Assessment of failure probability of planar steel frames to plastic collapse by advanced structural analysis

Resumo

The current advanced analysis techniques for steel frames generally use structural analyses with
geometric and material non-linearities to capture the collapse strength of the steel frame. Advanced analysis has
the potential to result in more efficient designs, due to more accurate predictions of true strength of the structural
system. Unfortunately, even with the advanced nonlinear structural analysis method, the true strength of a steel
frame cannot be predicted with certainty because of ever-present uncertainties of the most significant design
variables, which are the properties of the material, the applied external loads and the geometric properties of the
cross sections of the steel profiles. Reliability methods allow the evaluation of the safety level of structures in
probabilistic terms, by the direct evaluation of the failure probability of the structural system. In the present
work, the First Order Reliability Method (FORM) was used to calculate the probability of failure of planar steel
frames to plastic collapse. The advanced analyses were performed using the program MASTAN2 and considered
the geometric nonlinearities and the inelasticity of the steel. The failure probabilities of numerical examples of
planar steel frames were evaluated and compared to other authors. The results of the numerical examples showed
that it is essential to obtain the probability of failure as part of the structural design to account for uncertainties
inherent to design variables in order to obtain safer structures.