JPH0562179B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a foundation for supporting buildings and other structures, and more particularly to a foundation for protecting structures from earthquakes. .

B. Prior Art Modern engineering design experts generally agree that earthquake horizontal vibrations are primarily responsible for damaging buildings. The building is structurally designed to primarily support vertical loads, and the safety factors for static gravity loads and dynamic loads are designed with full consideration of vertical seismic loads. Also, vertical seismic motion is usually not very large and has little effect on buildings.

Severe seismic vibrations occur very close to the epicenter of medium-sized earthquakes and further away from the epicenter of large-scale earthquakes. For example, for a moderate earthquake (Richter magnitude ranging from 5.5 to 6.6) less than 5 miles from the epicenter, the peak horizontal acceleration is
Measurements were made in the range of 50% to 125% g (g is gravitational acceleration). In areas between 5 and 25 miles from the epicenter of a moderate earthquake, peak accelerations range from 10% to
It was 50%g. Although acceleration data in areas near the epicenter of large earthquakes is limited, large earthquakes affect larger areas, have longer durations, and have somewhat larger accelerations.

Building standards stipulate the magnitude and distribution of the minimum horizontal seismic force that general buildings must be designed based on linear elastic conditions. The strength design of buildings to resist dynamic seismic forces using linear elastic methods is well understood and can be satisfied by design using quantifiable standard structural procedures. The minimum horizontal seismic force specified in the building code corresponds to the force generated by an earthquake with a peak acceleration of about 5% g, which corresponds to a relatively small seismic vibration. Designing for larger moderate or severe ground vibrations based on linear elastic strength conditions significantly increases the cost of the structure. Therefore, the building code allows design based on minimum horizontal seismic forces.

But only if the structure is flexible enough to absorb the motion and energy of moderate or severe ground vibrations without life-threatening collapse.

The traditional method when designing a building is
This is done by designing the entire structure with sufficient flexibility and energy absorption capacity to absorb the motion and energy of an earthquake. Traditional approaches to building flexibility depend on distributing inelastic deformations across the structure;
Complicated by large variations in structural shape and configuration of details. The flexibility and energy absorption capacity of structures involves complex interactions of structural elements and loads that are difficult to quantify and clearly design. These complex interactions are best handled through a combination of standard structural shapes and structural design that balances flexibility of element and connection details. The design strength of the building is reduced below the horizontal seismic forces produced by severe seismic motions, based on the flexibility of the building. The reduction in design strength proportional to the seismic force is the reduction factor R. The factor R is difficult to quantify and is usually only approximated. Damage to the building and its contents is expected for moderately severe vibrations, but collapse of the building is avoided.

The flexibility approach is based on the satisfactory performance of standard geometry and flexible buildings during past earthquakes. Most building codes explicitly exclude the application of minimum seismic forces when designing unconventional buildings. Due to the known deficiencies of several conventional earthquake building types, most building design professionals are unable to avoid asymmetric designs, split levels, large discontinuities in structural elements, multi-storey open spaces, flexible ground floors, etc. , sloped structure method, over-perforated shear wall,
It is opposed to structures with extremely glazed exterior walls or complex building and structural elements. With traditional approaches to flexibility, proper implementation and quantification of irregular structures is difficult. The use of an unquantified coefficient R is not appropriate. Building collapse becomes dangerous.
Proper design of unconventional buildings involves individual measurements of the flexibility and energy absorption capacity of the elements and the entire assembly.

