• Structural Engineering and Mechanics
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• 제30권5호
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• pp.535-558
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• 2008

This study evaluates seismic performance of the school buildings with the selected template designs in Turkey considering nonlinear behavior of reinforced concrete components. Six school buildings with template designs were selected to represent major percentage of school buildings in medium-size cities located in high seismic region of Turkey. Selection of template designed buildings and material properties were based on field investigation on government owned school buildings in several cities in western part of Turkey. Capacity curves of investigated buildings were determined by pushover analyses conducted in two principal directions. The inelastic dynamic characteristics were represented by equivalent single-degree-of-freedom (SDOF) systems and their seismic displacement demands were calculated under selected ground motions. Seismic performance evaluation was carried out in accordance with recently published Turkish Earthquake Code that has similarities with FEMA-356 guidelines. Reasons of building damages in past earthquakes are examined using the results of performance assessment of investigated buildings. The effects of material quality on seismic performance of school buildings were investigated. The detailed examination of capacity curves and performance evaluation identified deficiencies and possible solutions for template designs.

• 한국소음진동공학회논문집
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• 제17권1호
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• pp.88-94
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• 2007

Structures with additional frictional damping system have strong nonlinearity that the dynamic behavior is highly affected by the relative magnitude between frictional force and excitation load. In this study, normalized response spectra of the structures with non-dimensional friction force are obtained through nonlinear time history analyses of the mass-normalized single degree of freedom systems using 20 ground motion data recorded on rock site. The variation of the control performance of frictional damping system is investigated in terms of the dynamic load and the structural natural period, of which effects were not considered in the previous studies. Least square curve fitting equations are presented for describing those normalized response spectrum and optimal non-dimensional friction forces are obtained for controlling the peak displacement and absolute acceleration of the structure based on the derivative of the curve-fitted design spectrum.

• 한국지진공학회논문집
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• 제10권3호
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• pp.77-84
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• 2006

비보강 조적조는 비균일 재료로 이루어진 합성재료에 가까우므로 그 거동이 하중종류와 구조물의 손상 정도에 따라서 매우 달라지게 된다. 본 연구에서는 여러 차례의 모의 지진을 받는 구조물의 손상거동이 어떻게 전개되어 가는지 살펴보는 간단한 방법을 제시한다. 특히, 시간영역 자료를 여러 구간으로 나누어서 주파수가 어떻게 변화해 가는지 살펴보는 부분 FFT방법을 이용하였다. 또한, 주파수와 강도와의 관계식을 이용하여 단자유도계의 이선형모델도 유도하였다. 본 연구에서 제시하는 이러한 방법들을 이용하여 비보강 조적조의 비탄성 성질들을 합리적으로 구할 수 있었다.

• Smart Structures and Systems
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• 제24권4호
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• pp.491-506
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• 2019

Literature regarding concrete walls reinforced by super elastic shape memory alloy (SMA) bars is rather limited. The seismic behavior of a system concurrently including a distinct steel reinforced concrete (RC) wall, as well as another wall reinforced by super elastic SMA at the first story, and steel rebar at upper stories, would be an interesting matter. In this paper, the seismic response of such a COMBINED system is compared to a conventional system with steel RC concrete walls (STEEL-Rein.) and also to a wall system with SMA rebar at the first story and steel rebar at other stories ( SMA-Rein.). Nonlinear time history analysis at maximum considered earthquake (MCE) and design bases earthquake (DBE) levels is conducted and the main responses like maximum inter-story drift ratio and residual inter-story drift ratio are investigated. Furthermore, incremental dynamic analysis is used to accomplish probabilistic seismic studies by creating fragility curves. Results demonstrated that the SMA-Rein. system, subjected to DBE and MCE ground motions, has almost zero and 0.27% residual maximum inter-story drifts, while the values for the COMBINED system are 0.25% and 0.51%. Furthermore, fragility curves show that using SMA rebar at the base of all walls causes a larger probability of exceedance 3% inter-story drift limit state compared to the COMBINED system. Static push over analysis demonstrated that the strength of the COMBINED model is almost 0.35% larger than that of the two other models, and its general post-yielding stiffness is also approximately twice the corresponding stiffness of the two other models.

