• Steel and Composite Structures
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• 제21권2호
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• pp.443-460
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• 2016

In this paper, the efficiency and effectiveness of two strengthening methods for upgrading behavior of the two external weak reinforced concrete (RC) beam-column joints were experimentally investigated under cyclic loading. Since two deficient external RC joints with reduced beam height and low strength concrete were strengthened using one-way steel prop and curbs with and without steel revival sheets on the beam. The cyclic performance of these strengthened specimens were compared with two another control external RC beam-column joints, one the standard RC joint that had not two mentioned deficiencies and another had both. Therefore, four half-scale RC joints were tested under cyclic loading.The experimental results showed that these innovative strengthening methods (RC joint with revival sheet specially) surmounted the deficiencies of weak RC joints and upgraded their performance and bearing capacity, stiffness degradation, energy absorption, up to those of standard RC joint. Also, results exhibited that the prop at joint acted as a fuse element due to adding steel revival sheets on the RC beam and showed better behavior than that of the specimen without steel revival sheets. In other words by stiffening of beam, the prop collected all damages due to cyclic loading at itself and acted as the first line of defense and prevented from sever damages at RC joint.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.470-473
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• 2006

Past experiences from recent earthquakes indicate that shear failures of beam-column connections were one of the main reasons causing significant damages and collapses of RC structures subjected to earthquake loadings. Many researchers and engineers have conducted to propose an effective way to improve the joint shear strength of RC connections. This paper presents an analytical model for the RC exterior beam-column joints strengthened with CFRP sheets. In the analytical model, the effect of shear behavior of the RC beam-column joint, bond slip of the beam longitudinal reinforcements and CFRP sheets were considered and incorporated into the non-linear structural analysis program. Final analytical results were compared with those from the experiment of eight exterior RC beam-column specimens. The analytical results showed that the developed connection model is very useful to investigate the hysteretic joint behavior and overall load-displacement response of the RC beam-column connections strengthened with CFRP sheets.

• Steel and Composite Structures
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• 제20권2호
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• pp.337-355
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• 2016

Steel coupling beam in reinforced concrete (RC) coupled shear wall system is a proper substitute for deep concrete coupling beam. Previous studies have shown that RC coupled walls with steel or concrete coupling beam designed with strength-based design approach, may not guarantee a ductile behavior of a coupled shear wall system. Therefore, seismic performance evaluation of RC coupled shear wall with steel or concrete coupling beam designed based on a strength-based design approach is essential. In this paper first, buildings with 7, 14 and 21 stories containing RC coupled shear wall system with concrete and steel coupling beams were designed with strength-based design approach, then performance level of these buildings were evaluated under two spectrum; Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE). The performance level of LS and CP of all buildings were satisfied under DBE and MCE respectively. In spite of the steel coupling beam, concrete coupling beam in RC coupled shear wall acts like a fuse under strong ground motion.

• Computers and Concrete
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• 제10권1호
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• pp.59-78
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• 2012

Although the effect of corrosion of reinforcing bar on the shear behavior of the reinforced concrete (RC) beam had been simulated by tests of the beam with unbonded, half-exposed or whole-exposed tensile steel reinforcements as well as defective stirrup anchorages, theoretical methods to accurately predict remaining capacity of this kind of RC beams, especially shear capacity, are still lacking. Considering the possible position of the critical inclined crack, the actual pattern of strains in the concrete body within the partial length and the proposed compatibility condition of deformations of the RC beam, shear strength of the RC beam with unbonded or exposed tensile steel reinforcements and/or defective stirrup anchorages is predicted. Comparison between the model's predictions with the experimental results published in the literature shows the practicability of the proposed model. Influence of the length of unbonded or exposed tensile steel reinforcements and the percentage of stirrups lacked end anchorages on the shear strength of the RC beam is discussed. It is concluded that, the shear strength of the RC beam with unbonded or exposed tensile steel reinforcements and/or defective stirrup anchorages is greatly influenced by the length of unbonded or exposed tensile steel reinforcements and the percentage of stirrups lacked end anchorages, this influence can be adverse, insignificant or even favourable, dependent on the given parameters of the corresponding normal bonded RC beam.

• Steel and Composite Structures
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• 제22권2호
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• pp.387-398
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• 2016

In order to evaluate the effects of U shape ultra high performance concrete (UHPC) permanent form on the behaviors of Reinforced Concrete (RC) beam, a full scale RC composite beam is designed and tested with U shape UHPC permanent form and a reference RC beam with same parameters is tested simultaneously for comparison. The effects of the permanent form on the failure mode, cracking strength, ultimate capacity and deformation are studied. Test results shows that the contributions of the U shape UHPC permanent form to the flexural cracking behaviors of RC beam are significant. This study may provide a reference for the design of sustainable RC beam with high durable UHPC permanent form.

