Local ductility of steel elements under near-field earthquake loading

Abstract The paper tackles the influence of the near-field earthquakes on the available deformational capacity of steel elements through a global view, joining the results of the wave propagation theory with the one of the local plastic mechanisms. Different from the case of far-field earthquakes, where the structural behavior is dominated by cyclic loading, for near-field earthquakes the structural response is characterized by pulse loading produced by the seismic wave propagation along the height of the structure. Due to this fact, the structure response is dominated by the effect of the strain rate, thus reducing the local ductility and increasing the danger of fracture. After a presentation of the propagation theory applied to near-field earthquakes, the effect of the strain rate on the rotation capacity and on the fractural rotation of the beam elements, considering the fabrication type (rolled or welded) and temperature (room and low) conditions, is studied. It was revealed that the controlled flange buckling, as well as, the yielding ratio is the decisive parameters in order to avoid brittle failures. Finally, a novel representation about the damage produced during the Northridge and Kobe earthquakes due to seismic wave propagation is provided.

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