Detailed evaluation of the ultimate flexural states of beams in unbonded precast prestressed concrete frames

Abstract

To guarantee the ductile and self-centering behavior of unbonded precast prestressed concrete (PCaPC) frames, a macro-model that accurately reflects the seismic behavior of cruciform unbonded PCaPC subassemblages was built using a theoretical approach in this study. By employing this macro-model, the relation between the strain states of the tendons and concrete in an arbitrary beam section was established. Based on this relation, iterative and simplified evaluation methods for the beam strength and deflection, as well as the strain of the tendons, in the ultimate flexural state were proposed. The accuracy and effectiveness of the proposed methods were verified through comparison of their results with those obtained in previous experiments and with other calculation methods. The proposed methods proved capable of providing more accurate evaluations of not only the ultimate strength and deflection of a beam, but also the corresponding strain of the tendon and are thus more effective than the previous calculation methods. In addition, the proposed simplified methods are sufficiently practical to be employed for design. By using the proposed methods, both the damage tolerance and self-centering performances of unbonded PCaPC frames can be achieved with higher accuracy.