Axial compression behavior and design of perforated high-strength steel square hollow section stub columns

Perforations are frequently introduced in steel structural members to accommodate service ducts and reduce structural weight; however, their presence can significantly affect the load-carrying capacity of compression members. This study presents a numerical investigation on the performance of cold-formed high-strength steel (CFHSS) square hollow section (SHS) stub columns having double-sided perforations. Finite element (FE) models were developed and validated against available experimental results for non-perforated high-strength steel (HSS) SHS stub columns and perforated carbon steel SHS stub columns, due to the absence of experimental data for perforated HSS members. This limitation is acknowledged and discussed. A comprehensive set of experimental and numerical column capacities from previous studies and the present parametric analysis were used to evaluate the accuracy of existing codified and proposed design equations, including the Direct Strength Method (DSM). The comparisons show that most current design equations for perforated stub columns provide overly conservative and highly scattered predictions of column capacity for perforated stub columns. To further investigate these effects, a parametric study covering the influence of thickness, perforation shape, size, and height on column capacity was conducted. Among all parameters, the size effect was found to have a significant impact on the stub column capacity. Hence, a modified DSM design equation has been proposed for various perforation size ratios (i.e. diameter of perforation to the width of the column specimen) considering the previous test results and current FE column capacities. A tri-linear equation for the size ratios d/D ≤ 0.5 and 0.5 < d/D < 0.7 were separately proposed. The proposed design equation demonstrates improved predictive accuracy and reliability within the investigated parameter range and may serve as a useful basis for future development of design provisions for perforated high-strength steel tubular stub columns, subject to further experimental validation.