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

Abstract

ResumoThis 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 submitted 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 reinforcement), 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.Keywords: column; reinforced concrete; strengthening; eccentricity; self-compacting concrete.Este artigo apresenta os resultados de pilares de concreto armado reforçados por meio da adição de camadas de concreto autoadensável, tanto na face tracionada quanto na face comprimida, com ou sem adição de barras de aço longitudinais. Oito pilares foram submetidos a um carregamento com excentricidade inicial de 60mm. Estes pilares possuíam seção transversal retangular de 120 mm x 250 mm, comprimento de 2000 mm, e armadura longitudinal constituída por quatro barras de 10 mm de diâmetro. Os pilares de referência, P1 e P2, foram ensaiados até a ruptura sem nenhum tipo de reabilitação. Os pilares P3 à P8 foram inicialmente submetidos a um pré-carregamento que provocava na armadura longitudinal, tensões próximas a do escoamento do aço. Em seguida, estas peças foram descarregadas e reforçadas. Após o concreto do reforço atingir resistência adequada, estes pilares foram ensaiados até a ruptura. Os resultados mostraram que o método de reforço estudado foi eficiente, pois dependendo da face do pilar em que se aplicava a camada de reforço, as peças reabilitadas apresentaram uma capacidade de carga de 2 a 5 vezes maior que a dos pilares não reforçados.Palavras-chave: pilar; concreto armado; reforço; excentricidade; concreto auto-adensável.

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

“…The experimental program included tests on nine columns whose measurements are shown in Figure 1. These models of tests and the test arrangements are similar to those carried out by Adorno (2004), Araújo (2004), Omar (2006), Nascimento (2006) and Sahb (2008). The columns were cast in two phases.…”

“…Nascimento (2006) investigated columns strengthened with SCC on the compressed face and with carbon fiber on the tensioned face. In their works, Omar (2006) and Nascimento (2006) observed load capacity increase on columns under combined bending and axial compression and strengthened with SCC on the compressed face, however, uncoating of the strengthening concrete was also confirmed. To reduce the effects of premature uncoating of the strengthening concrete and consequently of abrupt column strain, Sahb (2008) suggested improving the link between substrate and strengthening concrete by adding anchor bolts in various amounts and positions.…”

“…The experimental and theoretical results with greater concordance occurred in the cases of smaller eccentricities. Omar (2006) studied the behavior of columns strengthened by self-compacting concrete (SCC) on the compressed face and by tension reinforcement on the tensioned face. Nascimento (2006) investigated columns strengthened with SCC on the compressed face and with carbon fiber on the tensioned face.…”

Behavior of reinforced concrete columns strenghtened by partial jacketing

“…Column dimensions and details of column steel reinforcement are shown in Figures 1 and 2 for the model column used in the study. Several researchers (Araújo [4], Omar [5], Sahb [6] e Nascimento [7]), at those two universities, followed Adorno's line of research. Except for Araujo [4], they followed through with studies on column strengthening using a concrete jacketing with self-compacting concrete (SCC) and different kinds of connectors at the new concreteold concrete interface were used.…”

“…Except for Araujo [4], they followed through with studies on column strengthening using a concrete jacketing with self-compacting concrete (SCC) and different kinds of connectors at the new concreteold concrete interface were used. Omar [5] researched column jacketing on different column faces using a layer of self-compacting concrete (SCC). The original columns were loaded until longitudinal steel yielding and then unloaded and strengthened with a concrete jacket.…”