ELASTOMER-BASED EARTHQUAKE ISOLATORS MADE OF NATURAL RUBBER, SYNTHETIC RUBBER, RIGID POLYURETHANE AND SIMILAR MATERIALS WITH CONICAL, PYRAMIDAL SHAPE (FRUSTO-CONICAL PRISM, FRUSTO-PYRAMIDAL PRISM WITH SQUARE, RECTANGULAR AND OTHER GEOMETRIC CROSS-SECTIONS)

Description of the Technical Field The invention relates to the elastomer-based earthquake isolators. The invention relates in particular to a conical or pyramidal earthquake isolator based on natural rubber or synthetic rubber or rigid polyurethane and similar elastomers, wherein said isolator is developed in order to protect the engineering structures such as reinforced concrete or steel constructions as well as the highways, railway bridges, viaducts, petrochemical tanks, nuclear plants against the destructive and damaging effects of the earthquakes and to ensure the security of life and property, wherein the layers made of natural or synthetic rubber or rigid polyurethane and similar elastomeric materials and reinforced with plates made of steel metal derivatives are adhered to and laminated with steel plates, wherein the isolator comprises a coreless massive structure or a structure with rigid polyurethane or lead core positioned at the center on the vertical axis and/or a high performance structure with rigid polyurethane elastomer core or lead core manufactured by placing additional peripheral elastomeric cores on the vertical axis in addition to _^ the axial core positioned at the center on the vertical axis, or said isolator comprises a coreless massive structure or a hollow structure.

Description of the State of the Art

Earthquake, tremor or quake is a phenomenon of the development of seismic waves resulting from the sudden release of energy in the earth's crust and the shaking of the ground by these waves. The term seismic activity refers to the frequency, destructive effects, type and size of an earthquake over an area where it is experienced. Earthquakes are measured using the seismometers. The science that studies these events is called Seismology. The intensity of the earthquakes is determined with the moment magnitude (or with the Richter scale formerly used). According to this scale, the earthquakes with a magnitude of 3 and lower are usually imperceptible, while the earthquakes with a magnitude of 6 and over may have destructive effects. The intensity of shaking is measured with Mercalli intensity scale. The depth of the point where the earthquake occurs also affects the destructive power and the earthquakes occurring at a point closer to the ground cause more damage.

At the earth's surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground. Sometimes, when a large earthquake occurs at a point close to the surface, it may cause a tsunami. These shakings may also trigger landslides and volcanic activities.

In general, the word earthquake is used to describe any seismic event that either develops as a natural phenomenon or is caused by humans and that generates seismic waves. Earthquakes are usually caused suddenly by the rupture of the faults (fault lines) in the earth's crust. Earthquakes may also result from the volcanic activities, landslides, mine blasts or nuclear tests.

The first application of the seismic isolators (earthquake isolators), intended for protecting various structures against the damaging forces of the earthquakes they experience, dates back to 1900s B.C. On the other hand, the application of the earthquake isolators in the modern sense has increased since 1975 and their use is becoming more widespread with each passing day. The main reason why the earthquake isolators are now used more commonly and they have increased reliability is that the structures provided with earthquake isolation using the earthquake isolators have not suffered any damage from the great magnitude earthquakes that they have encountered following said isolation process. For the production of the earthquake isolators according to prior art, only the natural rubber or synthetic rubber is used as the material, and the production is completed by placing a lead core at the center of the rubber-based earthquake isolators on the vertical axis in order to improve and increase the insufficient mechanical properties of such rubber-based earthquake isolators. However, the lead core also has disadvantages resulting from the physical properties of the lead material.

