Analysis and Simplified Design of Precast Jointed Ductile Connections

Abstract eng:
This paper describes simplified design tools for precast concrete hybrid system/connections developed during the PRESSS (PREcast Seismic Structural Systems) project, where unbonded post-tensioned tendons/bars are adequately combined with longitudinal mild steel or supplemental damping devices. In order to design the hybrid connections, which are subjected to a controlled rocking motion under an earthquake excitation, a section analysis procedure to evaluate the moment-rotation behaviour of the connection has been proposed in literature by the authors, and validated through a series of experimental tests. In this contribution, a parametric analysis on different section profiles is carried out in order to investigate the principal parameters affecting the moment-rotation capacity of hybrid sections. Either structural parameters, i.e. unbonded length of cables/tendons, mild steel, element length and section parameters, i.e. mechanical ratios of unbonded cables/tendons, mild steel, axial ratio have been considered in the parametric studies. On the basis of these results design charts to be used within a simplified design procedure have been developed. Furthermore an approximate closed-form solution for rectangular sections with lumped mild steel reinforcement has been derived and proposed. The two section analysis approaches are then implemented and compared within a worked example of a hybrid structural connection, designed according to a direct displacement-based approach.

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