Horizontal forces due to severe seismic vibrations are 10 to 20 times greater than the minimum horizontal seismic forces required by building codes.
twice as big. Due to such a large difference, the coefficient R
becomes difficult to quantify, and coefficients R greater than 3 must be investigated and confirmed very carefully. Furthermore, during severe vibrations, considerable damage to structures and non-structural building elements and contents can be expected. These can have serious consequences for facilities that require post-earthquake treatment (hospitals, fire stations, police stations, communication facilities, city administrative centers, etc.). For any building, there is a serious risk of long-term loss of functionality and large-scale losses, which lead to large economic losses. In basic insulation solutions, the structure is supported on equipment that is specifically designed to absorb the motion and energy of seismic shocks. Basic insulation is a conceptually simple solution that is gaining recognition as an effective protection against earthquakes. Unfortunately, previously effective basic insulation systems have been difficult and expensive to install in conventional building structures. In addition, vibration isolators used to isolate equipment from general vibrations typically have a small load capacity, absorb only small amplitude motions, and include vibration isolation from vertical motions.
They often incorporate complex mechanical, liquid, and air support systems, making them impractical for building applications.

Basic insulation systems for buildings that do not have resilience are not sufficient. They have zero frequency response and are susceptible to extremely large displacements. These devices are susceptible to uncontrolled displacement due to ground rotation or tilting caused by ground distortion or subsidence. Devices incorporating independent springs for restoring force tend to be complicated by obstructions that must provide separate means for vertical support while allowing horizontal movement. Active devices in conjunction with electrical feedback and servo control devices are very complex, not sufficiently reliable, and require excessive maintenance.

Reference devices using rubber pad foundations have some limitations, but are useful for building. Current rubber pads employ thin layers of rubber and steel to increase vertical stiffness. These rubber pads absorb horizontal displacements due to shear strains within the rubber layer. The horizontal stiffness of the rubber pad decreases with increased vertical load and increased horizontal displacement, which constitutes an inherent instability characteristic. These instability characteristics limit the horizontal displacement that can be absorbed. The horizontal stiffness characteristics of the pad support system include torsional response motion due to the expected eccentricity between the center of horizontal resistance and the center of gravity of the building. Torsional motion doubles the required displacement and strain that the insulating pad must absorb. It is difficult to accommodate this required strain without exceeding the stability limits of the pad with its actual dimensions. Rubber bearings with sufficient height to absorb large horizontal displacements reduce stability and vertical stiffness. The reduced vertical stiffness creates a rocking mode with a period that is susceptible to amplification, increasing the vertical mode period to a range that is more susceptible to rocking. Local rotation of the connecting plate of the pad adds distortion and instability to the pad. These rotational and horizontal displacement instabilities are controlled by assembling a rigid frame on the pad and a peripheral foundation wall, but this has considerably increased the cost of using this device.

Another type of basic insulator that has useful application, although subject to some limitations, is the roller or rocker bearing. Many modifications for roller or rocker bearing devices are proposed. In general, this device is resilient but has the following practical limitations. That is, the supporting capacity of each roller bearing is limited by the small contact area, which are inconvenient to implement, and they require a separate energy absorption function.

A basic insulating device that has received little recognition or attention is the pendulum device. Some equipment for this type of building consists of a swing frame and a hanging rod with removable mechanisms to restrain small amplitude movements. The sling acts as a pendulum arm, providing lateral movement capacity. However, the rocking frame,
The hanging rod and attachment/detachment mechanism were cumbersome and difficult to implement, limited load-bearing capacity, and had questionable reliability.

Another proposed column foundation for building includes a base suspended by hanger rods. Since the length of the hanger rod is proportioned to be too short and there is no appreciable damping, the device does not work as effectively as proposed. The device is impractical because it cannot easily adjust the pendulum length and swing of the correct ratio, has a low support capacity, is expensive to manufacture, and is complex.

Another foundation system includes an earthquake protection platform for electrical equipment suspended from rigid pendulum links and fitted with viscous dampers. The device has a known and predictable period that makes it useful as a basic insulation device. However, the suspension platform solution is not practical for building. Furthermore, the required length of the pendulum link is approximately 1.2 m or more, which poses practical difficulties in applying it to buildings.

