Mobile device to perform a single lap shear test on frp bonded on a concrete real structure
Résumé
To characterize the adhesion of FRP composites bonded on concrete, the shear test is frequently used in laboratories studies. Several decades ago, CEREMA developed an experimental device able to perform a single lap shear test on FRP bonded on concrete or steel substrates. With this test, the failure mode of the studied FRP system, its maximum capacity and its anchorage length can be determined. It has also been used to study the durability of different FRP reinforcement systems subjected to hygrothermal ageing. However, this set-up is not suitable for characterization of FRP systems bonded on real structure and at that time, pull-off is the sole test available for onsite testing. Then considering that i) accelerated ageing conditions are always questionable regarding real environmental conditions, ii) that laboratory samples are not fully representative of the substrates of the retrofitted structures iii) that the pull-off test is unable to characterize the shear behavior of bonded joints and iv) that it exists a need for onsite acceptance testing, CEREMA, in collaboration with IFSTTAR, has therefore developed a specific mobile device that can be brought onsite in order to perform a shear test on a real structure.
The system is equipped with a jack of capacity 100 kN, which is adapted for the shear characterization of both externally bonded FRP sheets and strips. The machine is connected to a computer equipped with an ergonomic software that controls either the load rate or the displacement rate. It gives, in real time, the stress-displacement curve, the failure force and the anchorage length. Furthermore, the test can be monitored by strain gages, which may give access to cohesive zone model of the interface.
Some validation tests have already been carried out successfully on retrofitted RC bridges and the equipment will be fully qualified in 2018. In a near future, application or inspection companies will be offered the possibility to acquire this equipment.