• Magazine of the Korea Concrete Institute
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• v.5 no.3
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• pp.187-194
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• 1993

본 논문에서는 유리섬유의 적층수, 유리섬유의 배향각도에 대한 유리섬유 강화 플라스틱(Glass Fiber Reinforced Plastics ; GFRP)의 인장거동 변화를 고찰하고, 이들의 상관관계를 규명하기 위하여 일련의 GFRP 시험체에 대하여 인장실험을 수행하였다. 시험체는 폭12.5mm, 길이 60mm크기로 일정하게 제작하였으며, 시험체에 대하여 인장실험을 수행하였다. 시험체 제작시 유리섬유로 적층수는 14, 22, 30층, 유리섬유의 배향각도는 0$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$로 하였다. 인장실험시 각 시험체의 파괴양상, 극한하중 및 하중변화에 대한 인장변형율을 조사하였고, 이들 결과를 토대로 유리섬유의 적층수와 배향각도에 따른 GFRP의 극한하중, 응력-변형율 선도 및 탄성계수 등을 비교 분석하였다. 한편 본 논문에서는 유리섬유의 적층수, 직경 변화에 따른 GFRP관의 파괴거동을 고찰하기 위하여 4점 재하법에 의한 GFRP관의 휨파괴실험을 수행하였다. 실험에 사용된 시험체는 길이 1200mm로 하였으며, 유리섬유의 적층수를 30, 35, 40층, 관의 직경을 50, 100, 150mm로 하였다. 파괴실험시 각 시험체의 하중변화에 대한 휨 변형율, 중앙점 처짐량 및 항복하중을 측정하였고, 이들 결과를 토대로 유리섬유으 적층수와 관의 직경에 따라 GFRP관의 항복하중 및 파괴에너지를 비교 분석 하였으며, 항복시 파괴에너지를 추정할 수 있는 제안식을 유도하였다.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.35-35
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• 2011

CFT가 갖는 다양한 구조적 이점으로 인해, 축력이 지배적인 기둥 구조물에만 주로 적용되던 CFT 요소가 점차 거더에 적용되어 가고 있다. 그러나, 현재 CFT 요소에 대한 설계 기준은 축력이 지배적인 보-기둥 구조물에 대한 것으로 제한되어 있으며, 휨이 지배적인 보 구조물에 대한 현행 설계 기준의 적용성을 검토해야 할 필요가 있다. 현행 설계기준에서 제시하고 있는 CFT 요소의 극한 강도 평가방법은 소성응력분배법 및 변형률적합법으로 구분되어지며, 각 방법을 이용한 극한 강도의 평가결과를 기존 연구자들의 CFT 요소 휨 실험결과와 비교 분석하였다. 휨 강성 평가에 대한 타당성을 검증하기 위해 AISC에서 제시하는 휨 강성 평가식을 기존 실험 연구와 비교 검토하였으며, 아울러 압축력에 따라 휨 강성을 보정할 수 있도록 수정된 Roeder et al.의 제안식을 함께 검토하였다. 검토 결과, 강도 평가에 있어서는 설계 기준에서 제안하는 두 방법 모두 CFT 거더의 휨 강도를 적절히 평가할 수 있었으며, 강성 평가에 있어서는 설계 기준의 제안식이 휨 초기 강성을 적절히 평가하는 반면 사용 단계에서의 휨 강성은 Roeder et al.의 수정된 강성 평가식에 의해 적절히 평가할 수 있음을 확인하였다.

• Journal of the Korean Wood Science and Technology
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• v.23 no.4
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• pp.10-17
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• 1995

본 연구는 화염에 노출된 목재 부재의 거동에 관련된 자료를 얻기 위해 수행되었다. 목재 보에 대한 현행 내화 모델들은 외곽부 섬유의 MOE나 휨강도의 감소, 그리고 화염노출의 계속으로 인한 단면의 감소 등에 기초하고 있다. 하지만 이런 모델들은 정확한 거동 예측이 힘들다. 따라서 목재 보의 거동을 정확히 예측하기 위해 본 연구에서는 변형 단면을 이용한 내화거동 모델을 개발하고자 하였다. 이 변형 단면모델을 개발하기 위하여 온도분포 온도와 목재의 물리적 성질간의 상관관계를 이용하였다. 본 연구를 통해 온도와 목재의 휨성질간의 정확한 관계가 제공되기만 한다면 본 방법이 화염에 노출된 목재 보의 변형을 잘 예측할 수 있음을 알 수 있었다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.3
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• pp.213-220
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• 2005

Recently, a concern to verify the displacement capacity of shear wall has been arised to produce suitable data for the performance based design. In this paper, a process is presented to evaluate the displacement capacity of shear wall. The displacement of shear wall is expressed as the superposition of shear and flexural deformation. Variable crack angle truss model with a modification and sectional analysis method are used in calculating shear and flexural displacement, respectively. In addition, the effect of axial force and the contribution of vertical and horizontal reinforcements in wall are considered in the analysis. The accuracy of proposed method is evaluated by the comparison calculation results with previous test results. From the comparison, it was shown that the hysteretic behavior of shear wall could be well predicted by using the process. In the case with flange wall, however, the method overestimates the contribution of flange wall for strength and stiffness and underestimates for displacement capacity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.11-20
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• 2013

