• Steel and Composite Structures
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• 제10권5호
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• pp.385-414
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• 2010

In current European Standard EN 1993, the moment-rotation characteristics of beam-to-column joints made from steel with a yield stress > 460MPa are obtained from elastic design procedures. The strength of the joint basic components, such as the column web subject to local transverse compression, is thus limited to the yield resistance rather than the plastic resistance. With the recent developments of higher strength steel grades, the need for these restrictions should be revisited. However, as the strength of the steel is increased, the buckling characteristics become more significant and thus instability phenomena may govern the design. This paper summarizes a comprehensive set of finite element parametric studies pertaining to the strength behaviour of high-strength steel unstiffened I-columns in transverse compression. The paper outlines the implementation and validation of a three-dimensional finite element model and presents the relevant numerical test results. The finite element predictions are evaluated against the strength values anticipated by the EN 1993 for conventional steel columns and recommendations are made for revising the specifications.

• 콘크리트학회지
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• 제7권4호
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• pp.169-179
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• 1995

본 논문은 고강도 콘크리트($f'_c=700kg/cm^2$)를 사용한 보_기둥 접합부의 소성힌지 확산을 위하여 중간철근을 수직으로 앵커한 수직앵커형 중간철근으로 보 단부를 보강함으로써 보_기둥 접합부에 발생하는 소성힌지를 보 내측으로 1.0d 만큼 확산시키고자 하는 것이다. 실험의 주 변수로는 중간철근의 유물 및 앵커여부로 설정하여 중간철근의 보강형태에 따른 부재의 역학적 거동을 규명하도록 하였다. 실험결과로부터 보 단부의 1.0d부분을 수직앵커형 중간철근으로 보강하면 소성힌지를 1.0d 부분으로 확산할 수 있었으며, 에너지 분산능력도 ACI318-89에 따라 설계한 관례적인 실험체에 비하여 약 1.6배정도 향상되었다.

• Steel and Composite Structures
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• 제25권5호
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• pp.603-615
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• 2017

This experimental research presents the seismic performance of steel reinforced high-strength concrete (SRHC) short columns. Eleven SRHC column specimens were tested under simulated earthquake loading conditions, including six short column specimens and five normal column specimens. The parameters studied included the axial load level, stirrup details and shear span ratio. The failure modes, critical region length, energy dissipation capacity and deformation capacity, stiffness and strength degradation and shear displacement of SRHC short columns were analyzed in detail. The effects of the parameters on seismic performance were discussed. The test results showed that SRHC short columns exhibited shear-flexure failure characteristics. The critical region length of SRHC short columns could be taken as the whole column height, regardless of axial load level. In comparison to SRHC normal columns, SRHC short columns had weaker energy dissipation capacity and deformation capacity, and experienced faster stiffness degradation and strength degradation. The decrease in energy dissipation and deformation capacity due to the decreasing shear span ratio was more serious when the axial load level was higher. However, SRHC short columns confined by multiple stirrups might possess good seismic behavior with enough deformation capacity (ultimate drift ratio ${\geq}2.5%$), even though a relative large axial load ratio (= 0.38) and relative small structural steel ratio (= 3.58%) were used, and were suitable to be used in tall buildings in earthquake regions.

• Structural Engineering and Mechanics
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• 제72권3호
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• pp.367-382
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• 2019

This paper presents experimental and analytical investigations on additional fixed-end rotations resulting from the strain penetration of high-strength reinforcement in reinforced concrete (RC) beam-column connections under monotonic loading. The experimental part included the test of 18 interior beam-column connections with straight long steel bars and 24 exterior beam-column connections with hooked and headed steel bars. Rebar strains along the anchorage length were recorded at the yielding and ultimate states. Furthermore, a numerical program was developed to study the effect of strain penetration in beam-column connections. The numerical results showed good agreement with the test results. Finally, 87 simulated specimens were designed with various parameters based on the test specimens. The effect of concrete compressive strength ($f_c$), yield strength ($f_y$), diameter ($d_b$), and anchorage length ($l_{ah}$) of the reinforcement in the beam-column connection was examined through a parametric study. The results indicated that additional fixed-end rotations increased with a decrease in $f_c$ and an increase in $f_y$, $d_b$ and $l_{ah}$. Moreover, the growth rate of additional fixed-end rotations at the yielding state was faster than that at the ultimate state when high-strength steel bars were used.

