FRICTIONAL NON ROCKING SEISMIC BASE ISOLATOR FOR STRUCTURE SEISMIC PROTECTION (FNSI)

Abstract

Frictional Non Rocking Seismic Base Isolator For Structure Seismic Protection (FNSI) is a seismic protection isolator installed under foundations or columns of a building or other structure.

Description

GENERAL CHARACTER

This invention falls into 2^nd category of seismic protection devices which have 2 main categories; 1^st category damps seismic forces transferred to a protected structure thereby and 2^nd category isolates the structures from seismic forces by transferring fraction of seismic forces to the structure, due to smooth contacted surfaces of the seismic isolators.

DESCRIPTION OF THE RELATED ARTS

Frictional Non Rocking Seismic Base Isolator For Structure Seismic Protection, FNSI, is developed from an existing art named Earthquake Protective Column Support that is invented in 1987 by Zayas Vector A. However, FNSI functions completely different from Mr. Zayas seismic isolator. In addition, search for prior arts gives the following other relevant patents:

U.S. Pat. No. 4,644,714	Feb. 24, 1987	06/803895	Zayas; Victor A.
U.S. Pat. No. 7,338,035	Mar. 04, 2008	E04H 9/02	Tsai; Chung-Shien
U.S. Pat. No. 7,716,881	May 18, 2010	E04H 9/02	Tsai; Chung-Shien
U.S. Pat. No. 7,814,712	Oct. 19, 2010	E04B 1/98	Tsai; Chung-Shien
U.S. Pat. No. 8,122,651	Feb. 28, 2012	E04B 1/98	Tsai; Chung-Shien
U.S. Pat. No. 8,161,695	Apr. 24, 2012	E04B 1/98	Tsai; Chung-Shien
U.S. Pat. No. 8,307,586	Nov. 13, 2012	E04B 1/98	Tsai; Chung-Shien
U.S. Pat. No. 8,365,477	Feb. 05, 2013	E04B 1/98	Tsai; Chung-Shien

The main characteristics and disadvantages in the prior arts above are summarized as follows,

• • 1—The Earthquake Protective Column Support (EPCS) rocks like a pendulum under seismic forces, where its own frequency depends on the vertical radius of the concave base. As a result resonance is possible in an EPCS isolated structure when EPCS period is equal to the exciting force period. Resonance results in detrimental effects on the isolated structures. Moreover, when exciting frequency<1.4 of EPCS frequency, the EPCS starts to amplify the exciting forces instead of attenuating them.
  • 2—EPCS contacted surfaces are limited in their low friction coefficients, to values allow the EPCS to withstand horizontal wind forces without rocking under wind forces, which usually is not acceptable. This limitation on friction coefficients of contacted surfaces, result in higher forces transferred to the structure and subsequently, it results in higher costs to reinforce the structure for transmitted seismic forces and might render EPCS less efficient and less competitive than other counterpart devices.
  • 3—EPCS causes high stresses on the contact surfaces that cause maintenance problems to assure functionality at the time of a seismic event occurs.
  • 4—It has so high response displacements result in higher costs in manufacturing EPCS devices.

The 7 Shock Suppressor patents by Chung-Shien Tsai, mentioned above, reveal Shock Suppressors which have serious instability arrangments/failure mechanisms/restricted and limited responses render them unsable as explained in the following,

