Composite column critical temperature depending on its slenderness

Abstract

Stability of column, in fire conditions, depends on several parameters: type and dimensions of the section, height of the column, load intensity, material properties of constitutive elements, support conditions at the ends of the column, and so on. In normal exploitation conditions, it's relatively easy to calculate the critical buckling force of the column. With the increase in temperature, the mechanical characteristics of materials start to change, resulting in decreased bearing capacity of the column. Also, when the fire starts to spread, dilatations coused by the axial force and the temperature are in different directions. This thermal phenomenon will cause additional stresses in the column, depending on the degree of restrains at the ends of the column (elongation and rotation at the ends of the column). This paper analyzes the effect of temperature on the occurrence of critical buckling force of the columns. Knowing the critical buckling temperature helps in the proper design of composite columns, respectively, of their stability on buckling when the fire starts to spread. Nowadays, as the experiments of this type are very expensive, verified numerical methods for analysis of fire exposed structures are used. An example of calculating the critical temperature and critical buckling force of composite column with partially encased steel section, using the software SAFIR, is presented in this paper.

Keywords

• composite columns
• fire
• critical temperature
• buckling