Comparison between Design Formulations and Numerical Results for In-Plane FRCM-Strengthened Masonry Walls

Abstract

Strengthening strategies and structural rehabilitation of existing buildings with innovative materials and techniques are today one of the main activities in the field of structural engineering. Externally bonded Fiber Reinforced Cementitious Matrix (FRCM), materials are spreading as an alternative strengthening technique to the more traditional Fiber Reinforced Polymer (FRP) ones, especially for masonry elements. This research focuses on the assessment of the shear strength of in-plane FRCM-strengthened masonry walls by means of code predictions and numerical results, with particular attention on the interpretation of diagonal compression tests simulated by means of Finite Element (FE) models. Firstly, the various approaches commonly adopted for the interpretation of diagonal compression tests in terms of shear strength were examined, since codes give generally provisions in terms of maximum shear force, while several experimental and numerical results of diagonal compression tests are available in literature. Then, the numerical simulations of diagonal compression tests obtained by several FE analyses in a previous work were examined in light of these different approaches; the corresponding predictions of the shear force are compared with code indications in order to individuate the most reliable approach both for the un-strengthened and the FRCM-strengthened walls. For the latter ones, a detailed analysis of the actual strain levels in the reinforcement was carried out, too, by means of FE analysis.

Active Confinement of Masonry Walls with Stainless Steel Straps: The Effect of Strap Arrangement on the in-Plane Behavior of Strength, Poisson’s Ratio, and Pseudo-Ductility

“…The stress redistribution occurring in the specimen in the non-linear range does not affect the value of the maximum principal stress, σ I (the tensile stress in Appendix A), computed with the linear elastic solution [58]. For this reason and for the discussion on the interpretation of the diagonal compression test in Appendix A, Equation (A26) will provide the values of the diagonal tensile strength later in this document, as in References [40,41,[59][60][61]:…”

“…The second method is easier to perform than the shear-compression test [41]. It consists of loading one diagonal of a square masonry wall in compression, until failure, which usually involves the formation of cracks along the loaded diagonal.…”

Masonry Elements Strengthened with TRM: A Review of Experimental, Design and Numerical Methods

“…The results are compared in terms of diagonal load at the varying displacements (or strains) along the panel diagonals, monitored along almost their whole length or, occasionally, focusing on a more restricted central portion [8,23,27,[32][33][34]. The results can also be reported in terms of calculated shear stress at the varying shear strain, but these outcomes are affected by the different interpretations given to the tests and, in particular, to the assumed stress state at the panel center, which is still an open issue, as evidenced by several authors [28,32,[35][36][37]. Most of the diagonal-compression experimental tests available in the literature on TRM-strengthened masonry focused on a single leaf, clay solid brick masonry; however, some authors tested also panels made of tuff [8,23,27,32,33,38], hollow bricks [17], stones [18,24,25,30] and multiple leaves or infill clay brick masonry [19,24,26,29].…”

“…The results are compared in terms of diagonal load at the varying displacements (or strains) along the panel diagonals, monitored along almost their whole length or, occasionally, focusing on a more restricted central portion [8,23,27,[32][33][34]. The results can also be reported in terms of calculated shear stress at the varying shear strain, but these outcomes are affected by the different interpretations given to the tests and, in particular, to the assumed stress state at the panel center, which is still an open issue, as evidenced by several authors [28,32,[35][36][37].…”

Effects of the Mortar Matrix on the Flexural Capacity of Masonry Cross Sections Strengthened with FRCM Materials

“…Indeed, cementitious matrices offer better performance under elevated temperatures and better compatibility with modern masonry substrates. In fact, several authors observed good performances in practical applications [14][15][16][17][18][19]. More studies, however, are required to better understand the behavior of composite material on the structural response of strengthened masonry elements [20][21][22], both in terms of flexural [23][24][25] and shear performance [26][27][28].…”