• • 1) U.S. Pat. No. 7,338,035 restricts responses to random exciting forces including seismic forces, to only 2 perpendicular directions along 2 arcuate sliding channels, while for all other exciting force directions, the exciting forces are transmitted much higher than in the perpendicular 2 directions. In addition, cylindrical roller supports or Rods, (16A), only resist vertical forces. However, seismic forces, and all random vibrations, in practical world, have horizontal components which render Mr. Tsai device unstable and susceptible to failure at any time.
  • 2) U.S. Pat. No. 7,716,881, similarly, restricts responses to random exciting forces, to 2 perpendicular directions only, as explained in 1 above. However, this device has different instability mechanism located in the arcuate face, (112B) which causes the structure fixed to top plate, (14A) to tilt during responses, which might cause immediate failure.
  • 3) U.S. Pat. No. 7,814,712, similarly, restricts, the responses to random exciting forces, to 2 perpendicular directions only, as explained in 1 above. Nevertheless, this device has a third mechanism failure called “3 hinges located at one straight line” at the Connection Device, (20) which comprises First Slider, (21) and Second Slider, (22), which consist 3 hinges on one vertical line. This failure mechanism is well known, and causes immediate failure.
  • 4) U.S. Pat. No. 8,122,651; U.S. Pat. No. 8,161,695; U.S. Pat. No. 8,307,586, and U.S. Pat. No. 8,365,477 have the same 3^rd failure mechanism explained in 3 above. This failure mechanism can be recognized easily in these last 4 patents. Nonetheless, these last 4 patents reveal Shock Suppressors which might response to random excitement in any direction because they have concave base plates. Then the period of response (if they can move and the failure mechanism is assumed doesn't exist) is independent from exciting force period, which, in reality is attributed and first revealed by Victor Zayas in U.S. Pat. No. 4,644,714.

Innovative Ideas Associated Solely with FNSI, are

The main innovative parts in the FNSI are the Rotating Anvil, (RA) and its connection to the Hook. Those parts make the FNSI non-rocking seismic isolator during seismic excitement, and leads to the following results,

RA responds to SH horizontal excitements by rotating around the center of the Hook convex or concave and by vertical movements depends on the difference in levels between current location on, and the lowest point of the SH concave. In addition, the RA convex, normally doesn't slide above the SH concave, because the contacted surfaces of the SH and the RA bottom convex are 2 similarly curved surfaces, which generate reactions to horizontal forces, along the common edges of the SH concave and RA bottom convex. Those reactions are normally opposite in direction and almost equal in values to tangential forces to cause sliding.

FNSI responds, mainly, with vertical movements, with negligible horizontal displacements, which result in much more effectiveness of the seismic isolation, because the vertical response forces are, usually, accommodated by the structure. That because, normally, materials resistance for short term loads increase about 20% more than for static loads.

Resonance is not possible with structures isolated by FNSI that because the RA does not rock and does not have a self-period or frequency.

FNSI does move due to wind exciting forces, because the RA contacts the SH along, comparatively, large spherical surface which generates horizontal reactions to horizontal forces, at the SH, along mutual contact lines of the RA and SH, regardless effects of gravity which, its projection on the tangential direction to the SH concave consists the returning force to the original location, and which resists movements away from the original lowest point.

Contact stresses of FNSI isolator are less than Zayas isolators, then maintenance becomes less demanding.

FNSI reduces horizontal forces because it has very smooth contacting surfaces of sliding parts, as smooth surfaces as can be made by the industry, because wind does not affect FNSI. This high smoothness can be achieved by using solid lubricants that include but not limited to Disulfides Molybdenum, MOS2. Other lubricants may be used to have these surfaces smooth.

Although FNSI has very smooth contacted surfaces at RA bottom disk, SH concave, and the small concave and convex at the top of the RA and Hook; FNSI is stable in operational and non-operational settings because it resists all forces affect the superstructure in three main perpendicular directions including horizontal wind forces.

FNSI isolator is used for very strong diverse and different frequency earthquakes, that because of very smooth contacted surfaces which highly decreases the transmitted forces.

SYSTEM FULL DESCRIPTION AND FUNCTION

FNSI Description,

Frictional Non-Rocking Seismic Base Isolator for Structure Seismic Protection or FNSI which is installed between structures and ground, so that earthquake motions are transferred only through said FNSI to the structures. An FNSI comprises,

• • a) A Sliding Hammer (SH) which is a disk has top smooth concave surface and bottom flat surface fixed to ground which might be a source for earthquakes, or fixed to other source of vibrations.
  • b) A Rotating Anvil which is 2-convex, arrangement connected rigidly through a cylindrical neck, wherein bottom convex of the arrangement has similar radius to the SH concave and the bottom convex of the RA is large enough so that it doesn't slide over the SH due to exciting forces on the RA transferred from the Hook. That because of horizontal reaction forces created partially or completely at the peripheries of the contacted surfaces of the SH and RA. The reaction horizontal forces are almost equal to horizontal exciting forces. The other top convex of the arrangement has comparatively smaller radius than the bottom convex, and said arrangement situated between the upper face of said SH concave and the lower face of an upside down concave centered at bottom of
  • c) a Hook wherein the upside down concave has a radius similar to top small convex of the RA, and is connected rigidly and centered to the bottom of the Hook which is essentially a disk has flat top surface which is connected to the structure which is isolated by the FNSI.

