Robustness of Reinforced Concrete Frame with Respect to its Service Life

The effect of service life of a reinforced concrete building frame on its robustness parameters in the case of sudden failure of the outermost column has been investigated. The reinforced concrete frame of a philharmonic hall was chosen as the study subject. In order to evaluate its robustness, a relative robustness index, which is related to the parameters of the failure load for a system with and without initial local failure, has been utilized. Quasi-static modeling using the finite element method taking into account physical and geometric nonlinearity was performed as a part of the study. The physical nonlinearity of concrete, considering long-term operation of the structure, was accounted for by modified bilinear constitutive models of the material. Such models differed for elements with different stress-strain states in long-term operation. The parameters of the constitutive models were obtained using the integral deformation modulus proposed by Bondarenko. This approach has been employed to analyze the deformations and forces in the elements of the load-bearing system in the scenario of the outermost column failure. The curves for the percentage of destroyed elements of the load-bearing structure versus the parameters of the failure load have been plotted for the models with and without initial local failure of the outermost column, as well as for short-term and long-term operation. It is shown that the values of the failure load parameter and the relative robustness index decrease when the service life of the structure is accounted for.