Seismic behaviour of grouted sleeve precast column to foundation connections: results applied to the direct displacement based design

In this paper we present the application of Direct Displacement Based Design (DDBD) to precast concrete structures with different column to foundation connections, whose structural response has been obtained through a set of experimental tests carried out at the University of Brescia, involving cast in place, pocket foundation and grouted sleeve solutions. The latter have a slightly smaller dissipation capacity while being able to ensure a similar ductility, compared to the other solutions; the main advantage is to limit the damage to the grout layer between the precast column and the foundation. The experimental data allowed to calibrate the moment-curvature hysteretic parameters used in the finite elements analyses carried out to validate the DDBD procedure. The analyses results of structures designed according to DDBD procedure show a lack of accuracy in the maximum displacement predicted by the design procedure; a better estimation of the structural yielding displacement and the development of a procedure, based on inelastic spectra analyses, to recalibrate the hysteretic damping equations available in the literature allowed to improve the maximum displacement prediction. This procedure is suitable for other hysteretic models calibration.