Dynamic experiments on post-tensioned beam-column substructures following the sudden removal of a single interior column

Abstract

Most experimental investigations about post-tensioned (PT) substructures have been conducted statically, neglecting the dynamic characteristic of progressive collapse. Dynamic performances of PT frame structures against progressive collapse are imperative to study under the sudden column removal scenario, which can reflect the actual progressive collapse more convincingly. This paper presents experimental programs on six half-scaled beam-column substructures, which were tested to evaluate dynamic responses after the sudden removal of a single interior column. During the tests, extensive instruments were installed in prescribed locations to record various dynamic responses such as displacements, loads, strains, and crack patterns. By comparison, the influences of post-tensioned strands (PTS) on the structural mechanisms of reinforced concrete (RC) frames against collapse were demonstrated. The findings cover the span–depth ratio of beam, bonded form of bonded post-tensioned strands (BPTS), and unbonded form of unbonded post-tensioned strands (UPTS). Experimental results highlight that the initial stiffness of RC substructures can be significantly enhanced by the PTS. Resistant mechanisms are mobilized to resist progressive collapse, such as compressive arch action and catenary action. The catenary action develops to resist progressive collapse if a larger span–depth ratio is applied in the design. Moreover, both UPTS and BPTS can increase the damping ratio of the corresponding RC, and the damping ratio of the PT specimen can reach up to 217.23% of that of the corresponding RC. And also, the proposed analytical model and theoretical equations can be well verified by the experimental results.