Class of Bearings to Protect Structures from Earthquake and Other Similar Hazards
A class of bearings, each of them can be used as a connector to connect two parts in a structural system and as a supporter to transfer loads from one part to another, for examples, gravity of a superstructure to a substructure in a bridge or a building, or that of a machine to its foundation. While performing load transmission, it is able to reduce the transmission of transient vibrations between connected two structural parts and preserve the integrity of entire structural system; for examples, to protect a bridge's structural integrity when either an earthquake strikes its pier and foundation or a tsunami hits its superstructure or both occur simultaneously.
The present invention discloses a class of apparatuses. A said apparatus is used as a structural component in a large-scaled civil engineering system such as a building, a bridge, or a machine and its foundation, which has at least the following three functions: being a support to bear the weight of a part of said system, connecting different parts of the system to assure structural integrity, and transferring designed force-flows other than gravity between connected parts while damping out or isolating undesired vibrations.
For said engineering system like a bridge or a building, it generally can be divided into two parts: the superstructure such as a bridge's spans and deck that carries designed live loads; and the substructure that includes the bridge's piers, footing, and foundation, which supports carried superstructure. Wherein said bearing is a structural component that connects super and substructure, transferring carried superstructure's weight and live loads to substructure
BACKGROUND OF THE INVENTIONAn earthquake is a sudden tectonic-plate's movement at a spot inside earth's crust, radiating stress waves to surrounding and resulting in earth surface's vibrations. To a large-scaled civil-engineering structure, such as a building or a bridge, the lethality of an earthquake mainly comes from the two respects: ground acceleration that causes inertia forces and resonance that accumulates the energy associated with the acceleration in structure. Hence, acceleration-induced internal inertia force is the key factor to cause structural damages.
Ground acceleration can be divided into vertical (parallel to gravity direction) and horizontal component, which are respectively characterized by the corresponding peak values, teamed “Peak Ground Acceleration” (PGA) for design consideration. The horizontal PGA is generally higher than the verticals according to past experiences. Currently in United States the engineering standards and codes of buildings and bridges require all designs with the seismic resistant capacity to sustain the horizontal PGA that is quantified by the earthquake hazard map provided by USGS, see
In seismic resistant design, for example, for bridges, a generally-accepted philosophy is to isolate superstructure from substructure that directly expose to the impact of ground accelerated motion when an earthquake occurs. A bearing, when it connects sub and superstructure rigidly, often becomes the “weakest link” in entire structural system. This is because, as a pivot to carry all live loads and superstructure, a bearing is also the “neck” of inertia-induced force flow when any structural part is struck by dynamic loads. By contrast, when it is a flexible connection that is can temporally separate connected parts when one of them is struck by an external dynamic load, the corresponding high inertia force flow will not be established.
However, in reality it is generally impossible to completely “isolate” inertia force flow between connected parts in a civil engineering structure; the central of seismic-isolation design actually is to provide certain flexibility at the joints between major parts of a structure, so as to reduce inertia force while be able to temporally shift intrinsic resonate frequencies of a structure for avoiding the resonance with ground motions. On the other hand, engineering practice also requires such a joint to have certain robustness because a superstructure has to be able to sustain many different kinds of live loads, for examples, the strong lateral forces caused by hurricane and tsunami. A horrible experience during the earthquake at Mar. 11, 2011 in Japan was that many bridges and buildings were survived after the high magnitude earthquake but their superstructures were washed out by the following tsunami.
Hence, in contrast to conventional isolation, the concept of “integrated design”, which requires certain flexibility at joints and bearings to reduce and damp undesired vibration while be able to keep global structure as an integrated unit, is the underlying fundamental for this invention.
BRIEF REVIEW OF PRIOR ARTS AND PRODUCTS AVAILABLE IN MARKETDesign of seismic-resistant buildings and bridges is one of the most active and innovative areas in the field of civil and structural engineering. Using a three-storage building,
A bearing can be considered as a joint. According to functions, bearing products can be generally divided into three categories: (i) dumper-joints that utilize traditional mechanical devices, such as piston-cylinders damper, cams-pin-friction damper, and so on, for which some modern arts are implemented with shape memory alloys and controlled by electric sensors; (ii) common structural bearings such as elastomeric that has certain enhanced lateral resistance; (iii) the bearings based on friction-pendulum mechanism that focuses on seismic isolation.
