Seismic isolation (earthquake isolation or base isolation) is a method that protects the structure and all the components inside the building from the destructive effects of the earthquake by creating a layer between the building and the ground thanks to special devices (earthquake isolation devices) placed between the building itself and its foundation.
Seismic Isolation and Working Principle
Seismic isolation (earthquake isolation or base isolation) is a special device (earthquake isolation devices) placed between the building itself and its foundation, creating a layer between the building and the ground, and the aim is protecting all components inside the building from the destructive effects of the earthquake.
Earthquake isolators (seismic isolators or base isolation devices) are placed one per column in buildings and more than one under the curtain, and the superstructure is separated from the foundation and the ground.
Seismic isolation increases the period of the structure to which it is applied, thanks to the lateral flexibility of the devices, and meets the horizontal displacement demand that will occur during an earthquake at the isolator interface (with earthquake isolation devices). In addition, the damping rate, which is accepted as 5% in normal structures, increases to 20% and above when it comes to earthquake insulation, and plays an extra role in reducing the destructive effects of the earthquake.
Earthquake isolation protects both the structural and non-structural elements of the superstructure and thus ensures that the building survives any earthquake with zero damage and remains fully functional.
Earthquake isolation is the only proven and applicable method that can control relative floor drifts and floor accelerations in a building at the same time. In addition, earthquake insulation is the only method that enables the structure and all its components (structural and non-structural elements) to survive the largest expected earthquake in the area where that structure is located, and thus guarantees the uninterrupted use of the building after an earthquake.
All national and international earthquake regulations are prepared with the acceptance that the structure will be damaged at a certain level depending on the ductility level, otherwise it is not possible to design the structures. That is, all structures will receive a certain level of damage under the expected design earthquake in that area. The purpose of the regulations is not to provide damage, but to ensure the safety of life by preventing the collapse of the structures. Damage to the buildings in any earthquake can only be achieved with earthquake insulation application. Even if the loss of life can be minimized when buildings are constructed in accordance with the regulations, the only method that can prevent financial losses that will occur after a major earthquake is earthquake insulation. However, as it will enable non-structural elements (walls, ceilings, mechanical-electrical parts, cabinets, etc.) to survive a major earthquake without damage, earthquake insulation has a great psychological benefit as well as economic benefits on human health.
In addition, with the widespread use of earthquake insulation, the damage to the environment during the repair and demolition works of the buildings damaged after the earthquake is also prevented.
Detailed analysis of the above mentioned subject is available in the file named “Basic Differences in Classical and Earthquake-Proof Design in Buildings”. You can reach this file from here.
The visual regarding the above mentioned subject is available in the file named “Earthquake Resistant Design Options”. You can reach this file from here.
Important Points To Be Considered with Sismic Izolation
Important issues to be considered in a building with earthquake isolation are listed below.
Electrical and Mechanical Details
In addition to the isolator, since the structure is completely separated from the ground, the mechanical details (all connections such as electricity-water-waste-natural gas) must also be supported with special details in accordance with earthquake isolation and movement in all directions. Such special applications may be commercially available.
Photos of Example connection details will be added here.
The earthquake insulated building will be completely separated from the ground and a gap will remain around the building, since it is built in such a way that it can move freely in all directions during a possible earthquake. This gap must be crossed with all-round joints. Again, standard joints produced for such applications can be found in the market.
Drawings and photos of sample joint details will be attached here.
Vertical Component of the Earthquake
None of the earthquake isolation devices alone have an effect against the vertical component of the earthquake. If extra precautions are to be taken against vertical earthquakes, it is mandatory to use extra special damping systems in addition to the earthquake isolator. On the other hand, the effects of vertical components of earthquakes on both structural and non-structural elements are much lower than horizontal components. Considering this, according to the results of the structural analysis, it is decided whether or not to take measures against vertical earthquakes and as a result, extra special devices are used if necessary.
In buildings that are planned to be built with earthquake isolators, the building must be designed and modeled with isolator starting from the architecture. For example, the dimensions of the columns where insulators will be placed should be adjusted by calculations and the general architecture should be determined in a way that is suitable for the insulator application. The architectural approach and design in buildings with and without insulators are different from each other, and an insulator cannot be applied to an architecture that is planned and prepared without an insulator. For this reason, a building for which an earthquake isolator is planned should be solved with an appropriate architecture from the beginning.
The basic points to be considered in terms of architecture in earthquake insulated buildings are available in the file named “Architecture in Earthquake Insulated Buildings – General Approach Principles”.
