• Earthquakes and Structures
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• v.6 no.6
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• pp.581-609
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• 2014

Reinforced concrete (RC) structures are likely to experience damage when subjected to earthquakes. Damage index (DI) has been recognised as an advanced tool of quantitatively expressing the extent of damage in such structures. Last 30 years have seen many concepts for DI proposed in order to calibrate the observed levels of damage. The current research briefly reviews all available concepts and investigates their relative merits and limitations with a view to proposing a new concept based on residual deformation. Currently available DIs are classified into two broad categories - non-cumulative DI and cumulative DI. Non-cumulative DIs do not include the effects of cyclic loading, whilst the cumulative concepts produce more rational indication of the level of damage in case of earthquake excitations. Ideally, a DI should vary within a scale of 0 to 1 with 0 representing the state of elastic response, and 1 referring to the state of total collapse. Some of the available DIs do not satisfy these criteria. A new DI based on energy is proposed herein and its performances, both for static and for cyclic loadings, are compared with those obtained using the most widely accepted DI in literature. The proposed DI demonstrates a rational way to predict the extent of damage for a number of case studies. More research is encouraged to address some identified issues.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1389-1396
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• 2008

The recent Sichuan earthquake(2008) in China and Iwate-Miyazaki earthquake(2008) in Japan give Korea peninsula warning that it is no more safety zone against damage by earthquake events. So, rapid and appropriate countermeasures for dam operation and management against earthquake are needed. In Korea earthquake design standard(MOCT, 1997) has been revised after Kobe earthquake. Installation of seismometer and monitoring of earthquake for special class dams is requlated in dam aseismic design standard(MOCT, 2001). Accelerometer installation project for existing dams has been carrying out by K-water to establish an earthquake network for dam safety. Real-time dam earthquake monitoring network has also been developed to detect an earthquake efficiently and to warn to dam administrators as soon as possible. In this study, dam real-time earthquake monitoring system developed by K-water was introduced and applicability of real earthquake record measured by this system to dam safety management was illustrated.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.93-100
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• 2003

Seismic isolation systems can improve the seismic safety of nuclear power plants by decreasing seismic force transmitted to structures and equipment. This study evaluates the effectiveness of equipment seismic isolation systems by the comparison of core damage frequencies in non-isolated and isolated cases. It can be found that the seismic isolation systems increase seismic capacity of nuclear equipment and decrease core damage frequencies significantly. The effect of equipment isolation is more significant in the PGA range of 0.3g to 0.5g.

• Structural Engineering and Mechanics
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• v.39 no.6
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• pp.795-812
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• 2011

Estimation of damage probability of buildings under a future earthquake is an essential issue to ensure the seismic reliability. Fragility curves are useful tools for showing the probability of structural damage due to earthquakes as a function of ground motion indices. The purpose of this study is to compare the damage probability of R/C buildings with low and high level of strength and ductility through fragility analysis. Two different types of sample buildings have been considered which represent the building types mentioned above. The first one was designed according to TEC-2007 and the latter was designed according to TEC-1975. The pushover curves of sample buildings were obtained via pushover analyses. Using 60 ground motion records, nonlinear time-history analyses of equivalent single degree of freedom systems were performed using bilinear hysteretic model and peak-oriented hysteretic model with stiffness - strength deterioration for each scaled elastic spectral displacement. The damage measure is maximum inter-story drift ratio and each performance level considered in this study has an assumed limit value of damage measure. Discrete damage probabilities were calculated using statistical methods for each considered performance level and elastic spectral displacement. Consequently, continuous fragility curves have been constructed based on the lognormal distribution assumption. Furthermore, the effect of hysteresis model parameters on the damage probability is investigated.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.2
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• pp.75-83
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• 2015

The purpose of this study is to improve the previous damage evaluation model for RC members which is proposed by Igarashi[1] in 2010.The previous model was not confirmed by enough data of damage such as, residual crack length, width and area for exfoliation of concrete, etc. In addition, validation of the model is still insufficient. Therefore, experiment of a real-scale RC structure and experiment of RC columns using the high-strength concrete were conducted to gather the data of damage in RC members. The investigation has been conducted gathering the data not only additional experiments data but also existing data for modification of damage evaluation model. It has been investigated on changing damage in RC due to axial force ratio, shear reinforcement and shear span ratio. As a result, several problems were founded in the previous model, such as, hinge length($l_p$), spacing of flexural crack($S_{av,f}$), total width of flexural cracks regulated by maximum width of flexural crack($n_f$) and total width of shear cracks regulated by maximum width of shear crack($n_s$). New model is proposed and evaluated the damage properly.

