Inelastic seismic response of bridge drilled-shaft RC pile/columns

An analytical model based on a Winkler beam is used to represent the latera l force response of a reinforced concrete (RC) pile in cohesionless soil. A n inelastic finite-element analysis was performed on the structure, using a s the pile constitutive model the section moment-curvature relationship bas ed on confined stress-strain relationships for the concrete. Parameters var ied were pile head restraint (free and fixed head), height of pile head abo ve grade level, and soil stiffness. Linear, bilinear, and hyperbolic soil m odels were examined. The analysis showed that shear would be significantly underpredicted by an elastic analysis, as inelastic behavior moved the poin t of maximum moment in the pile shaft closer to the surface, thus reducing the shear span. Maximum moment depth in the pile shaft and plastic hinge le ngth were also shown to be strongly dependent on soil stiffness, and in the case of fixed-head piles, on abovegrade height of the superstructure. Line al soil models were shown to be adequate for most cases of pile/column desi gn.