The consecutive collapsing buildings revealed the state of the megacity: There are around 50 thousand risky buildings in Istanbul.

Yıldız Technical University Department of Civil Engineering Faculty Member Prof. Dr. Ali Koçak made alarming statements following the collapse of two buildings in Istanbul's Bahçelievler district. Koçak said, "Unfortunately, there are around 50,000 risky buildings in Istanbul. So, there must be at least 1,000 buildings in each district."

BUILDINGS COLLAPSED ONE AFTER ANOTHER IN ISTANBUL

Less than a month after the collapse of a 3-story building in Küçükçekmece, another collapse incident occurred in the city. A 7-story building with 3 illegal floors partially collapsed in Bahçelievler in the morning. A few hours later, a 4-story building in Bahçelievler also experienced a collapse on its roof. These consecutive incidents raised questions about how many buildings in the city are at risk of collapsing.

"EXTREMELY POOR QUALITY CONSTRUCTION"

Prof. Dr. Ali Koçak, a faculty member at Yıldız Technical University, stated that the biggest problem with the collapsed building in Bahçelievler was its illegal construction. Koçak examined the materials used in the building and said, "The concrete and steel used are not suitable for a 7-story building. The construction quality is also very poor. Building a 7-story structure without proper engineering services is already a problem. One of the main reasons for the collapse of the building is that the columns and beams have lost their load-bearing capacity. They couldn't support the building anymore."

"THEY CAN'T BEAR THEIR OWN LOADS"

Koçak stated that excessive corrosion occurred in the columns of the building that collapsed in Küçükçekmece and said that the common characteristics of both buildings were their poor quality, illegal construction without engineering services. Prof. Dr. Koçak said, "These structures have already completed their economic lifespan. They can't bear their own loads anymore. That's why they have started to suffer significant damage. These structures need to be demolished or strengthened and reopened. But it is essential to examine them, identify risky buildings, and take them out of service."

"BUILDINGS OVER 30 YEARS OLD SHOULD BE EVACUATED IMMEDIATELY"

Koçak pointed out that in Europe, these types of buildings are always revised and inspected according to the changing regulations. He mentioned that in Turkey, although the regulations have changed four times since the earthquake regulation in 1975, the identification of risky buildings has not been carried out. Koçak stated that after the 1999 earthquake, it was said that inspections and planning should be done, but it was not done. He said, "Now we say that these buildings built before 1999, especially those over 30 years old, should be evacuated, demolished, or reopened after being strengthened. But it is crucial to examine them, identify risky buildings, and take action."

Prof. Dr. Koçak emphasized that local governments should be more careful in these matters and continued, "First of all, they need to know very well the existing building stock and which buildings are risky. Then they should sit down with the Ministry and say, 'How can we rehabilitate these risky buildings?' If necessary, universities and professional chambers should be involved, and a method should be developed for these buildings."

"WE GOT USED TO EARTHQUAKES, LET'S NOT GET USED TO THIS"

"How can we make these buildings regular and prevent loss of life?" Our main goal should be to prevent loss of life. For this, we need to conduct building assessments, create inventories, and determine the method. They always say before the elections, 'Our priority is earthquakes, improving the quality of buildings.' Now we have to do it. When we said after 1999 that our buildings should not collapse in earthquakes, now we say that our buildings should not collapse on their own. We got used to earthquakes, let's not get used to this."

"NOT EVEN 1% OF THE INSPECTED BUILDINGS HAVE BEEN STRENGTHENED"

Koçak mentioned that they examined many buildings as a university after the earthquakes in Kahramanmaraş on February 6th and said that they received many core samples. He said, "I went to many buildings and asked, 'Do you have a plan? Your building is risky, what will you do next?' There is nothing, it remains the same. Maybe not even 1% of the total inspected buildings have been strengthened. But at first, our citizens were eager to have their buildings inspected because they were afraid of earthquakes. Yes, we are afraid, but now we are starting to fear that our buildings will collapse on their own."

"THERE ARE AROUND 50,000 RISKY BUILDINGS IN ISTANBUL"

Prof. Dr. Koçak stated that the Ministry announced that there are around 600,000 risky buildings in Istanbul, while Istanbul Metropolitan Municipality announced 300,000. He said, "I can say with certainty that 50,000 of them are in this condition. Because these are buildings that are over 40 years old. This one is also like that, built in 1980. Then, 2-3 floors were added illegally in 1995. Unfortunately, we have around 50,000 buildings like this. So, there must be at least 1,000 buildings in each district."

