DECOMPRESSION BASED ASSESSMENT OF ELASTIC AND CRACKED PRESTRESSED CONCRETE SECTIONS

The decompression threshold provides a useful reference for relating prestress, tensile stress and cracking in concrete sections. This study develops a reproducible assessment framework that combines classical kern theory with a normalized residual moment and compatible section analysis. Three modelling levels are compared: a gross elastic section with constant prestressing force, an uncracked transformed section with bonded reinforcement, and a locally cracked section with zero tensile concrete stress. A deterministic campaign considers rectangular, T-shaped and I-shaped sections with varying eccentricity, prestress, reinforcement ratios and concrete strength. Of 729 candidate configurations, 621 satisfy the initial tendon-stress filter, yielding 40,188 accepted loading states. Gross-section decompression moments differ from compatible elastic predictions by −2.80% to +2.05%, supporting their usefulness for preliminary threshold assessment. At a normalized loading coordinate of 0.50, gross-section curvature errors have a median of 3.19% and a maximum of 12.95%. At the first sampled cracked state, uncracked extrapolation underestimates local curvature by 21.32–85.92%. The normalized coordinate consistently aligns decompression and theoretical cracking while revealing the influence of geometry and reinforcement on subsequent response. These findings provide a practical basis for selecting the appropriate modelling level and separating threshold assessment from deformation prediction. The residual moment remains a loading indicator; cracked-section response requires the coupled contributions of concrete, passive reinforcement and tendons. The results describe local cracked sections and establish a foundation for future member-level assessment with tension stiffening and experimental validation.