• 한국강구조학회 논문집
• /
• 제29권6호
• /
• pp.411-422
• /
• 2017

본 연구에서는 콘크리트피복 원형충전강관 기둥을 적용한 합성구조 접합부의 거동특성과 내진성능을 평가하기 위하여, 기둥-플랜지 접합부에 대한 인장실험과 보-기둥 접합부에 대한 반복하중 실험을 수행하였다. 기둥-플랜지 인장실험은 피복콘크리트의 유무와 플랜지 폭, 인장철근 보강을 변수로 하여 5개의 실험체에 대하여 하중재하능력과 파괴모드를 분석하였다. 실험결과, 접합부에서의 플랜지 단부 폭을 200mm에서 350mm로 증가시킬 경우 연결부의 강도 및 강성이 각각 1.61배와 1.56배가 증가했고, 인장철근을 보강할 경우 추가적으로 강성과 강도가 각각 1.35배와 1.92배 증가했다. 접합부 반복하중 실험에서는 접합 상세를 변수로 3개의 외부접합부 실험체를 구성했다. 접합부 보강상세로는 인장철근 보강과 강관의 두께, 수직강판 보강을 고려하였다. 모든 접합부 실험체는 보에서 뚜렷한 휨항복이 발생하였으며 접합부의 손상은 제한적이었다. 특히, 강재보가 강관에 직접 용접되는 경우 보의 웨브를 통해서도 하중이 전달되기 때문에, 플랜지 인장실험 결과보다 보수적인 설계가 가능하며, 접합부 강관 두께를 증가시키거나 수직강판으로 보강한 경우에는 추가적으로 패널존의 전단내력이 증가하는 것으로 나타났다.

• Smart Structures and Systems
• /
• 제5권4호
• /
• pp.443-455
• /
• 2009

The use of fiber reinforced polymer (FRP) reinforcement in concrete structures has been on the rise due to its advantages over conventional steel reinforcement such as corrosion. Reinforcing steel corrosion has been the primary cause of deterioration of reinforced concrete (RC) structures, resulting in tremendous annual repair costs. One application of FRP reinforcement to be further explored is its use in RC frames. Nonetheless, due to FRP's inherently elastic behavior, FRP-reinforced (FRP-RC) members exhibit low ductility and energy dissipation as well as different damage mechanisms. Furthermore, current design standards for FRP-RC structures do not address seismic design in which the beam-column joint is a key issue. During an earthquake, the safety of beam-column joints is essential to the whole structure integrity. Thus, research is needed to gain better understanding of the behavior of FRP-RC structures and their damage mechanisms under seismic loading. In this study, two full-scale beam-column joint specimens reinforced with steel and GFRP configurations were tested under quasi-static loading. The control steel-reinforced specimen was detailed according to current design code provisions. The GFRP-RC specimen was detailed in a similar scheme. The damage in the two specimens is characterized to compare their performance under simulated seismic loading.

• Earthquakes and Structures
• /
• 제11권5호
• /
• pp.905-924
• /
• 2016

Several two-dimensional analytical beam column joint models with varying complexities have been proposed in quantifying joint flexibility during seismic vulnerability assessment of non-ductile reinforced concrete (RC) frames. Notable models are the single component rotational spring element and the super element joint model that can effectively capture the governing inelastic mechanisms under severe ground motions. Even though both models have been extensively calibrated and verified using quasi-static test of joint sub-assemblages, a comparative study of the inelastic seismic responses under nonlinear time history analysis (NTHA) of RC frames has not been thoroughly evaluated. This study employs three hypothetical case study RC frames subjected to increasing ground motion intensities to study their inherent variations. Results indicate that the super element joint model overestimates the transient drift ratio at the first story and becomes highly un-conservative by under-predicting the drift ratios at the roof level when compared to the single-component model and the conventional rigid joint assumption. In addition, between these story levels, a decline in the drift ratios is observed as the story level increased. However, from this limited study, there is no consistent evidence to suggest that care should be taken in selecting either a single or multi component joint model for seismic risk assessment of buildings when a global demand measure such as maximum inter-storey drift is employed in the seismic assessment framework.