Theoretically speaking, a pendulum is a conservative system that does not dissipate energy. Therefore, if there is no friction, an actual pendulum can swing around its static position forever once the motion is triggered. Therefore, friction between the contact surface-pair is also a key-mechanism in a FPS bearing, which requires considerable large contact area to assure enough friction force and capacity for carrying heavy superstructure. On the other hand, certain height of curved surface, at least for the bottom seat of the bearing in
The integrity between sub and superstructure's integrity is crucial for high-rise buildings and the bridges with high structural features. This is because, except those strong external forces such as hurricane and tsunami that directly imposed to superstructure, a horizontal ground motion-induced vibration may cause turnover moment to a superstructure; the magnitude of this moment is approximately proportional to the ratio between a structure's height and the largest one in its length and width dimensions on earth surface.
To gain super and substructure integrity,
According to the literatures search, no prior art has been found of heavy gravity-carrying bearings that has the dual properties in isolation/damping of strong vibrations and preserving structural integrity of a large-scaled civil engineering structure. The U.S. Pat. No. 5,669,189 is a solution toward this class of problems, at least, for light superstructure like family house; however, the design of the tendons and rotation-free fastener system in the art leaves the flexibility in horizontal motion for carried superstructure. This motion leads to less resistance against turnover moment and, once it occurs, the frictions among elastomeric layers become the resistance to prevent the bearing to restore its original shape. On the other hand, the layout of tendon-fasteners system requires relatively large space for the device.
Therefore, in order to provide practically-applicable and effective bearing products for our habilitations and transportation means, this application disclose a new class of apparatuses that can be used as structural bearings that aim at the satisfaction of following criteria:
-
- (A) Robustness: a stable and reliable connection between connected structural parts, for example, super and substructure of a bridge, in regular service condition.
- (B) Fuser: capable to accommodate a temporal separation between connected parts when one of them is struck by a transient accelerated motion that may be caused by earthquake, hurricane, barge or vessel's collision, or explosion, so as to minimize the damage to other parts.
- (C) Integrity: always keep the connected parts as an integrated structural system although temporally localized separation for the purpose of internal isolation.
- (D) Self-restoration: capable to restore original state after performing aforementioned “fuse” function.
- (E) Environment-friendly: does not introduce noise or extra material hazards, nor consumes extra energy during operation.
- (F) Reliability for long-term application and convenience in management.
- (G) Do not introduce difficulties for manufacturing and for field erection and construction.
- (H) Enable quantitative design to meet broad needs, for example, to damp and to isolate the inertia forces cause by the spectrum of ground accelerations predicted by
FIGS. 1 and 2 .
In order to reduce and ultimately prevent possible damages to buildings and bridges caused by broad spectrum of natural disasters, multiple apparatuses with respective independent embodiments or combination of them are disclosed in this article.
The first key-embodiment is the V-shape contact surface-pair, as the core of a class of the disclosed bearings, see
There can be multiple or single or no mate sheet between the top and bottom pads of the bearing in
When multiple mate sheets are desired, it leads to another key-embodiment, i.e. vertically embedded pins, which includes two subclasses: (i) the pin that enhances to the V-shape mate sheets and is made of the material with the yield strength lower than the sheet material but has the capacity for large plastic deformation; (ii) the pin that is made of the material with the yield strength higher than mate sheet material while the two ends of each pin are respectively fastened to top and bottom pads without the flexibility to rotation. The former, termed vertically-laid dissipation pin (VDP) with the major function to dissipate vibration energy. The latter, the high strength pin, does not deal with dissipation but provide additional lateral resistance against vibration and restoration driving force, termed vertical reinforcement pin (VRP).
An advantage for the embodiment of the vertically-reinforced pin (VRP) is that ties connected parts, for example, super and substructure of a bridge, together, whereas the bearing still plays the function for damping. Obviously, the apparatus with VRP satisfies all aforementioned criteria.
