DD-1 ve DD-2 deprem yer hareketi düzeyleri için betonarme binaların tasarımı, yapısal özellikler ve yapı maliyeti açısından karşılaştırılması
Design of reinforced concrete structures for DD-1 and DD-2 earthquake ground motion levels, comparison in terms of structural features and construction costs
Yazar: BEKİR ÖZBAY
Danışman: PROF. DR. TÜLAY AKSU ÖZKUL
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: İnşaat Mühendisliği = Civil Engineering

Özet:
Ülkemiz deprem kuşağında yer alan ve sık sık depreme maruz kalan bir ülkedir. TBDY-2018'de depremlerin olma sıklığına ve büyüklüklerine göre DD-1, DD-2, DD-3 ve DD-4 olmak üzere 4 adet deprem yer hareketi düzeyi tanımlanmıştır. DD-1 çok seyrek gerçekleşen en büyük deprem yer hareketi düzeyini, DD-2 seyrek deprem yer hareketi düzeyini, DD-3 sık deprem yer hareketi düzeyini ve DD-4 ise servis deprem yer hareketi düzeyini tarif etmektedir.  Türkiye Bina Deprem Yönetmeliği- 2018'de binalar tasarlanırken DD-2 deprem yer hareketi düzeyi tasarım yer hareketi düzeyi olarak kabul edilmiştir. Ancak 6 Şubat 2023 tarihinde 10 ilimizi etkileyen, ülkece yaşadığımız 2 büyük deprem felaketinde depremin spektral ivme değerlerinin DD-2 tasarım deprem yer hareketi düzeyini bir hayli aştığı, hatta DD-1 deprem yer hareketi düzeyini de aşan bölgeler olduğu görülmüştür. Bu gerekçe ile söz konusu yüksek lisans tez çalışmasında, tasarım deprem yer hareketi düzeyi DD-2 ve en büyük deprem yer hareketi düzeyi DD-1 ile çerçeveli ve perdeli-çerçeveli taşıyıcı sisteme sahip iki ayrı binanın tasarımı ve analizi ile elde edilen yapısal sonuçların ve yapı maliyetlerinin karşılaştırılması amaçlanmıştır. Tez çalışması 5 bölümden oluşmaktadır. 
Birinci bölümde çalışmanın amacı ve kapsamı açıklanmış, literatürdeki benzer çalışmalardan bahsedilmiştir.
İkinci bölümde deprem yer hareketi kavramları, deprem etkisi altında binaların değerlendirilme esasları, TBDY-2018 Dayanıma Göre Tasarım esasları açıklanmış ve taşıyıcı sistem elemanlarının tasarımındaki özel kurallara yer verilmiştir.
Üçüncü bölümde analiz edilecek çerçeve sistem tanıtılmış bina ve deprem parametreleri verilmiştir. Bu sistem mod birleştirme yöntemi kullanılarak DD-2 ve DD-1 deprem yer hareketi düzeyinde analiz edilmiştir. TBDY-2018 ışığında göreli kat ötelemeleri, ikinci mertebe etkileri, düzensizlikler vb. özellikler kontrol edilmiştir. Döşemelerin, kirişlerin, kolonların ve temelin betonarme hesapları yapılmıştır. Kirişlerin, kolonların ve birleşim bölgelerinin kesme güvenliği kontrolleri yapılmıştır. Temel için zımbalama hesabı yapılmıştır ve uygun temel kalınlığı belirlenmiştir. Ardından toplam beton ve donatı maliyetleri toplanarak yapı maliyeti hesaplanmıştır. Elde edilen bulgular DD-2 ve DD-1 deprem yer hareketi düzeyi için karşılaştırmalı olarak verilmiştir.
Dördüncü bölümde perdeli çerçeve sistem tanıtılmış, bina ve deprem parametreleri verilmiştir. Bu sistem mod birleştirme yöntemi kullanılarak DD-2 ve DD-1 deprem yer hareketi düzeyinde analiz edilmiştir Taşıyıcı sistem davranış katsayısı TBDY-2018'deki kurallara göre kontrol edilmiştir. Göreli kat ötelemesi, ikinci mertebe etkileri ve yapısal düzensizlikler kontrol edilmiştir. Kolon, kiriş, döşeme, perde ve temelin betonarme hesapları yapılmıştır. Beton ve donatı maliyetleri toplanmak suretiyle yapı maliyetleri hesaplanmıştır. Elde edilen bulgular DD-2 ve DD-1 deprem yer hareketi düzeyleri için karşılaştırmalı olarak ele alınmıştır.
Beşinci bölümde DD-2 ve DD-1 deprem yer hareketi düzeyinde çerçeveli ve perdeli çerçeve modellerin analizlerinden elde edilen sonuçlar açıklanmıştır.

