Depreme Dayanıklı Yapılar | Sismik İzolasyon, Deprem Yalıtımı | Seismic Isolation

What is Seismic Isolation

Seismic isolation, also known as the base isolation system, is one of the most popular ways to protect a structure against earthquake forces. Seismic isolation is a collection of structural elements that significantly separates a superstructure based on a rocking ground from its substructure, thereby preserving the integrity of a building or exterior structure.

Foundation isolation is one of the most powerful tools in earthquake engineering of passive structural vibration control technologies. Insulation can be achieved using a variety of techniques such as rubber bearings, friction bearings, ball bearings, spring systems and other means. It is intended to ensure that a building or external structure will recover from the impact of a potentially devastating earthquake through an appropriate initial design or subsequent modifications. In some cases, the application of seismic isolation can significantly improve both the seismic performance of a structure and its seismic sustainability.

The basic isolation system consists of isolation units with or without isolation components:

  1. Isolation units are the basic elements of a seismic isolation system intended to provide the aforementioned decoupling effect (the term used in sound insulation that is not transmitted to the next floor) to a building or outdoor structure.
  2. Isolation components are connections between insulating units and parts that do not have a self-decomposition effect.İzolasyon birimleri kesme veya kayma birimlerinden oluşabilir.

This technology can be used for both new structural design and seismic reinforcement. During the seismic retrofit process, some of the most important US monuments, eg: Pasadena City Hall, San Francisco City Hall, Salt Lake City and the County Building or LA City Hall, were installed in seismic isolation systems. It required provisions against tipping and the P-Delta Effect, as well as creating stiffness diaphragms and ditches around buildings.

Seismic isolation is also used on a smaller scale. Isolated raised floor systems are used to protect foundation equipment against earthquakes. This technique is included to preserve sculptures and other works of art. Seismic isolation units consist of Linear motion bearings that allow the building to move, oil dampers that absorb the forces caused by the movement of the building, and laminated rubber bearings that allow the building to return to its original position when the earthquake is over.

Providing Earthquake Resistance

Due to large and small earthquakes that occur frequently in Turkey, which is on the seismic belt, capillary cracks occur in the raft main and shear concrete of the buildings. If the waterproofing program made in the manufacturing step is damaged by the effect of time, the air and moisture developed from these cracks quickly rot the iron reinforcement inside the crack. In subsequent jolts, the iron reinforcement that rots and thins during the crack breaks and breaks. For this purpose, the waterproofing created on the main and load-bearing reinforced concrete walls of the buildings is very important in terms of their durability against earthquakes.

In our country, there is currently no regulation on waterproofing in buildings. For this purpose, the selection and application of waterproofing products is entirely at the discretion of construction companies and contractors. And unfortunately, wrong and incomplete programs are made in this regard. It is very difficult to compensate for the mistakes created in the insulation of the parts of the buildings that remain under the ground (foundation structures). This issue is often neglected; As a result, the equipment is damaged.

In our country, a program is carried out regarding the waterproofing of the main and carrier curtains, which play a very important role in the statics of the buildings, with the aim of preventing water from entering the interior. However, the task of the waterproofing created on these parts of the buildings that are under the ground is to protect the reinforcement first.

When earthquake disasters in our country are examined, it is seen that most of the collapsed buildings have weakened due to corrosion caused by humidity. The water absorbed by the building degrades the chemical nature of the materials and reaches the reinforcing bars with bearing quality, causing corrosion. In buildings without waterproofing, reinforcement bars lose 70% of their bearing quality within 10 years. The building, weakened by all these conditions, cannot resist against natural disasters.

Waterproofing in buildings is one of the individual measures to be taken to ensure life safety in earthquakes. Healthy waterproofing acts as a shield against earthquakes for buildings. Therefore, waterproofing of all existing and new buildings is the first requirement for earthquake resistant structures.

Waterproofing in buildings is very important for life and property safety. Waterproofing accounts for only 3 percent of the total building cost. In our country, where 92 percent of it is in seismic band, insulation is not an additional cost, but construction insurance. According to the latest data, more than 7 million houses in our country can be considered as risky in terms of earthquake safety. Therefore, the final consumer has a great responsibility in this regard. When you buy a house, build a house or insulate your home, you should make sure that it is quality insulation with CE certified materials that meet the standards.

Beton EvConcrete Houses Withstand Earthquake

In reinforced concrete construction, the combination of concrete and steel provides the three most important properties for earthquake resistance: hardness, strength and flexibility. Earthquake damage studies consistently show that well-fixed shear walls are the key to earthquake resistance in low-rise buildings.

Optimal design conditions include curtain walls that expand the entire height and are located on all four sides of a building. Long walls are stronger than short walls, and solid walls are better for windows and doors than those with a lot of openings. These elements are designed to survive severe lateral (in-plane) forces called racking and shearing without being damaged or bending too much. Shear walls must also fit well into the foundation structure to function effectively. Properly installed steel reinforcing bars run along the joint between the walls and the foundation to provide a secure fixation to the foundation.

Why Buildings Fail

Low-rise buildings, which are most vulnerable to earthquakes, have the necessary stiffness, strength and flexibility to resist the forces of an earthquake or have poorly bonded walls to a solid foundation or both. Three types of buildings sustain the most significant damage:

Multi-storey buildings with the ground floor only consisting of columns

Most of these buildings were 3 to 4 floors with a garage or a living area on the ground floor with many large windows. The columns may have been strong enough to lift the structure, but did not provide sufficient rack resistance during a seismic event. The upper floors sometimes tilted to one side when the earthquake shook the building from side to side. Whether made of wood, steel or concrete, they have all been damaged.

Timber frame houses with poor connections between walls and foundation

Timber-framed buildings are naturally flexible, which is a quality during an earthquake. However, the shaking threw some of these houses to one side. The shear walls were strong enough, but the connection to the foundation was a weak point.

Unreinforced masonry or concrete buildings

Masonry or concrete walls not reinforced with steel bars were not flexible enough to be effective curtain walls. And if there is no steel connecting them to their foundation, the connection between the walls and the foundation can be a weak point.

Why is Reinforced Concrete Safe?

Reinforced concrete walls are a composite system: Concrete resists compression forces, and reinforcement steel resists tensile forces from earthquakes.

Concrete is poured around the bars and locked in place. The exceptional flexibility of steel to withstand tensile forces, combined with the rock-like ability of concrete to resist compression, results in an excellent combination of the three most important earthquake-resistance properties: hardness, strength and flexibility. A study at the Building Technologies Laboratories revealed that even a lightly reinforced concrete shear wall has more than six times the rack load resistance of a framed wall construction.

It is not surprising that modern reinforced concrete buildings have rarely survived significant damage from these recent earthquakes.