• 제목/요약/키워드: Negative moments

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Effective width of steel-concrete composite beams under negative moments in service stages

  • Zhu, Li;Ma, Qi;Yan, Wu-Tong;Han, Bing;Liu, Wei
    • Steel and Composite Structures
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    • 제38권4호
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    • pp.415-430
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    • 2021
  • The effective flange width was usually introduced into elementary beam theory to consider the shear lag effect in steel-concrete composite beams. Previous studies have primarily focused on the effective width under positive moments and elastic loading, whereas it is still not clear for negative moment cases in the normal service stages. To account for this problem, this paper proposed simplified formulas for the effective flange width and reinforcement stress of composite beams under negative moments in service stages. First, a 10-degree-of-freedom (DOF) fiber beam element considering the shear lag effect and interfacial slip effect was proposed, and a computational procedure was developed in the OpenSees software. The accuracy and applicability of the proposed model were verified through comparisons with experimental results. Second, a method was proposed for determining the effective width of composite beams under negative moments based on reinforcement stress. Employing the proposed model, the simplified formulas were proposed via numerical fitting for cases under uniform loading and centralized loading at the mid-span. Finally, based on the proposed formulas, a simplified calculation method for the reinforcement stress in service stages was established. Comparisons were made between the proposed formulas and design code. The results showed that the design code method greatly underestimated the contribution of concrete under negative moments, leading to notable overestimations in the reinforcement stress and crack width.

MISCLASSIFICATION IN SIZE-BIASED MODIFIED POWER SERIES DISTRIBUTION AND ITS APPLICATIONS

  • Hassan, Anwar;Ahmad, Peer Bilal
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • 제13권1호
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    • pp.55-72
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    • 2009
  • A misclassified size-biased modified power series distribution (MSBMPSD) where some of the observations corresponding to x = c + 1 are misclassified as x = c with probability $\alpha$, is defined. We obtain its recurrence relations among the raw moments, the central moments and the factorial moments. Discussion of the effect of the misclassification on the variance is considered. To illustrate the situation under consideration some of its particular cases like the size-biased generalized negative binomial (SBGNB), the size-biased generalized Poisson (SBGP) and sizebiased Borel distributions are included. Finally, an example is presented for the size-biased generalized Poisson distribution to illustrate the results.

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횡하중에 대한 휨재의 부모멘트 재분배 (Redistribution of Negative Moments in Beams Subjected to Lateral Load)

  • 엄태성
    • 콘크리트학회논문집
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    • 제23권6호
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    • pp.731-740
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    • 2011
  • KCI 2007, ACI 318-08에 제시된 모멘트재분배 방법은 등분포 중력하중을 받는 연속 휨재에 대하여 검증된 방법이다. 횡하중에 의한 모멘트재분배 및 비탄성 거동은 중력하중과 전혀 다른 메커니즘을 발생된다. 이 연구에서는 기초역학에 근거하여 중력하중과 횡하중을 받는 철근콘크리트 모멘트골조의 보에 발생되는 모멘트재분배와 소성변형의 관계를 정량화하고, 이로부터 보의 소성변형능력에 근거한 모멘트재분배 설계법을 제안하였다. 제안된 모멘트재분배비는 KCI 2007, ACI 318-08 등 기존 설계기준과 마찬가지로 극한한계상태의 단면해석으로 결정되는 철근의 인장변형률로 정의된다. 또한 모멘트재분배비는 경간, 철근비, 단면강성, 변형경화 거동에 의하여 영향을 받는다. 제안된 방법을 사용하여 탄성해석으로 구한 설계모멘트를 재분배시키는 설계 가이드라인 및 예제를 제시하였다.

후진 미분 연산자를 이용한 이산확률분포의 적률 유도 (Derivations of moments for discrete probability distributions using backward difference operators)

  • 조길호
    • Journal of the Korean Data and Information Science Society
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    • 제22권3호
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    • pp.505-513
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    • 2011
  • 본 논문의 목적은 후진 미분 연산자를 이용하여 이산확률분포에 대한 원점으로부터의 r차 적률을 구하는 공식을 유도한다. 이 공식을 이용함으로써 r차 적률은 0에서 계산된 $x^r$의 r번째 후진 미분 연산자까지의 일차결합으로써 계산됨을 알 수 있다.

