Exterior post-tensioned band beam to column connections under earthquake loading

Although post-tensioned wide band beams are an extremely common structural floor system in Australia, very little is known about their performance under seismic loading. This study presents the results of two half-scale exterior post-tensioned wide band beam to column connections under seismic loading. The specimens were designed and detailed in accordance with current Australian practice to AS 3600-2009 to resist gravity loading only. The first specimen had tendons evenly distributed throughout the beam width, while the second specimen had the outer tendons moved much closer to the column side face. Both specimens performed similarly and torsional damage to the edge beam was critical. Both specimens achieved drifts of 3.0% or higher prior to significant loss in capacity, which is greater than the imposed maximum drift limit in most design codes. A 3D finite element parametric analysis was undertaken using the experimental results to calibrate the model. In addition to ensuring all reinforcement is properly anchored, this analysis confirmed the importance of the edge beam in the behaviour of the overall connection. Providing closed ligatures in the edge beam to the side face of the column was found to be critical to ensuring overall ductility of the connection, as well as minimising additional torsion placed on the edge beam by concentrating reinforcement within the column width where possible.