PSI - Issue 44

Corrado Chisari et al. / Procedia Structural Integrity 44 (2023) 1108–1115 Corrado Chisari et al./ Structural Integrity Procedia 00 (2022) 000 – 000

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3.2. Calibration of the material parameters Elastic properties of blocks were calibrated against the experimental results, providing Young’s modulus E b =1280 MPa and Poisson’s ratio ν=0.2. Friction coefficient and cohesion, characterising the tangential behaviour of the interfaces, were defined by means of shear/sliding tests carried out on masonry triplets. The values used in the numerical model are those reported in Table 1. The tension limit stress value was assumed to be 0.03 MPa, following a parametric study of its effect on the arch response. Mortar reinforcement was calibrated based on the experimental material tests reported in Table 1. Compression behaviour was defined by specifying compressive strength and a perfectly plastic uniaxial constitutive relationship since no compression failure was observed experimentally and it was not expected to be a concern in the models. The post-elastic behaviour in tension was characterised by linear softening, and thus uniquely governed by tensile strength and fracture energy. These were calibrated , together with Young’s modulus E m , on the basis of the experimental results provided by the indirect tensile (flexural) test. An example of such calibration is reported in Fig. 3, where the experimental-numerical plots are displayed together with a view of the specimen at failure. The average values obtained for ordinary and FRLBM are reported in Table 2.

(a)

(b)

Fig. 4. Calibration of the tensile properties of mortar based on flexural tests: (a) experimental-numerical plots, and (b) view of the model at failure.

Table 2. Mortar material properties for the numerical models obtained through calibration.

Mortar type

Young’s modulus [MPa]

Poisson’s ratio [-]

Compressive strength [MPa]

Tensile strength [MPa]

Fracture energy [N/mm]

FRLBM Ordinary

2500 3200

0.2 0.2

29.0 28.0

2.0 5.0

2.2

0.077

As it is possible to see in Table 2, the value of tensile strength for ordinary mortar is not too far from the value reported in Table 1 and based on elastic stress distribution over the cross-section. On the contrary, calibration of FRLBM properties against the experimental force-displacement plot is characterised by lower tensile strength and very high fracture energy, meaning that a redistribution of stresses is possible thanks to the high ductility of the material. Other parameters of Concrete Damaged Plasticity model were defined according to literature suggestions, as in Table 3.