Cyclic response of precast column-to-foundation connection using UHPC and Ni[sbnd]Ti SMA reinforcements in columns

Abstract

Earthquakes are catastrophic natural events with a special impact on reinforced concrete structures due to the horizontal loads that they introduce into structures. To adequately resist an earthquake, a precast structure must have a high deformation capacity, dissipate energy in each earthquake cycle, undergo less damage and fewer residual deformations. To achieve all this, the behaviour of precast columns made with UPHC was herein experimentally analysed. Steel rebars were replaced with NiTi shape memory alloy (SMA) bars with superelasticity (SE) in the critical zone of the column-to-foundation connection. The NiTi SMA bars crossed the interface between the column and foundation. Two types of connection with the foundation were studied: smooth pocket type and protruding bar type. Columns were subjected to constant compression and a cyclic lateral load. Rocking behaviour was observed at the connection critical section. The use of advanced materials allowed a moment-rotation behaviour of the connection to be developed without any significant damage. Low residual deformations were observed while testing because of both the damage in UHPC was low and the superelasticity of the NiTi SMA bars.