Abstract
The paper summarises the results of dynamic analyses of some single-stem and double-stem bridge piers responding to a range of earthquake ground motions, including both natural and synthetic earthquake records. The influence of foundation flexibility was modelled by an 'extended leg' analogy and by a more refined approach in which the soil is replaced by an equivalent spring system. A bilinear moment-curvature loop was assumed to model the plastic hinge behaviour. The curvature ductility factor demand of bridge piers with different foundation flexibilities was determined and compared with the rigid foundation case.
Highlights
Satisfactory performance of major highway and rail bridges under severe seismic attack is clearly of prime importance
Damage to rail bridges during designlevel earthquakes should not involve more lengthy repair work than necessary for ground-supported track. These considerations effectively imply better performance of major bridge structures under seismic attack than would be required for Class I buildings(D. This philosophy is inherent in the current Ministry of Works a n d Development (MWD) specifications for highway bridge design ^ which set higher seismic design base shear coefficients and design levels of ductility than specified for buildings capacity design approach is adopted to ensure beam hinging by specifying column flexural and shear strengths to be higher than the maximum input associated with beam hinges forming at maximum feasible beam strength
This paper examines the significance of foundation flexibility and earthquake characteristics to the ductility demands of bridge piers
Summary
SNYOPSIS The paper summarises the results of dynamic analyses of some singlestem and double-stem bridge piers responding to a range of earthquake ground motions, including both natural and synthetic earthquake records. The influence of foundation flexibility was modelled by an 1 extended leg[1] analogy and by a more refined approach in which the soil is replaced by an equivalent spring system. A bilinear moment-curvature loop was assumed to model the plastic hinge behaviour. The curvature ductility factor demand of bridge piers with different foundation flexibilities was determined and compared with the rigid foundation case
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