• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.225-232
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• 1997

철근콘크리트 유공보에 있어서 기존 유공보의 연구는 유공위치를 보춤의 중앙에 위치하여 연구하였으나 철근코크리트 보의 역학적 특성활용과 시공상의 편의성을 위해 사각형 유공의 위치를 보춤 하단에 설치하여 개방형 유공보로 변형하였다. 본 연구에서는 사각형 유공보에 대한 유공크기의 세로길이를 보춤의 0.3배로 하고 가로길이를 세로길의의 1~3배로 변화시켜 보강 및 무보강 상태의 사각형 유공보와 이의 사각형 유공하부 콘크리트를 제외시킨 개방형 유공보에 있어서 총 10개의 시험체를 대상으로 하는 실험을 실시하여 시험체의 최대내력, 유공주위에서의 전단균열과 시험체의 휨인장균열, 주요위치의 변위조사, 주근 및 유공주위의 콘크리트와 보강철근의 변형도조사, 시험체의균열을 조사하여 상호변화를 비교.분석하였다. 이 연구결과로부터 개방형유공보의 유공주위 응력변형상태, 파괴메카니즘, 적절한 개방형 유공크기,설계시 고려사항을 제시하여 차후의 개방형 유공보의 계속적인 연구에 기여하고자 한다.

• Earthquakes and Structures
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• v.7 no.6
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• pp.955-967
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• 2014

Storage racks are used worldwide in industries and commercial outlets due to the advantage of lighter, faster erection and easy alteration of pallet level as required. The studies to understand the behaviour of cold formed steel pallet racks, under seismic action is one of the emerging area of research. The rack consists of perforated uprights and beams with hook-in end connector, which enables the floor height adjustments. The dynamic characteristics of these racks are not well established. This paper presents the dynamic characteristics of 3-D single bay two storey pallet rack system with hook-in end connectors, which is tested on shake table. The sweep sine test and El Centro earthquake acceleration is used to evaluate the seismic performance of the cold formed steel pallet racks. Also an attempt is made to evaluate the realistic dynamic characteristics by using STAAD Pro software. Modal analysis is performed by incorporating the effective moment of inertia of the upright, which considers the effect of presence of perforations and rotational stiffness of the beam-to-upright connection to determine the realistic fundamental frequency of pallet racks, which is required for carrying out the seismic design. Finite element model of the perforated upright section has been developed as a cantilever beam through which effective moment of inertia is evaluated. The stiffness of the hook-in connector is taken from the previous study by Prabha et al. (2010). The results from modal analysis are in good agreement with the respective experimental results.

• Steel and Composite Structures
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• v.43 no.6
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• pp.707-723
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• 2022

This article aims to investigate the size dependent bending behavior of perforated nanobeams incorporating the nonlocal and the microstructure effects based on the nonlocal strain gradient elasticity theory (NSGET). Shear deformation effect due to cutout process is studied by using Timoshenko beams theory. Closed formulas for the equivalent geometrical characteristics of regularly squared cutout shape are derived. The governing equations of motion considering the nonlocal and microstructure effects are derived in comprehensive procedure and nonclassical boundary conditions are presented. Analytical solution for the governing equations of motion is derived. The derived non-classical analytical solutions are verified by comparing the obtained results with the available results in the literature and good agreement is observed. Numerical results are obtained and discussed. Parametric studies are conducted to explore effects of perforation characteristics, the nonclassical material parameters, beam slenderness ratio as well as the boundary and loading conditions on the non-classical transverse bending behavior of cutout nanobeams. Results obtained are supportive for the design, analysis and manufacturing of such nanosized structural system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.771-776
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• 2020

In this study, the flexural/shear behavior characteristics of perfobond FRP-concrete composite beams using an FRP plate with perforated webs as formwork and reinforcement are analyzed through an analytical method. Compared with the existing experimental results, we have proved its usefulness and use it in future practice. When the nonlinearity is very large in this case, the nonlinear finite element analysis by an explicit method will be effective. The concrete damage plasticity (CDP) model adopted in this study is considered to be able to adequately simulate the nonlinear behavior of concrete, and the determination of several variable factors required in the model is compared with the experimental results and values used in the study. This recommendation will require review and adjustment for more diverse cases. The effect of the perfobond of the composite beam with perforated web is considered to be somewhat effective in terms of securing the initial stiffness, but in the case of the apex, it is considered that the cross-sectional loss and the effect of improving the bonding force should be properly arranged. The contact problem, such as slipping of the FRP plate and concrete, is considered to be one of the reasons that the initial stiffness is slightly larger than the test result, and the slightly difference from the experimental results is attributed to the separation problem between concrete and FRP after the peak.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4245-4252
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• 2015

