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The Structural Engineer

All the articles from the July 2018 issue - a special issue on 'Structural engineering for the Elizabeth line'.

Publish Date - 2nd July 2018

Author – Various

Price – Free

The Structural Engineer

There is something special about megaprojects that brings out the best in engineering design and construction. It could be that the longer-term durations for the planning, design and build phases allow more measured and thoughtful decision making; it could be that the weight of public exposure and expectation creates an added incentive to succeed; it could be that the prestige of being part of the programme attracts the best teams in the best organisations; it could be that the extended schedule nurtures a team spirit and a collaborative way of working that is difficult to achieve in a typical shorter-term project.

Publish Date - 2nd July 2018

Author – G. Masterton

Price – Free

The Structural Engineer

Congratulations to all the winners of the Institution’s People and Papers Awards 2018, which were presented at a luncheon held at Church House in Westminster, London on Thursday 7 June.

The Awards recognise outstanding contributions to structural engineering and to Institution life, through innovative educational initiatives, papers published in The Structural Engineer and Structures, lectures, regional group activity, and much more. They cover the whole range of Institution life, from outstanding young professionals to those recognised for a lifetime of achievement and service.

Publish Date - 2nd July 2018

Author – Various

Price – Free

The Structural Engineer

Michael Dickson, Past President of the Institution, passed away on Monday 28 May 2018 after a battle with cancer. An inspirational man in so many ways, he was one of the great leaders, thinkers and mentors in our profession.

Publish Date - 2nd July 2018

Author – N/A

Price – Free

The Structural Engineer

I am pleased to have been asked to contribute a foreword to this timely publication. As work on the Crossrail programme comes to a conclusion and we pass the baton of largest infrastructure project in Europe to High Speed 2, this is a valuable collection of insights into the design and construction process for the structural elements of the programme. Crossrail has always been committed to sharing lessons learned, embodied most effectively in our Learning Legacy initiative, through which we have published many examples of insight and good practice on a dedicated website.

Publish Date - 2nd July 2018

Author – C. Sexton (Crossrail Ltd)

Price – Free

The Structural Engineer

The Elizabeth line, due to open in December 2018, crosses London from west to east. The Crossrail project to construct the Elizabeth line has seen 21km of twin-bored tunnels constructed under central London, with eight new stations built on this section.

The damage assessment and monitoring carried out comprised a significant element of work in terms of the resources involved, both human and financial. The background to this work was the experience from a number of tunnelling projects in London, probably most significantly that from the London Underground Jubilee line extension. While all assets along the alignment were subject to the same process, the impact of the works around the stations and shafts was calculated to be greater than along the bored tunnels, and the extent of instrumentation and monitoring was correspondingly higher. Both automated and manual methods were used, with instrumentation installed and readily visible on many buildings in these areas throughout the duration of the works.

This paper looks at the damage assessment and monitoring of buildings around the stations, focusing in particular on the new station at Tottenham Court Road. It also provides an overview of the two very different tunnel construction methods used on the project – the so-called tunnel boring machine (TBM) and sprayed concrete lining (SCL) methods – and describes how these lead to the ground movement that is the principal source of potential damage to the buildings.

Finally, the paper considers briefly some of the lessons learned and how these might be applied to future urban tunnelling projects.

Publish Date - 2nd July 2018

Author – D. Lazarus (Arup) and H-I Jung (Arup)

Price – Free

The Structural Engineer

Farringdon is one of eight new underground stations being built in central London for the Elizabeth line and will be one of the key interchange stations on the new line. Upon completion, over 140 trains per hour will pass through the Farringdon interchange, making it one of Britain’s busiest stations. With Thameslink, Elizabeth line and London Underground services, it will be a key link in bringing passengers from outer London to the business hubs in the City and Canary Wharf. The station will also provide direct rail links to three of London's five airports.

Farringdon Elizabeth line station comprises two platform tunnels, each 245m long, between new ticket halls over 300m apart. Each ticket hall has been designed to accommodate future oversite developments.

This paper discusses the structural engineering challenges encountered during design and construction of the two ticket halls on constrained sites surrounded by existing transport infrastructure, utilities and historic buildings.

Publish Date - 2nd July 2018

Author – G. Kumar (TfL Engineering, ex-AECOM) and D.Sharples (AECOM)

Price – Free

The Structural Engineer

The new Elizabeth line station at Custom House was a unique opportunity for design and construction. It is the only above-ground station on the central section of the line and will welcome millions of visitors to London’s largest conference centre, ExCeL, as well as providing vital connections for the Borough of Newham.