In this paper, the quantitative damage index for reinforced concrete (RC) columns with non-seismic details were presented. They are necessary to carry out the postearthquake safety evaluation of RC buildings under 5 stories without seismic details. The static cyclic test of the RC frame sub-assemblage that was an one span and actual-sized was first conducted. The specimen collapsed by the shear failure after flexural yielding of a column, lots of cracks on the surfaces of columns and beam-column joints and the cover concrete splitting at the bottom of columns occurred. The damage levels of these kinds of columns with non-seismic details were classified to five based on the load-displacement relationship by the test result. The residual story drift ratios and crack widths were then adapted as the quantitative index to evaluate the damage limit states because those values were comparatively easy to measure right after earthquakes. The highest one among the residual story drift ratios under the similar maximum story drift ratio decided on the residual story drift ratio of each damage limit state. On the other hand, the lowest and average ones among the respective residual shear and flexural widths under the similar maximum story drift ratio decided on the residual shear and flexural widths of each damage limit state, respectively. These values for each damage limit state resulted in being smaller than those by the international damage evaluation guidelines that are for seismically designed members under the same deformations.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1085-1088
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• 2008

Splice of reinforcement is inevitable in reinforced concrete structures and, generally, lap splices are used. Lap length for tension splice is determined from development length in tension. The development length is calculated from an experimental model which was based on data of tests on anchorage and splice. Longitudinal reinforcements in flexural members are deformed and, therefore, prying action happens in spliced reinforcements unlike anchored reinforcements. The prying action induces tensile stress in cover concrete and this tensile stress plays the same role to a circumferential tensile stress caused by bond. Because splitting failure is assumed to occur when the summation of tensile stresses caused by the prying action and the bond is equal to the tensile strength of the concrete, the prying action reduces the bond strength of spliced reinforcements. A theoretical model for the prying action is developed and effects of the prying action on the bond strength are assessed. The tensile stress by the prying action is proportional to tensile strength and modulus of elasticity of reinforcements. In addition, the tensile stress is inversely proportional to spacing of reinforcements. Consequently, longer splice length is required for spliced reinforcements with small spacing in flexible members.

• Computational Structural Engineering
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• v.3 no.4
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• pp.113-122
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• 1990

An analytical simulation of the flexural behavior of SFRC beam has been illustrated. Curvature distributions and crack opening in critical region were taken into account. Compressive and tensile constitutive models which express post-peak behavior of SFRC with stress-crack opening relationships were incorporated in simulating nonlinear flexural behavior of the beam. The model was able to predict test results with reasonable accuracy. Behavior of the critical section and effects of different factors m the flexural behavior of SFRC beam were investigated. Simple observation and statistical approach have been made in selecting most influential parameters in flexural behavior of SFRC.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.749-758
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• 2000

This study presents a governing equations of bending behavior of sandwich plates with thick metal, polymer composite facings. Based on zig-zag models for through thickness deformations, the transverse shear deformation of composite facings is included. All edges of plate are assumed to be simply supported. Results of the bending analysis under lateral loads are presented for the influence of various lay up sequences of antisymmetric angle-ply laminated facings. The accuracy of the approach is ascertained by comparing solutions from the sandwich plates theory with composite facings to the laminated plates theory. Since the present analysis considers the bending stiffness of the core and also the transverse shear deformations of the laminated facings, the proposed method showed higher than that calculated according to the general laminated plates theory. The information presented might be useful to design sandwich plates structure with metal, polymer matrix composite facings.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.3
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• pp.103-110
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• 2018

The long-term flexural behavior of reinforced concrete (RC) beams strengthened with an iron based-shape memory alloys (Fe-SMAs) by a near-surface mounted (NSM) method was evaluated. The pre-strained values of 2% and 4% and introduced prestressing force by an activation of a shape memory effect of the Fe-SMA strengthening material were considered as experimental variables. Deflections at the center of the RC beams were measured for six months after the 1 tonf concrete weight was loaded on the beam. Experimental results show that the deflections decreased because of the increased flexural stiffness of beams strengthened with the Fe-SMA strips. On the contrary, with increased pre-strained values, the deflection increased due to stiffness reduction of the strengthening material. It was confirmed that the specimens incorporating the prestressed force showed the deflection reduction of about 30%, compared to the ones without the prestressed force.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.101-112
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• 2011

This paper shows a study carried out on the estimation of nominal flexural strength for CFRP-plated RC beams failed by intermediate crack debonding. A strength reduction factor is proposed to consider the effect of the intermediate crack debonding for the determination of nominal flexural strength. The proposed factor is derived from experimental data and utilizes the ratio of effective stress(or strain) in the CFRP plate to its ultimate strength(or strain) which is called effective strain model. An analytical equation for the estimation of the nominal flexural strength is formulated as a function of strength reduction factor. The validity, accuracy and efficiency of the proposed factor are established by comparing the analytical results with the experimental data, and the major design codes, as well as a number of factors given by researchers. The analytical results presented in this paper indicate that the proposed factor can effectively estimate the flexural nominal strength of CFRP-plated reinforced concrete beams failed by intermediate crack debonding.