Revised code provisions for long-term deflection calculations

Beeby, A. W.; Scott, Richard; Jones, A. E. K.

doi:10.1680/stbu.2005.158.1.71

Cited by 16 publications

(12 citation statements)

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“…Many works have dealt with the time-dependent behaviour of reinforced concrete [2][3][4][5][6][7][8] and some others have focused on cyclic loads [9][10][11], but the interaction between both effects has not usually been studied, in spite of the fact that it is a relatively common situation of real structures. Moreover, codes of practice do not help practice engineers in understanding such interactions.…”

Section: Introductionmentioning

confidence: 99%

Some remarks on the interaction of long-term effects in deflections of RC members

Zanuy

2016

Engineering Structures

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Section: Introductionmentioning

confidence: 99%

Some remarks on the interaction of long-term effects in deflections of RC members

Zanuy

2016

Engineering Structures

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“…Prakhya and Morley (1990) adopted a tensile stress block comprising a linear ascending branch and a non-linear descending branch, while Kaklauskas and Ghaboussi (2001) adopted a tensile stress block composed of a linear ascending branch and a linear descending branch. Scott (1983) and Beeby et al (2005) proposed tensile stress blocks each comprising multi-linear ascending and descending branches. Recently, Torres et al (2004) adopted the strategy of determining the unknown parameters by curve-fitting with empirical momentcurvature curves given in a design code.…”

Section: Introductionmentioning

confidence: 99%

Tension stiffening in concrete beams. Part 1: FE analysis

Ng¹,

Lam²,

Kwan³

2010

Proceedings of the Institution of Civil Engineers - Structures

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Although after cracking, concrete has negligible tension capacity, the intact concrete between cracks within the tension zone of a reinforced concrete beam can still develop significant tensile stresses to contribute to the flexural stiffness of the concrete beam. Such a tension stiffening effect in a flexural member is not quite the same as that in an axial member because the tensile stresses in a cracked flexural member are induced not only by the steel reinforcement-concrete bond but also by the curvature of the flexural member. In this study, the tensile stresses developed in cracked concrete beams are analysed using a finite-element (FE) model that takes into account the non-linear biaxial behaviour of the concrete and the non-linear bond stress-slip behaviour of the steel reinforcement-concrete interface. Based on the numerical results so obtained, a tensile stress block is proposed for section analysis of the momentcurvature curves of reinforced concrete beams at both the uncracked and cracked states. It will be shown in part 2 of this paper that the tensile stress block may also be used for member analysis of the load-deflection curves of concrete beams without resorting to FE analysis.

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“…Where β 1 is a coefficient of the bond properties of the reinforcement (β 1 = 1.0 for ribbed bars and 0.5 for plain bars); β 2 is a coefficient of the duration and cyclical loading (β 2 = 1.0 for a single, short-term load; β 2 is 0.5 for cyclical or sustained loads); (Beeby et al 2005).…”

Section: Model Of Ceb-fip Codementioning

confidence: 99%

“…The recent FIB codes no longer apply the β 1 factor to this calculation, (Vollumand Afshar 2009, Beeby et al 2005). Instead, the coefficient η, for allowing the tension stiffing effects, is defined and calculated as shown in Eqs.…”

Section: Model Of Ceb-fip Codementioning

confidence: 99%

“…Following the above mentioned modification and based on the observations in the Durham and Leeds Universities tension experiment results, (Beeby et al 2005) suggested that use of β 2 for both long and short term deflections to account for the rapid decrease in tension stiffening is allowed. Recently Vollum and Afshar (2009) have suggested a method for the calculation of β 2 for short term loading during the construction period.…”

Section: Model Of Ceb-fip Codementioning

confidence: 99%

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Limitations and Uncertainties in the Long-Term Deflection Calculation of Concrete Structures

Vakhshouri

Nejadi

2014

Vulnerability, Uncertainty, and Risk

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There is no distinctive boundary in RC members when the short term deflection ends and long term begins. Simplified procedures for predicting deflections in design codes are not compatible with actual deflection under service loads especially in sensitive elements such as floor slabs. Design codes generally predict the time dependent deflection by multiplying an empirical amplification factor by an instantaneous deflection. Despite of negligible difference in instantaneous and short term deflection, the calculated value for long term deflection that is due to decrease in stiffness overtime due to the inelastic deformation of concrete shrinkage and creep, is sometimes significantly less than the actual deflection.In this paper, simplified calculations for the ratio of long term to short term deflection in codes and some empirical works have been compared. Based on the comparison between simplified methods and data obtained from experimental investigations of Gilbert and Guo (2005) it is evident that the long term/ short term ratio is sometime significantly beyond the range of codes of practice.

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Revised code provisions for long-term deflection calculations

Cited by 16 publications

References 1 publication

Some remarks on the interaction of long-term effects in deflections of RC members

Some remarks on the interaction of long-term effects in deflections of RC members

Tension stiffening in concrete beams. Part 1: FE analysis

Limitations and Uncertainties in the Long-Term Deflection Calculation of Concrete Structures

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