• Earthquakes and Structures
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• 제20권2호
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• pp.201-213
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• 2021

Contrast to the conventional jointed bridge design, integral abutment bridges (IABs) offer some marked advantages like reduced maintenance and enhanced service life of the structure due to elimination of joints in the deck and monolithic construction practices. However, the force transfer mechanism during seismic and thermal movements is a topic of interest owing to rigid connection between superstructure and substructure (piers and abutments). This study attempts to model an existing IAB by including the abutment backfill interaction and soil-foundation interaction effects using Winkler foundation assumption to determine its seismic response. Keeping in view the significance of abutment behavior in an IAB, the probability of damage to the abutment is evaluated using fragility function. Incremental Dynamic Analysis (IDA) approach is used in this regard, wherein, nonlinear time history analyses are conducted on the numerical model using a selected suite of ground motions with increasing intensities until damage to abutment. It is concluded from the fragility analysis results that for a MCE level earthquake in the location of integral bridge, the probability of complete damage to the abutment is minimal.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.926-939
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• 2022

The area of this study will cover the location-wise seismic response variation of an electrical cabinet in nuclear power point (NPP) based on classical reliability analysis. The location-based seismic ground motion (GM) selection is carried out with the help of probabilistic seismic hazard analysis using PSHRisktool, where the variation of reliability analysis can be understood from the relation between the reliability index and intensity measure. Two different approaches such as the first-order second moment method (FOSM) and Monte Carlo Simulation (MCS) are helped to evaluate and compare the reliability assessment of the cabinet. The cabinet is modeled with material uncertainty utilizing Steel01 as the material model and the fiber section modeling approach is considered to characterize the section's nonlinear reaction behavior. To verify the modal frequency, this study compares the FEM result with recorded data using Least-Squares Complex Exponential (LSCE) method from the impact hammer test. In spite of a few investigations, the main novelty of this study is to introduce the reader to check and compare the seismic reliability assessment variation in different seismic locations and for different earthquake levels. Alongside, the betterment can be found by comparing the result between two considered reliability estimation methods.

• Steel and Composite Structures
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• 제43권3호
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• pp.375-388
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• 2022

Nibellen structural system is a novel resilient bracing system based on the application of Bellville disks and Nitinol rods. The cyclic behavior of Nibellen assembly was obtained, and the design equations were developed based on the available literature. Seismic performance of the system was then studied analytically. Two groups of buildings with different lateral force resisting systems were designed and studied: one group with the Nibellen system, and the other with the special concentrically braced frame system. Each building group consisted of 5-, 10-, and 15-story buildings. The Design-Base-Event (DBE) and Maximum Considered Event (MCE) were considered as the seismic hazard, and a suite of seven ground motions were scaled accordingly for response history analyses. Finally, the resiliency of the buildings was studied by obtaining the functionality curve of the buildings before and after the seismic event. The construction cost of the 5-story building with Nibellen bracing system increased but the post-earthquake cost decreased significantly. The application of Nibellen system in the 10- and 15-story buildings reduced both the construction and repair costs, considerably. Resiliency of all the buildings was improved when Nibellen system was used as the lateral force resisting system.

