Experimental study on bonded and unbonded prestressed precast concrete beamcolumn substructures under penultimate column removal

Abstract

The collapse resistance of prestressed precast concrete frames relies on the tie force of the strands, but the influence of the bond conditions and layout of the strands remains unclear. This study investigates these factors through push-down tests on four beamcolumn substructures under penultimate column removal: one reinforced concrete specimen and three precast specimens (unbonded prestressed, bonded prestressed, and bonded with low-prestress parabolic profile). The results revealed that, compared to the reinforced concrete specimen, the precast specimens exhibited similar performance but were uniformly weaker under compressive arch action. Under catenary action, the precast specimens demonstrated significantly greater ultimate deformation and load-bearing capacity. The unbonded prestressed specimen failed due to wire rupture, impairing the flexural resistance of all its joints. In the bonded prestressed specimen, the bonded strand mitigated this issue but fractured prematurely. The bonded low-prestress specimen achieved the highest deformation and load-bearing capacity due to the enhanced deformation capacity of the low-prestress strand.