CONFINED CONCRETE COLUMNS WITH STUBS

The critical sections of columns in a framed structure subjected to earthquake loads are invariably adjacent to the beam-column/slab joints or the footings. External restraint provided by the heavy elements alters the behavior of the adjacent sections and may not always prove conservative. To simulate this behavior, 6 reinforced concrete columns were tested under cyclic flexure and shear while simultaneously subjected to a constant axial load. The variables in the test program were the amount of lateral steel, steel configuration, and level of axial load. From a comparison of the results with those from similar prismatic specimens tested earlier, it was concluded that the stub enhanced the adjacent section's flexural strength by more than 20%. The details of the study are described, and these and other findings are presented and discussed.