• Earthquakes and Structures
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• 제21권6호
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• pp.601-612
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• 2021

The paper concerns the selection of a design accelerograms used for the slope stability assessment under earthquake excitation. The aim is to experimentally verify the Arias Intensity as an indicator of the excitation threat to the slope stability. A simple dynamic system consisting of a rigid block on a rigid inclined plane subjected to horizontal excitation is adopted as a slope model. Strong ground motions recorded during earthquakes are reproduced on a shaking table. The permanent displacement of the block serves as a slope stability indicator. Original research stand allows us to analyse not only the relative displacement but also the acceleration time history of the block. The experiments demonstrate that the Arias Intensity of the accelerogram is a good indicator of excitation threat to the stability of the slope. The numerical analyses conducted using the experimentally verified extended Newmark's method indicate that both the Arias Intensity and the peak velocity of the excitation are good indicators of the impact of dynamic excitation on the dam's stability. The selection can be refined using complementary information, which is the dominant frequency and duration of the strong motion phase of the excitation, respectively.

• 한국지반환경공학회 논문집
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• 제24권7호
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• pp.5-14
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• 2023

최근 국내·외에서 지진이 자주 발생하고 있다. 이러한 지진은 다양한 형태의 자연적 피해와 물리적 피해의 원인이 된다. 특히, 지반이 액체와 같은 거동을 보이는 액상화는 구조물에 큰 피해를 발생시킨다. 이에 다양한 액상화 피해 저감 공법들이 연구 및 개발되고 있다. 이에 본 연구에서는 시트파일 공법을 이용하여 기존 구조물에 적용 가능한 지진 시 액상화 피해 저감 공법에 대해 연구하였다. 1-G 진동대 실험을 수행하였고 주문진 표준사로 지반을 조성하였다. 상사 법칙을 적용하여 2층 규모의 모형 구조물을 제작하였고, 입력파는 가속도 수준 0.6g와 주파수 10Hz의 정현파를 적용하였다. 다양한 근입비에 따른 구조물 피해 저감 효과를 분석하였다. 연구 결과, 시트파일 공법을 적용하여 지반을 보강하였을 때의 구조물 침하가 지반 보강을 하지 않았을 때보다 약 71% 정도 감소하였으며, 최소 침하량을 보인 근입비는 "1"이었다. 그리고 근입비가 증가할수록 시트파일로 인해 지반 내 간극수압의 소산이 지연되는 경향을 보였다. 이러한 결과를 바탕으로 근입비에 따른 구조물 침하와의 관계를 그래프와 관계식으로 제안하였다. 본 연구 결과는 향후 기존 구조물에 적용 가능한 시트파일 공법을 개발하는데 있어 기초자료로 사용될 수 있을 것으로 기대된다.

• 한국버섯학회지
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• 제19권2호
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• pp.109-113
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• 2021

현재 양송이 종균은 1980년대 개발된 방법으로 제조되고 있어, 양송이 종균 품질 향상을 위한 새로운 제조 방법을 개발하였다. 그 결과 균사체량이 5.92±0.52 g/L로 가장 많이 배양된 CDB(compost dextrose broth) 배지에서 24℃에서 120 rpm으로 진탕 배양(24시간/일) 하는 통기식(2.5 L/min) 액체배양법으로 배양기간 10일이 액체 접종원 사용으로 양호했으며, 양송이 밀 배지 종균 생산은 밀 배지 50 g당 액체 접종원 1ml을 적정 접종량으로 하여 10일 배양하면 종균의 뭉침과 흔드는 작업없이 적절하게 배양되었음을 보고한다.

• 한국공간구조학회논문집
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• 제19권1호
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• pp.117-126
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• 2019

Micro-Electro-Mechanical Systems (MEMS) sensors have been widely used in Structural Health Monitoring due to their convenience and lower costs in comparison to conventional sensors. Triggered measurements are relevant in events such as earthquakes because unlike continuous measurements, they only record the structural response once an event happens. This is more cost effective and it makes the data more manageable because only the required measurements from the event are recorded. The most common method of triggering is amplitude triggering. However, lower input amplitudes (less than 0.1g) cannot be triggered by using this method. In this paper, sound triggering was introduced to allow triggered measurements for lower input amplitude values. The performance of the sound triggering and amplitude triggering were compared by a series of shaking-table tests. It was seen that sound-triggering method has a wider frequency (0.5~10Hz) and amplitude (0.01~1.0g) range of measurements. In addition, the sound triggering method performs better than the amplitude triggering method at lower amplitudes. The performance of the amplitude triggering, in terms of the triggering being simultaneous improves at higher input amplitudes.

