PSI - Issue 44

Matteo Canestri et al. / Procedia Structural Integrity 44 (2023) 2198–2205 Canestri et al./ Structural Integrity Procedia 00 (2022) 000–000

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Fig. 5 shows representative failure modes for all the samples. For the reference specimen, a set of vertical cracks start developing during the test, causing vertical discontinuities across the whole sample, from top to bottom. Reinforced samples showed similar failure modes, either with delamination observed in the external layers of the reinforcement or with a complete detachment of the SRG composite from the confined masonry substrate. 4. Analytical model The positive influence of SRG composite layers on the confinement of masonry columns can be also described and predicted through analytical models. In this chapter, an analytical approach, proposed by Murgo and Mazzotti (2019), is applied. It was derived by adapting the Spoelstra-Monti approach, formulated for Reinforced Concrete (RC) columns strengthened with FRP, to the case of SRG-strengthened masonry columns. Differently from the well known Mander’s model, in which a constant confinement pressure was assumed for RC sections, the Spoelstra Monti approach considers a variable confinement, increasing with the axial stress increment. This is due to the constitutive behavior of FRP and can be applied also to SRG and TRM composites. In this framework, an iterative incremental procedure is needed to characterize the behavior of SRG confined masonry columns, which is synthetically presented in Fig. 6. The complete description of the analytical model can be found in Murgo and Mazzotti (2019).

Fig. 6. Iterative-incremental procedure adapted from the Spoelstra-Monti analytical model.

With reference to the procedure reported in Fig. 6, all the parameters referring to the unconfined masonry were derived from the uniaxial compressive test on the sample C_URM. It should be mentioned that the strain at peak for confined masonry was reduced with respect to the original Mander’s model to account for the reduced nonlinear deformation of masonry with respect to concrete. The coefficients k’ and α were set following the proposal by Rao and Pavan (2014). It should also be noted that the homogenized uncracked elastic modulus E j was considered in the calculations; it was derived from the results of the tensile tests on the SRG coupons (see Section 2.2) considering the homogenized cross section area of the samples, and resulted to be equal to 9255 MPa (C.o.V. 29.6%).