These disadvantages are as follows: The lead core does not absorb, until a certain size, the earthquake shear forces being in a direction parallel to the earth's crust and earthquake acceleration generated by the earthquake and it exhibits a rigid behavior against the earthquake, and after a certain magnitude of earthquake intensity, the lead core begins to deform and yield, i.e. change shape. When deformed, it is not able to recover its original properties and it loses its original mechanical properties, in other words, it becomes necessary to dismantle the isolator and remove the deformed lead core and replace the same with a new core. If this replacement is not undertaken, the isolator becomes unable to exhibit its protective and isolating feature during the future earthquakes.

Due to the insufficient mechanical properties of natural rubber and synthetic rubber, it is not possible to make the earthquake isolators with very high capacity of absorption.

As a result, due to the aforesaid drawbacks of the existing earthquake isolators and insufficiency thereof in terms of earthquake isolation, it has become necessary to develop the earthquake isolators, which are sufficient in technical terms and have novel shapes.

Description of the Objects of the Invention Based on the mentioned state of the art, the object of the invention is to develop elastomer-based earthquake isolators made of natural rubber, synthetic rubber, rigid polyurethane and similar materials with conical, pyramidal shape (frusto-conical prism, frusto-pyramidal prism with square, rectangular and other geometric cross- sections), which overcome the problems of the state of the art and provide many additional advantages.

Another object of the invention is to eliminate the drawbacks and deficiencies of the 5 previous rubber earthquake isolators with and without lead core and provide new additional advantages and performance increase for the isolators, owing to the present invention of the earthquake isolators with rigid polyurethane core.

Another object of the invention is to enable the use of "rigid polyurethane core and/or 10 cores" in the rubber earthquake isolators, instead of the lead core. Thus, the object of the invention is to render the structures where such earthquake isolators are used resistant to the massive earthquakes, owing to the high mechanical strength and high ability of earthquake absorption of the rigid polyurethane core and/or cores improving the earthquake resistance of the rubber-based earthquake isolators made with rigid i s polyurethane core material.

Another object of the invention is to enable the earthquake isolators with rigid polyurethane core having high strength properties to become resistant to repeated and massive earthquakes and to have a long life without showing the signs of aging. 0

Another object of the invention is to improve, using the conical prism or pyramidal prism shaped earthquake isolators, the strength of the rubber-based earthquake isolators that are otherwise unable to exhibit adequate and desired strength when subject to great earthquakes, thereby eliminating their drawbacks and increasing 5 their performance.

Another object of the invention is to develop an earthquake isolator, which is resistant to the static and dynamic column loads (P) that the structures experience during an earthquake and the earthquake shear forces (Q) in the horizontal directions resulting0 from the earthquake as well as the earthquake accelerations, wherein said isolator absorbs said forces and accelerations to render the same harmless and prevents the destruction of the tall buildings as a result of the displacements (ground displacements) caused by the earthquake.

Another object of the invention is to form a composite structure prepared by laminating and adhering to each other many overlapped steel metal derivative sheets and rubber layers and positioning a rigid polyurethane core or lead core at the center of the isolator on the vertical axis. In other words, the object of the invention is to develop "elastomer-based earthquake isolators made of natural rubber, synthetic rubber, rigid polyurethane and similar materials with conical, pyramidal shape (frusto- conical prism, frusto-pyramidal prism with square, rectangular and other geometric cross-sections)", which have a form made using the steel metal derivative sheets increasing the rigidity on the vertical axis and using the elastomer-based material with a rigid polyurethane core or lead core for providing the flexibility on the horizontal axis and absorbing the energy generated by the earthquake.

In order to achieve the objects of the invention, the elastomer-based earthquake isolators made of natural rubber, synthetic rubber, rigid polyurethane and similar materials with conical, pyramidal shape (frusto-conical prism, frusto-pyramidal prism with square, rectangular and other geometric cross-sections) have been developed with a coreless massive structure, a hollow structure, a rigid polyurethane core or a lead core.

Description of the Figures

Figure-1 : A sectional view of a preferred representative embodiment of the invention in a state assembled under the building columns or under the joists.

