Common Misconceptions!
"I built this reinforced concrete building according to the regulations; it will never be damaged in any earthquake."
"Old buildings are safe."
"New buildings are safe."
"The ground of this structure is rocky, so nothing will happen."
"The contractor of the building lives here, so he must have built the building properly."
"More reinforcement (steel) was used in this building than the project required, so it's very safe."
"The building was constructed before 2018 so structure does not have any chance to pass performance evaluation based on the new regulations."
"Sea sand was used in our building; our building is weak."
1. What is Seismic Performance Analysis?
Seismic performance analysis involves assessing whether a building meets the target performance level defined for a specified earthquake scenario, as outlined in the latest Turkish Earthquake Code. In simpler terms, it determines the damage state of a building during a potential earthquake. This analysis is essential for identifying deficiencies and developing retrofitting designs to address these issues. Speaking of damage, it’s important to clarify this concept. It is unrealistic to expect reinforced concrete buildings to sustain no damage at all. These buildings are designed to absorb earthquake energy by sustaining damage. The aim is for the damage to occur in specific areas, such as beams rather than columns, and to ensure the damage is ductile—meaning the structure retains its load-bearing capacity—rather than brittle, which results in sudden failure. In summary, reinforced concrete buildings are designed to sustain controlled damage, which is not something to fear.
2. What Should Be Done for Seismic Performance Analysis?
The process begins with understanding the building and its surroundings to create an analysis model in a computer environment. Various steps are taken to gather information about the materials used in the building (concrete, reinforcement, steel, etc.), soil conditions, structural system, and the load distribution within the building. Once the necessary data is collected, a model is created and analyzed in accordance with relevant regulations, taking into account the expected earthquake magnitude in the region. The results of the analysis are then interpreted.
3. Do Information Collection Processes Damage the Building?
One of the most common misconceptions is that procedures like core sampling and concrete scraping cause permanent damage to the structure. The tests conducted to determine material properties can be categorized into two groups:
Non-destructive methods: As the name suggests, these methods are performed without causing any damage to structural elements.
Destructive methods: These include processes such as core sampling and concrete scraping. The temporary damage caused by these methods is subsequently repaired.
In core sampling, the location from which the sample is taken is determined using devices like X-ray machines to avoid damaging the reinforcement. Unfortunately, it is not uncommon to encounter companies in the sector that incorrectly execute these procedures. Once the core sample is taken, the void is filled with high-strength structural repair mortar to restore the area. Similarly, after concrete scraping is performed to observe the reinforcement arrangement, the scraped surface is repaired with high-strength repair mortar.
This might raise the concern of whether the structure or its elements are damaged when samples are taken. If the building is under significant stress due to its own weight, it would typically show visible signs of distress, which a qualified engineer would recognize and might decide not to proceed with the testing. However, it is crucial to emphasize that this is an extreme scenario. Additionally, during the sampling process, a qualified engineer must be present on-site to control the operation.
4. Is There Hope for the Earthquake Resistance of Very Old Buildings?
Considering advancements in technology, progress in the construction industry, and stricter regulations in recent codes, it is reasonable to say that newer buildings are generally safer. The absence of these advancements in older buildings increases the likelihood of issues. However, it would be incorrect to assume that this is universally true for all older structures. If this explanation feels a bit confusing, to summarize: Generalizations are not always accurate. The reliability of a building depends on various factors, such as whether it received proper engineering services during its design and construction, the quality of materials used, soil conditions, and how carefully the building has been maintained throughout its lifespan. Without conducting a proper analysis, it is impossible to make definitive judgments, and any conclusions would remain mere generalizations. Performing seismic performance analysis is not only the technically correct method for evaluating a structure’s safety but also an essential step for determining whether the building can be retrofitted.
5. Is Testing Required on Every Floor, and If So, Why?
Due to the non-homogeneous nature of concrete and the fact that each floor may have been cast with concrete produced at different times, the regulations mandate taking core samples from every floor to achieve statistically accurate results. Similarly, the regulations also require testing on every floor to determine the mechanical properties of the reinforcement (commonly referred to as rebar). In engineering services provided solely for informational purposes, the responsible engineer may exercise discretion based on their evaluation of the building when deciding the extent of testing.
7. Can Buildings with Insufficient Earthquake Performance Levels Be Retrofitted, and If So, How Reliable Are They? Retrofitting or Reconstruction?
In theory, no building is beyond retrofitting—every structure can be strengthened. If a building is found to be inadequate after a performance evaluation, appropriate retrofitting methods (element- or system-level) can be chosen to address its deficiencies, allowing it to remain in service for many years. However, if the cost of retrofitting exceeds 40% of the cost of reconstruction, it may be more practical to opt for reconstruction. This is because the non-structural elements of the building, such as mechanical, electrical, or architectural components, may be relatively outdated and could incur additional expenses in the future. When considering reconstruction, it is essential to ensure there are no bureaucratic obstacles. If the building violates current zoning regulations or if the new structure would result in significant reductions in apartment sizes due to updated zoning plans, residents may view retrofitting as the only viable option.
