Leaderboard

1. "Captive Columns" are in fact start of as unrestrained (long) columns which then become "laterally restrained", by walls coming into the side of them, normally in one direction. They are therefore captive in one direction. 2. Under seismic loading, the column is subject to lateral - horizontal forces in BOTH direction - so for this directional force this column length & depth (in each direction) needs to be checked. 3. For direction into the building, where the column is clear full height, no lateral restraint: 10'/1.5' 4. For direction along the building perimeter frame: 6'/1.5' 5. It important that structural engineers look at BOTH structural & non-structural architectural walls, beams, coming into the 'side' of the column, and thus making the column captive - and design accordingly. 6. One way to overcome this is to have the architectural wall run past the face of the column on the outside. This will mean cantilevering the slab sufficiently to have the wall sitting on slab. Wall detailing and tying to column detail would be be considered carefully in this case. 7. This Captive or Short column always attract much higher proportion of lateral earthquake loading due to their modified slenderness/stiffness, and will therefore need to be designed AND detailed accordingly to avoid its failure.