• Steel and Composite Structures
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• 제17권3호
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• pp.287-303
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• 2014

8 steel reinforced concrete (SRC) columns with the encased steel ratio of 13.12% and 15.04% respectively were tested under the test axial load ratio of 0.33-0.80 and the low-frequency cyclic lateral loading. The cross sectional area of composite columns was $500mm{\times}500mm$. The mechanical properties, failure modes and deformabilities were studied. All the specimens produced flexure failure subject to combined axial force, bending moment and shear. Force-displacement hysteretic curves, strain curves of encased steels and rebars were obtained. The interaction behavior of encased steel and concrete were verified. The hysteretic curves of columns were plump in shapes. Hysteresis loops were almost coincident under the same levels of lateral loading, and bearing capacities did not change much, which indicated that the columns had good energy-dissipation performance and seismic capacity. Based on the equilibrium equation, the suggested practical calculation method could accurately predict the flexural strength of SRC columns with cross-shaped section encased steel. The obtained M-N curves of SRC columns can be used as references for further studies.

• 콘크리트학회논문집
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• 제21권3호
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• pp.311-318
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• 2009

본 연구는 고축력과 반복횡력을 받는 초고강도 RC 띠철근 기둥의 실험적 연구를 수행하였다. 콘크리트 압축강도 100 MPa 초고강도 RC 띠철근 기둥의 횡보강근의 양을 제안하는 것이다. 철근콘크리트 구조물의 실제 보를 스터브로 이상화한 1/2개 층의 기둥 실험체를 계획하여 1/3 크기의 19개 실험체를 제작하였다. 주요 변수는 축력비, 횡보강근의 형상 및 체적비로 하였다. 실험 결과, 띠철근 기둥의 강도와 연성은 횡보강근의 형상과 체적비의 영향을 받는 것으로 나타났으나, 무엇보다 축력비에 가장 큰 영향을 받는 것으로 나타나 초고강도 콘크리트 기둥의 횡보강근량 설계를 위해서는 축력비에 따른 적절한 횡보강근의 형상으로 보다 합리적인 설계가 이루어져야 할 것으로 판단된다. 또한, 초고강도 철근콘크리트 기둥의 충분한 연성확보를 위하여 최소한의 변위연성능력 4이상을 확보할 수 있도록 설계식을 제안하였다. 따라서 이는 축력비와 함께 횡보강근의 형상, 간격 및 주근의 개수 등을 고려한 유효횡구속감소계수 (${\lambda}^c$)를 적용한 것이므로 횡보강근량 산정시 보다 합리적일 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.430-433
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• 2006

The reinforced concrete column confined by square steel tubes(RCST) is a reinforced column (RC) confined by thin steel tubes which cover over the full length of the column but terminates 15mm from the column's ends. The steel tube is in uniaxial tension stress state and won't buckle when the column sustains axial load. This will highly increase the bearing capacity and ductility of the columns. The hysteretic behavior of four square RCST columns and one square RC column were experimentally studied under constant axial load and lateral cyclic load. The wide-to-thickness (D/t) ratio of RCST columns employed in this research is 75. The main variables of the experiment were axial load ratio and compressive strength of the concrete. Based on the findings in this research, RCST columns exhibits high lateral strength, ductility, and energy dissipation ability.

• Earthquakes and Structures
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• 제16권1호
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• pp.69-82
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• 2019

As the residual displacement and/or drift demands are commonly used for seismic assessment of buildings, the estimation of these values play a very critical role through earthquake design philosophy. The residual displacement estimation of fixed base structures has been the topic of numerous researches up to now, but the effect of soil flexibility is almost always omitted. In this study, residual displacement demands are investigated for SDOF systems with period range of 0.1-3.0 s for near-field and far-field ground motions for both fixed and interacting cases. The elastoplastic model is used to represent non-degrading structures. Based on time history analyses, a new simple yet effective equation is proposed for residual displacement demand of any system whether fixed base or interacting as a function of structural period, lateral strength ratio and spectral displacement.

• Earthquakes and Structures
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• 제26권6호
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• pp.489-499
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• 2024

Infill masonry walls are vulnerable to lateral loads, including seismic, wind, and concentrated push loads. Various strengthening metal fittings have been proposed to improve lateral load resistance, particularly against seismic loads. This study introduces the use of post-compressed wedges as a novel reinforcement method for infill masonry walls to enhance lateral load resistance. The resistance of the infill masonry wall against lateral-concentrated push loads was assessed using an out-of-plane push-over test on specimens sized 2,300×2,410×190 mm³. The presence or absence of wedges and wedge spacing were set as variables. The push-over test results showed that both the unreinforced specimen and the specimen reinforced with 300 mm spaced wedges toppled, while the specimen reinforced with 100 mm spaced wedges remained upright. Peak loads were measured to be 0.74, 29.77, and 5.88 kN for unreinforced specimens and specimens reinforced with 100 mm and 300 mm spaced wedges, respectively. Notably, a tighter reinforcement spacing yielded a similar strength, as expected, which was attributed to the increased friction force between the masonry wall and steel frame. The W-series specimens exhibited a trend comparable to that of the displacement ductility ratio. Overall, the findings validate that post-compressed wedges improve the out-of-plane strength of infill masonry walls.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.507-512
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• 1998

