Cast-Iron-Column Strength in Renovation Design

Cast-iron columns were used extensively in the past, and many buildings remain standing with cast iron as part of the structure. Retention of the columns during renovation is often necessary for esthetics, historic preservation, and economics. During renovation, the live load required may change because of changes in occupancy, and the dead load may change due to floor replacement. Using the original column design assumptions, a typical interior cast-iron column in a typical late 19th century industrial building is analyzed using the original design loads, modern live loads and the original dead load, and loads after renovation. The original floor system analyzed is flat tile arches with cinder fill; the modern replacement floor system is lightweight concrete on composite metal deck. It is demonstrated that under certain circumstances, reducing the floor dead load can increase compressive stress and induce tensile stress in the columns in an unconservative manner.