Load bearing capacity of precast concrete elements after fire

This paper deals with the structural assessment after fire of several precast concrete elements, namely a pretensioned girder, a small beam, a hollow core slab and a roof slab. These elements were part of an industrial hall raised in the 1970's in Belgium, to be submitted intentionally to a real scale fire test. During the fire which approximated the ISO 834 temperature curve, temperatures were recorded inside the building and the elements. Most of the elements only suffered from limited spalling, except the pretensioned girder for which spalling depths up to 8 cm were noticed, resulting in naked prestressing strands and penetrations through the web. After the fire, the precast elements were visually inspected for spalling and submitted to a loading test up to failure. For a small pretensioned beam, the bearing resistance is calculated based on the residual material properties obtained from drilled cores and by taking into account the reduction in cross-section due to spalling. Additionally, the resisting bending moment is calculated based on the 500°C isotherm method. An adequate agreement is found between the experimental and calculated results