Distortional buckling of I-steel concrete composite beams in negative moment area

  • Zhou, Wangbao;Li, Shujin;Huang, Zhi;Jiang, Lizhong
    • Steel and Composite Structures
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    • 제20권1호
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    • pp.57-70
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    • 2016
  • The predominant type of buckling that I-steel concrete composite beams experience in the negative moment area is distortional buckling. The key factors that affect distortional buckling are the torsional and lateral restraints by the bottom flange. This study thoroughly investigates the equivalent lateral and torsional restraint stiffnesses of the bottom flange of an I-steel concrete composite beam under negative moments. The results show a coupling effect between the applied forces and the lateral and torsional restraint stiffnesses of the bottom flange. A formula is proposed to calculate the critical buckling stress of the I-steel concrete composite beams under negative moments by considering the lateral and torsional restraint stiffnesses of the bottom flange. The proposed method is shown to better predict the critical bending moment of the I-steel composite beams. This article introduces an improved method to calculate the elastic foundation beams, which takes into account the lateral and torsional restraint stiffnesses of the bottom flange and considers the coupling effect between them. The results show a close match in results from the calculation method proposed in this paper and the ANSYS finite element method, which validates the proposed calculation method. The proposed calculation method provides a theoretical basis for further research on distortional buckling and the ultimate resistance of I-steel concrete composite beams under a variable axial force.

연속화된 Prestress 거더교의 거동연구 (A Study on Behaviors of Prestressed Bridge Girders Made Continuous)

  • 구민세;최인식;김진헌
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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    • pp.396-403
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    • 2002
  • To eliminate deck joints, continuous span bridges are becoming an attractive option. Defferent continuty methods and construction sequences have different time-dependent effects on the behavior of the bridge system. This paper is carried out to evaluate the restraint moments generated at interior span of bridges constructed with full-span prestessed concrete bridge. Especially, effects of creep and shrinkage between ACI209-95 and Eurocode 2 are compared in this paper. Time-dependent effects in prestressed concrete bridges include creep and shrinkage of concrete. Creep due to prestress makes the girders camber up and cause positive restraint moments. The most significant effect of shrinkage in continuous bridges is the differential shrinkage that occurs because of the difference in type and age of girder and deck concrete. Differential shrinkage between the precast girder and the deck typically causes negative res03int moments.

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Analytical and experimental study on the behavior of elastically supported reinforced concrete decks

  • Park, Nam-Hoi;Kang, Young-Jong;Choi, Jin-Yu;Lim, Nam-Hyoung
    • Structural Engineering and Mechanics
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    • 제15권6호
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    • pp.629-651
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    • 2003
  • Current design specifications prescribe that the upper and lower reinforcement mat is required in the same amount to resist negative and positive moment in bridge decks. This design concept is primarily based on the unrealistic assumption that the girder plays a role of rigid support against deck deflection. In reality, however, girders are flexible and the deflection of girders affect the behavior of deck slabs. In the present study, an analytical method was developed to take the effect of the girder flexibility on the deck behavior into account. The method was formulated based on the slope-deflection equations of plates and harmonic analysis. Unlike the conventional finite element analysis, the input and output schemes are simple and convenient. The validity of the presented study was verified by a series of comparative studies with finite element analyses and experimental tests. It was shown from the analyses that the negative transverse moments of decks were significantly reduced in many cases when the girder flexibility were appropriately taken into consideration whereas the positive moments tend to increase. This poses a strong need to improve the conventional design concept of decks on rigid girders to those on flexible girders.

ON ESTIMATION OF NEGATIVE POLYA-EGGENBERGER DISTRIBUTION AND ITS APPLICATIONS

  • Hassan, Anwar;Bilal, Sheikh
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • 제12권2호
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    • pp.81-95
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    • 2008
  • In this paper, the negative Polya-Eggenberger distribution has been introduced by compounding negative binomial distribution with beta distribution of I-kind which generates a number of univariate contagious or compound (or mixture of) distributions as its particular cases. The distribution is unimode, over dispersed and all of its positive and negative integer moments exist. The difference equation of the proposed model shows that it is a member of the Ord's family of distribution. Some of its interesting properties have been explored besides different methods of estimation been discussed. Finally, the parameters of the proposed model have been estimated by using a computer programme in R-software. Application of the proposed model to some data, available in the literature, has been given and its goodness of fit demonstrated.

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ON SIZE-BIASED POISSON DISTRIBUTION AND ITS USE IN ZERO-TRUNCATED CASES

  • Mir, Khurshid Ahmad
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • 제12권3호
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    • pp.153-160
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    • 2008
  • A size-biased Poisson distribution is defined. Its characterization by using a recurrence relation for first order negative moment of the distribution is obtained. Different estimation methods for the parameter of the model are also discussed. R-Software has been used for making a comparison among the three different estimation methods.

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