TBDY-2018'e göre tasarlanmış planda A1 ve A3 düzensizliği bulunan betonarme bir binanın performans analizi
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2022
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Özet
Deprem, tüm dünyada olduğu gibi ülkemizde de insanlığı tehdit eden bir doğa olayıdır. Gelişen teknoloji ile birlikte bu afete karşı önlemler alınmaya çalışılsa da can güvenliğini sağlamak adına depreme karşı dayanıklı yapı tasarlamak büyük önem arz etmektedir. Bu bağlamda, depreme dayanıklı bina tasarımının gerçekleştirilmesi ile ilgili belirli kuralların ve uygulama esaslarının yer aldığı deprem yönetmelikleri oluşturulmuştur. Tez çalışması kapsamında, 1 Ocak 2019 tarihi itibariyle ülkemizde yürürlüğe giren Türkiye Bina Deprem Yönetmeliği-2018 (TBDY-2018) esas alınmıştır. Bina tasarımında genel anlamda doğrusal-elastik hesaba dayalı dayanıma göre tasarım prensipleri kullanılmaktadır. Buna karşın, binaların gerçek davranışını yansıtan ve doğrusal olmayan analiz yöntemlerinin kullanıldığı şekildeğiştirmeye göre tasarım, binaların deprem yükleri altında performans seviyelerini belirlemek adına önem arz etmektedir. TBDY-2018'de deprem yer hareketi etkisi altındaki gerçek bina davranışının tahmin edilmesini gerektiren yüksek binalar, sismik izolasyonlu binalar gibi önemli binaların tasarımı ve mevcut binalarda şekildeğiştirmeye göre tasarım zorunlu kılınmıştır. Bu tür binalarda dayanıma göre tasarım bir ön tasarım yöntemi olarak benimsenmiştir. Bu kapsamda, söz konusu tez çalışmasında, TBDY-2018 esasları uyarınca dayanıma göre tasarımı yapılmış, bünyesinde A1-burulma düzensizliği ve A3-planda çıkıntı düzensizliği bulunduran, taşıyıcı sistemi boşluksuz perde ve çerçevelerden oluşan 10 katlı betonarme bir binanın performans değerlendirilmesi yapılarak şekil değiştirmeye göre tasarımı tamamlanmıştır. Tez çalışmasında, ilk olarak dayanıma göre tasarım kapsamında, binanın doğrusal-elastik davranışını esas alan üç boyutlu (3D) nümerik modeli ETABS programında oluşturulmuştur. Kolon ve kirişler çubuk eleman, perde ve döşemeler ise kabuk eleman olarak modellenmiştir. Doğrusal-elastik analizde kullanılan etkin kesit rijitlik çarpanları ilgili kesitlere atanmıştır. TS498'de belirtilen yük kabullerine göre döşeme ve kirişlere yük ataması yapılmıştır. Binanın kat kütleleri programa hesaplatılarak serbest titreşim analizi (modal analiz) gerçekleştirilmiş; binanın X, Y ve burulma doğrultularındaki hâkim titreşim periyotları, mod şekilleri ve kütle katılım oranları belirlenmiştir. TBDY-2018'de tanımlı olan elastik ivme spektrumu ve kat kütleleri ile birlikte ek dışmerkezlik etkileri de dikkate alınarak eşdeğer deprem yükü yöntemi uygulanmıştır. Dışmerkezlik etkileri ile X ve Y doğrultularındaki deprem yer hareketlerinin yönleri