BACKGROUND ART In general, an earthquake-proof rubber isolator has a construction of laminated layers, in which elastic rubber layers and steel layers are alternately laminated or lead is inserted between the laminated rubber and steel layers. This earthquake-proof system of the rubber-steel lamination types can show an excellent earthquake-proof performance for horizontal seismic force, but can be resonant with upper structures thereon in the vertical direction due to a stiffness change, thereby causing the structures to be destructed.

In the existing earthquake-proof rubber isolators, namely in a highly damping earthquake-proof system, an earthquake-resistant support (LRB), or an earthquake-proof rubber isolator of the natural rubber group, steel plates and rubber layers are alternately laminated so as to simultaneously perform a vertically supporting function and a function of expansion and contraction.

From the systematic viewpoint, the conventional earthquake-proof rubber isolator undergoes shear deformation when it is subjected to a horizontal force

while supporting a vertical load. That is, a vertically supporting performance of the earthquake-proof rubber isolator and its horizontally resisting performance have influence on each other, and this influence may cause an unexpected result. Especially, in the case of a bridge, when an upper plate of the bridge is contracted and expanded, an earthquake-proof rubber isolator supporting the upper plate of the bridge is horizontally displaced in response to the movement of the upper plate of the bridge. In this case, since the height of the earthquake- proof rubber isolator having a vertically supporting function and a horizontally resisting function which are integrated with each other decreases when the displacement of the earthquake-proof rubber isolator increases, a structure largely shakes as a vertical spring modulus of the earthquake-proof rubber isolator changes according to the horizontal displacement of the structure at the occurrence of an earthquake.

That is, in an earthquake-proof system of a type having an integrate construction, such as an earthquake-proof rubber isolator, the following details should be necessarily considered when the earthquake-proof system is designed. The reason is that a vertical frequency and a horizontal frequency are dependent on each other. Their relationship with respect to a shape coefficient is defined by equation 1 as below.

Equation 1 in which fv, fh, and S mean the vertical frequency, the horizontal frequency, and the shape coefficient, respectively, and can be obtained by the followingformulae,

S=D/(4t) orS=a x b/(2t (a+b)), in which Tv, Th, Kv, g, and W mean a vertical vibration period, a horizontal vibration period, a spring modulus in the vertical direction, a gravitational acceleration, and weight of an upper structure, respectively.

And afso, the vertical spring modulus Kv can be obtained by the following equation 1-1.

Equation 1-1 Kv= E x A/Te In equation 1-1, E is calculated by an equation, E = (3 + 4.935 S2) x G, A is equal to Ao or Ars and Tes G, and S mean an entire thickness of pure rubber, a shear modulus of elasticity, and the shape coefficient, respectively. Further, Ao and Av, meaning sectional areas without and with a shear deformation, respectively, are calculated by the following equations, Ao = 7cD2/4 and Ar = D 2 (o x #/180-sin #)/4, in which e = 2cos-1 (AQ/D) Since A is generally larger than 3Ar, when deformation of a structure due to temperature change and dry shrinkage of concrete causes a shear deformation of the earthquake-proof rubber isolator, the sectional area of the earthquake-proof rubber isolator supporting the structure changes from A to A/3, so that a sectional area, which the earthquake-proof rubber isolator can support, largely decreases, thereby having significant influence on A and the proportional factor, Kv, that is, characteristic values of A and Kv decreasing to one third of the original ones. Due to this reason, it can be understood, as in equation 1, that the vertical spring coefficient changes in every section of the shear deformation. This

means that a real design dimension should be very large in order to enable the earthquake-proof rubber isolator to stably perform its function. Further, in the case where the sectional area of the product increases in order to decrease the mutual dependence in the vertical and horizontal directions as described above, an excessively large shearing stress is generated to have a force transferred to the upper structure according to the following equation 2. Also, it can be understood that the seismic energy is amplified when the seismic energy is transferred through the earthquake-proof rubber isolator to the structure and that the force due to the shearing stress is transferred with a short vibration period similar to the seismic frequency, not with a long vibration period, which is the most important characteristic of the earthquake-proof rubber isolator.

Equation 2 F=GxA Equation 3 F = Cs x W In this case, Cs = AeS,/TB, in which T decreases when the same force is applied. A, W, F, and Ae mean a sectional area of a product, an upper load on the earthquake-proof system, a shearing force generated due to an earthquake, and a maximum ground acceleration coefficient, respectively.

Further, the biggest problem is that, since the earthquake-proof rubber isolator's vertically supporting function and horizontally resisting function are integrated with each other and change dependently on each other, it is nearly impossible to separately design dimensions for the two functions. Moreover, even if the dimensions for the two functions are separately designed, other

additional conditions should be taken into consideration so as to ensure safety against an earthquake.

In terms of manufacturing equipment, since the earthquake-proof rubber isolator should be so designed as to support weight of an upper structure on the earthquake-proof rubber isolator even after the earthquake-proof rubber isolator undergoes the shear deformation as described above, the product of the earthquake-proof rubber isolator becomes excessively large. Consequently, equipment and a mold for manufacturing the earthquake-proof rubber isolator should be scaled up and changed according to type and weight of the structure supported by the earthquake-proof rubber isolator. That is, whenever the earthquake-proof rubber isolator employed in each structure is designed, one product in one mold is manufactured for every standard. Further, the manufacture of this product requires not only an ultra-large press but also several tens to hundreds of molds from standard to non-standard dimensions, accordingly a large capital investment for equipment is required.

