• Computers and Concrete
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• 제33권2호
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• pp.205-216
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• 2024

Self-Curing Self Compacting Concrete (SCSCC), is a special concrete in contemporary construction practice aimed at enhancing the performance of structural concrete. Its primary function is to ensure a sufficient moisture supply that facilitates hydration along with flow, particularly in the context of high-rise buildings and tall structures. This innovative concrete addresses the challenges of maintaining adequate curing conditions in large-scale projects, maintaining requisite workability, contributing to the overall durability and longevity of concrete structures. For implementing such a versatile material in construction, it is imperative to understand the stress-strain (S-S) behaviour. The primary aim of this study is to develop the S-S curves for TCSCSCC and compare through experimental results. Finite element (FE) analysis based ATENA-GiD was employed for the numerical simulation and develop the analytical stress-strain curves by introducing parameters viz., grade of concrete, tie diameter, tie spacing and yield strength. The stress ratio and the strain ratios are evaluated and compared with experimental values. The mean error is 1.2% with respect to stresses and 2.2% in case of strain. Finally, the stress block parameters for tie confined SCSCC are evaluated and equations are proposed for the same in terms of confinement index.

• Steel and Composite Structures
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• 제35권4호
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• pp.509-525
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• 2020

Steel-concrete composite slabs with profiled steel sheeting are widely used in the execution of floors in steel and composite buildings. The rapid construction process, the elimination of conventional replaceable shuttering and the reduction of temporary support are, in general, considered the main advantages of this structural system. In slabs with the spans currently used, the longitudinal shear resistance commonly provided by the embossments along the steel sheet tends to be the governing design mode. This paper presents an innovative reinforcing system that increases the longitudinal shear capacity of composite slabs. The system is constituted by a set of transversal reinforcing bars crossing longitudinal stiffeners executed along the upper flanges of the steel sheet profiles. This type of reinforcement takes advantage of the high bending resistance of the composite slabs and increases the slab's ductility. Two experimental programmes were carried out: a small-scale test programme - to study the resistance provided by the reinforcing system in detail - and a full-scale test programme to test simply supported and continuous composite slabs - to assess the efficacy of the proposed reinforcing system on the global behaviour of the slabs. Based on the results of the small-scale tests, an equation to predict the resistance provided by the proposed reinforcing system was established. The present study concludes that the resistance and the ductility of composite slabs using the reinforcing system proposed here are significantly increased.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3112-3121
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• 2021

One of the major factors affecting the life span of a Reactor Pressure Vessel (RPV) is the Pressurised Thermal Shock (PTS). PTS is a thermo-mechanical load on the RPV wall due to steep temperature gradients and structural load created by internal pressure of the fluid within the RPV. Safe operating life of a nuclear power plant is ensured by carrying out fracture analysis of the RPV against thermal shock. Carrying out fracture tests on RPV/large scale components is not always feasible. Hence, studies on laboratory level specimens are necessary to validate and supplement the prototype results. This paper aims to study the fracture behaviour of standard Compact Tension [C(T)] specimens, made of RPV steel 20MnMoNi55, subjected to thermal shock through experimental and numerical investigations. Fracture tests have been carried out on the C(T) specimens subjected to thermal transient load and tensile load to quantify the effect of thermal shock. Crack resistance curves are obtained from the fracture tests as per ASTM E1820 and compared with those obtained numerically using XFEM and a good agreement was found. A quantitative study on the crack tip plastic zone, computed using cohesive segment approach, from the numerical analyses justified the experimental crack initiation toughness.

• Computers and Concrete
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• 제23권2호
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• pp.81-95
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• 2019

The unexpected seismic interaction of dry-assembled precast concrete frame structures typical of the European heritage with their precast cladding panels brought to extensive failures of the panels during recent earthquakes due to the inadequateness of their connection systems. Following this recognition, an experimental campaign of cyclic and pseudo-dynamic tests has been performed at ELSA laboratory of the Joint Research Centre of the European Commission on a full-scale prototype of precast structure with vertical and horizontal cladding panels within the framework of the Safecladding project. The panels were connected to the frame structure by means of innovative arrangements of fastening systems including isostatic, integrated and dissipative. Many of the investigated configurations involved a strong frame-cladding interaction, modifying the structural behaviour of the frame turning it into highly non-linear since small deformation. In such cases, properly modelling the connections becomes fundamental in the framework of a design by non-linear dynamic analysis. This paper presents the peculiarities of the numerical models of precast frame structures equipped with the various cladding connection systems which have been set to predict and simulate the experimental results from pseudo-dynamic tests. The comparison allows to validate the structural models and to derive recommendations for a proper modelling of the different types of existing and innovative cladding connection systems.

