PSI - Issue 44

Gabriele Guerrini et al. / Procedia Structural Integrity 44 (2023) 2214–2221 Gabriele Guerrini et al. / Structural Integrity Procedia 00 (2022) 000–000

2220

7

(a) (b) Fig. 5. Bilinear approximations (blue line) of lateral force-displacement envelopes (red line): (a) specimen P1; (b) specimen P2.

4. Conclusions This paper has evaluated the performance of two jacketing systems for stone masonry structures in seismic areas, through quasi-static cyclic in-plane shear-compression tests. Two specimens, labeled P1 and P2, were built at the Department of Civil Engineering and Architecture of the University of Pavia and tested at the EUCENTRE Foundation laboratories in Pavia, Italy. Specimen P1 was strengthened with a Composite-Reinforced Mortar (CRM) system, while P2 was retrofitted with a Fabric-Reinforced Cementitious Matrix (FRCM) solution. Each specimens included a pier between two window openings, with portions of the top and bottom spandrels. This layout allowed evaluating the effect of retrofit anchorage in nodal regions on the flexural strength of the pier. After presenting the specimen geometry, the material properties, the test setup, and the loading protocol, the experimental performance has been discussed looking at the lateral force-displacement hysteretic responses and at the failure modes associated with the two strengthening options. A bilinear idealization of the force-displacement envelope has also been derived, to obtain equivalent yield strengths and ultimate drift-ratio capacities. Specimen P1 exhibited a flexural response all the way to failure. In fact, the CRM jacketing remained bonded with the masonry pier also under large drift ratios, keeping the shear strength higher than the flexural one throughout the testing phases. This allowed reaching an ultimate drift ratio of 2.5%, which is 2.5 times the 1.0% limit prescribed by current building codes for masonry piers failing in bending. Specimen P2 reached about the same lateral strength of P1, but its failure mechanism transitioned from flexure to diagonal shear after the FRCM retrofit detached from the masonry pier surface. It is likely that a lateral force higher than the masonry shear strength had been achieved before FRCM separation, which led to pier failure when the retrofit lost its effectiveness. This behavior led to ultimate drift ratios of about 1.5%, corresponding to 3.0 times the 0.5% limit imposed by building codes for masonry piers characterized by shear failure. Both CRM and FRCM strengthening solutions proved effective at enhancing the lateral in-plane response of a stone masonry pier, especially in terms of displacement capacity. The detachment issue with the FRCM system may have been accentuated by the unevenness of the stone masonry surface and could be mitigated by improved mechanical connection with the substrate. Future experimental studies may involve different masonry typologies, specimen geometries, axial-load ratios, and jacketing details. Numerical models will be implemented and calibrated against these outcomes, to extend the experimental results and to derive design or analysis guidelines for practical applications.