• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.289-294
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• 2011

The installation of joint is to prevent random cracking due to drying shrinkage stress of concrete slab. However contraction joint spacing is empirically implemented into slab constructions without detail calculation based on quantitative criteria. In this study, shrinkage strain of concrete due to concrete shrinkage stress was measured to suggest joint spacing based on the study results. The test environmental conditions were applied temperature of $15^{\circ}C$ and relative humidity of 60%. The design compressive strength used was 30 MPa and 40 MPa, which are currently used in concrete slab designs. The drying shrinkage test result was applied to drying shrinkage models (ACI 209R, CEB MC 90, B3, GL 2000 and Sakata). The results showed that the most appropriate model was ACI 209R model. Based on the research findings, quantitative contraction joint spacing locations were calculated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.7
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• pp.1165-1172
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• 2008

In this paper, the scattering parameters of the metamaterial slab are obtained using the 2D FDTD(Finite-Difference Time-Domain) method. FDTD method is one of strongest electromagnetic numerical method which is widely used to analyze the metamaterial structure because of its simplicity. But it is very difficult to obtain frequency response of metamaterial itself because frequency dispersive model such as Lorentz, Drude model are used in FDTD. We used the well-known m-n-m cycle sine pulse to obtain the frequency response of the metamaterials. Comparisons between the wideband Gaussian input pulse and band-limited m-n-m cycle sine pulse are performed in this paper also. From the results, we concluded that the scattering parameters in frequency domain can be obtained using specific input pulse in FDTD even if the response has valid only for limited bandwidth.

• Steel and Composite Structures
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• v.39 no.4
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• pp.435-451
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• 2021

Shear lag effect was a significant mechanical behavior of steel-concrete composite beams, and the effective flange width was needed to consider this effect. However, the effective flange width is mostly determined by static load test. The cyclic vehicle loading cases, which is more practical, was not well considered. This paper focuses on the study of shear lag effect of the concrete slab in the negative moment region under fatigue cyclic load. Two specimens of two-span steel-concrete composite beams were tested under fatigue load and static load respectively to compare the differences in the negative moment region. The reinforcement strain in the negative moment region was measured and the stress was also analyzed under different loads. Based on the OpenSees framework, finite element analysis model of steel-concrete composite beam is established, which is used to simulate transverse reinforcement stress distribution as well as the variation trends under fatigue cycles. With the established model, effects of fatigue stress amplitude, flange width to span ratio, concrete slab thickness and shear connector stiffness on the shear lag effect of concrete slab in negative moment area are analyzed, and the effective flange width ratio of concrete slab under different working conditions is calculated. The simulated results of effective flange width are compared with calculated results of the commonly used specifications, and it is found that the methods in the specifications can better estimate the shear lag effect in concrete slab under static load, but the effective flange width in the negative moment zone under fatigue load has a large deviation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.75-82
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• 2019

Slab panels are very important to develop asphalt concrete (AC) track for minimizing the roadbed stress due to the train load and reducing the plastic deformation of infrared-sensitive AC. In this study, the slab panel for AC track was developed through the shape design and the indoor performance test and its structural integrity has been investigated through the finite element analysis under the flexural tensile stress and the design moment according to various static load combination by KRL-2012 standard train load model and KR-C code. In order to verify the suitability of the slab panel for AC track, static bending strength test and dynamic bending strength test were performed according to EN 13230-2. Results show that the slab panel for AC track satisfies all the performance standards required by European standards such as crack loads and crack extension.

• Coupled systems mechanics
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• v.8 no.4
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• pp.315-338
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• 2019

The numerical investigations have been carried out on reinforced concrete slab against blast loading to demonstrate the accuracy and effectiveness of the finite element based numerical models using commercial package ABAQUS. The response of reinforced concrete slab have been studied against the influence of weight of TNT, standoff distance, boundary conditions, influence of air blast and surface blast. The results thus obtained from simulations were compared with the experiments available in literature. The inelastic behavior of concrete and steel reinforcement bar has been incorporated through concrete damage plasticity model and Johnson-cook models available in ABAQUS were presented. The predicted results through numerical simulations of the present study were found in close agreement with the experimental results. The damage mechanism and stress response of target were assessed based on the intensity of deformations, impulse velocity, von-Mises stresses and damage index in concrete. The results indicate that the standoff distance has great influence on the survivability of RC slab against blast loading. It is concluded that the velocity of impulse wave was found to be decreased from 17 to 11 m/s when the mass of TNT is reduced from 12 to 6 kg. It is observed that the maximum stress in the concrete was found to be in the range of 15 to $20N/mm^2$ and is almost constant for given charge weight. The slab with two short edge discontinuous end condition was found better and it may be utilised in designing important structures. Also it is observed that the deflection in slab by air blast was found decreased by 60% as compared to surface blast.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.7
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• pp.437-443
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• 2004