The first embodiment is based on the concept of “V-sliding” in
Obviously, the angle α of the V-shape is the key design parameter, which determines the threshold of the lateral force that causes sliding-separation. This force, denoted as Q, results in corresponding stress distribution over both super and substructure, by which the peak value of the stress ratio,
should be limited to an allowable level that will not cause damage, i.e.
where σY is the yielding strength of the material element with the stress σpeak(Q) under the lateral force Q and designed live and dead load; nQ is safety factor and nQ>1. The condition (1) actually assures entire structure without yielding, so the angle α of the V-shape surface-pair is designed by the threshold of allowable impact force, denoted as “QTH”, which is the upper bound of Q to satisfy (1), i.e.:
Now consider an example: a bridge that has four bearings and the total mass of its superstructure and designed live load is represented by the quantity “4M”. Then, QR, the lateral resistance against onset of sliding, is (see
QR=M·g[tan(α)+fr] (3)
where fr is friction coefficient between V-contact surface and mate sheet. According to (2):
QR≦Qth (4)
By substituting (3) into (4) and taking equal-sign, the maximum allowable angle α that satisfies (2) yields:
For the invented V-shape bearings family, the second key design-parameter is the maximum allowable sliding distance l, which is quantitatively determined by applying the second Newton's law. When the bearings are primarily applied to seismic isolation,
to represent the ground motion spectrum in the form of following sinusoidal wave:
So the corresponding inertia-induced lateral force to each bearing of the bridge at the time t is:
Assuming the superstructure starts to slide at the time t0 when Qpred(t)>Qth, at the instance t>t0 its sliding speed is V(t) and the distance traveled is S(t), so
according to the second Newton's law.
Hence, in a VEBSP the superstructure is able to slide its maximum allowable sliding distance IVEBSP along lower V-contact surface within a duration ts-t0 and, then, will be stopped by side stopper that has an equivalent mass Mside and stiffness Kside corresponding to the superstructure's impact induced information. Applying momentum conservation law, Fside, the impact force to the stopper, can be approximately estimated by:
The time tS can be solved by the first equation of (9) when Fside is known, which should be determined based on the allowable stress of the bearing; then using the second equation to determine IVEBSP or verse versa.
Similarly, for a VEB, the requirements to the sliding distance lVEB, which assures that the sliding of a carried superstructure will stop within V-shape contact surface at the time tE, yields:
V(tE)=0 and S(tE)≦lVEB (10)
Substituting the first relation of (10) into (8) determines tE, then, substituting the tE into the second relation of (8) to solve lVEB, which finalizes the basic parameters in a VEB designs.
Design Examples with Additional EmbodimentsIn order to utilize the advantages of elastomer or elastomer-like material for damping and for environmental-friend purpose, for example, reduced noise, a problem to be solved in practice is to minimize the risk of tension instability for this class of materials. This leads to the invention of another sub-class VEB, termed “Multi-V Elastomeric Bearing (M-VEB)”. A design of MVEB is given in
As compared to the VVEB illustrated in
αE is generally smaller than the angles of adjacent facets. This subclass of VEB is termed “360° VEB”. The design examples in
For a VEB (or VEBSP) bearing, for example, that in
For both VEB and VEBSP, appropriated materials should be chosen to manufacture each piece of corresponding apparatus to satisfy the requirements of (i) strength; (ii) fatigue resistance; (iii) friction properties that include specified friction coefficient and wear-resistance; (iv) stiffness, (v) capacity for energy absorption and damping, (vi) corrosion resistance.
Elastomer, the traditional material for bridges' and building's bearings, can also be used as the mate sheet material between the V-shape contact surface-pair, for examples, the prototype in
To avoid the aforementioned drawbacks for this kind of materials while to utilize its beneficial properties, another key-embodiment of this invention is the concept of “vertical reinforcement”, as presented by the bearing prototypes in
As illustrated in
The applicability of the disclosed art has been explained by
- [1] Federal Emergency Management Agency (FEMA), Reports 350-353, 2000
- [2] USGS(United State Geological Survey) website: www.usgs.gov
- [3] California Department of Transportation (Caltran), “The Continuing Challenge: The Northridge Earthquake of Jan. 17, 1994”.
- [4] TRB NCHRP 12-68, Final Report: Rotational Limits for Elastomeric Bearings, 2004.
- [5] AASHTO Guide Specifications for LRFD Seismic Bridges' Design, 2nd Ed., 2011-2012
- [6] Amendment to AASHTO LRFD Bridge Design Specification-4th Ed., Section 14: Joints and Bearings, Caltran, 2010.
- [7] Touaillon J., “Improvement in Buildings”, United States Patents Office, U.S. Pat. No. 99,973, Feb. 15, 1870.
- [8] “Guide Specifications for Seismic Isolation Design”, AASHTO, Third Edition, July, 2010
- [9] “Guide Specifications for Seismic Bridges' Design”, AASHTO, Second Edition, 2011
- [10] “LRFD Bridge Design Specifications”, AASHTO, 5th Edition 2011 revision.
