• Journal of the Society of Disaster Information
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• v.14 no.3
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• pp.343-351
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• 2018

Purpose: Recently, As the size of the structure increased, the necessity of reducing its weight was raised. To reduce weight In concrete structures, a hollow slab is proposed as an alternative for weight reduction effect. Method: It is difficult to construct the hollow body due to buoyancy, and the shear performance is insufficient due to the decreased cross section. Slabs were fabricated using unidirectional hollow bodies such as PVC pipes, and experiments were conducted about construction performance and structural performance. Results: The buoyancy preventive device has been improved the construction performance by preventing floating hollow body, it has been confirmed that it has adequate performance to be used as a hollow slab system because it has enough expected shear performance. Coclusion: Hollow ratio has a little connection with bending performance, but after the yielding load, it is necessary to consider the secondary stiffness of structure, and is is supposed that the decrease of shear performance with the increase of hollow core ratio can be complemented with shear reinforcement.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2682-2695
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• 2021

This paper aims to evaluate the structural dynamic responses and damage/failure of the nuclear fuel reprocessing plant under the free drop impact of spent fuel cask (SFC) and fuel assembly (FA) during the on-site transportation. At the present Part I of this paper, the large-scale SFC model free drop test and the corresponding numerical simulations are performed. Firstly, a composite target which is composed of the protective structure, i.e., a thin RC plate (representing the inverted U-shaped slab in the loading shaft) and/or an autoclaved aerated concrete (AAC) blocks sacrificial layer, as well as a thick RC plate (representing the bottom slab in the loading shaft) is designed and fabricated. Then, based on the large dropping tower, the free drop test of large-scale SFC model with the mass of 3 t is carried out from the height of 7 m-11 m. It indicates that the bottom slab in the loading shaft could not resist the free drop impact of SFC. The composite protective structure can effectively reduce the damage and vibrations of the bottom slab, and the inverted U-shaped slab could relieve the damage of the AAC blocks layer dramatically. Furthermore, based on the finite element (FE) program LS-DYNA, the corresponding refined numerical simulations are performed. By comparing the experimental and numerical damage and vibration accelerations of the composite structures, the present adopted numerical algorithms, constitutive models and parameters are validated, which will be applied in the further assessment of drop impact effects of full-scale SFC and FA on prototype nuclear fuel reprocessing plant in the next Part II of this paper.

• Journal of the Korean Wood Science and Technology
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• v.50 no.5
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• pp.301-314
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• 2022

The moisture and dimensional behaviors of a nail-laminated timber (NLT)-concrete slab composed of an NLT-plywood composite and topping concrete are monitored for 385 days. The slab is developed for using as flexural elements such as floors. The humidity control of wood gently introduces significant fluctuations under the ambient relative humidity into the slab, and fluctuations in the relative humidity result in dimensional changes. The equilibrium moisture content of the slab increases from 6.7% to 15.3% during the monitoring period, resulting in a width (radial) strain of 0.58%. The length (longitudinal) strain is negligible, and the height (tangential) strain is excluded from the analysis because of abstruse signal patterns generated. Concrete pouring causes a permanent increase in the width of the NLT-plywood composite. However, the width deforms because the weight of the concrete mixture loosens the nail-laminated structure, not because of the significant amount of moisture in the mixture. The dimensional stabilization effect of the nail-laminated system is demonstrated as the composite strain is lower than the total strain of lumber and plywood, which are elements constituting the nail-laminated structure.

• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.167-180
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• 2022

A strategic structure when exposed to direct hit of conventional bomb/projectile are severely damaged because of large amounts of energy released by the impact and penetration of bomb. When massive concrete slabs suffer a direct hit, the energy released during impact and penetration process are able to easily break up large mass of concrete. When over stressed under such impact of bombs, the concrete structure fails showing brittle behavioural nature. This paper is intended to study and suggest the protective measures for structures used for strategic application by adopting a means to dissipate the large quantum of energy released. To quantitatively evaluate the force, displacement and energy in such scenario, a fine numerical model of the proposed layered structure of different combinations was built in ANSYS programme in which tri-nitrotoluene (TNT) explosive was detonated at penetration depth calculated for GP1000 Lbs bomb. The distinct blast mitigation effect of the proposed structure was demonstrated by adopting various layers/barriers created as protective measures for the strategic structure. The calculated result shows that the blast effect on the structure is potentially reduced due to provision of buster slab with sand cushioning provided as protective measure to the main structure. This concept of layered protective measures may be adopted for safeguarding strategic structures such as Domes, Tunnels and Underground Structures.

