Predictive Models for the Compressive Strength and Ultimate Strain of FRCM Confined Masonry

So far, the use of fabric reinforced cementitious matrix (FRCM) composites for the external confinement of masonry is still limited due to the lack of accurate formulas for estimating the compressive strength and the ultimate strain of confined members. With the aim to contribute to partially filling this knowledge gap, the authors have been carrying out studies on the FRCM confined masonry for some time and, in a recent study, they proposed some formulations for the prediction of the compressive strength which are also reported in this paper. In continuity to that work, analytical formulas for the prediction of the ultimate strain are proposed here, which were derived by considering a wide experimental database compiled from the technical literature. This database includes results of compression tests on FRCM confined masonry columns with square, rectangular and circular cross-sections; most of the collected members consist of artificial blocks and only a limited number of specimens is made of natural stones (tuff units or limestone). The mentioned formulas were developed by applying error minimization techniques to the collected experimental results which were either treated all together or treated separately based on the FRCM systems. The suitability of the found relationships was examined based on a comparison in terms of reliability with the few formulas published in the literature or reported in international guidelines. To this purpose, it is worth highlighting that the current Italian Guidelines CNR-DT 215/2018 do not provide indications about the estimate of the ultimate strain of the FRCM confined masonry, and the study proposed here represents a first attempt to provide a contribute to the document.