After the architectural solutions of the building are adjusted to be compatible with the earthquake isolator application, static calculations can be made more effectively. Similarly, static calculations should be made with structural analysis programs that have earthquake isolator models, the capacity to perform linear and nonlinear analyzes and have proven themselves in this field.
Before static calculations begin, published by AFAD be taken from Turkey Earthquake Hazard Map design spectrum together with site-specific seismic hazard analysis also be outsourced to experts and concerned the structure of the accounts should be started thereafter.
The basic points to be considered during static modeling and analysis in earthquake insulated buildings are available in the file named “Static Modeling in Earthquake Insulated Buildings – General Approach Principles”.
Design Oversight System
Earthquake-proof structures fall under the category of “special building”. In this context, T.C. The Ministry of Environment and Urbanization requires working with predetermined experts during the design and implementation stages of special buildings. According to this system called “Design Supervision (TGUA in Turkish)”, when it comes to an earthquake insulated building, it is mandatory to work with design supervisors at both the site-specific earthquake hazard analysis (TGUA-1) and the design of the earthquake insulated structure (TGUA-5). Design supervisors are responsible for checking and approving the calculations made in the relevant areas.
Design Supervisor for detailed information about the system, enacted on Official Gazette dated 11.01.2019 “Turkey Earthquake Building Regulation Communiqué Regarding the Scope of Things Design Surveillance and Control Service” is found in the document says.
It is very important that the insulators are installed in the relevant places in the field by the expert teams in this field. The assembly of these devices should be done very precisely and carefully. Otherwise, no matter how correct design and production is made, it is very difficult to return an error that will occur during assembly.
Field assembly application examples will be added here.
Structural Differences and Savings
When earthquake isolation is applied to a building, it cannot be expected that a size or reinforcement savings will be achieved in structural elements. In some cases, savings such as reducing the size of the superstructure elements and the amount of reinforcement may be in question, but this may vary for each structure and must be checked with calculations.
In buildings with earthquake isolation, the need for shear walls is reduced or completely eliminated.
Square columns and beam frames should be preferred instead of thin and long column / shear wall type carrier systems and floor without beams in seismically isolated structures.
Reinforcement with Earthquake Isolation
Earthquake isolation can be used not only in new constructions but also on existing structures. However, beforehand, an expert team must make an assessment in order to understand whether the building is suitable for strengthening with earthquake isolation. After the preliminary checks by the expert team, if there is no obstacle in reinforcement with isolator; It starts with determining the concrete quality of the existing structure (with current core purchases and material tests) and understanding the structural system of the building. Then, the building is modeled with an earthquake isolator and analyzed. Meanwhile, the strength and dimension checks of the structural elements on the floor and ceiling of the floor where the isolator will be applied and the columns are also checked and the strengthening requirement in the structural elements is determined. As a result of these operations, the scope of the construction works to be carried out during the reinforcement of the building with isolator is also determined. Most of the procedures written above are the work that should be done when a retrofit without an isolator is already planned. Regardless of isolator production and assembly, with the determination of the construction works to be carried out, whether the isolator can be reinforced and the final costs of the work are revealed.
Seismic Isolation Devices
Isolation devices used in the world to provide earthquake isolation are basically 3 types: Friction pendulum type (FPB-TDP), lead rubber type (LRB) and high damping rubber type (HDRB).
Friction Pendulum Type TDP Isolation Devices:
Friction pendulum isolation devices are the newest technology used in the field of earthquake isolation and the main advantages over rubber-based devices can be listed as follows:
It eliminates torsion effect in buildings.
Smaller (thinner) devices can be designed according to alternatives.
It is suitable for design and application in very high and very low axial loads and displacements.
With theoretical calculations, its behavior in practice can be predicted very consistently.
It has high fire resistance compared to its alternatives.
In addition to these general advantages, TDP earthquake isolators do not have a lifetime. Steel, stainless steel and teflon containing materials are used in TDP devices. In this way, it does not require maintenance and has a much longer life than reinforced concrete structures. Also, TDP devices do not need to be changed after earthquakes.
TDP friction pendulum type isolators are highly variable in size, size and weight and are designed specifically for the project. The design of the insulators varies depending on many factors such as the weight of the superstructure, the vertical load on each insulator, the seismicity of the area where the building is, the concrete class used in the building, the performance goal of the building, and the architecture.
You can reach our products from here.
Application Steps for Seismic Isolation
In New Buildings
Insulator application is made in the following order in new constructions:
Making soil analysis.
Site-specific earthquake hazard analysis, control and approval of the analysis by TGUA-1.
