• Structural Engineering and Mechanics
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• 제64권5호
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• pp.557-566
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• 2017

Fiber reinforced polymer (FRP) sheets are the most efficient structural materials in terms of strength to weight ratio and its application in strengthening and retrofitting of a structure or structural elements are inevitable. The performance enhancement of structural elements without increasing the cross sectional area and flexible nature are the major advantages of FRP in retrofitting/strengthening work. This research article presents a detailed study on the inelastic response of conventional and retrofitted Reinforced Concrete (RC) frames using Carbon Fibre Reinforced Polymers (CFRP) and Glass Fiber Reinforced Polymers (GFRP) subjected to quasi-static loading. The hysteretic behaviour, stiffness degradation, energy dissipation and damage index are the parameters employed to analyse the efficacy of FRP strengthening of brick in-filled RC frames. Repair and retrofitting of brick infilled RC frame shows an improved load carrying and damage tolerance capacity than control frame.

• Wind and Structures
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• 제22권1호
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• pp.107-131
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• 2016

The need for a more affordable, reliable, clean and secure energy has led to explorations in non-traditional sources, particularly renewable energies. Wind is one of the cleanest energy sources that plays a significant role in augmenting sustainability. Wind turbines, as energy convertors, are usually tall and slender structures, and depending on their location (inland or offshore), they can be subject to high wind and/or strong wave loadings. These loads can cause severe vibrations with detrimental effects on energy production, structural lifecycle and initial cost. A dissipativity analysis study was carried out to know whether wind turbine towers require damping enhancement or rigidity modifications for vibration suppression. The results suggest that wind turbines are lightly damped structures and damping enhancement is a potential solution for vibration lessening. Accordingly, the paper investigates different damping enhancement techniques for vibration mitigation. The efficacy of tuned mass damper (TMD), tuned liquid column damper (TLCD), tuned sloshing damper (TSD), and viscous damper (VD) to reduce vibrations is investigated. A comparison among these devices, in terms of robustness and effectiveness, is conducted. The VD can reduce both displacement and acceleration responses of the tower, better than other types of dampers, for the same control effort, followed by TMD, TSD, and finally TLCD. Nevertheless, the use of VDs raises concerns about where they should be located in the structure, and their application may require additional design considerations.

• 한국지진공학회논문집
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• 제18권4호
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• pp.171-180
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• 2014

Since the execution of structural design by professional structural engineers is not mandatory for small-size buildings in Korea, structural design is conducted by architects or contractors resulting in concern about the seismic safety of the buildings. Therefore, the Korean Structural Engineers Association proposed dedicated structural design criteria in 2012. The criteria were developed based on a deterministic approach in which the structural members are designed only with information of story and span length of the buildings and without structural analyses. However, due to the short time devoted to their development, these criteria miss satisfactory basis and do not deal with structural walls popularly used in Korea. Accordingly, the Ministry of Land, Infrastructure and Transport launched a research on the 'development of structural performance enhancement technologies for small-size buildings against earthquakes and climate changes'.. As part of this research, this paper intends to establish direction for the preparation of deterministic structural design guidelines for seismic safety of domestic small-size reinforced concrete buildings. To that goal, a typical plan of these buildings is selected considering frames only and frames plus walls, and then design is conducted by changing the number of stories and span length. Next, the seismic performance is analyzed by nonlinear static pushover analysis. The results show that the structural design guidelines should be developed by classifying frames only and frames plus walls. The size and reinforcement of structural elements should be provided in the middle level of the current Korean Building Code and criteria for small buildings by considering story and span length for buildings with frames only, and determined by considering the shape and location of walls and the story and span length as well for buildings with frames plus walls. It is recommended that the design of walls should be conducted by reducing the amount of walls along with symmetrically located walls.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.443-450
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• 2003

System identification techniques can be used to build a baseline modal model for a flawed structure that has no modal information on its as-built state. The accuracy of a system identification proposed by Stubbs and Kim is analyzed for plate-girder bridges and its impact on the accuracy of damage detection in those structures is also analyzed. A laboratory-scale model plate-girder is experimentally tested and the initial four bending modes are examined for certain damage scenarios. The performance of individual baseline modal models is assessed by detecting damage in the model structure.

• 한국공간구조학회논문집
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• 제15권2호
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• pp.61-68
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• 2015

The performance enhancement of various structural building systems from natural hazards has become an inctreasingly important issue in engineering field. In this paper, visco-elastic(VE) CST30 damping systems were tested under cyclic loadings to evaluate their performance in terms of ductility and energy dissipation. Main test variables are relative shear stiffness, rate of loading frequency, and thickness of specimens to evaluate the seismic capacity based on the performance criteria. This experiment was performed using a total of 12 specimens, subjected to cyclic loadings up to a shear deformation of 500%. All the CST30 dampers provided a ductile and stable hysterestic behavior when subjected to the demands of large shear stiffness and different loading frequencies. The test results showed that the CST30 dampers are an effective damping systems to enhance the buildings performance for remodeling and retrofit of buildings.

