• 한국생산제조학회지
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• 제21권5호
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• pp.741-746
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• 2012

The increase of energetic efficiency in plane bearing is getting more important in the transfer mechanism of semi-conductor and display panel manufacturing processes. To accomplish this objective, the technique of surface texturing on bearing surface has recently emerged as one of the most effective candidates. In this study, the effects of various pattern parameters on two bearing performance indices(load carrying capacity and effective friction coefficient) are investigated through a semi-analytic method, i.e., the 2-dimensional Reynolds equation incorporated into the finite difference scheme. Here, cavitation effect is also taken into account by employing an appropriate numerical scheme. In this study, the patterns in the textured surface are composed of a series of semi-spheres or semi-ellipsoids in shape. The effects of their size and number density on the performance indices are examined through the performance of various numerical experiments. Also, the effects of the anisotropy of the semi-ellipsoidal pattern on the bearing's lubrication characteristics are investigated and discussed.

• 동력기계공학회지
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• 제17권2호
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• pp.38-45
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• 2013

In this study, for carrying out the spray and combustion experiment using a Common Rail Direct Injection(CRDI) system, the controller was fabricated to drive a high speed camera, a injector and a laser beam sequentially at a low cost. CB280 module of one-chip micro processer was used for the controller. In order to confirm responsibility and utility of the controller, the current drive performance, the spray behavior and the injection rate were tested and analyzed under various experimental conditions. As this research results, we found that the fabricated controller was able to control the devices for the spray experiment precisely with the input value in program and it had the dynamic load responsibility and repetition. Also, we found that the injection rates of our experimental results were higher than those of others at the same injection pressure and the controller connected with the laser system and the data acquisition system had validity for carrying out the spray visualization experiment.

• Advances in concrete construction
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• 제9권5호
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• pp.437-448
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• 2020

In high rise buildings that utilize precast large panel system for construction, the shear wall provides strength and stiffness during earthquakes. The performance of a wall panel system depends mainly on the type of connection used to transfer the forces from one wall element to another wall element. This paper presents an experimental investigation on different types of construction detailing of the precast wall to wall vertical connections under reverse cyclic loading. One of the commonly used connections in India to connect wall to wall panel is the loop bar connection. Hence for this study, three types of wet connections and one type of dry connection namely: Staggered loop bar connection, Equally spaced loop bar connection, U-Hook connection, and Channel connection respectively were used to connect the precast walls. One third scale model of the wall was used for this study. The main objective of the experimental work is to evaluate the performance of the wall to wall connections in terms of hysteretic behaviour, ultimate load carrying capacity, energy dissipation capacity, stiffness degradation, ductility, viscous damping ratio, and crack pattern. All the connections exhibited similar load carrying capacity. The U-Hook connection exhibited higher ductility and energy dissipation when compared to the other three connections.

• 대한건축학회논문집:구조계
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• 제34권12호
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• pp.35-40
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• 2018

In this study, experimental research was carried out to evaluate the seismic performance of reinforced concrete exterior beam-column joint regions using hybrid retrofitting with AFRP sheets and embedded CFRP reinforcements in existing reinforced concrete building. Therefore it was constructed and tested three specimens retrofitting the beam-column joint regions using such retrofitting materials. Specimens, designed by retrofitting the beam-column joint regions of existing reinforced concrete structure, were showed the stable failure mode and increase of load-carrying capacity due to the effect of crack control at the times of initial loading and confinement of retrofitting materials during testing. Specimens RBCJ-SRA3 designed by the retrofitting of AFRP sheets and embedded CFRP reinforcements in reinforced exterior beam-column joint regions were increased its maximum load carrying capacity by 1.86 times and its energy dissipation capacity by 1.65 times in comparison with standard specimen RBCJ for a displacement ductility of 5.

• Steel and Composite Structures
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• 제37권6호
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• pp.741-759
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• 2020

Steel plate-concrete composite slabs provide attractive features, such as more effective loading transfer, and more cost-effective stay-in-place forms, thereby enabling engineers to design more high-performance light structures. Although significant studies in the literatures have been directed toward designing and implementing the steel plate-concrete composite beams, there are limited data available for understanding of the composite slabs. To fill this gap, nine the composite slabs with different variables in this study were tested to unveil the impacts of the critical factors on the ultimate strength behavior. The key information of the findings included sample failure modes, crack pattern, and ultimate strength behavior of the composite slabs under either four-point or three-point loading. Test results showed that the failure modes varied from delamination to shear failures under different design factors. Particularly, the shear stud spacing and thicknesses of the concrete slabs significantly affected their ultimate load-carrying capacities. Moreover, an analytical model of the composite slabs was derived for determining their ultimate load-carrying capacity and was well verified by the experimental data. Further extensive parametric study using the proposed analytical methods was conducted for a more comprehensive investigation of those critical factors in their performance. These findings are expected to help engineers to better understand the structural behavior of the steel plate-concrete composite slabs and to ensure reliability of design and performance throughout their service life.