• Structural Engineering and Mechanics
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• v.25 no.1
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• pp.39-52
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• 2007

This paper describes an experimental study on structural health monitoring of a 1:3-scaled one-story concrete frame subjected to seismic damage and retrofit. The structure is tested on a shaking table by exerting successively enhanced earthquake excitations until severe damage, and then retrofitted using fiber-reinforced polymers (FRP). The modal properties of the tested structure at trifling, moderate, severe damage and strengthening stages are measured by subjecting it to a small-amplitude white-noise excitation after each earthquake attack. Making use of the measured global modal frequencies and a validated finite element model of the tested structure, a neural network method is developed to quantitatively identify the stiffness reduction due to damage and the stiffness enhancement due to strengthening. The identification results are compared with 'true' damage severities that are defined and determined based on visual inspection and local impact testing. It is shown that by the use of FRP retrofit, the stiffness of the severely damaged structure can be recovered to the level as in the trifling damage stage.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.3
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• pp.49-57
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• 2010

Most previous research on the seismic response of structures with plan irregularities have focused on the relationship between the eccentricity and the amount of torsion. This approach cannot provide the direct relationship between the irregularity and the damage. Therefore, an investigation on the relationship between the eccentricities of buildings with plan irregularities and the damage index was performed. Inelastic dynamic time-history analyses were performed on one-story buildings with various eccentricities. For the damage assessment, a 3D damage index was adopted to reflect the effect of the bi-directional response and torsion. Based on the analysis results, buildings with eccentricities of 10%, 20% and 30% will suffer 3~5%, 13~18%, and 33~47% more damage than their regular counterparts, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.73-76
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• 2008

The damage of earthquakes have to achieve by probabilistic evaluation because of uncertainty of earthquake. Fragility analysis is a useful tool for predicting the probability of damage induced by the probable earthquake. This paper presents the probability of damage as a function of peak ground acceleration and estimates the probability of five damage levels for the pier of prestressed concrete (PSC) bridge subjected to given ground acceleration. At each 100 artificial earthquake motions were generated in terms of soil conditions, and nonlinear time domain analyses were performed for the damage states of the pier of PSC bridge structures. These damage states are described by displacement ductility result from seismic performance based on existing research results. Using the damage states and ground motion parameters, five fragility curves for the pier of PSC bridges with five types of dominant frequencies were constructed assuming a log-nomal distribution. It was found that there was a significant effect on the fragility curves due to the dominant frequencies.

• Journal of the Korean Institute of Educational Facilities
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• v.19 no.4
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• pp.29-38
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• 2012

Recently large scale earthquake s are occurred around the world following the damage of buildings. So the interest of preparing for earthquake seismic design and seismic performance has becoming high. School buildings are though used for educational purpose; they are also used as emergency shelter for local residents during earthquake disaster. However, the current seismic design ratio of our country (Korea) is 3.7% and if massive earthquake is occurred it follows a serious damage. In order to overcome this situation, seismic performance evaluation is carried out for existing school building and an accurate and appropriate seismic retrofit is required based on performance evaluation to upgrade the existing school buildings. In this paper, nonlinear static analysis on existing school buildings for ATC-40 and FEMA-356 are carried out using the capacity spectrum method to evaluate seismic performance and to determine the need for retrofitting. In addition, after reinforcement to verify the effect of retrofit enhance the seismic performance is applied the seismic performance evaluation is carried out to verify the effect of seismic retrofit time history analysis using nonlinear dynamic analysis is also performed and nonlinear behavior of earthquake load of seismic retrofit of structures was also investigated.

• Steel and Composite Structures
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• v.23 no.1
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• pp.53-66
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• 2017

Structures submitted to Fire-After-Earthquake loading situations, are first experiencing inelastic deformations due to the seismic action and are then submitted to the thermal loading. This means that in the case of steel framed structures, at the starting point of the fire, plastic hinges have already been formed at the ends of the beams. The basic objective of this paper is the evaluation of the rotational capacity of steel I-section beams damaged due to prior earthquake loading, at increased temperatures. The study is conducted numerically and three-dimensional models are used in order to capture accurately the nonlinear behaviour of the steel beams. Different levels of earthquake-induced damage are examined in order to study the effect of the initial state of damage to the temperature-evolution of the rotational capacity. The study starts with the reference case where the beam is undamaged and in the sequel cyclic loading patterns are taken into account, which represent earthquakes loads of increasing magnitude. Additionally, the study extends to the evaluation of the ultimate plastic rotation of the steel beams which corresponds to the point where the rotational capacity of the beam is exhausted. The aforementioned value of rotation can be used as a criterion for the determination of the fire-resistance time of the structure in case of Fire-After-Earthquake situations.