• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.18-21
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• 2003

The effect of interface bonding strength on the recovery force of SMA wire reinforced polymer matrix composites was investigated by pullout test. Firstly, the recovery forces and transformation temperatures of various prestrained SMA wires were measured and 5% prestrained SMA wires were prepared for the reinforcements of composites. EPDM incorporated with 20vol% silicon carbide particles(SiCp) of 6, 12, $60{mutextrm{m}}$ size were used as matrix. Pullout test results showed that the interface bonding strength increased when the SiCp size decreased due to the increase of elastic modulus of matrix. Cyclic test of composites was performed through control of DC current at the constant displacement mode. The abrupt decrease of recovery force during cycle test at high current was occurred by thermal degradation of matrix. This was in good agreement with temperature related in the thermal degradation of matrix. The hysteresis of recovery force with respect to the temperature was compared between wire and composite and the hysterisis of composites was smaller than the wire due to less thermal conduction.

• Structural Engineering and Mechanics
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• 제26권3호
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• pp.231-250
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• 2007

The influence of masonry infills with eccentric openings on the seismic performance of reinforced concrete (r/c) frames that were designed in accordance with current code provisions are investigated. Eight 1/3-scale, single-story, single-bay frame specimens were tested under cyclic horizontal loading up to a drift level of 4%. In all examined cases the shear strength of columns was higher than the cracking shear strength of solid infill. The parameters investigated include the shape and the location of the opening. Assessment of the behavior of the frames is also attempted, based on the observed failure modes, strength, stiffness, ductility, energy dissipation capacity and degradation from cycling loading. Based on these results there can be deduced that masonry infills with eccentrically located openings has been proven to be beneficial to the seismic capacity of the bare r/c frames in terms of strength, stiffness, ductility and energy dissipation. The location of the opening must be as near to the edge of the infill as possible in order to provide an improvement in the performance of the infilled frame.

• 한국강구조학회 논문집
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• 제20권4호
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• pp.483-491
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• 2008

1994년 노스리지 지진 이후, 철골모멘트골조 강축방향 접합부의 내진성능 평가에 관한 연구가 국내 외에서 활발하게 진행되어온 반면, 국내 철골모멘트골조 내진설계 및 시공의 실무에 관행적으로 적용되고 있는 철골모멘트골조 약축방향 접합부의 내진성능 평가 연구가 국내는 물론 국외에서도 그 사례를 찾아보기 힘든 상황이다. 따라서 본 연구에서는 국내에서 내진성능 확보 여부가 확인되지 않은 상태에서 내진설계 실무에서 가장 많이 사용되고 있는 브라켓 형식 및 WUF-B 형식의 접합상세를 갖는 철골모멘트골조 약축접합부의 실물대(Full scale) 실험체를 제작 및 실험하여 이와 같은 형상의 접합부에 대한 내진성능을 평가하여 향후 이와 같은 형상을 갖는 철골모멘트골조 약축접합부의 설계를 위한 기초자료를 제공하는 것을 목적으로 한다. 이러한 목적을 달성하기 위하여, 현장조사 및 설계도서등의 기존 자료를 통해 총 2개의 실험체를 제작하여 내진성능을 평가 실험연구를 수행하였다. 실험결과로부터 최대내력 비교, 하중-변위 이력 및 응력도 등에 대한 거동을 비교 분석 하였다. 실험결과 층간변위각 5%의 BR-W 실험체가 층간변위각 4%를 갖는 WUF-B 실험체에 비해 우수한 구조적 거동을 보여주었으며, 설계 내력을 상회하는 내력을 보유하고 있는 것을 알 수 있었다. 또한 브라켓 형식의 실험체는 최대내력 도달 이후 완만한 강도 저하를 나타내었으나, WUF-B 형식의 실험체는 최대내력 도달 이후 급격한 하중 저하를 나타내며 취성적인 거동을 보였다.

• Earthquakes and Structures
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• 제20권4호
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• pp.431-444
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• 2021

T-shaped column is usually used as side column in buildings, which is one of the weak members in structural system. This paper presented a quasi-static cyclic loading experiment of six specimens of reinforced concrete (RC) T-shaped columns under compression-flexure-shear-torsion combined loadings to investigate the effect in the ratio of torsion to moment (T/M) and axial compression ratio (n) and height-thickness ratio of flange plate (φ) on their seismic performance. Based on the test results, the failure characteristics, hysteretic curves, ductility, energy dissipation, stiffness degradation and strength degradation were analyzed. The results show that the failure characteristics of RC T-shaped columns mainly depend on the ratio of torsion to moment, which can be divided into bending failure, bending-torsion failure and shear-torsion failure. With the increase of T/M ratio, the torsion ductility coefficient increased, and in a suitable range, the torsion and horizontal displacement ductility coefficient of RC T-shaped columns could be effectively improved with the increase of axial compression ratio and the decrease of height-thickness ratio of flange plate. Besides, the energy dissipation capacity of the specimens mainly depended on the bending and shear energy dissipation capacity. On the other hand, the increase of axial compression ratio and the ratio of torsion to moment could accelerate the torsional and bending stiffness degradation of RC T-shaped columns. Moreover, the degradation coefficient of torsion strength was between 0.80 and 0.98, and that of bending strength was between 0.75 and 1.00.

