seismic motion, the rotation inclination of the vertical axis of the laminated block is within the stable setting, and together with the self-restoring force due to gravity,
The lift restoring force from the curvature of the concave sliding bearing surface of the seismic isolation block also acts, and returns to the normal position.

[0015]

FIG. 2 and FIG. 3 show a two-layer stack of stacked blocks. For example, when the supporting strength of the ground is insufficient for the load, the laminating end may be stepped to increase the supporting area, or a three-stage lamination may be configured from an assumed response displacement amount or the like. If the seismic isolation function is not necessary due to the relationship between the characteristics of the ground and the natural period of the structure, replace the pair of seismic isolation blocks with one that does not slide in the same form, and that does not separate vertically. Using a block, a laminated “non-seismic type” can be used in which horizontal displacement is suppressed only for the purpose of improving the bearing capacity.

The diameter Φ, which is the basic dimension of the laminated block, is
30 to 60 cm is appropriate from the viewpoint of the scale and construction of the structure. The other dimensions including the seismic isolation block are the basic diameter Φ
Is determined in proportion to As for the material, concrete is appropriate in terms of strength and price, but recycled synthetic resin can also be used. It is appropriate that the sliding bearing portion of the seismic isolation block be embedded with a stamped steel plate or hard synthetic resin in the manufacturing process.

The shape such as the curvature of the sliding surface in the sliding bearing portion of the seismic isolation block is evaluated as an equivalent rigidity and an equivalent damping constant together with the frictional resistance and the like depending on the material of the bearing surface and the processing method. Is appropriately set or selected based on the scale of the building, the natural period characteristics of the structure, and the like. other,
A moving body method such as an ellipsoidal sphere can also be used.

As a point to be noted in the construction, the entire space around the lower half cone of the lower layer laminated block directly laid on the ground is compacted with fine-grained gravel or the like and backfilled. It is desirable that the laminated block at the outer peripheral end of this step be inquired by the embedded laminated block and the shackle at every two locations in the diagonal diagonal direction under the ground condition where lateral displacement is likely. When the footing of the structure is cast, the space above the seismic isolation block is EP
It is covered with S or held by a buried form or the like. In cold regions, the bottom of the footing should be deeper than the freezing depth or the groundwater level should be considered. In addition, backfilling of the outer peripheral end including the structure after the upper half of the lower step block is performed with non-adhesive sand or the like which has little passive restraint.

[0019]

The laminated foundation of the present invention has good sitting stability,
It lays product blocks that have a certain standard size and that are well managed in terms of quality, and can contribute to rationalization of construction without requiring special construction techniques or skills. Conventionally, in the sedimentary ground, as the ground strength of the direct foundation is somewhat inadequate, relying on a long pile foundation suddenly, improvement of the bearing capacity by the laminated foundation of the invention, adjustment of the support area expansion, etc.,
A rational and economic foundation can be built that effectively utilizes the bearing capacity of the sedimentary ground.

At the same time, as a basis for providing a seismic isolation function,
Low construction cost, low temperature dependence and functional deterioration in cold regions compared to rubber-based isolation, no need for subsequent maintenance, and can be widely used for seismic isolation of buildings and civil engineering structures. In particular, in the sedimentary ground, the predominant period of the ground motion is often close to the natural period of the middle and low-rise structures, and the conventional foundation has high dynamic response such as resonance vibration,
By utilizing the laminated foundation of the present invention, the transmission of dynamic energy to the upper structure can be effectively damped and alleviated, integrally with the function of improving the ground support force.

Specific examples of the target structures include reinforced concrete and SRC structural buildings where the natural period is close to the predominant vibration characteristics of the ground in the middle and low layers, steel structures and wooden structures below the middle layer, and exposed water storage. It is an independent structure such as a tank. In cases where the ground motion is difficult to separate from the ground such as buried type such as underground pipelines and gutters or the ground such as retaining walls, or where seismic isolation function is not required, improve the ground support capacity. For a limited purpose, a laminated “non-seismic type” with suppressed horizontal displacement can be applied.

[Brief description of the drawings]

FIG. 1 is a plan view of the laying of a block laminate foundation.

FIG. 2 is a sectional view taken along line a of the block lamination foundation.

FIG. 3 is a sectional view taken along line b in FIG.

FIG. 4 is a diagram (a front view and a plan view) showing the shape of a laminated block.

FIG. 5 is a structural view (a pair of upper and lower front sectional views and a plan view) of a seismic isolation block which is a fitting block.

FIG. 6 is a seismic isolation operation comparison diagram (a sectional view taken along line b). The normal state (shown by broken lines) and the operating state during an earthquake (solid line) are shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single laminated block 2 Set-in block (a pair of seismic isolation blocks) 3 Upper seismic isolation block 4 Lower seismic isolation block 5 Sliding bearing part of seismic isolation block 6 Lower layer backfill soil (fine grain gravel etc.)

Claims (1)

[Claims] 1. A single laminated block characterized by a shape exhibiting a truncated cone on both the upper and lower sides is arranged on an excavated ground, laid in a plurality of layers, and formed between the laminated layers. In the interior space, a block that conforms to the shape of the space is fitted, a stable layering is built, the uneven settlement is suppressed, and the ground support force is improved. A series of block-laying foundations that can be provided with a seismic isolation function that attenuates and relaxes the dynamic response of the upper structure during an earthquake by using a pair of seismic isolation blocks of the type.