Effizientes Vorspannen von CFK-Lamellen

Efficient Prestressing of FRP-Strips

Strengthening of structures is an emerging engineering field, and requires an efficient strengthening method. Strengthening with pre-stressed near surface mounted (PNSM) carbon fibre reinforced polymers (CFRP) is a powerful technique, where CFRP-strips are placed and pre-stressed in a groove within the concrete cover. The utilisation of CFRP can be increased and the advantages of PNSM are as follows: the activation of dead loads, a better performance for deflection as well as cracks, an improved bond behaviour and protection of the strip against impacts. On the other hand the pre-stressing action is very elaborate, and often very expensive anchorages have to remain at the structure, which have to be protected against corrosion. By using the Composite Wedge-Technique a pre-stressing unit for the PNSM-Method was developed, which operates within the concrete cover and uses the wedge technique. The pre-stressing-force can be applied fast and simple and the device is removed after the strip was glued in the groove. As a final step, the pre-stressing device will be removed and a permanent bond anchorage made of epoxy reisin will be implemented. No corrosive anchoring parts remain at the structure, the method is very durable and efficient and furthermore anchorage costs are diminished.
The pre-stressing device and strengthening method were developed and tested within the scope of the research project "Strengthening with pre-stressed near surface mounted CFRP-Strips" conducted at Vienna University of Technology.