Figure-2: A perspective view of a preferred representative embodiment of the elastomer-based earthquake isolator according to the invention having the shape of a pyramidal prism and comprising a rigid polyurethane core or a lead core or a hollow structure, in disassembled state.

Figure-3: A perspective view of a preferred representative embodiment of the elastomer-based massive earthquake isolator according to the invention having the shape of a pyramidal prism, in disassembled state. Figure-4: A sectional view of a preferred representative embodiment of the elastomer-based coreless massive earthquake isolator according to the invention having the shape of a conical prism or pyramidal prism.

Figure-5: A sectional view of a preferred representative embodiment of the elastomer-based earthquake isolator according to the invention having the shape of a conical prism or pyramidal prism and comprising a rigid polyurethane core or a lead core or a hollow structure.

Figure-6: A sectional perspective view of a preferred representative embodiment of the elastomer-based earthquake isolator according to the invention having the shape of a conical prism or pyramidal prism and comprising a rigid polyurethane core or a lead core or a hollow structure.

Reference Numbers

Detailed Description of the Invention Owing to "the elastomer-based earthquake isolators (X) according to the invention made of natural rubber, synthetic rubber, rigid polyurethane and similar materials with conical, pyramidal shape (frusto-conical prism, frusto-pyramidal prism with square, rectangular and other geometric cross-sections)", said elastomer-based novel earthquake isolators according to the invention having a massive structure, or a structure with rigid polyurethane core or lead core, or a hollow structure without any core, have been provided with an extended lifetime and mechanical properties and performance that are considerably improved compared to the existing conventional earthquake isolators in terms of resistance to repeated and great magnitude earthquakes.

Due to the inadequate mechanical properties and the short useful lifetime of maximum 50 years of the natural rubber or synthetic rubber, it has not been possible to make long-life earthquake isolators having a high capacity of absorption. Unlike the rubber earthquake isolators of the prior art having a low capacity in terms of absorption of earthquake forces and earthquake acceleration, the earthquake isolators according to the present invention have been provided with increased resistance to great earthquakes owing to the conical prism or pyramidal prism shape and owing to the improvement of the mechanical strength performance brought about by the addition of rigid polyurethane core to the earthquake isolator as an alternative to the lead core that was added to the old type isolators in order to improve their earthquake absorption ability.

Whereas the natural rubber employed in the manufacture of the rubber-based earthquake isolators has a Young's modulus between E=0.76 and 4,5 MPa, this value is between E=10 and 120 MPa for the rigid polyurethane elastomers. In addition, the shear modulus for the natural rubber is between G=0.35 and 1.35 MPa, while the rigid polyurethane elastomers have a shear modulus between G=3,30 and 39,99 MPa. The density of rubber is 910 to 1100 kg/m3, whereas the rigid polyurethane elastomers have a density of 1100 to 1270 Kg/m3.

The natural and synthetic rubbers have a Shore A hardness value between 50 and 75, whereas the Shore A hardness value for the rigid polyurethane elastomers is between 50 and 100 it is possible to manufacture the same with desired hardness value. Owing to this property, the elastomeric core made with rigid polyurethane material has considerably increased the earthquake resistance and the earthquake isolation ability of the rubber earthquake isolators (X).

With these characteristics, the rigid polyurethane core (3) has eliminated disadvantages of the previously existing rubber earthquake isolators with lead core and increased the resistance of the structures to the repeated earthquakes.

Whereas the lead core becomes deformed and suffers permanent damage due to the horizontal earthquake shear forces (Q) and loses its mechanical strength, such a performance loss is out of question in a rigid polyurethane core and thus the malfunction of the isolator (X) is not possible. Said rubber earthquake isolators (X) with rigid polyurethane core (3) according to the present invention may be reliably used for many years. The steel metal derivative reinforcement sheets (reinforcement plates) (1), which are placed in a parallel manner one on top of another at certain intervals and are in circular, square, rectangular and other geometric shapes, are adhered and laminated to the mass of natural rubber layers (2) or synthetic rubber layers (2) or rigid polyurethane elastomer layers (2) with conical prism or pyramidal prism shape and to the lower steel loading plate (5) at the bottom and to the upper steel loading plate (4) at the top. The rigid polyurethane core (3) or lead core is placed into the axial cavity of the earthquake isolator (X) which is made hollow axially on the vertical axis, or the isolator is manufactured with a massive structure with no inner cavity or it is manufactured as a hollow structure.