Previously known pivot sliding foundations were not designed in a manner suitable for basic insulation. They have a fulcrum above the sliding surface, have a low load-bearing capacity, and do not include a means to achieve reliable hysteretic friction damping. One such configuration includes a three-point foundation system employing a combination of fixed and sliding foundations. This uncommon basic device is
It was designed to accommodate vertical wavy deformations of the ground and cracks in the ground beneath the building. Two embodiments of the sliding mechanism are used to accommodate the torsion of the ground relative to the base in the horizontal direction, employing a pivoting shoe on a concave surface, which is satisfactory for this purpose. Looks like it's working. A fixed base in one embodiment is used in conjunction with the sliding shoe, and the fixed base absorbs horizontal forces and provides horizontal stability to the shoe base. In another embodiment, the structure includes a rubber-like bushing below the sliding base that absorbs high frequency, small amplitude motion. Rubber pushing serves as an initial base insulation measure when designed to protect sliding shoes from large horizontal inertia forces.

Serious difficulties would occur if the pivot shoe were used without a fixed base and without proper rubber bushings underneath all bases. Shoes are directly subjected to large inertial forces and high-speed displacement movements caused by horizontal seismic vibrations. Because of the height of the fulcrum above the sliding surface, the shoe experiences an overturning moment equal to the product of the horizontal force on the building times the height of the fulcrum above the sliding surface. This overturning moment pushes down the shoe, causing instability and irregular sliding motion.

The design of the pivoting shoe is such that the height of the fulcrum above the sliding surface is in the range of 17% to 33% of the radius of curvature of the sliding surface. Furthermore, when the shoe is in a tilted position, the height of the fulcrum creates a resultant vector of the weight of the building, which is offset toward one edge of the shoe at the fulcrum. This weight shift reduces the stabilizing moment provided by the weight of the building and causes the load-applying edge of the shoe to dig into the support surface. This gouging increases frictional resistance and further serves to knock down the shoe.

The uneven vertical pressure causes a stick-slip phenomenon in sliding motion. Furthermore, when subjected to high speed unlubricated sliding, the surfaces seize together due to the phenomenon of cold welding. Most importantly, the sliding surfaces of the shoe and the concave surface tend to stick to each other after years of high pressure contact and therefore do not slip when needed.

When rocking is large, the supported building undergoes rocking motion. This locking movement causes a temporary rise in individual shots. The shoe itself, after being raised, undergoes a horizontal acceleration movement which rotates the shoe with respect to the building. As a result, the shoe rotates out from under the building, resulting in improper alignment and unacceptable instability when re-contacting the sliding surface.

These constraints apply to pivot sliding platforms where the fulcrum is at a considerable distance from the sliding surface. These limitations in non-lubricated devices are exacerbated when unsuitable materials are used for the friction interior surface. Regarding lubrication devices, it is difficult to maintain sufficient lubrication of sliding surfaces when a non-slip state continues for a long period of time. The height of the fulcrum above the sliding surface also causes horizontal and vertical displacements of the building with respect to the fulcrum and the sliding surface. Therefore, the building exhibits horizontal and vertical motions that do not follow the horizontal and vertical motion relationships that follow the shape of the concave surface.

C. Means for Solving the Problems In one aspect, the present invention provides a foundation for a building or other load. The base has a member with a spherical concave sliding surface having a predetermined center of curvature and a predetermined radius of curvature. The base further includes a load receiving element spaced apart from the spherical concave sliding surface and movable relative to the member and having a spherical recess having a predetermined center of curvature opposite the spherical concave sliding surface. There is. The base further has a convex sliding surface having the same radius of curvature as the radius of curvature of the spherical concave sliding surface, movably sliding along the spherical concave sliding surface, and having a radius of curvature of the spherical concave sliding surface of the load receiving element. The slider includes a slider having a convex articular surface having a center of curvature coincident with the center of curvature and slidably contacting the spherical recess in a tiltable manner. The center of curvature of the spherical recess is set at a position separated from the center of curvature of the spherical concave sliding surface by a distance exceeding 90% of the radius of curvature of the spherical concave sliding surface.

