• 한국해안·해양공학회논문집
• /
• 제25권6호
• /
• pp.412-421
• /
• 2013

최근 서해안 등지에서 중소규모 지진이 빈번하게 발생하고 있다. 이러한 지진에 의한 항만 구조물의 손상 및 파괴는 국가 경제에 큰 피해를 유발할 수 있다. 따라서 이러한 지진에 대비하기 위한 내진 설계 및 지진 경보시스템 개발이 필요한 실정이다. 본 연구에서는 항만 지진 피해 예측 시스템에 입력치 제공을 위한 부산 및 인천항의 안벽 구조물의 지진 취약도 해석을 수행하였다. 해석 대상은 부산 및 인천항의 잔교식, Caisson식, 부벽식, 블록식 안벽을 각각 4가지 Case를 해석하였으며 기능수행수준 및 붕괴방지수준에 대하여 변위기반 지진취약도 해석을 수행하였고 해석결과를 다른 항만의 안벽에도 적용할 수 있도록 회귀분석하였다.

• Computers and Concrete
• /
• 제20권4호
• /
• pp.369-380
• /
• 2017

The effects of the vertical component of a ground motion on the earthquake performances of semi-ductile high-rise R/C structures were investigated in the present study. Linear and non-linear time-history analyses were conducted on an existing in-service R/C building for the loading scenarios including and excluding the vertical component of the ground motion. The ratio of the vertical peak acceleration to the horizontal peak acceleration (V/H) of the ground motion was adopted as the main parameter of the study. Three different near-source earthquake records with varying V/H ratio were used in the analyses. The linear time-history analyses indicated that the incorporation of the vertical component of a ground motion into analyses greatly influences the vertical deflections of a structure and the overturning moments at its base. The lateral deflections, the angles of rotation and the base shear forces were influenced to a lesser extent. Considering the key indicators of vertical deflection and overturning moments determined from the linear time-history analysis, the non-linear analyses revealed that the changes in the forces and deformations of the structure with the inclusion of the vertical ground motion are resisted by the shear-walls. The performances and damage states of the beams were not affected by the vertical ground motion. The vertical ground motion component of earthquakes is markedly concluded to be considered for design and damage estimation of the vertical load-bearing elements of the shear-walls and columns.

• Earthquakes and Structures
• /
• 제12권4호
• /
• pp.437-448
• /
• 2017

Soft or extreme soft storeys in multi-storied buildings cause localized damage (and even collapse) during strong earthquake shaking. The presence of such soft or extremely soft storey is identified through provisions of vertical stiffness irregularity in seismic design codes. Identification of the irregularity in a building requires estimation of lateral translational stiffness of each storey. Estimation of lateral translational stiffness can be an arduous task. A simple procedure is presented to estimate storey stiffness using only properties of fundamental lateral translational mode of oscillation (namely natural period and associated mode shape), which are readily available to designers at the end of analysis stage. In addition, simplified analytical expressions are provided towards identifying stiffness irregularity. Results of linear elastic time-history analyses indicate that the proposed procedure captures the irregularity in storey stiffness in both low- and mid-rise buildings.

• Earthquakes and Structures
• /
• 제24권2호
• /
• pp.97-109
• /
• 2023

This experimental study investigates the effectiveness of applying carbon fiber reinforced polymer (CFRP) jackets for the retrofit of short reinforced concrete (RC) columns with inadequate transverse reinforcement and stirrup spacing to longitudinal rebar diameter equal to 12. RC columns scaled at 1/3, with round and square section, were subjected to axial compression up to failure. A damage scale is introduced for the assessment of the damage severity, which focusses on the extent of buckling of the longitudinal rebars. The damaged specimens were subsequently repaired with unidirectional CFRP jackets without any treatment of the buckled reinforcing bars and were finally re-tested to failure. Test results indicate that CFRP jackets may be effectively applied to rehabilitate RC columns (a) with inadequate transverse reinforcement constructed according to older practices so as to meet modern code requirements, and (b) with moderately buckled bars without the need of previously repairing the reinforcement bars, an application technique which may considerably facilitate the retrofit of earthquake damaged RC columns. Factors for the estimation of the reduced mechanical properties of the repaired specimens compared to the respective values for intact CFRP-jacketed specimens, in relation to the level of damage prior to retrofit, are proposed both for the compressive strength and the average modulus of elasticity. It was determined that the compressive strength of the retrofitted CFRP-jacketed columns is reduced by 90% to 65%, while the average modulus of elasticity is lower by 60% to 25% in respect to similar undamaged columns jacketed with the same layers of CFRP.

