strengthening steel columns by reducing its effective length using R.C.encasing

Abstract

Columns are designed on specific loads transferred to them through beams, and as a result of the possibility of changing the function of the building or one of its parts, the columns and other structural elements are likely to be subjected to loads greater than the design loads, which calls for strengthening them in different ways. The bearing capacity of the columns is mainly related to their slenderness, which determines the structural type of column as long or short column, and thus determines the mechanism of its collapse either as a result of buckling or the bearing capacity of its material. In this research, a scientific framework was found for a common method of strengthening long steel columns, by implementing a concrete incasing to reduce the effective length of the column in different proportions. In the study, we relied on the MIDAS Gen program, where the column was modeled and studied with and without the presence of the concrete incasing. The study was carried out on a steel column of section UC 305 x 305 x 97, and two models of this column were studied according to the boundary conditions: The first model: a fixed steel column at the base and free at the top, with a height of 5m. The second model: a steel column hinged at both ends with a height of 10m. A concrete incasing with different heights was modeled, and the effect of adding this Incasing on each of the previous two models was studied.  The bearing capacity of the column increases with the increase in the height of the concrete incasing. The results of the study can summarize in: The impact of the concrete incasing is greater in the case of the column hinged on both sides than it is in the case of the column fixed from the bottom and free from the top.