Tensile behavior of linear fastening systems in masonry structures

The seismic retrofit of existing masonry structures often requires the improvement of the connection between the slabs and the walls of the building. Common interventions use post-installed bonded anchors in the shape of linear fastening systems to strengthen the wall-to-wall and roof-to-wall connections in order to achieve the box-like behavior of the structure. Although this type of application is quite common, there is still a lack of knowledge about the tensile behavior of linear fastening systems because the most of the experimental results obtained in the assessment tests are limited to single or double anchor systems. In order to overcome this problem, an experimental campaign was carried out on linear groups of one to five 12 mm threaded bars installed with an adhesive in solid brick masonry specimens. The experimental layout was defined to take into account the most critical configurations (i.e. installation in the mortar joint, limited embedment depth, small spacing) and a special device was designed to ensure a linear distribution of the applied displacements on the group of anchors. The test results obtained are discussed and numerical simulations are presented to highlight the influence of the geometrical imperfections (i.e. eccentricity of the applied load with respect to the center of the group of anchors) as well as the scatter of the strength of the different anchors on the overall capacity of the linear fastening system.