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Title:
GEO ISOLATOR (UNDER GROUND SEISMIC ISOLATION SYSTEM)
Document Type and Number:
WIPO Patent Application WO/2019/038614
Kind Code:
A1
Abstract:
The present invention is introduced as a new Seismic Isolator System with the aim of reducing forces of strong earthquake on structure and eliminating limitations of conventional seismic attenuating systems. This isolation system, without the need of sophisticated and costly equipment and devices, changes the upper soil layer of a site, as an alternative, with new unified distributed materials to completely separate the structure from underground soil; dynamic properties of the new material layer reduce earthquake forces before entering into the structure. The idea of this approach is to transfer isolation system from inside of structure to the soil. In this way, the isolation system is constructed within the bed soil of site located below the structure and under the foundation level for which the seismic isolation level extends across the sub foundation level to depth. As a result, with the implementation of this isolation system, the whole structure, including foundation, is separated from bed soil at the foundation bottom level. By this technology, the tools and equipment of isolation are replaced with a layer of separating materials while the isolation level is transmuted to sub‐foundation level. At this basis, this separation system can be built before construction of structure and foundation. Due to the fact that this separation system is built before construction and does not require use of complex isolating systems, this system can be used extensively in the urban areas and new towns before construction for seismic areas. This system can also be used against earthquake forces and dynamic waves to rehabilitate underground metro tunnels and other buried structures underground as civil engineering projects, pipelines, gas and oil stores, underground installations, and so on. This new seismic isolation method is introduced by the inventors as "GEO ISOLATOR", which is a step forward to reduce the causality of life and the financial cost of the earthquake.

Inventors:
SARRAF SADYAR (IR)
SARRAF SAMYAR (IR)
Application Number:
PCT/IB2018/055916
Publication Date:
February 28, 2019
Filing Date:
August 06, 2018
Export Citation:
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Assignee:
SARRAF SADYAR (IR)
SARRAF SAMYAR (IR)
International Classes:
E04H9/02
Foreign References:
US20160169312A12016-06-16
US20160169312A12016-06-16
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Claims:
CLAIMS

1) Under Ground Seismic Isolating System; GEO ISOLATOR is made out of four main parts named as Central Damping Core (CDC), Vertical Separator Layer (VSL), 1st Horizontal Separator Layer (HSL1) and 2nd Horizontal Separator Layer (HSL2).

2) The Under Ground Seismic Isolating System; GEO ISOLATOR according to claim 1 is built under the foundation in the bed soil.

3) GEO ISOLATOR according to claim 1, is constructed before beginning of the structure construction operation.

4) The Under Ground Seismic Isolating System; GEO ISOLATOR according to claim 1 is built over the entire foundation-soil contact surface with adequate depth in sub soil.

5) The Under Ground Seismic Isolating System; GEO ISOLATOR according to claim 1 is independent of superstructure system, geometry, dimensions and suitable for any usage of construction: residential, business, army, industrial and etc.

6) The Under Ground Seismic Isolating System; GEO ISOLATOR according to claim 1 has got vast operation field for rural, urban, suburb and town area which are faced up to high earthquake risk and can be used to retrofit other underground structures as tunnels due to earthquake and dynamic waves effects.

7) The Under Ground Seismic Isolating System; GEO ISOLATOR according to claim 1 is including of a Central Damping Core (CDC) which is located uniformly at the center of the system over entire surface of the under foundation.

8) The Central Damping Core (CDC), according to claim 6, is the main part of The GEO ISOLATOR that is a continuous and integrated ground isolator layer that plays the basic role of energy mitigation for passing seismic waves and mitigates major part of earthquake force.

9) The Central Damping Core (CDC), according to claim 6, is made from mixture of strength material and damping material with a specific mixing percent, while mixing percent specified from laboratory tests for any case.