dikkate alınarak sekiz farklı kombinasyon oluşturulup düzensizlik, göreli kat ötelemeleri, ikinci mertebe etkileri ve devrilme momenti kontrolleri yapılmıştır. Binada A1 burulma düzensizliği ve A3 planda çıkıntı bulunması düzensizliklerinin yer aldığı tespit edilmiştir. Devrilme momenti kontrollerinin sağlanamaması üzerine yapı davranış katsayısında (R) düzeltme yapılmıştır. Burulma düzensizliği katsayısı oranında dışmerkezlik etkileri artırılmış ve eşdeğer deprem yükü yöntemi binaya tekrar uygulanmıştır. Yalnızca düşey yüklerin bulunduğu tasarım kombinasyonu ile birlikte depremin X ve Y bileşenlerinin aynı anda etkimesi durumlarını gözönüne alacak şekilde oluşturulan toplamda 65 yük kombinasyonu için en olumsuz durumu veren yükleme değerine göre kolon, kiriş ve perde elemanların boyut ve donatı miktarları belirlenmiştir. Binanın serbest titreşim modlarının kütle katılım oranlarının X, Y ve burulma doğrultularında yeterli katılımı sağlayamadığından dolayı binaya ayrıca mod birleştirme yöntemi de uygulanmıştır. Mod birleştirme yöntemi ile de yük kombinasyonları oluşturulup tasarım gerçekleştirilmiş ve dayanıma göre tasarım sonlandırılmıştır. Şekildeğiştirmeye göre tasarım kapsamında, binanın doğrusal olmayan davranışı esas alan nümerik modeli yine ETABS programıyla oluşturulmuştur. Malzeme açısından doğrusal olmama durumunu dikkate alabilmek adına kiriş ve kolonlarda yığılı plastisite; perdelerde ise yayılı plastisite kullanılmıştır. Kirişlerin uçlarına M3 eğilme mafsalı, kolonlara iki eksenli eğilme ve normal kuvvet etkileşimini dikkate alabilen P-M2-M3 mafsalı, perdelerde ise kritik perde yüksekliği boyunca bünyesinde doğrusal olmayan beton ve donatı çeliği gerilme-şekildeğiştirme bağıntılarının tanımlanabildiği kesit hücreleri atanmıştır. Kolon ve kiriş kesitlerinin moment-eğrilik ilişkilerinin oluşturulması için XTRACT programından faydalanılmıştır. Moment-eğrilik ilişkileri iki doğrulu olarak idealleştirilerek doğrusal olmayan analize esas olacak etkin kesit rijitlikleri ile göçme öncesi (GÖ) ve kontrollü hasar (KH) performans sınırları için plastik dönme değerleri hesaplanmıştır. Kolonlarda moment-eğrilik ilişkileri oluşturulurken dikkate alınacak eksenel yük doğrusal olmayan düşey yük analiziyle belirlenmiştir. Perde elemanlarında kullanılan kesit hücrelerine atanan parabolik pekleşen donatı ve Mander sargılı-sargısız beton modelleri TBDY-2018'den alınmıştır. X ve Y yönünde kütle katılım oranlarının düşük olması sebebiyle binaya sabit tek modlu itme analizi yöntemi uygulanmamış; Zaman Tanım Alanında Doğrusal Olmayan Analiz (ZTA) yöntemi uygulanmıştır. Analizde kullanılacak yatay deprem ivme kayıtları, tasarıma esas deprem yer hareketi düzeyine uygun deprem büyüklüğü, kaynak mekanizması, yerel zemin grubu ve faya olan mesafelere