Erhöhung der Verbundtragfähigkeit von aufgeklebten CFK- oder Stahl-Lamellen auf Stahlbetonkonstruktionen durch Bügelumschließungen

Increase of the Bond Capacitiy of Externally Bonded CFRPor Steel-plates on RC-Structures as the Result of External Enclosures

Strengthening of concrete structures with externally bonded CFRP- or steel-plates has become a well established strengthening method in many countries. In Germany building authority approvals demand that the end of a plate has to be provided by a glued external enclosure. Glued enclosures are primarily needed in order to increase the shear force capacity of a RC member. It is known, that a transverse enclosure of longitudinal CFRP-plates has a positive effect on the buckling load of the latter, which is yet completely unknown. The aim of this work is to assess the increase of the buckling load caused by the enclosure. In the paper the dependency between the so-called self-induced contact pressure of an external enclosure with steel frames or laminated carbon fiber sheets and the longitudinal force of the CFRP- or steel-plate is shown. The self-induced contact pressure is the result of the vertical lifting of the plate towards the external enclosure due to the beginning of plate's debonding process. The test results show, that the increase of the plate-force depends on the type and size of the external enclosure. In some tests up to twice of the ultimate load was optained. An engineering model is presented to take into consideration the effect for dimensioning.