• 한국소음진동공학회논문집
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• 제18권8호
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• pp.856-863
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• 2008

High-rise apartments of shear wall system are governed by flexural behavior like a cantilever beam. Installation of the damper-brace system in a structure governed by flexural behavior is not suitable. Because of relatively high lateral stiffness of the shear wall, a load is not concentrate on the brace and the brace cannot perform a role as a damping device. In this paper, a friction damper applying flexibility of shear wall is proposed in order to reduce the deformation of a structure. To evaluate performance of the proposed friction damper, nonlinear time history analysis is executed by SeismoStruct analysis program and MVLEM(multi vertical linear element model) be used for simulating flexural behavior of the shear wall. It is found that control performance of the proposed friction damper is superior to one of a coupled wall with rigid beam. In conclusion, this study verified that the optimal control performance of the proposed friction damper is equal to 45 % of the maximum shear force inducing in middle-floor beam with rigid beam.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.757-762
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• 2002

This study focused on the investigation of durability of latex modified concrete in the points of surface scaling resistance as cement types variated and latex content variated such as 5%, 10%, 15%, and 20%. An increasing the amount of latex produced concrete with increased flexural strength, but with slightly lower compressive strength. The increase in flexural strength might be attributed to the latex films between the hydrated cement and aggregates, and the decrease in compressive strength to the flexibility of the latex component named by Butadiene. The surface scaling resistance test was used to evaluate the durability of latex-modified concretes and rapid setting latex-modified concretes. The surface scaling resistance of LMC was quite good comparing to conventional concrete. Further, surface scaling resistance of RSLMC was improved with increasing the latex content.

• Structural Engineering and Mechanics
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• 제27권4호
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• pp.501-521
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• 2007

This study presents a model to better understand the shear behavior of reinforced concrete walls subjected to lateral load. The scope of the study is limited to squat walls with height to length ratios not exceeding two, deformed in a double-curvature shape. This study is based on limited knowledge of the shear behavior of low-rise shear walls subjected to double-curvature bending. In this study, the wall ultimate strength is defined as the smaller of flexural and shear strengths. The flexural strength is calculated using a strength-of-material analysis, and the shear strength is predicted according to the softened strut-and-tie model. The corresponding lateral deflection of the walls is estimated by superposition of its flexibility sources of bending, shear and slip. The calculated results of the proposed procedure correlate reasonably well with previously reported experimental results.

• Computers and Concrete
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• 제17권1호
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• pp.29-51
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• 2016

Tension-stiffening is the contribution of concrete between the cracks to carry tensile stresses after cracking in Reinforced Concrete (RC) members. In this paper, a tension-stiffening model has been proposed for computationally efficient nonlinear analysis of RC flexural members subjected to service load. The proposed model has been embedded in a typical cracked span length beam element. The element is visualized to consist of at the most five zones (cracked or uncracked). Closed form expressions for flexibility and stiffness coefficients and end displacements have been obtained for the cracked span length beam element. Further, for use in everyday design, a hybrid analytical-numerical procedure has been developed for nonlinear analysis of RC flexural members using the proposed tension-stiffening model. The procedure yields deflections as well as redistributed bending moments. The proposed model (and developed procedure) has been validated by the comparison with experimental results reported elsewhere and also by comparison with the Finite Element Method (FEM) results. The procedure would lead to drastic reduction in computational time in case of large RC structures.

• Earthquakes and Structures
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• 제7권5호
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• pp.797-815
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• 2014

This research aimed to investigate retrofitting methods for damaged RC columns with SRF (Super Reinforced with Flexibility) and aramid composites and their impacts on the seismic responses. In the first stage, two original (undamaged) column specimens, designed to have a flexural- or shear-controlled failure mechanism, were tested under quasi-static lateral cyclic and constant axial loads to failure. Afterwards, the damaged column specimens were retrofitted, utilizing SRF composites and aramid rods for the flexural-controlled specimen and only SRF composites for the shear-controlled specimen. In the second stage, the retrofitted column specimens were tested again under the same conditions as the first stage. The hysteretic responses such as strength, ductility and energy dissipation were discussed and compared to clarify the specific effects of each retrofitting material on the seismic performances. Generally, SRF composites contributed greatly to the ductility of the specimens, especially for the shear-controlled specimen before retrofitting, in which twice the deformation capacity was obtained in the retrofitted specimen. The shear-controlled specimen also experienced a flexural failure mechanism after retrofitting. In addition, aramid rods moderately fortified the specimen in terms of the maximum shear strength. The maximum strength of the aramid-retrofitted specimen was 12% higher than the specimen without aramid rods. In addition, an analytical modeling of the undamaged specimens was conducted using Response-2000 and Zeus Nonlinear in order to further validate the experimental results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.130-135
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• 2007

The mechanical characteristics of three types of core with two-dimensional isotropic patterns-triangular, hexagonal and starcell-were studied in applications to sandwich structures. The Young's modulus and shear modulus were calculated for the three core types in the direction normal to the faces. The compressive buckling strength and shear buckling strength were calculated by modeling each cell wall of the core as a plate under compressive or shear load. To verify this model, tests were conducted on scaled specimens to measures the compressive buckling strength of each core. The bending flexibilities of the three cores were also studied. Compliances for the three cores were measured using biaxial flexural tests. The three isotropic core patterns exhibited distinct characteristics. In the direction normal to the faces, all three cores had the same stiffness. However, the starcell core exhibited high flexibility compared to the other cores, indicating potential for application to curved sandwich structures.

