Many piping systems installed in the power plant are directly related to the safety and operation of the plant. Various dampers have been applied to the piping system to reduce the damage caused by earthquakes. In order to reduce the vibration of the piping system, this study developed a steel coil damper (SCD) with a straightforward structure but excellent damping performance. SCD reduces the vibration of the objective structure by hysteretic damping. The new SCD damper can be applied to high-temperature environments since it consists of steel members. The paper introduces a design method for the elastoplastic coil spring, which is the critical element of SCD. The practical applicability of the design procedure was validated by comparing the nonlinear force-displacement curves calculated by design equations with the results obtained from nonlinear finite element analysis and repeated loading test. It was found that the designed SCD’s have a damping ratio higher than 25%. In addition, this study performed a set of seismic tests using a shaking table with an existing piping system to verify the vibration control capacity on the piping system by SCD. Test results prove that the SCD can effectively control the displacement vibration of the piping system up to 80%.

In this study, the seismic safety of nuclear power plant structures is evaluated and verified by performing a vibration test on a relatively simple shear wall structure. The shear walls are the prominent members of nuclear power plants and resist the seismic load. The shear wall structure is designed and manufactured to perform shaking table tests and is used to increase the accuracy of the analytical method by comparing them with the numerical analysis results. Different results will be checked and more efficient application methods will be studied depending on the method of designing reinforced concrete structures.

Earthquake preparedness has become more important with recent increase in the number of earthquakes in Korea, but many existing structures are not prepared for earthquakes. There are various types of liquefaction prevention method that can be applied, such as compaction, replacement, dewatering, and inhibition of shear strain. However, most of the liquefaction prevention methods are applied before construction, and it is important to find optimal methods that can be applied to existing structures and that have few effects on the environment, such as noise, vibration, and changes in underground water level. The purpose of this study is to estimate the correlation between the displacement of a structure and variations of pore water pressure on the ground in accordance with the depth of the sheet file when liquidation occurs. To achieve this, a shaking table test was performed for Joo-Mun-Jin standard sand and an earth pressure, accelerometer, pore water pressure transducer, and LVDT were installed in both the non-liquefiable layer and the liquefiable layer to measure the subsidence and excess pore water pressure in accordance with the time of each embedded depth. Then the results were analyzed. A comparison of the pore water pressure in accordance with Hsp/Hsl was shown to prevent lateral water flow at 1, 0.85 and confirmed that the pore water pressure increased. In addition, the relationship between Hsp/Hsl and subsidence was expressed as a trend line to calculate the expected settlement rate formula for the embedded depth ratio.

A conventional lumped-mass stick model is based on the tributary area method to determine the masses lumped at each node and used in earthquake engineering due to its simplicity in the modeling of structures. However the natural frequencies of the conventional model are normally not identical to those of the actual structure. To solve this problem, recently an updated lumped-mass stick model is developed to provide the natural frequencies identical to actual structure. The present study is to investigate the seismic response accuracy of the updated lumped-mass stick model, comparing with the response results of the shaking table test. For the test, a small size four-story steel frame structure is prepared and tested on shaking table applying five earthquake ground motions. From the comparison with shaking table test results, the updated model shows an average error of 3.65% in the peak displacement response and 9.68% in the peak acceleration response. On the other hand, the conventional model shows an average error of 5.15% and 27.41% for each response.

In the current research, a seismic ceiling system as one of non-structural elements in buildings has been developed by applying newly designed vertical hanger clips combined with M-bar channel clips. In order to evaluate the seismic performance of the developed system, full-scale shaking table tests of one story frame structure with the conventional ceiling system or the developed seismic ceiling system were performed with time-history responses under earthquake loads. The developed system was also evaluated by the time-history dynamic analysis. From seismic test and analysis, it was shown that the developed seismic ceiling system could give improved seismic performances to minimize displacements and damages of ceiling systems as well as enhance seismic safety of the ceiling system.

