• 국제초고층학회논문집
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• 제1권3호
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• pp.181-194
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• 2012

Chile is characterized by the largest seismicity in the world which produces strong earthquakes every $83{\pm}9years$ in the Central part of Chile, where it is located Santiago, the capital of Chile. The short interval between large earthquakes magnitude 8.5 has conditioned the Chilean seismic design practice to achieve almost operational performance level, despite the fact that the Chilean Code declares a scope of life safe performance level. Several Indexes have been widely used throughout the years in Chile to evaluate the structural characteristics of concrete buildings, with the intent to find a correlation between general structural conception and successful seismic performance. The Indexes presented are related only to global response of buildings under earthquake loads and not to the behavior or design of individual elements. A correlation between displacement demand and seismic structural damage is presented, using the index $H_o/T$ and the concrete compressive strain ${\varepsilon}_c$. Also the Chilean seismic design codes pre and post 2010 Maule earthquake are reviewed and the practice in seismic design vs Performance Based Design is presented. Performance Based Design procedures are not included in the Chilean seismic design code for buildings, nevertheless the earthquake experience has shown that the response of the Chilean buildings has been close to operational. This can be attributed to the fact that the drift of most engineered buildings designed in accordance with the Chilean practice falls below 0.5%. It is also known by experience that for frequent and even occasional earthquakes, buildings responded elastically and thus with "fully operational" performance. Taking the above into account, it can be said that, although the "basic objective" of the Chilean code is similar to the SEAOC VISION2000 criteria, the actual performance for normal buildings is closer to the "Essential/Hazardous objective".

• 한국수학교육학회지시리즈D:수학교육연구
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• 제5권1호
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• pp.59-75
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• 2001

This paper reports an investigation of problem solving activities of students at university level students. The study focused on the cognitive-metacognitive and affective activities appeared in problem solving process. The cognitive-metacognitive framework was used to analyzed and categorize the written response and free response of interviews probing the students\\` cognitive-metacognitive activities. Affective factors were assessed by administering the problem solving survey (Carlson, The emergence of students\\` problem solving behavior, 1999). This study provide an insight for the design of problem solving instruction by identifying cognitive, metacognitive and affective characteristics of the students\\` problem solving behaviors. The results report that the metacognitive factor were significantly related to problem solving performance interacting with both cognitive and affective factors.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.87-92
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• 2000

The real situation of an underground reinforced concrete(RC) structure with the surrounding soil medium subjected to seismic load is quite difficult to be simulated through an expensive work and, even if it is possible to arrange such an experiment, it will be too expensive. So development of analytical method can be applied usefully to seismic design and seismic retrofit through an analysis of seismic behavior and seismic performance evaluation. A path-dependent constitutive model for soil that can estimate the response of soil layer is indispensible for dealing with kinematic interaction of RC/soil entire system under seismic loads. And interface model which deals with the dynamic interaction of RC/soil entire system is also necessary. In this study, finite element analysis program that can consider path-dependent behavior of RC and soil, and interfacial behavior between RC and soil is developed for rational seismic analysis of RC/soil entire system. Using this program, nonlinear behavior of interface between RC and soil is analyzed, and the effect of interfacial behavior to entire system is investigated.

• 한국지진공학회논문집
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• 제8권5호통권39호
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• pp.1-14
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• 2004

본 연구는 우리나라에서 저층 주거용 건물로 널리 사용되고 있는 2층 규모의 비보강조적조 의 1/3 축소 모델에 대한 진동대 실험을 수행한 것이다. 본 연구의 주목적은 내진설계가 이루어지지 않은 조적조 건물의 내진거동을 살펴보고, 실험적 자료를 확보하는데 있다. 실험대상구조물은 횡방향으로는 대칭이지만 종방향으로는 약간 비대칭이고, 비교적 강한 다이어프램을 나타내는 콘크리트 슬래브로 되어있다. 실험체에 대한 모의 지진하중은 가속도를 점차 증가시켜가면서 종방향으로 가력하였다. 실험에서 얻은 구조물의 동적 응답자료는 진동대의 입력지진과 연관지어서 분석하였다. 더욱이 성능기초설계를 위한 성능수준을 제시하였다. 실험결과 1층에서의 전단파괴가 지배적이고 상부층은 강체거동을 보여주었다. 또한 균열 발생후에도 상당한 강도와 변형능력을 보유하고 있는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제52권6호
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• pp.1069-1084
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• 2014

The long-term performance of plates resting on viscoelastic foundations is a major concern in the analysis of soil-structure interaction. As a powerful mathematical tool, fractional calculus may address these plate-on-foundation problems. In this paper, a fractionalized Zener model is proposed to study the time-dependent behavior of a uniformly loaded rectangular thin foundation plate. By use of the viscoelastic-elastic correspondence principle and the Laplace transforms, the analytical solutions were obtained in terms of the Mittag-Leffler function. Through the analysis of a numerical example, the calculated plate deflection, bending moment and foundation reaction were compared to those from ideal elastic and standard viscoelastic models. It is found that the upper and lower bound solutions of the plate response estimated by the proposed model can be determined using the elastic model. Based on a parametric study, the impacts of model parameters on the long-term performance of a foundation plate were systematically investigated. The results show that the two spring stiffnesses govern the upper and lower bound solutions of the plate response. By varying the values of the fractional differential order and the coefficient of viscosity, the time-dependent behavior of a foundation plate can be accurately captured. The fractional differential order seems to be dependent on the mechanical properties of the ground soil. A sandy foundation will have a small fractional differential order while in order to simulate the creeping of clay foundation, a larger fractional differential order value is needed. The fractionalized Zener model is capable of accounting for the primary and secondary consolidation processes of the foundation soil and can be used to predict the plate performance over many decades of time.

