PSI - Issue 84

Sergio Belluco et al. / Procedia Structural Integrity 84 (2026) 607–614 Table 2 lists the values of , whose computation is described in detail in Belluco et al. 2023. Table 2. Probabilistic coefficient for transmission length of fib Model Code and Eurocode 2. 0 . 05 0 . 50 0 . 95 Φ (2.64) Φ (3.04) Φ (3.44) Release GSGSGSGSGSGS fib Model Code 2020 0.47 0.44 0.64 0.71 0.80 1.14 0.91 1.53 0.95 1.72 0.99 1.94 2 nd gen Eucorode 2 0.49 0.46 0.66 0.74 0.83 1.20 0.94 1.59 0.99 1.79 1.03 2.01 These coefficients are needed for computing , 0 . 05 (or 1 ), where the shorter the more onerous the SLS verification, and , 0 . 95 (or 2 ), where the longer the more onerous the ULS verification (Faleschini et al. 2023). Finally, Fig. 3 shows a comparison between the current and proposed formulations, computed considering ϕ = 15.2mm , f pi =1395MPa and f ( )=30MPa . Results show that for the lower fractile (SLS verifications), the code provisions are not conservative in case of sudden prestress release, while are very close to the target reliability length in case of gradual release. In contrast, for the upper fractile (ULS verifications), the code provisions are excessively conservative, particularly the fib Model Code 2020. For the EC2:2023 they are conservative for the gradual release and unconservative for the sudden one. 611

Fig. 3. Difference between current and proposed models for transmission length (adapted from Belluco et al. 2023).

3. Anchorage length 3.1. Current formulations

Identically to previous 2010 version, in fib Model Code 2020 the anchorage length is modelled as the sum of the transmission length (Eq. (1)) and the flexural bond length , i.e. the length required to anchor the additional tendon stress Δ due to external loads: = + , with = − = (6) that means scaling proportionally to the additional stress in the tendon due to external loading Δ f p , computed by subtracting the effective prestress after all losses f pe from the design tendon stress under the design load . Fig. 4 shows a representation of the physical meaning of the quantity involved in Eq. (6). Formulation of 2 nd gen. EC2 is similar in the concept, even if it is presented in a slightly different way: = + , with = 1 . 5 ⋅ 2⋅ 2 ⋅ 3 ⋅( − ) 1 ⋅ ( ) 1 2 ⋅ (7)