In a preferred embodiment of the invention, the center of curvature of the spherical recess is located on the spherical concave sliding surface of the member.

In another preferred embodiment of the invention, the radius of curvature of the spherical concave sliding surface of said member has a length in the range from 0.9 m to 15 m.

In still another preferred embodiment, a damping member is formed on the convex sliding surface of the slider, and the damping member provides a predetermined friction damping by sliding with the spherical concave sliding surface of the member, and the damping member has a predetermined friction damping effect. It is made of a dry bearing member that has a coefficient of friction.

In yet another preferred embodiment, a compressible viscoelastic member is arranged between the member and the load receiving element to resist relative movement therebetween.

In yet another preferred embodiment, the load-receiving element has first and second vertical extension tubes arranged in a nested manner, and a compressible viscoelastic member is disposed within the second vertical extension tube.

In yet another preferred embodiment, the radius of curvature of the spherical concave sliding surface of the member is larger than the radius of curvature of the spherical recess of the load receiving element, and the height of the slider is greater than the radius of curvature of the spherical recess of the load receiving element. is smaller than twice the radius of curvature of

D. Effect In a platform embodying the present invention, the weight of the load is supported through a slider and a spherical concave sliding surface that translates in relation to the slider in response to ground vibrations. The slider pivots during translation into full contact with the spherical concave sliding surface. The fulcrum on which the slider pivots is located away from the center of curvature of the spherical concave sliding surface by a distance exceeding 90% of the radius of curvature of the spherical concave sliding surface, and is located at the contact surface between the slider and the spherical concave sliding surface, or It's near there. As a result, the slider is inherently stable under all dynamic loads, provides effective hysteretic friction damping, and has high load carrying capacity. The resultant dynamic response of a supporting building or other structure is that of a pendulum. The sliding surface contact pressure between the slider and the spherical concave sliding surface is evenly distributed during sliding, allowing effective hysteresis damping and avoiding digging. The foundation exhibits a reliable and predictable response and has a high load-bearing capacity, so it absorbs seismic motion and energy with high efficiency. The base is mechanically simple;
Easily attached to conventional building structures,
It allows the foundation to stabilize and rotate, and is effective against aftershocks. If the fulcrum is placed on a spherical concave sliding surface, the resultant motion is such that the radius of curvature of the spherical concave sliding surface determines its natural period.

E. Example Earthquake protection foundations have flexible and energy-absorbing column connections that can achieve effective basic insulation. In FIG. 1, a support structure 10 is supported on a support foundation 11 by an earthquake protection foundation. Although only a portion of the fully supported structure is shown in the figure, other portions of the structure may be supported as well. The spherical concave sliding surface 1 is essentially a spherical surface with a certain length of radius of curvature R in FIG. This will be explained in detail later, but the center of curvature of surface 1 is the letter C in Figure 1.
It is expressed as The joint slider 2 has a spherical convex sliding surface 3 with the same radius of curvature R as the spherical concave sliding surface 1 . The convex sliding surface 3 is made for translational movement along the spherical concave sliding surface 1.

The articulated slide 2 consists of a convex sliding surface 3 and all the elements that move as an integral unit with this convex sliding surface 3. The joint slider 2 has a convex joint surface 4 that is a spherical sliding surface. As the articulating slider 2 translates along the concave sliding surface 1, the convex articulating surface 4 rotates the slider 2 about the fulcrum 6. The fulcrum 6 always maintains a constant geometrical position with respect to the slider housing 5. As shown in FIG. 1, the fulcrum 6 is located in the center of the convex sliding surface 3. The slider housing 5 forms part of the load-bearing element connecting the articulated slider 2 and the support column 8. The slider housing 5 has a concave articulation surface. This surface transfers all vertical and horizontal loads of the support structure 10 from the support column 8 to the articulated slider 2.
It is transmitted to the convex articular surface 4 of. Support column 8
is the slider housing 5 and the support structure 1
Rigidly connected to 0. Support column 8 may be of any suitable length and may be an integral part of support structure 10. A structure connection plate 9 and its bolts are illustrated as one possible suitable connection of support column 8 to support structure 10.

