3D Finite-Element Analysis of Steel Moment Frames Including Long-Span Entrance by Strengthening Steel Cables and Diagonal Concentrically Braced Frames under Progressive Collapse

Progressive collapse in structures is considered a rare event. Yet, if it occurs, it may lead to disastrous human and financial loss. A significant item to study in examining progressive collapse relates to structures with relatively large spans. In such buildings, as the adjacent column collapses, maximum damage is caused to the entire structure. Therefore, in this study, six buildings of 16 and 31 m in height were, initially, subjected to nonlinear dynamic analysis upon the removal of a column. Shell elements were employed for concrete floors, and beam elements were used for beam members, columns, braces, and truss elements for cables, taking into account the nonlinear and geometric behavior of materials. The results of the numerical models were compared with the two experimental models, and a proper match was achieved. After the analysis of the primary structures, the two strengthening methods of braces and cables were employed by the removal of the column. The results of the study indicate that the use of cables and braces is able to significantly reduce the displacement of the node over the column by using an alternative-path method. Also, these two reinforcement methods are another reason for other structural elements to remain elastic.