- [11] “California Amendment to AASHTO LRFD Bridge Design Specifications—Fourth Edition (Section 14)”,
- [12] “Experimental Investigation on the Seismic Response of Bridge Bearings”, Univ. of California, Berkeley, EERC-2008-02, 2008.
- [13] Kelly, J. M., 1997, “Earthquake-resistant design with rubber”, 2nd Ed., Springer, London.
- [14] “Rotation Limits for Elastomeric Bearings”, Report 12-68, University of Washington, 2006 (published as report NCHRP 596, 2008). Civil, Structural & Environmental Eng. , University at Buffalo
- [15] Buckle, I., Nagarajaiah, S., and Ferrell, K. 2002. “Stability of elastomericisolation bearings: Experimental study.” J. Struct. Eng., 128(1), pp 3-11.
- [16] Constantinou M. C., and Kneifati, M. C., “Dynamics of soil-base isolated structure system”, Journal of Structural Engineering, ASCE, Vol. 114, No. 1, 1988, pp. 211-221
- [17] Jerry, B. J. and Yuen, W. P. “Seismic Performance and Design of Bridges With Curve and Skew”, FHWA Report, Accession Number: 01080786, 2006
- [18] Cooper J., Friedland I. M., Buckle I. G., Nimis R. B., Bobb N. M., 2009, “The Northridge earthquake: progress made and learned from seismic-resistance design”, FHWA.
- [19] Bazant, B. “Stability of Structures: Elastic, Inelastic, Fracture, and Damage Theories”, Mineola, Dover Pub. 2001
- [20] Galambos V. Theodore, “Structural Stability of Steel Concepts and Applications for Structural Engineers”, John, Willies & Son, 2008
Claims
1. An apparatus that is used as a connector to connect two parts in a structural system while as a supporter to transfer forces from one part to another, for examples, gravity of a superstructure to a substructure in a bridge or a building, or that of a machine to its foundation. As the conventions in this claim and associated claims, a “structural part” refers to a part of said structural system, for example, super or substructure; whereas a component of said apparatus is termed “a piece” or “a piece of said apparatus”.
- Said apparatus can provides robust connection between two connected structural parts when said system is under static load condition or is struck by the dynamic loads under a designed level; it is also able to reduce the transmission of transient vibrations and associated inertia force through relative-sliding in one or multiple V-shape contact surface-pairs in said apparatus when said system is struck by the dynamic loads above said designed level; it also has the capability to self-restore said system's original state after said relative sliding; wherein
- (a) said apparatus comprises at least two pieces along its vertical direction;
- (b) said vertical direction is the direction of the force with the largest amplitude among all said forces transferred by said apparatus under static conditions or the dynamic loads under said designed level; earth gravity is such a force for buildings and bridges; therefore, a horizontal plane of said apparatus is parallel to earth surface;
- (c) said apparatus comprises at least one V-shape contact surface-pair; wherein a V-shaped contact surface in a said surface-pair is concave and formed by at least two facets; whereas another V-shape contact surface is convex and formed by the equal or less number of facets in its counterpart; wherein a said facet is a piece of plane that is not parallel to said horizontal plane of said apparatus;
- (d) said V-shape contact surface-pair in said apparatus, wherein the two V-shape surfaces in a pair can be either bonded together through adhesive or simply overlaid without additional bonding material or separated by single or multiple mate sheets in-between; for the last two cases, a relative sliding along at least one facet pair of said contact surface-pair is permissible;
- (e) said mate sheet contained between two surfaces in a V-shape contact surface-pair; wherein said mate sheet is made of the material selected from the group that includes metal, composite, and elastomer, so as to be able to accommodate relative rotation while no loss of contact occurs within all involved contact surface-pairs when said mate sheet is make by the material that is softer than the material of said V-shape surface-pair, and to adjust contact friction coefficient when said mate sheet contains pre-made cuts to adjust contact area;
- (f) said apparatus comprises at least one V-shape contact surface-pair; wherein the top-most V-shape contact surface belongs to an apparatus' piece that is mounted either directly, or through other pieces, to a superstructure of a said structural system; similarly, the bottom-most V-shape contact surface belongs to an apparatus's piece that is mounted either directly, or through other pieces, to the substructure of said structural system; the super and substructure are connected through all said V-shape contact surface-pairs within said apparatus;
- (g) when said apparatus connects super and substructure of a said structural system for the purpose of seismic isolation while the superstructure's weight is transferred through said V-shape contact surface-pairs to the substructure, the angles between each facet and said apparatus' horizontal plane determines said “designed level” that allows to start temporal sliding when amplitude of a dynamic load is beyond the level, which is quantified according to the peak-ground-acceleration (PGA) predicted by USGS-published earthquake hazard map that is effective at the time for the site of the structural system inside US or by an effective earthquake hazard map published in the country where said apparatus applies.
