• 소성∙가공
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• 제21권1호
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• pp.58-66
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• 2012

The work roll surface temperature rises and falls repetitively during hot slab rolling because the work roll surface is cooled continuously by water. This study focused on Std. No. 7 to determine a cooling method which significantly reduces the tangential tensile stresses on the work roll surface of the hot slab mill at Hyundai Steel Co. in Korea. A series of finite element analyses were performed to compute the temperature distribution and the tensile stresses in the circumferential direction of the work roll. The virtual slab model was used to reduce the run time considerably by assigning a high temperature to the virtual slab. Except for the heat generated by plastic deformation, this is equivalent to the hot rolling condition that a high temperature slab (material) would experience when in contact with the work rolls. Results showed that when the virtual slab model was coupled with FE analysis, the run time was found to be reduced from 2000 hours to 70 hours. When the work roll surface cooled with a certain on-off patter of water spray, the magnitude of the tangential stresses on the work rolls were decreased by 54.1%, in comparison with those cooled by continuous water spraying. Savings of up to 83.3% in water usage are possible if the proposed water cooling method is adopted.

• 한국소음진동공학회논문집
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• 제19권2호
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• pp.162-168
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• 2009

In this study, numerical analysis is performed to investigate the sound radiation characteristics of an apartment house according to the type of the slab system. In order to satisfy the boundary condition of the apartment house, the whole floor is modelled with FEM model for three different structural system: wall, RC, flat slab system. From the analytical results, it is shown that heavy weight floor impact noise of wall type slab is larger than that of the other slab systems and the noise radiated from the wall have great effect on the sound pressure level. The results also show that the vibration energy of RC or flat slab system is widely distributed over the whole slab, which is main reason that the noise induced by the slab systems is reduced in comparison with wall slab system.

• Geomechanics and Engineering
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• 제13권5호
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• pp.881-892
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• 2017

Design and management of concrete slabs in concrete-faced rock-fill dams are crucial issues for stability and overall dam safety since cracks in the concrete face induced by stress, shrinkage, and deterioration can cause severe leakage from the reservoir into the dam. Especially, the increase of dam height to a certain level to enhance the storage capacity and to improve hydraulic stability can lead to undesirable deformation behavior and stress distribution in the existing dam body and in the concrete slabs. In such conditions, simulation of a concrete slab with a numerical method should involve the use of an interface element because the behavior of the concrete slab does not follow the behavior of the dam body when the dam body settles due to the increase of dam height. However, the interfacial properties between the dam body and the concrete slab have yet to be clearly defined. In this study, construction sequence of a 125 m high CFRD in South Korea is simulated with commercial FDM software. The proper interfacial properties of the concrete slab are estimated based on a comparison to monitored vertical displacement history obtained from the concrete slab. Possibility of shear strength failure under the critical condition is investigated based on the simplified model. Results present the significance of the interfacial properties of the concrete slab.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.379-384
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• 2009

It is of great importance to assure the running safety and ride comfort in designing the floating slab track for the mitigation of train-induced vibration. In this paper, for this, analyzed are the system requirements for the running safety and ride comfort, and then, the behavior of train and track at the transition zone between the floating slab track and the conventional concrete slab track according to several main design variables such as spring constant, damping coefficient, spacing and arrangement of isolators and slab length, using the dynamic analysis technique considering the train-track interaction. The results of numerical analysis demonstrate that the discontinuity of the support stiffness at the transition results in a drastic increase of the vertical vibration acceleration of the train body, wheel-rail interaction force, rail bending stress and uplift force. The increase becomes higher with the decrease of the spring constant of isolators and the increase of the isolator spacing, but the damping ratio does not significantly affect the behavior of train and track at the transition. Therefore, to assure the running safety and ride comfort, simultaneously increasing the effectiveness of vibration isolation, it is effective to minimize the relative vertical offset between the floating slab and the conventional track slab by adjusting the spring constant and spacing of isolators at the transition.

• Structural Monitoring and Maintenance
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• 제9권3호
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• pp.271-287
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• 2022

This study investigates the bending behavior of a composite concrete slab roof with different methods of externally strengthing using steel plates and carbon fiber reinforced polymer (CFRP) strips. First, the concrete slab model which was reinforced with CFRP strips on the bottom surface of it is validated using experimental data, and then, using numerical modeling, 7 different models of square-shaped composite slab roofs are developed in ABAQUS software using the finite element modeling. Developed models include steel rebar reinforced concrete slab with variable thickness of CFRP and steel plates. Considering the control sample which has no external reinforcement, a set of 8 different reinforcement states has been investigated. Each of these 8 states is examined with 6 different uncertainties in terms of the properties of the materials in the construction of concrete slabs, which make 48 numerical models. In all models loading process is continued until complete failure occurs. The results from numerical investigations showed using the steel plates as an executive method for strengthening, the bending capacity of reinforced concrete slabs is increased in the ultimate bearing capacity of the slab by about 1.69 to 2.48 times. Also using CFRP strips, the increases in ultimate bearing capacity of the slab were about 1.61 to 2.36 times in different models with different material uncertainties.

