Higher-order modeling of a thin-walled beam with a welded multicell cross-section and its application to welding line optimization

• Published in: Computers & structures 2023-07, Vol.283, p.107056, Article 107056
• Main Authors: Choi, Seungju, Kim, Jaeyong, Jeon, Jaemin, Chang, Hongsuk, Chan Park, Jong, Young Kim, Yoon, Jang, Gang-Won
• Format: Article
• Language: English
• Subjects: Beam frame structure; Distortion; Higher-order beam theory; Multicell cross-section; Warping; Welding
• ISSN: 0045-7949; 1879-2243
• DOI: 10.1016/j.compstruc.2023.107056

•A new modeling method for a welded multicell thin-walled beam was presented based on a higher-order beam theory.•Partial welding lines in the axial direction of a beam can be accurately simulated by adopting constraint equations among sectional modes.•The optimized locations of welding lines can be found by using a genetic algorithm (GA).•The large number of analyses required for GA is not problematic due to the fast analysis of the proposed beam model.•Optimized welding lines are found near beam ends and joint regions because of large reaction forces and end effects.•Optimized welding lines on the top and bottom surfaces of a multicell beam do not generally overlap by complementing each other.•The proposed method is very helpful in reducing development time for new vehicle structures consisting of many multicell thin-walled beams. Thin-walled multicell structures observed in vehicle frames are partially welded to lower the welding process cost while maintaining their overall structural stiffness comparable to those of fully-welded multicell structures. A fast and reliable beam-based model for analyzing such structures is required in the concept stage of the design process. In this investigation, an analysis method for a thin-walled beam of a multi-cell cross-section partially welded along its axial direction is newly established using a higher-order beam theory (HoBT). Our approach uses the Lagrange multipliers to impose the partial welding condition along the common edges of multiple thin-walled closed sections using the three-dimensional field derived from a higher-order beam theory. The developed method in this study can be an accurate and effective alternative without full finite element analysis employing shell and solid elements. To find the optimal welding locations, we introduced binary design variables parameterized through their corresponding welding constraints to identify the status of welding or non-welding along a candidate welding line. A genetic algorithm is adopted to solve optimization problems. After establishing the analysis method and optimization technique, their validity was checked using double-cell and triple-cell sectioned beams and beam frame structures, including a bus structure. The stiffnesses of the structures with optimized partial welding lines (20%) drop less than 6% from those of fully welded counterparts.