Stability of steel columns strengthened under preload: Numerical study with experimental validation

Abstract

Steel structures are often strengthened under a preload, which is defined as the existing load on the structure during the strengthening process. This study aims to understand the preload effect on the stability of strengthened steel columns. A numerical study on steel columns strengthened by bolted steel profiles under a preload is presented. Finite element (FE) models are developed and verified using experimental results. Furthermore, a parametric study is conducted with 242 FE models on parameters, including the preload, strengthened section properties, column length, and bolt configuration. The numerical results indicate that the preload effect on the ultimate load capacity can be beneficial, negligible, or adverse, ranging from −17% to 8%. The preload effect is found to be dependent on the preload level, section geometry, steel properties, and column length. Subsequently, a prediction model is proposed, wherein the preload effect is expressed as a function of the preload level and normalized slenderness. The prediction model is validated by existing experimental results and found capable of providing practically accurate predictions.