• Structural Engineering and Mechanics
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• 제90권6호
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• pp.577-590
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• 2024

Considering the Column-Supported Group Silos (CSGSs) often arranged by rows in practical applications, earthquake responses will be affected by group effect. Since group effect presenting uncertainties, establishing the analytic model and evaluating characteristics of CSGSs seems necessary. This study aimed at providing a simplified method to evaluate seismic performances of the CSGSs. Firstly, the CSGSs with different storage granule heights are used as numerical examples to derive the base shear formula for three-particle dynamic analytical model. Then, the base shear distribution coefficient is defined as the group effect index. The simplified calculation method of the group silos based on the distribution coefficients is proposed. Finally, based on the empty, half, and full granular storage conditions, the empirical design parameters for the group silos system are given by combining finite element simulation with shaking table test. The group effect of storage granule heights of group silos on its frequency and base shear are studied by comparative analysis between group silos and independent single silo. The results show that the frequency of CSGSs decreases with the increasing weight of the stored granule. The connection between the column top and silo bottom plate is vulnerable, and structural measures should be strengthened to improve its damage resistance. In case of different storage granule heights, distribution coefficients are effective to reconstruction the group effect. The complex calculations of seismic response for CSGSs can be avoided by adopting the empirical distribution coefficients obtained in this study. The proposed method provides a theoretical reference for evaluation on the seismic performances of the CSGSs.

• 한국지진공학회논문집
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• 제22권4호
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• pp.253-259
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• 2018

Structure behaviors resulting from an earthquake are experimentally simulated mainly through a shaking table test. As for large-scale structures, however, size effects over a miniature may make it difficult to assess actual behaviors properly. To address this problem, research on the hybrid simulation is being conducted actively. This method is to implement numerical analysis on framework members that affect the general behavior of the structure dominantly through an actual scale experiment and on the rest parts by applying the substructuring technique. However, existing studies on hybrid simulation focus mainly on Slow experimental methods, which are disadvantageous in that it is unable to assess behaviors close to the actual level if material properties change depending on the speed or the influence of inertial force is significant. The present study aims to establish a Real-time hybrid simulation system capable of excitation based on the actual time history and to verify its performance and applicability. The hybrid simulation system built up in this study utilizes the ATS Compensator system, CR integrator, etc. in order to make the target displacement the same with the measured displacement on the basis of MATLAB/Simulink. The target structure was a 2-span bridge and an RC pier to support it was produced as an experimental model in order for the shaking table test and Slow and Real-time hybrid simulations. Behaviors that result from the earthquake of El Centro were examined, and the results were analyzed comparatively. In comparison with the results of the shaking table test, the Real-time hybrid simulation produced more similar maximum displacement and vibration behaviors than the Slow hybrid simulation. Hence, it is thought that the Real-time hybrid simulation proposed in this study can be utilized usefully in seismic capacity assessment of structural systems such as RC pier that are highly non-linear and time-dependent.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.647-652
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• 2008

This paper focused on the application of finite element model updating technique to evaluate the structural properties of the reinforced concrete specimen using the data collected from shaking table tests. The specimen was subjected to six El Centro(NS, 1942) ground motion histories with different Peak Ground Acceleration(PGA) ranging from 0.06g to 0.50g. For model updating, flexural stiffness values of structural members(walls and slabs) were chosen as the updating parameters so that the converged results have direct physical interpretations. Initial values for finite element model were determined from the member dimensions and material properties. Frequency response functions(i.e. transfer functions), natural frequencies and mode shapes were obtained using the acceleration measurement at each floor and given ground acceleration history. The weighting factors were used to account for the relative confidence in different types of inputs for updating(i.e. transfer function and natural frequencies). The constraints based on upper/lower bound of parameters and sensitivity-based constraints were implemented to the updating procedure in this study using standard bounded variable least-squares(BVLS) method. The veracity of the updated finite element model was investigated by comparing the predicted and measured responses. The results indicated that the updated model replicates the dynamic behavior of the specimens reasonably well. At each stage of shaking, severity of damage that results from cracking of the reinforced concrete member was quantified from the updated parameters(i.e. flexural stiffness values).

