Tension chord model for <scp>CFRP</scp> ‐prestressed structural concrete

Abstract This paper introduces a mechanical model for steel‐reinforced concrete prestressed with bonded CFRP rods and presents the findings of an experimental campaign conducted to validate the model. The study is part of a project aiming at developing a railway bridge system in Switzerland that utilizes stainless steel reinforcing bars combined with pretensioned sand‐coated CFRP rods to (i) maximize durability and (ii) achieve reasonable plastic deformation capacity despite the inherent brittleness of the prestressing material. The proposed Tension Chord Model for CFRP‐prestressed Structural Concrete (TCM‐cfrp) extends the established Tension Chord Model for Structural Concrete by introducing a constant, rigid‐perfectly plastic bond shear stress‐slip relationship between concrete and CFRP, allowing for computationally efficient closed‐form solutions to determine the load‐deformation behavior, crack widths, and reinforcement stresses. The validation against the experimental results reveals (i) satisfactory model predictions of the mean strains, the stresses at the crack and the crack widths and (ii) insensitivity of the structural behavior on local bond shear stress distributions, thus supporting the simplification of assuming constant bond shear stresses. The TCM‐cfrp is capable of capturing all stress states in tension chords of railway bridge girders and other structural elements relevant for serviceability, ultimate, and to some extent, fatigue limit state verifications. The limitations of the model lie in (i) the simplified treatment of the crack formation process, overestimating deformations but underpredicting crack widths prior to stabilized cracking and (ii) its inability to realistically model local strain and stress distributions between the cracks, which is however of limited relevance for most structural engineering purposes.