göre Pacific Earthquake Engineering Research Center (PEER) veritabanında bulunan gerçek deprem ivme kayıtlarından seçilmiştir. TBDY-2018'de yer alan basit ölçeklendirme yöntemi PEER veritabanı tarafından gerçekleştirilmiştir. Bu kapsamda, on bir deprem ivme kayıt takımının bileşenlerinin elastik ivme spektrum ordinatlarının karelerinin toplamının karekökü alındıktan sonra ortalamalarından oluşan spektrumdaki ivme değerlerinin, tasarıma esas elastik spektrum ivme ordinatlarının 1.3 katından büyük olması esas alınmıştır. Zaman tanım alanında doğrusal olmayan analizin başlangıç adımı olarak doğrusal olmayan düşey yük analizi tanımlanmıştır. Bu analiz sonucu oluşan deformasyon ve rijitlik durumları esas alınarak yer hareketinin her iki bileşeni aynı anda binaya belirlenen ölçek katsayısı ile çarpılarak etki ettirilmiştir. Analizlerde Rayleigh sönümü kullanılmış olup sınır periyotlar için belirli yaklaşımlar yapılmıştır. Sonuç olarak, on bir adet yer hareket çifti, doğrultuları değiştirilerek binaya etki ettirilmiş, toplamda 22 adet zaman tanım alanında doğrusal olmayan analiz yapılmıştır. Yeni yapılacak binanın deprem yer hareketi karşısında performansını belirlemek adına, ZTA'dan elde edilen istem büyüklüklerinin zaman serisi sonuçlarının en büyük değerlerinin ortalamaları dikkate alınmıştır. Bazı istem değerleri için, doğrusal olmayan analiz için hesaplanan bu değerler ile mod birleştirme yöntemi ile hesaplanan değerler karşılaştırılmıştır. Hesaplamalar sonucunda, TBDY-2018 uyarınca Dayanıma Göre Tasarımda belli oranda hasar oluşumuna izin verilmiş olsa da A1 ve A3 türü düzensizliğe rağmen kolon ve kiriş olarak çalışan elemanların yaklaşık %85' i Sınırlı Hasar Bölgesi' nde kalmıştır. Perde elemanlarda plastikleşmenin zemin kat düzeyinde sınırlı kaldığı ve şekildeğiştirmelerin bütün depremler için yönetmelik hasar sınır değerinin altında kaldığı belirlenmiştir. Mod Birleştirme yöntemi ile bulunan sonuçlar karşılaştırıldığında, tepe yerdeğiştirmelerinin doğrusal olmayan analizde her iki yönde de ortalama %70 oranında daha fazla çıktığı, göreli kat ötelemeleri değerlerinin iki yöntem için de yönetmelik sınır değerleri altında kaldığı, taban kat kesme kuvvetlerinin doğrusal olmayan analiz sonuçlarında yaklaşık 3 katı kadar fazla olduğu gözlemlenmiştir. Bütün olarak bakıldığında, TBDY-2018 esaslarına göre tasarlanan söz konusu binanın tasarım deprem yer hareketi olan DD-2 altında Kontrollü Hasar performans düzeyinde olduğu, ancak Belirgin Hasar Bölgesi' ne geçen çok az sayıda elemanın bulunması nedeniyle oldukça güvenli tarafta kalan bir performans sergilediği söylenebilir. Özellikle perdelerin sınırlı hasar performans seviyesinde kaldığı düşünüldüğünde perde tasarımında daha düşük donatı oranlarının kullanılabilmesine olanak doğmaktadır.
