PSI - Issue 78

Maria Teresa De Risi et al. / Procedia Structural Integrity 78 (2026) 1151–1158 M.T. De Risi, C. Del Gaudio, G.M. Verderame / Structural Integrity Procedia 00 (2025) 000 – 000

1153

3

Mean yielding strength of 509 MPa and 604 MPa have been obtained from uniaxial tensile tests for longitudinal and transverse reinforcement, respectively. Mean concrete compressive strength (f c ) is equal to 12 MPa for columns and 21.5 MPa for the foundation block. Within the area of interest, column stirrups are 90°-hooked, as typical in obsolete RC buildings. The first specimen (AB) has been tested in its as-built condition. Considering the mechanical properties of adopted materials, a “pure shear” failure mode (without yielding) is expected for this specimen, since the plastic shear load is significantly higher than the expected shear strength (being the latter equal to 112 kN, according to variable inclination (θ) truss model prescribed by D.M. 2018 and Eurocode 8 -part 1-CEN 2005).

Fig.2. Geometric (dimensions in mm) and reinforcement details of column specimens.

The other two specimens (labelled SL and SH) have been strengthened with a different number of steel strips, all pre-stressed with the same nominal pre-stress level. “C1000” strip typology is adopted. Mechanical properties of the adopted steel strips are obtained based on uniaxial tensile tests (see Fig. 3): a “conventional yielding stress” (f 0.2 ) can be defined, as that leading to 0.2% of residual strain after unloading. The mean value of f 0.2 herein is 773 MPa.

f 0.2

0.2%

a) b) Fig.3. (a) Closing system for pre-stress application; (b) experimental uniaxial test and resulting constitutive relationship of steel strips.