Seismic Design of Bridges to Relate Ductility and Sway


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Title: Seismic Design of Bridges to Relate Ductility and Sway

Author(s): Ergin Atimtay

Publication: Special Publication

Volume: 128


Appears on pages(s): 1243-1256

Keywords: abutments; bridges (structures); ductility; structural analysis; earthquake-resistant structures; moment-curvature relationship; piers; structural design; superstructures; Design

Date: 11/1/1991

A design method has been proposed that considers the interaction of the superstructure with the abutments. The superstructure sways freely under moderate intensity ground shaking. At this stage, the piers are considered to be taxed at 70 percent of their capacity. Under the design earthquake, the piers hinge and bang against the abutments. The soil passive resistance behind the abutment back wall is mobilized, which is considered as elastic springs in the computer model. The sway of the superstructure is carefully monitored to limit the displacement of the abutment to avoid stability problems. The maximum resistance of the soil behind the backwall is also limited. Since the maximum longitudinal sway is known, the demand on ductility of the pier is quantified by plastic analysis. This demand is checked against the realistic thrust-moment-curvature relationship of the pier. Iterations may be performed to satisfy the constraints and achieve acceptable results.