7. Will My Building Be Demolished If It Is Decided Inadequate After Evaluation?
There is often confusion between seismic performance analysis and the identification of risky structures. A risky structure report is a mandatory procedure for urban transformation, while seismic performance analysis takes a different approach. Seismic performance analysis aims to clearly understand how a building would perform during an earthquake according to the latest Turkish Earthquake Code and, if necessary, to develop retrofitting projects. However, if the results are unfavorable and the building is deemed inadequate, and the owners fail to address these deficiencies, they may face sanctions from local or central authorities.
8. Do All Columns and Beams of a Building Need to Be Strengthened During Retrofitting?
No, this approach stems from inexperienced engineers implementing costly solutions simply to feel secure. A proper seismic performance analysis identifies the deficient elements and system shortcomings, and solutions are developed to optimize improvements based on these deficiencies. For example, if the analysis reveals insufficiencies in only one or two elements, strengthening should be done at the element level. Techniques like FRP or steel jacket can be used to reinforce the specific deficient elements, whether they are columns, beams, or others. If multiple elements are found to be inadequate and addressing each one is impractical from an economic or application standpoint, system-based retrofitting should be considered. This involves altering the structural system’s behavior, such as adding new components to reduce the load on the deficient elements, making them sufficient while transferring the extra forces to the new components. Examples include adding reinforced concrete shear walls, steel braces, or using FRP to strengthen infill walls. In cases where operations must continue uninterrupted, such as in certain industrial facilities, advanced technologies like base isolators or dampers can also be employed for retrofitting.
9. Why Should We Perform Seismic Performance Analysis?
Although we are geographically accustomed to earthquakes, we are equally unprepared for them. In recent earthquakes, we have experienced significant loss of life and property. To prevent such tragedies from happening again, the first step in earthquake preparedness is to assess the safety of our homes—where we spend most of our time—and address their deficiencies, or to construct safe new homes. There is no price that can be placed on human life. We must recognize that it is not the earthquake itself, but the building that causes fatalities, and take preventive measures before we lose our loved ones.
10. What Should We Do If There Are Cracks or Other Damages in Our Building?
The only preventive measure you can take is to show the cracks to a qualified engineer. Cracks should never be repaired without the engineer's inspection. The engineer will then assess whether the cracks or damages are in structural elements (such as columns or beams) or non-structural elements (such as infill walls or plumbing). For structural elements, the engineer will check if the cracks are superficial or deep, and then evaluate the type of crack. The cracks should be monitored, and their growth should be tracked. Cracks that do not pose a threat to the building's safety should be repaired, while any other cracks should be addressed through strengthening measures based on the results of a seismic performance analysis.
11. What Should We Do If the Usage Status of Our Building Has Changed? How Does It Affect the Building?
It is common to see residential buildings being used for purposes other than their original design, such as being converted into workplaces. In these cases, additional loads and factors such as heavy machinery with vibrations—weights not considered during the initial design—can significantly affect the building's behavior. As a result, the adequacy of structural elements must be thoroughly checked. In these situations, where slab flexural capacity deficiencies are often observed, floor strengthening can be implemented. Since this is a common issue, it is important to emphasize again that columns should never be cut to create more space.
12. Is It Possible to Evaluate a Building by Visual Inspection?
According to the Turkish Earthquake Code (TBDY 2018), it is not possible. However, in cases where a comprehensive evaluation is not feasible, observational assessments for informational purposes can be carried out by expert engineers in accordance with international codes such as ASCE 41 or FEMA 154.
13. What Is the Lifespan of Reinforced Concrete Buildings?
Reinforced concrete buildings do not have a fixed lifespan as you might expect. However, when creating design parameters, factors such as economy and safety are considered, and to statistically achieve the targeted probability, the building's lifespan is typically assumed to be 50 years during calculations. The reasons for relatively short lifespans often attributed to reinforced concrete buildings are errors during construction, the absence of engineering services, and environmental impacts resulting from a lack of proper insulation.
14. Is the Statement "In the Event of an Earthquake in Istanbul, No Building Will Survive" True? Should We Trust Engineering?
This statement is not accurate, but since this is a relative question, let’s consider an example from the DEZİM (Earthquake and Ground Survey Department). According to the updated report on the "Estimated Earthquake Loss Predictions for Istanbul" prepared by DEZİM, if the design earthquake occurs in Istanbul, 53,101 lives are expected to be lost. In the case of a major earthquake greater than the DD1 design earthquake, the loss is projected to be 206,148 lives. The average loss in simulation scenarios is 23,350 lives. These potential scenarios are not to be dismissed or forgotten, as even one loss of life cannot be replaced. Therefore, if we take the necessary precautions—by conducting seismic performance analyses and implementing retrofitting measures in the case of deficiencies—we can trust engineering to help eliminate the risks.
