On the sensitivity of Finite Element results in the calculation of the lateral thrust for all-steel buckling-restrained braces

Abstract

The paper discusses the numerical analysis of all-steel buckling-restrained braces. These devices are designed to work in an inherently unstable regime, and their behavior is acutely sensitive both to any configuration detail in reality, and to any adopted parameter in their analysis. Their dissipative axial behavior can be reasonably well predicted by any suitable FEM model, if a good constitutive law is available. Nevertheless, it is shown here that an apparently accurate FEM calculation of the lateral contact forces, generated by the buckled core when it contacts the external containment profiles, produces results so sensitive to modelling details that they are practically devoid of an acceptable degree of accuracy. These observations might raise some doubts about the advisability of employing this type of bracing in normal engineering practice. In our viewpoint, a similar conclusion could be reached for any structural element designed to work in an unstable regime, unless the imperfections – of any type, including possible modelling details – could be explicitly taken into account, either parametrically or in a statistical way.