Support structure 10, support column 8, and slider housing 5 act as an integral unit with negligible deformation occurring between slider housing 5 and support structure 10. By the rotational movement of the articulated slider 2 with respect to the slider housing 5,
The convex sliding surface 3 comes into full contact with the spherical concave sliding surface 1 during translational movement. Furthermore, the convex sliding surface 3 always remains centered around the fulcrum 6. Therefore, the convex sliding surface 3 is always maintained stably under the weight of the support structure 10.

The spherical concave sliding surface 1 is the inner surface of the dish 12 and is formed into a smooth surface. The plate 12 also has a side surface 13
and a lip 14. A flexible viscoelastic cover 15 is continuously connected and sealed around the lip 14 and likewise around the support column 8. Side 13 and lip 1
4 as well as the dish 12, the flexible viscoelastic cover 15 and the support column 8 constitute a sealing unit which protects the spherical concave sliding surface 1 and the articulation slide 2 from surrounding elements.

The protective cover 16 rigidly protects the viscoelastic cover 15 and is configured for fire prevention. The protective cover 16 is connected to the support column 8 so that it can be removed for inspection purposes and is supported by the lip 14, but is not connected to the lip 14 or to the flexible viscoelastic cover 15.

Pan housing 17 holds pan 12, sides 13, lip 14 and is connected to support foundation 11. The pan housing 17 can be configured in various shapes and configurations depending on the application, and can also be an integral part of the support foundation 11. The horizontal displacement stop 18 forms part of the pan housing which prevents the horizontal displacement of the support column 8 from exceeding a maximum value. The lift stopper 19 is embedded and fixed in the dish housing 17 and is attached to the support structure 1.
A steel cable connected to 0. The inner diameter of the eye of the lifting stopper 19 is larger than the outer diameter of the bolt connecting the eye to the support structure 10. This diameter difference serves to dampen impact forces in the unlikely event that the lift stopper 19 is required.

The main bodies of the articulated slider 2, slider housing 5, support column 8 and connecting plate 9 are economically made from structural steel. Dish 12 and protective cover 16 are economically constructed from stainless steel.
Other suitable strength materials may be used in place of steel for special applications. The viscoelastic cover 15 is made from a viscous elastomer or a synthetic or natural rubber mixture.

FIG. 2 shows details of the articulated slider 2 and slider housing 5. The convex articular surface 4 is part of a complete sphere. Its area is approximately 45% of the area of a perfect sphere with the same radius. The convex sliding surface 3 has a convex spherical shape and a circular periphery. The convex sliding surface 3 becomes the outer surface of the frictional inner layer 20. This layer 20 is mechanically fixed to the body of the articulated slider 2.

The important characteristics of the friction inner layer 20 are that it does not stick to the steel spherical concave sliding surface 1 even after several years of contact without lubrication, and that it has no friction between the speed range of 0 m/sec to 0.9 m/sec. The coefficient should be reliable and the load bearing capacity should be in the range of 70.4Kg/cm ² to 2112Kg/cm ² . The most effective coefficient of friction is in the range 0.05 to 0.2 and should not exceed about 0.4 after several years of non-slip contact. Some suitable materials are selected from dry bearing materials for non-lubricated sliding surfaces of structures such as machines, aircraft, satellites, etc. Such materials are described in tribophysics publications. For example, “Self−
Lubricating Materials for Plain Bearings provides useful material. For different applications, specific material compositions are chosen to obtain the desired coefficient of friction. Two-material compositions suitable for all applications include polytetrafluoroethylene (PTFE) fibers interwoven with reinforcing fibers, PTFE and lead-filled porous bronze.

