| Summary: | Recent research on jointed unbonded post-tensioned precast concrete frames has demonstrated their superior seismic resistance. Inelastic rotation generated during large earthquake motions is accommodated through gap opening and closing at the beam-to-column connections in the frame. By applying the principles of Damage Avoidance Design (DAD), a steel-steel armoured connection has been demonstrated to be effective in protecting the precast elements from damage. The re-centring ability of the unbonded prestressed post-tensioned system allows the building to return to its original undeformed position after the earthquake with negligible residual deformations. This research experimentally assesses the biaxial performance of the unbonded precast beam-to-column joint and simplifies the steel-steel armoured connection details in the joint. The experimental results of both quasi-static unidirectional lateral loading tests and biaxial lateral loading tests conducted on a 80% scaled unbonded jointed beam-to-column joint are presented. The performance of the proposed simplified steel-steel connection is assessed. A theoretical model is developed based primarily on rigid body kinematics and is validated using the test results. A formulation is also developed based on St Vennants' principle, to estimate the effective stiffness of the precast concrete beams under bidirectional rocking. Based on the experimental findings, improvements to the steel-steel armoured connection and joint details are proposed.
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