Effect of Reinforcement Ratio on the Effective Moment of Inertia of Reinforced Concrete Beams

10.14359/4119 ◽  
1993 ◽  
Vol 90 (2) ◽  
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Reinforcement Ratio ◽  
Moment Of Inertia ◽  
Reinforced Concrete Beams ◽  
Effective Moment ◽  
Effective Moment Of Inertia

Rational model for calculating deflection of reinforced concrete beams and slabs

2007 ◽  
Vol 34 (8) ◽  
pp. 992-1002 ◽  
Author(s):  
Peter H Bischoff
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Moment Of Inertia ◽  
Reinforced Concrete Beams ◽  
Beam Deflection ◽  
Rational Approach ◽  
Steel Reinforced Concrete ◽  
Rational Expression ◽  
Effective Moment ◽  
Effective Moment Of Inertia

Deflection control is an important performance criterion that needs to be satisfied to ensure serviceability of the structure for its intended use. The extent of cracking and amount of reinforcement affects the flexural rigidity, EI, of a reinforced concrete member and both the Canadian concrete design standard (CSA A23.3-04) and ACI Building Code (ACI 318-05) use an effective moment of inertia, Ie, that was originally proposed by Branson to compute beam deflection. This is an empirically derived equation that works well within a narrow range of limits corresponding to steel-reinforced concrete beams with a reinforcing ratio between 1% and 2%. However, the equation underestimates deflection for steel-reinforced concrete beams and slabs with a reinforcing ratio less than 1% and for most beams reinforced with low-modulus, fibre-reinforced-polymer (FRP) bars. Deflection of slender tilt-up wall panels can also be underestimated with Branson's equation. This paper provides an explanation of why the Branson equation does not always work well in predicting deflection, and presents a rational approach to develop an alternative expression for the effective moment of inertia that works equally well for both steel- and FRP-reinforced concrete at all reinforcing ratios. A rational expression is also introduced for continuous beams that uses an averaged moment of inertia, Ie,avg, to calculate beam deflection. Changes are included in a proposed revision to deflection prediction requirements specified in clause 9.8 of CSA A23.3-04.Key words: reinforced concrete, deflection, effective moment of inertia, serviceability.

scholarly journals Prediction of Deflection of Reinforced Concrete Beams Strengthened with Fiber Reinforced Polymer

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1367 ◽  
Author(s):  
Daugevičius ◽  
Valivonis ◽  
Skuturna
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Moment Of Inertia ◽  
Reinforced Concrete Beams ◽  
Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Simple Method ◽  
Reinforced Polymer ◽  
Effective Moment ◽  
Effective Moment Of Inertia

The article analyses the calculation of the deflection of reinforced concrete beams strengthened with fiber reinforced polymer. This paper specifically focuses on estimating deflection when the yielding of reinforcement is reached. The article proposes a simple method for calculating deflection that was compared with the experimentally predicted deflection. The carried out comparison has showed that the proposed method is suitable not only for the strengthened beams but also for the reinforced concrete beams with a varying reinforcement ratio. The suggested calculation method is based on the effective moment of inertia, such as the one introduced in the ACI Committee 318 Building Code Requirement for Structural Concrete (ACI318). The development of deflection was divided into three stages, and equations for the effective moment of inertia were proposed considering separate stages. In addition, the put forward equations were modified attaching additional relative coefficients evaluating a change in the depth of the neutral axis.

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