ABSTRACT
For retrofitting purposes, there is a demand to reinstate or increase the capacity of damaged or non-damaged columns. In addition to confinement techniques, section extensions to columns are often employed. Adhesion and mechanical anchoring over the interface are required to achieve the column’s full capacity. During the hardening process of the concrete, shrinkage of the newly cast extensions results in supplementary loading of the existing part of the column. The present work, based on the principles of composite action, considers one-directional enlargements, focusing on the normal forces in the column components and the shear flow acting on the interface. Additionally, fire action on an existing column that is enlarged on two opposite sides, is considered. It is demonstrated that optimizing bar locations in the new parts leads to a significant increase in fire safety.
