• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.3
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• pp.1-10
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• 2010

The target performance of a current seismic design code is to achieve collapse-prevention in order to minimize casualties. Existing structures are also being retrofitted to meet this target performance. This seismic performance seems to have been achieved in recent great overseas earthquakes, but the accompanying enormous economic loss is pointed out as a new problem. A new seismic design concept over the current target performance is required to reduce economic loss, in which a target performance is determined by the damage probability in order to control the damage levels of structures. In this study, the seismic behavior of bridges having different characteristics was investigated by nonlinear seismic analyses, and fragility curves with respect to a reference damage level were derived. Based on these results, the characteristics of target ductilities satisfying a target damage probability were investigated.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.3 s.22
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• pp.37-45
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• 2006

In this study, displacement ductility capacity and plastic hinge regions of reinforced concrete multi-column bent with different transverse reinforcement ratio are investigated. The ductility increases remarkably as transverse reinforcement ratio increase and the multi-column bent loaded along transverse direction is more ductile. The plastic hinge length for special detailing requirements of transverse reinforcement is estimated. For high target ductility, plastic hinge length for confinement should be extended with increased transverse reinforcement ratio. The plastic hinge length of multi-column bent loaded along transverse direction is shorter than that along longitudinal direction, because of the different moment distribution.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.63-69
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• 2003

In this study seismic design procedure for buckling-restrained braced frame systems was proposed using hysteretic energy spectrum and accumulated ductility spectrum constructed from single degree of freedom systems. The hysteretic energy spectra and accumulated ductility spectra corresponding to target ductility ratio were constructed first. The cross-sectional area of braces required to meet a given target displacement was obtained by equating the hysteretic energy demand to the accumulated plastic energy dissipated by braces. Twenty earthquake records were utilized to construct the spectra and to verify the validity of the design procedure. According to analysis results of three- and eight-story buckling-restrained braced frame structures designed using the proposed method, the mean values for the top story displacement correspond well with the given performance target displacements. Also, the inter-story drifts turned out to be relatively uniform over the structure height, which is desirable because uniform inter-story drifts indicate uniform damage distribution. Therefore if was concluded that the proposed energy-based method could be a reliable alternative to conventional strength-based design procedure for structures with buckling-restrained braces.

• Management & Information Systems Review
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• v.32 no.3
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• pp.221-245
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• 2013

The purpose of this study is to examine the factors leading resilience and to investigate the impact of the adaptive performance. The results are as follows: First, Cognitive Flexibility, Self Concept Clarity and Learning Goal Orientation were proved as antecedents predicted to resilience. Second, Cognitive Flexibility had positive effects on all sub variables on adaptive performance and Prove Goal Orientation had positive effects on some sub variables on adaptive performance such as problem solving, cope with uncertainty, cross cultural adaptability. Self Concept Clarity had positive effects on some sub variables on adaptive performance such as problem solving, handle crisis, cross cultural adaptability. Third, Resilience mediated the relationship between Cognitive Flexibility and Adaptive Performance(problem solving, handle crisis, cross cultural adaptability). The hypotheses of the mediation effect of resilience between Goal Orientation, Self Concept Clarity and Adaptive Performance were rejected. Lastly, this study emphasized and verified the importance of resilience in process of adaptive performance. Future studies should be looked for broad variety of resilience factors.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.2
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• pp.37-47
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• 2010

In order to attain enhanced seismic performance of RC bridges, premature shear failure prior to the achievement of target ductilities of the piers should be prevented. For this purpose, a reliable shear strength evaluation is required. The shear strength of an RC column subjected to a lateral force decreases with an increase in ductility. Many empirical equations for the shear strength have been proposed by many researchers. However, there are many discrepancies in the initial shear strength in the low ductility range, and in the decrease rate according to the ductility. In this study, a new empirical equation of shear strength considering the displacement ductility effect has been proposed, in which the initial shear strength equation proposed by the authors was revised on the basis of the investigation of many other researchers' test results. The resulting improvement in accuracy is confirmed by comparison with other empirical equations.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.793-805
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• 2004

