FRP-Confined Masonry: from Experimental Tests to Design Guidelines

Historical masonry construction are prone to brittle failures under seismic or static overloads. Thus retrofit and strengthening of masonry structures, in order to furnish structural ductility and additional strength, is of primary importance for the maintenance of the European Architectural Cultural Heritage. Confinement with Fibre Reinforced Polymer (FRP) materials demonstrated to be an effective solution in a large number of cases. In this research program extensive experimental tests were conducted to calibrate design guidelines for FRPconfined masonry columns, which were introduced in the CNR DT-200 Italian document. Columns built with lime or with calcareous blocks, commonly found in Italy in historical buildings, were tested under compression static loads. Rectangular masonry columns were tested taking into account the influence of several variables: different strengthening schemes, curvature radius of the corners, number of composite layers, cross-section aspect ratio and height of the specimens. Materials characterization was carried out to study the properties of plain masonry. For all cases the experimental tests evidenced a significant increase in load carrying capacity and ductility after FRP-strengthening, which identified the columns as ductile elements despite to the brittle nature of the unconfined masonry. Differences in mechanical behavior due to the geometry of the columns, to the nature of different materials, to different strengthening schemes and to the amount of reinforcement are presented and discussed in the paper. The calibration of design equations recently developed by Italian CNR was conducted by using experimental results.