In this study, an experiment which utilized glass fiber reinforced polymer(GFRP) plank as the permanent formwork of cast-in-place high strength concrete structures was performed. The GFRP plank currently being produced has smooth surface so that it causes problems in behavior with concrete. Therefore, this research analyzed the flexure/shear failure behavior of composite beams, which used GFRP plank as its permanent formwork and has short shear span ratio, by setting the sand coated at GFRP bottom surface, the perforation and interval of the GFRP plank web, and the width of the top flange as the experimental variables. As a result of the experiments for effectiveness of sand attachment in case of not perforated web, approximately 47% higher ultimate load value was obtained when the sand was coated than not coated case and bending/shear failure mode was observed. For effectiveness of perforation and interval of gap, approximately 24% higher maximum load value was seen when interval of the perforation gap was short and the fine aggregate was not coated, and approximately 25% lower value was observed when the perforation gap was not dense on the coated specimen. For effectiveness of top flange breadth, the ultimate load value was approximately 17% higher in case of 40mm than 20mm width.

• Journal of the Korean Society of Safety
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• v.28 no.6
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• pp.49-56
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• 2013

The statistics of recent accidents in warehouses show that a heavy toll of lives were produced by various accidents, e.g. collision, overturn, fall, slip, exposure to harmful substances or environments, etc. Of significant concern amongst them is the collision, especially the collision between forklift and storage rack structure. Accordingly, this study focuses on behavioral characteristics of rack structure subjected to dynamic impact loading of a forklift. For this purpose, time-domain response analysis has been performed on a standard 2-bay six-story rack structure consisting of columns, beams and bracing members with perforated open section. In order to investigate the most critical scenario, the impact loads are applied in both down-aisle and cross-aisle directions, and the impact locations are also varied along the shelves of the palettes. In order to deal with storage distributions, three types of rack structures are further taken into account: original empty rack structure with no storage, half-loaded rack structure and fully-loaded rack structure. The numerical simulation results demonstrate that the dynamic characteristics of the rack structure are significantly dependent on the distribution of the storage goods and its natural period varies from 0.24sec to 1.06sec, approximately 4.4 times. Further, the parametric studies show that the forklift impact is most critical to the safety of the rack structure when it collides either at the base or at the top of the rack structure.

• Journal of the Korean housing association
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• v.25 no.6
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• pp.111-121
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• 2014

The purpose of the study is to understand the unique characteristics of decoration style in traditional Javanese houses. Reviewing literature and visiting site were applied as the research method. Javanese House can be divided into three parts; roof, wall and floor. First, the roof of the traditional Javanese House is the most unique and important decorative element. The roofs are covered with roof-tiles and have clay carving ornaments on top. Usually there are no ceilings, just exposed to the oblique shape roof, which are made of wood to enable air ventilation. Joglo roof is the outstanding and representative roof type of Javanese houses. There is artistic and constructive roof structure named as tumpang sari in Joglo roof. The decoration on tumpang sari is the most colorful and symbolic ornaments. Secondly, the most unique element in the wall is the gebyok. Gebyok is made of wood and full of carved ornament, which has an artistic appearance, and also important function. The top part of doors are designed as perforated woodcarving, which give both aesthetic and ventilation purposes. Last, the stratified floor is begin with ground yard, then veranda that made from hardened clay, and main room constituted with a wood scaffold to provide air circulation and remove the humidity of the ground. The decorations of the column stand (umpak) are unique, where usually lotus flower is carved into black stone or lime stone. The outside of the buildings in Java Houses is not decorated by colors or symbols, whereas colors are only used in temples, pavilion or in royal housings. Instead they have carvings and decorations on important structural elements such as columns and beams inside. The ornaments and colors of decorations symbolize their god, ancestors and piece.