In a second embodiment of the FNSI, the RA bottom convex has 2 or more different radii, wherein a central part of the RA bottom convex has a radius equals to the radius of the SH and surrounding parts have gradually and slightly smaller radius than SH to allow increasingly widening tapered space between the SH and the bottom convex of the RA.

In a third embodiment of the FNSI, the RA has convex-concave arrangement connected rigidly through a cylindrical neck, wherein bottom convex of the arrangement has similar radius to the SH concave and the bottom convex of the RA is large enough so that it doesn't slide over the SH because of the same reason stated in b) above. The top concave of the arrangement has comparatively smaller radius than SH radius, while the Hook, in this embodiment, has upside down convex fits into the top concave of the RA, and the upside down convex is connected rigidly to, and centered at the bottom of the Hook disk which supports and connected to the structure, which is isolated by the FNSI.

In a fourth embodiment of the FNSI, the RA has convex-concave arrangement connected rigidly through a cylindrical neck, wherein the bottom convex of the RA has 2 or more different radii, wherein a central part has a radius equals to the radius of the SH and surrounding parts have gradually and slightly smaller radius than SH to allow increasingly widening tapered space between the SH and the bottom convex of the RA. The bottom convex of the RA is large enough so that it doesn't slide over the SH, for the same reason stated in b) above. The Hook has upside down convex fits into the top concave of the RA. The small radius of the top concave of the RA increased gradually and slightly and towards the edges of the small concave to allow for tapered space with the convex of said Hook which is connected centrally and rigidly to bottom of Hook which is essentially a disk with a flat top surface which supports and connected to the structure which is isolated by the FNSI.

FNSI Function

FNSI functions as seismic or vibration isolator by placing the FNSI between the structure and ground, normally under columns or footings, one FNSI under each column or foundation. Normally there is no other connection allowed between the structure and ground other than the FNSIs.

In an operational setting, any movement of the SH due to ground motions in an earthquake, results in turning the RA around the center of its top small convex or concave, which does not coincide with the rotation center of the SH, and simultaneously moving vertically causing the structure to vibrate, mostly, vertically instead of rocking horizontally. Due to high smoothness of contacting surfaces of SH, RA and the Hook convex or concave and due to Rotation of RA, the transmitted horizontal forces are, normally, close to zero.

As a result, the FNSI responds mainly with vertical movements and very small or no horizontal displacements with jerk movements around the Hook.

The RA, normally, does not move when wind forces affect isolated structure by means of FNSI, wherein the wind forces push, normally, horizontally the structure, which pushes the top convex or concave of said RA, which pushes the bottom convex which touches the SH concave completely or partially. The SH, reacts, normally, with horizontal forces equal to the wind exciting forces, and the reaction forces of the SH are not initiated if the wind forces less than frictional forces between the SH and the bottom Convex of the RA.

The RA stays, normally, at the lowest location of the SH concave when the SH is not exited by a ground motion, wherein the gravity loads of the structure act on the SH via the RA contacted surfaces. Then the SH reacts with forces normal to the SH surface and equal to the normal components of the gravity to SH surface. While the tangential components of the gravity forces push the RA downwards towards the lowest point of the SH, wherein the fractional forces resulted from the normal components of the gravity acting on the SH concave, are normally very small because of high smoothness of the contacted surfaces of the SH concave and RA convex.

As a result, FNSI might be used to isolate structures including but not limited to buildings, bridges, silos, factories and other structures, being made of concrete, steel, wood or other materials, from earthquake effects, or other structures from random vibrations, by means of its smooth contacted surfaces which reduce or eliminate the transmitted seismic horizontal forces to superstructures.

