This doctoral dissertation presents a novel numerical framework for the fire analysis of post-tensioned concrete beams with curved tendons. The framework consists of three sequential steps: (i) analysis of fire development in the vicinity of the structure, (ii) hygro-thermal analysis of the cross-section, and (iii) mechanical analysis in which the reinforced concrete beam and the prestressing tendons are represented as separate interacting components, allowing their mechanical response and potential failure to be assessed individually. The core contribution lies in the formulation and implementation of a highly efficient model for the structural deformation analysis (step iii), for which a new beam-type finite element formulation is proposed. Unlike 2D or 3D finite element models commonly used in the literature, this approach significantly reduces the number of degrees of freedom and thus the computational cost, while retaining high accuracy. Additional numerical efficiency is achieved by selecting strains as the interpolated unknowns, which prevents numerical locking often encountered in displacement-based formulations. By adopting exact material nonlinearity (enabling implicit or explicit consideration of transient and creep deformations) while linearizing the structural kinematics, the model gains further robustness. These features collectively enable efficient analysis of larger structural systems, rather than being limited to individual members. Validation against experimental studies confirms the model’s accuracy and numerical stability, while its low computational demand supports routine use on standard personal computers and facilitates its integration into engineering practice.
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