A joint team from Crossrail Ltd, Atkins, Arup, Allies & Morrison, and Laing O'Rourke collaborated to develop the striking station design, creating a beacon for both the Elizabeth line and the local community. Faced with many constraints, a ‘kit of parts’ strategy was developed for Custom House’s construction, including prefabricated and standardised components.

This approach – where much of the station was built off site – minimised workon site, drove down programme times and costs, and reduced the impact on the local community. The approach also led to Custom House’s excellent health and safety record – one of the best of any Elizabeth line station to date.

Publish Date - 2nd July 2018

Author – E. Newman-Sanders (Atkins), R. Smiley (Atkins)

Price – Free

The Structural Engineer

The design of Bond Street Elizabeth line station has evolved over 10 years of design and construction work. This article explains how the design has developed over this timeframe and how the independent designs for two clients were successfully delivered on the same site. It will discuss how the site constraints have informed the design, how the station was designed to be constructed and how it was ensured that the design has been assured throughout.

Publish Date - 2nd July 2018

Author – R. Paul (WSP)

Price – Free

The Structural Engineer

The new Elizabeth line station at Tottenham Court Road, delivered by the Crossrail programme, has been an exercise in interface management as well as a feat of engineering.

This paper describes the design carried out by the Arup Atkins Joint Venture (AAJV) under contract C134, principally of the Western Ticket Hall box. Nestled in Soho, this was developed within a dense urban grid and the constraints of a residential oversite development above.

The team worked closely with London Underground Ltd's engineers at the Eastern Entrance, which was delivered as part of London Underground’s own station upgrade works.

The tunnel for the eastbound Elizabeth line passes through the Western Ticket Hall box, which also provided construction access for the sprayed concrete-lined platform and concourse tunnels. Access dates to the site meant that there was insufficient time to complete construction of the box before the arrival of the tunnel boring machine (TBM). Consequently, the need to complete the excavation became critical and the team adopted a bottom-up construction sequence for one of the deepest open shafts ever excavated in central London. The box, formed of elements of diaphragm walls and raft, was constructed before the TBM arrived, and the remaining internal elements completed afterwards.

Publish Date - 2nd July 2018

Author – J. Plant (Arup), S. Frost (Geada) and S. Roberts (AECOM)

Price – Free

The Structural Engineer

Tottenham Court Road Elizabeth line station is a new station located in the heart of London, adjacent to Oxford Street, being delivered as part of the Crossrail programme. The station is expected to accommodate more than 200 000 passengers every day when it becomes operational in December 2018. The station is of paramount importance due to its strategic location, interchange with the London Underground and future link to Crossrail 2.

Tottenham Court Road consists of two entrances on the east (Goslett Yard Box) and west (Western Ticket Hall) sides of Soho Square, each of which has a ventilation tower equipped to ventilate the 250m long new platforms and running tunnels located 25m below ground. The ventilation towers are two of the largest overground structures on the entire Crossrail project, and presented a vast array of challenges due to their locations as well as their technical complexity.

Following the award of the contract to Laing O’Rourke, discussions were held about changing the design of the superstructures to precast concrete. However, due to the design process that would have been required to alter the concept, and lead time for bespoke precast elements, there was not sufficient time to alter the construction methodology. Therefore, a traditional in situ concrete approach was used. In fact, due to the precise planning and coordination of this approach, it resulted in a more economical solution than the precast option.

Publish Date - 2nd July 2018

Author – J. Maltezos and T. Harman (both Laing O'Rourke)

Price – Free

The Structural Engineer

The St Giles Circus project involves the £150M redevelopment of a central London site adjacent to Tottenham Court Road Station. The structural and civil engineering design was undertaken by Engenuiti, with geotechnical advice from Donaldson Associates. The development includes leisure, retail, commercial, residential accommodation and a boutique hotel. Above ground, the building incorporates an immersive multimedia urban gallery hung from two-storey steel trusses cantilevered over Tottenham Court Road Station. Below ground, a 2000-person basement venue for live music and events is being built 6m above the eastbound Elizabeth line tunnel, adjacent to the London Underground Northern line platform tunnels and above the inclined cut-and-cover concrete box housing the escalators that provide public access to the Northern line.

