scholarly journals Creep strains on reinforced concrete columns

2013 ◽  
Vol 6 (4) ◽  
pp. 537-560 ◽  
Author(s):  
E. L. Madureira ◽  
T. M. Siqueira ◽  
E. C. Rodrigues
Keyword(s):  
Reinforced Concrete ◽  
Concrete Columns ◽  
Sustained Load ◽  
Physical Parameters ◽  
Concrete Element ◽  
Memory State ◽  
Reinforced Concrete Columns ◽  
Steel Bars ◽  
State Models ◽  
Creep Strains

A concrete element when kept under sustained load presents progressive strain over time, associated to the creep. In reinforced concrete columns, such deformations cause the stress increase in the steel bars of the reinforcement and may induce the material to undergo the yielding phenomenon. The pioneering formulations about the creep effect, developed on the base of creep coefficient, are applicable, especially, when the stress magnitude remains constant. Its application to reinforced concrete members, which exhibits change in stress magnitude, requires simplifications of which result the memory models, which have the disadvantage of requiring the storage of the stress history. To overcome the difficulties related to the excessive demand for computer memory, State models have been developed that dispense such robustness of storage. The subject of this work is the analysis of creep deformations in reinforced concrete columns on the base of a state model fixing its physical parameters from results obtained through the NBR 6118/07 formulation. The results showed that, in the elapse of the phenomenon, occurs stresses transfer from the concrete mass to the reinforcement steel bars which, in turn, have the effect of restrain the creep strains, confirming, in some cases, an imminent material yielding condition.

scholarly journals Experimental analysis of reinforced concrete columns strengthened with self-compacting concrete and connectors

2012 ◽  
Vol 5 (3) ◽  
pp. 305-315
Author(s):  
P. P. Nascimento ◽  
R. B. Gomes ◽  
L. L. J. Borges ◽  
D. L. David
Keyword(s):  
Reinforced Concrete ◽  
Failure Mode ◽  
Experimental Analysis ◽  
Thick Layer ◽  
Concrete Columns ◽  
The Other ◽  
Experimental Phase ◽  
Self Compacting Concrete ◽  
Reinforced Concrete Columns ◽  
Steel Bars

There are many problems involving cases of destruction of buildings and other structures. The columns can deteriorate for several reasons such as the evolution and changing habits of the loads. The experimental phase of this work was based on a test involving nine reinforced concrete columns under combined bending and axial compression, at an initial eccentricity of 60 mm. Two columns were used as reference, one having the original dimensions of the column and the other, monolithic, had been cast along the thickness of the strengthened piece. The remaining columns received a 35 mm thick layer of self-compacting concrete on their compressed face. For the preparation of the interface between the two materials, this surface was scarified and furrowed and connectors were inserted onto the columns' shear reinforcement in various positions and amounts.As connectors, 5 mm diameter steel bars were used (the same as for stirrups), bent in the shape of a "C" with 25 mm coatings. >As a conclusion, not only the quantity, but mainly, the location of the connectors used in the link between substrate and reinforcement is crucial to increase strength and to change failure mode.

scholarly journals Experimental analysis of reinforced concrete columns strengthened with Self-Compacting concrete

2010 ◽  
Vol 3 (3) ◽  
pp. 271-283 ◽  
Author(s):  
M. Y. M. Omar ◽  
R. B. Gomes ◽  
A. P. A. Reis
Keyword(s):  
Reinforced Concrete ◽  
Ultimate Load ◽  
Rectangular Cross Section ◽  
Concrete Columns ◽  
Loading Capacity ◽  
Longitudinal Reinforcement ◽  
Self Compacting Concrete ◽  
Reinforced Concrete Columns ◽  
Subsequent Test ◽  
Steel Bars

This paper presents the results of reinforced concrete columns strengthened by addition of a self-compacting concrete overlay at the compressed and at the tensioned face of the member, with and without addition of longitudinal steel bars. Eight columns were submit- ted to loading with an initial eccentricity of 60 mm . These columns had 120 mm x 250 mm of rectangular cross section, 2000 mm in length and four longitudinal reinforcement steel bars with 10 mm in diameter. Reference columns P1 and P2 were tested to failure without any type of rehabilitation. Columns P3 to P8 were loaded to a predefined load (close to the initial yield point of tension reinforce- ment), then unloaded and strengthened for a subsequent test until failure. Results showed that the method of rehabilitation used was effective, increasing the loading capacity of the strengthened pieces by 2 to 5 times the ultimate load of the reference column.

scholarly journals Fresh concrete consistency effect on thin-walled columns creep phenomenon

2018 ◽  
Vol 11 (3) ◽  
pp. 644-651 ◽  
Author(s):  
E. L. MADUREIRA ◽  
L. A. PAIVA
Keyword(s):  
Reinforced Concrete ◽  
Fresh Concrete ◽  
Memory Storage ◽  
Sustained Load ◽  
Physical Parameters ◽  
Integral Calculus ◽  
Yielding Condition ◽  
Material Creep ◽  
Thin Walled ◽  
State Models

Abstract A concrete structural member when kept under sustained load presents progressive strains over time, associated to the material creep. The fresh concrete consistency, specially, exerts some effect on that phenomenon. The pioneering formulations developed to modelling the creep of concrete are applicable, directly, to the cases for which the stress magnitude remains constant. Its application to reinforced concrete structural members, that exhibits changes in the magnitude of the stresses over such a time dependent phenomenon, requires simplifications from which result the memory models, whose implementation presents the disadvantage of involving the history of the stresses storage. The State Models were developed to overcome these difficulties, as they result of integral calculus scheme improvement, dispensing such computational memory storage. The subject of this work is the analysis of creep strains on reinforced concrete thin-walled columns, emphasizing the fresh concrete consistency efecct, on the base of a state model, fixing the values of its physical parameters from the NBR 6118/14 proceedings [1]. The obtained results showed the occurrence of stresses transfer from the mass of the concrete to the reinforcement steel bars, that was more pronounced in those cases for which the slump test abatement were the highest and, in some cases, including, it induced the material yielding condition.

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