"THEY SHOULD NOT BUY BUILDINGS WITHOUT CONDUCTING THOROUGH RESEARCH"

Koçak warned citizens to check whether a building has a permit and engineering services before buying or renting a house. He said, "They should go to the relevant municipality and ask, 'I'm renting this place, is it earthquake-resistant? Does it have earthquake insurance?' They should ask these questions.When buying a building, if it is before 2000, they should definitely not buy it without conducting thorough research and making accurate assessments. They should also have the building that was purchased after 2000 checked by engineering services. Only after the inspection should they proceed with buying the buildings. Otherwise, the cheapness or location of the building does not matter. They should question the ground it is built on, the quality of the building, and whether engineering services and proper inspections have been carried out before purchasing the building. "

"UNCONSCIOUSLY BUILT BUILDINGS BEFORE 1999"

Prof. Dr. Hasan Yıldırım, a faculty member at Istanbul Technical University's Department of Civil Engineering, explained that buildings were constructed without considering the quality of concrete and the use of steel, without obtaining engineering services, and without the strict control and supervision that exists today. He stated that the consequences of this were experienced during earthquakes. Yıldırım also mentioned that although the buildings were not built perfectly after the earthquake, inspections were introduced and buildings started to be constructed with engineering services.

"MOST CONSCIOUSLY BUILT BUILDINGS ARE STRONG"

Yıldırım pointed out that poorly maintained buildings should be distinguished into two categories: those built without the presence of an engineer and those built according to old regulations. He stated that buildings constructed according to old regulations and with engineering services are not earthquake-proof. However, if the ground was examined according to the conditions of that time and the project was designed accordingly, most of the buildings are still standing strong. Buildings that collapse on their own fall into a different category.

"WHAT HAPPENS IF YOU USE MORE CEMENT?"

If no engineering services were obtained, and a certain amount of cement and sand were used, people would say, "They used too little cement." What would happen if they used more cement? There used to be bagged cements. 40% of these were additives, not pure cement. They would pour concrete for 6 bags for concrete 160, and 7 bags for concrete 225, according to their own preferences. They would buy what the hardware stores sold. They were cheaper compared to pure cements.

Since there are no cements like CEM 1 42.5, 52.5 today, there was already a problem in achieving the correct dosage even if these bagged cements were used correctly and the materials were clean. In addition, the materials used in Istanbul, such as seashells, or materials like sand and gravel from rivers in Anatolia, when combined, resulted in poorly constructed buildings before 2000. These buildings already had no load-bearing capacity. "

WHY DID THE BUILDINGS COLLAPSE?

Prof. Dr. Yıldırım emphasized that buildings can collapse not without reason but due to two factors. He said, "First, if you make changes to the columns or walls of a building without consulting an engineer, I don't think about this. We should consider the second factor in these buildings. They built 1, 2, or 3-story buildings, poured concrete by hand, used cement and materials. When tests are conducted, we will see the concrete and speak more clearly. Let's take a core sample right away. I wonder if the foundation was built according to that ground?"

"GOOD QUALITY CONCRETE DOES NOT MEAN A GOOD BUILDING"

A building is not considered good just because the concrete quality is good. If it collapses for no reason, it means that the concrete quality was not good and the steel rusted. When the steel rusts, it causes the concrete to expand. If you then add several floors to a place that is already unable to carry its own weight, the building will not collapse on the day it was built, but as time goes by, corrosion and rust progress, the concrete cracks, and it becomes unable to carry its own weight.

"IF YOU BUILD AN UNCONSCIOUS BUILDING, IT WILL EVENTUALLY COLLAPSE"

When a building no longer has the strength to withstand, it will collapse. It is highly likely that a building with no calculations, poor material quality, and no engineering services will eventually collapse. Yıldırım stated that it is not possible to give a precise number for buildings in Istanbul that are at risk of collapsing on their own, as these buildings are already destroyed during earthquakes. He said that there are many buildings that are likely to collapse during an earthquake, but it is difficult to estimate the percentage of buildings that will collapse on their own.