• 한국터널지하공간학회 논문집
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• 제15권3호
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• pp.357-373
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• 2013

본 논문에서는 터널-지반 시스템의 거동을 합리적으로 해석하고 재료의 특성과 터널설계정수 평가를 위한 역해석 프로그램을 개발하였다. 이 프로그램은 유한차분법과 직접법을 조합한 역해석 기법을 이용하기 위하여 상용 프로그램인 FLAC(Fast Lagrangian Analysis of Continua)과 최적화 알고리즘을 이용하여 지하구조물의 역해석이 가능하도록 구성되었다. 역해석 알고리즘으로는 최적화 기법 중 미분계수를 구하지 않고 직접탐색이 가능한 로젠브록법(Rosenbrock Method)을 이용하였다. 이 연구를 통하여 개발된 역해석 알고리즘의 현장 적용성 검증을 위하여 4개 구간의 실제현장을 대상으로 현장 계측결과를 이용하여 역해석을 수행하였다. 역해석 과정에서 현장계측 변위에 대한 해석 대상지반의 최적함수를 파악하기 위하여 비선형 회귀분석(nonlinear regression analysis)을 실시하였다. 회귀분석은 지수함수와 분수함수를 이용하였으며, 이를 통하여 결정된 최적함수를 이용하여 계산된 총 변위를 역해석 입력 자료로 활용하였다. 이 연구결과로써 대상구조체의 실측변위를 이용한 역해석을 수행한 결과는 계측변위와 평균 4.5%의 오차율을 보였다. 따라서 이 연구에서 제안하는 역해석 기법이 터널 해석에 유용하게 적용될 수 있음을 알 수 있었다.

• 대한토목학회논문집
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• 제41권5호
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• pp.533-541
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• 2021

옹벽 구조물은 철도, 도로, 원자력 발전소, 댐, 하천 시설 등 토압 저항을 통한 사면 붕괴방지에 활용된다. 동토압 산정 및 지진시 거동에 대한 특성을 파악하기 위해 많은 연구자들은 다양한 수치해석 프로그램(FLAC, PLAXIS, ABAQUS 등)을 활용하여 동적 하중에 대한 구조물과 지반의 비선형 거동을 분석하고 있다. 또한, 구조물의 지진에 대한 안전성을 확보하기 위해 지진취약도 곡선을 산정하여 확률론적 지진안전성 평가를 수행하고 있다. 본 연구에서는 수치해석프로그램 FLAC2D를 활용하여 뒷채움토의 사면 경사도가 있는 역T형 옹벽의 지진거동 특성을 파악하고, 옹벽 벽체의 상대적인 수평변위를 고려하여 지진취약도 평가를 수행하였다. 다양한 지진하중을 고려하기 위해 암반에서 계측된 7개의 지진파를 활용하여 각 지반특성 별(S2, S4) 비선형 지반응답해석을 수행하였고, 산정된 지진파의 크기를 5가지(0.1, 0.3, 0.5, 0.7, 0.9 g의 최대지반가속도)로 조정하였다. 본 연구에 활용된 수치해석 모델은 다른 수치해석결과와 실험결과, 주동토압 산정식을 활용하여 비교 검증하였다. 옹벽 높이에 대한 상대수평변위를 손상지수로 고려하여 옹벽의 손상상태를 결정하여 지진취약도 곡선을 산정하였다. 상대적으로 깊고 토층 평균 전단파 속도가 느린 S4 지반에서 S2 지반보다 옹벽 벽체의 수평 변위에 대한 지진취약도가 크게 산정되었음을 확인하였다.

• 한국지반환경공학회 논문집
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• 제18권6호
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• pp.39-44
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• 2017

본 연구는 기 시공된 단일말뚝의 항복점 이후 수평저항력에 관한 거동을 현장시험 및 해석적기법의 결과와 비교분석하는 과정을 다루고 있다. 또한 현장시험 및 해석적 기법의 비교분석을 통하여 횡하중을 받는 말뚝 및 기초지반의 수치모델을 검증(model calibration)하였다. 검증 및 매개변수에 관한 해석을 수행하기 위해 pushover 해석기법을 적용하였고, 본 해석기법을 통해 말뚝의 횡방향 거동에 대한 수치모형과 현장시험과의 비교분석을 통한 모델 검증, 그리고 현장시험에서는 빈도가 매우 드문 횡방향 재하를 통한 말뚝의 항복점 이후 거동까지 검증된 수치모델을 통해 분석하였다.