Abstract:
Our country is located in a seismic zone and frequently experiences earthquakes. The 2018 Turkish Building Earthquake Code (TBDY) defines four levels of seismic ground motion, categorized based on the frequency and magnitude of earthquakes: DD-1, DD-2, DD-3, and DD-4. DD-1 represents the most severe ground motion level, which occurs very rarely; DD-2 represents a rare ground motion level; DD-3 represents a frequent ground motion level; and DD-4 represents the service ground motion level. In the code, the DD-2 ground motion level is accepted as the design ground motion level when designing buildings. However, it was observed that the spectral acceleration values from the two major earthquakes that occurred on February 6, 2023, with epicenters in Pazarcık (Kahramanmaraş) and Elbistan (Kahramanmaraş), which affected ten provinces and had magnitudes of Mw 7.7 and Mw 7.6, respectively, exceeded the design spectrum values obtained for the DD-2 design earthquake ground motion level. For this reason, the purpose of this master's thesis is to compare the structural results and construction costs obtained from the design and analysis of two separate buildings with the same structural system for DD-1 and DD-2 earthquake ground motion levels. In the analyses and calculations within the scope of the thesis, Hatay, one of the provinces most affected by the earthquake, was chosen as the location.
The study focuses on two types of structural systems: a frame structural system composed of columns, beams, and slabs, and a shear wall frame structural system with L-shaped shear walls at the corners, both with eight stories, plan dimensions of 25x15 meters, and story heights of 2.90 meters. The material used is C30 concrete class and B420C reinforcement steel. ZC soil class was selected as the ground type.
The design process began with the calculation of slab thickness, which was determined to be 14 cm. Next, the loads transferred from beams and slabs to the columns were calculated, and approximate preliminary sizing of columns and other structural elements was carried out. After determining the dimensions of the slabs, columns, and beams, slab covering loads, beam wall loads, wind loads, snow loads, and live loads according to TS-498 were established. In the models created using the CSI-ETABS v20.3 software, columns and beams were modeled as beam finite elements, while shear walls and slabs were modeled as shell finite elements. The modal superposition method was used within the scope of the thesis.
Based on the considered earthquake ground motion levels and the ZC soil class, local soil effect coefficients and design spectral acceleration coefficients were determined through the AFAD website, and with these coefficients, horizontal and vertical elastic design spectra were obtained. Subsequently, according to TBDY-2018, the Building Usage Class (BKS) was determined as BKS=3 for residential buildings, with a Building Importance Factor of I=1.0. The design spectra were transferred to the CSI-ETABS v.20.3 software for finite element analysis. In addition to the horizontal earthquake effect, the vertical earthquake effect (Ez) was also calculated. The building was analyzed using the load combinations provided in the TBDY and TS-500 regulations. Separate analyses were performed for the building with a frame structural system and the building with a shear wall frame structural system, considering DD-1 and DD-2 earthquake ground motion levels.
Regarding the analysis results, it was observed that the highest period occurred in the frame systems. The period decreased by approximately 50% with the addition of shear walls to the system. The maximum base shear force occurred in the shear wall frame system under DD-1 earthquake ground motion level. When using the equivalent earthquake load method, the base shear force under the DD-1 earthquake ground motion level increased by 2.3 times in the x-direction and 2.4 times in the y-direction in the frame system compared to DD-2. In the shear wall frame system, the increase was 2.5 times in both x and y directions. The frame system exceeded the relative story drift limit in both X and Y directions under DD-1 earthquake ground motion level. In the models within the scope of the thesis, the largest spectral displacement occurred in the x and y directions in the shear wall frame system under DD-1 earthquake ground motion level. In the frame system, spectral displacement under DD-1 earthquake ground motion level increased by 1.6 times in the x-direction and 2 times in the y-direction compared to DD-2 earthquake ground motion level. No plan irregularities were found in the frame and shear wall frame models within the scope of the thesis, but soft story irregularity (B2) was present on the first floor. In the frame and shear wall frame models within the scope of the thesis, the longitudinal reinforcement ratio in columns ranged from 1.06% to 1.2% under DD-2 and DD-1 earthquake ground motion levels. Specifically, the longitudinal reinforcement ratio was 1.19% in 45×45 columns, 1.06% in 55×55 columns, 1.08% in 65×65 columns, 1.11% in 75×75 columns, and the minimum reinforcement ratio was 1.04% in 85×85 columns. In the frame and shear wall frame models within the scope of the thesis, all columns under DD-1 and DD-2 earthquake ground motion levels did not exceed the axial load upper limit. In the frame system, columns operate at a maximum of 40% capacity under DD-2 earthquake ground motion level, while this ratio is around 83% at the DD-1 level. In the frame system with shear walls, columns operate at a maximum of 37% capacity under DD-2 earthquake ground motion level, while this ratio is approximately 45% at the DD-1 level. At the DD-2 earthquake ground motion level, 8 mm diameter stirrups were used in the beams, while it was determined that 10 mm diameter stirrups were required at the DD-1 earthquake ground motion level. In the frame system, at the DD-2 earthquake ground motion level, additional reinforcement bars with diameters of 12 mm and a small amount of 14 mm were sufficient for beams. At the DD-1 earthquake ground motion level, additional reinforcement bars with diameters of 14 mm and predominantly 16 mm were used. 

Regarding construction costs, the total cost of concrete and reinforcement in the frame system under DD-1 earthquake ground motion level increased by approximately 14.5% compared to DD-2. In the shear wall frame system, the total cost of concrete and reinforcement under DD-1 earthquake ground motion level increased by approximately 44% compared to DD-2.
When shear walls are added to the edges of the frame system, the cost increases by approximately 20% at the DD-2 earthquake ground motion level and by around 50% at the DD-1 earthquake ground motion level. Considering the effectiveness of shear walls in resisting horizontal loads and limiting displacements and second-order effects, and given that their impact on construction costs is around 20%, it is crucial to design load-bearing systems as regular frame systems with shear walls.
Shear walls should be placed in a way that does not induce torsion in the building plan. They must have buckling stability, symmetric stiffness, and sufficient safety against overturning at the base. When positioning shear walls in the plan, it is advisable to ensure that the expected plastic deformations are evenly distributed throughout the building plan.
In multi-story buildings, shear walls should be placed in both directions. For instance, American earthquake codes recommend at least four shear walls in each principal direction of the building. Based on the results obtained in this study, it is suggested that a requirement for a certain proportion of shear walls in the load-bearing system be included in TBEC-2018.