Academy

Earthquake Safety in Buildings

Earthquake is a natural disaster which is unpredictable among natural events and whose negative effects can be sudden and large in size. The effects of earthquake can vary in proportion to its intensity. The greatest effect of the earthquake is realised on the structures, which are an unchangeable part of human life. Therefore, it is inevitable to plan the buildings by taking into account the earthquake effects.

In our country, where destructive earthquakes are frequently experienced, 66% of our land and 71% of our population are located in 1st and 2nd degree earthquake zones. For this reason, it is important that building projects are prepared in accordance with the earthquake regulations and the implementation is carried out in accordance with the projects and regulations. The last regulation prepared in our country belongs to 2018. With the 1999 earthquake, sensitivity to earthquake and building safety has increased in our country, but it is also clear that we are behind the desired levels, especially in practice. The scene encountered as a result of the recent 6 February 2023 earthquakes has clearly demonstrated how problematic structures we are still building in practice despite the 24 years that have passed since the 1999 earthquake. Damage or collapse of the structures despite the fact that the project designs were made in accordance with the regulations showed the fact that we have serious deficiencies at the point of implementation.

What needs to be done in this regard can be grouped under three headings as urban settlement planning, project design and project implementation.

  1. City Settlement Planning and Zoning PracticesThe selection of city settlement areas is very important for protection from earthquake effects. The selection of soils with high soil bearing capacity as settlement areas is the first measure to reduce the negative reflection of earthquake effects on structures. In the recent earthquake of 6 February 2023, the images of the moment of the earthquake reflected on the cameras clearly showed that the ground behaves like a liquid in many residential areas. For this reason, it is very important to select areas away from fault lines and with solid ground when planning urban settlement. The structures to be constructed in areas with solid soils will have advantages in terms of construction cost since they will not need ground reinforcement (bored pile and jet grout applications, etc.). On the other hand, in soils with liquefaction characteristics, if no additional reinforcement is foreseen for the ground, damages such as overturning or sinking into the ground can be seen even if there is no collapse, no matter how solid structures are built. Agricultural lands, water basins, stream beds, alluvial soils, coastlines are generally not suitable for settlement. When it is necessary to construct a building on such soils, necessary ground reinforcement calculations should be made and projects should be prepared. In this framework, geotechnical engineering should be given more importance. On the other hand, it is important to make some changes in the zoning regulations, which are taken as basis in the architectural design of buildings, in order to reduce earthquake casualties. Practices such as avoiding high-rise buildings as much as possible, putting an end to the practice of contiguous order buildings, taking island-based project design as a basis, increasing the share of green areas in the urban settlement are the issues that will provide advantages in reducing the losses caused by earthquakes and intervening in damaged buildings.

     

  2. Earthquake Regulations and Project Design

    The first condition for the emergence of a building is to have a project. Project design is indispensable in terms of both the robustness of the structure, the inclusion of the needs and aesthetics for use within the structure and economic solutions. Project design generally includes ground survey report, ground reinforcement and shoring projects if necessary (to prevent excavation risks), architectural project, static project, electrical and mechanical projects.  Project design starts with ground investigations. The purpose of ground surveys is to determine the bearing capacity of the ground on which the building will sit and to determine whether there is a need for improvement in the ground according to the condition of the structure to be built. Geological engineers make these determinations and put them in the project file as a report. The static project of the building is prepared within the framework of the data and recommendations of this report. When architectural projects are prepared, it is important that they do not contain some structural irregularities specified in earthquake regulations. When static projects are prepared, it is important to act primarily with the assumptions specified in the earthquake regulations. Earthquake ground motion levels to be taken as basis in the design of new buildings and evaluation of existing buildings under earthquake effect are defined in the earthquake regulation. The earthquake effects corresponding to these earthquake ground motion levels are defined by the Earthquake Hazard Maps of Turkey, which were put into force with the decision of the Council of Ministers dated 22/01/2018 and numbered 2018/11275. These maps can be accessed from the website https://tdth.afad.gov.tr/. Within the scope of this regulation, the following four different earthquake ground motion levels are defined:

  3. Earthquake Ground Motion Level-1 (DD-1)

    DD-1 Earthquake Ground Motion characterises a very rare earthquake ground motion with a 2% probability of exceeding the spectral magnitude in 50 years and a corresponding recurrence period of 2475 years. This earthquake ground motion is also referred to as the largest earthquake ground motion considered.