• Steel and Composite Structures
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• 제49권5호
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• pp.533-546
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• 2023

Cost-effective solutions provided by composite construction are gaining popularity which, in turn, promotes the appearance on the market of new types of composite sections that allow not only to take advantage of the synergy of steel and concrete working together at room temperature, but also to improve their behaviour at high temperatures. When combined with high performance materials, significant load-bearing capacities can be achieved even with reduced cross-sectional dimensions. Steel-reinforced concrete-filled steel tubular (SR-CFST) columns are one of these innovative composite sections, where an open steel profile is embedded into a CFST section. Besides the renowned benefits of these typologies at room temperature, the fire protection offered by the surrounding concrete to the inner steel profile, gives them an enhanced fire performance which delays its loss of mechanical capacity in a fire scenario. The experimental evidence on the fire behaviour of SR-CFST columns is still scarce, particularly when combined with high performance materials. However, it is being much needed for the development of specific design provisions that consider the use of the inner steel profile in CFST columns. In this work, a new experimental program on the thermo-mechanical behaviour of SR-CFST columns is presented to extend the available experimental database. Ten SR-CFST stub columns, with circular and square geometries, combining high strength steel and concrete were tested. It was seen that the circular specimens reached higher failure times than the square columns, with the failure time increasing both when high strength steel was used at the embedded steel profile and high strength concrete was used as infill. Finally, different proposals for the reduction coefficients of high performance materials were assessed in the prediction of the cross-sectional fire resistance of the SR-CFST columns.

• Earthquakes and Structures
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• 제8권6호
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• pp.1325-1348
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• 2015

Real-time hybrid testing (RTHT) involves virtual splitting of the structure into two parts: physical substructure that contains the key region of interest which is tested in a laboratory and numerical substructure that contains the remaining part of the structure in the form of a numerical model. This paper numerically assesses four step-by-step integration methods (Central difference method (CDM), Operator splitting method (OSM), Rosenbrock based method (RBM) and CR-integration method (CR)) which are widely used in RTHT. The methods have been assessed in terms of stability and accuracy for various realistic damping ratios of the physical substructure. The stability is assessed in terms of the spectral radii of the amplification matrix while the accuracy in terms of numerical damping and period distortion. In order to evaluate the performance of the methods, five carefully chosen examples have been studied - undamped SDOF, damped SDOF, instantaneous softening, instantaneous hardening and hysteretic system. The performance of the methods is measured in terms of a non-dimensional error index for displacement and velocity. Based on the error indices, it is observed that OSM and RBM are robust and performs fairly well in all the cases. CDM performed well for undamped SDOF system. CR method can be used for the system showing softening behaviour. The error indices indicate that accuracy of OSM is more than other method in case of hysteretic system. The accuracy of the results obtained through time integration methods for different damping ratios of the physical substructure is addressed in the present study. In the presence of a number of integration methods, it is preferable to have criteria for the selection of the time integration scheme. As such criteria are not available presently, this paper attempts to fill this gap by numerically assessing the four commonly used step-by-step methods.

• 한국디지털정책학회:학술대회논문집
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• 한국디지털정책학회 2005년도 춘계학술대회
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• pp.51-71
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• 2005

Performance measurement systems based on the principle that "if you can't measure it, you can't manage it" reinforce a short-term culture by focussing on tangible outputs. Instead, the focus of organisations should be on sustainable long-term performance through continuous systemic improvement. To establish and reinforce behaviours that drive systemic improvement, measurement and reporting systems need to be de designed to re-enforce work to role behaviour by managers. This paper discusses this concept and how it is being applied in practice through an ongoing action research project.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 추계학술대회
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• pp.740-742
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• 2015

본 연구의 목적은 최근 기업들이 출시하고 있는 분야의 첨단 융합 하이테크 제품에 대한 소비자들이 인식을 조사한 것이다. 기술의 진보와 소비자들의 욕구가 증가함에 따라 제품의 다양성과 복잡성이 날로 증가하고 있다. 이러한 혁신을 유발하는 IT 분야의 하이테크 융합제품에 대한 소비자들의 반응을 조사하였다. 이러한 조사결과를 바탕으로 소비자들이 인지하는 IT 융합제품에 대한 혁신성과 저항성에 대한 관계를 통해 기업의 성공적인 시장진입과 소비자의 욕구 충족의 근거를 제공하고자 한다.