The bearing inner layer 21 is made of bearing material and is once lubricated before assembly. Lubrication chamber 22 contains sufficient lubricant to lubricate all foreseeable joint movements during the life of support structure 10. The lubricant may be non-altering graphite or silicon based.
Inner seal 23 retains lubricant and creates an airtight seal of the inner articular surface. Outer slider seal 7
are mechanically connected and also provide a continuous seal around the slider housing 5 and the articulated slider 2. The slider seal 7 is an elastic body with irregularities that absorbs joint motion. The extension lip 24 of the articulated slider forms a mounting surface for the slider seal 7 and serves as a rotational stop for the articulated slider 2.

Figure 3 is a cross-sectional view of the foundation viewed from the horizontal plane. The pan housing 17 is constructed from concrete poured into the building site, and it is generally easy to form vertical sides on the outer periphery.
The complete sealed unit, including plate 12, sides 13, lip 14, articulating slide 2, viscoelastic cover 15, protective cover 16, support column 8 and connecting plate 9, is delivered to the construction site as a single pre-assembled unit; It is then fixed in place. Concrete for the pan housing 17 is poured, surrounding and filling the pan unit. The protective cover 16 is delivered,
It is temporarily fixed to the lip 14 for installation and assembly, and then released.

In operation, the seismic protection foundation device reduces the maximum horizontal force transmitted to the support structure below the proportional elastic strength of the support structure. The behavior of seismic protection foundations during large ground vibrations of an earthquake is best illustrated in Figure 1. When the lateral force from the horizontal ground vibration exceeds a critical force level, the support structure 10 moves horizontally with respect to the dish housing 17. The support column 8, slider housing 5, articulated slider 2, and protective cover 16 move horizontally together with the support structure 10. The viscoelastic cover 15 typically extends to accommodate only a few inches of lateral displacement. The viscoelastic cover 15 extends up to twice its original length when absorbing the maximum horizontal displacement. Any desired amount of horizontal displacement capacity can be absorbed by the device.

The support structure 10 is supported by the articulated slider 2 . The large bearing surfaces of the articular surface 4 and the convex sliding surface 3 enable the device to support large structural loads.
It is particularly important that the articulating slide 2 is inherently stable. For any combination of vertical and horizontal forces, the resultant force vector of the structural loads acts perpendicular to the articular surface 4 and passes through the fulcrum 6. No matter what load is applied to the joint slider 2, this resultant vector must have a downward component, and the joint slider 2 cannot overturn. Moreover, it cannot act in contact with the articular surface 4. Furthermore, the frictional force acting in contact with the joint surface 4 (which is small since the surface is lubricated) also acts as a restoring force on the joint slider 2 to resist any overturning rotation. Furthermore, since the resultant force acts through the fulcrum 6 (which is also the center of the convex sliding surface 3), the vertical pressure acting on the convex sliding surface 3 is evenly distributed. This is particularly important to avoid gouging between this layer and the spherical concave sliding surface and to reduce stress and wear on the frictional inner layer 20.

The horizontal/vertical displacement relationship of the support structure 10 is exactly the same as that of the fulcrum 6. The fulcrum 6 is constrained to slide along the spherical surface of the spherical concave sliding surface 1. A fulcrum 6 provided by a spherical concave sliding surface 1
The motion constraint of is the same as that given by the pendulum arm. The pendulum arm has a length equal to the radius of curvature R of the concave sliding surface 1. When the supporting end of the pendulum arm is at the center of curvature of the spherical concave sliding surface 1 and the weight end is at the fulcrum 6, the weight end of the pendulum arm is aligned with the spherical surface exactly on the concave sliding surface 1. restrained from moving. The weight of the structure of the earthquake protection foundation acts on the fulcrum 6, thus demonstrating the equivalence of sliding support and pendulum support. The motion of the pendulum is a function of this motion relationship and the acceleration of gravity g. The friction of the joint slider 2 is equivalent to the friction of a pendulum joint.

