Effects of thermal creep of prestressed steel on post-tensioned concrete slabs in and after fire

Abstract

The effects of thermal creep of prestressing steel on post-tensioned concrete slabs in and after fire were investigated based on existing thermal creep model and calibrated parameters in this paper. A nonlinear finite element model was built up employing ABAQUS package, taking into account frictionless contact behaviour between prestressing steel tendons and surrounding concrete. The nonlinear material behaviour of concrete and prestressing steel at elevated temperatures was taken into account, where three material models for prestressing steel were adopted with or without considering thermal creep, and based on the model from EN 1992-1-2. The finite element model developed was verified against experimental results from the literature, showing that the model considering thermal creep was more accurate. Then the fire resistance period and responses of post-tensioned concrete slabs in and after fire were investigated based on the verified model. Ignoring thermal creep underestimated the fire resistance period but overestimated the residual tendon stresses. The model from EN 1992-1-2 achieved nearly the same effects as the model considering thermal creep in fire but might yield inaccurate evaluation of residual tendon stresses. The model considering thermal creep worked well under fire and in the post-fire conditions yielding reasonable predictions.