Earthquake Thoughts and Facts
Sent by Necil Engür, an expert civil engineer and an old friend
Translated from my original Turkish post. I used Google translator then I fine tuned it in a haste. Hopefully, it makes sense as much as the original does.
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As a Civil Engineer, who worked as a project manager for 25 years and as a manager in the field applications of Turkey's important projects for 20 years, I would like to share the following opinions about the Earthquake Disaster that took place in our country, based on my knowledge and experience. I did project / calculations / design in accordance with the 1975 and 1997 Earthquake Regulations. As many of my colleagues, engineers who do many projects/designs/calculations and many of my professors have said, I can say that the last Earthquake Regulation published in 2018 is the best regulation, which is very detailed and prepared by considering the real behavior of structures against horizontal loads. — Necil Engür, Civil Engineer, BEng, MEng, İTÜ 1976 graduate.
Earthquake is a natural event that affects many countries in the world. There is no escape from it. It is impossible to predict when exactly an earthquake will occur. An earthquake happens. It leaves a lot of things behind. Some of the buildings remain intact, some get damaged, some collapse. Under the collapsed buildings, people, animals, trees, goods, vehicles, valuables, etc. remain. The most important thing for the survivors is the "memories and sadness" left amongst the ruins.
In earthquake countries like us, there is an obligation to learn to live with earthquakes. In order to be prepared for an earthquake, it is necessary that the "Structures Be Strong" first. Ensuring this happens is the job of Civil Engineering. Civil Engineering Schools teach how to design buildings that will survive the quake. While teaching how to make calculations; Information in many branches such as materials, strength, reinforced concrete, steel, building statics, railways, roads, water structures, the force of water, and rivers, which are interconnected, are also taught.
Acting on structures are vertical and horizontal loads. Vertical Loads; It creates weights such as the own weights of the structures, human weights (moving loads), goods and material weights, snow-ice weights, and fixed machine weights. Horizontal Loads are; It creates loads such as earthquake, wind, explosion, vibration-generating machines. The calculations of the structures are made by superimposing these two loads, vertical and horizontal loads, according to the Bearing Power Method of the sections.
The vertical loads and calculation methods to be used in the calculations of the structures built in Turkey are determined by some standards and regulations. The TS 498 standard for vertical and live loads and snow loads, the TS 500 standard for the Design and Construction Rules of Reinforced Concrete Structures, and the Earthquake Code rules last issued in 2018 for Horizontal Loads are taken as basis.
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What are the calculations and how are they made?
Civil Engineers first need an architectural project in order to start engineering computations. According to the architectural projects prepared by the architects, if the building is to be a reinforced concrete structure, first the Formwork Plan and Column Layout Plan are prepared. Civil Engineers and Architects decide where the reinforced concrete elements such as columns, beams and curtains should be built on the project, and the “Structural System” of the building is created. The carrier system should be configured as simple and symmetrical and the carriers at the level should be uninterrupted. Civil Engineers prepare the Static Analysis of the structure whose carrier system is being designed. A Static Analysis is prepared according to the vertical loads affecting the structure first and then the horizontal loads, and the Section Effects affecting the carrier elements of the structure are calculated. The Concrete (C30, C40, C50 etc.) and Steel (Ç I, ÇIII, plain or ribbed) types to be used are decided, and the Structural Elements are dimensioned and equipped according to the rules specified in the TS 500 and Earthquake Specifications, according to the Cross-Section Effects in the static solution. According to these calculations, “Reinforcement Plans-Sections-Quantities” of Load-bearing Structural Elements such as Slab, Beam, Column, Wall, and Foundation to be applied in the field are drawn. Here the accounts are finished, the application is about to start.
With the license to be obtained from the municipality, the construction of the building begins with the Static-Reinforced Concrete Projects. The details in the prepared projects should be applied exactly in the field. No one can make an application other than the details in the prepared project.
It should not be expected that the buildings built in accordance with the Reinforced Concrete Projects, which have the right solution and prepared in accordance with the regulations, will emerge without any damage from the earthquake. Because the Earthquake Regulation has been prepared according to the principles of the structures being able to stand with little damage after an earthquake.
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Causes of Structures Collapsing in an Earthquake
There are many reasons including the following:
1. There are currently 127 Civil Engineering Schools in Turkey. According to the legislation in Turkey, a Civil Engineer graduating from the school has the authority to sign any project immediately. A freshly Graduate Civil Engineer is deemed competent enough to make static and reinforced concrete calculations of all kinds of structures. In many other countries, there is the concept of Competent (Expert) Engineering. For example, having worked in a design office for 10 years and making similar designs during this period is required, and they can become a Competent (Specialist) Engineer. In some countries they also need to pass an exam after clocking in the requisite years. Lacking such stringent requirements in Turkey, incorrect calculations prepared by people who have not made calculations before or who have made a small number of calculations may cause the buildings collapse.
2. The soil on which the buildings will be constructed must be well-investigated. Excavation, seismic, GPR, etc. examinations should be made as required until all the features can be determined correctly and the necessary values are known for the calculation. If wrong foundation systems are built on the wrong ground, there is a strong risk of collapse of the buildings even with minor earthquakes.