The lateral natural period of vibration of the earthquake protection foundation is determined from the pendulum equation below.

T=2π√where, is the length of the radius of curvature R (equivalent length of the pendulum), and g is the gravitational acceleration. This equation is accurate for pendulum motion up to 45 degrees, which is significantly larger than the angle encountered in seismic protection foundations. It should be noted that the period is not determined by the mass or weight of the support structure. This is of particular value in the design of seismic protection foundations, since the lateral period is easily selected by specifying the length of the radius of curvature. Therefore, any supported weight has the same period, all parts of the structure cooperate with each other in vibrating with the same period, and the response of the structure is influenced by changes or redistribution of the weight. do not have.

Furthermore, the horizontal rigidity of each base is as follows.

K=W/ where W is the weight of the structure. This stiffness is therefore directly proportional to weight. This is a major advantage for earthquake protection foundations, since the center of horizontal stiffness always coincides with the center of gravity. Therefore, there are no torsional vibrations. Horizontal displacements occurring in corner foundations of buildings with mass eccentricity are reduced by as much as 50% compared to other base insulation devices with springs or rubber pads. As a result, earthquake protection foundations are particularly suitable for asymmetric structures.

When the fulcrum 6 is placed on the spherical concave sliding surface 1,
The above motion characteristics and stress distribution are precisely satisfied.
The deviation from these properties increases when the fulcrum 6 is located further away from the spherical concave sliding surface 1, either towards or away from the center of curvature C of the spherical concave sliding surface 1. The fulcrum 6 is the center of curvature C
has an adverse effect on gouging and slider stability when located close to the 10% of the length of the radius of curvature of the concave sliding surface until the fulcrum 6 faces the center of curvature C.
(or 50% of the diameter of the convex sliding surface), i.e., approximately 90% of the radius of curvature of the concave sliding surface, and when located away from the center of curvature C, there is a serious adverse effect on the response of the device. give. However, when the position of the fulcrum 6 is moved further away from the center of curvature C, i.e. toward the concave sliding surface,
At a distance from the center of curvature C of more than 90% of the radius of curvature of the concave sliding surface, the normal stress on the connecting edge of the convex sliding surface 3 during sliding becomes greater than the stress on the leading edge. This arrangement distance is 1% of the length of the radius of curvature R (or 10% of the diameter of the convex sliding surface 3).
%), that is, when the fulcrum 6 is separated from the center of curvature C by a distance corresponding to 99% of the radius of curvature of the concave sliding surface, the normal stress on the connecting edge is 10% greater than the stress on the leading edge. . This has the advantage of additional protection against gouging. Minor relocation effects on other properties of the device can be ignored.

The length of the radius of curvature R provides effective protection from a seismic motion range of 0.9 m to 15 m (3 to 50 ft), depending on the frequency characteristics of the input motion. A short radius of curvature is a typical seismic motion on rock;
Suitable for seismic input motions with a dominant period of less than 1 second. Long radii of curvature, as occurs for seismic movements during deep alluvial sediment deposition,
It is suitable for seismic input motions with long natural periods. The selection of the length of the radius of curvature is a function of the pendulum principle and seismic characteristics, and is not determined by the size or weight of the support structure. This applies to conventional structures where the dimensions of the foundation elements are selected as a direct function of the dimensions or weight of the supporting structure;
Significantly different from the design of mechanical or basic insulation elements.

The properties of seismic protection foundations facilitate analytical modeling and prediction of structures by manual calculation or computer analysis. A history loop for horizontal force H versus horizontal displacement Δ is shown in FIG. The critical frictional force becomes μW. μ is the friction coefficient. Most of the damping for seismic protection foundations is friction hysteresis damping. Friction hysteresis damping is equal to the area within the loop.
Friction hysteresis damping is displacement dependent and has the same effect on the dynamic response as hysteresis damping of durable structural elements. However, frictional properties are easier to predict and more reliable than the durability capabilities of various structural shapes. The reversibility of the direction of the frictional forces corresponds to the reversibility of the inelastic yield forces in durable structural elements. The free vibrational response of the device is tightly damped for representative values of the device variables.