SH concave has, at least, two radii, vertical radius and horizontal radius. Vertical radius is calculated from the requirements for self-returning to a stationary position at the lowest point of the SH concave, while the horizontal radius is calculated from the largest displacements expected in a region, due to an earthquake. Horizontal radius is slightly larger than the largest earthquake displacement.

Radius of RA convex equals to vertical radius of the SH concave as shown in FIG. 1A and FIG. 2A. In another embodiment, RA bottom convex has a central part which has a radius equals to the radius of the SH and the surrounding parts of the RA bottom disk have slightly smaller radii than SH to allow small tapered space which provides for smooth rotation of the RA about the small convex or concave of the Hook, as shown on FIGS. 1B and 2B.

When one side of SH moves, in the first quarter of SH period, towards RA bottom convex, that is situated in its stationary position at the lowest point of the SH Concave, SH forces the bottom disk of RA to rotate around RA top concave or convex, and at the same time, pushes up the whole isolated structure. When the SH, in its second quarter of its period, moves away from said RA that moved already to a higher location of said SH Concave, the RA starts to slides down towards the lowest point of said SH concave because of gravity loads of the isolated structure.

Flexible connections with the main sanitary, water pipes and other utilities are required along with sufficient spaces around those connections and enough horizontal spaces between ground boundaries which might be vertical retaining walls and the FNSIs. Horizontal radius, (Rh) of the SH is greater than the greatest design earthquake horizontal displacement expected in the region in order to eliminate seismic induced damages due to collisions between isolated structure or building with surrounding boundary or retaining walls. The Rh of the SH is estimated from the largest possible displacements under seismic forces or other applicable vibration source.

DRAWINGS' BRIEF DESCRIPTION

FNSI parts are illustrated in FIGS. 1 and 2. The numbers in these figures are as follows,

• • 1) Sliding Hammer, (SH) which is essentially a concave base, number 1 in FIGS. 1 and 2.
  • 2) Rotating Anvil (RA) that has a bottom spherical disk connected to another small convex, as in FIG. 1, or to a concave, as in FIG. 2, via a cylindrical neck. The cylindrical neck is situated at the center and top of the RA bottom disk.
  • 3) Hook, is a disk consists of flat surface on the top and a cylindrical neck fixed centrally to the bottom of the Hook disk and connected to a concave, as in FIG. 1, or a cylindrical neck fixed centrally to the bottom of the Hook disk and connected to a convex, as in FIG. 2.
  • 4) Ground footing or ground.
  • 5) Isolated structure column or foundation.

DRAWINGS

FIG. 1-A, Section in 1^st embodiment of FNSI.

FIG. 1-B, Section in 2^nd embodiment of FNSI, Convex-Convex arrangement incorporates tapered space between the SH and RA bottom convex.

FIG. 2-A, Section in 3^rd embodiment of an FNSI.

FIG. 2-B, Section in 4^th embodiment of an FNSI, Convex-Concave arrangement incorporates tapered space between the SH and RA bottom convex.

Claims

1. frictional non rocking seismic base isolator for structure seismic protection or FNSI which is installed between a structure and ground, so that earthquake motions transferred only through the FNSI to the structure, comprises, a) a sliding hammer (SH) which is a disk has top smooth concave surface and bottom flat surface fixed to ground,b) a rotating anvil (RA), which is 2-convex, arrangement connected rigidly through a cylindrical neck, wherein bottom convex of the arrangement has similar radius to the sliding hammer concave, and is large enough so that it, normally, does not slide over the sliding hammer due to horizontal forces affect the bottom convex, due to horizontal reaction forces created partially or completely at the peripheries of the contacted surfaces of the SH and RA, and wherein the other top convex of the arrangement has comparatively smaller radius, and wherein the arrangement situated between the upper face of the SH concave and the lower face of an upside down concave fixed centrally at bottom of,c) a hook which is a disk, has flat surface at the top, and wherein the upside down smooth concave has a radius similar to top small convex of the RA, so that the RA small convex fits into the hook concave and can rotate around its own center which is, normally, coincide with the center of the hook upside down concave and wherein the hook upside down concave is connected rigidly and centered at the bottom of the hook disk which is connected to the structure isolated by the FNSI.