3. There is no statutory requirement for project computations being officially audited. Even such requirement existed, the auditors would have to be at least as knowledgeable, experienced and competent people/organizations as those who created the calculations. Previously, the calculations were approved by the Chamber of Civil Engineers. Then the approval task was transferred to the municipal authorities. Municipal approval was given relatively easily with the idea that “responsibility rests entirely with those who make the calculations”. Therefore, the accuracy of the calculations and the responsibility and accountability remain very important criteria that are not necessarily satisfied in the current system.
4. After 2000, it was obligatory for construction to be carried out under the supervision of Building Inspection firms. The control and approval of the inspection companies were expected at every project step. Due to lack of other checks and balances, this control activity degenerated to a paper pushing exercise. It is known that there are many audit companies that sign approval for what is done in the field without even seeing it. This leads to the conclusion that many buildings are not built in accordance with their projects.
5. The formworks of the structures should be supported by a sufficient number of uprights and installed without deflection. The presence of deflected slabs, beams, columns that have fallen out of their plumb line, and wall element molds that change direction can cause additional loads to occur on the structures that are not foreseen in the calculations, which may cause the sections to exceed their bearing capacity and cause the structures to collapse in an earthquake.
6. In our country, there are infamous construction company owners who boast that "everyone was doing it back then, we sold sea sand to construction companies". When this is the mentality, it does not matter that the calculations of the buildings are correct and comply with the regulations. When the application in the field is inadequate and wrong, the demolition of these structures is an inevitable result. The concrete quality of the buildings has lately increased significantly thanks to the concrete produced by the ready-mixed concrete companies. This practice started in the 1990s and mostly displaced the low-quality concrete produced by mixing with concrete mixers and mixed with sea sand (???) in the past. However, even with ready-mixed concrete, there are prqctices that are overlooked from time to time, e.g. adding water into the mixers to ensure the spreading fluidity of the concrete in the mold, reducing and weakening the strength of the concrete while ensuring the fluidity of the concrete. Even if the calculation is correct, even if the application is correct, weak concrete will cause structures to collapse.
7. Steel used in construction is a building material that is specially made and has a certain tensile strength. In construction rebars that are produced incorrectly for various reasons or bought from under-the-counter manufacturers to cut costs will cause problems. The use of rebars whose tensile strength is not fully provided in construction sites will cause inconsistency with the calculations and cause the structures to collapse.
8. When the concrete arrives and is placed in the mold, it is necessary to remove the voids in the concrete with vibrators and pour void-free concrete. If not, the concrete will be weak.
9. After the concrete is poured, the concrete must be watered and cured according to seasonal conditions in order for the concrete gain its design strength. Early molded concretes deform, crack, decrease in strength, eventually lose their carrier element properties and collapse.
10. Another very common situation is this: While the buildings are being used, some ignorant and/or fraudulent users cut and break the vertical and horizontal carrier elements (columns and beams) in order to make room for them. The vertical loads carried by the broken columns and beams are somehow balanced and transferred to the foundation, but the horizontal earthquake loads cannot be carried and the structures collapse.
11. There is another very common situation. The construction of additional floors (illegal floors) on top of buildings without making calculations and without showing their portability with calculations is also the reason for the collapse of the buildings.
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What should be done?
It is also very difficult to share responsibility in collapsed buildings due to incorrect and uncontrolled calculations, insufficient inspection of the application, insufficient construction materials such as concrete and steel. The responsibility is put on the back of the contractor. However, although everything has been done in accordance with the project, will the contractor be blamed for the destruction caused by the column and beam cutters after the client takers over the building? Is it not the fault of the column and beam cutters when a building collapses in such situations?
So what should be done?
I am of the opinion that there is no regulatory change that can be made in the short term to improve these conditions. What to do in the long run;
1. In order to increase the quality of education, at least 100 of existing 127 civil engineering schools should be closed, with quality education in fewer schools under the leadership of distinguished and valuable teachers.
2. Persons who will design should be further trained with an exam to be held at universities after at least 10 years. These people should be given a refresher training and re-examined every 5-10 years.
3. Structural computations must be audited by the Auditing Offices, which will employ experts.
4. Furthermore, the work of the Auditors must be checked by a higher Control Authority. The Control Authority experts should be more experienced and better equipped than those working in Account Offices.
5. Building Inspection Offices, which will inspect the field applications, should also be followed very seriously and should be controlled with a double-triple system.
6. In order to become a contractor, some criteria should be introduced and the number of contractors in Turkey should be reduced. (While the total number of contractors in all European countries is around 50,000, the number of contractors in Turkey is around 450,000.) The contractor must have worked in stronger contracting companies for at least 10 years, engineering-machine park-work programming-economy, in order to be able to do business on his own. Those who have filled in the university should be able to become a Freelance Contractor by succeeding in the exams to be held at universities. At the moment, any 18-year old can apply to the Ministry of Environment and get qualified as a Contractor.
7. Politicians should absolutely and definitely refrain from issuing “zoning amnesties” to forgive structural mistakes. This provision should enter the Constitution to guarantee its future enforcement.
8. Laws should be drawn up to punish those who cut and break columns and beams in buildings. These oeople should be prosecuted for the crime of "premeditated murder". The number of people who died in Chile with a magnitude of 8.8 (30-40 times of the Pazarcık Earthquake) is 520 people. This is because there are very heavy penalties for mistakes and irregularities in construction works in Chile.
Kind regards,
Necil Engür
Civil Engineer, BEng, MEng
(ITÜ-1976 graduate)