10) The strength material, according to claim 9, is natural stone graded as particles which provide required strength for isolation layer to carry on the gravity loads. Due to much lower stresses level for the ground isolating layer in sub soil, it is possible to use natural graded materials with normal range strength. GEO ISOLATOR - CLAIMS

11) The damping material, according to claim 9, is selected from elasto plastic material which has appropriate dynamic properties and elasto-plastic behavior with adequate damping ratio to satisfy desired damping of ground isolator layer to damp seismic wave's vibration. The damping material is graded as particles which are placed between the strength material particles to fill in the void volumes. Appropriate, wellness and elasto plastic behavior of strength and damping materials are defined and should obtain from laboratory tests. Due to much lower stress over the Ground Isolator Layer, it is possible to use elasto-plastic materials with normal range strength and high damping like elastomers.

12) The Central Damping Core (CDC), according to claim 6, duties are absorption and mitigation of transmitted earthquake energy through the system of claim 1 by utilizing plasticity specification, nonlinear response and materials damping nature of resistance and damping mixture of CDC.

13) The Under Ground Seismic Isolating System; GEO ISOLATOR according to claim 1, is including of a Vertical Separator Layer (VSL) which is located as the surrounding layer of the system of claim 1 at the boarder of soil contact era.

14) Vertical Separator Layer (VSL) according to claim 13 is made of materials with low elastic modulus and high ultimate loading capacity specifications as neoprene, soft polymer with high ultimate bearing capacity, elastomer and such materials.

15) The Vertical Separator Layer (VSL), according to claiml3, duty is mitigation of a portion of surface waves and lateral soil excitations which is transferred from surrounding ground into the body of the system of claim 1. This feature is due to flexibility of low elastic modulus of the VSL materials.

16) The Under Ground Seismic Isolating System; GEO ISOLATOR according to claim 1 is including of a 1st Horizontal Separator Layer (HSL1) which is located entirely under the CDC of claim 6.

17) The 1st Horizontal Separator Layer (HSL1) according to claim 16, is made of material with low seismic waves velocity specifications and high ultimate bearing capacity such neoprene, soft polymer with high ultimate bearing capacity, elastomer and such materials.

18) The Under Ground Seismic Isolating System; GEO ISOLATOR according to claim 1 is including of a 2nd Horizontal Separator Layer (HSL2) which is located at the bottom of the system of claim 1 and placed uniformly under the 1st Horizontal Separator Layer (HSL1) of claim 16. GEO ISOLATOR - CLAIMS

19) The 2nd Horizontal Separator Layer (HSL2) according to claim 18 is a layer of natural materials with high ultimate bearing capacity like broken stone or ballast which hardened and integrated by concrete or mortar with high cement content.

20) The 1st Horizontal Separator Layer (HSLl), according to claim 16, duty is to decrease wave length of the seismic waves passed through the system of claim 1 by refracting and changing of frequency content of these waves to those ranges that the operation performance of the system of claim 1 be maintained.

21) The 1st Vertical Separator Layer (VSL) according to claim 13 and IstHorizontal Separator Layer (HSLl) according to claim 16 provide uniqueness of the system demand to hold both dispersion of GEO ISOLATOR compared to bed soil behavior and integrity of whole system.

22) The 2nd Horizontal Separator Layer (HSL2) according to claim 18 plays the role of stabilizer and provides a base layer for upper elements to be carried on over this layer. By the way, through passing strong motion over this part, huge energy would result to crack growth and breakage of stiff material that not only leads to mitigation of a part of energy portion but also is caused to change the frequency of passing seismic wave to others.

Description:
TITLE OF INVENTION: GEO ISOLATOR (Under Ground Seismic Isolation System)

TECHNICAL FIELD: Section E04 FIXED CONSTRUCTION - BUILDI NGS

BACKGROUND ART

The earthquake is a global phenomenon and a general problem for the people all over the world throughout the history. Earthquakes have occurred millions of years ago and will continue happening in the future. Hundreds of millions of people all over the world now live in high risk of earthquake and billions dollars are being spent on stand ing against this danger. It is impossible to prevent an earthquake to occurs, but it can reduce the impact of severe earthquakes which can lead to loss of lives, accidents, damages, and colla pse of structures. U ndoubtedly, the worst earthquake damage is due to failure of structures. There are two ways to reduce the destructive effects of earthquakes in the structures.

