• Computational Structural Engineering
• /
• v.5 no.3
• /
• pp.119-126
• /
• 1992

Most civil engineering structures such as bridges, power plants, and offshore platforms are apt to suffer structural damages over their service lives caused by adverse loadings, such as earthquakes, wind and wave forces. Accumulation of structural damages over a long period of time might cause catastrophic structural failure. Therefore, a methodology for monitoring the structural integrity is essential for assuring the safety of the existing structures. A method for the damage assessment of structures by the second order inverse modal perturbation technique is presented in this paper. Perturbation equation consists of a matrix equation involving matrices of structural changes(stiffness and mass matrix changes) and matrices of modal property changes(natural frequency and mode shape changes). The damages of a structure are represented as changes in the stiffness matrix. In this study, a second order perturbation equation is formulated for the damage assessment of structures, and solved by an iterative procedure. The effectiveness of the proposed method has been investigated through a series of example analysis. The estimated results for the structural damage indicated that the present method yields resonable estimates for the structural changes.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.6
• /
• pp.166-172
• /
• 2016

This paper deals with the seismic qualification of the reflective metal insulation for thermal shielding that is installed on the outer surfaces of the main equipment of the primary coolant system of a nuclear power plant. A small-scale model of the reactor pressure vessel, which has equivalent dynamic characteristics, was designed to be tested in domestic seismic testing facilities in the future. In this study, seismic analysis of the small-scale model installed with metal insulation was performed using equivalent static analysis and response spectrum analysis. The required Response Spectrum for main equipment of the primary coolant system of APR-1400 plant were considered to establish the enveloping response spectrum, which was applied to the seismic analysis model. The results from two seismic analysis methods were compared to show the structural adequacy of the metal insulator design against a safe shutdown earthquake. This study will form the basis for the seismic testing to support the seismic qualification of the reflective metal insulator.

• Journal of the Korea Concrete Institute
• /
• v.26 no.3
• /
• pp.351-360
• /
• 2014

The purpose of this research is to introduce the simplified equivalent frame model for the equivalent lateral force procedure, the response spectrum procedure and nonlinear procedure according to ASCE7-10 in order to reduce the time of performance and reasonably evaluate the effect of applying the damping system with the various conditions for the analysis and the variable. In this research, the seismic performance assessment and the design of the damping system were conducted through the nonlinear time history analysis based on the performance based seismic design in ASCE7-10 in regard to applying the damping system to apartment buildings which is lately issued. The optimal design based on the 75% of seismic base shear was performed for an apartment building. The seismic performance assessment were conducted to check the safety of the building, and the economic evaluation was performed by comparing the amount of resource for the optimal designed building with the amount of resource for the original building. In addition, hysteresis dampers was applied to the apartment building, and the suggested equivalent frame model was performed using the damping system design in ASCE7-10, then its control effects were proved in the full scale model of the apartment building which was used in this research.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.13 no.5
• /
• pp.51-60
• /
• 2009

To secure the structural safety of structures and members against earthquakes, the plastic deformation capacity demand of members should be accurately predicted. In the present study, a method for the evaluation of the plastic deformations of members for moment frames was developed. To facilitate the practical use of the proposed method in equivalent seismic design, the plastic deformations of members were evaluated based on the results of elastic analysis, without using nonlinear analysis. The plastic deformation demands of members were formulated as functions of story drift demand, redistributed moment and member stiffness. Story drift demand and moment redistribution were directly determined from elastic analysis. The proposed method was applied to an 8 story-2 bay moment frame, and the predicted plastic deformations were verified using nonlinear analysis. The results showed that the proposed method could be used to accurately predict the member plastic rotations with simple calculations. The proposed method can be applied both to the earthquake design of new structures and to the performance evaluation of existing structures.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.8 no.1
• /
• pp.17-27
• /
• 2004

A new earthquake design method performing iterative calculations using secant stiffness was developed. The proposed design method has the advantages of convenience and stability in numerical analysis because it uses elastic analysis. At the same time, the proposed design method can accurately estimate the strength and ductility demands on the members because it performs the analysis on the inelastic behavior of structure using iterative calculation. In the present study, the procedure of the proposed design method was established, and a computer program incorporating the proposed method was developed. Design examples using the proposed method were presented, and its advantages were presented by the comparisons with existing design methods using elastic or inelastic analysis. The proposed design method, as an integrated method of analysis and design, can address the earthquake design strategy devised by the engineer. such as ductility limit on each member, the design concept of strong column - weak beam, and etc. In addition, through iterative calculations on the structure preliminarily designed only with member sizing, the strength and ductility demands of each member can be directly calculated so as to satisfy the given design strategy. As the result. economical and safe design can be achieved.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.4
• /
• pp.71-79
• /
• 2003

As a critical member of cable-stayed bridges, stay cables play on important role of supporting the entire structure. Traffic, wind or rain-wind induced vibrations of stay cables would be a major cause of degrading both safety and serviceability of the bridge. One of the effective alternatives to solve this problem is to employ the cable dampers. In order to design the cable damper optimally, it is necessary to exactly estimate the dynamic characteristics of the existing cables. To achieve more reliable dynamic properties of stay cables, precise excitations inducing forced vibration are needed. Therefore, in this study, a cable excitation system(exciter) controlled digitally was developed. And to evaluate the performance of the cable exciter developed, a solution of the differential equation of cable motion considering the exciter was derived, Using the cable exciter, sine sweeping and resonance tests on a cable model were carried out to obtain the dynamic characteristics effectively.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.96-96
• /
• 2022

