Lumped-Plasticity Models for Performance Simulation of Bridge Columns

In bridge seismic design, a lumped-plasticity model based on a specified plastic-hinge length expression is used to estimate the ultimate displacement capacity. In contrast to current design guidelines, performance-based earthquake engineering (PBEE) requires assessment of damage for multiple demand levels. Implementation of PBEE of bridges therefore requires analytical methods capable of predicting bridge damage for multiple levels of earthquake demand. This paper evaluates models for PBEE of bridge columns, including new expressions for effective elastic stiffness, plastic-hinge length, and strain at onset of bar buckling. Data from 37 tests of large-scale circular bridge columns with post-1980 design details were used for model evaluation and development. The models were used to compute displacements and strains associated with various damage states and the resulting mean values and standard deviations. Findings indicate that the new model provides more accurate and precise predictions of damage in bridge columns than do existing models.