Using seismic isolation columns for retrofitting buildings with soft stories

Base isolation is known as en effective way to improve structural seismic response and reduce damages that may be caused to structures by earthquakes. The objective of seismic isolation is to decouple the structure from the earthquake motion input, preventing the structure from absorbing the earthquake energy. A new engineering solution for seismic isolation columns is presented in this study. It is aimed fi rst of all at retrofi tting existing buildings with a soft storey by replacing weak conventional columns, having low static and dynamic load carrying capacity, by the proposed ones. The idea is based on a well known friction pendulum principle. The proposed seismic isolation column is a kinematic system. Its main joint has high load carrying capacity as well as all properties of a three-dimensial hinge connection. No special materials are required for its manufacturing. No special lifting equipment is required to replace the conventional columns in existing structures by the proposed ones. An additional advantage is that manufacturing of such seismic isolation columns is relatively easy and does not require high accuracy and testing of each unit, like in other types of base isolators. A method for design of buildings, incorporating the proposed devices, was developed. The developed design procedure was applied for a multi-storey RC frame with infi ll walls in a numerical example. It was shown that using the proposed solution yields signifi cant improvement in structural response to earthquakes.