• 콘크리트학회논문집
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• 제21권6호
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• pp.697-703
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• 2009

이 연구에서는 강섬유 혼입률과 주인장 철근의 정착 방법을 변수로 한 섬유보강 고강도 콘크리트 내민받침을 제작하고 구조실험을 실시하였다. 강섬유의 혼입, 강섬유 혼입률의 증가에 따라 고강도 콘크리트 내민받침의 내하력, 강성, 연성은 증가하는 것으로 나타났고, 최대 균열폭은 감소하였다. 또한, 횡방향 철근에 용접하여 주인장 타이 철근을 정착한 내민받침 보다 헤디드 바를 주인장 타이 철근으로 사용한 내민받침이 더 높은 내하력, 강성, 연성을 보였다. 따라서, 헤디드 바를 주인장 타이 철근으로 사용하고, 강섬유를 혼입함으로써 내민받침의 내하력, 내구성, 시공성 등을 향상시킬 수 있을 것으로 판단된다. 실험 결과를 설계기준의 규준식 및 여러 연구자들이 제안한 예측모델과 비교한 결과, Fattuhi가 제안한 트러스 모델은 섬유 보강 고강도 콘크리트 내민받침의 강도를 잘 예측하는 것으로 나타났다.

• Smart Structures and Systems
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• 제3권3호
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• pp.281-298
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• 2007

The load carrying capacity of a bridge needs to be properly assessed to operate the bridge safely and maintain it efficiently. For the evaluation of load carrying capacity considering the current state of a bridge, static and quasi-static loading tests with weight-controlled heavy trucks have been conventionally utilized. In these tests, the deflection (or strain) of the structural members loaded by the controlled vehicles are measured and analyzed. Using the measured data, deflection (or strain) correction factor and impact correction factor are calculated. These correction factors are used in the enhancement of the load carrying capacity of a bridge, reflecting the real state of a bridge. However, full or partial control of the traffic during the tests and difficulties during the installment of displacement transducers or strain gauges may cause not only inconvenience to the traffic but also the increase of the logistics cost and time. To overcome these difficulties, an alternative method is proposed using an excited response part of full measured ambient acceleration data by ordinary traffic on a bridge without traffic control. Based on the modal properties extracted from the ambient vibration data, the initial finite element (FE) model of a bridge can be updated to represent the current real state of a bridge. Using the updated FE model, the deflection of a bridge akin to the real value can be easily obtained without measuring the real deflection. Impact factors are obtained from pseudo-deflection, which is obtained by double-integration of the acceleration data with removal of the linear components on the acceleration data. For validation, a series of tests were carried out on a steel plategirder bridge of an expressway in Korea in four different seasons, and the evaluated load carrying capacities of the bridge by the proposed method are compared with the result obtained by the conventional load test method.

• Wind and Structures
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• 제32권4호
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• pp.283-292
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• 2021

Performance-based seismic design (PBSD) is currently used for retrofitting of older buildings and the design of new buildings. Whereas, application of performance-based design for wind load is still under development. The tendency has been in the codes to increase wind hazard based on recent recorded events. Since tall buildings are highly susceptible to wind load, necessity for developing a framework for performance-based wind design (PBWD) has intensified. Only a few guidelines such as ASCE (2019) provide information on using PBWD as an alternative for code prescriptive wind design. Though wind hazards, performance objectives, analysis techniques, and acceptance criteria are explained, no recommendations are provided for several aspects like how to select a proper level of wind hazard for each target performance criterion. This paper is an attempt to explain current design philosophy for wind and seismic loads and inherent connection between the components of PBSD for development of a framework for PBWD of tall buildings. Recognizing this connection, a framework for PBWD based on limits set for serviceability and strength is also proposed. Also, the potential for carrying out PBWD in line with ASCE 7-16 is investigated and proposed in this paper.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.41-49
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• 2007

More diversified and strengthened safety regulations require higher safety vehicle with less weight. The structural foam can play a role for restraining section distortion of main body members undergoing bending collapse at vehicle crash. In this study, using structural foam modeling technology, validated in previous work, the bending collapse characteristics were evaluated for two types of circular and actual vehicle body frame sections. With changing the foam filling method, outer panel thickness and section shape, load carrying capability and absorbed energy were observed. The results indicate valuable design strategy for effectively elevating bending collapse performance of body members with foam filled.

• Computers and Concrete
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• 제17권1호
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• pp.67-86
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• 2016

Strengthening as well as correcting unsightly deflections of reinforced concrete (RC) beam may be accomplished by retrofitting. An innovative way to do this retrofitting that is proposed in this study utilizes turnbuckle to apply external post-tensioning. This Turnbuckle External Post-Tensioning (T-EPT) was experimentally proven to improve the serviceability and load carrying capacity of reinforced concrete beams. The T-EPT system comprises a braced steel frame and a turnbuckle mechanism to provide the prestressing force. To further develop the T-EPT, this research aims to develop a numerical scheme to analyze the structural performance of reinforced concrete beams with this kind of retrofitting. The fiber method analysis was used as the numerical scheme. The fiber method is a simplified finite element method that is used in this study to predict the elastic and inelastic behavior of a reinforced concrete beam. With this, parametric study was conducted so that the effective setup of doing the T-EPT retrofitting may be determined. Different T-EPT configurations were investigated and their effectiveness evaluated. Overall, the T-EPT was effective in improving the serviceability condition and load carrying capacity of reinforced concrete beam.