Earthquake is a natural event that threatens humanity in our country as well as all over the world. Although precautions are being taken against this disaster with the developing technology, it is important to design an earthquake-resistant structure to ensure life safety. In this context, earthquake regulations have been established, including specific rules and guidelines for the implementation principles of earthquake-resistant building design. Within the scope of the thesis, the Turkish Building Earthquake Code-2018 (TBEC-2018), which entered into force in our country as of January 1, 2019, was taken as a basis. In general, strength-based design principles built on linear-elastic analysis are used in building design. On the other hand, deformation-based design, which reflects the real behavior of the buildings and where nonlinear analysis methods are used, is important in order to determine the performance levels of the buildings under seismic loads. In TBEC-2018, deformation-based design has been made mandatory for important buildings such as high-rise buildings, seismic isolated buildings, which require the estimation of the actual building behavior under earthquake ground motion. In such buildings, strength-based design has been adopted as a preliminary design method. Within this scope, in the thesis study, performance evaluation of a 10-storey reinforced concrete building consisting of shear walls and frames with A1-torsion irregularity and A3-re-entrant corner irregularity designed in accordance with strength-based design principles of TBEC-2018 is done. Therefore, deformation-based design is completed. In the thesis study, first of all, within the scope of strength-based design, a three-dimensional (3D) numerical model rely on the linear-elastic behavior of the building was created in the ETABS program. Columns and beams are modeled as frame elements, shear walls and floors are modeled as shell elements. The effective section stiffness factors used in the linear-elastic analysis are assigned to the related sections. According to the load acceptance criteria specified in TS498, loads were assigned to the floors and beams. Free vibration analysis (modal analysis) of building was performed by considering the floor masses calculated by the program. The dominant vibration periods, mode shapes and mass participation ratios in the X, Y and torsional directions of the building were determined. Equivalent earthquake load method was applied, taking into account the elastic acceleration spectrum and storey masses defined in TBEC-2018, as well as additional eccentricity effects. Eight different combinations were created by taking into account the eccentricity effects and the directions of earthquake ground motions in the X and Y directions, and controls for irregularity, storey drifts, second order effects and overturning moment were made. It has been determined that there are A1 torsional irregularities and A3 re-entrant corner irregularities in the plan. Since the overturning moment controls could not be achieved, the building behavior coefficient (R) was corrected. The eccentricity effects were increased by the ratio of the torsional irregularity coefficient and the equivalent earthquake load method was applied to the building again. Considering the simultaneous effect of the X and Y components of the earthquake, the dimensions and reinforcement ratio of columns, beams and shear walls were determined according to the most unfavorable situations arising from a total of 65 load combinations including the design combination of vertical loads only. Since the mass participation ratios of the free vibration modes of the building could not provide sufficient participation in the X, Y and torsional directions, the mode superposition method was also applied to the building. The design was carried out with also by load combinations created for mode superposition method and strength-based design was finalized. Within the scope of deformation-based design, the numerical model rely on the non-linear behavior of the building was created with the ETABS program. In order to take into account the material nonlinearity, the concentrated plasticity model in beams and columns, while, distributed plasticity model was used in shear walls. M3 moment hinge are assigned to the ends of the beams, the P-M2-M3 hinge which can take into account the biaxial bending and normal force interaction was assigned to columns, and fibers in which nonlinear concrete and reinforcing steel stress-strain relations can be defined, were assigned to shear walls along the critical wall height. XTRACT program is used to create moment-curvature relations of column and beam sections. By idealizing the moment-curvature relations as bi-linear, the plastic rotation values were calculated for the effective section stiffnesses and the Collapse Prevention (CP) and Life Safety (LS) performance limits, which will be the basis for the non-linear analysis. The axial load to be considered when creating the moment-curvature relations in columns is determined by nonlinear vertical load analysis. Parabolic hardening reinforcement steel and Mander confined-unconfined concrete models assigned to the fibers used in the shear walls elements are taken from TBEC-2018. Due to the low mass participation ratios in the X and Y directions, the single-mode pushover analysis method was not applied to the building; Nonlinear Time History Analysis (NTHA) method was applied. The horizontal earthquake acceleration records to be used in the analysis corresponding to the design earthquake ground motion level were selected from the real earthquake records in the Pacific Earthquake Engineering Research Center (PEER) database, according to the earthquake magnitude, the source mechanism, local site class and the distance to the fault that. The simple scaling method in TBEC-2018 was performed by the PEER database. In this context, earthquake selection was done by the following rule: the average elastic spectrum calculated from the 11 acceleration spectrum ordinates after taking the square root of the sum of the squares of X and Y components of each earthquake pair should be greater than 1.3 times of the design basis elastic spectrum acceleration ordinates. Nonlinear vertical load analysis is defined as the initial step of nonlinear time history analysis. Based on the deformation and stiffness conditions resulting from this analysis, both components of the ground motion were simultaneously applied to the building by using pre-determined scale factor. As a result, eleven ground motion acceleration pairs were affected on the building by changing their directions, and 22 nonlinear time history analysis was performed in total. In order to determine the performance of the new building under earthquake ground motion, the averages of the largest values of the time series results of demand parameters obtained from the NTHA were taken into account. For some demand parameters, the values calculated from NTHA analysis were compared with the results obtained from the mode superposition method. As a result of the calculations, although a certain amount of damage was allowed in the strength-based design in accordance with TBEC-2018, approximately 85% of the elements working as columns and beams remained in the Limited Damage Zone despite the A1 and A3 type irregularities. It has been determined that the plasticization of the shear wall elements is limited at the ground floor level and the deformations are below the damage limit value of the regulation for all earthquakes. Compared to the results obtained by the Mode Combination Method, it was observed that the peak displacements are increased by 70% on average in both directions in the nonlinear analysis, the relative storey drift values are below the regulation limit values for both methods, and the nonlinear analysis results of the base story shear forces are approximately 3 times higher. As a whole, it can be said that the building was designed according to the TBEC-2018 guidelines, and that it was at the level of controlled damage performance under the design earthquake ground level DD-2, but it has a very safe performance due to the fact that there are very few elements in the significant damage zone. Especially considering that the shear walls remain at a limited damage performance level, it becomes possible to use lower reinforcement ratios in the design of the shear wall.
Earthquake is a natural event that threatens humanity in our country as well as all over the world. Although precautions are being taken against this disaster with the developing technology, it is important to design an earthquake-resistant structure to ensure life safety. In this context, earthquake regulations have been established, including specific rules and guidelines for the implementation principles of earthquake-resistant building design. Within the scope of the thesis, the Turkish Building Earthquake Code-2018 (TBEC-2018), which entered into force in our country as of January 1, 2019, was taken as a basis. In general, strength-based design principles built on linear-elastic analysis are used in building design. On the other hand, deformation-based design, which reflects the real behavior of the buildings and where nonlinear analysis methods are used, is important in order to determine the performance levels of the buildings under seismic loads. In TBEC-2018, deformation-based design has been made mandatory for important buildings such as high-rise buildings, seismic isolated buildings, which require the estimation of the actual building behavior under earthquake ground motion. In such buildings, strength-based design has been adopted as a preliminary design method. Within this scope, in the thesis study, performance evaluation of a 10-storey reinforced concrete building consisting of shear walls and frames with A1-torsion irregularity and A3-re-entrant corner irregularity designed in accordance with strength-based design principles of TBEC-2018 is done. Therefore, deformation-based design is completed. In the thesis study, first of all, within the scope of strength-based design, a three-dimensional (3D) numerical model rely on the linear-elastic behavior of the building was created in the ETABS program. Columns and beams are modeled as frame elements, shear walls and floors are modeled as shell elements. The effective section stiffness factors used in the linear-elastic analysis are assigned to the related sections. According to the load acceptance criteria specified in TS498, loads were assigned to the floors and beams. Free vibration analysis (modal analysis) of building was performed by considering the floor masses calculated by the program. The dominant vibration periods, mode shapes and mass participation ratios in the X, Y and torsional directions of the building were determined. Equivalent earthquake load method was applied, taking into account the elastic acceleration spectrum and storey masses defined in TBEC-2018, as well as additional eccentricity effects. Eight different combinations were created by taking into account the eccentricity effects and the directions of earthquake ground motions in the X and Y directions, and controls for irregularity, storey drifts, second order effects and overturning moment were made. It has been determined that there are A1 torsional irregularities and A3 re-entrant corner