PSI - Issue 44

Sara S. Lucchini et al. / Procedia Structural Integrity 44 (2023) 2206–2213 Lucchini et al. / Structural Integrity Procedia 00 (2022) 000–000

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(CV=8.4%). Notched prisms with a cross section of 150 mm (depth) x 40 mm (thickness) and a span length of 500 mm were tested under three-point bending according EN 14651. The flexural tests were performed under Crack Mouth Opening Displacement (CMOD) control by a 500 kN Instron ® testing machine. The mean residual strengths corresponding to CMODs of 0.5 mm, 1.5 mm, 2.5 mm and 3.5 mm resulted f R,1m =6.5 MPa (CV=31%), f R,2m =8.0 MPa (CV=26%), f R,3m =7.4 MPa (CV=26%) and f R,4m =7.0 MPa (CV=26%). The strength at the limit of proportionality (f L,m ) was equal to 4.2 MPa (CV=20%). 1.2. Specimen properties and test set-up The specimens tested in this research consisted in two one-way beams having a width of 1000 mm a height of about 2520 mm and a thickness of 200 mm. As shown in Fig. 1, a total of four vertical cuts (i.e., two per each specimen) were made on the “North wall” of the building by a concrete track sawing. Each cut was about 10 mm thick so that the beams were not restrained by the remaining portions of the “North wall” bounding the vertical sides of the samples.

Fig. 1. Specimen geometry and test set-up. (dimensions in mm)

The specimens were restrained along the top and bottom side by the top chord of the floor and the building foundation, respectively. The 30 mm thick SFRM coating was applied only on the outer side of the wall whereas the inner surface of masonry was not plastered. The continuity between the SFRM coating and the concrete foundation of the building was ensured by 8 mm diameter steel rebars located within the coating thickness. Considering the actual position of such rebars with respect to the vertical cuts, one may assume that the base cross section of the two specimens intersected a single rebar (Fig. 1). Two steel loading beams were placed both on the inner and the outer surface of the samples at approximately ¼ of the beam span length. The inner and the corresponding outer loading beams were clumped together by a couple of Dywidag bars in order to allow loading reversal. By a vertical distributor beam the horizontal load was equally shared between the loading beams. The total lateral load was applied by a 200 kN electromechanic jack joined to the distributor beam by a double-hinged connection provided with a load cell. The thrust jack was mounted on a reaction steel frame fixed to the strong floor. Both test walls were axially loaded by a compression stress of 0.1 MPa resulting from the gravity loads. The instrumentation used to continuously monitor the specimens’ response is shown in Fig. 1. The sensors designated as “HC#” and “HM#” were used to detect the lateral deflection of the wall. The potentiometers designated as “V#” were placed only on the outer surface to detect cracks on the SFRM coating. One of the two specimens was loaded monotonically in both directions whereas the other one was subjected to reverse cyclic loading. It was assumed that the positive loads and the related positive displacements corresponded to the outward deflection of the specimen.