• Structural Engineering and Mechanics
• /
• 제73권6호
• /
• pp.613-620
• /
• 2020

The research study is focuses on a form of all-bolted joint with the external ring stiffening plate in the prefabricated steel structure. The components are bolted at site after being fabricated in the factory. Six specimens were tested under cyclic loading, and the effects of column axial compression ratio, concrete-filled column, beam flange sub plate, beam web angle cleats, and spliced column on the failure mode, hysteretic behavior and ductility of the joints were analyzed. The results shown that the proposed all-bolted joint with external ring stiffening plate performed high bearing capability, stable inflexibility degradation, high ductility and plump hysteretic curve. The primary failure modes were bucking at beam end, cracking at the variable section of the external ring stiffening plate, and finally welds fracturing between external ring stiffening plate and column wall. The bearing capability of the joints reduced with the axial compression ratio increased. The use of concrete-filled steel tube column can increase the bearing capability of joints. The existence of the beam flange sub plate, and beam web angle cleat improves the energy dissipation, ductility, bearing capacity and original rigidity of the joint, but also increase the stress concentration at the variable section of the external reinforcing ring plate. The proposed joints with spliced column also performed desirable integrity, large bearing capacity, initial stiffness and energy dissipation capacity for engineering application by reasonable design.

• 한국구조물진단유지관리공학회 논문집
• /
• 제25권6호
• /
• pp.68-75
• /
• 2021

본 연구에서는 반복하중을 받는 외부 보-기둥 접합부에 정착된 57mm 확대머리철근의 정착성능을 평가하였다. 총 4개의 외부 보-기둥 접합부 실험체를 계획하였으며, 콘크리트 압축강도, 측면피복두께, 횡보강근비 및 파괴유형을 주요 실험 변수로 설정하여 정착성능평가를 수행하였다. 성능평가 결과, 접합부에 정착된 대구경 확대머리철근의 정착성능에 가장 큰 영향을 주는 요소는 측면피복두께 및 횡보강근으로 나타났으며, 외부 보-기둥 접합부에 정착된 57mm 대구경 확대머리철근은 반복하중하에서도 충분한 정착성능이 발현되는 것을 확인할 수 있었다.

• Earthquakes and Structures
• /
• 제3권1호
• /
• pp.37-57
• /
• 2012

The behavior of beam-column joints in moment resisting frame structures is susceptible to damage caused by seismic effects due to poor performance of the joints. A good number of researches were carried out to understand the complex mechanism of RC joints considered in current seismic design codes. The traditional construction detailing of transverse reinforcement has resulted in serious joint failures during earthquakes. This paper introduces a new design philosophy involving the use of additional diagonal bars within the joint particularly suitable for low to medium seismic effects in earthquake zones. In this study, ten full-scale interior beam-column specimens were constructed with various additional reinforcement details and configurations. The results of the experiment showed that adding additional bars is a promising approach in reinforced concrete structures where earthquakes are eminent. In terms of overall cracking observation during the test, the specimens with additional bars (diagonal and straight) compared with the ones without them showed fewer cracks in the column. Furthermore, concrete confinement is certainly an important design measure as recommended by most international codes.

• Earthquakes and Structures
• /
• 제14권6호
• /
• pp.525-535
• /
• 2018

This study presents a new beam-column model comprising material nonlinearity and joint flexibility to predict the nonlinear response of reinforced concrete structures. The nonlinear behavior of connections has an outstanding role on the nonlinear response of reinforced concrete structures. In presented research, the joint flexibility is considered applying a rotational spring at each end of the member. To derive the moment-rotation behavior of beam-column connections, the relative rotations produced by the relative slip of flexural reinforcement in the joint and the flexural cracking of the beam end are taken into consideration. Furthermore, the considered spread plasticity model, unlike the previous models that have been developed based on the linear moment distribution subjected to lateral loads includes both lateral and gravity load effects, simultaneously. To confirm the accuracy of the proposed methodology, a simply-supported test beam and three reinforced concrete frames are considered. Pushover and nonlinear dynamic analysis of three numerical examples are performed. In these examples the nonlinear behavior of connections and the material nonlinearity using the proposed methodology and also linear flexibility model with different number of elements for each member and fiber based distributed plasticity model with different number of integration points are simulated. Comparing the results of the proposed methodology with those of the aforementioned models describes that suggested model that only uses one element for each member can appropriately estimate the nonlinear behavior of reinforced concrete structures.