1) SEISMIC RESISTANCE SYSTEM

The conventional method for reducing ea rthquakes destructive effect is fortifying seismic resistance system of a structure to resist under earthquake load by increasing the structural member dimensions and joint's capacities, or adding lateral strength members such as bracing, shear walls and other hardening members. Execution of this method increases the structural weight which cases extra load sand costs on a structure. I n addition, because of nonlinear shape changes in structural and non-structural members, there is a possibility of irrecoverable damages for these members and equipment allocated inside the story due to the occurrence of large displacements and significant accelerations.

2) SEISMIC ATTENUATING SYSTEM

The aim of utilizing seismic attenuating system is to absorb some portion of the earthquake energy and to reduce the forces applied to the structure instead of increasi ng the strength of the structural capacity to withstand the earthquake induced forces. According to the analytical and laboratory results, a structural system equi pped with this technology experiences a lower seismic force than conventional structures; furthermore, the main period of the structure is increased by the use of these attenuating systems. The seismic attenuating systems make the structural skeleton lighter and reduce cost of construction by reducing the earthquake force transferred to the structure. But due to high cost of available attenuating systems, total cost of using these systems is more than the saving money due to the structural lightening and has no economic advantage over conventional methods. For these reasons, the seismic attenuating systems has generally been used in developed countries and related to important structures. Seismic attenuating systems are divided into two general categories:

2-1) VIBRATION CONTROL SYSTEM

Vibration control system is the main group of Dampers which is a tool for reducing vibrations. This system is installed as a part of the structural element to reduce the vibration force by absorbing vibration energy when an earthquake occurs.

2-2) SEISMIC ISOLATION SYSTEMS

In seismic isolation system, Isolators, the whole or a part of the structure is separated from the foundation or the other parts of the structure in order to reduce the seismic response of those sections during an earthquake.

BASE ISOLATOR:

Most of the existing seismic isolators are in the form of the Base Isolator; these isolators are located at the junction of structure and the foundation. Since this system is located between the structure and the foundation, the isolators are installed at the base of the column's connection to the foundation to reduce transferring of the earthquake forces from the foundation to the upper structure. Therefore, the base Isolator system must be constructed with the materials, meanwhile this system carries on the vertical stresses due to gravity loads of structure, should have the adequate damping to reduce the forces caused by the earthquake that is transmitted through the foundation to the column's bases. Most of base isolators are made from special types of high strength rubber and steel with special type of bounding between rubber and steel to resist severe earthquakes and not to be separated.

BACKGROUND OF BASE ISOLATORS

SEPARATION OF BEDROCK

The first signs of the using this type of isolating system against earthquakes have been observed in ancient city of Persia, named Pasargad, for the tomb of Cyrus the Achaemenid king in the sixth century BC. The system is a foundation made up of a deep and broad rock placed on another foundation made out of flat and plain stones with a thick and smooth mortar layer between two foundations. These two foundations are connected in such a way that the structure has survived during earthquakes. RUBBER ISOLATOR

The first use of rubber as a seismic separator was in a primary school building with three floors in Yugoslavia in 1969. This three story concrete building was constructed on cubic blocks of rubber that were convexly displaced under the weight of the building. Since horizontal and vertical stiffness of the rubber blocks are equal, during an earthquake the building was unbalanced, mutated and moved back and forth. Consequently, this method was never being used in any building afterward.

REINFORCED RUBBER ISOLATOR

In 1954, Reinforced Rubber made of thin steel sheets covered by layers of rubber among was invented by a French engineer Freyssinet and patented in France. Reinforced Rubber creates a combination of vertical stiffness resulting from steel layers and horizontal flexibility resulting from use of rubber. Reinforced Rubber over the time has been widely used in many industries and has been used as seismic isolator for buildings since 1980.

RECYCLED TIRE ISOLATOR

In 2002, seismic isolation method for small residential buildings was developed for developing countries and for some parts of the United States. This seismic isolator is using recycled rubber tires which is filled by particular rock aggregates that is patented by Lang et al. in the United States in 2005.

