Stochastic cohesive zone modelling of imperfect adhesive interfaces in TCC beams under different loading configurations

This study presents a stochastic cohesive zone modelling framework to investigate the mechanical performance of adhesive interfaces with spatially variable bonding conditions in timber–concrete composite (TCC) systems. The proposed framework accounts for uncertainties associated with adhesive imperfections by introducing stochastic variations in the distribution of bonded and weakly bonded regions along the interface. Two loading configurations, including uniformly distributed loading and four-point bending, are investigated to evaluate the influence of bonding reduction under different stress distributions. A uniform stochastic bonding approach is developed to represent randomly distributed adhesive imperfections and is applied to both loading configurations. For the four-point bending configuration, an additional zone-dependent stochastic approach is introduced that divides the adhesive interface into shear- and bending-dominated regions. The adhesive behaviour is described using a traction–separation cohesive law, while a deterministic hash-based stochastic algorithm with block-based spatial correlation is implemented to generate reproducible bonding fields. The results demonstrate that the structural response depends on both bonding ratio and adhesive distribution. A bonding ratio of approximately 50–60% maintains a stiffness-based composite efficiency equivalent to the fully bonded upper bound under uniform loading, while a critical shear bonding threshold of approximately 50% is identified under four-point bending conditions. These thresholds are configuration-specific and may vary with different structural geometries, material properties, or loading arrangements.