2. another embodiment of the FNSI as defined in claim 1, wherein the RA bottom convex has 2 or more different vertical radii, wherein a central part of the bottom convex has a radius equals to the radius of the SH and the other surrounding parts of the bottom convex have gradually and slightly smaller radius than SH to allow increasingly widening tapered space between the SH and the bottom convex of the RA.

3. a third embodiment of the FNSI as defined in claim 1, wherein the RA has convex-concave arrangement connected rigidly through a cylindrical neck, wherein bottom convex of the arrangement has similar radius to the SH concave and the bottom convex of the RA is large enough so that it, normally, does not slide over the SH, due to horizontal reaction forces created partially or completely at the peripheries of the contacted surfaces of the SH and RA, and the top concave of the arrangement has comparatively smaller radius than SH radius, and wherein the hook has bottom upside down convex fits into the top concave of the RA, and the upside convex is connected rigidly to and centrally to the bottom of the hook disk which supports and connected to the structure, which is isolated by the FNSI.

4. a fourth embodiment of the FNSI as defined in claim 1, wherein the RA has convex-concave arrangement connected rigidly through a cylindrical neck, wherein the bottom convex of the RA has 2 or more different vertical radii, and wherein a central part has a radius equals to the radius of the SH and surrounding parts have gradually and slightly smaller radius than SH to allow increasingly widening tapered space between the SH and the bottom convex of the rotating anvil, and wherein the bottom convex of the rotating anvil is large enough so that it does not slide over the SH, due to horizontal reaction forces created partially or completely at the peripheries of the contacted surfaces of the SH and RA, and wherein the hook has upside down convex fits into the top concave of the rotating anvil wherein the small radius of the top concave of the rotating anvil increased gradually and slightly towards the edges of the small concave to allow for tapered space with the convex of said hook and wherein the convex of the hook is connected rigidly and centered at the bottom of the hook disk which has a flat top surface to support and connect to the structure which is isolated by the FNSI.

5. a method to protect structures from earthquakes, or other sources of vibrations, by using the: FNSI as defined in claim 1, 2, 3 or 4 by placing the FNSI between the structure and ground, normally under columns or foundations, one FNSI under each column or foundation, wherein, normally, no other connection between the structure and ground other than the FNSIs.

6. A method to operate each FNSI as defined in claim 1, 2, 3 or 4 wherein any movement of the SH due ground movement in an earthquake, results in rotating the RA around the center of its top small convex or concave, simultaneously with moving up vertically which causes the structure to vibrate, mostly, vertically instead of rocking horizontally, due to high smoothness of the contacting surfaces of the SH, RA and Hook convex or concaves and due the Rotation of the RA around the center of Hook bottom convex or concave, which does not coincide with the center of SH which.

7. The RA as defined in claims 1, 2, 3 and 4, normally, does not move when wind forces affect the isolated structure by means of FNSI, wherein the wind pushes, normally, horizontally, the structure, which pushes the Hook, which pushes the top convex or concave of said RA, which pushes the bottom convex which touches the SH concave completely or partially, and the SH reacts, normally, with horizontal forces which are almost equal to the wind forces, and the reaction forces of the SH are, normally, not initiated if the wind forces less than frictional forces between the SH and the bottom convex of the RA.

8. The RA as defined in claims 1, 2, 3 and 4, stays, normally, at the lowest location of the SH concave when the SH is not exited by a ground motion, wherein the gravity loads of the structure act on the SH via the RA contacted surfaces, and wherein the SH reacts with equal forces to the normal to surface components of the gravity forces, and the tangential components of the gravity forces push the RA downwards towards the lowest point of the SH, and wherein the fractional forces resulted from the normal components of the gravity forces acting on the SH concave, are normally very small because of the high smoothness of the contacted surfaces of the SH concave and RA convex.