Continuous prestressed concrete beams are widely used in bridges and multi-span structural systems, where their behavior is primarily influenced by span continuity, moment redistribution, and tendon stress development. Numerical prediction of this behavior is challenging especially for unbonded and hybrid (a combination of bonded and unbonded tendons) systems involving steel and CFRP tendons. To address this need, this study develops and validates a finite element model (FEM) for continuous prestressed concrete beams incorporating bonded, unbonded, and hybrid configurations using both steel and CFRP tendons. The numerical framework conducted in ABAQUS and include nonlinear concrete behavior, tension softening, and appropriate constitutive models for steel and CFRP tendons. The proposed formulation integrates a trussed-beam analogy within FEM to enforce global deformation compatibility and to capture tendon stress development in unbonded tendon layouts. CFRP tendons are modeled as linear elastic to rupture, while steel reinforcement is treated as elastoplastic. Prestressing is applied through an initial strain approach to allow direct prediction of stress increment in unbonded tendons. The model is validated against two independent experimental programs involving fifteen continuous beams with varying cross sections, prestressing layouts, and a combination of steel and CFRP tendons. Comparison of load deflection responses and tendon stress increment curves shows that the FEM captures both the linear stiffness and nonlinear flexural behavior with good accuracy. Across all the beams, the model was able to reproduce the general flexural response trends, with minor discrepancies at higher load levels. The error levels for ultimate load, mid-span deflection, and stress increment in unbonded tendons are within acceptable engineering limits, confirming the model’s reliability. A comprehensive parametric study was performed to evaluate the effects of concrete strength, effective prestress level, bonded and unbonded tendon areas, non-prestressed reinforcement area, and span-to-depth ratio. The results show that increasing the concrete compressive strength enhances the beam load-carrying capacity, while also leading to higher tendon stress demand and increased deflection at ultimate. In addition, the area of the unbonded prestressing tendon has a greater influence on the beam load-carrying capacity than the bonded tendon area. The span-to-depth ratio was found to have a significant influence on the beam behavior, affecting stiffness, load capacity, and deflection.
Mana Humouda (Thu,) studied this question.