• Steel and Composite Structures
• /
• 제49권4호
• /
• pp.407-417
• /
• 2023

After a disaster like the catastrophic earthquake, the government have to use rapid assessment of the condition (or damage) of bridges, buildings and other infrastructures is mandatory for rapid feedbacks, rescue and post-event management. Many domain schemes based on the measured vibration computations, including least squares estimation and neural fuzzy logic control, have been studied and found to be effective for online/offline monitoring of structural damage. Traditional strategies require all external stimulus data (input data) which have been measured available, but this may not be the generalized for all structures. In this article, a new method with unknown inputs (excitations) is provided to identify structural matrix such as stiffness, mass, damping and other nonlinear parts, unknown disturbances for example. An analytical solution is thus constructed and presented because the solution in the existing literature has not been available. The goals of this paper are towards access to adequate, safe and affordable housing and basic services, promotion of inclusive and sustainable urbanization and participation, implementation of sustainable and disaster-resilient buildings, sustainable human settlement planning and manage. Simulation results of linear and nonlinear structures show that the proposed method is able to identify structural parameters and their changes due to damage and unknown excitations. Therefore, the goal is believed to achieved in the near future by the ongoing development of AI and control theory.

• 지구물리와물리탐사
• /
• 제13권3호
• /
• pp.268-276
• /
• 2010

지진재해대책법이 2009년 3월에 발효됨에 따라 가속도 지진관측을 수행하여야 할 기관이 대폭 확대되었다. 소방방재청의 추정에 의하면 최소 400개소의 자유장 가속도 관측소가 설치될 예정이다. 지진계측기의 성능 향상과 통신 기술의 발달로 지진관측소 설치가 보편화되면서 지진관측의 주 기능이 신속 피해 예측과 경보 발령 등 지진방재에 적극적으로 활용할 수 있도록 전환되고 있다. 신속 지진피해 예측의 기반기술인 실시간 지진동 영상화기법을 소개하였다. 이 기술은 신속한 지진피해 평가를 위한 실시간 자료 취합뿐 아니라 시각적으로 정보를 파악할 수 있도록 개발되어 활용되고 있다. 한편 지진피해는 주로 S 파와 연속되는 표면파에 의해 발생한다. 최초로 도달하는 P 파로부터 최대 지반운동 크기와 지진 피해를 예측하여 경보를 발령하는 것이 지진조기경보체계이다. 지진조기경보의 기술개발 현황과 함께 2007년 오대산지진에 적용한 예를 소개하였다. 조기경보 기술은 기상청의 지진통보 체계를 획기적으로 개선시킬 수 있다. 또한 지역별로 분산된 주요 국가 시설물의 지진방재를 위해 활용할 수 있는 분산형 조기경보 시스템의 구성과 활용방안을 제안하였다.

• 한국산학기술학회논문지
• /
• 제18권2호
• /
• pp.14-22
• /
• 2017

전 세계적으로 지구온난화에 의한 이상기후현상으로 자연재해의 발생빈도와 규모가 증가하고 있는 추세이다. 태풍, 지진, 홍수, 폭우, 가뭄, 폭염, 풍랑, 쓰나미 등과 같은 다양한 자연재해는 현재까지 인간생활에 피해를 주고 있다. 특히, 일본의 대지진, 미국의 허리케인 카트리나, 한국의 태풍 매미 등 세계적으로 자연재해에 의한 피해는 막대하다. 현 단계에서 자연 재해로 인한 피해규모를 정확히 예측하고, 그에 대처하는 것은어려운 실정이다. 그러나 재해대응 차원에서 피해 규모를 예측 할 수 있다면 신속하게 대응하여 피해를 저감할 수 있다고 판단된다. 따라서, 본 연구에서는 여러 가지 자연재해 중 해풍과 파랑에 의해 발생하는 풍랑에 관한 피해예측함수를 개발하였다. 서해 연안지역을 대상으로 국민안전처에서 발간하는 재해연 보('91~'14)의 풍랑 및 태풍피해 이력을 수집하였으며, 물가상승률을 반영하기 위해 2014년 기준으로 피해액을 환산하였다. 또한, 풍랑 및 태풍피해가 발생했을 때 기상청 및 국립해양조사원 홈페이지에서 파고, 풍속, 조위, 파향, 파주기 등의 자료를 수집하였다. 최종적으로, 연안의 지역특성을 반영하여 서해안의 9개 지역의 풍랑 피해예측함수를 개발하였다.