In terms of manufacturing process, after all raw materials are prepared, rubber layers and steel plates are alternately laminated and inserted in a mold, and then they are vulcanized for a long period of time by means of a hydraulic press utilizing vapor pressure. For example, in the case of an earthquake-proof rubber isolator having a diameter of 600 mm, when it is manufactured through a vulcanization after an alternate lamination of steel plates and rubber, the vulcanization should be carried out, for at least twelve hours to twenty-four hours under high temperature and high pressure in consideration of the fact that the rubber has an ultra-low heat transmission, to manufacture a product having at least a stable and standard physical characteristic.

In terms of endurance, since rubber takes a great large portion of the volume and the sectional area in the earthquake-proof rubber isolator and since

the earthquake-proof rubber isolator is excessively scaled up, the high temperature and the high pressure applied while the earthquake-proof rubber isolator is manufactured produce another problem, which is fatal to the endurance of the earthquake-proof rubber isolator, that the product's surface and interior have different characteristics from each other.

Moreover, since an excessively large quantity of heat at high temperature and high pressure is applied to the outer surface of the earthquake- proof rubber isolator, the bonding force between the rubber molecules is weakened. Since temperature is slowly transmitted at the interior of the earthquake-proof rubber isolator, the best bonding condition between the rubber molecules is not ensured, so that the physical characteristic of the material is deteriorated. An adhesion force between the rubber and the steel plate also decreases.

In order to manufacture the earthquake-proof rubber isolator having a diameter of 600 mm, the vulcanization should be carried out for at least twelve hours, and at the same time the high temperature of 150°C and the high pressure of 100 to 250 kgf/cm2 should be applied. The result of an experiment has shown that the interior of the earthquake-proof rubber isolator within 10 minutes after the vulcanization was initiated was at 24°C whereas the outer surface of the earthquake-proof rubber isolator was at 150°C. After the earthquake-proof rubber isolator was vulcanized for twelve hours under the high temperature and pressure, the earthquake-proof rubber isolator's outer surface and interior was measured to be at 150°C and at 120°C, respectively. However, when the product was drawn out of the mold after twelve hours passed, the interior of the earthquake-proof rubber isolator did not yet reach 150°C which is a proper vulcanization temperature. Aging has already been in progress at the surface of the product due to this long vulcanization, and the heat at a high

temperature and the high pressure break intermolecular linkages, so that the rubber almost loses such elasticity that it cannot function as an earthquake-proof rubber isolator in use.

DISCLOSURE OF THE INVENTION Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art. An object of the present invention is to provide a combination-type earthquake-proof apparatus capable of preventing the deterioration of an earthquake-proof function, for small-and medium-scaled earthquakes, arising from the integrated vertical load-supporting and horizontal load-resisting functions in the conventional earthquake-proof rubber isolator, capable of smoothly performing an earthquake-proof function even for large- scaled earthquakes, and capable of remarkably reducing an impact force applied to an upper structure in the horizontal direction, especially when a large-scaled earthquake occurs, thereby reducing the costs and time for manufacturing the apparatus.

In order to achieve the object, the present invention provides a combination-type earthquake-proof apparatus disposed between a lower structure and an upper structure so as to cushion a force applied between the lower structure and the upper structure, the apparatus comprising: a lower plate fixed to the lower structure; an upper plate fixed to the upper structure; a vertical load supporting means disposed between the lower plate and the upper plate to support a vertical load of the upper structure and to allow a relative horizontal movement between the lower plate and the upper plate ; and restoring means for elastically connecting the lower plate and the upper plate with each other so as to provide a restoring force for a relative horizontal displacement generated

between the lower plate and the upper plate.

It is preferred that the apparatus further comprises a first slant-surfaced member and a second slant-surfaced member, the first slant-surfaced member being fixed to one of the lower and upper plates and having a first slant surface, the second slant-surfaced member being fixed to the other of the lower and upper plates and having a second slant surface, the first slant surface and the second slant surface being opposed to each other so as to disperse a horizontal shearing force in a vertical direction, and the horizontal shearing force being applied between the upper structure and the lower structure.

It is also preferred that the vertical load supporting means comprises an elastic supporting member disposed between the lower plate and the upper plate to cushion the vertical load of the upper structure and to transfer the vertical load to the lower structure, a first friction plate fixed to one of the upper and lower plates, and a second friction plate fixed to the other of the upper and lower plates, the first and second friction plates being opposed to and in contact with each other so as to enable the first friction plate to slide on the second friction plate when a horizontal shearing force is applied between the upper structure and the lower structure.

It is preferred that the first slant-surfaced member is disposed between the elastic supporting member and the first friction plate, and has a recess in which the first friction plate is received.

It is also preferred that the vertical load supporting means may comprise a first friction plate and a second friction plate, the first friction plate being disposed between the lower plate and the upper plate and fixed to one of the upper and lower plates, the second friction plate being fixed to the other of the upper and lower plates, the first and the second friction plates being opposed to and in contact with each other so as to enable the first friction plate to slide on

the second friction plate when a horizontal shearing force is applied between the upper structure and the lower structure, and the first slant-surfaced member having a recess in which the first friction plate is received.