By means of the rigid polyurethane- or natural or synthetic rubber-based side surface covering member (10), which covers the side surfaces of the mass of natural rubber or synthetic rubber layers (2) or rigid polyurethane elastomer layers (2) and of the steel plates and which protects the isolator from the external effects, the outer surface of the isolator (X) is covered and in this manner, the earthquake isolator is protected against the external effects. The upper steel loading plates (4) and the lower steel loading plates (5), which are present as the last steel plate respectively at the top and bottom portions of the earthquake isolator (X), and the lower steel assembly plates (6) and the upper steel assembly plates (7), which are used to connect the earthquake isolator with the structure, with the basement or the column of the building or with the bridge joist or the bridge pier, are connected by means of the assembly connection members (8), and in this manner, the earthquake isolator (X) is formed.

Said lower steel assembly plates (6) and upper steel assembly plates (7) present in the earthquake isolator (X) are connected via the anchor members (9) and the assembly connection members (8) with the location under the column head (11) of the column (12) that joins the basement of the structure aimed to be protected from the damaging effects of the earthquake with the first floor thereof, thereby securing the earthquake isolator (X) to the building. In this manner, "the rubber earthquake isolator with rigid polyurethane core or the earthquake isolator with lead core or the massive earthquake isolator or the hollow earthquake isolator (X)" is secured to the structure aimed to be protected from the earthquake.

The rubber-based earthquake isolator (X) with rigid polyurethane elastomer core absorbs the energy of the dynamic and static vertical column loads (P) experienced by the structures during an earthquake and the earthquake shear forces (Q) also resulting from the earthquake, and thus it damps said forces.

The isolator is strengthened with steel metal derivate plates (1) in the vertical direction and laminated by way of adhering the natural rubber or synthetic rubber layers (2) or rigid polyurethane layers (2) with these steel plates (1), wherein a rigid polyurethane elastomer core (3) or a lead core (3) is placed at the center of the isolator (X) on the vertical axis and the earthquake isolator (X) is formed with the side surface covering members (10), which enable the isolator (X) to be covered with the natural rubber or synthetic rubber or rigid polyurethane material that entirely surrounds the outer side surface of the isolator (X) in the vertical direction. The rigid polyurethane elastomer core (3) is formed, the connection of which is provided by way of adhering the same to the center of the earthquake isolator (X) along said isolator (X) on the vertical axis. In order for said rigid polyurethane elastomer core (3) to be positioned into the isolator, the interior of the isolator (X) is made hollow on the vertical axis according to the envisaged dimensions of the rigid polyurethane core (3) and the rigid polyurethane core (3) is cast in liquid form into said hollow or it is placed at a later time into the core hole externally manufactured, thereby positioning said core into the isolator. Moreover, when it is desired to make an earthquake isolator (X) with lead core, the lead core (3) is manufactured outside the isolator (X) and said lead core (3) is subsequently positioned into the earthquake isolator.

The elastomer-based earthquake isolator has been developed as an industrial product of engineering, said isolator being formed by the rigid polyurethane elastomer core (3) or lead core (3), the steel metal derivative plates (1) and rubber- based material layers (2) or rigid polyurethane elastomer layers (2) and the side surface covering member (10) made of rigid polyurethane or rubber material to entirely surround the outer side surface of said earthquake isolator (X).

