• Title/Summary/Keyword: 비틀림 부재

Search Result 66, Processing Time 0.028 seconds

Failure Modes of RC Beams with High Strength Reinforcement (고강도 비틀림보강철근을 사용한 철근콘크리트 보의 파괴모드)

  • Yoon, Seok-Kwang;Lee, Su-Chan;Lee, Do-Hyeong;Lee, Jung-Yoon
    • Journal of the Korea Concrete Institute
    • /
    • v.26 no.2
    • /
    • pp.143-150
    • /
    • 2014
  • To avoid abrupt torsional failure due to concrete crushing before yielding of torsional reinforcement and control the diagonal crack width, design codes specify the limitations on the yield strength of torsional reinforcement of RC members. In 2012, Korean Concrete Institute design code increased the allowable maximum yield strength of torsional reinforcement from 400 MPa to 500 MPa based on the analytical and experimental research results. Although there are many studies regarding the shear behavior of RC members with high strength stirrups, limited studies of the RC members regarding the yield strength of torsional reinforcement are available. In this study, twelve RC beams having different yield strength of torsional reinforcement and compressive strength of concrete were tested. The experimental test results indicated that the torsional failure modes of RC beams were influenced by the yield strength of torsional reinforcement and the compressive strength of concrete. The test beams with normal strength torsional reinforcement showed torsional tension failure, while the test beams with high strength torsional reinforcement greater than 480 MPa showed torsional compression failure. Therefore, additional analytical and experimental works on the RC members subjected to torsion, especially the beams with high strength torsional reinforcement, are needed to find an allowable maximum yield strength of torsional reinforcement.

Evaluation of Internal Bracing Member Forces due to Distortional Behaviors of Tub Section Steel Box Girders (U형 강박스 거더의 뒤틀림 거동에 의한 내부 수직브레이싱 부재력 평가)

  • Kim, Kyung-Sik
    • Journal of Korean Society of Steel Construction
    • /
    • v.23 no.2
    • /
    • pp.249-259
    • /
    • 2011
  • In this study, the distortional behaviors of tub-section steel girders subjected to torsional loading were analyzed, and predictor equations were developed for estimating the member forces induced in the internal bracing system installed in the steel tub girders. Torsional loadings originated either by eccentric vertical loading or girder curvature were decomposed into the pure torsional force component that does not affect the distortional box deformation, and into the distortional force component that directly induces box distortion. The axial member forces induced in the internal cross frames were formulated as a function of the magnitude of torsional loading through the analytical investigation of the interactions between the distortional force component and internal cross frames. To verify the proposed equations, three-dimensional finite element analysis (3D FEA) was conducted for the straight simple-span girder and the three-span continuous girder samples. Very good agreement was found between the member forces from the FEA and the proposed equations.

Torsional Behaviour of Concrete Filled Circular Steel Tube Column Considering Confinement Effect (구속효과를 고려한 콘크리트 충전 원형강관 기둥의 비틀림 거동)

  • Yun, Bok Hee;Lee, Eun Taik;Park, Ji Young;Jang, Kyong Ho
    • Journal of Korean Society of Steel Construction
    • /
    • v.16 no.5 s.72
    • /
    • pp.529-541
    • /
    • 2004
  • Concrete filled steel tube structures were recently used in constructing high-rise buildings due to their effectiveness. Studies on concrete filled steel tubes have been focused on the experiments of uni-axial compression and bending and eccentric compression. There were also a few studies that investigated CFT member behavior under combined compression and torsion. The behavior of a circular CFT column under combined torsion and compression was theoretically investigated, considering the confinement of steel tubes on the concrete, the softening of the concrete, and the spiral effect, which were the dominant factors that influenced compression and torsion strength. The biaxial stress effects due to diagonal cracking were also taken into account. By applying those factors to compatibility and equilibrium conditions, the basic equation was derived, and the equation could be used to incorporate the torsional behavior of the entire loading history of the CFT member.

Study on Torsional Strength of Reinforced Concrete Members (철근콘크리트 부재의 비틀림강도에 관한 연구)

  • Park, Chang-Kyu
    • Journal of the Korean Recycled Construction Resources Institute
    • /
    • v.7 no.2
    • /
    • pp.145-150
    • /
    • 2019
  • This paper proposes a model for the calculation of the ultimate torsional strength in normal-strength and high-strength concrete beams which include the concrete contribution strength and use a reasonable thickness of shear flow. The adequacy of the proposed model is evaluated by comparing the calculated torsional strength with the experimentally observed results from 104 test specimens reported in the literature. The results are also compared with the calculations of the KCI and the ACI building code equations, and those of other model which include the concrete contribution strength. The comparisons show that the ultimate torsional strengths calculated by the proposed equation and Rahal's equation are closer to the experimentally observed results than those calculated by the code equations.

A New Model for Accurate Nonlinear Analysis of Prestressed Concrete Members under Torsion (비틀림을 받는 프리스트레스트 콘크리트 부재의 새로운 비선형 해석 모델)

  • 오병환;박창규
    • Magazine of the Korea Concrete Institute
    • /
    • v.6 no.2
    • /
    • pp.159-168
    • /
    • 1994
  • The present study proposes a realistic method to analyze the prestressed concrete members subjected to torsion. For this end, this study devises a method to realistically take into account the tensile stiffness of concrete after cracking. The effects of biaxial compressive and tensile loadings on the compressive and tensile strengths of concrete are also taken into account in the present model. The comparison of the present theory with experimental data indicates that the proposed model dipicts reasonably well the actual behavior of prestressed concrete members subjected to torsion. The present model can predict not only the service load behavior, but also up to the behavior of ultimate load stages.