• Steel and Composite Structures
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• 제51권6호
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• pp.619-645
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• 2024

In the construction industry, composite structures have revolutionized traditional design principles, opening innovative possibilities. The Concrete Encased - Concrete Filled Steel Tubular (CE-CFST) column stands out as a distinctive composite structure, offering structural stability and resilience for various engineering applications. Comprising Reinforced Concrete (RC) and Concrete Filled Steel Tubular (CFST) components, CE-CFST columns are valued for their inherent properties, including ductility and rigidity, CE-CFST is commonly used in the construction of bridges, high-rise buildings, and more. This article aims to provide a concise overview of the evolutionary development of CE-CFST columns and their performance in structural applications. Through a comprehensive review, the study delves into the behaviour of CE-CFST columns under different scenarios. It examines the influences of key parameters such as size, infills, cross section, failure causes, and design codes on the performance of CE-CFST columns, highlighting their enhanced functionality and future potential. Moreover, the review meticulously examines previous applications of CE-CFST columns, offering insights into their practical implementation.

• 벤처창업연구
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• 제13권2호
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• pp.51-61
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• 2018

우리 사회가 성숙해지면서 사회적 자본으로서 신뢰에 대한 관심이 커지고 있으며, 사회적 자본에 대한 연구가 시민사회와 국가경제 발전에 대한 사회학적 관심에서 출발하여 기업의 역량강화에 대한 관심으로 확산되고 있다. 특히 중소벤처기업의 경우 최소인원으로 핵심기능만을 조직화한 창업이 늘어나고, 핵심기능에 집중하는 부문별 Partner의 책임경영 체제가 강조되면서 기업의 가치창조를 결정하는 변인과 과정에 대한 관심이 커지고 있다. 본 연구는 중소벤처기업의 가치창조와 장기적 생존을 위하여 필수적인 구성원의 협력과 조직의 혁신행동을 달성하기 위한 변인과 과정을 알아보기 위하여 실증적 연구를 시도하였다. 기업조직의 수준에서 Nahapiet & Ghoshal이 제안한 사회적 자본의 3가지 차원 즉, 구조적 차원, 인지적 차원, 관계적 차원의 변수로서 조직공정성, 공유가치, 조직신뢰를 선택하고 기업성과의 선행변수인 직무만족을 거쳐 기업성과의 대용변수인 혁신행동에 긍정적 영향을 미칠 것이라는 가설을 수립하여 검정하였다. 기업의 조직구성과 운영은 사회적 계약관계이므로 조직공정성과 공유가치가 직무만족에 긍정적 영향을 미치고, 직무만족이 혁신행동에 긍정적 영향을 미치며, 조직신뢰는 직무만족과 혁신행동 사이의 관계에 매개효과를 갖는 인지적 과정과 조직적 맥락을 분석하였다. 구체적으로 직무만족이 혁신행동에 미치는 직접적 효과(69%)에 비하여 조직신뢰가 혁신행동에 미치는 간접적 효과(31%)가 작지 않게 나타났으며 상대적으로 중요한 변수로 관찰되었다. 구성원 30인 이하의 중소벤처기업의 경우에는 직접효과(36%)보다 오히려 간접효과(64%)가 더 큰 것으로 나타났으며, 이는 구성원의 직무만족을 높이기 위한 노력과 함께 조직신뢰를 최우선적으로 확보하여야 한다는 점을 보여준 것이다. 본 연구의 의의는 구성원 30인 이하의 중소벤처기업의 경우 조직신뢰가 조직공정성, 공유가치, 직무만족보다 더욱 큰 영향력을 갖는 변수라는 점을 실증적으로 확인하였다는 점에 있다. 추가적으로 혁신과 생존을 위하여 조직신뢰를 포함한 사회적 자본의 제반요소를 강화하기 위한 실행방안을 논의하였다.