• Journal of the Korean Institute of Educational Facilities
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• v.26 no.2
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• pp.3-10
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• 2019

This study evaluated the vibration use and safety of students living in the dormitories on the 12th and 14th floors by feeling uncomfortable. The measurement method was to measure the acceleration due to free vibration and single - person walking. The slab stiffness was then calculated, and the usability and safety were compared according to international standards. The natural frequency of the slab was 6.8 Hz. The natural frequency of a typical slab is around 15Hz. Therefore, the evaluation slab is judged as a flexible floor structure. It is considered that there is a high possibility of resonance in the middle of daily life because of low natural frequency and near harmonic component of walking vibration. As a result, the RMS acceleration level is within the tolerance range defined by ISO 10137 code, but the 13th floor exceeds the reference limit, so that a sensitive person could detect the vibration somewhat in the lying position.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.11
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• pp.1-7
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• 2000

Surface wave scattering by periodic grooves of arbitrary profile in a grounded dielectric slab is investigated for the TE surface wave incidence. Both the finite and infinite periodic geometries are considered. The former case is analyzed by using of hybrid FEM/MOM and the latter by using of full MOM procedure. Some numerical results for the reflected and transmitted powers in a grounded dielectric slab, radiation power into the free space, and radiation patterns in case of finite structure and for the dispersion diagram in case of infinite structure are presented. And some descriptions on the relationship between the finite and infinite structure such as the maximum beam angle are given.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.836-841
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• 2004

Recently, the development of the paved track is required as a Low-maintenance of conventional line. The main reason is that the line capacity and bearing of track are increased progressively. The most important factor of paved track is stability and applicability. To be based on this subject, Cement Mortar Pouring(CMP) paved track is developed. CMP paved track is a kind of ballast reinforced track using the pre packed concrete technique. The most important to design is characteristics of the structure. CMP slab's thickness is less than the conventional slab track and pouring layer is attached tie and roadbed directly. On this paper, to verify the basic structure of the CMP track, characteristics of the structure is investigated pouring layer, tie and interaction of the each layer using the 3D finite elment analysis.

• Structural Engineering and Mechanics
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• v.13 no.5
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• pp.465-478
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• 2002

This study lays emphasis on the development of efficient analytical models for a multistory structure with wings, including the in-plane deformation of floor slabs. For this purpose, a multistory structure with wings is regarded as the combination of multistory structures with rectangular plan and their junctions. In addition, a multistory structure with a rectangular plan is considered to be an assemblage of two-dimensional frames and floor slabs connecting two adjacent frames at each floor level. This modeling, concept can be easily applied to multistory structures with plans in the shape of L, T, Y, U, H, etc. To represent the in-plane deformation of floor slabs efficiently, a two-dimensional frame and the floor slab connecting two adjacent frames at each floor level are modeled as a stick model with two degrees of freedom per floor and a stiff beam with shear deformations, respectively. Three models are used to investigate the effect of in-plane deformation of the floor slab at the junction of wings on the seismic behavior of structures. Based on the comparison of dynamic analysis results obtained using the proposed models and three-dimensional finite element models, it could be concluded that the proposed models can be used as an efficient tool for an approximate analysis of a multistory structure with wings.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.5
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• pp.11-21
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• 2009

Considering that the weight of a biaxial hollow slab system is not increased with an incremental increase in its thickness, and that the flexural stiffness of a biaxial hollow slab is not significantly lower than that of a general solid slab, there has been a growing need for biaxial hollow slab systems, because long span structures are in great demand. In a long span structure, the problem of vibration of floor slabs frequently occurs, and the dynamic characteristics of a biaxial hollow slab system are quite different from the conventional floor systems. Therefore, in this study, the floor vibration of a biaxial hollow slab system subjected to walking load is investigated in comparison with a conventional floor slab system. For the efficiency of time history analysis, an equivalent plate slab model that can precisely represent the dynamic behavior of a biaxial hollow slab system is used. From the analytical results, it was determined that vibration of a biaxial hollow slab system subjected to walking load is evaluated as "office-level vibration," according to the classifications of the architectural institute of Japan and ANSI.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4A
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• pp.245-253
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• 2012

In the longway tunnel and underground traffic road, the structure of transverse ventilation system is constructed by the airpit slab. In this study, the full scale specimens of the PSC airpit slab that attached fire resistance panel are performed the static and dynamic loading tests for evaluation of bending capacity. The first of all, it confirmed the evaluations about the fundamental efficiency of the fire resistance panel and PSC slab by the 3-point bending test and pull-off test. The tests are performed for evaluation of the bending resistance under ultimate static load and the bonded capacity under dynamic fatigue load. A fatigue test is performed for an investigation of the effect on wind pressure that is developed by transit of traffic. The damage or debonding on surface between fire resistance panel and PSC slab was not developed in dynamic fatigue load test, also the behavior of the specimens is very stable and the debonding of the fire resistance panel attached at the bottom surface of PSC slab was not developed in static load test, too. Therefore, the crack or debonding of the fire resistance panel will be not developed by external loads during the construction or completion of the precast fire resistance system.