• 아태비즈니스연구
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• 제12권2호
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• pp.25-37
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• 2021

Purpose - This study analyzes the situational relationship between the components of job crafting and innovation performance, and based on this, suggests practical alternatives to the effect of the control variables of organizational support. Design/methodology/approach - For this survey, 350 questionnaires were distributed to Korean SME workers from October 5, 2020 to March 20, 2021, and 230 questionnaires were collected. In order to check the validity of the questionnaire, the questionnaire judged to be inappropriate in response was excluded. The recovery rate was 65.7%, and the effectiveness of the questionnaire was 82%. Structural equation model and hierarchical regression analysis are used to analyze those data. Findings - First, job enhancement through job redesign as well as organizational support is a key task in order to expect innovative results from field members. Innovative performance is not created by individual jobs, but is created between jobs and jobs, tasks and tasks, teams and teams, and departments and departments. This is why it is worth paying attention not to the functional approach, but to the interconnection structure of the process. Research implications or Originality - In this study, it was analyzed that structural job resource increase and social job resource increase, which are components of job crafting, had a positive effect on innovation performance, and that challenging job will had no significant effect. Challenging work will itself does not negatively affect innovation performance. Combining the survey and interview, field members who make up the majority of respondents say that they do not lack the will to work. They claim that there is no channel or opportunity to express or practice a challenging will.

• Journal of Information Technology Applications and Management
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• 제29권6호
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• pp.63-80
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• 2022

In this paper, we study structural changes and performance gains in condition-based maintenance process redesign when mobile IoT technology is embedded into urban railway rolling stock. We first develop condition-based maintenance To-Be process model in accordance with the IoT deployment scheme. Secondly, we draw upon theoretical framework of redesign process analysis to develop performance evaluation method suitable to predictive maintenance shift from As-Is ordinary maintenance practice. Subsequently, To-Be process performance evaluations are conducted adopting both the quantitative and qualitative method for time, cost, and dependability dimensions. The results ascertain the considerable benefits captured through detection abnormality prior to actual rolling stock failure occurrence, and details of performance improvements and enhancement of standardization level is revealed. The procedures and results presented in this paper offers useful insights in the fields of IoT economic analysis, condition based maintenance, and business process redesign.

• 한국구조물진단유지관리공학회 논문집
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• 제11권3호
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• pp.185-191
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• 2007

본 연구에서는 주거용 무량판구조의 내진성능을 개선하기 위한 면진적용 가능성을 평가하였으며, 시간이력 해석을 위한 지진기록 사용에 대한 문제점을 제시하였다. 면진층 강성 및 주기 평가 및 포락해석법을 적용하여 면진전 비틀림 모드가 강한 구조물을 면진시스템 적용으로 내진성능을 개선하였다. 지진기록 사용 및 크기 조절효과의 적정성을 평가하기 위하여 DBE, MCE, ASCE 7-05의 1.4DBE 의해 크기를 조정한 시간이력 해석결과를 비교한 결과, 구조물의 지반조건과 유사한 조건에서 관측된 지진기록 및 지진기록의 응답이 설계규준 응답스펙트럼의 평균${\pm}$표준편차 범위 안에 있는 기록을 사용하는 것이 적절한 것으로 판단된다.

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.124-128
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• 2018

Titanium doping is employed to enhance the structural strength of a high-Ni layered cathode material in lithium ion batteries during high temperature cycling. After Ti-doping, the external morphology remains similar, but the lattice parameters of the layered structure are slightly shifted toward larger values. With application of the prepared materials as cathodes in lithium-ion batteries, the initial capacities are similar but the cycling performance at $25^{\circ}C$ is enhanced by Ti-doping. During high temperature cycling at $60^{\circ}C$, furthermore, highly improved capacity retention is achieved with the Ti-doped material (95% of initial capacity at 50th cycles), while cycle fading is accelerated with the bare electrode. This enhancement is attributed to better retention of the compressive strength of the particles and retarded crack formation within the particles. In addition, impedance increase is reduced in the Ti-doped electrode, which is attributed to an improvement in the structural strength of the high-Ni cathode material with Ti-doping.

• Earthquakes and Structures
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• 제16권5호
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• pp.523-532
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• 2019

Different types of gas reservoir such as Liquid Natural Gas (LNG) are among the strategic infrastructures, and have great importance for any government or their private owners. To keep the tank and its contents safe during earthquakes especially if the contents are of hazardous or flammable materials; using seismic protection systems such as base isolator can be considered as an effective solution. However, the major deficiency of this system can be the large deformation in the isolation level which may lead to the failure of bearing system. In this paper, as a solution, the efficacy of an optimally designed combined vibration control system, the combined laminated rubber isolator and rotational friction damper, is investigated to evaluate the enhancement of an existing metal tank response under both far- and near-field earthquakes. Responses like impulsive and convective accelerations, base shear, and sloshing height are studied herein. The probabilistic framework is used to consider the uncertainties in the structural modeling, as well as record-to-record variability. Due to the high calculation cost of probabilistic methods, a simplified structural model is used. By using the Mont-Carlo simulation approach, it is revealed that this combined isolation system is a highly reliable system which provides considerable enhancement in the performance of reservoir, not only leads to the reduction of probability of catastrophic failure of the tank but also decrease the reservoir damage during the earthquake. Moreover, the relative displacement of the isolation level is controlled very well by this combined system.