PSI - Issue 78

Sabatino Di Benedetto et al. / Procedia Structural Integrity 78 (2026) 1697–1704

1704

proposed by the Model Code 1990 for smooth bars, here extended to the case of a steel tube. The model was able to predict the ultimate bond resistance of the specimen with satisfactory accuracy. The study also highlights that the structural response is strongly influenced by the nonlinear development of shear stresses along the steel – concrete interface. Consequently, simplified approaches based on the assumption that the maximum bond stress is uniformly developed at failure, as commonly adopted in design codes, prove to be inadequate for accurately estimating the actual bond resistance in such configurations. Finally, a parametric analysis was carried out by varying the tube diameter and the concrete strength class, revealing that if the bond stress coefficient of 0.3 from the Model Code 1990 is reduced to 0.24, the assumption of a uniform bond stress distribution along the tube length still enables an accurate estimation of the bond resistance of steel micropiles embedded in concrete plinths. References Bryson, J. O., Mathey, R. G., 1962. Surface condition effect on bond strength of steel beams embedded in concrete. J. Am. Concrete Inst., 59(3). Cao, X., Xie, X.D., Zhang, T.Y., 2023. Bond-slip behavior between high-strength steel tube and ultra-high performance concrete, Structures, Elsevier, 47, 1498 – 1510. CEN. Eurocode 2: Design of concrete structures – Part 1-1: General rules and rules for buildings (EN 1992-1-1:2004). Brussels: European Committee for Standardization, 2004. CEN. 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