PSI - Issue 44

Ingrid Boem et al. / Procedia Structural Integrity 44 (2023) 2238–2245 I. Boem, B. Patzák, A. Kohoutková / Structural Integrity Procedia 00 (2022) 000–000

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To set the parameters concerning the masonry ply (“Cdpm2” material model), the experimental tests performed on unreinforced samples are considered. In particular, the compression tests on masonry wallets (500x350x1000 mm 3 ) to calibrate the compressive parameters (Fig. 2b), and the shear-compression test (1500x350x2000 mm 3 ) to deduce the tensile ones (see §3). 3. In-plane shear-compression tests The shear-compression tests are generally aimed at investigating on the in-plane behavior of the piers in a masonry building, that are the wall portions between two adjacent openings, at the same storey level. The experimental tests herein considered concerned double-wythe rubble stone samples, having nominal dimensions 1500x1960x350 mm 3 (width x height x thickness) - Fig. 3a. The samples were built in the testing laboratory on reinforced concrete beams (cross section 300x350 mm 2 ) that were bolted to a steel base, fixed to the floor. On the top of the sample, another reinforced concrete beam was installed and then bolted to the upper steel beam of the testing apparatus, which was constrained so to avoid rotations (shear-type scheme). A constant axial stress level (0.5 MPa) was introduced, while lateral loading cycles at increasing displacement were applied. Three tests were performed: one sample was tested unstrengthened, as reference, one sample with the CRM applied at both sides and one with the CRM on one side only. In the former strengthened sample, 20 couples of GFRP L-shape connectors, passing through the masonry and injected with resin, were introduced; while in the latter, 12 GFRP L-shape connectors and 6 artificial diatones were applied. The diatones were made of stainless steel treaded rods inserted in fabric sleeves injected with high-performance grout. Further details and discussion about the experimental tests can be found in Gattesco et al. (2022). The numerical model is schematized in Fig. 3b: the masonry pier, the reinforced concrete beams and the steel ones were modelled through the 20-nodes brick elements. When considering CRM strengthened masonry samples, the multi-layer cross sections were defined for both the pier and the RC beams, since in the experimental samples the CRM application prosecuted also in the latter. Perfect bond was assumed between the pier and the RC beams, while elastic vertical links were considered for the connections between the RC and the steel beams, according to the experimental evidences (monitored with dedicated potentiometer transducers). To apply the shear-type scheme, a master node was selected at the top of the upper steel beam and all other nodes at that level were forced to have the same translations. To simply reproduce connectors and diatones, axial rigid links connecting the nodes at the opposite wall faces were introduced. The vertical load was distributed at the top of the upper steel beam and maintained constant, while the horizontal load was applied at the actual level of the actuator; the simulations were performed by increasing monotonically the horizontal displacement of the control point, at the upper-right corner of the pier.

A b Fig. 3. In-plane shear-compression tests: (a) main characteristics of the samples and (b) schematization of the numerical model. As indicated in the previous section, the experimental test on the unreinforced pier served for the calibration of the tensile behavior of the plain masonry. In particular, since the failure occurred for diagonal cracking, the tensile strength f t was evaluated from the resistance of the pier V t by using the well-known Turnsek-Cacovic formulation (Eq. 1), considering the axial stress level,  0 , the width, height and thickness of the pier (l , h , t ) and the slenderness ratio b = h/l . The softening was calibrated so as to reproduce as close as possible the experimental behaviour.