• Advances in nano research
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• 제15권6호
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• pp.495-511
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• 2023

In this research, the impact of micro-silica, nano-silica, and polypropylene fibers on the fracture energy of self-compacting concrete was thoroughly examined. Enhancing the fracture energy is very important to increase the crack propagation resistance. The study focused on evaluating the self-compacting properties of the concrete through various tests, including J-ring, V-funnel, slump flow, and T50 tests. Additionally, the mechanical properties of the concrete, such as compressive and tensile strengths, modulus of elasticity, and fracture parameters were investigated on hardened specimens after 28 days. The results demonstrated that the incorporation of micro-silica and nano-silica not only decreased the rheological aspects of self-compacting concrete but also significantly enhanced its mechanical properties, particularly the compressive strength. On the other hand, the inclusion of polypropylene fibers had a positive impact on fracture parameters, tensile strength, and flexural strength of the specimens. Utilizing the response surface method, the relationship between micro-silica, nano-silica, and fibers was established. The optimal combination for achieving the highest compressive strength was found to be 5% micro-silica, 0.75% nano-silica, and 0.1% fibers. Furthermore, for obtaining the best mixture with superior tensile strength, flexural strength, modulus of elasticity, and fracture energy, the ideal proportion was determined as 5% micro-silica, 0.75% nano-silica, and 0.15% fibers. Compared to the control mixture, the aforementioned parameters showed significant improvements of 26.3%, 30.3%, 34.3%, and 34.3%, respectively. In order to accurately model the tensile cracking of concrete, the authors used softening curves derived from an inverse algorithm proposed by them. This method allowed for a precise and detailed analysis of the concrete under tensile stress. This study explores the effects of micro-silica, nano-silica, and polypropylene fibers on self-compacting concrete and shows their influences on the fracture energy and various mechanical properties of the concrete. The results offer valuable insights for optimizing the concrete mix to achieve desired strength and performance characteristics.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 춘계학술대회 논문집
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• pp.190-195
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• 2001

In the present paper computational simulation of a concrete dam is performed to determine the effect of vertical ground motions on earthquake response of concrete dams. Cyclic and dynamic versions of the plastic-damage model proposed by Lee and Fenves are used to represent micro-crack development and crack opening/closing, which is important mechanism in nonlinear damage analysis of concrete structures subject to strong earthquake loading. The result shows that the vertical component of ground motion effects on final crack patterns and consequently, on displacement response.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.41-48
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• 1999

Small earthquake records with magnitude 2.7-4.8 recorded in Kyungsang Basin during 1995-1997 were analysed. Total of 87 records consisted of 16 events instrumented at 11 stations,. Mean dominant period at each station mean zero period acceleration of each component and the acceleration response spectra were analysed. Spectral value increases as magnitude increases and the predominant frequency band expands to low frequency zone as magnitude increases.

• 한국지진공학회논문집
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• 제22권6호
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• pp.353-360
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• 2018

This paper is to investigate the micro-behavior of the double-span beams with WUF-W seismic connection under combined axial tension and moment and to propose the rational rotational capacity of it for progressive collapse-resistant analysis and design addressing the stress and strain transfer mechanism. To this end, the behavior of the double-span beams under the column missing event is first investigated using the advanced nonlinear finite element analysis. The characteristics of fracture indices of double-span beams with WUF-W connection under combined axial tension and flexural moment are addressed and then proposed the rational rotational capacity as the basic datum for the progressive collapse-resistant design and analysis. The distribution of fracture indices related to stress and strain for the double-span beams is investigated based on a material and geometric nonlinear finite element analysis. Furthermore, the micro-behavior for earthquake and progressive collapse is explicitly different.

• 한국지구과학회지
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• 제33권5호
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• pp.408-421
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• 2012

The objective of this paper is to apply a newly developed wavelet-based semblance filtering and eigenvalue analysis to investigate the geomagnetic variations in some micro-earthquakes that had occurred in the Korean Peninsula. The wavelet-based filtering showed improved results in delineating the geomagnetic variations in relation to earthquake events from their background field. In addition, the eigenvalues analysis was also useful for the interpretation of three components geomagnetic fields during the earthquake events. The wavelet-based semblance analysis showed a prominent result for short-term geomagnetic variation related to the earthquake event, and the eigenvalue analysis was feasible to long-term geomagnetic variation. Considering the fact that the basement rock of the Korean Peninsula has a highly resistive electrical structure, it seems to be possible for small magnitude earthquakes to generate some distinguished geomagnetic variations.

• Structural Engineering and Mechanics
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• 제61권2호
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• pp.267-274
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• 2017

In this study was investigated of possibility using the recorded micro tremor data on ground level as ambient vibration input excitation data for investigation and application Operational Modal Analysis (OMA) on the bench-scale earthquake simulator (The Quanser Shake Table) for model steel structures. As known OMA methods (such as EFDD, SSI and so on) are supposed to deal with the ambient responses. For this purpose, analytical and experimental modal analysis of a model steel structure for dynamic characteristics was evaluated. 3D Finite element model of the building was evaluated for the model steel structure based on the design drawing. Ambient excitation was provided by shake table from the recorded micro tremor ambient vibration data on ground level. Enhanced Frequency Domain Decomposition is used for the output only modal identification. From this study, best correlation is found between mode shapes. Natural frequencies and analytical frequencies in average (only) 2.8% are differences.

