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

Injected Anchors For The Seismic Retrofit Of Historical Stone Masonry Buildings: In Situ Experimental Tests

The paper reports the results of a research on the behaviour of injected anchors in historical masonry under cyclic loads. Monotonic and cyclic pull-out in situ tests were conducted on historical stone masonry to analyse the response of anchors injected orthogonally to the masonry main plane and at different heights to evaluate also the effect of different values of normal confinement on the anchor behaviour. Moreover the tests were conducted on anchors of different length, instrumented with strain-gauges. The aim was to investigate the loss of strength under cyclic loads. The results allowed: 1) construction of load-displacement graphs, up to the maximum load value (maximum strength); 2) steel bar deformation graphs on the length of the anchors at different values of load, under cyclic loads; 3) qualitative bond stress curve, derived from the steel bar strains, to investigate bond behavior along the bar length

Pre-stressed vertical injected anchors on historical masonry: a case study, the Bell Tower of Botta di Sotto il Monte Papa Giovanni XXIII

The Bell Tower of the Church "Sacro Cuore Gesù e S. Egidio Abate" in Sotto il Monte (Bergamo, Italy), represents a case study of the research programme "ANIMUS", funded by the European Programme FESR-2007-2013. The necessity of building a steel belfry on top of the bell tower required a detailed study of its connection with the supporting masonry structure. This connection has been realized by means of deep vertical anchors, obtained by grouting steel bars by injecting the grout in special socks, such that any dispersion of the mortar in the masonry is avoided. By this technique, a "bulb" creating an effective interlock with the masonry structure is created. The behaviour of the system has been studied by means of a finite element model, allowing to assess the performance of the connection under wind and seismic loads both at service and ultimate limit states. The results have highlighted the opportunity to design vertical anchors with a double bulb of mortar. This way, by grouting the deeper bulb soon after installation, the anchor could be pre-stressed to avoid any decompression of the connection between the superstructure and the masonry tower under service loads. The upper bulb, grouted at a later time, has the role of transferring the loads exceeding serviceability limit state to the masonry structure. After the installation of vertical anchors, an experimental phase started with the execution of cyclic tests, thus allowing to evaluate the effectiveness of the intervention and to compare experimental and numerical results