ABSTRACT
This chapter shows that the minimum expected excess capacity under direct compression and reviews the parameters of expected excess capacity under combined compression and bending. The capacity of existing columns is one of the most common areas of concern during investigations and alterations of historic steel-frame buildings. Columns are often the key to analyzing the capacity of the existing frame, and therefore are the key to structural feasibility of alteration and adaptive reuse projects. The reinforcing of floor beams is a relatively simple process, affecting only the area in question, that can be carried out during a simple alteration, while column reinforcing can be quite difficult, and may require work from the altered floor in question all the way down to the foundations. The cost of column reinforcing can determine the economic viability of a proposed alteration. Engineers analyzing existing buildings therefore search for all reasonable methods to justify increased loading without reinforcing.