Preparation of the architecture.
Determining TGUA-5 before starting static calculations and obtaining approval for architecture.
Preparation of static projects with insulators and preliminary analysis.
Isolator manufacturer designing according to preliminary static analysis, building properties and seismicity (determination of isolator budgetary costs).
The static project is analyzed and checked once again with the final isolator parameters, corrections are made if necessary, and the project is finalized. Obtaining TGUA-5 approval.
Production and quality control tests (prototype and production tests) of isolators. With these tests, the design parameters of the isolators are verified.
Installation of isolators at the construction site.
Completion of superstructure construction.
The licensing and approval processes are also progressing at this time. This process, which was very problematic before 2018, was facilitated due to the publication of the new earthquake regulation and the earthquake isolation section in this regulation. In addition, with the applications that started with hospitals, the awareness of the systems in the sector increased, which facilitated the approval processes.
Detailed information about Design Supervisor system, specified as above TGUI, 11.01.2019 dated entered into force upon its publication in the “Resmi Gazete” “Turkey Building Earthquake Regulation Communiqué Regarding the Scope of Things Design Surveillance and Control Service” is found in the document says.
Structures to be Strengthened Against Earthquakes
If the building is contiguous, it cannot be applied or it should be applied to all structures that are adjacent at the same time.
There must be an extra and empty floor where the isolator will be applied (warehouse, parking lot, etc.). Otherwise, the floor where the insulator is placed will not be insulated.
Although the building itself will not be touched and residents will not need to evacuate their belongings, it will be necessary for the residents of the building to be absent while working on the foundation of the building (within the framework of OHS rules).
On the floor where the insulator will be applied, it is very likely that the structural elements will need to be reinforced extra.
In order to clearly understand whether the building is suitable for strengthening with an insulator, an expert team must first see the building, then check the strength of the structural elements and perform preliminary analyzes by creating the static model of the building. The strength of the building, the shape of the session and its architecture affect all this process.
Apart from these articles, the processes written for the standard structure are valid.
Costs of Seismic Izolators
There is no price list for TDP earthquake isolation devices. The reason for this is that insulators are specially designed for each project and their dimensions vary according to many factors. Insulator dimensions and therefore prices vary depending on many factors such as the weight of the superstructure, the vertical load on each insulator, the seismicity of the area where the building is located, the concrete class used in the building, the performance goal of the building, and the architecture. After determining the seismicity of the region with the preliminary static results of the project, a budget study can be carried out and prices can be determined.
Note: As a domestic manufacturer, after entering the market in 2016, earthquake isolators are now available in our country. Today, as TİS, we are able to perform earthquake isolation applications at prices like half or even one quarter of the prices in 2015 and previous years, when we are not in the market yet, on a turnkey basis and in accordance with all national / international specifications and regulations. Also, without any dependence on abroad, the whole process related to the earthquake isolation (R & D, design, manufacturing, testing, assembly) we yürütebilmekt in Turkey. Prior to 2015, this process, which progressed completely with its design, production and tests, became localized with the establishment of our company TİS in 2015. First, the Ministry of Health published in 2013 and 2018 and «1. and 2nd degree earthquake zone are 100 beds and above to be constructed as isolated earthquake all hospitals »necessity of bringing circulars, and then entered into force in 2019″ Principles for the design of buildings under the Influence of Earthquake »with earthquake regulations in civil engineering practice in Turkey earthquake isolation important has come a way.
At this point, the most important issue to be considered is that structures with earthquake isolators can continue to be used immediately after the earthquake. This means that the structural and non-structural damage that will occur after a possible earthquake is completely prevented and possible repair costs will not be experienced, and this is a performance that can never be achieved in a structure designed without an insulator. For example, people living in a house designed with earthquake isolators and properly applied will be able to continue to sit in their homes even after the maximum expected earthquake in the region, and will not bear any repair costs or the psychological burden of the earthquake.
The effects of earthquake isolation application during the first construction phase and after a possible design earthquake are shown in the file named “Earthquake Resistant Design Options”.
Structures Which Cannot Be Applied For Seismic Isolation
Seismic isolation cannot be applied for adjacent regular structures.
It is not correct to apply earthquake isolation in buildings with liquefaction risk.
It is not correct to apply earthquake isolation alone in very high and tower type structures (12-13 floors and above). Applications in such structures should be made with extra damping devices.
Strengthening projects start with the examination of the existing structure by expert teams and determining whether it is suitable for strengthening with earthquake isolation.
All projects that are considered to apply earthquake isolation must first start the project in consultation with experts in the relevant subject.