ANIDIS - L'ingegneria Sismica in Italia, ANIDIS XIX & ASSISi XVII - 2022

Dimensione del carattere:  Piccola  Media  Grande

Study on the effectiveness of a CRM system: in-plane and out-of-plane cyclic tests on masonry piers

Emanuele Rizzi, Natalino Gattesco

Ultima modifica: 2022-08-31


In the paper are presented the results of a broad experimental campaign concerning in-plane shear-compression tests and out-of-plane three-point bending tests performed on full scale masonry samples, to assess the effectiveness of a CRM (Composite Reinforced Mortar) strengthening system. In particular, the shear-compression tests were carried out on masonry samples strengthened with the application of the CRM system on one or both faces of the wall, consisting of a 30 mm thick mortar coating, reinforced with a preformed glass fiber composite mesh (GFRP). In the former case, to connect wall wythes, artificial diatones made of a stainless steel threaded rod injected with cementitious grout were used; in the latter case, couples of GFRP L-shape connectors, lap spliced through epoxy resin, were used, to confine the masonry wall.

Shear-compression and three-point bending tests on piers were carried out on both reinforced (RM) and unreinforced masonry (URM), as a reference. Double-leaf rubble stone masonry (350 mm thick) was considered. Shear-compression tests were carried out on samples 1500 mm wide and 1960 mm tall. The test setup reproduced a shear-type scheme (rotation prevented at top and bottom ends of the sample). A vertical axial force was applied (0.5 MPa) and maintained constant on all samples; then various cycles were performed between couples of equal horizontal displacements but with different sign up to reaching the sample collapse. A significant effectiveness was obtained with both strengthening techniques: 60% increase in resistance and 150% in displacement capacity, with the strengthening at one side, and 110% increase in resistance and 320% increase in displacement capacity, with the strengthening at both sides. One out-of-plane test was performed on a sample 1030 mm wide and 2480 mm tall, strengthened by applying the CRM system on one side; artificial diatons were also used to prevent the detachment between the wythes of the wall. The sample was arranged vertically and loaded cyclically according to a three-point bending scheme. The results were compared with those of the equivalent unreinforced sample and evidence a considerable increase in resistance (700%) and in displacement capacity (200%). The collapse of the strengthened sample occurred at the composite mesh rupture.

Simplified analytical approaches, based on the mechanical characteristics of the component materials, are presented in the paper to predict the experimental results; both approaches fit quite correctly the experimental results.

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