2. An apparatus that is used as a connector to connect two parts in a structural system while as a supporter to transfer forces from one part to another, for examples, gravity of a superstructure to a substructure in a bridge or a building, or that of a machine to its foundation. As the conventions in this claim and associated claims, a “structural part” refers to a part of said structural system, for example, super or substructure; whereas a component of said apparatus is termed “a piece” or “a piece of said apparatus”.
- Said apparatus can provides robust connection between two connected structural parts when said system is under static load condition or is struck by the dynamic loads under a designed level; it is also able to reduce the transmission of transient vibrations and associated inertia forces in both horizontal and vertical directions through a sliding-pin guided relative-sliding between the two connected parts of said system when the latter was struck by the dynamic loads above said designed level; it has the capability to self-restore the original state said system's after said relative sliding; wherein
- (a) said apparatus comprises at least three pieces along its vertical direction;
- (b) said vertical direction is the direction of the force with the largest amplitude among all said forces transferred by said apparatus under static conditions or the dynamic loads under said designed level; earth gravity is such a force for buildings and bridges; therefore, a horizontal plane of said apparatus is parallel to earth surface;
- (c) said apparatus comprises at least one V-shape contact surface-pair; wherein a V-shaped contact surface in a said surface-pair is concave and formed by at least two facets; whereas another V-shape contact surface is convex and formed by the equal or less number of facets in its counterpart; wherein a said facet is a piece of plane that is not parallel to said horizontal plane of said apparatus;
- (d) said apparatus comprises at least one V-shape contact surface-pair; wherein the top-most V-shape contact surface belongs to an apparatus' piece that is mounted either directly, or through other pieces, to a superstructure of a said structural system; similarly, the bottom-most V-shape contact surface belongs to an apparatus's piece that is mounted either directly, or through other pieces, to the substructure of said structural system; the super and substructure are connected through all said V-shape contact surface-pairs within said apparatus;
- (e) said V-shape contact surface-pair in said apparatus, wherein the two V-shape surfaces in a pair can be either bonded together through adhesive or simply overlaid without additional bonding material or separated by single or multiple mate sheets in-between; for the last two cases, a relative sliding along at least one facet pair of said contact surface-pair is permissible;
- (f) said mate sheet contained between two surfaces in a V-shape contact surface-pair; wherein said mate sheet is made of the material selected from the group that includes metal, composite, and elastomer, so as to be able to accommodate relative rotation while no loss of contact occurs within all involved contact surface-pairs when said mate sheet is make by the material that is softer than the material of said V-shape surface-pair, and to adjust contact friction coefficient when said mate sheet contains pre-made cuts to adjust contact area;
- (g) said apparatus comprises at least one sliding-pin and a means for said guided-sliding; wherein said sliding-pin has two straight parts along its longitude direction; the two parts bend towards each other with the angle that coincides to an angle between two opposite facets in a V-shape contact surface within said apparatus; the transverse section's geometry along one straight part of said pin is designed to fit into a guiding-rail that is built into a piece of said apparatus with one V-shape contact surface in said surface-pair; whereas the section of another straight part of said pin is with designed geometry that is able to sliding through an open-slit in a side-stopper that is a part of or fastened to another piece of said apparatus with another V-shape contact surface in said surface pair; so the sliding-pin is able to move freely along said guiding-rail or through said side-stopper's open-slit or doing the both simultaneously, establishing a sliding-able connection between the two pieces within said apparatus that originally was contacted through V-shape surface-pair but forbid any other relative motions between the pair;
- (h) said apparatus with additional damping core; wherein said apparatus contains at least one cavity; wherein at least one said cavity starts at a point in the apparatus' piece that is with said top-most V-shape contact surface and at least one said cavity ends at the point in the apparatus' piece that is with said bottom-most V-shape contact surface; all the cavities are filled with damping medium that is selected from the group of materials with high capacity of plastic deformation, for example, Lead and Tin, or a mixing of this class of materials.