The vertical load supporting means may comprise a rubber cushion plate fixed in a first recess formed at the lower plate, a vertical load supporting plate having a second recess formed at an upper surface of the vertical load supporting plate, a first friction plate fixed in the second recess, and a second friction plate fixed to a lower surface of the upper plate, the second friction plate being opposed to and in contact with the first friction plate.

According to circumstances, the vertical load supporting means may comprise an elastomeric bearing fixed in the first recess of the upper plate and having a third recess formed at an upper end plate of the elastomeric bearing, the first friction plate fixed in the third recess, and the second friction plate fixed to the lower surface of the upper plate, the second friction plate being opposed to and in contact with the first friction plate.

The apparatus may further comprise a lead column disposed at a central portion of the elastomeric bearing and between the lower plate and the first friction plate, guide pins fixed to the upper end plate of the elastomeric bearing, and guide grooves formed at the lower surface of the upper plate, the pins having upper ends inserted and guided in the guide grooves.

Preferably, a second friction plate has first and second frictional surface sections divided from each other, the first frictional surface section taking a central portion of the second friction plate and having a relatively small frictional force, the second frictional surface section taking a portion surrounding the first frictional surface section and having a relatively large frictional force.

It is particularly preferable that a first friction plate is made from one of high-molecular compounds and fluorine resin, and a second friction plate is

made from stainless steel.

It is also preferred that the restoring means, being one of rubber springs, steel plate-rubber layer lamination springs, steel springs, rubber-steel springs, and compression cylinders, are disposed around the vertical load supporting means at a predetermined distance from the vertical load supporting means.

The apparatus may further comprise a threshold for limiting a relative horizontal movement between the lower plate and the upper plate, the threshold being formed in a path of a horizontal movement of the vertical load supporting plate.

The vertical load supporting means may comprise an elastic supporting member disposed between the lower plate and the upper plate to cushion the vertical load of the upper structure and to transfer the vertical load to the lower structure, a first friction plate fixed to one of the upper and lower plates, and a second friction plate fixed to the other of the upper and lower plates, the first and second friction plates being opposed to and in contact with each other so as to enable the first friction plate to slide on the second friction plate when the horizontal shearing force is applied between the upper structure and the lower structure, and the first slant-surfaced member having a recess for receiving the first friction plate between the elastic supporting member and the first friction plate.

The vertical load supporting means may comprise a first friction plate and a second friction plate, the first friction plate being disposed between the lower plate and the upper plate and fixed to one of the upper and lower plates, the second friction plate being fixed to the other of the upper and lower plates, the first and second friction plates being opposed to and in contact with each other so as to enable the first friction plate to slide on the second friction plate when the horizontal shearing force is applied between the upper structure and

the lower structure, and the first slant-surfaced member having a recess in which the first friction plate is received.

BRIEF DESCRIPTION OF THE DRAWINGS The above object, and other features and advantages of the present invention will become more apparent with reference to the following detailed description in conjunction with the drawings, in which: FIG. 1 is a perspective view of a combination-type earthquake-proof apparatus according to an embodiment of the present invention; FIG. 2 is an exploded perspective view of the combination-type earthquake-proof apparatus shown in FIG. 1; FIG. 3 is a sectional view of the combination-type earthquake-proof apparatus shown in FIG. 1; FIG. 4 is a sectional view of a combination-type earthquake-proof apparatus according to another embodiment of the present invention; FIG. 5 is a sectional view of another combination-type earthquake-proof apparatus modified from the apparatus shown in FIG. 4; FIG. 6 is a sectional view of a combination-type earthquake-proof apparatus according to a third embodiment of the present invention; FIG. 7 is an exploded perspective view of the combination-type earthquake-proof apparatus shown in FIG. 6; FIG. 8 is a sectional view of a combination-type earthquake-proof apparatus according to a fourth embodiment of the present invention; FIG. 9 is an exploded perspective view of the combination-type earthquake-proof apparatus shown in FIG. 8; FIG. 10 is a perspective view illustrating the assembled state of the

combination-type earthquake-proof apparatus shown in FIG. 9; FIG. 11 is a perspective view of a second friction plate employed in the combination-type earthquake-proof apparatus of the invention; FIGS. 12a to 12e are sectional views of several restoring means disposed between an upper plate and a lower plate, according to other embodiments of the present invention; FIG. 13 is a sectional view of a combination-type earthquake-proof apparatus modified from the apparatus shown in FIG. 3; and FIG. 14 is an exploded perspective view of the combination-type earthquake-proof apparatus shown in FIG. 13.

BEST MODE FOR CARRYING OUT THE INVENTION The above and other objects, characteristics, and advantages of the present invention will be apparent from the following description, along with the accompanying drawings, in which the same reference numerals will be given to the same elements.

FIG. 1 is a perspective view of a combination-type earthquake-proof apparatus according to an embodiment of the present invention, and FIGS. 2 and 3 are an exploded perspective view and a sectional view of the combination-type earthquake-proof apparatus shown in FIG. 1, respectively.

