Injected Anchors For The Seismic Retrofit Of Historical Masonry Buildings: Experimental Study On Brick Masonry

The paper reports the results of a research on the behaviour of injected anchors in historical masonry under cyclic loads. Tests in laboratory with masonry specimens (bricks and mortar with low characteristics to replicate a real historical masonry) were conducted to analyse the response of steel anchors injected with a special sock and with different sorts of mortar (cement and lime based). The test benches replicate the real condition of the use of these anchors: to connect masonry panels (T and L connections) or to anchor steel ties to contrast the arch thrust. Monotone and cyclic pull out tests were conducted on short and long anchors (injected orthogonally and lengthwise to the masonry main plane) to compare the results and to define the loss of strength under cyclic loads for different situations. The results allowed to obtain: 1) construction of load-displacement graphs, up to the maxi- mum load value (maximum strength) of each anchor and the related displacement; 2) steel bar deformation graphs on the length of the anchors (thanks to the strain gauges installed on steel bars) at different values of load and under cyclic loads; 3) qualitative bond stress curve derived from the steel bar strains, which allowed to investigate the behavior of the anchors along the bar length under cyclic loads.