PSI - Issue 11

Luigi Ascione et al. / Procedia Structural Integrity 11 (2018) 202–209 L. Ascione et al./ Structural Integrity Procedia 00 (2018) 000 – 000

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3. Main features of the homologation process

The Italian guideline qualifies the FRCM composites based on predefined mechanical properties evaluated by means of homologated tensile and debonding tests performed by the Manufacturer through accredited laboratories under the supervision of the Ministry of the Public Works. After a long debate within the Italian scientific community, the following properties have been identified (Ascione and Feo 2016): a) Conventional limit stress (characteristic value),  lim,conv , and conventional limit strain,  lim,conv , as defined in the following; b) Tensile stiffness of the FRCM sample in the stage A, if detectable ( E , mean value); c) Tensile ultimate stress  u (characteristic value) and tensile ultimate strain  u (mean value) of the FRCM sample; d) Tensile ultimate stress  u,f (characteristic value) of the bare (non-impregnated) mesh; e) Young modulus E f (mean value) of the dry mesh; f) Compressive strength f c,mat (characteristic value) of the matrix,. The tensile ultimate strain  u,f of the bare mesh is obtained dividing  u,f by E f . The stresses are referred to the area of the cross-section of the bare mesh ( A f ) present in the sample, without considering the matrix. The values of mechanical quantities should be suitably stable with respect to degradation induced by environmental actions, as described below. The conventional limit stress is obtained by debonding and tensile tests as illustrated in Fig. 3. The guideline recommends three possible types of conventional supports (concrete, tuff masonry, and solid brick masonry), even if other types of supports can be proposed by the Manufacturer. The Manufacturer can choose the type of standard support for which the homologation is required.

Fig. 3. Evaluation of  lim,conv and  lim,conv

The stability of the mechanical properties of FRCMs with respect to the degradation induced by environmental actions is evaluated trough tensile tests of the composite material. The durability tests include freeze-thaw cycles and artificial aging tests. To perform such tests, 4 unconditioned FRCM coupons (used as reference) and other conditioned samples are subjected to tensile testing. The mean value of the tensile ultimate stress provided by the conditioned specimens should not be lower than a specific percentage of the mean ultimate limit stress provided by the unconditioned specimens. The reference standard tests are indicated in Table 1.