The main objective of this paper is to evaluate the ductility and strength factors that are key components of the response modification factor for special steel moment-resistant frames. The ductility factors for special steel moment-resistant frames were calculated by multiplying the ductility factor for SDOF systems and the MDOF modification factors. Ductility factors were computed for elastic and perfectly plastic SDOF systems undergoing different levels of inelastic deformation and periods when subjected to a large number of recorded earthquake ground motions. Based on the results of the regression analysis, simplified expressions were proposed to compute the ductility factors. Based on previous studies, the MDOF modification factors were also proposed to account for the MDOF systems. Strength factors for special steel moment resisting frames were estimated from the results of the nonlinear static analysis. A total of 36 sample steel frames were designed to investigate the ductility and strength factors considering design parameters such as number of stories (4, 8, and 16 stories), seismic zone factors (Z = 0.075, 0.2, and 0.4), framing system (Perimeter Frames, PF and Distributed Frames, DF), and failure mechanism (Strong-Column Weak Beam, SCWB, and Weak-Column Strong-Beam, WCSB). The effects of these design parameters on the ductility and strength factors for special steel moment-resisting frames were investigated.

• Korean Journal of Optics and Photonics
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• v.33 no.6
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• pp.295-302
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• 2022

In this paper, a wedge prism application method was studied to design a full-high-definition (FHD)-class high-resolution flexible endoscope. In the case of the conventional flexible endoscope optical system, the F number is made large or a liquid lens is applied to obtain the same imaging performance in a wide depth of field. However, there is a problem in that the diameter of the optical system increases because an additional light guide and equipment are required. To solve this problem, two wedge prisms were applied to the flexible endoscope optical system to adjust the image distance for each object distance. First, two wedge prisms were symmetrically placed on the designed endoscopic optical system. An image distance satisfying the target imaging performance according to each objective distance was derived. Next, the wedge prism decenter value for controlling the image distance was derived. By combining these two data, a wedge prism decenter value that satisfied the target imaging performance at each object distance was applied in multi configurations. As a result of the optimal design applied with the wedge prism, a target imaging performance of more than 20% of the modulation transfer function for a resolution of 178 cycles/mm was satisfied in the entire depth of field of 100 mm-7 mm.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.3
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• pp.106-114
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• 2006

This study proposed the applicability of inverse stiffness method on the seismic design for steel frame with buckling restrained braces and the design results were compared with former research's. The concept of this method is simple and efficient. Furthermore it is able to reflect the high mode's effect and control the ductility factors of each story individually. Design results using the proposed method showed that according to increase of the given target drift, the areas of brace generally decreased but partially increased in some stories of the tall structure with very large ductility. And the post yield stiffness ratio's variation had more effect on the design results in the small post yield stiffness ratio.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.23-31
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• 2018

Recently, there was an collision accident of vehicle-concrete median barrier and unfortunately, passengers were killed by exceeded capacity of concrete median. Therefore, improving the capacity of concrete median barrier is need to reduce damage. Accordingly, in this study, appropriate collision model verified by using the FE analysis program LS-Dyna and recommend a concrete median barrier section. The improvement parameters such as wire mesh diameter, steel plate, rubber pad were selected for improved capacity of the median barrier. Finally, section of concrete median barrier improved wire mesh diameter decreased volume loss, section of concrete median barrier improved rubber pad accepted impact loading and increased elastic area.

• Journal of the Society of Disaster Information
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• v.8 no.3
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• pp.234-241
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• 2012

The main objective of this research is to calibrate the performance prediction models for the growth of fatigue cracking in multi-layered asphalt concrete pavement systems. However, the calibration factors are dependent upon the prediction model, testing method, and the laboratory loading history. A detailed study on the field data has revealed that the performance of flexible pavements is affected by both the traffic loading and the environmental cycling which is related to the age of the pavements. Thus, a composite indicator was developed in this study which utilizes both the traffic and the age information with appropriate weighting factors. Using the proposed fatigue performance model the calibration factors were also estimated through the comparisons between the field performances on fatigue cracking and the laboratory-based fatigue life.