As shown in FIGS. 1 to 3, a combination-type earthquake-proof apparatus 100 according to the first embodiment of the present invention generally includes a lower plate 110, an upper plate 120, a vertical load supporting means 130, and a plurality of restoring means 150. The vertical load supporting means 130 is disposed between the lower plate 110 and the upper plate 120 to support a vertical load of an upper structure on the apparatus while

allowing the lower plate 110 and the upper plate 120 to move relatively to each other in the horizontal direction. The restoring means 150 elastically connects the lower plate 110 and the upper plate 120 with each other and provides a restoring force for the relative movement between the lower plate 110 and the upper plate 120.

The lower plate 110 is disposed on the ground or on a pier, and has lower foundation bolts 112 provided at a lower surface thereof. The lower foundation bolts 112 are fixed to the ground or to the pier by means of concrete, and fixedly support the lower plate 110. Therefore, in the case where there exists another fixing means, for example, when metal fixing members are arranged on the ground or the pier, the lower plate 110 can be fixed by such a method as welding, without the lower foundation bolts 112. This is the same in the case of the upper plate 120. As shown, a first recess 114 is formed at an upper surface of the lower plate 110.

The upper plate 120 is fixed to a lower surface of the upper structure or an upper plate of a bridge, and has upper foundation bolts 122 provided at an upper surface of the upper plate 120.

The vertical load supporting means 130 has a rubber cushion plate 132 disposed in the first recess 114 of the lower plate 110. The rubber cushion plate 132 cushions a vertical load of the upper structure. That is, the rubber cushion plate 132 is a kind of elastic supporter. A vertical load supporting plate 134 having a second recess 135 formed on an upper surface of the vertical load supporting plate 134 is disposed on the rubber cushion plate 132, and a first friction plate 136 is fixedly disposed in the second recess 135. In this case, it is preferred that the vertical load supporting plate 134 is made from metal and the first friction plate 136 is made from high-molecular compound or fluorine resin.

As shown, a second friction plate 138 is attached to a lower surface of the upper

plate 120. The second friction plate 138 is an element to be in contact with the first friction plate 136, so as to allow the first friction plate 136 to horizontally slide and thereby allowing the lower plate 110 and the upper plate 120 to move relatively to each other in the horizontal direction when a horizontal shearing force is applied between a lower structure or the ground, to which the lower plate 110 is fixed, and a pier or an upper structure, to which the upper plate 120 is fixed. Therefore, it is preferred that the second friction plate 138 is made from stainless steel, which has a small frictional coefficient. Instead of the construction of the vertical load supporting means 130 as described above, the second friction plate 138 may be attached to the lower plate 110 while the other elements are provided at the upper plate 120.

The restoring means 150 are disposed around the vertical load supporting means 130 and apart from the vertical load supporting means 130 at a predetermined distance. The restoring means 150 elastically connect the lower plate 110 and the upper plate 120 with each other, and function as a kind of restoring spring for providing the horizontally displaced upper structure with a restoring force. As the restoring means 150, a rubber spring 151, a steel plate- rubber layer lamination spring 153, a steel spring 155, a rubber-steel spring 157, and a compression cylinder 159, which will be described later in this specification, can be employed.

FIG. 4 is a sectional view of a combination-type earthquake-proof apparatus according to another embodiment of the present invention.

In the apparatus of FIG. 4, an elastomeric bearing 140 is employed instead of the rubber cushion plate 132 and the vertical load supporting plate 134 shown in FIGS. 1 to 3. That is, in the vertical load supporting means 130 disposed between the lower plate 110 and the upper plate 120 having the lower foundation bolts 112 and the upper foundation bolts 122, respectively, the

elastomeric bearing 140 having a third recess 142 formed at an upper surface of the elastomeric bearing 140 is disposed in the first recess 114 of the lower plate 110, the first friction plate 136 is disposed in the third recess 142, and the second friction plate 138 is provided at a lower surface of the upper plate 120 opposed to the first friction plate 136. The restoring means 150 are disposed around the vertical load supporting means 130 and between the lower plate 110 and the upper plate 120 in the same manner as described above.

FIG. 5 is a sectional view of another combination-type earthquake-proof apparatus modified from the apparatus shown in FIG. 4.

That is, in addition to the construction of the combination-type earthquake-proof apparatus 100 shown in FIG. 4, a lead column 144 is deeply embedded in a central portion of the elastomeric bearing 140 to be assembled in a fourth recess 116 of the lower plate 110, guide pins 148 is fixed to an upper end plate 146 of the elastomeric bearing 140, and guide grooves 124 having a predetermined length are formed at a lower surface of the upper plate 120 opposed to the upper end plate 146. In this construction, the lower plate 110 and the upper plate 120 can move in both directions, the transverse and longitudinal directions of a bridge, with respect to a static load between the lower plate 110 and the upper plate 120, while they can move in one direction, the transverse direction of a bridge, with respect to a dynamic load therebetween. That is, the combination-type earthquake-proof apparatus 100 as shown in FIG. 5 is disposed at both moving ends of a bridge, and has an earthquake-proof performance of preventing a relative displacement between an upper structure and a lower structure in the longitudinal direction of a bridge with respect to an instant load such as a wind load and a seismic load, while permitting a relative displacement between the upper structure and the lower structure in the transverse direction of a bridge, so as to prolong the vibration period and thereby

exhibit an earthquake-resistant performance. Therefore, the combination-type earthquake-proof apparatus of the present invention has both the earthquake- proof performance and the earthquake-resistant performance. Besides, the first friction plate 136, the second friction plate 138, and the restoring means 150 have the same constructions as those described above.

