Synopsis
A flagship Crossrail structure, the new station at Paddington will be constructed at the heart of one of London's most significant existing transport hubs. The opportunity to connect Crossrail with international air travel, national mainline and London transport both above and below ground, drives the need to develop an iconic piece of infrastructure worthy of such a location. This is a significant challenge given the position of the new station: below the existing taxi rank and busy Eastbourne Terrace, and within just 3m of Isambard Kingdom Brunel's 150 year old mainline station.
Since commencing design work on the station in 2009, URS has implemented fundamental changes to the original scheme. These will improve passenger experience, operational functionality, and reduce construction costs. The final scheme however, is not without challenge: construction planning to minimise the impact on road traffic; complex links to adjacent underground stations and interfaces with the existing above ground buildings and mainline station. There is also the construction of the main station box itself: 264m long, 25m wide, 25m deep, framed with diaphragm walls and constructed top-down using sizeable plunge columns. A significant design and construction constraint is that the Crossrail running tunnels are driven through the end walls after diaphragm walling and remain live during the excavation of the box until the penultimate slab is installed.
This paper discusses the architectural and structural engineering challenges encountered, and solutions developed, during the detailed design of the station. In particular it focuses on the changes introduced since the preliminary design stage, reviewing the driving factors for structural form and discussing the final design solutions that were implemented. This in turn exposes the requirement for the structural engineer in such an interdisciplinary project, to produce efficient solutions that respond to the various requirements of the integrated design team.