2007-2010: “Strengthening of reinforced concrete structures with externally bonded composite materials”, MSc Engineering, Fedja Arifovic, ALECTIA.

In this PhD project carrying capacity of reinforced concrete structures, strengthened by external bonding of Fiber Reinforced Polymer (FRP) materials, is considered. Strengthening of concrete structures may for instance be required when the structure has been damaged, or when the structure is about to be subjected to loads greater than the design loads.

When FRP-materials are externally bonded to a structural element, they act as external reinforcement of the structure. Since the early sixties strengthening of concrete structures by external bonding of materials has been done by application of thin steel plates. This method is, however, being replaced by use of increasingly more popular FRP-materials due to their superior strength-to-weight ratio compared to steel material. FRP-materials are composite materials.

A composite material is a combination of two or more materials that form a third material. The purpose of producing of composite materials is to exploit best qualities of their components, or producing qualities that neither of the original components possesses. For composite materials considered in this study, it is the quality of high strength, stiffness, corrosion resistance and low weight that is of the foremost interest.

In the first part of the project a bond strength model is developed for a composite to concrete joint subjected to shear. In this way valuable knowledge is gained on composite materials’ ability to take over the load when bonded to a structural element.

Further on flexural strengthening is considered. In such case a composite is bonded to the tension face of the beam or slab. In this way the applied composite materials act as replacement, or additional tensile reinforcement. It is shown that classical methods from concrete mechanics may be applied when correction for the contribution from the applied composite material is introduced.

Composite materials may also be used in shear strengthening. When reinforced concrete beams are strengthened in shear, composites are bonded at the side of reinforced concrete beam. It is shown that carrying capacity of a beam strengthened in this way may be found by the plasticity-based crack sliding theory.

Further on, the solutions derived in this project are compared to experiments reported in literature, and the experiments performed during the study.