가상현실 (Virtual Reality, VR) 기술은 3차원 가상공간 내에서의 높은 몰입감에 기반한 체험을 바탕으로 다양한 분야에서 활용되고 있다. 소방훈련이나 태풍, 지진 등 재해 대응훈련과 같이 인명피해의 위험이 있는 재해에 대한 VR 기술을 활용한 방재교육은 위험성을 동반하지 않으면서도 현장감에 기반한 높은 교육적 효과를 창출할 수 있다. 한국전자통신연구원에서는 VR 기술을 이용하여 소방훈련을 위한 실감 소방훈련 시뮬레이터를 개발한 바 있으며 목동재난체험관에서는 홍수, 태풍, 지진 등 다양한 재해에 대한 안전교육을 위한 자연재해 가상현실체험을 운영하고 있다. 이외에도 전국 지자체 및 교육청에서는 방재교육을 목적으로 VR 기술을 활용하고 있다. 그러나 기존의 VR을 활용한 수재해 방재교육은 범람의 수리학적 특성과 함께 수해지의 지형적 특성을 적절히 반영하지 못하는 단점을 가지고 있다. 이는 방재교육이나 경각심을 부각하는 데엔 효과적이나 실질적인 방재 가이드라인을 제시하는 데엔 한계가 있다. 본 연구는 몰입형 파랑해석모형인 Celeris Base를 기반으로 3차원 가상현실 시각화를 활용한 수리학적 홍수추적 모형을 개발하였다. 3차원 가상현실 시각화는 Unity3D를 이용하여 모의환경 내에 구현되었다. 강우-유출 과정의 수리학적 해석을 위해 동수역학 수치모형의 연속방정식 내에 강우와 침투에 대한 항을 추가하였다. 침투모형으로는 Horton 모형, Green-Ampt 모형과 함께 사면의 기울기를 고려한 Green-Ampt 모형을 적용하였다. 실제 유역에서의 홍수추적 모의결과는 관측값과 비교적 잘 일치함을 확인하였다. 개발된 모형은 VR 방재교육을 통해 일반인의 수재해 대응능력 향상에 기여함과 동시에 정확성 높은 홍수추적 모의결과에 기반한 홍수대책 마련에도 활용 가능할 것으로 기대된다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.3
• /
• pp.207-214
• /
• 2017

High voltage electric power transmitter GIS(Gas Insulated Switchgear) above 72.5kV needs to satisfy domestic Korean peninsular standard(ES-6110-0002) in KEPCO with respect to normal and special operation conditions which include internal gas pressure, dead weight, wind and seismic load. Some other requirements not described in Korean standard can be applied from other international standards such as IEC(International Electronical Committee) 62271-203 and 62271-207. The GIS is a kind of pressure vessel structure made of aluminum and filled with SF6 gas of internal pressure 0.4~0.5MPa. Finite element analysis of GIS is performed with such operational loads including seismic loading and the stability and reliability is determined according to ASME BPVC(Boiler and Pressure Vessel Code) SEC. VIII standard where the allowable stress level of the pressure vessel is suggested. The result shows that the stress of GIS is satisfied the allowable stress level and the safety factor is about 2.3 for Korean peninsular standard.

• Computational Structural Engineering
• /
• v.10 no.2
• /
• pp.203-211
• /
• 1997

In the design of tall building system, the wind loading can be more dominant factor than earthquake loading, and thus, it is important to check the stability and human comfort against wind. Experimental wind tunnel test is usually performed to predict wind behavior of a tall building, however, the test is not cost-effective in the preliminary stage for various structural models of tall building systems. In this regard, the study is focused on the numerical wind analysis of the tall building with and without tuned mass dampers based on the three dimensional model of wind loads and building behavior. As a numerical result, an asymmetrical 102-story tall building is presented to show the results of root mean squares of build responses with and without tuned mass dampers.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.292-292
• /
• 2020

방조제는 국토 확장, 수자원 확보 및 배수 개선에 사용되는 구조물로, 재난 발생 시 자산, 국가산업 및 환경에 큰 영향을 끼칠 위험이 있다. 따라서, 파도월류, 지진, 투수, 액상화와 같은 다양한 피해 원인에 대비하여 구조적 사용성과 안정성을 확보하기 위해 신중한 검토 및 분석이 수행된다. 그러나 변화하는 환경조건에서 방조제는 다양한 외력의 변동성과 불확실성에 노출되며, 설계 시 고려된 손상 요인이 개별적으로 발생하기보다는 여러 요인이 복합적으로 반응하고 그 영향이 전달되어 피해의 발생과 전파 과정이 복잡한 양상을 나타낸다. 따라서 방조제에 대한 사고 예방 및 안정적인 유지관리를 위해서는 발생 가능한 위험을 종합적으로 고려한 위험도 평가가 중요하게 요구된다. 본 연구에서는 방조제 손상 원인 중 큰 비중을 차지하는 제체 내부 침식 위험에 대하여 위험인자 간 상호작용을 고려할 수 있는 확률통계학적 접근으로 Bayesian network 기법을 도입하였다. 위험인자에 대한 파괴 메커니즘을 조사하여 분류 후, 설계값과 측정자료를 기반으로 위험변수의 통계적 특성을 반영하기 위해 Monte Carlo 시뮬레이션을 수행하여 파괴 매커니즘의 위험도를 계산하였다. 위험도는 연간기대피해액으로 제공되었으며, 이는 방조제 손상으로 인한 피해에 대비하여 예방할 수 있는 솔루션을 제공할 것으로 기대된다.