Steel based retrofitting interventions for existing masonry walls: a comparative numerical investigation

Abstract

Masonry buildings constitute a significant portion of the architectural heritage all over the world, also in regions affected by a high seismic hazard. Since this constructional material is characterized by lack of tensile strength, as well as small deformation capacity, masonry structures could result hugely damaged if shaken by seismic forces. In order to avoid collapses and reduce structural damage, innovative retrofitting interventions are necessary to improve the seismic behavior of masonry structures. In this context, steel‐based techniques could be considered among the most suitable solutions. In fact, by using such a high‐performant material, additional strength and ductility may be conferred to existing masonry structures. Based on these premises, the present paper focuses on a numerical investigation of two different retrofitting techniques: the CAM© system and the application of steel grids on both faces of a masonry wall. In particular, on the base of an experimental test carried out within the research project In.CAM.M.I.N.O. on an unreinforced masonry wall tested in condition of constant vertical force and horizontal loads, a reference FE Model has been calibrated in Abaqus by using a macro‐modelling approach with a damage‐plasticity material model for the masonry. Then, based on the reference model, the efficiency of the two systems has been investigated and compared by means of numerical analyses, in order to evaluate the strength and ductility increases obtainable by the application of the two retrofitting techniques.

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

“…In the plane of the wall, however, the rectangular arrangement does not bring any increase in strength or stiffness. Both in-depth experimental tests [37] and recent numerical analyses [38], in fact, have shown that the rectangular arrangement of the stainless steel straps leads to an almost negligible increase in the strength of the shear-loaded masonry panels while providing a significant increase in ductility. The use of steel grids on both faces of the masonry wall, conversely, increases both the shear strength and the ductility, but the ultimate displacement achieved with the steel grids is lower than that achieved with the CAM ® system [38].…”

“…Both in-depth experimental tests [37] and recent numerical analyses [38], in fact, have shown that the rectangular arrangement of the stainless steel straps leads to an almost negligible increase in the strength of the shear-loaded masonry panels while providing a significant increase in ductility. The use of steel grids on both faces of the masonry wall, conversely, increases both the shear strength and the ductility, but the ultimate displacement achieved with the steel grids is lower than that achieved with the CAM ® system [38]. The author of this article is of the opinion that the lack of increase in shear strength with the CAM ® system depends on the arrangement of the perforations, which makes the strengthening system labile to horizontal loads [29].…”

“…The ranges of compressive strains in the figures of the apparent Poisson's ratio (Figures [38][39][40] are the same as the ranges of 𝜀 * in Figure 34 and the details in Figures 35b and 36b, respectively. Incidentally, it is worth mentioning that the discussion on the displacements caused by the opening of cracks during a mechanical resistance test assumes a more general meaning, as it allows us to investigate the actual nature of strain-softening in brittle materials [56] and to formulate new constitutive laws in tension [74] and compression [75,76].…”

“…The ranges of compressive strains in the figures of the apparent Poisson's ratio (Figures [38][39][40] are the same as the ranges of 𝜀 * in Figure 34 and the details in Figures 35b and 36b, respectively. Although devoid of actual rheological significance, the curves in Figures 38-40 nonetheless provide some useful information.…”