Abstract Civil structures are, normally, subjected to gravitational and thermal loads. The association of the effects of these loads should be the object of analysis when the loss of stability of the slender columns was verifying. In the case of reinforced concrete structures, temperature variations induce internal stresses in addition to gravitational ones since they are caused by the difference in the thermal properties of steel and concrete. Since the structure is a slender system, its stiffness was divided into two parts. In the first one, the properties of the concrete were introduced, including cracking and creep, doing the equations obtained at the time-dependent mathematical process. In the second, the geometric, the construction imperfections and the internal efforts mobilized by the temperature variation were considered. Additionally, strains and thermal loads were considered together. At the end, the values of critical buckling loads for different moments of interest were determined.

Abstract The ultimate limit state of stability by equilibrium bifurcation, the limit states for stress and strain resulting from this condition were evaluated for an extremely slender real structure of reinforced concrete, with geometry varying along its length. The aspects related to nonlinearities of the material were considered through the recommendations on NBR 6118:2014, from the Brazilian Association of Technical Standards (ABNT). In the analytical solution, developed for stability analysis, all elements of the structural dynamics present in the system were taken into account, including the column self-weight. The critical buckling load was then dynamically defined to different instants of time. Reductions of 70% for the modulus of elasticity and 59% for the critical buckling force were found in analyses performed from zero and five thousand days. It was also possible to obtain the induced stresses on the homogenized cross-sections and those transferred to reinforcement steel bars.