- (i) when said apparatus connects super and substructure of a said structural system for the purpose of seismic isolation while the superstructure's weight is transferred through said V-shape contact surface-pairs to the substructure, the angles between each facet and said apparatus' horizontal plane determines said “designed level” that allows to start temporal sliding when amplitude of a dynamic load is beyond the level, which is quantified according to the peak-ground-acceleration (PGA) predicted by USGS-published earthquake hazard map that is effective at the time for the site of the structural system inside US or by an effective earthquake hazard map published in the country where said apparatus applies.
3. Said apparatus in claim 1 or 2 with additional vertical reinforcement mechanism; wherein the apparatus comprises at least one vertically-aligned pin; wherein one end of each said vertically-aligned pin is fastened to the apparatus' piece that is or above the piece with said top-most V-shape contact surface; whereas another end of the pin is fastened to the apparatus' piece that is or below the piece with said bottom-most V-shape contact surface; none of vertically-aligned pins is able to rotate freely around either of its ends after fastened to the corresponding pieces of said apparatus
4. An apparatus that is used as a connector to connect two parts of a structural system and as a supporter to transfer loads from one part to another, for examples, gravity of a superstructure to a substructure in a bridge or a building, or that of a machine to its foundation. As the conventions in this claim, a “structural part” refers to a part of said structural system, for example, super or substructure; whereas a component of said apparatus is termed a piece or a piece of the apparatus; a piece or a structural part is a component of the structural system.
- Said apparatus can provides robust connection between two connected structural parts when said system is under static load condition or is struck by the dynamic loads under a designed level; it is also able to reduce the transmission of transient vibrations and associated inertia forces in both horizontal and vertical directions through at least one vertically-reinforced pin between the two connected parts of said system when the latter is struck by the dynamic loads above said designed level; it has the capability to self-restore the original state said system's after said relative sliding; wherein
- (a) said apparatus comprises at least four pieces;
- (b) said vertical direction is the direction of the force with the largest amplitude among all said forces transferred by said apparatus under static conditions or the dynamic loads under said designed level; earth gravity is such a force for buildings and bridges; therefore, a horizontal plane of said apparatus is parallel to earth surface;
- (c) said apparatus comprises at least one V-shape contact surface-pair; wherein the top-most V-shape contact surface belongs to an apparatus' piece that is mounted either directly, or through other pieces, to a superstructure of a said structural system; similarly, the bottom-most V-shape contact surface belongs to an apparatus's piece that is mounted either directly, or through other pieces, to the substructure of said structural system; the super and substructure are connected through all said V-shape contact surface-pairs within said apparatus.
- (d) said contact surface-pair in said apparatus, wherein the two surfaces in a pair can be bonded together by adhesive or they are just overlaid without additional bonding material; for the latter case a relative motion between the two surfaces is permissible; wherein said relative motion between a contacted surface-pair refers to the case that there is difference in displacements between the two surfaces but this difference does not result in loss of contact between all facet-pairs of the contact surface-pair, in other word, at least one contact facet-pair remains contacted;
- (e) said apparatus comprises at least two vertically-aligned pins; wherein one end of each said vertically-aligned pin is fastened to the apparatus' piece that is with said top-most contact surface; whereas another end of the pin is fastened to the apparatus' piece that is with said bottom-most contact surface; so none of vertically-aligned pins is able to rotate freely around either of its ends after fastened to the corresponding pieces of said apparatus.
- (f) when said apparatus connects super and substructure of a said structural system for the purpose of seismic isolation while the superstructure's weight is transferred through said V-shape contact surface-pairs to the substructure, the angles between each facet and said apparatus' horizontal plane determines said “designed level” that allows to start temporal sliding when amplitude of a dynamic load is beyond the level, which is quantified according to the peak-ground-acceleration (PGA) predicted by USGS-published earthquake hazard map that is effective at the time for the site of the structural system inside US or by an effective earthquake hazard map published in the country where said apparatus applies;
- (g) said apparatus with additional damping core; wherein said apparatus contains at least one cavity; wherein at least one said cavity starts at a point in the apparatus' piece that is with said top-most V-shape contact surface and at least one said cavity ends at the point in the apparatus' piece that is with said bottom-most V-shape contact surface; all the cavities are filled with damping medium that is selected from the group of materials with high capacity of plastic deformation, for example, Lead and Tin, or a mixing of this class of materials
Type: Application
Filed: Nov 2, 2012
Publication Date: Oct 30, 2014
Inventor: Su Hao (Irvine, CA)
Application Number: 14/359,120
International Classification: E04H 9/02 (20060101);