PSI - Issue 84

Biruk Yenehun Lemlem et al. / Procedia Structural Integrity 84 (2026) 1255–1263

1259

Table 1 Stochastic input parameters Parameter

Distribution Mean COV

Reference

Acting load – Dead (KN) Acting load – Live (KN) Concrete strength, fcm (MPa) Steel yield strength, fym (MPa)

Normal Normal

139

0.10 (Nowak & Collins, 2012) 0.18 (Nowak & Collins, 2012) 0.15 (Luyten et al., 2024) 0.054 (Luyten et al., 2024) 0.15 (Luyten et al., 2024)

58 38

Lognormal Lognormal

560

Resistance model uncertainty, KR (-) Lognormal

1.2

3.4. Monte Carlo Simulation Implementation For each realization in the Monte Carlo simulation, the acting stress in every STM element is first calculated. The safety factor of element i is then expressed as shown in Eq. (Errore. Nel documento non esiste testo dello stile specificato. .4) where σ Rd,i is the resistance stress of element i , σ Ed,i is the corresponding acting stress, and K R,i is the resistance model uncertainty. The overall system resistance is governed by the weakest element, defined as shown in Eq. (Errore. Nel documento non esiste testo dello stile specificato. .5). This expression reflects the principle that the failure of the most critical member controls the capacity of the entire STM. = , , ∗ , ( Errore. Nel documento non esiste testo dello stile specificato. .4)

( Errore. Nel documento non esiste testo dello stile specificato. .5)

= ∗ mi n( )

4. Results And Discussion 4.1. Development of Strut-and-Tie Models

Four STM configurations were developed to represent different internal load transfer mechanisms in the half-joint. These configurations were selected based on experimentally observed behavior, commonly adopted models in literature, and design guideline recommendations. STM A (Orthogonal Model) incorporates vertical hanger reinforcement as the primary load transfer mechanism, with predominantly vertical and horizontal force components. STM B (Diagonal Model) incorporates diagonal reinforcement as the primary load path, idealizing direct force transfer through inclined ties. STM AB (Combined Model) integrates features of both orthogonal and diagonal configurations, creating a hybrid load path that activates multiple reinforcement components simultaneously. This model introduces an additional node (N6) positioned to maximize capacity, consistent with the methodology outlined by Desnerck et al. (2018). STM C (Design Guideline Model) is developed in accordance with recommendations from the Design Manual for Roads and Bridges (Highways England, 2020) and explicitly includes the first stirrup as a critical tie element based on experimental findings by Desnerck et al. (2018). The development of each STM begins with identification of tie positions based on concrete cover dimensions and the