Influence of the link overstrength factor on the seismic behaviour of eccentrically braced frames

The paper investigates the influence of the link overstrength factor on the seismic behaviour of eccentrically braced frames designed in accordance with capacity design principles. To this end, systems characterised by different level number and link length are designed according to the force-based approach, by either static or modal analysis. In order to correctly evaluate the ability of structures to develop global collapse mechanisms characterized by remarkable exploitation of the deformation capacity of links, incremental dynamic analyses are carried out with reference to either deterministic or random values of yield strength. While the first analyses are intended to lead to the conventional evaluation of the seismic response of EBFs, those referred to random values of yield strength are carried out to achieve a more correct verification of the capacity design principles and a deep comprehension of the sensitivity of the structural response to real strength distributions. On the basis of such results, the study also permits a critical analysis of the values of the behaviour factor generally proposed by building codes with reference to this structural typology.