• Steel and Composite Structures
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• 제48권5호
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• pp.565-582
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• 2023

The present research reports the application of engineered cementitious composites (ECC) as an alternative to conventional concrete to improve the seismic behavior of short columns. Experimental and finite element investigation was conducted by testing five reinforced engineered cementitious composite (RECC) concrete columns (half-scale specimens) and one control reinforced concrete (RC) specimen for different shear-span and transverse reinforcement ratios under cyclic lateral loads. RECC specimens with higher shear-span and transverse reinforcement ratios demonstrated a significant effect on the column lateral load behavior by improving ductility (>5), energy dissipation capacity (1.2 to 4.1 times RC specimen), gradual strength degradation (ultimate drift >3.4%), and altering the failure mode. The self-confinement effect of ECC fibers maintained the integrity in the post-peak region and reserved the transmission of stress through fibers without noticeable degradation in strength. Finite element modeling of RECC specimens under monotonic incremental loads was carried out by adopting simplified constitutive material models. It was apprehended that the model simulated the global response (strength and stiffness) and damage crack patterns reasonably well.

• 한국세라믹학회지
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• 제41권1호
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• pp.69-75
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• 2004

인공치아용 3Y-TZP와 (Y,Nb)-TZP/$Al_2O_3$ 복합체를 유사 구강분위기인 인공타액 하에서 500-3000N의 하중 조건으로 $10^6$ 횟수까지 헤르찌안 반복하중 피로특성을 조사하였다. 500N의 하중에서 $5{\times}10^5$까지 반복피로 실험결과, 강도 저하 및 균열 현상은 관찰되지 않았다. 피로특성은 SY-TZP가 (T,Nb)-TZP/$Al_2O_3$ 복합체보다 상전이에 의한 응역회복 때문에 우수하였다. 하중값이 증가함에 따라 링 균열에서 방사상 균열로 전이되었을 때 급격한 강도 저하 현상이 발생하였다. 강도 저하 현상은 유사 구강 분위기하에서 반복 하중 접촉 시 발생한 균열을 통해 침투한 인공타액의 화학적 침식으로 더욱 가속화 되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.179-184
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• 2001

The objective of this study is to clarify the seismic capacity and the characteristics in the hysteretic behavior of RC structures with nonseismic detailing. To do this, an exterior beam-column subassemblage was selected from a 10-story RC building and 6 1/3-scale specimens were manufactured with 3 variables; ⑴ with and without slab, ⑵ upward and downward direction of anchorage for the bottom bar in beams, and ⑶ with and without hoop bars in the joint region. The test results have shown that ⑴ the existence of slab increased the strength in positive and negative moment, 25% and 62%, respectively; ⑵ the Korean practice of anchorage (downward and 25 $d_{b}$ anchorage length) caused the 8% reduction of strength and the early strength degradation when compared with the case of seismic details; and ⑶ the existence of hoop bars in the joint region does not show significant difference because the size of column is much larger than that of beam.m.

• 한국지진공학회논문집
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• 제28권2호
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• pp.77-83
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• 2024

The design shear strength equations of RC shear walls have been developed based on their performance under in-plane (IP) loads, thereby failing to account for the potential performance degradation of shear strength when subjected to simultaneous out-of-plane (OOP) loading. Most of the previous experimental studies on RC walls have been conducted in one direction under quasi-static conditions, and due to the difficulty in experimental planning, there is a lack of research on cyclic loading and results under multi-axial loading conditions. During an earthquake, shear walls may yield earlier than their design strength or fail unexpectedly when subjected to multi-directional forces, deviating from their intended failure mode. In this paper, nonlinear analysis in finite element models was performed based on the results of cyclic loading experiments on reinforced concrete shear walls of auxiliary buildings. To investigate the reduction trend in IP shear capacity concerning the OOP load ratio, parametric analysis was conducted using the shear wall FEM. The analysis results showed that as the magnitude of the OOP load increased, the IP strength decreased, with a more significant effect observed as the size of the opening increased. Thus, the necessity to incorporate this strength reduction as a factor for the OOP load effect in the wall design strength equation should be discussed by performing various parametric studies.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 가을 학술발표회논문집
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• pp.182-189
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• 2000

This paper presents a simple and reliable constitutive model for predicting the nonlinear response of reinforced concrete subjected to general membrane loadings. Based on the concept of equivalent uniaxial strain, constitutive relations of concrete are presented in the axes of orthotropy. The behavior of cracked concrete is described by a system of orthogonal cracks, which follows the principal strain directions and rotates according to the loading history. Simple hysteretic rules defining the cyclic stress-strain curves of concrete and steel are used. In addition, the stiffness and strength degradation of cracked concrete is included in the formulation. Correlation studies between analytical results and experimental values from idealized shear panel tests are conducted with the objective to establish the validity of the proposed model.

• Steel and Composite Structures
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• 제25권4호
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• pp.505-521
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• 2017

The steel plate shear wall with beam-only connected infill plate (SSW-BO) is an innovative lateral load resisting system consisting of infill plates connected to surrounding beams and separated from the main columns. In this research, the effects of perforation diameter as well as slenderness ratios of infill plates on the hysteresis behavior of SSW-BO systems were studied experimentally. Experimental testing is performed on eight one-sixth scaled one-story SSW-BO specimens with two plate thicknesses and four different circular opening ratios at the center of the panels under fully reversed cyclic quasi-static loading in compliance with the SAC test protocol. Strength, stiffness, ductility and energy absorption were evaluated based on the hysteresis loops. It is found that the systems exhibited stable hysteretic behavior during testing until significant damage in the connection of infill plates to surrounding beams at large drifts. It is also seen that pinching occurred in the hysteresis loops, since the hinge type connections were used as boundaries at four corners of surrounding frames. The strength and initial stiffness degradation of the perforated specimens containing opening ratio of 0.36 compared to the solid one is in the range of 20% to 30% and 40% to 50%, respectively.