Study on progressive collapse mechanisms of unbonded prestressed beam-column sub-assemblages

To study the load resisting mechanisms of unbonded prestressed concrete (UPC) structures with different tendon profiles (straight or parabolic profile) subjected to a middle column removal scenario, two 1 / 2 scaled UPC specimens and one reinforced concrete (RC) specimen were tested by pushdown loading regime. Test results indicate that the load resistance of the UPC specimens with straight or parabolic tendons is 95% and 189% higher than that of the RC specimen, respectively. However, the presence of tendons results in higher horizontal tensile reaction forces, which in turn cause more severe damage to the side columns of the UPC specimens than that of the RC specimen. The failure of the UPC specimen with parabolic tendon and the RC specimen is controlled by the fracture of the beam rebar whereas the failure of the UPC specimen with straight tendon is controlled by fracture of the tendon. Moreover, high-fidelity finite element (FE) models are built using LS-DYNA. After validation, the FE models are employed to conduct a parametric study. The parametric study results indicate that, for the same tendon ratio, the load resistance of the UPC specimen with straight tendon is 20% -58% higher than that of the UPC specimen with the parabolic tendon. The development of catenary action in the straight tendon occurs throughout the whole loading history, while the development of catenary action in the parabolic tendon begins when the displacement exceeds one beam depth. © 2023 Science Press. All rights reserved.