15. What Should Be Done for Buildings Where Seismic Performance Analysis Cannot Be Conducted? (If the Owners Do Not Want It)
It should be remembered that seismic performance analysis is a process that benefits everyone in the building. The procedures, results, and benefits of the analysis should be clearly explained. If there is no consensus on proceeding with the analysis, an expert engineer can be brought in to conduct an observational evaluation of the building.
16. Is There a Faster and Simpler Evaluation Method for Our Building, Even If It Is Rough?
While a full evaluation may not be possible, interpretations can still be made based on signs of damage, such as cracks. For this, assistance can be sought from a reliable and expert engineer. However, it should be remembered that these are not exact results. No engineer should say whether a building is safe or not just by looking at it.
17. Is It Correct to Categorize Buildings as Good or Bad Based on Their Construction Years, and What Are the Most Important Factors Affecting a Building's Earthquake Resistance?
It is undeniable that technological advancements and the increasing knowledge in the sector have improved quality. Of course, older buildings are more likely to be at higher risk compared to newer ones. However, the reliability of a building depends more on factors such as the materials used, maintenance, whether engineering services were provided, the type of foundation, and the location, rather than solely on the construction year. These engineering and other parameters play a much more significant role in determining the building's earthquake resistance.
18. What Are the Common Misconceptions About Earthquake Performance Analysis and Buildings?
· "This reinforced concrete building was built according to the regulations, so it won’t be damaged in any earthquake."
Reinforced concrete buildings are designed to sustain damage in a controlled manner rather than avoiding it altogether. The goal is to absorb seismic energy by allowing plastic (ductile) deformation, not brittle failure. If built to code, it is expected to sustain damage at specified locations, but without losing structural capacity.
· "Old buildings are safe, or new buildings are safe."
The perception that old buildings, especially historic ones, are safe comes from the fact that a few well-preserved structures have survived to this day. However, these are rare examples and do not represent all buildings from that era. Generalizations about the strength of old or new buildings are not accurate. Structural reliability depends on the quality of construction and materials, not the age of the building.
· "The building is on rocky soil, so it won’t be affected by an earthquake."
The ground is just one factor that affects the performance of a structure, so having good soil alone does not necessarily mean a building will perform well. Additionally, good soil can sometimes lead to negative outcomes under certain conditions. For example, excavating rocky soil requires dynamite or powerful machinery like heavy-duty excavators. Therefore, most structures do not sit on rocky ground.
· "The contractor lives here, so the building he constructed is strong."
Good intentions do not necessarily lead to good outcomes. Many construction mistakes are made due to lack of knowledge or poor execution, not bad intentions. It is crucial to rely on skilled professionals to ensure structural integrity.
· "The building has more rebar than the original design, so it’s much stronger."
Adding more reinforcement than specified in the design is not a guarantee of improved strength. It could create issues such as altering the behavior of structural elements, turning ductile elements into brittle ones, or causing stress concentrations that reduce overall safety.
· "The building was constructed before 2018, so it won’t pass a performance evaluation according to the new regulations."
Building codes have evolved over time, and newer regulations bring important improvements. However, even older buildings designed under past regulations can be assessed and retrofitted according to current standards. The most important factor is whether engineering services were involved during construction, not just the year it was built.
· "Our building survived the 1999 earthquake in Istanbul without damage, so it’s safe."
If your building were in Kocaeli, this would be a relevant factor, but for buildings in Istanbul, which is far from Kocaeli, the 1999 earthquake is not a very significant indicator. The distance from the earthquake's epicenter to the building, the soil class in the affected area, the magnitude of the earthquake, and other factors influence the potential damage. A conclusion should not be reached based on insufficient arguments alone.
· "Our building was constructed using sea sand, so it’s weak."
Using untreated sea sand can lead to corrosion of the reinforcement, which is dangerous. However, if the sea sand is properly processed, washed, and purified of harmful substances, it can be safely used in construction. It’s not the sea sand itself that’s the issue, but rather improper use without necessary precautions.
· "Can my building be strengthened and made safe just by asking?"
Questions and comments like "Can my building be strengthened and will it become solid?" should be approached with caution. Every building can be strengthened, but determining how it should be strengthened and whether strengthening is the optimal solution requires a full evaluation. Just as you wouldn't expect a doctor to diagnose and treat you without necessary tests (X-rays, MRIs, etc.), your building also requires tests and analyses to provide a healthy (correct) assessment.
19. What Are Your Final Words?
It should be remembered that sharing knowledge does not diminish it; on the contrary, knowledge grows as it is shared. Therefore, we are always happy to welcome young colleagues or senior professionals to our office. Thank you for taking the time to meet with us.
