How Resistant to Earthquake Is Your House?

Turkey is an Earthquake Belt Country:

Unlike many countries, Turkey is truly an earthquake-prone country. We all know this, maybe many of us have experienced the moment of the earthquake, maybe there are those among us who have suffered painful losses in our families, relatives, acquaintances. Whenever there is a major earthquake disaster, experts start to make various comments on the screens. These publications are also beneficial for raising the awareness of the society, I have no objections. But this issue usually stays at that stage, we all get upset for a while and then forget about it.

There are many inexpensive test methods to check the soundness of our buildings. Among the non-destructive methods, ultrasonic tests and concrete hammer test (Schmidt hammer) are the most used methods, and the damaged method, I can count the determination of concrete quality by taking a core sample and breaking it in the laboratory. It is called damaged because it is necessary to drill the concrete.

Contributions of Necdet Burgul and Ali Terzibaşoğlu to My Engineering:

When I finished university, I decided to become a project engineer instead of going to construction sites like many of my friends. I think that my decision to start working as his assistant assistant to the late Necdet Burgul, who was one of the veteran engineers of Turkey and who built some of the first sugar factories, during the years that I extended the school was effective. With his advice, as soon as the school ended, my main teacher, who we recently lost, Dr. I started to work as a project engineer with Ali Terzibaşoğlu. I worked with him for quite a while and learned a lot about engineering from him. I pay homage to both of them.

It had been several years since the Erzincan earthquake. After the earthquake, they carried out reinforcement works in cooperative buildings with the loan of the world bank, and the consultant firm and the contractor could not come to an agreement on some issues during the delivery of the work. They decided to apply to the independent quality control inspectorate. I think it was 1995. At that time, there was a separate department related to earthquakes in the civil engineering department of Istanbul Technical University, they applied to this department. They also brought the matter up to our office, to Mr. Ali.

Mr. Ali is a graduate of ITU, he was a veteran engineer who also contributed to the board that prepared the revised new construction standards that we use today. Back then, before the construction standards were revised, we used to prepare projects at world standards with different methods.

My Onsite Investigation After the Erzincan Earthquake:

Ali Bey sent me to Erzincan, I examined what was done for about four months, and I had the missing or faulty reinforcement works corrected by consulting Ali Bey from time to time.

In one of the buildings, the cooperative performed so badly that we could not decide, by simple tests or by visual inspection, whether the reinforcement work by the contractor was sufficient. Concrete tests came out fine, but the look was disastrous. The consultant wanted the building to be demolished, and the contractor was saying why didn't you tell him in time.

At this stage, I need to give some technical information beforehand in order to explain the subject better:

Technical Information about Earthquake and Building Relationship:

As you know, the earthquake creates a tremendous vibration as a result of the breaking of the fault lines between the rock layers underground, and because this vibration creates horizontal and vertical forces in the structures, if the structure or building cannot bear the force, the concrete carcass that cannot withstand the load will break and the building will collapse.

Vibrating waves have periods, just like waves in the sea. The sound of the waves hitting the beach is in all our ears, but the waves hit the beach at regular intervals. Likewise, seismic waves are vibration waves and act like superimposed waves.

Every structure also has natural periods. Let me explain what I mean by natural period with an example. For example, if we pull a tree sapling a little bit and leave it to ourselves, it starts to shake from side to side. The period of this shaking changes from sapling to sapling in proportion to the length of the sapling and the thickness of its trunk. You can imagine me saying this with other things as well. For example, when we were little, we used to have wooden or plastic rulers, 30 cm. or 20 cm. I used to like to play with rulers. If you stretch the tip a little too far from the ordinary, it will vibrate more slowly, if you hold it shorter, it will vibrate more often. We call these vibration periods the natural periods of the structure.

Structures also behave like saplings or rulers, all with one dominant but several vibrational periods. Here, if the vibration periods of the earthquake coincide with the natural periods of the structures, the structure enters resonance and especially the lateral forces acting on the structure become very large.

Calculation of Natural Periods of Buildings and Earthquakes:

The natural periods of the buildings can be calculated from the project. The periods of earthquake waves are also known from the records of earthquakes that have happened so far. While designing the building, you can build the height you want by paying attention not to overlap the two periods. This is how they build tall buildings in Japan, even in earthquakes bigger than ours, the buildings do not collapse.