Experimental Study on Global Buckling of Singly Symmetric FRP Members (일축대칭 FRP 부재의 전체좌굴에 관한 실험적 연구)

  • Lee, Seungsik
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.26 no.1A
    • /
    • pp.99-106
    • /
    • 2006
  • Due to single symmetry of cross section, T-shaped members are likely to buckle in a flexural-torsional mode when they are subjected to axial compression. Therefore, the flexural-torsional buckling can be regarded as a governing mode of global buckling. An experimental program has been carried out to investigate the flexural-torsional buckling behavior of pultruded T-shaped members. Two types of pultruded members were tested in the experiment, and they were made of either E-glass/vinylester or E-glass/polyester. Lay-up and thickness of reinforcing layers, volume fractions of each constituents in layers, mechanical properties were experimentally determined. Two sets of knife edge fixure were used to simulate simple support condition for flexure and twisting, and the lateral displacements and the angle of twist were measured using three potentiometers. Every specimen buckled in a flexural-torsional mode, and most of the specimens showed post-buckling strength.

Verification of the Torsional Amplification Factor for the Seismic Design of Torsionally Imbalanced Buildings (비틀림 비정형 건물의 내진설계를 위한 우발편심 비틀림 증폭계수 검증)

  • Lee, Kwang-Ho;Jeong, Seoung-Hoon
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.14 no.6
    • /
    • pp.67-74
    • /
    • 2010
  • Because of the difference between the actual and computed eccentricity of buildings, symmetrical buildings will be affected by torsion. In provisions, accidental eccentricity is intended to cover the effect of several factors, such as unfavorable distributions of dead- and live-load masses and the rotational component of ground motion about a vertical axis. The torsional amplification factor is introduced to reduce the vulnerability of torsionally imbalanced buildings. The effect of the torsional amplification factor is observed for a symmetric rectangular building with various aspect ratios, where the seismic-force-resisting elements are positioned at a variable distance from the geometrical center in each direction. For verifying the torsional amplification factor in provisions, nonlinear reinforced concrete models with various eccentricities and aspect ratios are used in rock. The difference between the maximum displacements of the flexible edge obtained between using nonlinear static and time-history analysis is very small but the difference between the maximum torsional angles is large.

Strength and Lateral Torsional Behavior of Horizontally Curved Steel I-Girders Subjected to Equal End Moments (양단 균일 모멘트를 받는 수평곡선 I형 강재 거더의 횡-비틀림 거동 및 강도 산정 방안)

  • Lee, Keesei;Lee, Manseop;Choi, Junho;Kang, Youngjong
    • Journal of Korean Society of Steel Construction
    • /
    • v.30 no.1
    • /
    • pp.1-12
    • /
    • 2018
  • A curved member should resist bending and torsional moments simultaneously even though the primary load is usually supposed to be gravitational load. The torsional moment causes complicate stress state and also can result in early yielding of material to reduce member strength. According to analysis results, the strength of a curved member that has 45 degrees of subtended angle could decrease more than 50% compare to straight girder. Nevertheless, there have been very few of researches related with ultimate strength of curved girders. In this study, various kinds of stiffness about bending, pure torsion and warping were considered with a number of models in order to verify the main factor that affects ultimate behavior of curved girder. Lateral and rotational displacement of curved member were introduced as lateral-torsional-vertical behavior and bending-torsional moment interaction curve was derived. Finally, a strength equation for ultimate moment of horizontally curved steel I-girders subjected to equal end moments based on the interaction curves. The equation could take account of the effect of curvature, unbraced length and sectional properties.

Strength of Reinforced Concrete Members in Pure Torsion (순수(純粹)비틀림을 받는 철근(鐵筋)콘크리트 부재(部材)의 내력(耐力))

  • Shin, Hyun Mook;Kim, Eun Kyun;Kim, Seon Il
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.8 no.2
    • /
    • pp.125-133
    • /
    • 1988
  • To establish the rational design method, it is very important that predict accurately load-deformation response on reinforced concrete members. Torque-twist curves of reinforced concrete members in pure torsion were proposed recently by Collins and Hsu, etc. But, it is found that torsional strength of reinforced concrete members based on Hsu's theory is underestimated in the over-all load region except the ultimate state. In this paper, an attempt is made to present the higher-precision of torsional strength on arbitrary loading condition. For this purpose, constitutive equations are derived from which an estimate can be made of the torsional behavior of reinforced concrete members under the pure torsion. Tension stiffness of concrete in both the cracked and uncracked state have been considered. A softening effect that reduces the strength of the concrete by the diagonal cracking of concrete have been appropriately deliberated. Particularly, the experiments was done with 14 test beams to investigate the validity of theoretical analysis.

  • PDF

Minimum Torsional Reinforcement Ratio of Reinforced Concrete Members for Safe Design (안전한 설계를 위한 철근콘크리트 부재의 최소비틀림철근비)

  • Kim, KangSu;Lee, DeuckHang;Park, Min-Kook;Lee, Jung-Yoon;Ju, HyunJin
    • Journal of the Korea Concrete Institute
    • /
    • v.25 no.6
    • /
    • pp.641-648
    • /
    • 2013
  • Current design codes regulate the minimum torsional reinforcement requirement for reinforced concrete members to prevent their brittle failure. The minimum torsional reinforcement ratio specified in the current national code and ACI318-11, however, have problems in the minimum longitudinal reinforcement ratio for torsion, the equilibrium condition in space truss model, and a marginal strength, etc. Thus, in order to overcome such shortcomings, this study presents a rational equation for minimum torsional reinforcement ratio that can provide a sufficient margin of safety in design. The minimum torsional reinforcement ratio proposed in this study was compared to the test results available in literature, and it was confirmed that it gave a proper margin of safety for all specimens studied in this paper.