Publish Date - 2nd July 2018

Author – C. Fussell (Engenuiti)

Price – Free

The Structural Engineer

Canary Wharf was the first station on the Elizabeth line to be constructed, and the first to be let as a design-and-build contract, with developer Canary Wharf Group. Innovative design and construction techniques enabled the station box to be completed four months ahead of the development programme. Construction of the Crossrail Place retail and leisure oversite development (OSD) proceeded concurrently with that of station. The OSD included a number of features aimed at increasing future flexibility for the developer and tenants. A timber gridshell roof completes the development, partially covering a large roof garden that is open to the public. The OSD opened in May 2015, nearly four years ahead of the planned station opening.

Publish Date - 2nd July 2018

Author – T. Worsfold (Arup), M. Bryant (Canary Wharf Group) and J. Crack (Canary Wharf Group)

Price – Free

The Structural Engineer

This paper covers the engineering design of the platform edge screens for five Elizabeth line tunnel stations in central London. Full-height platform edge screens are a signature feature of the Elizabeth line’s station platforms, and their design presented many challenges. To gain maximum uniformity, the edge screens were developed as a common reference design, which was then issued to each of the station contractors.

The paper describes the technical challenges from the point of view of a structural engineer, but in doing so, it draws in interfaces with disciplines as diverse as tunnel ventilation, electrical engineering, and rolling stock procurement. The reference design approach allowed unique features of the platform edge screens to be prototyped and tested before construction.

Publish Date - 2nd July 2018

Author – J. Birbeck, R. Smiley, G. Stowell and E. Newman-Sanders (all Atkins)

Price – Free

The Structural Engineer

The Elizabeth line will use above-ground sections of existing Great Eastern and Great Western tracks between Stratford and Maidenhead where new overhead line equipment (OLE) and traction power supply will be installed.

The OLE is supported by gantries of various types and configurations. In the case of the Great Eastern, the gantries date from the electrification of UK railways in the 1940s.

Initial structural assessment carried out had shown that existing gantries on the route were inadequate to carry increased loading from the upgraded OLE. However, a rigorous procedure incorporating detailed non-linear structural analysis was developed that eliminated some of the inherent conservatism in traditional codified approaches. Particular benefit was found in the case of the many types of slender structure where buckling was a governing factor. Using non-linear techniques, it was possible to demonstrate that families of structures were suitable for incorporation in the Crossrail (Elizabeth line) scheme.

This paper describes the approach that was used. The project is remarkable for significant programme and cost savings that were accomplished using sophisticated engineering analysis. It is also noteworthy from a sustainability point of view, as it allowed the existing infrastructure to be reused.

Publish Date - 2nd July 2018

Author – S. Fryer, M. Couchman and T. Eckhart (all BuroHappold Ltd)

Price – Free

The Structural Engineer

Simon Pitchers enjoys this account of the creation of the London Olympic Stadium, both for its lessons on running successful projects and the fascinating facts that will enrich a dinner-party conversation.

Publish Date - 2nd July 2018

Author – S. Pitchers

Price – Free

The Structural Engineer

This month's letters come to the defence of the magazine's brainteasers; discuss the cranked beam problem from the April issue; and answer last month's question about water trapped in hollowcore floors.

Publish Date - 2nd July 2018

Author – Various

Price – Free

The Structural Engineer

Upcoming events at HQ and around the Regional Groups.

Publish Date - 2nd July 2018

Author – Various

Price – Free

The Structural Engineer

This month we are delighted to announce the winners of the 2018 Structures prizes. Congratulations to Andrew Liew, Leroy Gardner and Philippe Block on winning the ‘Best Research Paper Prize’ for their paper on ‘Moment-Curvature-Thrust Relationships for Beam-Columns’ published in Volume 11, August 2017.

We also congratulate Chris Burgoyne and Owen Mitchell on winning the ‘Best Research into Practice Paper Prize’ for their paper on ‘Prestressing in Coventry Cathedral’ published in Volume 11, August 2017.

Both papers will be free to read until 7 September 2018.

The annual Structures prizes are judged by The Institution of Structural Engineers Research Panel and supported by Elsevier. Each prize carries an award of £500.

Publish Date - 2nd July 2018

Author – Various

Price – Free

The Structural Engineer

This month we present a reader contribution from Ewan Macpherson on shear forces.

Publish Date - 2nd July 2018

Author – E. Macpherson

Price – Free