Influence of internal defects of semi grouted sleeve connections on the seismic performance of precast monolithic concrete columns

To investigate the influence of internal defects of semi-grouted sleeve connections on the seismic performance of precast monolithic columns, four specimens of precast monolithic concrete columns with semi-grouted sleeves connecting reinforcement bars were fabricated, including one specimen (PC-D0) with no internal defect and three specimens (PC-D10, PC-D20, PC-D30) with 10%, 20%, 30% of internal defects respectively by controlling the length of anchor bars inside the semi grouting sleeve. The behavior of the columns as well as the failure modes, hysteresis loops, skeleton curves, degradation of rigidity, ductility and energy dissipation capacity were studied based on the data obtained by a low cycle reciprocating test. The results indicate that (1) the precast columns are all damaged by bending and the grouting layer of the assembled columns can be pulled apart easily; (2) the seismic energy dissipation capacity of the column without defects is higher than that of the columns with defects; (3) the existence of internal defects reduces the horizontal bearing capacity, rigidity, ductility and energy dissipation capacity of the assembled columns. However, the peak load for PC-D10, PC-D20 and PC-D30 reaches values respectively equal to 94%, 90% and 84% of that exhibited by PC-D0; (4) the energy dissipation capacity of the defective column with 30% of internal defects is significantly lower than those reached by other columns with defects, a feature that indicates that the influence of internal defects on the energy dissipation capacity of assembled columns is not linear. In conclusion, the results provide an insight into the influence of internal defects of semi grouted sleeve connections on the seismic performance of precast monolithic columns.