• Structural Engineering and Mechanics
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• 제86권3호
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• pp.417-430
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• 2023

As the key part in the reinforced concrete column-steel beam (RCS) frame, the beam-column joints are usually subjected the axial force, shear force and bending moment under seismic actions. With the aim to study the seismic behavior of RCS joints with and without RC slab, the quasi-static cyclic tests results, including hysteretic curves, slab crack development, failure mode, strain distributions, etc. were discussed in detail. It is shown that the composite action between steel beam and RC slab can significantly enhance the initial stiffness and loading capacity, but lead to a changing of the failure mode from beam flexural failure to the joint shear failure. Based on the analysis of shear failure mechanism, the calculation formula accounting for the influence of RC slab was proposed to estimate shear strength of RCS joint. In addition, the finite element model (FEM) was developed by ABAQUS and a series of parametric analysis model with RC slab was conducted to investigate the influence of the face plates thickness, slab reinforcement diameter, beam web strength and inner concrete strength on the shear strength of joints. Finally, the proposed formula in this paper is verified by the experiment and FEM parametric analysis results.

• 한국구조물진단유지관리공학회 논문집
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• 제16권3호
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• pp.99-108
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• 2012

본 연구에서는 철근콘크리트 슬래브의 내부식성과 경량화를 도모하기 위하여 GFRP bar를 휨보강근으로 사용하는 경량골재콘크리트 슬래브를 고려하고 이 구조물에 대하여 기초적인 거동을 조사하였다. 경량콘크리트의 압축강도 및 인장강도 그리고 콘크리트 파괴에너지 측정, 일련의 슬래브 휨실험, 비선형유한요소해석을 통한 수치해석, 휨실험과 수치해석의 결과비교 등이 행하여졌다. 그 결과, GFRP bar를 휨보강근으로 사용한 경량콘크리트 슬래브는 기준시험체로 사용된 동일 규격의 철근콘크리트 슬래브에 비하여 무게를 28%정도 감소시킬 수 있었지만 파괴하중은 36%정도 감소되었다. 이는 GFRP bar의 낮은 축강성과 경량콘크리트의 낮은 부착강도 때문인 것으로 판단된다. 그리고 경량콘크리트의 부착력 감소 특성을 고려하기 위하여 GFRP bar와 콘크리트 경계면 사이에 계면요소를 사용한 수치해석 결과는 계면요소의 사용이 실험결과에 더 근접해갈 수 있는 방법임을 보여주었다.

• 한국건축시공학회지
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• 제17권1호
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• pp.31-37
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• 2017

최근에는 공사기간을 단축하기 위해서 데크플레이트 외에 half PC 슬래브의 사용도 점차적으로 증가하고 있는 실정이다. PC 슬래브 위에 후타설되는 topping concrete 의 건조수축 변형이 PC 슬래브에 의해 구속을 받게 되므로 topping concrete 에 건조수축에 의한 균열이 발생할 수 있다. 따라서 half PC 슬래브의 품질을 향상시키고 내구성능을 증가시키기 위해서 건조수축에 의한 half PC 슬래브의 거동을 사전에 정확히 예측하는 것이 중요하다. 하지만 아직까지 half PC 슬래브의 수축거동 예측에 관한 연구결과가 없는 실정이므로 본 연구에서는 half PC 슬래브를 대상으로 건조수축거동을 관찰하였으며, 크리프특성을 고려한 증분법에 의한 수축거동을 예측한 후 실측값과 비교하여 그 타당성을 검토하였다. 그 결과 건조수축의 구속작용에 의해 half PC 슬래브에 발생하는 인장변형률은 구속률 개념과 증분법을 적용하여 예측이 가능한 것으로 확인되었다.

• 한국건설관리학회논문집
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• 제18권5호
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• pp.3-10
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• 2017

HBS 슬래브는 PSC슬래브 상부에 경량체를 설치하고 이웃하고 있는 PSC슬래브의 두 개 리브가 현장 토핑 콘크리트에 의해 형성된 현장 리브와 결합함으로서 동일축상에서 단일 부재로 거동하는 공법이다. 본 연구의 목적은 PSC 슬래브 공법에 관하여 실험적 연구를 통하여 기존 공법과의 성능 비교를 구현 하는 것이다. 본 연구에서는 기존 공법의 한계를 개선하는 공법으로 HBS 슬래브를 개발하였으며 그 우수성을 검증하기 위하여 기존 공법과의 성능 비교를 시행하고자 한다. 기존 공법과의 구조 성능 비교는 HBS 슬래브의 실험적 연구를 통하여 휨성능 및 전단에 대한 구조 성능과 PC보와 HBS 슬래브의 접합 성능을 검토하였으며, 이론적 방법을 통하여 기존 공법과 비교를 수행하고자 한다.

• 한국소음진동공학회논문집
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• 제20권7호
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• pp.651-657
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• 2010

Previous experimental results performed by many researchers for a couple of decades in South Korea have shown that an absorbing sheet inserted in a conventional floating slab system for thermal insulation or vibration absorption may amplify the vibration of the slab system at specific frequency ranges depending on the material properties of the sheet. The amplified vibration, consequently, results in the heavy weight floor impact noise exceeding the sound level limit for an apartment house, 50 dB. In this study, the amplification mechanism is examined through numerical analysis and a new slab system is proposed to reduce the amplification and control the noise. The new slab system consists of studs connecting the base slab and upper concrete finishing yielding the dramatically increased stiffness of the slab. The numerical simulation is performed to investigate the effect of the slab system with studs on the vibration and noise control. The results show that the performance of the slab is sensitive to the number and location of studs, and the heavy weight floor impact noise can be reduced up to 6~7 dB compared to the conventional slab system at the optimal stud location.