RECYCLED TIRE DERIVATE AGGERAGATES (TDA) ISOLATOR

In 2007, seismic isolating method was developed for developing countries using a mixture of recycled tire derivate aggregates (TDA) and soil, proposed by Tsung et al. Despite of the advantages, increasing soil damping characteristic by adding recycled tire aggregates, use of this kind of isolator due to the high thickness of this isolating layer, about 10 to 20 meters depth, and outcropping of 10 meters from each side of the structure has been inappropriate.

SUMMARY OF INVENTION

TECHNICAL PROBLEM

From the beginning of the world, earthquakes have occurred and will continue happening in the future. The most dramatic and memorable images of earthquake damages are indeed those of structural collapse. There are two fundamental approaches to mitigate earthquake damages on structures. The first approach is fortifying the structural lateral resistance system, using structural elements, in order to tolerate exerted earth motion forces. These systems include moment resistance frames, shear walls and braces. Diminishing earthquake forces before entering into the structure states as the second approach. The first approach which is known by name of conventional method is well-known, constructor-accepted and it has been widely used within the engineering practice; however, this method increases dead load of structure which can be undesirably costly. The second approach is less practiced in the literature and needs to be more explored. Designing usual elements and structural systems deals with whole arise earthquake energy exerting to the structure during ground motions. The main goal of partake quake-attenuating in buildings is to absorb energy and to attenuate the exerted forces into structures as a result of ground motions. Quake-attenuating systems are divided into two main categories of Dampers and Isolators. Quake-attenuating systems restrain transmission of ground displacement into the structure; therefore, it makes considerable subsidence in story acceleration and story drifts that overall result is visible in designing forces carried by each elements. Notwithstanding achievements and developments in the field of quake-attenuating systems production, applying in structures is proportional to following complicated technology and subtle engineering. Installation and initiation of dampers depend on educated and expert crew; moreover, such attenuating systems need maintenance and repair during the useful structural life time. The aforementioned reasons lead to limitation and high-cost of utilizing such system, especially in developing countries. Consequently, nowadays civil engineering suffers from the lack of such quake-attenuating systems to be able to respond simply but applicable mechanism at the same time for almost a ll types of structure. SOLUTION TO PROBLEM

A NEW SEISMIC ISOLATION SYSTEM: GEO ISOLATOR

Based on the idea of seismic attenuating systems, a new definition of seismic isolation is presented as Ground Isolation. The Ground Isolation is a new idea of seismic isolation that the isolation level is relocated from inside of the structure to the bed soil of under structure. The ground isolation idea is made possible by introducing Ground Isolator which is a seismic attenuating layer based on the Ground Isolation idea. Ground Isolator changes the site soil conditions before beginning of construction operation in such a way to attenuate the earthquake force transmission to the upper structure. The inventors named this new seismic isolation system as " GEO ISOLATOR".

Ground Isolation is a type of seismic isolation system that is relocated from inside of the structures to the under structure bed soil and the isolating level is displaced from inside of the structure or structure-foundation level to the under foundation level inside of sub soil. The seismic base isolation system is characterized as single point isolation by locating at the column's bases connection to the foundation while Ground Isolation is extended to continuous surface isolation over entire foundation-soil surface. Separation of the whole structures and foundation on the contact surface from sub soil leads to change the nature of a single point of base isolation into the integrated Ground Isolator Layer. Ground Isolator Layer is placed between the structure and the sub soil to separate the structure from the bed soil. Ground Isolator Layer is made from graded strength materials which have adequate strength to carry on the gravity loads of structure that are mixed with graded elasto-plastic materials which have required dynamic characteristics of attenuating seismic loads. Ground Isolator Layer behave as an elasto-plastic mixture for which the elastic materials part satisfies the elastic section of constitutive modeling due to low stiffness and high ultimate strength and by the corporation with the resistance part of geo-materials to fulfill the need of plastic behavior of the system that result to the overall high hysteretic damping feature for Ground Isolation System. Ground Isolation System is constructed before beginning of the structure construction operation. For this purpose, an under foundation layer of sub soil with a specific depth is removed and replaced by the Ground Isolation System, GEO ISOLATOR. ADVANTAGE OF GEO ISOLATOR

GEO ISOLATOR (Underground Seismic Isolation System) has the following benefits:

. The seismic isolation system is transmitted from structure to bed soil.

