Mestrado em Engenharia Civil (EEC)
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Navegando Mestrado em Engenharia Civil (EEC) por Assunto "Aderência"
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Item Análise do comportamento de pilares de concreto armado reforçados com chumbadores e concreto auto adensável(Universidade Federal de Goiás, 2014-04-11) Marques, Marília Gonçalves; Liserre, Andrea Prado Abreu Reis; Gomes, Ronaldo Barros; http://lattes.cnpq.br/6046088082653028; Gomes, Ronaldo Barros; Liserre, Andrea Prado Abreu Reis; Guimarães, Gilson Natal; Trautwein, Leandro MoutaStrengthening of reinforced concrete columns by jacketing is one of the most common structural rehabilitation techniques in Brazil. For adequate performance, it is necessary, among others, to avoid detachment of the new concrete layer (strengthening material) from the old concrete substrate when the strengthened member is again in service conditions. This paper describes the test results of eight reinforced concrete rectangular columns subjected to combined compression and one-axis bending to evaluate the efficiency of using sleeve wedge bolts across the new concrete/old concrete interface to avoid detachment. The strengthening technique, in this case, consisted of adding a layer of self-compacting concrete to one column face. Two columns tested were monolithic and named PO (original column) e PR (reference column). The other six columns were strengthened using a new 35 mm thick self-compacting concrete layer attached to the column face subjected to highest compressive stresses. Column PO had a 120mm by 250 mm rectangular cross section and its results gave information about column behavior without the use of strengthening. Column PR had a 155mm by 250 mm rectangular cross section and its cross section dimensions matched the strengthened columns but it was cast monolithically. To improve bond conditions between the existing concrete and the new concrete, the concrete surface was roughened and the outermost aggregate was exposed using hydro jetting. Holes along the concrete surface were made to insert the wedge bolts responsible for increasing the bond between the two concrete surfaces. The difference among the six strengthened columns consisted in the position and amount of bolts used. Results indicate the position and amount of the bolts significantly alters the strength capacity of the strengthened columns since premature rupture by concrete detachment was delayed. The reinforcement used was increased approximately three times the ultimate load of the original column, indicating the good performance of reinforcement.Item Estudo da aderência no reparo com concreto autoadensável (CAA): influência do preparo da superfície, da resistência à compressão do concreto da base e do tipo do concreto (convencional e CAA)(Universidade Federal de Goiás, 2011-04-28) Rocha, Adilson Pereira da; Gomes, Ronaldo Barros; http://lattes.cnpq.br/6046088082653028; Gomes, Ronaldo Barros; Guimarães, Gilson Natal; Pereira, Cláudio Henrique de Almeida FeitosaEfficient repairs in concrete structures require perfect bonding between the base concrete and the applied concrete. The experimental analysis shown in this study focused on how bonding is influenced by three types of base concrete preparation: hydro-jet blasting (BHD), manual scabbling (BMA) and mechanical scabbling (BME), as well as two types of base surface condition: dry (0%) and humid (100%) and also by the application of three different types of bonding agents: B - cement + water; C – cement + water + additive superplasticizer; D – cement + water + additive superplasticizer + active sílica. Fifteen conventional concrete bases prepared using concrete with compressive strength of class C20 and fifteen self-consolidating concrete bases with compressive strength of class C30 were tested. Surface roughness was characterized using profiles according to parameters Ra (standard deviation with respect to an average line) and Rz (average height between consecutives peaks and valleys). Self-consolidating concrete with C40 compressive strength was used to repair the concrete bases. Dyna Proceq apparatus was used to determine tension bonding strength. The hydro-jet blasting (BHD) preparation presented the lowest surface roughness values and the highest bonding strength results as well as the lowest values of the coefficient of variation. The manual scabbling (BMA) preparation presented intermediary results. The mechanical scabbling (BME) preparation presented the highest surface roughness values and the lowest bonding strength results. Surface humidity increase the number of concrete base ruptures. The use of bonding agents increased bonding strength regardless of the degree of surface humidity.