Session Abstracts:
Session 7A
Structural Engineer
Stantec
Presentation Title: Quantifying the Effects of Seismic Loading History on the Collapse Behavior of Concrete Columns
Co-Author: Wassim Ghannoum; Adolfo Matamoros
Abstract: Experimental studies have indicated that the lateral and axial behaviors of concrete columns under seismic excitation can be highly dependent on loading history, particularly at high-damage states. However, due to cost limitations, most experiments on concrete columns have used fully reversed cyclic loading protocols, with only limited tests in the literature exploring the effects of loading history on behavior. Consequently, current modeling parameters and acceptance criteria for assessing seismic vulnerability are based on typical reversed cyclic loading protocols, which can make them overly conservative for short duration or near-field motions, and possibly unconservative for long-duration ground motions generated in basins or subduction regions. Due to lack of experimental data, continuum finite element models were constructed covering a relatively wide range of column parameters and failure modes to explore the effects of loading history on both lateral and axial degradation of concrete columns. A first set of over 30 column models were constructed to replicate tested columns and calibrated to those experimental tests, which were conducted under varying lateral loading protocols. Selected columns sustained flexural-shear, shear, and flexural modes of lateral strength degradation. Columns were selected to cover a range of shear stresses, axial loads, transverse reinforcement spacings and ratios, and longitudinal reinforcement ratios. All tested columns sustained axial collapse. Calibrated column models were then subjected to a series of loading protocols, including monotonic pushover, and non-symmetric ratcheting protocols. The effects of the lateral loading protocols on damage progression, strength, and deformation capacities are identified and discussed for the columns.