Ductility and linear analysis with moment redistribution in reinforced high-strength concrete beams

2005 ◽  
Vol 32 (1) ◽  
pp. 194-203 ◽  
Author(s):  
Ricardo N.F do Carmo ◽  
Sérgio M.R Lopes
Keyword(s):  
High Strength Concrete ◽  
Concrete Beams ◽  
High Strength ◽  
Linear Analysis ◽  
Strength Concrete ◽  
Plastic Rotation ◽  
Moment Redistribution ◽  
Rotation Capacity ◽  
The Moment ◽  
Plastic Rotation Capacity

The evaluation of the ductility of reinforced concrete beams is very important, since it is essential to avoid a fragile collapse of the structure by ensuring adequate deformation at the ultimate limit state. One of the procedures used to quantify ductility is based on deformations, namely, the plastic rotation capacity. Knowledge of the plastic rotation capacity of certain regions of the structure is important for a plastic analysis or a linear analysis with moment redistribution. An experimental program is described in this article. It is composed of 10 tests designed to study the moment redistribution and ductility of continuous high-strength concrete beams. Particular care was given to analysing how the tensile reinforcement ratio and the transverse reinforcement ratio influence the plastic rotation capacity of the beams. A comparative study was carried out on several codes related to the moment redistribution permitted and the experimental findings. It was found that some of the recommendations are unsafe. It was also found that high-strength concrete beams, when properly designed, have enough deformation capacity to be used in plastic analysis.Key words: structural concrete, plastic rotation, moment redistribution, high-strength concrete.

Evaluation of ductility and allowable moment redistribution in reinforced concrete structures

2000 ◽  
Vol 27 (6) ◽  
pp. 1286-1299 ◽  
Author(s):  
Adnan Shakir ◽  
David M Rogowsky
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Bending Moment ◽  
Reinforced Concrete Beams ◽  
Bond Slip ◽  
Plastic Rotation ◽  
Moment Redistribution ◽  
Rotation Capacity ◽  
The Moment ◽  
Plastic Rotation Capacity

Designers can use moment redistribution to reduce the design bending moment envelope. Code provisions for moment redistribution are not entirely rational. They neglect the effects of important parameters on permissible moment redistribution and can be very conservative. To establish a realistic limit on permissible moment redistribution, one needs a rational model for predicting the plastic rotation capacity of critical sections (plastic hinges). This paper presents a model for computing the plastic rotation capacity, θp, and permissible moment redistribution, β, in reinforced concrete beams. Important parameters, affecting θp and β, are identified and incorporated in the model. The model is validated against experimental results and shows good agreement. A comparison of the moment redistribution limits is made between the model and CSA A23.3-94. Although the code provides a reasonable estimate of β for unfavourable combinations of parameters, the code can be very conservative when conditions are favourable for moment redistribution. Deeper beams with closely spaced stirrups allow significantly more moment redistribution than that predicted by the code.Key words: moment redistribution, ductility, plastic rotation capacity, bond-slip, shear cracking, reinforced concrete beams, c/d, ultimate concrete strain.

Available plastic rotation in continuous high-strength concrete beams

2008 ◽  
Vol 35 (10) ◽  
pp. 1152-1162 ◽  
Author(s):  
Ricardo N.F. do Carmo ◽  
Sérgio M.R. Lopes
Keyword(s):  
High Strength Concrete ◽  
Concrete Beams ◽  
Concrete Strength ◽  
High Strength ◽  
Reinforcement Ratio ◽  
Experimental Program ◽  
Strength Concrete ◽  
Model Code ◽  
Moment Redistribution ◽  
Eurocode 2

An experimental program was formulated to study moment redistribution in continuous high-strength concrete beams. The evaluation of ductility is important for this type of beam as, for high-strength concrete, the ductility decreases as the concrete strength increases. It is therefore necessary to determine whether the critical sections are able to develop appreciable plastic rotations to justify the application of a linear elastic analysis with moment redistribution. This work specifically examined the influence of the tensile reinforcement ratio and the transverse reinforcement ratio on the rotation capacity of plastic hinges. The moment redistribution obtained experimentally is compared with the guidelines recommended in Eurocode 2, CEB-FIP Model Code 1990, and ACI 318. The results show that ACI 318 recommendations for linear analysis with moment redistribution are too conservative and that the predictions, according to Eurocode 2 and CEB-FIP Model Code 1990, agree with experimental evidence.

Sign in / Sign up

Export Citation Format

Share Document