FIG. 6 is a sectional view of a combination-type earthquake-proof apparatus according to a third embodiment of the present invention, and FIG. 7 is an exploded perspective view of the combination-type earthquake-proof apparatus shown in FIG. 6.

As shown in FIGS. 6 and 7, the combination-type earthquake-proof apparatus 100 according to the present embodiment generally includes a lower plate 110, an upper plate 120, a vertical load supporting means 130, and restoring means 150. The vertical load supporting means 130 is disposed between the lower plate 110 and the upper plate 120 to support a vertical load of an upper structure on the apparatus while allowing the lower plate 110 and the upper plate 120 to move relatively to each other in the horizontal direction. The restoring means 150 connect the lower plate 110 and the upper plate 120 with each other elastically or non-elastically according to design conditions, and the restoring means 150 provide a restoring force for the relative movement between the lower plate 110 and the upper plate 120.

The lower plate 110 is disposed on the ground or on a pier, and has the lower foundation bolts 112 provided at a lower surface thereof. The lower foundation bolts 112 are fixed to the ground or the pier by means of concrete and fixedly support the lower plate 110. Therefore, in the case where there exist any other fixing means, for example, when metal fixing members are arranged on the ground or the pier, the lower plate 110 can be fixed by such a method as welding, without the lower foundation bolts 112. This is the same in the case of

the upper plate 120. As shown, the first recess 114 is formed at an upper surface of the lower plate 110.

The upper plate 120 is fixed to a lower surface of the upper structure or an upper plate of a bridge, and has the upper foundation bolts 122 provided at an upper surface of the upper plate 120.

The vertical load supporting means 130 has the rubber cushion plate 132 disposed in the first recess 114 of the lower plate 110. The rubber cushion plate 132 cushions a vertical load of the upper structure. Without the rubber cushion plate 132, the combination-type earthquake-proof apparatus 100 could be broken by even a small vertical impact. That is, the rubber cushion plate 132 is a kind of elastic supporter. A vertical load supporting plate 134 having a second recess 135 formed on an upper surface of the vertical load supporting plate 134 is disposed on the rubber cushion plate 132, and a first friction plate 136 is fixedly disposed in the second recess 135. In this case, it is preferred that the vertical load supporting plate 134 is made from metal and the first friction plate 136 is made from high-molecular compound or fluorine resin. As shown, a second friction plate 138 is attached to a lower surface of the upper plate 120. The second friction plate 138 is an element to be in contact with the first friction plate 136, so as to allow the first friction plate 136 to horizontally slide and thereby allow the lower plate 110 and the upper plate 120 to move relatively to each other in the horizontal direction when a horizontal shearing force is applied between a lower structure or the ground, to which the lower plate 110 is fixed, and a pier or an upper structure, to which the upper plate 120 is fixed. Therefore, it is preferred that the second friction plate 138 is made from stainless steel, which has a small frictional coefficient. Instead of the construction of the vertical load supporting means 130 as described above, the second friction plate 138 may be attached to the lower plate 110 while the other elements are provided at

the upper plate 120. In this case, the first friction plate 136 and the second friction plate 138 facing and contacting with each other enable the lower plate 110 and the upper plate 120 to undergo a relative movement to each other in the horizontal direction, while the vertical load supporting means 130 cushions and supports the vertical load. Of course, the vertical load supporting means 130 may employ various constructions of other types only if it can support the vertical load.

The restoring means 150 are disposed around the vertical load supporting means 130 and apart from the vertical load supporting means 130 at a predetermined distance. The restoring means 150 elastically connect the lower plate 110 and the upper plate 120 with each other, and function as a kind of restoring spring for providing the horizontally displaced upper structure with a restoring force. According to necessity, the restoring means 150 may be separately constructed.

As shown, the combination-type earthquake-proof apparatus 100 of the present embodiment further includes a first slant-surfaced member 170 which has a first slant surface 172 fixed to the lower plate 110 and is disposed around the vertical load supporting means 130.

And also, the combination-type earthquake-proof apparatus 100 of the present embodiment further includes a second slant-surfaced member 180, which has a second slant surface 182, is fixed to the upper plate 120, and is disposed outside of the first slant surface 172. The first slant surface 172 of the first slant-surfaced member 170 fixed to the lower plate 110 and the second slant surface 182 of the second slant-surfaced member 180 fixed to the upper plate 120 are opposed to each other. It goes without saying that the inclined angles of the first and second slant surfaces 172,182 can be selected according to kinds and characteristics of the structure supported by the apparatus.

The first slant-surfaced member 170 and the second slant-surfaced member 180 are important characteristic elements of the present invention, which function not only to limit the horizontal displacement of the upper structure within a predetermined range when a large-scaled earthquake occurs, but also to disperse and transform the horizontal shearing force into a force against gravitational energy of the upper structure, so as to reduce the impact force applied to the upper structure in the horizontal direction. In order to ensure these functions, the second slant-surfaced member 180 should be disposed in a path of horizontal movement of the first slant-surfaced member 170, and the first slant surface 172 and the second slant surface 182 should be opposed to each other.

