PSI - Issue 84

Pavlina Lakatosova et al. / Procedia Structural Integrity 84 (2026) 1278–1285

1285

The analysis is performed only at the ultimate limit state, representing the condition just before structural failure. Crack development cannot yet be explicitly assessed. A practical recommendation is to limit reinforcement stresses to approximately 280 MPa to avoid excessive cracking. In the presented case, stresses reach up to 460 MPa, indicating that although edge splitting would not occur, excessive cracking would develop, as also reflected by the crack strain ε₁.

Fig. 14. Principal tensile strain and deformation

Fig. 15. Influence of triaxial stress state on the increase in concrete compressive strength

The method also allows visualization of the ratio between the maximum principal compressive stress σ₃ and the design compressive strength f _cd . This ratio quantifies the influence of triaxial stress on the increase in concrete compressive capacity. In this case, the compressive strength is increased by nearly 4.5 times due to triaxial confinement, as shown in Fig. 15. The equivalent stress σ _c,eq = σ₃ − σ₁ corresponds directly to the design compressive strength f _cd . 4. Conclusion The Compatible Stress Field Method, particularly its three-dimensional extension (3D CSFM), is a valuable engineering tool for assessing reinforced concrete discontinuity regions. Its ability to realistically capture the behavior of concrete and reinforcement in spatially complex details provides engineers with a higher level of accuracy and insight than conventional simplified approaches. References [1] IDEA StatiCa Detail – Structural design of concrete 3D discontinuities. IDEA StatiCa Support Center, 2024. [2] Kaláb, P., Design of D-regions in bridge structures using CSFM. Silnice a železnice 01/2024. [3] IDEA StatiCa Detail – Pull-out behavior of cast-in-place anchors with different embedment depths. IDEA StatiCa Support Center, 2024. [4] IDEA StatiCa Detail – Tri-axial stress: the active confinement effect. IDEA StatiCa Support Center, 2024. [5] IDEA StatiCa Detail – Columns subjected to high compressive loading: passive confinement effect. IDEA StatiCa Support Center, 2024.