At force amplitudes below μW, there is no relative motion on the foundation for the frequency of the input motion. The stable harmonic response of the slider pendulum is such that input vibrations with force amplitudes greater than μW and periods less than To/√2 are absorbed by a reduction in transmitted force and displacement. The maximum force transmitted to the structure is significantly less than the force transmitted to the structure by a rigid foundation connection and significantly less than the force transmitted by a viscous damping foundation insulation device with equal energy absorption. .

The input vibration has a period larger than To/√2,
When the slider has an acceleration amplitude of 1.27 μg or less, the slider damps the transient relative motion and no amplification of the harmonic motion occurs. These long-period ground accelerations
When the amplitude is less than 1.0 μg, there is no relative motion on the insulator. Long-period seismic motions have low acceleration amplitudes. Furthermore, since seismic protection foundations are easily designed to have arbitrary natural periods, the device variables To and μ can be chosen to eliminate all long-period relative motions. In the event of unpredictable high long period vibrations exceeding these levels, the input energy above these levels will be absorbed by viscous damping. Viscous damping is provided by the viscoelastic cover 15, building elements and movement.

The coefficient of friction μ has a certain reliable magnitude due to the particular dry bearing material used for the friction inner layer 20. The magnitude of μ is checked periodically during the life of the structure by simply mounting a tool on the articulated slide 2 and rotating it about its vertical axis. The energy absorption capacity of the friction inner surface layer 20 is several times greater than that required for the most severe of most known earthquakes.

For seismic vibrations with peak accelerations in the range 35% to 125% g, numerical studies using time history computer analysis show that the maximum displacement of slider 2 in the seismic protection foundation is 3.8 for typical equipment variables. to 24cm (1.5 to 9.5

Claims (1)

[Scope of Claims] 1. A member having a spherical concave sliding surface having a predetermined center of curvature and a predetermined radius of curvature, and a relative movement relative to the member at a distance from the spherical concave sliding surface of the member. a load receiving element having a spherical recess freely positioned and having a predetermined center of curvature facing the spherical concave sliding surface; a convex articular surface having a convex sliding surface movably sliding along the sliding surface, having a center of curvature that coincides with the center of curvature of the spherical recess of the load receiving element, and slidingly contacting the spherical recess in a tiltable manner; and the center of curvature of the spherical recess is set at a position away from the center of curvature of the spherical concave sliding surface by a distance exceeding 90% of the radius of curvature of the spherical concave sliding surface. Earthquake protection foundation featuring 2. The earthquake protection foundation according to claim 1, wherein the center of curvature of the spherical recess is located on the spherical concave sliding surface of the member. 3 The radius of curvature of the spherical concave sliding surface of the member is
Earthquake protection foundation according to claim 1, characterized in that it has a length ranging from 0.9 m to 15 m. 4 A damping member is formed on the convex sliding surface of the slider and provides a predetermined friction damping by sliding with the spherical concave sliding surface of the member, and the damping member is a dry bearing having a predetermined coefficient of friction. The earthquake protection foundation according to claim 1, characterized in that it is formed of a member. 5. Claim 1, characterized in that a compressible viscoelastic member is disposed between the member and the load receiving element to resist relative movement therebetween.
Earthquake protection foundations as described in Section. 6. The load-receiving element has first and second vertical extension tubes arranged in a nested manner, and a compressible viscoelastic member is disposed within the second vertical extension tube. Earthquake protection foundations as described in Scope 1. 7. The radius of curvature of the spherical concave sliding surface of the member is larger than the radius of curvature of the spherical recess of the load receiving element, and the height of the slider is twice the radius of curvature of the spherical recess of the load receiving element. Earthquake protection foundation according to claim 1, characterized in that it is smaller than.