Leaderboard

Picked up columns are different from normal RC columns in that at their lowest point, these are located on (picked up from) top of a beam at some upper story of the building & transfer the load to the supporting beam, instead of trasferring it to a lower column directly. In the following image (showing elevation view of an ETABS model, where vertical purple lines represent columns, and horizontal lines represent beams), second column from left, is a picked up column. It is starting from top of a beam at first floor level, unlike all other columns stsrting from the 'base' i.e., ground level.

Base located at the ground in that case. Location of Base for Seismic Design.pdf

Good question. Seismic forces are actually inertial forces generated within a body in response to seismic acceleration at ground. When seismic ground waves (PGA) accelerate a building (Sa; spectral acceleration), the inertia of a building resist these accelerations generating inertial forces in the building. Inertial forces are nothing strange but the usual F=ma i.e. the product of mass and acceleration. In softwares, the joints or nodes are loaded with this F based on the mass attributed to the tributary area of that particular node x accelration of that floor. Like this, these forces are applied at each level like static procedures.