• 한국구조물진단유지관리공학회 논문집
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• 제23권3호
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• pp.127-135
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• 2019

본 논문은 기존 RC 보강방법인 철골프레임 적용방법의 단점을 보완하고자, 접합철물을 최소화하고 팽창형 모르타르를 사용하여 H형강 프레임을 기존 RC 골조에 보강하고자 하였다. 철골프레임 적용 유.무를 변수로 RC 골조에 대한 반복가력실험을 실시하여 내진성능을 평가하였다. 철골프레임을 적용한 RC 골조의 최대내력이 기존 RC 골조에 비해 약 1.4배 향상되었으며, 등가점성감쇠비 평가결과 또한 평균 2.4% 향상되어 에너지 소산능력이 개선되었다. 유한요소해석결과 해당 실험결과가 신뢰성을 가질 수 있는 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
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• pp.851-856
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• 1998

In recent years, glassfibers have been used for strengthening in RC structure because of low material cost and easy repairing work. The purpose of this study is to experimentally and analytically investigate the effect of glassfibers for enhancing the capacity of RC structure. The result shows that yield and ultimate strength of RC beam with glassfibers are increased by approximate 13% and 26%, comparing with those for RC beam without glassfibers. It has been observed from the test that fatigue behaviors of RC beam with glassfibers have been significantly and large improved comparing with those for RC beam without glassfibers.

• Structural Engineering and Mechanics
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• 제84권5호
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• pp.619-632
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• 2022

Reinforced concrete (RC) structures may be subjected to sudden dynamic impact loads such as explosions occurring for different reasons, the collision of masses driven by rockfall, flood, landslide, and avalanche effect structural members, the crash of vehicles to the highway and seaway structures. Many analytical, numerical, and experimental studies focused on the behavior of RC structural elements such as columns, beams, and slabs under sudden dynamic impact loads. However, there is no comprehensive study on the behavior of the RC column-beam connections under the effect of sudden dynamic impact loads. For this purpose, an experimental study was performed to investigate the behavior of RC column-beam connections under the effect of low-velocity impact loads. Sixteen RC beam-column connections with a scale of 1/3 were manufactured and tested under impact load using the drop-weight test setup. The concrete compressive strength, shear reinforcement spacing in the beam, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, and displacements measured from the test specimens were recorded in experiments. Besides, shear and bending crack widths were measured. The effect of experimental variables on the impact behavior of RC beam-column connections has been determined and interpreted in detail. Besides, a finite element model has been established for verification and comparison of the experimental results by using ABAQUS software. It has been demonstrated that concrete strength, shear reinforcement ratio, and impact energy significantly affect the impact behavior of RC column-beam connections.

• 한국강구조학회 논문집
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• 제14권3호
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• pp.463-470
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• 2002

TEC-BEAM System은 구조용 CT형강, PC 콘크리트 그리고 현장타설콘크리트 슬래브로 이루어진 합성보이다. 이 시스템은 단순보에 대한 휨 및 전단실험을 수행하였고 우수한 거동을 보였다. 그러나 현장적용을 위해서는 TEC-BEAM과 RC 기둥 강접합 상세개발이 필요하다. 이 접합부는 TEC-BEAM의 하부에 발생하는 힘을 기둥에 전달하기 위한 매캐니즘을 발생해야만 한다. 그래서 TEC-BEAM의 단면이 증대되어 TEC-BEAM 플랜지 하부로 철근이 배근되는 접합부를 개발하였다. 본 논문에서는 제안된 시스템의 구조적 성능 평가를 위해 2개의 실험체에 대하여 실험하였다. 실험변수는 철근의 정착길이 즉, 증대된 단면의 길이이며, 실험결과 제안된 시스템은 우수한 접합부를 구조 성능을 가지고 있음을 확인할 수 있다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.106-109
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• 2006

It has been shown that many reinforced concrete(RC) structures designed without seismic details have experienced brittle shear failures in the beam-column joint area and may result in large permanent deformations and structural collapse. In this study, experimental investigations for RC beam-column joints strengthened with the carbon fiber-reinforced polymer(CFRP) under cyclic loadings were presented. The use of CFRP in the joint was varied to determine the effective way of improving the structural performances of RC joints. Ten RC beam-column joints were designed and tested with cyclic loadings. The experimental results showed that the use of CFRP in RC joints would be very effective solutions to improve the seismic performances of the non-seismic RC joints. All of the non-seismic design specimens strengthened with CFRP sheets showed the significant increase of strength and ductility.