That is, when a large shearing force is applied between the upper structure and the lower structure due to a large-scaled earthquake, there happens a relative horizontal displacement between the lower plate 110 and the upper plate 120. Moreover, when this displacement becomes larger than a predetermined value, the first slant surface 172 of the first slant-surfaced member 170 and the second slant surface 182 of the second slant-surfaced member 180 come into contact with each other, and then the second slant- surfaced member 180 climbs up the first slant surface 172 of the first slant- surfaced member 170 while it goes on moving in the horizontal direction. That is, the horizontal shearing force is dispersed into a force of horizontally moving the upper structure and a force of vertically supporting the upper structure.

Therefore, a large shearing force or a large impact force is not applied to the upper structure even if the large-scaled earthquake occurs.

FIG. 8 is a sectional view of a combination-type earthquake-proof apparatus according to a fourth embodiment of the present invention, FIG. 9 is an exploded perspective view of the combination-type earthquake-proof apparatus shown in FIG. 8, and FIG. 10 is a perspective view of the combination-

type earthquake-proof apparatus of FIG. 9 in its assembled state.

As understood from FIGS. 8 to 10, the first slant-surfaced member 170 shown in FIGS. 6 and 7 may be integrated with the vertical load supporting means 130, according to necessity. That is, as shown in FIGS. 8 and 9, the first slant surface 172 is formed along an upper circumferential portion of the vertical load supporting plate 134 disposed at the lower plate 110, and the second slant- surfaced member 180 fixed to the lower surface of the upper plate 120 has the second slant surface 182 opposed to the first slant surface 172. In this case, the vertical load supporting plate 134 performs the function of the first slant-surfaced member 170, simultaneously with supporting the vertical load.

The other elements constituting the vertical load supporting means 130, including the rubber cushion plate 132, the first friction plate 136, the second friction plate 138, and restoring means 150 disposed around the vertical load supporting means 130 and between the lower plate 110 and the upper plate 120 to provide a restoring force against the horizontal displacement, respectively are the same as those described above.

That is, the lower plate 110 is fixed to a lower structure such as the ground and the pier by means of the lower foundation bolts 112, and the upper plate 120 is fixed to an upper structure such as an upper plate of a bridge and an upper structure of a building by means of the upper foundation bolts 122. Then, the weight of the upper structure is supported by the vertical load supporting means 130 having the first friction plate 136, the second friction plate 138, and the rubber cushion plate 132, and the restoring force against the horizontal displacement is provided by the restoring means 150 disposed around the vertical load supporting means 130. In this state, when there happens a large relative displacement between the upper structure and the lower structure due to an earthquake, the lower plate 110 and the upper plate 120 undergo a relative

horizontal movement, so that the vertical load supporting plate 134 having the first slant surface 172 formed at the upper circumferential portion thereof comes into collision with the second slant surface 182 of the second slant-surfaced member 180 surrounding the vertical load supporting plate 134. Then, as the first slant surface 172 and the second slant surface 182 come into contact with each other, a part of a horizontal shearing force having been applied between the upper structure and the lower structure functions as a force pushing the upper structure upward. Therefore, the impact force which has been applied between the upper structure and the lower structure in the horizontal direction is remarkably reduced in comparison with the force required for moving the upper structure upward. Of course, a design advantage can be obtained from which the vertical load supporting function and the horizontal restoring function are separated, and a manufacturing advantage can be obtained from which the earthquake-proof rubber isolator is reduced.

FIG. 11 shows a modified example of a second friction plate.

As shown in FIG. 11, the second friction plate 138 provided at the lower surface of the upper plate 120 may include a first frictional surface section 138a and a second frictional surface section 138b which are divided from each other.

The first frictional surface section 138a having a relatively small frictional coefficient is disposed at the center thereof while the second frictional surface section 138b having a relatively large frictional coefficient is disposed around the first frictional surface section 138a. The frictional coefficients can be properly selected by adjusting the roughness of the surfaces. That is, the first frictional surface section 138a has a relatively smooth surface whereas the second frictional surface section 138b has a relatively rough surface, so that they show different frictional forces with respect to the first friction plate 136. In this case, when a small-scaled earthquake occurs, the apparatus so allows a smooth

horizontal displacement as to absorb the seismic force, thereby performing an earthquake-proof function. When a large-scaled earthquake occurs, the horizontal shearing energy absorbed by the second frictional surface section 138b increases, so that the apparatus can limit the horizontal displacement.

The above-described first and second friction plates 136,138 may exchange their fixed positions between the lower plate 110 and the upper plate 120. Moreover, they may not be directly adhered to the lower plate 110 and the upper plate 120, but may be disposed at any other positions between the lower plate 110 and the upper plate 120 as long as they can be opposed to and make slidable contact with each other. And also, it goes without saying that locations of the rubber cushion plate 132, the vertical load supporting plate 134, and the elastomeric bearing 140 may be properly changed according to conditions.

FIGS. 12a to 12e show several examples of restoring means disposed between the upper plate and the lower plate.

