• 소성∙가공
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• 제25권2호
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• pp.102-108
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• 2016

The aim of the current study was to develop an advanced prediction model for the slab width spread during hot rough rolling. Rough rolling consists of both vertical rolling using a set of profiled edger rolls and horizontal rolling using a set of plain work rolls. FE-simulations were performed to investigate the influences of process variables such as initial slab width, initial thickness, sizing draft, edger roll draft and work roll draft on the final slab width variation. From a statistical analysis of the simulation results, an advanced model, which can predict the slab width spread during the edger rolling and horizontal rolling, was developed. The experimental hot rolling trials showed that the newly developed model provided fairly accurate predictions on the slab width spread during hot rough rolling process using a profiled edger rolls.

• Investigative Magnetic Resonance Imaging
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• 제15권1호
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• pp.77-81
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• 2011

조영 증강 MR 혈관조영 영상에서 척추동맥 기시부의 협착이 과장되어 보이며 종종 가성협착율을 보인다는 것은 잘 알려져 있다. 그러나 뇌의 후방순환의 허혈, 경색의 임상적 중요성을 고려하면, 척추동맥 기시부 협착의 정확한 진단은 매우 중요하다. 따라서 저자들은 thin-slab maximum-intensity projection(MIP) 영상을 이용하여 통상적인 full thickness MIP 영상에서 보이는 척추동맥 기시부의 진성협착과 가성협착을 구분하고자 한다.

• 한국주거학회논문집
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• 제17권3호
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• pp.61-69
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• 2006

Vertical vibrations on the slab of buildings are affected by types of vibration sources, transfer paths, and the material property and the size of members. Among these parameters, the vibration sources and the transfer path can not be controlled, but the property and the size of members can be controlled in the phase of design the members. In this study, the vibration responses according to the property and size of members were obtained by using a prediction program based on dynamic-stiffness matrix. Three parameters which are not usually considered as major factors for architecral planning were selected fur these analyses. They are the strength of materials, the thickness of wall and the thickness of slab. The ground vibration source located near a building was used as vibration input data in the analyses. This study has its originality on presenting appropriate property and size of structural members in order to reduce vertical vibration of slab in shear-wall structures. Analysing the results from the vibration estimation program according to the variations of parameters, the appropriate ratio among the sizes of structural members were proposed. From these results, the vibration level on the slab which is not constructed yet would be predicted and the vibration peak level can be reduced or shifted into the desirable frequency range. Therefore, the vertical vibration could be controlled in the phase of designing buildings.

• 한국건설순환자원학회논문집
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• 제12권3호
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• pp.298-305
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• 2024

본 논문은 철근콘크리트 슬래브의 바닥 충격음을 개선하기 위한 기초연구이다. 시공에 의해 두께의 차이가 발생하는 경우를 고려하여 철근콘크리트 슬래브의 단면을 모르타르로 회복시켰을 경우 차음 특성의 변화를 분석 하였다. 분석 대상 주택은 평면형식이 다른 84 type와 59 type의 2종류로 하였으며, 철근콘크리트 슬래브 위에 단면을 회복하기 위해 중량모르타르로 단면 회복용 모르타르 시공할 때를 철근콘크리트 슬래브 단독과 일반 모르타르로 단면 회복용 모르타르 시공한 경우와 비교하여 진동가속도레벨과 음압의 차이를 측정하였다. 모르타르를 타설 후 슬래브에 대해 진동가속도 레벨을 측정한 결과, 84 type 63 Hz에서 CS 모르타르가 66.4 dB, ES 모르타르가 66.1 dB로 일반 모르타르에 비해 2 dB 이상 낮게 나타났다. 또한 철근콘크리트 슬래브 단독과 비교할 때 CS 모르타르가 5.5 dB, ES 모르타르가 4.6 dB이 저감되어 비교적 우수한 값을 보였다. 바닥충격음 음압은 결과의 경우, 84B type이 63 Hz에서 CS 모르타르와 일반 모르타르가 67.3 dB로 유사하게 나타났으며, 철근콘크리트 슬래브 단독 대비 저 감량은 CS 모르타르가 3.6 dB, ES 모르타르가 2.7 dB, 일반 모르타르가 1.4 dB 저감되었다. 철근콘크리트 슬래브의 두께를 보상하기 위하여 모르타르를 타설함으로서 진동가속도레벨 및 바닥충격음은 감소하였으며, 동제련 슬래그 잔골재를 사용한 중량모르타르를 사용할 경우 상대적으로 우수한 성능을 발현하는 것으로 나타났다.

• Structural Monitoring and Maintenance
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• 제10권1호
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• pp.1-23
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• 2023

Various efforts have been made to reduce the weight of concrete slabs while preserving their flexural strength. This will result in reducing deflection and allows the utilization of longer spans. The top zone of the slab requires concrete to create the compression block for flexural strength, and the tension zone needs concrete to join with reinforcing for flexural strength. Also, the top and bottom slab faces must be linked to transmit stresses. Voided slab systems were and are still used to make long-span slab buildings lighter. Eight slab specimens of (1000^*1000 (1000^*1000 mm²) were cast and tested as two-way simply supported slabs in this research. The tested specimens consist of one solid slab and seven voided slabs with the following variables (type of slab solid and voided), thickness of slab (100 and 125 mm), presence of steel fibers (0% and 1%), and the number of GFRP layers). The voids in slabs were made using high-density polystyrene of dimensions (200^*200^*50 mm) with a central hole of dimensions (50^*50^*50 mm) at the ineffective concrete zones to give a reduction in weight by (34% to 38%). The slabs were tested as simply supported slabs under partial uniform loading. The results of specimens subjected to monotonic loading show that the combined strengthening by steel fibers and GFRP sheets of the concrete specimen (V-125-2GF-1%) shows the least deflection, deflection (4.6 mm), good ultimate loading capacity (192 MPa), large stiffness at cracking and at ultimate (57 and 41.74) respectively, more ductility (1.44), and high energy absorption (1344.83 kN.mm); so it's the best specimen that can be used as a voided slab under this type of loading.

