Évaluation du comportement en fatigue des poutres en béton armé renforcées à l'effort tranchant à l'aide de polymères renforcés de fibres

Abstract

The risk of collapse of reinforced concrete (RC) bridge girders under long-term cyclic loading (fatigue) is one of the major problems facing the existing infrastructure in modern world including Canada. In North America, one third of bridges are classified as structurally deficient or functionally obsolete. However, the authorities are faced with major economic and technical challenges due to high costs associated with the maintenance and retrofit of these important structures, the continuous increase in service loads and traffic volumes, and the major drawbacks associated to conventional strengthening methods. This highlights the need to develop innovative rehabilitation methods that are more effective, easy to implement, and viable. The use of fiber reinforced polymers (FRP) has attracted enormous interest and is now established as a structurally efficient and cost-effective strengthening technology. Strengthening RC beams with FRP under static loading is well documented and design guides are provided in many international standards and codes. In contrast, studies on the behavior of beams strengthened with FRP under cyclic loads are relatively few, especially with regard to shear strengthening. This is attributed to the fact that fatigue behavior is a complex issue due to the contribution of many variables, such as cyclic loading conditions (load range, frequency and number of applied cycles), the repetitive nature of cyclic loads that may increase the rate of damage due to cumulative fatigue degradation of the structure, as well as the premature shear failure problems. The objective of this doctoral research is to contribute to bridge these gaps and better understand the fatigue behavior of RC beams strengthened with FRP. The study includes theoretical and experimental investigations. The theoretical part aims to synthesize the stateof-the-art devoted to this subject. The experimental part involves exhaustive tests on fullscale RC T-section beams strengthened in shear with externally bonded (EB) FRP. The specimens are subjected to fatigue loading up to 6 million load cycles at a rate of 3 Hz. The specimens that did not fail in fatigue are then tested under static loading up to failure to evaluate their residual capacity. A comparison with the fatigue limits specified by standards and design guidelines is established. The test results demonstrated the effectiveness of the implemented shear strengthening techniques with EB FRP, thus producing significant results that might be useful for the strengthening of concrete bridges and for the construction industry in general. This undertaking has provided important conclusions, particularly due to the relevance of the examined variables such as the cyclic loading range, the FRP strengthening system, and ratio of the transverse steel internal reinforcement.

Date	6 Jul 2015
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Omar Chaallal (Supervisor)