진동대를 통한 백색잡음 가진 실험과 모드별 고유진동수의 Sine wave 가진 후 자유진동 실험을 통해 다자유도 구조물의 영상기반 동특성 추정을 수행하고자 하였다. 실제 현장에 적용하기에 앞서, 15 케이스의 모형 구조물을 통한 동특성 식별을 통해 영상 기반 계측 시스템의 적용성을 검증하였다. 캠코더를 통한 계측 및 동특성 추정 결과는 LDS(Laser Displacement Sensor) 및 가속도계 를 통한 결과와 비교하여 유효성을 판단하고자 하였다. 시간 및 진동수 영역에서의 동적계측 결과, 모든 센서를 통한 계측 결과가 높은 유사성을 나타냈다. 또한 캠코더 계측 데이터를 활용한 동특성 추정 결과는 LDS 및 가속도계 계측 데이터를 통한 추정 결과와 전 체적으로 유사하게 나타나므로, 영상기반 계측을 통한 구조물 동특성 추정은 유효성이 있다고 판단된다.

Liquid storage tank is one of the major infrastructures and generally used to store gases, drinking and utilizing water, dangerous fluids, fire water and so on. According to the recent reports and experiences, the tank structures are damaged in many earthquakes due to their low energy dissipating capacity. Therefore, many researchers have been tried to know the dynamic properties of the tanks including liquids. However, vary limited experimental studies are carried out using relatively small tank models. In this study, a series of shaking table tests are performed with maximum 2 m cubic rectangular liquid storage tanks made of steel to measure the natural frequency and estimate damping coefficient of impulsive and convective mode of the tanks. Especially, the damping values under different shapes and excitation methods are estimated by logarithmic decrement method and half power band-pass method and compared with current design code and standards such as ASCE 7, Eurocode 8 and NZS. Test results show that the impulsive mode damping is around 2% which is proposed by general standards and codes but the impulsive mode damping is 0.13% average that is slightly lower than the code recommendation.

Large spatial structures can not easily predict the dynamic behavior due to the lack of construction and design practices. The spatial structures are generally analyzed through the numerical simulation and experimental test in order to investigate the seismic response of large spatial structures. In the case of analysis for seismic response of large spatial structure, the many studies by the numerical analysis was carried out, researches by the shaking table test are very rare. In this study, a shaking table test of a small-scale arch structure was conducted and the dynamic characteristics of arch structure are analyzed. And the dynamic characteristics of arch structures are investigated according to the various column cross-section and length. It is found that the natural vibration periods of the small-scaled arch structure that have large column stiffness are very similar to the natural vibration period of the non-column arch structure. And in case of arch structure with large column stiffness, primary natural frequency period by numerical analysis is very similar to the primary natural frequency period of by shaking table test. These are because the dynamic characteristics of the roof structure are affected by the column stiffness of the spatial structure.

A series of tests was conducted for full-scale single-pylon asymmetric cable-stayed bridges using a system of multiple shaking tables. The 2-span bridge length was 28 m, and the pylon height was 10.2 m. 4 different base conditions were considered: the fixed condition, RB (rubber bearings), LRB (lead rubber bearings), and HDRB (high damping rubber bearings). Based on investigation of the seismic response, the accelerations and displacements in the axial direction of the isolated bridge were increased compared to non-isolated case. However, the strain of the pylon was decreased, because the major mode of the structure was changed to translation for the axial direction due to the dynamic mass. The response of the cable bridge could differ from the desired response according to the locations and characteristics of the seismic isolator. Therefore, caution is required in the design and prediction in regard to the location and behavior of the seismic isolator.

본 논문은 지진에 의한 구조물의 거동을 평가하기 위한 실험방법 중 최근 국내에 도입되어 연구되고 있는 하이브리드실험에 대한 시스템을 구축하고, 그에 따른 모델개발과 하이브리드실험을 실시하여 하이브리드실험기법의 타당성과 정확도를 평가하기 위함이다. 이를 위해 NEESgrid의 미니모스트 시스템을 벤치마킹하여 여건에 맞게 수정, 보완하였으며 2차원 평면뼈대모형을 개발하여 실험에 적용하였다. 그리고 하이브리드실험 결과의 평가를 위해 국내에서는 거의 시도되지 않았던 진동대실험과 비교를 함으로써 결과의 신뢰도를 높였다. 진동대실험에는 하이브리드실험과 동일한 크기의 실물모형을 제작, 실험하여 크기효과의 영향을 최소화하였다. 두 실험의 결과는 거의 비슷한 것으로 나타나 하이브리드실험이 진동대실험을 대체할 수 있을 것으로 판단된다.