• 한국지진공학회논문집
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• 제2권4호
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• pp.63-72
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• 1998

본 연구는 허용진동환경을 만족하기 위한 콘크리트 슬래브의 미진동해석 및 제어기법에 관한 것이다. 본 연구에서는 제시된 방법은 임의 두 점간의 전달 함수와 가속 도로부터 미지의 가진력을 산정하고 수치해석 및 구조실험의 검증을 통하여 콘크리트 슬래브의 미진동해석 및 제어를 실시하였다. 미진동제어 설계를 위한 구조물의 고유진동수는 25-30Hz 이상이 되는 것인 바람직하며 콘크리트 구조물에서의 감쇠가 3%-5%인 경우 가진력 진동성분의 1.5배 이상 되는 것이 바람직함을 밝혔다.

• Structural Engineering and Mechanics
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• 제84권1호
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• pp.85-100
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• 2022

The updated Turkish Building Earthquake Code has been significantly renovated and expanded compared to previous seismic design codes. The use of earthquake ground motion levels with different probabilities of exceedance is one of the major advances in structural mechanics with the current code. This study aims to investigate the earthquake performance of steel structure in settlements with different seismic hazards for various earthquake ground motion levels. It is focused on earthquake and structural parameters for four different ground motion levels with different probabilities of exceedance calculated according to the location of the structure by the updated Turkish Hazard Map. For this purpose, each of the seven different geographical regions of Turkey which has the same seismic zone in the previous earthquake hazard map has been considered. Earthquake parameters, horizontal design elastic spectra obtained and comparisons were made for all different ground motion levels for the seven different locations, respectively. Structural analyzes for a sample steel structure were carried out using pushover analysis by using the obtained design spectra. It has been determined that the different ground motion levels significantly affect the expected target displacements of the structure for performance criteria. It is noted that the different locations of the same earthquake zone in the previous code with the same earthquake-building parameters show significant variations due to the micro zoning properties of the updated seismic design code. In addition, the main innovations of the updated code were discussed.

• 한국지반환경공학회 논문집
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• 제12권6호
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• pp.53-60
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• 2011

본 연구의 목적은 국내 사력댐에서 계측된 미소지진 기록(댐 정상부 계측 최대가속도 0.001g 이하)을 활용하여, 사력댐의 고유주기를 신뢰성 있게 산정할 수 있는 방법을 제시하는 데 있다. 이를 위하여, 최근 국내에서 발생한 6회의 지진에 대해 7개의 사력댐에서 계측된 총 20개의 미소지진 계측기록에 대하여, 비교적 크기가 큰 지진 계측기록(댐 정상부 계측 최대가속도 0.02g)에 대해 적용되었던 댐 저부와 정상부 가속도 증폭비에 의한 산정방법과 미소지진 기록에 직접적 적용사례는 없었던 댐 저부(기초부 또는 양안 어버트)와 정상부 가속도의 응답스펙트럼비에 의한 산정방법을 이용하여 사력댐의 고유주기를 산정해 보았다. 고유주기 산정 결과로부터, 각각의 산정방법이 미소지진 계측기록을 이용하여 국내 사력댐의 고유주기를 일관성 있게 산정할 수 있는 지 여부를 검토하였다. 본 연구에서는 국내와 같이 중약진 지역에서 미소지진 계측기록을 활용하여 사력댐의 고유주기를 산정하고자 하는 경우에는, 댐 저부와 정상부 가속도의 응답스펙트럼비를 이용한 방법이 가장 합리적인 방법인 것으로 판단되었다. 이러한 방법은 각각의 지진계측 기록에 대해 일관성 있게 사력댐의 고유주기를 산정함을 확인하였다. 또한, 산정된 결과를 기존의 일본 사력댐들에서 계측된 기록을 활용하여 산정한 일본 사력댐의 고유주기 산정결과와 비교한 결과, 매우 유사한 결과를 보임을 확인하였다.

• 지구물리와물리탐사
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• 제14권4호
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• pp.267-273
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• 2011

대륙지각으로부터 해양지각으로의 지각특성 변화가 나타나는 동해연안 해저에서 발생하는 미소지진의 위치를 JHD (Joint Hypocenter Determination) 방법을 사용하여 정밀 재결정하였다. 기상청 국가지진관측망의 지진관측 능력을 충분히 활용하고 지진발생위치 결정에 사용되는 지진의 수를 충분히 확보하기 위하여 연속지진자료를 점검하여, 20 km ${\times}$ 20 km의 연구지역에서 발생하는 56개의 미소지진 자료를 확보하였다. 우선 일반적으로 사용되는 단일진원인자 결정 방법으로 지진의 발생위치를 결정하였으며, 이 결과만으로는 연구지역 해저에 존재하는 해저 구조를 밝혀내기에 충분치 않다. 그러나 JHD 방법을 적용하면, 지진의 발생위치는 공간적 군을 형성하고 지진 발생의 원인이 되는 4개의 단층을 구체적으로 표시한다. 이들 4개의 단층은 2개의 수직으로 분포하는 진원위치와 2개의 가파르게 남쪽으로 경사져서 분포하는 진원위치로 표시된다.