Analytical Studies on Debonding Behaviour of RC Beams Strengthened with UHPFRC Overlay

摘要

The debonding characteristics of ultra-high-performance fibre-reinforced concrete (UHPFRC)-strength-ened structures under certain loading conditions have been investigated in this paper. Debonding of UHPFRC-strengthened structures seldom occurs owing to the fact that the tensile strength and the stiffness of UHPFRC are similar to that of the concrete substrate. This work concentrates mainly on the strengthening scheme where UHPFRC is provided in the form of strips at the tension zone of concrete. The studies on the effect of normal and shear stresses at the interface of the beam and UHPFRC strip with load increments are essential to determine the scheme of strengthening. The effect of interfacial shear and normal stresses near the strip end was studied by using the Tounsi model which is a modification of Teng model. A comparative study on the variation of the interfacial shear and normal stresses for the beams retrofitted with UHPFRC strip and other repair materials has been carried out. In the present study, the variation of stresses is investigated at two load levels with one load close to the pre-damage load given to the beam and the other load close to the ultimate load. Analytical studies are carried out to study the debonding behaviour of damaged RC beams strengthened with UHPFRC strips under static and fatigue loading. Parametric studies have also been carried out to determine the optimum configuration of the strips to be bonded to the beams.