Thermal bowing of reinforced concrete sandwich panels using time-domain coupled-field finite element analysis

Abstract

Thermal bowing in concrete sandwich panels (CSPs), which is an undesirable deflection due to temperature differentials between inner and outer surfaces, has not been studied sufficiently and its effects are still not well understood. In this study, a transient thermal-mechanical finite element technique in ANSYS software, featuring two separate but interrelated time-domain simulations, a heat transfer and a non-linear structural, has been developed to study the bowing phenomenon in CSPs. The model predictions were validated by comparing with experimental data from full-scale panels in the literature subjected to heating on one wythe that produced an increasing temperature differential up to 30 °C. Validation included thermal bowing, slip and temperatures gradient. The structural component of the model was also validated by comparing with panels tested under flexural loads. The coupled model was then used to study the effects of several key variables that were not examined in the experiments, including cooling load, degree of composite action (kp), and wind loading combined with thermal loading. Results showed that very cold temperatures can result in bowing that exceeds serviceability limits and can cause compression failure in connectors. Bowing increased by 129% when kp increased from zero to 85%. Up to 50% increase in bowing was observed when adding wind effects to thermally determined bowing for the thermal range investigated in the parametric study.