irregularities in the plan. Since the overturning moment controls could not be achieved, the building behavior coefficient (R) was corrected. The eccentricity effects were increased by the ratio of the torsional irregularity coefficient and the equivalent earthquake load method was applied to the building again. Considering the simultaneous effect of the X and Y components of the earthquake, the dimensions and reinforcement ratio of columns, beams and shear walls were determined according to the most unfavorable situations arising from a total of 65 load combinations including the design combination of vertical loads only. Since the mass participation ratios of the free vibration modes of the building could not provide sufficient participation in the X, Y and torsional directions, the mode superposition method was also applied to the building. The design was carried out with also by load combinations created for mode superposition method and strength-based design was finalized. Within the scope of deformation-based design, the numerical model rely on the non-linear behavior of the building was created with the ETABS program. In order to take into account the material nonlinearity, the concentrated plasticity model in beams and columns, while, distributed plasticity model was used in shear walls. M3 moment hinge are assigned to the ends of the beams, the P-M2-M3 hinge which can take into account the biaxial bending and normal force interaction was assigned to columns, and fibers in which nonlinear concrete and reinforcing steel stress-strain relations can be defined, were assigned to shear walls along the critical wall height. XTRACT program is used to create moment-curvature relations of column and beam sections. By idealizing the moment-curvature relations as bi-linear, the plastic rotation values were calculated for the effective section stiffnesses and the Collapse Prevention (CP) and Life Safety (LS) performance limits, which will be the basis for the non-linear analysis. The axial load to be considered when creating the moment-curvature relations in columns is determined by nonlinear vertical load analysis. Parabolic hardening reinforcement steel and Mander confined-unconfined concrete models assigned to the fibers used in the shear walls elements are taken from TBEC-2018. Due to the low mass participation ratios in the X and Y directions, the single-mode pushover analysis method was not applied to the building; Nonlinear Time History Analysis (NTHA) method was applied. The horizontal earthquake acceleration records to be used in the analysis corresponding to the design earthquake ground motion level were selected from the real earthquake records in the Pacific Earthquake Engineering Research Center (PEER) database, according to the earthquake magnitude, the source mechanism, local site class and the distance to the fault that. The simple scaling method in TBEC-2018 was performed by the PEER database. In this context, earthquake selection was done by the following rule: the average elastic spectrum calculated from the 11 acceleration spectrum ordinates after taking the square root of the sum of the squares of X and Y components of each earthquake pair should be greater than 1.3 times of the design basis elastic spectrum acceleration ordinates. Nonlinear vertical load analysis is defined as the initial step of nonlinear time history analysis. Based on the deformation and stiffness conditions resulting from this analysis, both components of the ground motion were simultaneously applied to the building by using pre-determined scale factor. As a result, eleven ground motion acceleration pairs were affected on the building by changing their directions, and 22 nonlinear time history analysis was performed in total. In order to determine the performance of the new building under earthquake ground motion, the averages of the largest values of the time series results of demand parameters obtained from the NTHA were taken into account. For some demand parameters, the values calculated from NTHA analysis were compared with the results obtained from the mode superposition method. As a result of the calculations, although a certain amount of damage was allowed in the strength-based design in accordance with TBEC-2018, approximately 85% of the elements working as columns and beams remained in the Limited Damage Zone despite the A1 and A3 type irregularities. It has been determined that the plasticization of the shear wall elements is limited at the ground floor level and the deformations are below the damage limit value of the regulation for all earthquakes. Compared to the results obtained by the Mode Combination Method, it was observed that the peak displacements are increased by 70% on average in both directions in the nonlinear analysis, the relative storey drift values are below the regulation limit values for both methods, and the nonlinear analysis results of the base story shear forces are approximately 3 times higher. As a whole, it can be said that the building was designed according to the TBEC-2018 guidelines, and that it was at the level of controlled damage performance under the design earthquake ground level DD-2, but it has a very safe performance due to the fact that there are very few elements in the significant damage zone. Especially considering that the shear walls remain at a limited damage performance level, it becomes possible to use lower reinforcement ratios in the design of the shear wall.
Açıklama
Anahtar Kelimeler
Burulma düzensizliği, Planda çıkıntı bulunması, Performans analizi, Doğrusal olmayan analiz, TBDY-2018, Torsional irregularity, Projections in plan irregularity, Performance analysis, Nonlinear analysis