• Smart Structures and Systems
• /
• 제3권3호
• /
• pp.245-261
• /
• 2007

Nonlinear time-domain system identification (SI) algorithm is proposed to assess damage in a shear building by synchronously estimating time-varying stiffness and damping parameters using measured acceleration data. Mass properties have been assumed as the a priori known information. Viscous damping was utilized for the current research. To chase possible nonlinear dynamic behavior under severe vibration, an incremental governing equation of vibrational motion has been utilized. Stiffness and damping parameters are estimated at each time step by minimizing the response error between measured and computed acceleration increments at the measured degrees-of-freedom. To solve a nonlinear constrained optimization problem for optimal structural parameters, sensitivities of acceleration increment were formulated with respect to stiffness and damping parameters, respectively. Incremental state vectors of vibrational motion were computed numerically by Newmark-${\beta}$ method. No model is pre-defined in the proposed algorithm for recovering the nonlinear response. A time-window scheme together with Monte Carlo iterations was utilized to estimate parameters with noise polluted sparse measured acceleration. A moving average scheme was applied to estimate the time-varying trend of structural parameters in all the examples. To examine the proposed SI algorithm, simulation studies were carried out intensively with sample shear buildings under earthquake excitations. In addition, the algorithm was applied to assess damage with laboratory test data obtained from free vibration on a three-story shear building model.

• Earthquakes and Structures
• /
• 제13권3호
• /
• pp.323-335
• /
• 2017

A simplified framework for the probabilistic estimation of economic losses induced by the structural vulnerability in single-story and single-bay precast industrial buildings is presented. The simplifications introduced in the framework are oriented to the definition of an expeditious procedure adoptable by government agencies and insurance companies for preliminary risk assessment. The economic losses are evaluated considering seismic hazard, structural response, damage resulting from the structural vulnerability and only structural-vulnerability-induced e]conomic losses, i.e., structural repair or reconstruction costs (stock and flow costs) and content losses induced by structural collapse. The uncertainties associated with each step are accounted for via Monte Carlo simulations. The estimation results in a probabilistic description of the seismic risk of portal-like industrial buildings, expressed in terms of economic losses for each occurrence (i.e., seismic event) that owners (i.e., insured) and stakeholders can use to make risk management decisions. The outcome may also be useful for the definition of the insurance premiums and the evaluation of the risks and costs for the owner corresponding to the insurance industrial costs. A prototype of a precast concrete industrial building located in Mirandola, Italy, hit by the 2012 Emilia earthquake, is used as an example of the application of the procedure.

• 한국지진공학회논문집
• /
• 제14권5호
• /
• pp.53-64
• /
• 2010

구조물의 지진취약도 곡선은 지진의 다양한 강도를 최대지반가속도 등의 함수로 하여 몇 가지로 구분된 손상상태를 초과할 확률을 나타내는 것으로 구조물의 내진성능과 지진위험도를 평가하는데 유용하게 활용된다. 기존의 많은 연구자들이 수행한 지진취약도 곡선에 대한 연구에서 근거리 및 원거리 지진하중의 특성에 대하여 고려하지 못하였다. 본 연구에서는 근거리 및 원거리 지진으로 구분되는 지진가속도 기록을 사용하여 국내 교량의 대표적인 형식의 하나인 PSC상자형교에 대한 지진취약도 곡선을 평가하였으며 근거리와 원거리로 구분된 지진 특성이 지진취약도 곡선에 미치는 영향을 분석하였다. 예제교량의 지진취약도 곡선에 대한 근거리 및 원거리 지진의 영향이 현저한 차이를 나타내므로 지진취약도 해석시 근거리와 원거리로 구분되는 지진의 특성을 반영하여야 할 것이다.