In addition, there are new new methods, sometimes sliding supports are made under the columns of the buildings, and sometimes some measures can be taken to absorb the earthquake load on the top of the building. If the natural periods of the building are close to the periods of earthquake waves during the design phase, the natural periods of the building can be changed with such measures.

Let's come to my Erzincan adventure. I say adventure because after working as a project engineer for all these years, the construction site environment was interesting. Anyway, what was I saying, one of the buildings had really bad concrete work, it probably snowed while pouring the concrete of the building and there were gaps in places because they didn't clean the mold. Concrete quality was normal, but we had to decide whether to demolish the building and rebuild it or whether the reinforcement was sufficient.

The professors at ITU talked about a device in the Kandilli observatory. Now maybe there are other places than this device. There was only one then. We called, they accepted, they came to Erzincan as a team, we met the team and we got down to business immediately. The system works like this. You mount the device on the top of the building and, by controlling it with a computer, you gradually increase and vibrate the building. Sensors that can sense vibrations are placed in each corner of the building, all of them are connected to the computer by cables at that time, and the building starts to resonate when the given vibration approaches the building's natural periods. It starts shaking like an earthquake. Of course, an expert who knows this process should do it, if you vibrate exactly in the natural period, you will destroy the building due to resonance. Just as the soldiers marching on the bridge at a brisk pace demolished the bridge from shaking.

In this way, the natural periods of the completed structures can be extracted. It is possible to check whether it holds with the project values ​​and decide on the robustness of the building according to the result. If the project is calculated as earthquake resistant, there is no problem when the values ​​hold. This means that no mistakes were made during the construction, or if the building has experienced an earthquake before, cracks have formed in some parts that we cannot see, or if the natural periods of the building have changed, it is obvious because it does not match with the project values.

In those days, when we examined the values ​​we obtained from this test, we understood that the building I mentioned had been strengthened enough with the reinforcement. We had decided not to demolish the building by filling the gaps in the concrete with repair mortars. Because I like the construction site environment, I worked as a project engineer in Ankara for a short time and then went to Moscow to the construction site.

This is the method I mentioned is the most accurate method for controlling buildings. Now, most likely, these devices are new. Vibration sensitive sensors are now probably wireless as well.

Other Methods, Supportive Tests:

I think it is possible to control buildings in a very practical way with this method. Of course, as in all matters, this method alone is not enough to take the right decision, it is necessary to test the concrete quality separately, it will be useful to see if there are cracks or something with an ultrasonic test. By comparing the project values ​​of the buildings with the results of the tests, really problematic buildings can be identified in a short time. Accurate information can be obtained, not guesswork.

With the right information, it will be possible to find the most economical solution. Without the right information, this one often looks cracked bad, let's tear it down, leave it that way, making predictive decisions. Maybe the crack that is visible is just a crack in the plaster or a brick wall.

Sometimes, wrong decisions are made by only doing the concrete hammer test and saying that the concrete quality is poor. The hammer test does not always give accurate information. It is only for local tests anyway, you only get information at the point where the test is done. The test I mentioned makes it possible to obtain more accurate information as it can control the entire building.

With the right information, it is now easy to decide what action to take. Maybe problematic buildings should be demolished, maybe reinforcement should be done. This decision is now the job of experts, not politicians or rent-seekers.

We have so many universities, we have so many engineers, but the education level is also very insufficient. It is not easy to find a specialist with us.

As a graduation project at universities in Japan, students make model building carcasses, all models are placed on a vibrating platform and tested. If your model is destroyed, you cannot graduate.

We're back to the problem of education again, right? But this is our situation, unfortunately, we do not have enough trained staff. Engineering education is very inadequate in many universities.

Earthquake Preparations are Important:

Before the upcoming big Marmara earthquake, we really need to take precautions without wasting any more time. And we have to do it in the most economical way. Something is being done, I know, but I think the topic is a bit off the agenda these days. At least, I can't read much news about these issues in the press anymore.

If we do not want to suffer again as in previous earthquakes, my opinion is that we should leave the daily political conflicts aside, perhaps accept this issue as above politics and put it under the control of an independent committee consisting of experts and professional experience. In this way, at least with the right methods, we can primarily identify the really problematic buildings.

If we can save the problematic buildings with retrofit methods, this board should decide.

I think we do not have much time left, it is time to find a solution to this issue across the country. I hope we will make the right decision as soon as possible.

Love and regards from Moscow