본 연구에서는 지진시 앵커기초의 파괴한계성능을 평가하기 위하여 진동대 실험을 수행하였다. 앵커기초에 발생 가능한 열화현상인 균열의 영향을 평가하기 위하여 균열이 없는 시편, 관통균열 시편 그리고 파괴예상면 내에 측면균열이 있는 시편을 제작하여 각각의 파괴한계성능을 평가하였다. 우선적으로 임팩트 해머에 의한 가진 실험을 통하여 동특성분석실험을 수행하여 실험모형의 동특성을 분석하였으며, 앵커기초의 파괴 시까지 진동대 실험을 수행하여 극한거동을 평가하였다. 최종적으로 앵커기초의 설계기준과 비교하여 거동특성을 분석하였다.

합성 교각의 설계에서 요구 내진성능을 만족하기 위한 철근상세 규정이 명확하지 않은 측면이 있다. 합성 교각은 단면치수를 감소시키고 지진하중하에서 기둥의 연성을 개선하기 위해 제안되었다. 이 논문에서는 400mm 직경을 가진 단일 강재를 콘크리트에 매입한 합성기둥 부재를 5기 제작하여 합성기둥의 내진성능을 연구하였다. 진동대 실험과 유사동적 실험이 수행되었는데 근단층지반운동을 고려한 축소모형의 구조적 거동이 평가되었다. 실험 변수는 횡철근의 간격, 주철근의 겹침이음, 매입 강재 단면으로 설정하였다. 진동대 실험에 의해 평가된 변위연성도가 유사동적 실험에 비해 적게 나타났고 한정연성설계, 주철근의 겹침 이음 50%를 가진 부재가 기준 부재에 비해서 낮은 연성도를 보였다. 강재비는 극한강도에 영향을 미치고 겹침이음과 횡철근 비의 감소는 변위능력을 감소시켰다. 합성 교각의 상세에 따른 에너지 소산능력의 차이는 뚜렷하게 나타나지 않았다.

본 연구에서는 원전내 주요 안전관련 기기중 비상디젤발전기를 대상으로 한 진동대 실험을수행하였다. 원전의 비상디젤 발전기는 원전 전체의 노심손상빈도에 미치는 영향이 매우 크며 또한 면진장치를 설치하여 지진력을 저감시킬 경우 큰 폭으로 노심손상빈도를 감소시킬 수 있으며, 가동중 발생하는 소음과 진동으로 인하여 주변 구조물과 기기에 영향을 미치기도 한다. 따라서 지진력 저감과 기계 진동의 저감효과를 동시에 고려하기 위한 면진장치를 적용하여 그 효과를 평가하여 보고자하였다. 면진장치로는 코일스프링과 점성 댐퍼가 결합된 형태의 면진장치를 선정하였다. 실험의 대상으로 하는 비상디젤발전기는 영광 5,6호기에 설치되어 있는 모델로서 축소모형을 제작하였으며, 제작된 모형에 적합한 코일스프링-점성댐퍼 시스템을 설계하여 제작하였다. 제작된 면진장치를 축소모형에 설치하여 설계지진을 이용한 진동대 시험을 수행하여 지진력 저감효과를 분석하였다 본 연구를 통하여 설계지진의 경우 20% 그리고 Scenario 지진의 경우 70% 까지의 지진력 저감이 가능한 것을 확인하였으며, 면진장치의 기계적 특성이 설계값과 일치하지 않음으로 인하여 실제 지진력 저감효과가 크게 변할 수 있음을 확인할 수 있었다.

