Issue 51

G. Ramaglia et alii, Frattura ed Integrità Strutturale, 51 (2020) 288-312; DOI: 10.3221/IGF-ESIS.51.23 296 mm 3 and 113×115×240 mm 3 for the solid and hollow masonry respectively. The masonries present mass density of 2000 kg/m 3 and 900 kg/m 3 for solid and hollow bricks respectively. The masonry was prepared using two types of mortar: calcium mortar (namely type a) and cement mortar (namely type b). Brick and mortar were coupled in order to get a realistic representation of the existing masonries. The specimens were wrapped using two types of strengthening systems based on synthetic fiber (carbon and glass) and epoxy-resin. The carbon was applied using sheets having a mass density of 230 g/m 2 . Conversely, the glass fiber was applied using an unidirectional fiber system with a mass density of 430 g/m 2 . The wrapping was applied by means of one or two plies of CFRP, and two and three plies of GFRP with resin interlayers. The mechanical characteristics and the geometries of specimens were shown in Tabs. 4.A and 7.B respectively. In Rao et al. [37] seventyeight specimens were involved in the experimental investigation. The attention focused on standard specimens made of solid and cored clay bricks (Tab. 5.A). The mortar joint thickness changed between 10 and 12 mm (Tab. 9.B). The specimens were wrapped by CFRP and GFRP having 200 g/m 2 and 200-360 g/m 2 respectively (Tab. 5.A). One ply of CFRP and GFRP (Tab. 5.A) was wrapped around the specimens. The failure of specimens occured at increasing axial load, under displacement control at rate of 0.01mm per second. In Corradi et. al. [38] twentyfour masonry columns made of solid clay brick were tested under pure axial load. Two types of masonry were considered for the experimental program (Tab. 6.A). The geometrical characteristics were reported in the Tab. 11.B. The attention focused on four masonry specimens strengthened using several strengthening systems (Tab. 6.A). The solid clay bricks with dimensions of 245×120×55 mm 3 were used to assembly the masonry specimens. The mortar used was composed of Portland cement and hydraulic lime. The thickness of mortar was fixed to 8-10 mm. The specimens were wrapped with strengthening systems made of organic matrix (epoxy resin) and synthetic fiber with different mechanical properties (Tab. 6.A). Two types of fibers were considered for the passive confinement: carbon with high tensile strength (CFRP-HT) and carbon fiber with very high modulus (CFRP-VHM). In Krevaikas et al. [39] fortytwo masonry specimens made of solid clay brick were tested (Tab. 7.A) by means of pure axial load tests. For the analysis, six specimens were considered to compare the numerical results with the theoretical previsions. The brick element had dimensions of 55×40×115 mm 3 coupled with a mortar cement and lime based. The specimens were prepared according to several scale factors (1:1, 1.5:1 and 2:1) providing specimens with dimensions 115×115×340 mm 3 , 172.5×115×340 mm 3 and 130×115×340 mm 3 . The thickness of mortar was fixed to 10 mm for all specimens. Two types of strengthening systems were considered: GFRP and CFRP (Tab. 7.A). The specimens were wrapped with one, two and three plies of unidirectional CFRP sheets or with five plies of unidirectional GFRP system (Tab. 13.B). The fiber system was applied on the substrate using epoxy-resin. In Aiello et al. (2009) [40] thirtythree masonry specimens were tested under pure axial load. For the present study one specimen was considered due to the similarity with previous experimental programs (Tab. 8.A). The specimen was made of solid clay bricks having dimensions shown in Tab. 15.B. It was prepared starting from blocks with dimensions of 100×150×30 mm 3 . A mortar lime and cement based was used for the masonry specimen. It was wrapped with GFRP system with one plie and epoxy-resin (Tab. 8.A). The further information on the mechanical properties of constituents used in the past experimental programs previously outlined were reported in the Appendix A, from Tab. 1.A to Tab. 8.A. The geometrical characteristics of the specimens (cross-section, b × h and height, h), characteristics of strengthening systems (type of fiber, number of layers, n l , equivalent thickness, t eq ) and the experimental results in terms of unconfined, 0 m f and confined compressive, mc f strengths, are reported in Appendix B. The confined compressive strength, mc f can be normalized to the unconfined compressive strength, 0 m f , as shown in Appendix B. For each specimen, the effective confining stress, , l eff f has been assessed according to the two approaches previously discussed (Eqns. 13 and 18). The effective confining stress, , l eff f has been expressed in normalized form as shown in the Appendix B, from Tab. 1.B to Tab. 16.B. The additional results of the experimental tests are available in the original papers [33-40]. S TATISTICAL PARAMETERS FOR THE COMPARISON OF RESULTS he reliability of the mechanical models previously discussed has been tested by comparing the theoretical previsions with the experimental results. Some statistical parameters have been chosen to assess the reliability of the available confinement models. The comparison has been performed by means of some statistical parameters. The absolute approximation provides first information on the local reliability of the confinement models and it can be calculated as follow: