Engineering in Three Dimensions: Differences in Structural Behavior between Plane and Space Frames in Terms of Bending Moments

Resumo

With the continuous advancement of computational tools applied to structural engineering, it has become possible to represent structural behavior with greater accuracy, significantly contributing to the safety and the alignment of with real world conditions of building design. In this context, this study aimed to compare the structural behavior of plane (2D) and spatial (3D) frames through models developed using the Direct Stiffness Method. The first part of the study focused on the comparison of internal forces resulting from the application of vertical loads—representing self-weight and live loads—and horizontal loads due to wind action. This stage also included an evaluation of structural behavior under pinned connections using the DysTrucS software, for its efficiency in automatically generating load envelopes. In the second phase, a multi-story building was modeled under simultaneous vertical and horizontal loading conditions, with an emphasis on analyzing internal forces in specific structural elements. The results indicated significant discrepancies between 2D and 3D modeling approaches, with differences in bending moments reaching up to 13% in certain beams, and reducing to approximately 6% when considering moment envelopes. The literature indicates that three-dimensional modeling provides a more accurate representation of structural behavior, particularly in cases involving geometric asymmetry and significant lateral loads, while plane frames remain suitable for regular structures primarily subjected to vertical loading. This study highlights the importance of careful selection and application of modeling strategies in structural analysis and their practical implications for structural design