Designing Robust Concrete Structures: An Introduction

About this course.

Robustness is the ability of a structure to withstand damage, an accident or an unforeseen event without collapsing to a degree that is disproportionate to the original cause. In other words, a robust structure is one in which a small, local problem stays local: if a single element is damaged or removed — by an impact, an explosion, a fire, a foundation movement, a gross overload or even a construction defect — the structure as a whole does not come down. This matters because the events that most threaten life are rarely the everyday loads a structure is routinely designed for; they are the rare, unexpected actions that no design can fully anticipate, and robustness is the property that lets a structure survive them.

It is important to distinguish robustness from ordinary strength. Strength is the capacity of a structure and its members to carry the loads specified in the design brief — the weight of the building, the people and furnishings, the wind, and so on. A structure can be entirely adequate in strength for all of those loads and still be fragile, because strength alone says nothing about what happens when something outside the brief occurs. Robustness is about that "what if": what if a column is struck by a vehicle, what if a support settles, what if a load far exceeds anything foreseen? A strong-but-brittle structure may fail suddenly and completely under such an event, while a robust one absorbs the damage and remains standing, even if locally injured.