An Experimental and Numerical Study on the Behavior of High Strength Concrete Columns in Fire Subjected to High Restraint

The first part of this paper represents the results of an experimental research executed on 42 high strength concrete columns. The parametric study investigated high strength concrete columns under 3 loading levels 0.2, 0.4 and 0.6 subjected to high degree of axial restraint = 0.2 and exposed to two heating rates with a special attention directed to explosive spalling. The second part of the paper represents a three-dimensional finite element model of the reinforced concrete columns taking into account exposure to high temperatures. The effects of tension softening is included in the model and based on Hordijik, Cornelissen and Rienhardt curve. The concrete columns were modeled taking into account the embedded reinforcement and cracks formation and propagation using smeared cracks model which allowed a non-linear transient structural analysis to be conducted. The comparison of the results of the FE and the performed tests showed a reasonable agreement and a divergence in some cases due to concrete spalling. An assessment of the stresses generated in the high strength concrete columns under fire using the FEM model is also presented in the paper. The experimental and the FEM study showed that imposing axial restraint against concrete columns expansion may reduce explosive spalling of concrete during fire.