• Earthquakes and Structures
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• 제17권6호
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• pp.635-647
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• 2019

Tests and theoretical studies for seismic responses of a transmission tower-line system under coupled horizontal and tilt (CHT) ground motion were conducted. The method of obtaining the tilt component from seismic motion was based on comparisons from the Fourier spectrum of uncorrected seismic waves. The collected data were then applied in testing and theoretical analysis. Taking an actual transmission tower-line system as the prototype, shaking table tests of the scale model of a single transmission tower and towers-line systems under horizontal, tilt, and CHT ground motions were carried out. Dynamic equations under CHT ground motion were also derived. The additional P-∆ effect caused by tilt motion was considered as an equivalent horizontal lateral force, and it was added into the equations as the excitation. Test results were compared with the theoretical analysis and indicated some useful conclusions. First, the shaking table test results are consistent with the theoretical analysis from improved dynamic equations and proved its correctness. Second, the tilt component of ground motion has great influence on the seismic response of the transmission tower-line system, and the additional P-∆effect caused by the foundation tilt, not only increases the seismic response of the transmission tower-line system, but also leads to a remarkable asymmetric displacement effect. Third, for the tower-line system, transmission lines under ground motion weaken the horizontal displacement and acceleration responses of transmission towers. This weakening effect of transmission lines to the main structure, however, will be decreased with consideration of tilt component.

• 한국소음진동공학회논문집
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• 제18권7호
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• pp.725-731
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• 2008

This paper focused on the application of finite element model updating technique to evaluate the structural properties of the reinforced concrete specimen using the data collected from shaking table tests. The specimen was subjected to six El Centre (NS, 1942) ground motion histories with different peak ground acceleration (PGA) ranging from 0.06 g to 0.50 g. For model updating, flexural stiffness values of structural members (walls and slabs) were chosen as the updating parameters so that the converged results have direct physical interpretations. Initial values for finite element model were determined from the member dimensions and material properties. Frequency response functions (i.e. transfer functions), natural frequencies and mode shapes were obtained using the acceleration measurement at each floor and given ground acceleration history. The weighting factors were used to account for the relative confidence in different types of Inputs for updating (j.e. transfer function and natural frequencies) The constraints based on upper/lower bound of parameters and sensitivity-based constraints were implemented to the updating procedure in this study using standard bounded variable least-squares(BVLS) method. The veracity of the updated finite element model was investigated by comparing the predicted and measured responses. The results indicated that the updated model replicates the dynamic behavior of the specimens reasonably well. At each stage of shaking, severity of damage that results from cracking of the reinforced concrete member was quantified from the updated parameters (i.e. flexural stiffness values).

• 한국지반환경공학회 논문집
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• 제14권2호
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• pp.43-50
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• 2013

본 연구는 진동대 모형실험기를 이용하여 동하중 재하 시 네일 두부 구속방식에 따른 쏘일네일 보강사면의 거동에 관한 실험을 실시하였다. 진동대 모형실험은 네일 두부의 구속과 비구속조건 등을 변화시키면서 장주기 특성을 지닌 Hachinohe 지진파와 단주기 특성을 지닌 Ofunato 지진파를 적용하여 실험을 실시하였다. 실험으로부터 얻어진 결과를 바탕으로 사면의 파괴유형과 지반 가속도특성, 수직변위 및 수평변위를 비교 분석하였다. 진동대 모형실험을 수행한 결과 단주기파가 장주기파 보다 사면에 미치는 영향이 큰 것으로 나타났고, 네일 두부의 구속이 동하중에 대하여 전단저항력이 크게 발휘하는 것을 알 수 있었다. 또한 쏘일 네일 두부를 구속함으로써 지진하중 작용 시 사면의 안정성이 크게 향상됨을 확인할 수 있었다.