• Earthquakes and Structures
• /
• 제9권1호
• /
• pp.233-256
• /
• 2015

This paper presents an experimental study to assess the effectiveness of using ferrocement to strengthen deficient beam-column joints. Ferrocement is proposed to protect the joint region through replacing concrete cover. Six exterior beam-column joints, including two control specimens and four strengthened specimens, are prepared and tested under constant axial load and quasi-static cyclic loading. Two levels of axial load on column (0.2fc'Ag and 0.4fc'Ag) and two types of skeletal reinforcements in ferrocement (grid reinforcements and diagonal reinforcements) are considered as test variables. Experimental results have indicated that ferrocement as a composite material can enhance the seismic performance of deficient beam-column joints in terms of peak horizontal load, energy dissipation, stiffness and joint shear strength. Shear distortions within the joints are significantly reduced for the strengthened specimens. High axial load (0.4fc'Ag) has a detrimental effect on peak horizontal load for both control and ferrocement-strengthened specimens. Specimens strengthened by ferrocement with two types of skeletal reinforcements perform similarly. Finally, a method is proposed to predict shear strength of beam-column joints strengthened by ferrocement.

• 콘크리트학회논문집
• /
• 제15권3호
• /
• pp.369-376
• /
• 2003

프리캐스트 보-기둥 연결부에는 기둥 주근과 보의 정착철근, 연결부를 위한 띠철근 등으로 매우 복잡한 배근상태로 철근 배근과 콘크리트의 타설 및 다짐이 용이하지 않다. 특히 보의 갈고리는 띠철근 또는 주근과의 마주침이 흔히 발생하는 철근으로, 외곽기둥의 경우 충분한 정착길이를 확보하기가 더욱 난해할 때가 있다. 본 연구에서는 헤드철근을 적용한 보-기둥 연결부를 위하여 두 개의 프리캐스트 기둥과 하나의 프리캐스트 보를 연결한 4개의 실험체를 제작하여, 보-기둥접합부와 기둥-기둥접합부에 대한 반복하중실험으로 강도와 그 이력거동을 평가하여 보았다. 실험 결과 강주 약보 실험체들은 갈고리철근과 유사한 거동을 보였다. 국내에서 주로 적용되는 스플라이스 기둥 접합은 강주 약보의 기둥에서는 충분한 내력을 발휘하였다.

• Structural Engineering and Mechanics
• /
• 제54권3호
• /
• pp.521-543
• /
• 2015

Depending on the damage type as well as the level of damage observed after the earthquake, certain measures should be taken for the damaged buildings. In this study, structural repairing of two different types of damaged RC beam-column assembly by carbon fiber-reinforced polymer sheets is investigated in detail as a member repairing technique. Two types of 1:1 scale test specimens, which represent the exterior RC beam-column connection taken from inflection points of the frame, are utilized. The first specimen is designed according to the current Turkish Earthquake Code, whereas the second one represents a deficient RC beam-column assembly. Both of the specimens were subjected to cyclic quasistatic loading in the laboratory and different levels of structural damage were observed. The first specimen displayed a ductile response with the damage concentrated in the beam. However, in the second specimen, the beam-column joint was severely damaged while the rest of the members did not attain their capacities. Depending on the damage type of the specimens, the damaged members were repaired by CFRP wrapping with different configurations. After testing the repaired specimens, it is found that former capacities of the damaged members were mostly recovered by the application of CFRPs on the damaged members.