Influence of link models in the assessment of the seismic response of multi-storey EBFs

The cyclic response of links in eccentrically braced structures has often been modelled as elastic plastic with kinematic hardening or as elastic perfectly plastic. These models were based on the Euler-Bernoulli beam with concentrated flexural plastic hinges and considered ending springs to simulate the inelastic shear and flexural response of the link. Recently, the authors have proposed a simple but refined link model in which the response of the hinges is dictated by the uniaxial material model proposed by Zona and Dall’Asta for buckling restrained braces. This model takes into account both kinematic and isotropic hardening. Previous investigation has proved that the cyclic response provided by the proposed link model matches satisfactorily that obtained by experimental tests. This new model is considered here to assess the effectiveness of some common and simpler models in which the effect of the isotropic hardening is not taken into account explicitly. The comparison is made on multi-storey structures subjected to artificial accelerograms. The structures are characterized by different number of storeys and link lengths and are designed according to Eurocode 8. The investigation considers both global and local response parameters, namely maximum top-storey displacement, maximum transient and residual drifts and plastic rotations of links.