PSI - Issue 84

Emeka John Ude et al. / Procedia Structural Integrity 84 (2026) 1294–1301

1296

Table 1. Concrete material properties from experimental campaign (Flores Ferreira et al., 2025) Property Value

Compressive strength

46.8 MPa

Tensile strength

2.48 MPa

Table 2. Reinforcement material properties from experimental campaign

Rebar diameter (mm)

10

12

14

20

26

fᵧ, av (MPa) fₜ, av (MPa)

526.5 530.2 623.7 628.2

507.7 627.5

555

522.7 634.7

677.7

For the experimentation, the two ends of four beams were subjected to monotonic loading following the scheme shown in Fig. 2 , resulting in eight tests in total, namely two initial capacity tests and six tests on beams strengthened with three different FRCM configurations..

Fig. 2. Loading scheme of the reference experiment Prior to retrofitting, all beams were preloaded to 270 kN to induce an initial damage state consistent with the original test program. The initial capacity tests on the reference specimen yielded peak loads of 537.96 kN (REF‑01) and 459.29 kN (REF‑02), with the reduced capacity of REF‑02 attributed to prior load ing damage and actuator eccentricity. While the original authors adopted REF‑02 when reporting the effect of FRCM strengthening, the present study uses REF‑01 as the reference because the developed FEM reproduces REF‑01 more accurately; moreover, a later n umerical study by the same research group also adopted REF‑01 as the baseline for their FEM campaign (Flores Ferreira et al., 2025). 3. Finite Element Modelling 3.1. Constitutive model of materials With respect to the constitutive model for concrete, a two-variable continuum damage-plasticity framework that separately accounts for tensile and compressive damage in concrete was employed. This framework is implemented using theASDConcrete3Dmodel, which characterizes concrete behaviour by incorporating separate damage parameters for tensile ( + ) and compressive ( − ) states. These damage indices govern the evolution of the effective stress tensor ( ) throughout the analysis increments according to the relationship = (1 − + ) ̅ + +(1− − ) ̅ − ( 1) Where , + and − represent the positive (tensile) and negative (compressive) stress components, respectively. The post-peak behaviour of the concrete model is driven by fracture energy, which dictates material softening and energy release during crack formation. The model uses a smeared-crack approach that normalizes the fracture energies (tension and compression) based on a characteristic crack-band width proportional to element dimensions. The softening curve is scaled such that energy dissipated in the softening zone equals the material's fracture energy. Reinforcements are modelled with OpenSees’ Hysteretic uniaxial material - a trilinear backbone with pinching, stiffness degradation and energy/ductility damage parameters.