That is, based on the usage and surroundings of the combination-type earthquake-proof apparatus 100 according to the present invention, the above- mentioned restoring means 150 can be used by selecting any one from, or in combination with, the steel spring 155 as shown in FIG. 12a, the steel plate- rubber layer lamination spring 153 having alternately laminated rubber layers 153a and steel plates 153b as shown in FIG. 12b, the rubber spring 151 as shown in FIG. 12c, the compression cylinder 159 as shown in FIG. 12d, and the rubber-steel spring 157 having rubber 157a and a steel spring 157b combined with each other as shown in FIG. 12e. Otherwise, other types of restoring springs may be employed as the restoring means. In order to assemble the restoring means 150 with the lower plate 110 and the upper plate 120, upper and lower ends of the restoring means 150 can be made from metal and welded to the lower plate 110 and the upper plate 120, or they may be inserted into holes

formed at the lower plate 110 and the upper plate 120 and coupled therewith by means of bolt coupling.

FIG. 13 is a sectional view of a combination-type earthquake-proof apparatus modified from the apparatus shown in FIG. 3, and FIG. 14 is an exploded perspective view of the combination-type earthquake-proof apparatus shown in FIG. 13.

As shown in FIGS. 13 and 14, a threshold 160 may be preferably arranged, as circumstances require, in the middle of the horizontal movement path of the vertical load supporting plate 134 so as to limit the relative horizontal displacement between the lower plate 110 and the upper plate 120.

The threshold 160 prevents an upper structure mounted on the upper plate 120 from being displaced farther than a predetermined distance, thereby performing an earthquake-resistant function. The threshold 160 may be adhered directly to the lower surface of the upper plate 120 or fixed to the second friction plate 138 adhered to the lower surface of the upper plate 120 as shown in FIG.

9, in such a manner that a side surface of the vertical load supporting plate 134 can come into contact with the threshold 160. The same description as above can be given about other elements including the rubber cushion plate 132, the vertical load supporting plate 134 having the second recess 135 formed at the upper surface thereof, the first friction plate 136 disposed in the second recess 135, the second friction plate 138 provided at the lower surface of the upper plate 120, and the restoring means 150.

Three basic requirements are generally necessary for an earthquake- proof system constituted by the combination-type earthquake-proof apparatus as described above. The most important one of the three requirements is to provide the earthquake-proof system with a horizontal spring function, so that the earthquake-proof system can have a characteristic of smoothly responding to a

shearing force. By this characteristic, the entire earthquake-proof system can have a prolonged vibration period, so as to securely prevent a destructive power of the seismic energy introduced with a short vibration period from being transferred to the upper structure. The second one is to provide the earthquake- proof system with an energy reduction system capable of limiting the relative displacement of the horizontal spring when the upper structure undergoes a shear deformation due to seismic shear energy generated when an earthquake happens. The third one is to provide the earthquake-proof system with stiffness capable of bearing against an ordinary times load, which enables the earthquake-proof system to respond to a dynamic load such as a wind load and a load generated when an automobile is urgently braked.

In addition, the earthquake-proof system should be necessarily provided with a function of supporting a heavy vertical load. Hereinafter, there is provided a theoretical description about the combination-type earthquake-proof apparatus of the present invention.

First, in the combination-type earthquake-proof apparatus of the present invention, restoring shear springs capable of restoring the lower plate 110 and the upper plate 120 displaced relatively to each other to their original positions function as a single system, whose horizontal spring stiffness Ke can be obtained by the following equation 4. That is, the horizontal spring stiffness is obtained by dividing a value, which is obtained by multiplying a shear modulus of rubber at a shear state of one hundred percents by the entire sectional area of a rubber spring, by the entire thickness of the rubber spring.

Equation 4 Ke = G x 7-ArF

In equation 4, G, LA, and T mean a shearing stress in a state the deformation is corresponding to the thickness of the rubber spring (Kg/cm2), the entire sectional area of a rubber spring (cm2), and the entire thickness of the rubber spring (cm), respectively.

Second, in the combination-type earthquake-proof apparatus of the present invention, relative displacement happens between the first friction plate 136 made from a high-molecular compound or a fluorine resin formed at the upper portion thereof and the second friction plate 138 made from steel or stainless steel adhered to the lower surface of the upper plate 120, so that the seismic energy introduced into the structure is transformed into a friction energy by the friction characteristic between the first friction plate 136 and the second friction plate 138. As a result, the seismic force is damped and absorbed.

In general, the damping performance can be obtained by the following equation 5. In the case of the combination-type earthquake-proof apparatus, the damping performance is proportional to the closed area of a hysteresis loop through repetitive experiments while being inverse proportional to a horizontal stiffness and a square of the displacement when an earthquake happens.

Equation 5 ß = A/(2s x Keff x D2) In this case, A is obtained from the equation, A = 4Q (D-Dy) in which A has a unit of ton. cm, and Q is obtained from the equation, Q = 11 x W. The following references,, W, D, Dy, and Keff, mean a frictional coefficient, a weight of an upper structure (ton), a displacement when an earthquake happens (cm), a yielding displacement (cm), and an effective stiffness in an earthquake which is obtained through a combination of the stiffness of the rubber spring and the

frictional force and has a unit of ton/cm2, respectively.

According to the following table 1 as an example, a desired design can be easily achieved by changing the value of stress applied between the fluorine resin and the stainless steel, and a design required by a customer can be effectively and properly selected.

Third, a wind load or a force by an instant braking of an automobile is born by a frictional force between the first friction plate 136 made from high- molecular compounds or fluorine resin and the second friction plate 138 made from steel or stainless steel adhered to the lower surface of the upper plate 120.

