AIE是一个成立于2005年的加拿大组织，该组织的成立旨在及时快速地将能够为人类造福的工程领域重要的科学研究成果和创新技术在世界各地迅速传播，其主要的读者和受众是受过良好教育的工程和物理界的科学家、教授和学生。

AIE推广论文是经过国际专家顾问组高度筛选后确定的，AIE每周会在全球范围内工程领域发表文献中选出最多20篇的优秀论文进行特别报道，被选中发布推广的论文中选率少于千分之一，方向包括通用工程（航空航天、通讯、计算机、农业、工业）、化学、电子、机械、土木、纳米技术、材料、应用物理、生物医学工程。被AIE推广的论文需要具有特殊的科学重要性并能够被广大的科学读者所理解。AIE每月的阅读量高达65万次，其读者群35%为北美，33%为欧洲，30%来自亚洲。AIE除受到全球主要研究机构的关注外，也被全球排名前50位的工程公司所链接，用于跟踪突破性科技进展。

AIE专题报道中介绍郝际平：是中国西安建筑科技大学土木工程学院的教授，研究钢结构、竹结构和创新结构系统。他在多个与土木工程相关的国家委员会任职，是中国建筑金属结构协会主席。

田为峰博士研究重点是钢结构的稳定性和创新的抗震荷载系统，他目前的大部分研究是关于阶梯钢筋的屈曲和钢板剪力墙的后屈曲行为。钟炜辉博士的研究重点是钢结构的稳定性和钢结构的连续倒塌，特别是钢框架的抗连续倒塌性能。

阶梯柱框架：

(Frame with stepped columns)

附专题报道中英文原文

Buckling of stepped columns considering the interaction effects amongst columns

Significance

The frames used in mill buildings need to be robust enough to withstand the high crane loads. Usually, such frames are made of stepped columns with a lighter upper segment and a heavy wide-flange cross-section lower segment to accommodate the crane load. However, unlike prismatic columns, stepped columns exhibit considerably varying buckling behavior due to the effects of the non-uniform cross-section and the presence of axial (crane) load. To this end, the buckling behavior of stepped columns has drawn significant research attention. Since Timoshenko’s pioneering works in the 1970s, numerous theoretical and experimental studies have been carried out to calculate the buckling loads of different columns, establish their effective length factors and mechanical behaviors. These studies have satisfactorily addressed various problems associated with buckling behaviors and have been extended to multi-step and non-uniform columns. Following the previous studies, design protocols for stepped columns have been established and adopted.

Despite the progress, most existing studies concentrate on the behaviors of individual columns while neglecting the effects of the interaction amongst different columns, leading to inaccurate frame design. In an effort to address this challenge, a couple of hand manual hand-design methods have been developed to determine the effective length factors as well as buckling loads used in the design of stepped columns. Unfortunately, the existing methods are not suitable for some design scenarios, such as pitched-roof portal frames and multi-bay frames, since they ignore the inclination angles of the roof and interaction effects amongst columns. Therefore, developing a design method applicable to all design scenarios is highly desirable.

Although computer software and finite element modeling are quite popular, hand calculation methods are indispensable because they better comprehend the design process and mechanical behaviors of the columns. Therefore, Dr. Weifeng Tian, Professor Jiping Hao, Professor Weihui Zhong from Xi’an University of Architecture and Technology proposed a simple and accurate hand calculation method for evaluating the second-order effects and effective length factors on stepped column-based frames. This method accounts for the interaction effects amongst different stepped columns. The work is currently published in the Journal of Construction Steel Research.

The proposed method was based on the concept of negative stiffness that is applicable to different frame types. This concept was used to calculate effective length factors accounting for the interaction effects amongst different stepped columns. Next, the second-order effects were theoretically analyzed to develop expressions to determine the moment amplification and deflection factors. The authors also presented a practical method considering the influence of roof angles with stepped columns. Lastly, the practicability of the proposed method was validated through nonlinear static and eigenvalue analysis.

Results demonstrated the superiority of the proposed method in capturing the interaction effects of different columns and providing accurate estimates of effective length factors than the existing methods. A satisfactory estimation of the second-order effects with 0.6% and 3.4% differences in displacement and bending moment, respectively, was achieved. The slight inaccuracy of the bending moment was attributed to the simplification of the column deformation curve. In addition, the proposed method accurately accounted for the influence of roof angle, and it applies to a wide range of frame types

In summary, a simple and feasible approach for calculating effective length factors and evaluating the buckling behavior of stepped columns by considering the interaction effects of multiple columns were reported. The method enabled the authors to use stiffness factor values corresponding to lateral load coefficient to ensure the physical significance of the expressions and equations used to calculate the effective length factors. The results demonstrated the validity and practicability of the proposed approach. The authors further provided recommendations for improving the current design codes. In a statement to Advances in Engineering, authors said their study findings and the recommendations will enable engineers and fabricators to develop cost-effective and reliable designs for stepped columns in mill buildings.

Reference

Tian, W., Hao, J., & Zhong, W. (2021). Buckling of stepped columns considering the interaction effect among columns. Journal of Constructional Steel Research, 177, 106416.