Seismic shear amplification in structural walls

Abstract

Earthquake resistant design of structural walls involves inhibiting brittle shear failure that would develop with the formation of plastic hinge at the base of the walls. During seismic action, recent studies demonstrate that maximum wall shear responses, during an earthquake depending on characteristics of the walls, are generally higher than the conventional code procedures, namely elastic analysis procedures, which can be attributed to the contribution of higher mode effects subsequent to the formation of plastic hinge at the base of the wall. In light of findings from analyses of structural walls, shear amplification factors have been proposed in Eurocode 8 EN1998-1 (CEN, 2004) to inhibit brittle shear failure occurrence in structural walls. Proposed relationships mainly depend on first mode period of wall and strength reduction factors. However, in Turkish Seismic Design Code, this issue has been handled by considering a constant base shear amplification of 1.5 regardless of first mode period and ductility level of the structural walls. Generic structural walls having four, eight, twelve, sixteen stories with different sectional properties have been analyzed in order to evaluate the dynamic shear amplification phenomenon. Responses of structural walls have been obtained through nonlinear analyses results such as base shear amplification factors, force and deformation responses. This study can be treated as an initial investigation for developing a sound procedure for shear design of structural walls in current code applications.