Seismic Durability of Retrofitted R.C. Columns

摘要

The seismic performances of three retrofitted and one control, half scale, circular, reinforced concrete columns were studied. The columns were 10-ft. high, 18-in. diameter cantilevers. The longitudinal flexural steel was spliced to the foundation dowels just above the fixed base. A concentric axial load was continually applied during testing. The free ends of the cantilevers were translated to produce a maximum displacement of four times that necessary to produce yield in the longitudinal reinforcing steel. The loading was repeated with both positive and negative displacements in a quasi-static manner until the lateral forces required to produce these displacements approached zero. The measure of seismic durability used was the number of such cycles that a column sustained before losing structural integrity. The arrangement was intended to model that of bridge columns constructed during the 1960s. Three columns were retrofitted with prestressed, externally located circular hoops at intervals along the lower 4 ft. The spacing and size of these ties varied from column to column. The control column sustained less than two cycles before losing structural integrity; the retrofitted columns sustained a minimum of twelve cycles.