Unbonded post-tensioning of face loaded URM cavity walls under semi-cyclic and dynamic loading

Abstract

An unbonded post-tensioning (PT) system installed into full-scale face loaded (out-of-plane) URM cavity walls using threaded rod and steel anchor plates spanning the cavity was investigated through experimental testing. Two different cavity wall typologies were tested: (1) two single clay brick leaves separated by an air cavity and (2) a two-leaf solid clay brick wall with an external single leaf brick layer separated by an air cavity. The PT walls were tested under semi-cyclic and dynamic shake-table loading. The tested PT system suppressed mid-span wall displacements, resulting in wall responses that were constrained well below geometric instability. Load-carrying capacity increased markedly up to 1500% when compared to cavity walls without post-tensioning. PT loads were varied to determine whether rod tension could be activated by vertical wall arching displacement. Upon preliminary analysis of the unbonded PT system, it was concluded that post-tensioning provides a cost-effective and constructible solution to considerably improve the performance of URM cavity walls.