Strengthening of concrete slabs by bonded reinforcement to increase punching resistance

ABSTRACT

Strengthening of concrete slabs to increase punching resistance with bonded reinforcement is currently not allowed by the majority of codes because of the lack of specific theoretical and experimental studies. For this reason, the University of Applied Sciences (UAS) Fribourg carried out a theoretical and experimental research on strengthening of concrete slabs by bonded reinforcement to increase punching resistance. The experimental studies include nine load tests on concrete slabs of 2.40 m x 2.40 m and a thickness of 200 mm. These slabs were strengthened by high performance composite material : CFK laminates, prestressed or not prestressed ; CFK laminates with or without a mechanic anchor system ; carbon, aramide and glass fiber sheets. A significant increase of punching resistance has been proved, in particular on slabs strengthened by prestressed CFK laminates and laminates with mechanic anchor systems. On the basis of these experimental studies, the proposed strengthening technique could be applied for cases which are similar to the tested examples. However, the establishment of general recommendations for the design of bonded reinforcement requires additional studies.