• 대한기계학회논문집
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• 제15권1호
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• pp.376-385
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• 1991

본 연구에서는 그루브의 각도에 따라 그루브 에징을 한 형상과 상사하게 가상 의 슬라브를 제작하여 오버랩에 영향을 미치는 압연인자들을 분석하고 그 영향을 검토 함으로써 최적 G 롤의 각도를 결정하였고, 최적인 G 롤의 형상으로 에저를 제작하여 G 에징량에 따른 오버랩량의 변화를 고찰하였다.

• Computers and Concrete
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• 제25권4호
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• pp.355-367
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• 2020

This paper proposed a numerical investigation based on finite elements analysis (FEA) in order to study the punching shear behavior of reinforced concrete (RC) flat slabs using ABAQUS and SAP2000 programs. Firstly, the concrete and the steel reinforcements were modeled by hexahedral 3D solid and linear elements respectively, and the nonlinearity of the used materials was considered. In order to validate this model, experimental results considered in literature were compared with the proposed FE model. After validation, a parametric study was performed. The parameters include the slab thickness, the flexure reinforcement ratios and the axial membrane loads. Then, to reduce the time of FEA, a simplified modelling using 3D layered shell element and shear hinge concept was also induced. The effect of the footings settlement was studied using the proposed simplified nonlinear model as a case study. Results of numerical models showed that increase of the slab thickness by 185.7% enhanced the ultimate load by 439.1%, accompanied with a brittle punching failure. The punching failure occurred in one of the tested specimens when the tensile reinforcement ratio increased more than 0.65% and the punching capacity improved with increasing the horizontal flexural reinforcement; it decreased by 30% with the settlement of the outer footings.

• Steel and Composite Structures
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• 제18권2호
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• pp.375-394
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• 2015

This paper presents the results of four long-term experiments carried out to investigate the time-dependent behaviour of composite floor slabs with particular attention devoted to the development of non-uniform shrinkage through the slab thickness. This is produced by the presence of the steel deck which prevents moisture egress to occur from the underside of the slab. To observe the influence of different drying conditions on the development of shrinkage, the four 3.3 m long specimens consisted of two composite slabs cast on Stramit Condeck $HP^{(R)}$ steel deck and two reinforced concrete slabs, with the latter ones having both faces exposed for drying. During the long-term tests, the samples were maintained in a simply-supported configuration subjected to their own self-weight, creep and shrinkage for four months. Separate concrete samples were prepared and used to measure the development of shrinkage through the slab thickness over time for different drying conditions. A theoretical model was used to predict the time-dependent behaviour of the composite and reinforced concrete slabs. This approach was able to account for the occurrence of non-uniform shrinkage and comparisons between numerical results and experimental measurements showed good agreement. This work highlights the importance of considering the shrinkage gradient in predicting shrinkage deformations of composite slabs. Further comparisons with experimental results are required to properly validate the adequacy of the proposed approach for its use in routine design.

• Steel and Composite Structures
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• 제21권6호
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• pp.1307-1325
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• 2016

Nonlinear behavior of two-span, continuous composite steel-concrete girders strengthened with Carbon Fiber Reinforced Polymers (CFRP) bonded to the top of concrete slab over the negative moment region was evaluated using a non-linear Finite Element (FE) model in this paper. A three-dimensional FE model of continuous composite girder using commercial software ABAQUS simulated and validated with experimental results. The interfacial regions of the composite girder components were modeled using suitable interface elements. Validation of the proposed numerical model with experimental data confirmed the applicability of this model to predict the loading history, strain level for the different components and concrete-steel relative slip. The FE model captured the different modes of failure for the continuous composite girder either in the concrete slab or at the interfacial region between CFRP sheet and concrete slab. Through a parametric study, the thickness of CFRP sheet and shear connection required to develop full capacity of the continuous composite girder at negative moment zone have been investigated. The FE results showed that the proper thickness of CFRP sheet at negative moment region is a function of the adhesive strength and the positive moment capacity of the composite section. The shear connection required at the negative moment zone depends on CFRP sheet's tensile stress level at ultimate load.

• Steel and Composite Structures
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• 제45권2호
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• pp.219-230
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• 2022

The aim of this paper is to study the mechanical behaviors of the cold-formed thin-walled steel and reinforced concrete sandwich composite slab (CTS&RC-SCS) under vertical loads and to develop the calculation methods of its flexural bearing capacity and section stiffness. Two CTS&RC-SCS specimens were designed and manufactured to carry out the static loading test, and meanwhile, the numerical simulation analyses based on finite element method were implemented. The comparison between experimental results and numerical analysis results shows that the CTS&RC-SCS has good flexural capacity and ductility, and the accuracy and rationality of the numerical simulation analysis are verified. Further, the variable parameter analysis results indicate that neither increasing the concrete strength grade nor increasing the thickness of C-sections can significantly improve the flexural capacity of CTS&RC-SCS. With the increase of the ratio of longitudinal bars and the thickness of the composite slab, the flexural capacity of CTS&RC-SCS will be significantly increased. On the basis of experimental research and numerical analysis above, the calculation formula of the flexural capacity of CTS&RC-SCS was deduced according to the plastic section design theory, and section stiffness calculation formula was proposed according to the theory of transformed section. In terms of the ultimate flexural capacity and mid-span deflection, the calculated values based on the formulas and the experimental values are in good agreement.