Main goal of this research project on the structural behaviour of seismically strengthened unreinforced masonry (URM) was to investigate the influence of the prefabricated strengthening elements on the structural behaviour of masonry walls under cyclic shear loading. Load tests on a series of four clay block masonry walls have been completed. Each 0.175 m thick and 2.6 m high wall was placed between two 0.5 m long prefabricated and pre-stressed concrete in-filled clay block elements which were friction-locked connected to the URM wall. Preliminary results of tests on specimens were analyzed and allow a set of conclusions to be drawn:

• Strengthening the URM walls with prefabricated, pre-stressed elements improves their structural behaviour and performance under cyclic horizontal loading.
• A higher ductility and larger energy dissipation capacity of strengthened walls (compared to the URM walls) could be expected.
• Tested strengthening elements are easy to install on site and, having a masonry block casing, integrate well in the overall (architectural) concept.

Further research work should concentrate on developing simple design methods, analytical and numerical, capable of capturing the structural behaviour of the pre-stressed concrete in-filled clay block elements.