• 한국지진공학회논문집
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• 제25권6호
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• pp.261-266
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• 2021

Nuclear power plants in Korea were designed and evaluated based on the NRC's Regulatory Guide 1.60, a design response spectrum for nuclear power plants. However, it can be seen that the seismic motion characteristics are different when analyzing the Gyeongju earthquake and the Pohang earthquake that has recently occurred in Korea. Compared to the design response spectrum, seismic motion characteristics in Korea have a larger spectral acceleration in the high-frequency region. Therefore, in the case of equipment with a high natural frequency installed in a nuclear power plant, seismic performance may be reduced by reflecting the characteristics of domestic seismic motions. The failure modes of the equipment are typically structural failure and functional failure, with an anchorage failure being a representative type of structural failure. In this study, comparative analyses were performed to decide whether to consider the inelastic behavior of the anchorage or not. As a result, it was confirmed that the seismic performance of the anchorages could be increased by considering the inelastic behavior of an anchorage.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.306-311
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• 1996

This paper persents the flexural behavior of high performance concrete beams having different concrete filling conditions. Three tests were conducted on full-scale beam specimens with design concrete compressive strength of 400 kg/$\textrm{cm}^2$. Different concrete filling conditions were intentionally made such that the first beam specimen was soundly cast to obtain the perfect concrete filling condition. Second beam specimen was cast in such a way that up to the longitudinal tensile reinforcement from the top, good concrete was filled while poor concrete was poured for the bottom part to simulate the poor workamanship, workability and unsatisfactory compaction. Third beam specimens was cast in such a way that up to the neutral axis of the beam section from the top, good concrete was filled while so did for the bottom part as the second beam specimen. The test results were analyzed in terms of load-displacement response, formation of crack, crack width, crack spacing and shift of neutral axis. An evaluation of the ductile response fo three different beam specimens was made in combination with the ultimate load accoding to the three different concrete filling conditions.

• Earthquakes and Structures
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• 제13권6호
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• pp.561-572
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• 2017

Seismic base isolation has been accepted as one of the most popular design procedures to protect important structures against earthquakes. However, due to lack of information and experimental data the application of base isolation is quite limited to nuclear power plant (NPP) industry. Moreover, the effects of inelastic behavior of soil beneath base-isolated NPP have raised questions to the effectiveness of isolation device. This study applies the wavelet analysis to investigate the effects of soil-structure interaction (SSI) on the seismic response of a base-isolated NPP structure. To evaluate the SSI effects, the NPP structure is modelled as a lumped mass stick model and combined with a soil model using the concept of cone models. The lead rubber bearing (LRB) base isolator is used to adopt the base isolation system. The shear wave velocity of soil is varied to reflect the real rock site conditions of structure. The comparison between seismic performance of isolated structure and non-isolated structure has drawn. The results show that the wavelet analysis proves to be an efficient tool to evaluate the SSI effects on the seismic response of base-isolated structure and the seismic performance of base-isolated NPP is not sensitive to the effects in this case.

• Computers and Concrete
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• 제23권1호
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• pp.11-23
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• 2019

Nowadays, the characterization of Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) tensile behavior still remains a challenge for researchers. For this purpose, a simplified closed-form non-linear hinge model based on the Third Point Bending Test (ThirdPBT) was developed by the authors. This model has been used as the basis of a simplified inverse analysis methodology to derive the tensile material properties from load-deflection response obtained from ThirdPBT experimental tests. In this paper, a non-linear finite element model (FEM) is presented with the objective of validate the closed-form non-linear hinge model. The state determination of the closed-form model is straightforward, which facilitates further inverse analysis methodologies to derive the tensile properties of UHPFRC. The accuracy of the closed-form non-linear hinge model is validated by a robust non-linear FEM analysis and a set of 15 Third-Point Bending tests with variable depths and a constant slenderness ratio of 4.5. The numerical validation shows excellent results in terms of load-deflection response, bending curvatures and average longitudinal strains when resorting to the discrete crack approach.

• Computers and Concrete
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• 제21권4호
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• pp.399-406
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• 2018

The present study focuses on the performance of basalt fiber reinforced concrete (BFRC) lining in tunnel situated in sandstone rock when subjected to internal blast loading. The blast analysis of the lined tunnel is carried out using the three-dimensional (3-D) nonlinear finite element (FE) method. The stress-strain response of the sandstone rock is simulated using a crushable plasticity model which can simulate the brittle behavior of rock and that of BFRC lining is analyzed using a damaged plasticity model for concrete capturing damage response. The strain rate dependent material properties of BFRC are collected from the literature and that of rock are taken from the authors' previous work using split Hopkinson pressure bar (SHPB). The constitutive model performance is validated through the FE simulation of SHPB test and the comparison of simulation results with the experimental data. Further, blast loading in the tunnel is simulated for 10 kg and 50 kg Trinitrotoluene (TNT) charge weights using the equivalent pressure-time curves obtained through hydrocode simulations. The analysis results are studied for the stress and displacement response of rock and tunnel lining. Blast performance of BFRC lining is compared with that of plain concrete (PC) and steel fiber reinforced concrete (SFRC) lining materials. It is observed that the BFRC lining exhibits almost 65% lesser displacement as compared to PC and 30% lesser displacement as compared to SFRC tunnel linings.