IABSE Awards 2021

The International Association for Bridge and Structural Engineering (IABSE) is pleased to announce the Laureates of the IABSE Awards 2021.

The Outstanding Structure Award

The IABSE Outstanding Structure Award (OStrA) was established in 1998. It is one of the highest distinctions awarded by IABSE and recognises, in different regions of the world, some of the most remarkable, innovative, creative, or otherwise stimulating structures. Sustainability and respect of the environment is also an important factor. This Award recognises the most remarkable, innovative, creative or otherwise stimulating structure completed within the last few years. The Awards are restricted to a maximum of one Award per year. The Outstanding Structure Award Committee chaired by Naeem Hussain.

Winner ‘Bridge or Other Infrastructures’ category: Rose Fitzgerald Kennedy Bridge over the River Barrow

Outstanding Structure Award (OStrA) for ‘Bridge or Other Infrastructures’ category 2021 is presented to the Rose Fitzgerald Kennedy Bridge over the River Barrow, as part of the N25 New Ross Bypass project. ‘A landmark structure with three-towers and iconic profile that has pushed the boundaries for the span of a concrete extrados bridge.’

The Rose Fitzgerald Kennedy Bridge is one of the most iconic structures in Ireland. This three-tower extradosed bridge has two main spans of 230m each, the longest post-tensioned all concrete extradosed spans in the world. While there are longer spans in extradosed bridges, they all take advantage of a lighter steel composite section in the central part of the main span. The structure is part of the N25 New Ross Bypass project, which strengthens regional connectivity as well as local connections between the communities of Wexford, Kilkenny and Waterford in the south east of Ireland. At the location of the crossing, the River Barrow is 300m wide and is surrounded by a landscape of gently rolling hills. This modern, 21st century landmark has been designed to be sympathetic and complementary to its surroundings and environment, enhancing the quality of life in New Ross town which was previously subjected to frequent traffic congestion. The structure was conceived during the planning stage as a three-tower extradosed bridge with a central tower higher than the lateral towers.

Proportioned to the golden ratio in height and span distribution, with a truly shallow (less than 15 degrees) cable arrangement in a harp configuration, the bridge represents a formidable structural design and construction challenge.

Three towers following an asymmetrical configuration give the bridge a unique profile, with a shallow single central plane cable system in a pure extradosed structural system. The Rose Fitzgerald Kennedy Bridge has two main spans of 230m each which are the longest post- tensioned all concrete extradosed spans in the world to date. Despite the main span lengths, the towers are only 27m and 16m in height, while a deck slenderness of L/65 at the central section and L/35 and L/27 over the lateral and central towers was achieved. The structure comprises a single central plane of cables supporting a dual carriageway, leading to a 21.9m deck width. The deck is slender, with a 3.5m deep section (span/65) at midspan, 8.5m over the central tower (span/27) and 6.5m over the side towers (span/35). The tower height limits, with the central tower rising 27.0m above the deck level and the lateral towers 16.2m, result in all cables following the conventional extradosed harp arrangement with minimal spacing in the pylon (1m) and a shallow angle with the deck, which varies from 9 to 11 degrees due to the longitudinal slope of the deck.

Photo caption: Rose Fitzgerald Kennedy Bridge at night (23 March 2020). © Royston Palmer