• Steel and Composite Structures
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• v.26 no.4
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• pp.485-499
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• 2018

In this paper, a hollow steel tube (HST) shear connector is proposed for use in a slim-floor system. The HST welded to a perforated steel beam web and embedded in concrete slab. A total of 10 push-out tests were conducted under static loading to investigate the mechanical behavior of the proposed HST connector. The variables were the shapes (circular, square and rectangular) and sizes of hollow steel tubes, and the compressive strength of the concrete. The failure mode was recorded as: concrete slab compressive failure under the steel tube and concrete tensile splitting failure, where no failure occurred in the HST. Test results show that the square shape HST in filled via concrete strength 40 MPa carried the highest shear load value, showing three times more than the reference specimens. It also recorded less slip behavior, and less compressive failure mode in concrete underneath the square hollow connector in comparison with the circular and rectangular HST connectors in both concrete strengths. The rectangular HST shows a 20% higher shear resistance with a longer width in the load direction in comparison with that in the smaller dimension. The energy absorption capacity values showed 23% and 18% improvements with the square HST rather than a headed shear stud when embedded in concrete strengths of 25 MPa and 40 MPa, respectively. Moreover, an analytical method was proposed and predicts the shear resistance of the HST shear connectors with a standard deviation of 0.14 considering the shape and size of the connectors.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.919-926
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• 2023

To analyze the cause of the destruction of thin, carbon-backed lithium fluoride targets during a measurement of the fusion of ⁷Li and ¹⁷O, we estimate theoretically the lifetimes of carbon and LiF films due to sputtering, thermal evaporation, and lattice damage and compare them with the lifetime observed in the experiment. Sputtering yields and thermal evaporation rates in carbon and LiF films are too low to play significant roles in the destruction of the targets. We estimate the lifetime of the target due to lattice damage of the carbon backing and the LiF film using a previously reported model. In the experiment, elastically scattered target and beam ions were detected by surface silicon barrier (SSB) detectors so that the product of the beam flux and the target density could be monitored during the experiment. The areas of the targets exposed to different beam intensities and fluences were degraded and then perforated, forming holes with a diameter around the beam spot size. Overall, the target thickness tends to decrease linearly as a function of the beam fluence. However, the thickness also exhibits an increasing interval after SSB counts per beam ion decreases linearly, extending the target lifetime. The lifetime of thin LiF film as determined by lattice damage is calculated for the first time using a lattice damage model, and the calculated lifetime agrees well with the observed target lifetime during the experiment. In experiments using a thin LiF target to induce nuclear reactions, this study suggests methods to predict the lifetime of the LiF film and arrange the experimental plan for maximum efficiency.

• Progress in Medical Physics
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• v.21 no.1
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• pp.86-92
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• 2010

The purpose of this study was to measure curvature contour skin dose using radiochromic film and TLD for a conventional open field. We also attempted to quantify the degradation of skin sparing associated with use of immobilization devices for high energy photon beams and to calculate the skin dose with a help of Monte Carlo (MC) simulation. To simulate head-and-neck and shoulder treatment, a cylindrical solid water phantom 11 cm in diameter was irradiated with 6 MV x-rays using $40{\times}40\;cm^2$ field at 100 cm source axis distance (SAD) to the center of the phantom. Aquaplastic mesh mask was placed on the surface of the cylindrical phantom that mimicked relevant clinical situations. The skin dose profile was obtained by taking measurements from $0^{\circ}$ to $360^{\circ}$ around the circumference of the cylindrical phantom. The skin doses obtained from radiochromic film were found to be 47% of the maximum dose of $D_{max}$ at the $0^{\circ}$ beam entry position and 61% at the $90^{\circ}$ oblique beam position without the mask. Using the mask (1.5 mm), the skin dose received was 59% at $0^{\circ}$ incidence and 78% at $80^{\circ}$ incidence. Skin dose results were also gathered using thin thermoluminescent dosimeters (TLD). With the mask, the skin dose was 66% at $0^{\circ}$ incidence and 80% at $80^{\circ}$ incidence. This method with the mask revealed the similar pattern as film measurement. For the treatments of the head-and-neck and shoulder regions in which immobilization mask was used, skin doses at around tangential angle were nearly the same as the prescription dose. When a sloping skin contour is encountered, skin doses may be abated using thinner and more perforated immoblization devices which should still maintain immoblization.