Creep characteristics of compressed members strengthened with CFRP composite materials
Tomasz Trapko
Quarterly No. 1, 2011 pages 18-22
DOI:
keywords: CFRP, compression, creeping, rheological strain, strengthening
abstract In the paper, the results of the experimental studies on the creep characteristics of compressed concrete members strengthened with CFRP composite materials are presented. Creep consists in a process in which concrete strains in a structure are subjected to an external load over an extended period of time. Increasing strains initiate additional deformations of structures. The subsequent consequences of them are additional impacts on structural members (e. g. eccentricities). The parameter considering the influence of creep on concrete in engineering calculations is the creep coefficient that is the creep characteristic. The phenomena of concrete creep is investigated and described in specialist literature. The value of the creep characteristic can be obtained with nomograms included in PN-EN 1992-1-1:2008 Eurocode 2. In literature there is a lack of information concerning the coefficient in the case of hybrid members which are combinations of concrete and CFRP composites. The aim of the conducted investigations was to estimate the influence of transverse and longitudinal CFRP strengthening on the creep characteristic of members subjected to long-term axial compression. The experimental investigations were divided into a few stages. The studies were performed on cylindrical concrete specimens with a diameter of 113 mm and height of 350 mm. Two types of strengthening were applied in the experiment. The first type of strengthening was one, two or three layers of CFRP sheet attached around the cylindrical specimens. Second type was longitudinal seg-ments of CFRP strips (with an area AL of 378 or 252 mm2) and one, two or three layers of CFRP sheet as transverse strengthening. For comparative analyses, control unstrengthened specimens were preformed for each type of strengthening. All of the specimens were subjected to long-term axial compression in constant environmental conditions. During the investigations the longitudinal strains of the specimens were measured. When the strains stabilized the specimens were unloaded and standard compression failure tests were performed. The experimental values of the creep characteristics for each type of member was determined in the paper. The analyses of the results is presented as well.