• 소음진동
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• 제9권5호
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• pp.1029-1035
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• 1999

This paper relates to the flexural vibration analysis of slender spindle systems with multiple thin disks, supported by the ball bearings by means of the finite element method. Each system component is analytically modeled taking into account its flexibility and also the centrifugal effect especially for the disk. In order to show the rapid convergence rate and accuracy of the proposed approach, an experimental set-up is built to be versatile. In two distinct cases, its natural modes are numerically computed using only a small number of total element meshes as the shaft rotational speed is varied, and verified through experimental frequency response function obtained by the impact test.

• 한국항공우주학회지
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• 제32권8호
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• pp.82-90
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• 2004

등방성의 2차원 단위 셀 형상을 지닌 세 종류의 심재-삼각형 심재, 육각형 심재와 starcell 심재-에 대하여 샌드위치 구조물 내에서의 응용과 관련된 기계적 특성을 연구하였다. 세 종류의 심재에 대하여 축 방향 Young 계수, 전단 계수를 계산하여 비교하고, 심재의 셀 벽을 압축 하중과 전단 하중을 받고 있는 판재로 가정하여 축 방향 압축 좌굴 강도와 전단 좌굴 강도를 산출하였다. 심재의 유연성을 나타내는 평면탄성계수를 비교하고 쌍축 굴곡 실험 (biaxial flexural test)을 실시하여 유연성을 측정하였다. 세 가지 심재 모두 축 방향으로 같은 강성을 가지고 있었으나, 삼각형 심재는 다른 두 종류의 심재에 비하여 낮은 강도를 나타내었고, starcell 심재는 다른 심재들에 비해 월등히 높은 유연성 을 나타내었다. 이러한 유연성은 starcell 심재가 곡면에 적용되는 샌드위치 구조물의 심재로서 응용될 수 있음을 보여주었다.

• 접착 및 계면
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• 제23권4호
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• pp.137-143
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• 2022

본 연구에서는 신발 및 의류용 접착제로 접착력과 굴곡성이 우수한 폴리우레탄 아크릴레이트 수지를 합성하기 위하여 폴리에스테르 폴리올인 poly(tetramethylene adiphate glycol) (PTAd)와 폴리에테르 폴리올인 poly(tetramethylene ether glycol) (PTMG)를 4,4'-methylene diphenyl diisocyanate (MDI), isophorone diisocyanate (IPDI), 1,4-butandiol (1,4-BD), 2-ydroxyethyl methacrylate (2-HEMA), dibutyl amine (DBA)와 함께 사용하여 폴리우레탄 아크릴레이트를 합성하였으며, 폴리올을 병용한 폴리우레탄 아크릴레이트의 열적·기계적 특성, 접착력 및 굴곡성을 검토하였다. 합성된 폴리우레탄 아크릴레이트의 유리전이온도는 -70~-40 ℃ 범위로 확인되었으며, PTAd 함량이 증가함에 따라 유리전이온도, 분해온도, 인장강도, 접착력 및 내열성이 증가하였고 반대로 신장률, 내수성 및 굴곡성은 감소되었다. 합성된 폴리우레탄 아크릴레이트는 PTAd와 PTMG 비율이 5:5일 때 높은 접착력과 굴곡성을 나타내었다.

• KIEAE Journal
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• 제11권1호
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• pp.9-14
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• 2011

Currently, the multi-residential apartments used in Korea are mostly bearing wall apartments which don't satisfy consumers for the lack of architectural plan flexibility. And due to remodelling-incompatible, bearing wall apartments have to be reconstructed. It is, thus, necessary to develop multi-residential apartments utilizing composite beam that can replace the conventional bearing wall-type apartment buildings. Composite beams proposed in this paper ensure modification of space and quality control, while the floor heights are maintained at the same floor height as in bearing wall structures. This study analyzes the experimental behavior of composite beams with proper combination of structural steel, reinforced concrete, and precast concrete. By comparing with the theoretical analysis and experimental results, the accuracy of flexural moment capacity and neutral axis was evaluated. The experiments were performed by two simply-supported specimens using loading and unloading. When the analysis results were compared with the experimental results, the flexural moment capacity of the composite beam was shown with an error of approximately -0.5 to 0.1% at the maximum load limit state.