Effect of initial imperfections on the seismic performance of thin-walled steel hollow piers: A numerical approach.

This research investigates the influence of initial imperfections on the seismic performance of steel hollow piers, which are crucial components of bridges and other critical structures. The study focuses on two main types of imperfections: residual stresses and global geometric imperfections. The goal is to understand how these imperfections affect the pier’s ductility, maximum energy dissipation capacity, and overall behavior under uni-directional cyclic loads which simulates the seismic loading conditions. A numerical model was developed using finite element method (FEM), incorporating various imperfection profiles and tested under different loading directions. Parametric studies were conducted to observe the effects of imperfections within permissible limits, as well as beyond those limits. The results revealed that the residual stresses had a negligible impact on seismic performance. However, global geometric imperfections significantly influenced the performance when the bend exceeded the allowable limit, and loaded in line with the imperfection, which is particularly critical. The study shows that global imperfections lead to a significant reduction in maximum strength, with reductions as high as 24% when loaded in line with the imperfection and between 1% and 11% when loaded perpendicularly and these findings indicate that global imperfections play a dominant role in failure modes due to lateral cyclic loading.