Seismic behaviour of stone masonry spandrels and one sided strengthening was investigated. The work was divided into three segments. In the first one a complex laboratory test setup for full scale masonry spandrels was designed and assembled. In the second part a stone masonry spandrel in reference and strengthened state was tested. The one sided mortar coating of strenghtened spandrel was about 30 mm thick and reinforced with glass fibre (GFRP) mesh. The strengthened wall had 2.8 times higher strength capacity and reached maximum resistance at about 33 times larger drift. The amount of dissipated energy was increased about 20 fold. The key for achieving such efficiency of strengthening was the use of two kinds of specially designed anchors. In the third segment, resistance of walls was estimated analytically. Because very few models exist in literature, and even those that exist are for brick, not stone masonry, no model could be used directly. Therefore an existing model was sensibly adjusted for the present case. The estimated resistance of a reference spandrel was underestimated by about 25 %, whereas the resistance of the strengthened spandrel was overestimated by about 20 %.
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