• Journal of the Korea Institute of Building Construction
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• v.2 no.4
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• pp.163-168
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• 2002

The object of this study is to define the characteristics of high performance concrete with varing compressive strength of concrete and curing temperature. The major test variables are 1) high strength concrete(500kg/$cm^2$) and ordinary strength concrete(240kg/$cm^2$) compressive strength, 2) curing temperature and condition, 3) concrete curing age, 4) three types of cement. From the test results were shown that curing temperature and curing conditions were also very effective for high strength concrete and ordinary strength concrete, and concrete were largely effected by cement type and temperature during the hydration reaction process. This paper describes the effect of curing temperature for strength and characteristics of high performance concrete.

• Magazine of the Korea Concrete Institute
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• v.15 no.6
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• pp.78-84
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• 2003

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2006.11a
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• pp.529-532
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• 2006

The application of ubiquitous technology offers many chances for improving construction management technologies. Currently the Construction System Integration Lab (CSIL) at Pusan National University is executing research on applying ubiquitous technology for better communication in the construction process. One of the research area is the implementation of RFID for monitoring the concrete pour process. The objective of this study is to collect data occurring in the process and use the data be properly planning concrete pour activities. Case study has been done on an actual concrete work. For the study a user environment was developed interfacing on internet with RFID devices that were installed in a batch plant and a construction site. The result of the test demonstrated that the RFID-based concrete monitoring can be a feasible approach for improving the communication in the construction process.

• Computers and Concrete
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• v.12 no.5
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• pp.717-737
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• 2013

In this study, experiment and numerical analysis were conducted to identify the heat transfer characteristics and behavior of high-strength concrete upon a fire. The numerical analysis was employed to forecast the characteristics and properties of the high-strength concrete upon a fire, which can not be accomplished through a fire test due to the specific conditions and restrictions associated with the test. The result of the numerical analysis was compared with that of the test to verify the reliability of the analysis. In the numerical analysis of the heat transfer characteristics and behavior of 80 and 100 MPa high-strength concrete upon a fire, the commercial software of ABAQUS(V.6.8) was used. It was observed from the experiment that the contraction of the concrete with fiber-cocktail was mitigated by 25~55 % compared with that without fiber-cocktail because the fiber controlled the heat transfer of the concrete and thus improved the fire-resistance performance of the column.

• Journal of the Korea Concrete Institute
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• v.26 no.1
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• pp.57-62
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• 2014

In this study, the vertical pipe cooling method was developed to propose the pipe cooling method suited for the vertically long mass concrete structures. FEM (finite element method) analysis was carried out to investigate the validity of the vertical pipe cooling method, and the temperature, the behavior of tensile stress of concrete and the crack index were investigated. In result, it was confirmed that the vertical pipe cooling method was effective in the thermal cracking control of mass concrete member.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.173-175
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• 2012

Temperature during concrete curing can be effectively used to predict the early age strength of concrete However, various current methods have limits to provide the temperature data in real time due to harsh working environment including frequent cutting of wires. This paper presents the results of our investigation of an all-in-one Wireless sensor network (WSN) for the management of the curing temperature of in-placed concrete at early curing stages. Also, the network device for transmission can be easily separated from the probe sensor part and reused consistently. The field experiment entailed measuring the curing temperature of concrete using the WSN. After fresh concrete was poured into the formworks, the signals were measured at a 150 m radius from the field office. The signal was acquired for 28 days without any dispersion or interruption at the construction site; therefore, this study confirms the applicability of the proposed system to a construction site.

• Structural Engineering and Mechanics
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• v.52 no.4
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• pp.701-721
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• 2014

In the assessment of existing RC buildings, the reliable appraisal of the compressive strength of in-situ concrete is a fundamental step. Unfortunately, the data that can be obtained by the available testing methods are typically affected by a high level of uncertainty. Moreover, in order to derive indications about the degradation and ageing of the materials by on site tests, it is necessary to have the proper terms of comparison, that is to say, to know the reference data measured during the construction phases, that are often unavailable when the building is old. In the cases when such a comparison can be done, the in situ strength values typically turn out to be lower than the reference strength values (tests performed on taken samples during the construction). At this point, it is crucial to discern and quantify the specific effect induced by different factors: ageing of the materials; poor quality of the placement, consolidation or cure of the concrete during the construction phases; damage due to drilling. This paper presents a procedure for correlating the destructive compressive tests and non-destructive tests (ultrasonic pulse velocity tests) with the data documenting the compressive strength tested during the construction phases. The research work is aimed at identifying the factors that induce the difference between the in-situ strength and cubes taken from the concrete casting, and providing, so, useful information for the assessment procedure of the building.

• Steel and Composite Structures
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• v.35 no.1
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• pp.93-109
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• 2020

Developed from conventional concrete filled steel tubular (CFST) members, concrete-encased CFST has attracted growing attention in building and bridge practices. In actual construction, the inner CFST is erected prior to the casting of the outer reinforced concrete part to support the construction preload, after which the whole composite member is under sustained service load. The complex loading sequence leads to highly nonlinear material interaction and consequently complicated structural performance. This paper studies the full-range behaviour of concrete-encased CFST columns with initial preload on inner CFST followed by sustained service load over the whole composite section. Validated against the reported data obtained from specifically designed tests, a finite element analysis model is developed to investigate the detailed structural behaviour in terms of ultimate strength, load distribution, material interaction and strain development. Parametric analysis is then carried out to evaluate the impact of significant factors on the structural behaviour of the composite columns. Finally, a simplified design method for estimating the sectional capacity of concrete-encased CFST is proposed, with the combined influences of construction preload and sustained service load being taken into account. The feasibility of the developed method is validated against both the test data and the simulation results.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.166-167
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• 2016

Unlike the past, supported by the development of digital technologies, free-form buildings are frequently designed with creative thoughts of architectural designers. However, there are some difficulties preventing successfully completion of projects, like reduced productivity and increased construction duration and cost upon the process of producing and installing concrete panels for free-form structures. In particular, there are active studies on the CNC machine for production of free-form concrete panels. Yet, it is difficult to effectively and easily come up with information on production and installation of free-form, curve-surfaced panels which are difficult to be mathematically defined. This requires a lot of manpower and time to implement the curved surfaces of free-form buildings as intended by architects. Accordingly, it needs a model that can effectively create production-installation data of free-form concrete panels for successful free-form building projects. Thus, the purpose of the study is to suggest data estimation model of production-installation using mathematical algorithm in free-form concrete panels. The study results will realize effective production and installation of free-form concrete members, allowing improved productivity of projects, reduced cost and shortened construction duration.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.88-89
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• 2015

In cold weather, the speed of concrete strength development is slow. As a result, construction speed becomes slow and it is problem for all construction site to solve this. So in this study, to shorten removing frame time after placing concrete, mix proportion using early-strength-binder(ESB) and curing method such as using heat line in concrete was considered. At first, concrete mix proportion was examined at -5℃ temperature between ordinary portland cement(OPC) and ESB. And second step, concrete, using mix proportion with OPC, was examined according to curing method(: 1) heat line used and 2) no heat line) and kinds of form (: 1) Deck slab, 2) Half PC slab and 3) SOG slab). All cases are same condition: slab thickness is 1,500mm, double-bubble sheet is used as a curing sheet after placing concrete. After the test, OPC is enough to get strength compared to ESB in special condition and 48~60 hours is needed according to form condition.