The rubber earthquake isolator (X) with rigid polyurethane core (3) is laminated by way of adhering to the lower steel loading plates (5) and the upper steel loading plates (4) respectively at the bottom and top portions thereof and the natural rubber or synthetic rubber or rigid polyurethane layers (2).

There is provided a covering member (10) with rigid polyurethane or rubber material, which is adhered to the outer side surfaces of said isolator (X).

The upper steel assembly plates (7), which serve to connect said earthquake isolator (X) with the building column or bridge joist (12) and which are used to secure the earthquake isolator (X) to the building via their assembly to the upper steel loading plates (4) at the bottom and top portions of the isolator (X), are mounted to the building by means of the assembly connection members (8).

In order to protect the buildings from the destructive and damaging effects of the earthquakes, the earthquake isolator (X), placed under the column head (11) or in the middle of the column (12) or in the head of the column (12) on the basement of the building desired to be protected, is secured to the building by means of the anchor members (9) and the assembly connection members (8). The rubber- or rigid polyurethane-based conical or pyramidal earthquake isolator (X) with a rigid polyurethane core or a lead core or with a massive structure or the elastomer-based conical or pyramidal earthquake isolator (X) with a hollow structure, which is positioned at the desired locations of the structures, i.e. the buildings or the bridges, performs the absorption of energy against the static and dynamic vertical column loads (P) resulting from the earthquake, against the earthquake shear forces (Q) formed in a horizontal direction parallel to the basement of the building, against the earthquake accelerations generated by the earthquake and against the ground displacements in the horizontal direction, thereby eliminating the damaging and destructive effects of the earthquake, in short, damping the earthquake, and isolating the earthquake to prevent the same from being transmitted to the structure. In this way, the earthquake isolator (X) protects the structure where it is mounted against the earthquake.

The earthquake isolators (X) manufactured from natural rubber, synthetic rubber, rigid polyurethane and similar elastomer materials in conical or pyramidal shape (frusto-conical or frusto pyramidal prism with square, rectangular and other geometric cross-sections) are entirely different from the existing earthquake isolators in terms of shape. Instead of being the earthquake isolators (X) with plain cylindrical shape with circular cross-section or with square or rectangular cross-section, they are the earthquake isolators (X) with frusto-conical prism or frusto-pyramidal prism shape with square, rectangular, pentagonal, hexagonal and similar geometric cross- sections. Owing to the manufacture of the rubber earthquake isolators (X) with rigid polyurethane core according to the invention, a significantly improved performance is obtained in terms of both shape and material as well as the resistance against the successive shocks from the repeated earthquakes as compared to the previously existing conventional rubber-based earthquake isolators (X) with or without lead core, and the lifetime is also extended over said conventional isolators.

The earthquake isolators (X) according to the prior art have a limited ability of absorbing the earthquake forces and earthquake acceleration. By means of the present invention, the elastomer-based earthquake isolators (X) made of natural rubber, synthetic rubber, rigid polyurethane and similar materials with conical, pyramidal shape (frusto-conical prism, frusto-pyramidal prism with square, rectangular and other geometric cross-sections) are provided with improved capability of earthquake absorption and improved mechanical strength performance such as the preservation of the structural stability and the prevention of the tipping of the buildings even under the conditions of extensive ground displacements, thereby offering the earthquake isolators (X) with enhanced resistance against the great magnitude earthquakes.

Whereas the lead core becomes deformed and suffers permanent damage due to the horizontal earthquake shear forces (Q) and loses its mechanical strength, such a performance loss is out of question in a rigid polyurethane core and thus the malfunction of the isolator (X) is not possible. Said rubber earthquake isolators (X) with novel shapes and rigid polyurethane core (3) according to the present invention have such mechanical properties enabling them to be reliably used for many years.

Moreover, the earthquake isolators (X) with conical prism or pyramidal prism shape according to the present invention are entirely different from the conventional earthquake isolators (X) in terms of shape, wherein said shape of pyramidal or conical prism enables the earthquake isolators (X) to have increased physical performance.