On the Analysis and Design of Steel Structure to Mitigate Progressive Collapse

Since Ronan Point tower local collapse in UK in 1968, progressive collapse phenomenon in structures attracted more attention for civil engineers all over the world so there were no useful researches and manual codes related to progressive collapse designing before. Progressive collapse occurs when loading pattern, boundary condition and resisting path changed, so critical elements undergo excessive unpredicted loading. We cannot omit reason of collapse as well as prevention of distribution of it that cause progressive collapse. Also, we cannot predict exact location of collapse beginning, so we should generalized design guides to whole or part of structures elements based on risk analyzing. Also we can use load carrying element removal scenario for critical elements. To prevent progressive collapse, structural systems require to having a well-distributed, redundant lateral load resisting system and ductile connections capable of undergoing large inelastic rotations without failing. There are some new guides and criteria for elements and connections to be designed to resist progressive collapse. Depends on required accuracy, importance of the buildings and acceptable risk level, the analysis methodologies ranged from linear to nonlinear with static and dynamic approaches. In this paper, codes and researches recommendations to resist progressive collapse for steel structures are presented, classified and compared. Also, applicable design methods based on codes and some retrofitting methods are summarized.