FRP-confined masonry columns

Historical buildings are often prone to brittle failures due to their lack of structural redundancy and robustness. Safety is guaranteed until the strength of masonry elements is reached; in the post-cracking field there are not significant resources that allow the structure to maintain its structural integrity. Columns result the most critical elements since they allow the entire load to be transferred by compression to the foundation system, but have a brittle behaviour under compression or shear loads. Brittle failure of masonry columns may be mitigated or avoided by using fibre reinforced polymer (FRP) composites as confining devices, reducing the capacity of the column to have large lateral strains. This paper reports the results obtained by the authors in the last years after the study of the mechanical behaviour of FRP-confined masonry columns, also compared with results obtained by other researchers in the field . Data are collected in order to show a possible calibration of European and Italian guidelines that are used by practitioners involved in the structural retrofit of historical buildings. Analytical models based on the calibration of hardening factors in terms of strength and ultimate axial strain are shown and applied for columns made with different masonry materials, different geometry and different strengthening scheme. Limestone and clay masonry columns were studied, effect of square, rectangular and circular cross section will be reported as same as the effect of internal confinement with bars or external confinement with continuous jacket or discontinuous strips, that strongly influence the mechanical response. Recommendation for future research in this field are presented based on a calibration of the existing analytical models and available results.