Table 1 Formally Published Frictional Coefficient ! frictional stress between fluorine resin and stainless steel coefficient (je.) with oil Without oil 5 N/mm2 0.08 0.08x2 10 N/mm2 0.06 0.06x2 20 N/mm2 0. 04 0. 04x2 at least 30 N/mm2 0. 03 0. 03x2 In the combination-type earthquake-proof apparatus, the vertical load supporting function is carried out by an elastomeric bearing or a rubber plate, and the restoring means 150, namely restoring springs, constitute a system, which has nothing to do with an effective sectional area for supporting the vertical load when an earthquake happens. Further, even when elements such as the rubber spring 151, the steel spring 155, and the compression cylinder 159 have been broken, the vertical load supporting function is still carried out.

Therefore, it is preferred that the apparatus is so designed as to support three times of the vertical load.

In addition, when the earthquake-proof apparatus of the present invention is installed to a bridge, necessarily required is a rotation generated due to a deflection of the bridge itself or a rotation with respect to an instant braking load of an automobile. In this case, the energy with respect to an instant braking load of an automobile or the rotation of an upper structure of a bridge can be easily absorbed by adjusting the restoring springs, and the frictional coefficient and the thickness of the elastomeric bearing or the rubber plate.

INDUSTRIAL APPLICABILITY As apparent from the above description, the combination-type earthquake-proof apparatus according to the present invention, which can be designed in accordance with various conditions, remarkably reduces time and labor required for manufacturing the apparatus.

In the combination-type earthquake-proof apparatus according to the present invention, rubber, which requires a relatively long manufacturing time, can be minimized, so that the vulcanization time can be reduced from twelve hours of the prior art to about thirty minutes, thereby enabling the apparatus to be manufactured at low cost.

In the combination-type earthquake-proof apparatus according to the present invention, an irregular rubber portion, which requires quality control, is minimized to reduce the quantity of defective units due to a difference of physical performance in a high earthquake-proof rubber isolator, a lead-inserted earthquake-proof rubber isolator, and an earthquake-proof rubber isolator of the natural rubber group, which are large earthquake-proof systems. Moreover, the

apparatus employs an increased quantity of steel members having a relatively constant mechanical performance, thereby having an improved endurance.

Furthermore, the apparatus enables a structure and the ground to move together against a wind load or other external forces, so that habitants in a high- rise building can make a living as if they lived in a house.

And also, the apparatus can be well replaced with already installed members such as a port support. In the case of long usage, the performance of the apparatus is not lowered by a creep because of the minimization of rubber.

In the combination-type earthquake-proof apparatus of the present invention, the vertical load supporting function and the horizontal load-resisting function can be separately designed, so that the design can be standardized.

In the combination-type earthquake-proof apparatus of the present invention, due to the standardization of the product, the simple combination of the vertical load and the horizontal load restoring systems enables a rapid production process.

In addition, since the vertical load supporting function and the horizontal load-resisting function are separated, the apparatus can perform its functions very well not only with respect to small-and medium-scaled earthquakes but also with respect to large-scaled earthquakes.

In the combination-type earthquake-proof apparatus of the present invention, since the vertical load supporting function and the horizontal load- resisting function are independent from each other, eliminated is a problem of the prior art that the height of an upper structure is changed even by a small horizontal displacement.

In the combination-type earthquake-proof apparatus according to the present invention, the surface of the second friction plate is divided into a first friction surface for a small-scaled earthquake and a second friction surface for a

large-scaled earthquake so as to function based on the earthquake scales.

Therefore, the apparatus can perform an earthquake-proof function in respect of the small-scaled earthquake. Moreover, the apparatus can perform an earthquake-proof function having an ultra-high damping performance of limiting the magnitude of the displacement in the large-scaled earthquake.

Further, in the case of utilizing an elastomeric bearing, the seismic energy is absorbed by a shear deformation of the elastomeric bearing in the small-scaled earthquake, while the seismic energy is absorbed by a friction between the first friction plate made from fluorine resin or high-molecular compounds and the second friction plate made from stainless steel and adhered to the lower surface of the upper plate in the medium-and large-scaled earthquake.

Since the elastomeric bearing undergoes a shear deformation only by a shearing force not larger than the frictional force between the first friction plate made from fluorine resin or high-molecular compounds and the second friction plate made from stainless steel, there is no movement of the upper structure in the vertical direction.

Further, the combination-type earthquake-proof apparatus of the present invention has a construction, which enables the impact force by the horizontal shearing force applied between the upper and lower structures to be dispersed in the vertical direction against the weight of the upper structure, so as to reduce the impact force applied to the upper structure in the horizontal direction in the large-scaled earthquake, thereby preventing a high-rise building from collapsing and preventing an upper plate of a bridge from being displaced out of a displacement range.

For maintaining a stable civilized living, the combination-type earthquake-proof apparatus of the present invention can be employed for an

earthquake-proof design of an atomic power plant and applied to all structures, which may be seismically damaged, including a hospital, a school, a public building, a semiconductor factory, and an LNG tank.

While there have been illustrated and described what are considered to be preferred specific embodiments of the present invention, it will be understood by those skilled in the art that the present invention is not limited to the specific embodiments thereof, and various changes and modifications and equivalents may be substituted for elements thereof without departing from the true scope of the present invention.