• Steel and Composite Structures
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• 제7권2호
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• pp.135-160
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• 2007

Recently, CFT column has been well-studied and reported on, because a CFT column has certain superior structural properties as well as good productivity, execution efficiency, and improved rigidity over existing columns. However, CFT column still has problems clearing the capacity evaluation between its steel tube member and high-strength concrete materials. Also, research on concrete has examined numerical values for high-strength concrete filled steel square tube columns (HCFT) to explain transformation performance (M-${\phi}$) when a short-column receives equal flexure-moment from axial stress. Moment-curvature formulas are proposed for HCFT columns based on analytic assumption described in this paper. This study investigated structural properties (capacity, curvature), through a series of experiments for HCFT with key parameters, such as strength of concrete mixed design (58.8 MPa), width-thickness ratio (D/t), buckling length to sectional width ratio (Lk/D) and concrete types (Zeolite, Fly-ash, Silica-fume) under eccentric loads. A comparative analysis executed for the AISC-LRFD, AIJ and Takanori Sato, etc. Design formulas to estimate the axial load (N)-moment (M)-curvature (${\phi}$) are proposed for HCFT columns based on tests results described in this paper.

• 한국강구조학회 논문집
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• 제24권1호
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• pp.13-21
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• 2012

최근 건축구조물의 고층화 및 단면크기의 증대 때문에, 600MPa급 이상의 고강도 후판강재의 개발이 활발하다. 그러나 국내에서 연구되는 이러한 강재는 높은 설계기준강도와 높은 항복비로 인하여 사용이 제한적일 우려가 있다. 그래서 이 연구에서는 일본에서 개발된 저항복강 600MPa급 강재에 대한 기계적 성능을 기본으로 하여, 축력과 휨모멘트를 받는 beam-column의 단조재하실험결과를 이용하여, 연강처럼 건축물에 이용이 가능한지, 그 구조적 특성을 검증한다. 따라서, 이 연구에서는 현재 국내 시험생산된 유사 고강도 강재의 실용적 연구의 기초자료를 제공하고자 한다.

• 한국화재소방학회논문지
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• 제26권6호
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• pp.64-71
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• 2012

60 MPa급, 100 MPa급 고강도 철근콘크리트 기둥에 대하여 횡구속력 보강공법(와이어로프)과 내화보강공법(Fiber-Cocktail) 적용 유무 및 하중비에 따른 내화성능을 평가하기 위하여 표준화재 재하조건에 내화실험을 실시하였다. 실험결과 60 MPa급 고강도 콘크리트 기둥의 경우 와이어로프를 적용함으로써 화재시 축방향의 연성이 향상되며, 내화성능은 23 % 이상 향상되는 것으로 나타났다. 또한 와이어로프를 적용할 경우 하중은 설계하중의 70 % 수준이 적정하다고 판단된다. 100MPa급 고강도 콘크리트 기둥에 와이어로프와 Fiber-Cocktail을 적용할 경우 띠철근만을 적용한 경우보다 내화성능이 4배 이상 향상되는 것으로 나타났으며, 100MPa급 고강도 콘크리트 기둥에 내화성능을 확보하기 위해서는 하중은 설계하중의 70 % 미만으로 설정하는 것이 적정하다고 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 가을 학술발표회 논문집
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• pp.51-56
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• 1990

Six small-scale reinforced concrete beam-column joint specimens subjected to monotonic and cyclic loading were tested to investigate the effects of strength of concrete. Variables are 1)compressive strength of concrete(f' c=300, 700kg/㎠), 2)shear span to depth ratio (a/d=4.7, 2.0). The major results of this test were: 1)flexural strength of high strength concrete beam-column joint was not affected too much by the compressive strength of concrete, 2) flexural cracks emerge to inside of beam deeply for high strength concrete member.

• 한국강구조학회 논문집
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• 제13권2호
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• pp.123-131
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• 2001

본 연구의 목적은 고강도 H형강 기둥재(beam-column)의 폭두께비에 관한 기준을 조사하고 좌굴내력을 평가하여, 강구조 한계상태설계기준과 허용응력설계기준(안)과 비교함으로써, 고강도강을 사용한 기둥부재 설계시 적용된 기준식의 타당성을 검토하기 위한 것이다. 실험에 사용된 고강도강은 SM520TMC, SM570Q 등을 사용하였고, 강재의 기계적 성질과 단주의 응력-변형도 관계를 파악하기 위하여 인장시험 및 단주압축시험을 실시하였다. 또한 고강도강 기둥재의 좌굴내력을 산정하기 위하여 수치해석을 수행하였다. 수치해석에 사용된 축력-모멘트-곡률 관계는 단주압축실험에서 구해진 응력-변형도 관계를 사용하였다

• Steel and Composite Structures
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• 제44권1호
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• pp.1-15
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• 2022

The weld quality has always been an important factor affecting the development of exposed CFT column-base joint. In this paper, a new type of exposed RCFST column-base joint is proposed, in which the high strength steel bars (USD 685) are set through the column and reinforced concrete foundation without any base plate and anchor bolts. Three specimens, the varying axial force ratio (0, 0.25 and 0.5), were tested under cyclic loadings. In addition, the bending moment capacity, energy dissipation capacity and deformation capacity of column-base joints were clarified. The experimental results indicated that the axial force ratio increases the stiffness and the bending moment and improves the energy dissipation capacity of column-base joints. This is because a large axial force can limit the slip between steel tubular and infilled concrete effectively. The specimens show stable hysteresis behavior.