An experimental investigation was conducted to examine the behavior of high strength R/C columns subjected to reversed cyclic and axial loads and to find the relationship between amounts of lateral reinforcement and axial loads ratios. The test parameters of column specimens were the compressive strength of concrete($f`_c$=250, 320, 460, $517kg/\textrm{cm}^2), $ the yield strength of longitudinal steel($f_y$=3700, $5254kg/\textrm{cm}^2), $ axial load ratio(0.3, 0.5, 0.6$f`_cA_g$). The results indicated that axial load can significantly affect and alter the behavior of HS R/C column under inelastic cyclic loadings. Also we found that the relationship between amounts of lateral reinforcement and axial load ratios was $\rho$ =(0.37η+0.15)f`/f.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.565-570
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• 2000

The objective of this paper is to analyse the high-strength concrete columns subjected to reversed cyclic and axial loads by using nonlinear analysis model and compare the experimental results with analysis. The analytical parameters are the compressive strength of concrete, spacing of lateral reinforcement and lateral reinforcement ratio. In this study, the proposed analytical model takes ito account the influence of confined concrete, tension stiffening and strain hardening of steel. The high-strength concrete columns are used to model fiber section element. The analysis results are shown comparatively good prediction on envelope curve, accumulative dissipated energy, deformability and so on.

• 한국구조물진단유지관리공학회 논문집
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• 제11권3호
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• pp.95-104
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• 2007

편심 하중을 받는 철근 콘크리트 기둥에서 띠철근과 콘크리트 강도의 영향을 파악하기 위하여 콘크리트 압축강도, 띠철근 배근간격 및 형상, 편심비를 주요 변수로 하여 단면 $200mm{\times}200mm$의 시험체 24개를 실험하였다. 이러한 연구를 통하여 콘크리트 기둥은 편심거리비, 띠철근 배근간격, 띠철근 배근형태 등에 관계없이 콘크리트 강도가 증가할수록 취성적으로 거동하였고, 편심거리비가 증가할수록 띠철근 배근에 의한 연성 증가 효과는 감소함을 알 수 있었다. 띠철근 배근간격이 100mm에서 30mm로 줄어들 경우, 최대 내력은 10~20% 증가하였으며, 최대 내력 이후에도 보다 연성적으로 거동하였다. 그러므로 고강도 콘크리트 기둥에서 적당한 연성과 강도를 확보하기 위해서는 일반강도 콘크리트에 비하여 더 많은 띠철근 체적비와 밀실한 띠철근 배근이 필요하였으며, 띠철근 배근 간격만을 제한하는 현재의 대한건축학회 내진 기준은 고강도 콘크리트 사용 시 띠철근의 배근 효과와 부재 연성 확보 측면에서 불안전하였으며, 띠철근을 콘크리트 강도와 연계하는 새로운 내진 기준이 필요한 것으로 나타났다.

• KCI Concrete Journal
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• 제13권1호
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• pp.69-78
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• 2001

The inelastic behavior of a reinforced concrete columns is influenced by a number of factors : 1) level of axial load, 2) tie spacing, 3) volumetric ratio of lateral steel, 4) concrete strength, 5) distribution of longitudinal steel, 6) strength of lateral steel, 7) cover thickness, 8) configuration of lateral steel, 9) strain gradient, 10) strain rate, 11) the effectively confined concrete core area, and 12) amount of longitudinal steel. A new constitutive model of a confined concrete is suggested in order to investigate the nonlinear behavior of the reinforced concrete columns under concentric loading. The developed constitutive model for the confined concrete takes into account the effects of effectively confined area as well as the horizontal and longitudinal distributions of the confining pressures. None of the existing models incorporated these two main effects at the same time. A total of different six constitutive models for the behavior of the confined concrete under concentric compression were compared with the sixty-one test results reported by different researchers. The superiority of the developed model in its accuracy is demonstrated by evaluating the error function, which compares the weighted averages for the sum of squared relative differences in peak compressive strength and corresponding strain, stress at strain equal to 0.015, and total area under stress-strain curve up to strain equal to 0.015.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.479-482
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• 2005

The concrete box girder members are extensively used as a superstructure in bridge construction. The load carrying capacity of concrete box girders in lateral direction is generally influenced by the sizes of haunch and web. The internal upper decks are restrained by the webs and exhibit strength enhancement due to the development of aching action. The current codes do not have generally consider the arching action of deck slab in the design because of complexity of the behavior. However, there are significant benefits in utilizing the effects of arching action in the design of concrete members. The main objective of this paper is to propose a rational method to predict the ultimate load of deck slab by considering various haunch sizes and web restraint effect of concrete box girder bridges. To this end, a comprehensive experimental program has been set up and seven large-scale concrete box girders have been tested. A transverse analysis model of concrete box girders with haunches is proposed and compared with test data. The results of present study indicate that the ultimate strength is significantly affected by haunch dimension. The increase of strength due to concrete arcing action is reduced with an increase of prestressing steel ratio in laterally prestressed concrete box girders and increases with a larger haunch dimension. The proposed theory allows more realistic prediction of lateral ultimate strength for rational design of actual concrete box girder bridges.