Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

One commonly used method to increase the shear capacity of existing concrete structures consists of adding vertical steel bars anchored to the structure by means of mechanical anchorages, such as expansion torque controlled anchorages or steel anchorage plates. If the drilled holes are not filled with adhesive then the bars are unbonded along their length. In order to study the behaviour of concrete members with unbonded transverse reinforcement, thick concrete beams (width of 610 mm and height of 750 mm) were loaded until shear failure. It has been observed that their shear capacity is closely related to the shear cracking behaviour. At shear cracking, the propagation of one large diagonal crack is required to activate the vertical unbonded bars, thereby reducing the aggregate interlock shear capacity along the cracks. Beams containing at least minimum amounts of conventional stirrups experience several diagonal cracks at shear failure, whereas a beam with unbonded bars tends to have one dominant crack and can therefore experience the size effect in shear. A finite element (FE) model was also used to study the parameters influencing the behaviour of concrete members with unbonded transverse bars. The finite element results show very good agreement with the experimental results.