Three resilient megastructures by Pier Luigi Nervi

Resilience, as the ability of a structure to withstand threats and continue to function, it is normally related to durability and performance to accepted standards over time. The resilience of a structure can be threatened by poor design, changes in the public's perception of style, the potential for a change-in-use and structural attack; catastrophic events such as fire, explosion or impact are usually considered the main threats for Resilience. In the contemporary built environment Resilience is considered increasingly important; it has, in fact, become one of the major design issues, especially for large, iconic or public and prominent structures: this has not always been the case. Following the Second World War, building designers faced the necessity to conceive projects within severe financial constraints, hence the proliferation of a low quality and limited life-span structures; buildings which were designed to be replaceable, cheap and perhaps anonymous. This was thought to be an effec-tive answer to quickly accommodate the large number of people moving towards the urban environment partly destroyed by the WWII. These very buildings now constitute the backbone of our urban scenery and although some still function adequately, many are perfect examples of structures which exhibit a lack of re-silience. Fortunately, there were a few designers who refused this post-war tendency and attempted to design lasting structures of quality: most of them were engineers. This is not a coincidence, engineers had less to do with the issue of providing residential accommodations and more with the erection of large structures which necessitated a higher quality control on materials and technologies: Pier Luigi Nervi was one of them. This work considers three large structures designed and built fifty years ago,in 1961, by the Italian engineer. The structures are the Bus Station at the George Washington Bridge in New York (USA); The Burgo Paper Mill in Mantua (Italy); and the Palace of Labour in Turin (Italy). All of these buildings are hybrid structures (concrete and steel), an unusual choice for Nervi that perhaps reects the design climate at the time; These buildings reacted quite differently to the events that have occurred over the past half century. One of the key factors to achieve resilience it is considered to be the quality of the buildings, which includes their ability to perform maintenance. The lack of which for whatever reason, this paper aims to demonstrate, will inevitably result in a weak performance in terms of resilience on the long run