Robustness and Progressive Collapse of Structures

Robustezza e crollo progressivo delle strutture

In the recent decades, the natural and man-made disasters are known to be the cause of extensive human and socio-economic losses, particularly in modern societies and city structures. In this framework, the concepts of robustness and resilience of urban areas, as well as the idea of resilient community, have gathered the attention of the scientific research worldwide.

In the Structural Engineering field, the robustness is the capacity of a structure to avoid a major collapse due to the minor damage from accidental or malicious actions, and to show insensitivity to local failure. A robust structure is, therefore, able to redistribute loads when a load-bearing member suffers a loss of strength or stiffness, but exhibits a ductile, rather than the brittle, failure mode. Such a structure is not over-designed, because its ability to resist damage is achieved through global structural behaviour and failure modes, where the effects of a localised structural failure can be mitigated by the capability of the structure to redistribute the load elsewhere and the initial failures can initially propagate slowly. The Eurocode 1 (BS EN 1991-1-7) defines robustness as “the ability of a structure to withstand events like fire, explosions, impact or the consequences of human error without being damaged to an extent disproportionate to the original cause”, thus linking explicitly this concept to the disproportionate collapse one.

The structural progressive collapse mechanism is the failure of either a large percentage or the entire construction, which originates from the propagation of local damages in such a way that the structural system cannot withstand the main structural loads. Vehicular collision, accidental overload, aircraft impact, design/construction error, fire, gas explosions, bomb explosions, hazardous materials and so on are recognised as possible abnormal loads that can potentially trigger collapses similar to that of a row of dominos. The term progressive refers to a characteristic of the structural collapse behaviour. The progressive collapse can be propagated horizontally, starting from a structural bay to those adjacent to it, or vertically, when the collapse of a column interests the stories above it as in a situation of the so-called “pancake” collapse. A disproportionate collapse is that judged by the observer to be disparate to the initial cause. This is merely a judgement made on observations of the damage consequences resulting from the initiating events and does not describe the structural behaviour characteristics. For example, a collapse may be progressive but not necessarily disproportionate, if it becomes arrested after it develops through a number of structural bays. On the other hand, a collapse may be disproportionate but not necessarily progressive if, for example, the collapse is limited in its extents to a single structural bay, but the structural bays are large.

On the basis of the above premises, this session invites leading academic scientists and researchers to exchange and share their experiences and research results on all aspects of Structural Robustness Design and Progressive Collapse. As a premier interdisciplinary platform for researchers, practitioners and educators, the participants should present and discuss the most recent innovations, trends and concerns, as well as practical challenges encountered and solutions found in the field of robustness structural design. In particular, special emphasis will be devoted to the descriptions of various methodologies and current approaches (analytical, numerical, and experimental), developments and demonstrations of effective strategies for enhancing structural robustness, and the establishment of analytical guidelines and acceptance criteria for the designs of robust structural systems.