In this work the AC loss measurement setup based on an iron core background magnet, not used in a conventional one, has been successfully developed. To prove its validity, a round-robin test for the same Bi-2223 tape sample among three institutes has been done. The results show that the self-field and magnetization losses from the developed setup well agree with the losses measured at two other institutes of Korea Basic Science Institute and Yokohama National University. The measured magnetization losses for parallel or perpendicular fields can be well predicted from the slab model or the strip model for a filamentary region. However the magnetization losses for longitudinal fields can be rather predicted by the slab model for a decoupled filament. The self-field losses are well explained by the Norris ellipse model.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.584-589
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• 2008

It is known that slab thermal storage which uses concrete slab as thermal material is effective in the load leveling and using the nighttime electric power. The temperature distribution is not constant in plenum in thermal storage time by beams, ducts such as several factor. It is considered that this fact will effect on efficiency of thermal storage and indoor thermal environment. The purpose of this paper is to examine the thermal environment inside plenum. A macro model was made for the analysis of indoor thermal environment as the first step. The flow rate distribution and temperature distribution of object room model was examined by use of basic equations such as airflow by the pressure difference between unit cells, heat flow by air and heat transfer.

• Nuclear Engineering and Technology
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• v.43 no.6
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• pp.523-530
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• 2011

In a previous study, the stochastic space-dependent kinetics model (SSKM) based on the forward stochastic model in stochastic kinetics theory and the Ito stochastic differential equations was proposed for treating monoenergetic space-time nuclear reactor kinetics in one dimension. The SSKM was tested against analog Monte Carlo calculations, however, for exemplary cases of homogeneous slab reactors with only one delayed-neutron precursor group. In this paper, the SSKM is improved and evaluated with more realistic and complicated cases regarding several delayed-neutron precursor groups and heterogeneous slab reactors in which the extraneous source or reactivity can be introduced locally. Furthermore, the source level and the initial conditions will also be adjusted to investigate the trends in the variances of the neutron population and fission product levels across the reactor. The results indicate that the improved SSKM is in good agreement with the Monte Carlo method and show how the variances in population dynamics can be controlled.

• Journal of Advanced Engineering and Technology
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• v.11 no.4
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• pp.279-285
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• 2018

A shear connection between the steel beam and concrete slab determines the stability of composite beams. An extensive numerical study to evaluate the resistance of the shear connection in a solid slab at high temperature was conducted. Three-dimensional thermo-mechanical finite element models were developed using a dynamic explicit method and concrete damaged plasticity model. Temperature-dependent plasticity parameters of the concrete model were proposed, and the accuracy of the developed model was obtained against experimental data. This investigation has revealed that a stud shearing failure occurs regardless of temperatures, and its shearing location changes in accordance with a rise in temperature. A new strength reduction formula has been presented to estimate the resistance of the shear connection at high temperatures.

• Advances in concrete construction
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• v.9 no.5
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• pp.511-527
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• 2020

The main aim of the current research is to investigate the flexural behavior of the reinforced concrete (RC) slabs strengthened with strain hardening cementitious composites (SHCC) experimentally and numerically. Seven RC slabs were prepared and tested under four-points loading test. One un-strengthened slab considered as control specimen while six RC slabs were strengthened with reinforced SHCC layers. The SHCC layers had different reinforcement ratios and different thicknesses. The results showed that the proposed strengthening techniques significantly increased the ultimate failure load and the ductility index up to 25% and 22%, respectively, compared to the control RC slab. Moreover, a three dimensional (3D) finite element model was proposed to analyze the strengthened RC slabs. It was found that the results of the proposed numerical model well agreed with the experimental responses. The validated numerical model used to study many parameters of the SHCC layer such as the reinforcement ratios and the different thicknesses. In addition, steel connectors were suggested to adjoin the concrete/SHCC interface to enhance the flexural performance of the strengthened RC slabs. It was noticed that using the SHCC layer with thickness over 40 mm changed the failure mode from the concrete cover separation to the SHCC layer debonding. Also, the steel connectors prevented the debonding failure pattern and enhanced both the ultimate failure load and the ductility index. Furthermore, a theoretical equation was proposed to predict the ultimate load of the tested RC slabs. The theoretical and experimental ultimate loads are seen to be in fairly good agreement.