  4. Earthquake Ground Motion Level-2 (DD-2)

    DD-2 Earthquake Ground Motion characterises the rare earthquake ground motion where the probability of exceeding the spectral magnitudes in 50 years is 10% and the corresponding recurrence period is 475 years. This earthquake ground motion is also referred to as standard design earthquake ground motion.

  5. Earthquake Ground Motion Level-3 (DD-3)

    DD-3 Earthquake Ground Motion characterises frequent earthquake ground motion where the probability of exceeding the spectral magnitudes in 50 years is 50% and the corresponding recurrence period is 72 years.

  6. Earthquake Ground Motion Level-4 (DD-4)

    DD-4 Earthquake Ground Motion characterises very frequent earthquake ground motion where the probability of exceeding the spectral magnitudes in 50 years is 68% (50% probability of exceeding in 30 years) and the corresponding recurrence period is 43 years. This earthquake ground motion is also called service earthquake ground motion. According to this regulation, Building Performance Objectives to be taken as basis in the design of new buildings under earthquake effect and in the evaluation of existing buildings and Earthquake Design Classes (EDS) depending on these objectives are defined. Since the cost of the building will vary according to the preferred level, the preference of the building owner should also be asked in this regard. Building Performance Levels and definitions for building structural systems under earthquake effect are given below:

 

  1. Project ImplementationIt is important to consider and implement the actions to be taken to prevent or minimise earthquake damages as a whole. This issue can be evaluated under three main headings:

     

  2. Construction Phase Application Errors

    In the application phase, concrete casting defects and reinforcement binding errors are prominent in reinforced concrete structures. Adding water to the concrete at the construction site during concrete casting, waiting for the concrete more than necessary, not performing vibration as much as necessary, not curing after concrete casting are among the most common mistakes. Curing of concrete is very important especially in hot weather. Concrete without curing will have a brittle structure with the effect of increasing internal temperature and will experience serious loss of strength. It is an important deficiency that the stirrup hooks in the reinforcements are not made in the project angle. Failure to pay attention to the placement that will allow the concrete to pass through in frequent reinforcement areas will cause voids in reinforced concrete elements. It is also important to perform the formwork workmanship properly and to pay due attention to in-form cleaning and rust allowances. The possibility of error in steel structures is lower compared to reinforced concrete manufacturing due to workshop manufacturing. However, workshop and field controls are important in terms of the compliance of steel fabrications with the project and regulations. The only way to prevent these errors is to carry out construction applications under the supervision of technical personnel and to make the inspection mechanisms of official administrations more functional.

  3. Post-Construction Changes

    Interventions to the structural system in finished buildings are one of the most important causes of damage during earthquakes. In existing buildings, applications that will adversely affect the behaviour of the building during an earthquake such as columns cut to expand the usage area, interventions to columns and beams for additional installation passages, and additional attics and mezzanines can be seen. In order to prevent such changes, it is important to inform the society through educational programmes. In addition, it is important to establish a system where such changes can be reported and complained, and to take measures to punish those responsible and to compensate for the error. It is clear that the penalties to be imposed on those responsible should be deterrent and the imposition of definitive provisions on this issue will be beneficial in preventing future disasters.

  4. Retrofitting in Existing Buildings

    Another method to protect against earthquake damages and losses can be the retrofitting of risky buildings. Two possibilities can be evaluated in existing risky buildings. One is the demolition and reconstruction of the building and the other is retrofitting. Here, the result of the cost-benefit evaluation will be effective in making the right decision. In the retrofitting of existing structures, it is essential to design the project within the framework of earthquake regulations. In order to make a retrofitting project, if there is a project of the existing structure, retrofitting calculations can be made through that project. If the existing building does not have a project, the process of collecting data about the structural system must be carried out from surveying the building to modelling, taking samples from the structural system and performing tests. Within the framework of the collected data, the retrofitting system should be decided and the project design phase should be started. Steel, reinforced concrete and FRP systems are used in retrofitting applications. These systems can be generally wrapped around the existing structural systems or they can be designed as additional structural elements. In addition, seismic isolators can be applied to the columns in existing buildings to provide the opportunity to absorb earthquake movements of the building.

Contact Now

Fill out the form and we will call you as soon as possible.

Green Services Enerji Elektrik A.Ş.