A comprehensive model of fatigue for steel beams

Resumo

Steel beams may be subjected to cyclic loads and consequently damaged by the fatigue phenomena.
Concerning to identify and to monitor the crack initiation, the crack evolution and the subsequent failure of this
structures, in this paper it is proposed a model that allows the study of the fatigue phenomena, either for ultralow
and low cycles and high and ultrahigh cycles, considering both stationary and non-stationary fatigues. A new state
variable for the identification of the beginning of the crack propagation is introduced for each plastic hinge, which
is called the pre-damage variable. Its evolution law is based on Manson-Coffin law and also on the Basquin law.
Fundamental concepts of the Lumped Damage Mechanics (LDM) are also included. It allows the consideration of
the damage variable itself and its influence in the constitutive relationships. A new damage law is settled and takes
into consideration effects from both different types of fatigues. Appropriately, the crack closure effect is used
through the unilateral damage assumption. Finally, the accuracy of the model is its validation is done by a finite
element analysis (FEA) to predict the experimental behavior of tests of steel beam-column that are available in the
literature.