PSI - Issue 44

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Paolino Cassese et al. / Procedia Structural Integrity 44 (2023) 774–781 P. Cassese et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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2 Test Campaign An experimental program was carried out at the Department of Civil Engineering and Architecture (DICAr) of the University of Pavia in collaboration with the Construction Technologies Institute of the Italian National Research Council (ITC-CNR). Overall, four tests were performed on real scale cRCSP specimens representative of typical building walls: specimens were built in groups of two characterized by different shape and presence/absence of openings. The first series (W) was composed of two continuous squat walls with aspect-ratio (i.e., height-to-depth ratio) equal to 3/4. The second series (O) included two square wall (aspect-ratio of 1/1) with a central door-type opening. A detailed description of tests specimens and laboratory set-up is reported in the following sections. 2.1 Specimen Design and Material Properties Geometry and reinforcement details of the test specimens are shown in the Fig. 1. The continuous panels (W-series) present a rectangular in-plane shape of 400 cm × 270 cm, whereas the panel with a door-type opening (O-series) has an area of 300 cm × 270 cm and an opening area of 100 cm × 200 cm, as shown in Fig. 1. Each cRCSP wall was rigidly connected to two RC beams, made of ordinary concrete with compressive strength higher than 38 MPa: the top beam represents the slab beam and ensures uniform transfer of both gravity and lateral loads; the bottom beam acts as foundation beam and it is aimed at simulating rigid horizontal/rotation connection to the strong floor. The cRCSPs used for construction of tested walls are composed by two external wythes of reinforced concrete (RC) and a central core of EPS. All panels were characterized by the same thickness (t) equal to 18 cm, obtained as sum of two 4 cm thick concrete layers and one core with thickness equal to 10 cm. At the external ends of the wall, two full concrete portions with length equal to 4 cm were realized, in which two couples of D12 steel longitudinal bars were placed (generally identified as chains). Steel reinforcement of walls was represented by a continuous square mesh with diameter equal to 2.5 mm and spacing of 5 cm × 5 cm. Before concrete pouring, steel mesh was anchored to the steel cages of top and foundation RC beams by means of U-shaped steel stirrups with diameter 8 cm and height of at least 60 cm, spaced each-other at 50 cm. Concrete was applied by means of the so-called spritz-beton technique: the mix is sprayed on the external reinforcement cages to create the external layers. The results of uniaxial standard compressive tests (EN 12390-3, 2019) suggested a mean value of compressive stress (f cm ) equal to 26 MPa. Two types of steel were used in the manufacture of the specimens: one for anchorage bars at the panel/foundation joint and outer chain bars, the other for reinforcing meshes of external concrete layers. The latter served also as a support during the construction process. C7D type galvanized steel was used to this aim with an ultimate tensile strength (f t ) of 700 MPa. The remaining reinforcing bars were characterized by conventional B450C-type steel with nominal yield stress (f y ) of 450 MPa (NTC, 2018). The EPS core had density of 20 kg/m 3 and it was composed by wavy sheets with volume of approximately 112 × 270 × 10 cm 3 . The collaboration between the two external concrete wythes is ensured by means of steel connectors in the amount of 47 per square meter.

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Fig. 1. Geometry and reinforcement details for O (a) and W (b) panels.