. The isolating level is transferred to the level of under foundation in the sub soil from inside of the structure or at junction of structure and foundation.

. The conventional seismic base isolation systems are composed from a series of single point isolators while the Ground Isolation System is an integrated continuous surface isolation system placed over entire foundation-soil surface.

. By utilizing the Ground Isolation System, the whole structure and foundation are separated from sub soil at all contact surfaces.

. Single point of isolation due to point isolator devices is changed to integrated isolation layer with the use of Ground Isolator layer.

. The Ground Isolator Layer is placed between the structure and the sub soil to separate the structure and foundation from the bed soil.

. The Ground Isolator Layer is made from graded natural stone aggregates which have adequate strength to carry on gravity loads of the structure which are mixed with graded elasto-plastic_material with required specific dynamic characteristics for attenuating seismic loads.

. The Ground Isolator Layer behaves as an elasto-plastic mixture for which the elastic material part satisfies the elastic section of constitutive modeling due to low stiffness and high ultimate strength and with the corporation of the resistance part of geo-materials to fulfill the need of plastic behavior of the system that result to the overall high hysteretic damping feature for the Ground Isolation System.

. The Ground Isolator Layer, which includes mixing of strength material and damping material with desired damping and strength specifications, is the main part of the Underground Seismic Isolation System that plays the basic role of energy mitigation for passing seismic waves.

0. The Underground Seismic Isolation System is constructed before beginning of the structure construction operation. For construction of a Underground Isolation System, specified depth of sub soil of under foundation location should be removed and replaced by the Ground Isolation System. The Underground Seismic Isolation System has got vast operation fields for rural, urban, sub-urban and new town areas which are faced up to high earthquake risk and can be used to retrofit other underground structures like tunnels due to earthquake and dynamic waves. The Underground Seismic Isolation System with these specifications is named GEO ISOLATOR by inventors.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1) GEOISOLATOR-Seismic under Ground Isolation System (2D map)

1. Structure

2. Bed soil

3. Foundation

4. Central Damping Core (CDC)

5. Vertical Separator Layer (VSL)

6. l s Horizontal Separator Layer (HSL1)

7. 2 nd Horizontal Separator Layer (HSL2)

Note- Figures are schematic and not to scale.

Figure 2) GEOISOLATOR- Seismic under Ground Isolation System (3D map)

1. Structure

2. Bed soil

3. Foundation

4. Central Damping Core (CDC)

5. Vertical Separator Layer (VSL)

6. l s Horizontal Separator Layer (HSL1)

7. 2 nd Horizontal Separator Layer (HSL2)

Note- Figures are schematic and not to scale.

As seen in the figures, the GEO ISOLATOR is made from 4 parts: Central Damping Core (CDC) is the main part of the GEO ISOLATOR made from mixture of graded strength material and graded damping material that play the basic role of central core of energy mitigation for passing seismic waves and mitigate major part of earthquake force; meanwhile, the other parts, Vertical Separator Layer (VSL) andl s Horizontal Separator Layer (HSLl),provide uniqueness of the system demand to hold both dispersion of Geo-lsolator compared to bed soil behavior and integrity of whole system. These two systems, HSL1 and VSL, also can change some seismic wave frequency, caused by the nature of low wave velocity feature of these materials, to other frequencies that mitigate destruction aspect. Lastly, 2 nd Horizontal Separator Layer (HSL2) plays the role of stabilizer and provides a base layer for upper elements to be carried on over this layer. By the way, through passing strong motion over this part, huge energy would result to crack growth and breakage of stiff material that not only leads to mitigation of a part of energy portion but also is caused to change the frequency of passing seismic wave to others. DESCRIPTION OF EMBODIMENTS

I ntroduction of a new seismic isolation system; GEO ISOLATOR

GEO ISOLATOR is a new kind of seismic isolation system that is an alternative to seismic base isolation systems; in fact, GEO ISOLATOR is a system which is based on the Ground Isolation idea that provides an alternative for the base isolation idea by using Ground Isolator Layer instead of base isolator devices. Ground Isolation is a new idea in the field of seismic isolation which is based on the idea of relocating the isolation location from inside of the structure to the bed soil under the structure. Ground Isolator is a seismic attenuating layer based on the idea of Ground Isolation that changes site soil conditions in such a way to attenuate transmitted earthquake forces to the upper structure.

The GEO ISOLATOR (Underground Seismic Isolation System) characteristics:

1. I n the GEO ISOLATOR the seismic isolation system location is transmitted from structure to under structure bed soil .

2. Isolation level is transferred from inside structure or structure-foundation junction to the under foundation level in bed soil.

3. Point isolating at individual structural elements converted to continuous isolating in bed soil and isolation system is extended from single point isolators to a continuous and integrated isolating layer over the entire foundation-soil contact surface.

4. The whole structure and foundation are completely separated from the sub soil by this continuous and integrated isolation system .

5. A series of single point base Isolator devices are changed into one integrated Ground Isolator Layer.

6. Due to ground-structure integrated isolating layer and distribution of structure gravity load over a greater area, the stresses through the Ground Isolator Layer at the bed soil are much lower than the point isolating (Stress on the Ground Isolator layer is about to soil strength ).

7. Due to need of much lower stress level for the Ground Isolator Layer, it is possible to use materials with strength in the range of natural stone aggregates instead of requiring use of high strength materials as steel to resist gravity loads in seismic isolators.

8. Due to distribution of seismic loads in the kind of shear waves over a greater and continuous isolation surface, the shear strain on the Ground Isolator Layer at the bed soil are much lower than the isolator devices . 9. Due to much lower forces over the Ground Isolator Layer, it is possible to use elasto-plastic materials with moderate strength and high damping instead of the high strength and high flexible materials like vulcanized rubber to damped seismic forces.

10. Due to much lower stress on the Ground Isolator Layer, it is possible to mixture moderate strength material and damping elasto-plastic material without the need of any specific bounding for them like steel rubber bond as reinforced rubber.

11. The Ground Isolator Layer is made from mixture of strength material and damping material with a specific mixing percent while mixing percent is specified from laboratory tests for any case.

12. The strength material is graded as particles which provides required strength for isolation layer to carry on the gravity loads.

13. The damping material is selected from elasto plastic material which has appropriate dynamic properties and elasto plastic behavior with adequate damping ratio to satisfy desired damping of ground isolator layer to damp seismic waves vibration, the damping material is graded as particles which are placed between the strength material particles to fill in the void volumes. Appropriate, wellness and elasto-plastic behavior of strength and damping materials are defined and should obtain from laboratory tests.

14. The Ground Isolator Layer behaves as an elasto-plastic mixture for which the elastic material part satisfies the elastic section of constitutive modeling due to low stiffness and high ultimate strength and with the corporation of the resistance part of geo-materials to fulfill the need of plastic behavior of the system that result to the overall high hysteretic damping feature for the Ground Isolation System.

15. To construct the GEO ISOLATOR system, firstly, the excavation is carried out to maintain required depth below the foundation level and, at the same time, soil stabilizer system is developed over the wall of the excavation. The lower layer, HSL2, of the separator is made from graded fractured stones with the high-grade concrete as a mortar to fill the gaps and to maintain layer integrity in the combination with the fractured stones. After adequate concrete hardening, the upper layer, HSL1, is constructed with a layer of continuous elastic materials and afterward the vertical separator layer, VSL, is localized vertically all around the excavation walls by a layer of elastic materials. Central Damping Core, CDC, is a mixture of damping and strength materials that is a volume limited by the layer of HSL1 as lower limit and foundation base as upper limit while is surrounded by the VSL. Central Damping Core is made in the layered form to make possible the necessary compaction. After the GEO ISOLATOR construction, foundat and structure would be constructed in the normal manners.