본 연구에서는 건물모델만을 물리적인 실험체로 이용하여 동적 지반강성을 갖는 지반-구조물계의 동적거동을 모사하기 위한 하이브리드 진동대 실험법을 제안하고 이를 실험적으로 검증하였다. 본 연구에서 제안되는 실험방법은 상부구조물과 진동대의 가속도를 계측하여 진동대 제어기로 피드백하고, 전체 지반-구조물계의 동적거동을 묘사하기 위해 요구되는 기초부분의 절대가속도 응답(가속도 피드백 방법) 또는 절대속도 응답(속도 피드백 방법)을 계산하여 진동대를 구동시키는 방법이다. 지반부분을 계산하기 위해서 이론적인 동적지반강성을 제안방법에 따라서 다르게 근사화하여 진동대 제어기에 반영함으로써 실험을 수행하였다. 기초 고정계 모델에 대한 실험으로부터 계측된 응답과 본 논문에서 가정한 지반-구조물 계에 대한 실험으로부터 측정된 응답을 비교하고, 진동대 제어기에 반영한 동적지반강성과 실험데이터를 이용하여 식별된 동적지반강성을 비교함으로써 본 논문에서 제안된 실험방법의 유효성을 검증하였다.

The behavior of the Tuned Liquid Damper (TLD) which has been widely used for mitigating structural vibration is generally modeled by linear wave theory and its vibration control performance is evaluated using Tuned Mass Damper (TMD) analogy. However, some previous studies showed that the properties of the TLD such as natural frequency and damping ratio were dependent on the excitation amplitude. In this study, the dynamic nonlinear characteristics of the TLD are investigated by shaking table test with varying excitation amplitude. In case of harmonic excitation experimentation, the damping ratio, natural frequency, and effective mass are obtained through envelope curves overlap of time-history curve from measured base shear and analogy base shear using simulation a freedom of simple degree modeling. In the white noise experimentation, the parameters obtained through curve-fitting of the transfer function from the table acceleration to the base shear.

In this study, in order to investigate the effectiveness of tuned liquid damper (TLD) for the seismic performance enhancement of the existing reinforced concrete (RC) apartment structure which is not seismically designed, shaking table test was conducted for the small scale five story RC structure with TLD. TLD model was constructed to have the frequency tuned to the first modal frequency of the structure, 2% mass ratio of the first modal mass, and 0.08 liquid depth ratio. White noise with 0.2~5Hz frequency bandwidth and harmonic load tests were performed using the shaking table at Korea Institute of Machinery and Materials, and the displacement and absolute acceleration of each floor were measured. Test results indicate that more than 30% seismic responses reduction can be achieved using TLD for RC structure under white noise and harmonic load.

본 논문에서는 상부구조물과 진동대에서 측정된 가속도를 이용하여 구조물과 지반의 동적 상호작용을 고려한 진동대 시험을 수행하는 방법이 제안된다. 부분구조법을 기반으로 한 제안된 실험법은 상부구조물만을 실험체로 사용하고 지반모델에 대해서는 동적지반강성을 진동대 제어기에 반영하는 방법이다. 이 때, 실험부분인 상부구조물은 전체 구조물 지반계의 동적거동을 모사하기 위한 운동으로 진동대에 의해 가진된다. 먼저, 구조물 지반계의 운동방정식으로부터 유도된 수치 시뮬레이션 검증모델에 의해 제안된 방법의 타당성이 검증된다. 또한, 진동대의 전달함수를 고려한 시뮬레이션 모델로부터 진동대 시험에 의한 제안된 방법의 적용성이 수치 시뮬레이션에 의해 검증된다.

This paper proposes substructuring method using experimental model of only upper MDOF structure and verifies its applicability to shaking table test. The structure considered in the test is a five-stoty shear type building model which is divided into two parts, of which one is lower three floors for a numerical substructure and the other is upper two floors for a experinlental substructure. The experimental substructure is excited by the shaking table and the acceleration data for the input of shaking table is obtained numerically from lower numerical part. For implementation of the proposed substructuring method, a controller of the shaking table is designed reflecting experimental model. In comparison with acceleration responses, which are measured from experinlental part of 3rd, 4th, and 5th floor and are numerically calculated from the original five-stoty structure, it is observed that the experimental results match well with the numerical results in both time and frequency domain.