Effect of Outstanding Flanges on Stress Concentration in Box Beam

Background of the research: A conventional box-type structure is generally used in constructing the core/shear wall, internal frame, and steel box girders. Tube-in-Tube with single and multiple tubes reduces the shear lag effect and lateral deformation in a tall tubular structure. Purpose: However, the present study focuses on the behavior of a modified form of the conventional box beam, i.e., a box beam with outstanding flanges. Thus, this study analyzes a box beam with outstanding flanges and compares the shear lag effect (Stress concentration) and lateral deformation with a conventional box beam. Methodologies: The minimum potential energy principle is applied to analyze the models and validated with the finite element results. Principal results: The transformation is observed to be reducing the shear lag effect at the web-flange junction and lateral deformations of the beam. In addition, the transformation also controls stress reversal. The modification demonstrated in the present study is stiffer than the conventional box-type structure as a core/shear wall or internal frame. Major conclusions and contributions to the field: This modification may be an integral part of tall tubular buildings producing significantly lowered stress concentration and lateral deformation. The present study is also applicable to strengthening steel box girders. It is possible to extend the bottom plate with the outstanding flange to increase the load-bearing capacity or strengthen the existing steel box girder. Therefore, the transformed box beam can be utilized as an economical alternative in constructing tall tubular buildings and retrofitting the steel box girder bridge. It is convenient and straightforward as there is no need to stiffen any part of the core/shear wall or internal frame. Additionally, there is no need to remove elements from the existing girder or alter its dimensions. Add the remaining flange by welding or bolting it onto the bottom flange to extend it. Limitation of the study and future research: A different assumption of stress function can be used in the flange and web when an orthotropic membrane theory is adapted to analyze the frame tube structure.