Non-linear finite element analysis of reinforced concrete beams with temperature differentials

Nonlinear finite element modelling is initially conducted to simulate simply supported reinforced concrete beams with temperature differentials over their depth (ΔT = 30 °C) that were tested at room (15 °C) and low temperature (−25 °C) during the experimental phase of this research program. Three-dimensional finite element models of the beams are developed to account for the geometry, material, loading, boundary conditions, and temperature profile. Then, the results of the nonlinear finite element analysis (NLFEA) are verified against the corresponding experimental results in terms of cracking loads, yield loads, ultimate loads, displacements, and cracking patterns. The validated NLFEA models are then extended to explore the response of the same beams with uniform temperature profiles as well as similar statically indeterminate reinforced concrete beams with and without temperature differentials. The numerical results show that the models are capable of predicting the ultimate strength of the beams at both room and low temperature. Additionally, the results show that indeterminacy (fixed-ends) substantially increases the ultimate strength of the reinforced concrete beams (up to 110%). The NLFEA results also show that low temperature (down to −40 °C) increases the strength of the beams without stirrups and decreases the number of the cracks on those beams even when temperature differentials are present. On the other hand, the strength and cracking pattern of the beams with stirrups are not affected when exposed to temperatures as low as −40 °C.