High-strength steel (HSS) is popularly used in large-scale high-rise and long-span structures owing to its superior toughness and strength properties. When using HSS plates as axial compression members, it is advisable to use high width-to-thickness plate ratio to fully utilize its advantages. In this configuration, the stability of the plates is the critical design factor as it controls the ultimate load of the HSS members. In most engineering cases, using HSS could potentially result in slender plates, especially when used as compression members. These slender plates are generally susceptible to the effects of local buckling and have attracted significant research interest.
Because of loading eccentricity or imperfections, box-section columns are usually under the impact of combined loadings. Moreover, the stability of the post-buckling behavior always permits pure local buckling. However, this often causes a decrease in the column stiffness, leading to local-global interaction modes. Therefore, it is important to study the local buckling behavior of these columns and develop effective and robust design models to predict the ultimate and buckling loads accurately.
While the HSS box-section columns with the same mechanical behavior in both directions is common in most practical applications, the lack of clear design guidelines for accurate prediction of their buckling behaviors compromises their practical applications. In recent years, a significant amount of research efforts has been devoted to theoretically and experimentally studying the buckling behavior of HSS box-section columns. Nevertheless, the local buckling of welded box-section columns subjected to axial compression is sparsely investigated.
Herein, Dr. Chao Cheng, Dr. Xianlei Cao and led by Professor Zhengyi Kong from Anhui University of Technology in collaboration with Dr. Bing Li and Dr. Zhimin Song from Henan University of Engineering carried out a series of experiments to investigate the local buckling behavior of 800 MPa HSS welded box-section columns under axial compression. Finite element analysis of different HSS-based columns was also conducted to examine the buckling characteristics of the plates. These experimental analyses considered the influence of various parameters, including steel grade, residual stresses of the plates and geometric imperfections. The work is currently published in the journal, Thin-Walled Structures.
The evaluation of the currently available design specifications for estimating ultimate and buckling loads of HSS welded box-section columns revealed that the GB50017-2017 and the AISC360-16 design codes currently used to predict buckling and ultimate loads, respectively, are slightly overestimated. In addition, Eurocode 3 and GB50017-2017 are underestimated for estimating the ultimate loads. To this note, more accurate and robust models were proposed and verified via reliability.
The authors showed the effectiveness of the proposed finite element model in predicting the ultimate load and buckling load of the welded HSS section columns with remarkable accuracy. Compared with the normal strength steel welded box-section columns, the influence of the residual stresses and initial geometric imperfections on the stress ratios and local buckling of the HSS welded column were much less effective. Moreover, the differences between the local buckling and post-buckling strengths of HSS increased more than that for normal strength steel.
In summary, an experimental study on the local buckling behavior of 800 MPa HSS welded box-section columns was reported. The proposed empirical models were verified and proved suitable for estimating local buckling and ultimate loads of welded box-section columns under axial compression. Section resistance safety factors were also proposed. In a statement to Advances in Engineering, Professor Zhengyi Kong, the corresponding author stated that their findings would contribute to advancing our knowledge and future studies of the buckling behaviors of welded box-section columns fabricated from other steel alloys.
Li, B., Cheng, C., Song, Z., Cao, X., & Kong, Z. (2022). Local buckling behaviour of high strength steel welded box-section columns under axial compression. Thin-Walled Structures, 171, 108677.