EFFECT OF CONCRETE COVER ON AXIAL LOAD RESISTANCE OF REINFORCED CONCRETE COLUMNS IN FIRE

Abstract

The prescriptive rules in national codes specify that the fire resistance of reinforced concrete (RC) structures is proportionally dependent on the concrete cover to main reinforcing steel bars. However, performance-based design approaches developed from rational analyses of thermal and mechanical responses of materials and structures require more specific information of the relationship between concrete cover and the axial load resistance of RC structures, which may result in more economical design compared to those obtained from prescriptive rule. This paper introduces an analytical model that is capable of simulating the effects of concrete cover on the temperature-dependent mechanical properties of concrete and reinforcing steel used for the cross-sectional analysis for RC columns when subjected to fire. Parametric studies are conducted on prototype columns, based on which the axial load resistance of the column can be quantitatively determined at a certain time of a standard fire. The proposed analytical model is validated by a number of fire tests on RC columns and can be efficiently used for simplified assessment procedure of load resistance of RC columns in fire.

Keywords: Column; reinforced concrete; concrete cover; axial load; fire.

Received: August 16^th, 2016, revised: August 29^th, 2016, accepted: October 13^gh, 2016