Editing Gateshead Millennium Bridge (section)

==Structure==

=== Design ===
[[File:MovableBridge tilt.gif|alt=Animation demonstrating how a tilt bridge operates to either let pedestrians cross or allow water traffic to pass underneath. The bridge consists of two arcs, both with their end points near a common horizontal axis. In the lowered position one arc is horizontal, on which a pedestrian can cross. The other arc is raised above the water and supports the pathway part through attached cables. To allow a boat to pass underneath, both arcs pivot as a unit so that both arcs are well above the river.|thumb|Animation demonstrating how a tilt bridge operates to either let pedestrians cross or allow water traffic to pass underneath|left]]
Gateshead Millennium Bridge was constructed to fulfil the following main design constraints: the bridge must be {{Convert|4.5|m|ft}} above river-level during high spring tides when closed; nothing must be built on the Gateshead [[Quayside]]; the deck must have no more than a 1:20 slope to allow disabled access.{{Sfn|Blandford|2007|loc=para 1. Introduction}} The bridge consists of two steel arches – a deck which acts as the pedestrian and cycle path, and a supporting arch.<ref name=":2" /> The bridge was designed to be as light as possible to allow for easy opening and closing, so the two arches are lighter towards the centre span than at the hinges.{{Sfn|Jennings|2004|p=403}} The pedestrian and cycle deck is a parabolic shape with a {{Convert|2.7|m|ft}} vertical camber. It is divided into two separate paths on different levels for the different modes of transport, separated by a [[stainless steel]] "hedge" with seating areas and steps interspersed throughout.{{Sfn|LeCuyer|2003|p=34-36}} The supporting arch is also a parabola, designed in such a way as to match the shape of the [[Tyne Bridge]] upstream.{{Sfn|Jennings|2004|p=403}} The two arches are joined together by 18 suspension cables which provide stability for people crossing the bridge.

Six [[hydraulic ram]]s (three on each side){{Sfn|White|Fortune|p=207|2012}} tilt the entire 850,000{{nbsp}}kg bridge as a single structure,{{Sfn|Petroski|2005|p=97}} meaning that when the supporting arch lowers, the pedestrian deck rises to create {{Convert|25|m|ft}} of clearance for river traffic to pass underneath.<ref name=":2">{{Cite web|title=Gateshead Millennium Bridge design|url=https://www.gateshead.gov.uk/article/4610/Gateshead-Millennium-Bridge-design|access-date=6 February 2022|website=[[Gateshead Council]]}}</ref>{{Sfn|LeCuyer|2003|p=38}} The bridge takes around four minutes to rotate through the full 40° from closed to open, moving as fast as {{Convert|18|mm|in|abbr=in}} per second.{{Sfn|Petroski|2005|p=98}} The design is so energy-efficient that, {{as of|2017|04|alt=in April 2017}}, it cost just £3.96 per opening.<ref>{{cite web|date=2017-03-23|title=Gateshead Millennium Bridge tilts|url=https://www.whatdotheyknow.com/request/gateshead_millennium_bridge_tilt|access-date=2017-05-11|website=[[WhatDoTheyKnow]]|df=dmy-all}}</ref><ref>{{cite book|last1=Winn|first1=Christopher|title=I Never Knew That About England|publisher=[[Ebury Publishing]]|year=2005|isbn=9780091902070|location=[[London]]|page=74}}</ref> The appearance of the bridge during this manoeuvre has led to it being nicknamed the "Blinking Eye Bridge", and has solidified its reputation as being not only a functional piece of infrastructure but a spectacle in and of itself.<ref name="BBC-opening" />{{Sfn|Davey|Forster|2007|p=37}} The rotation of the bridge is also used as a self-cleaning mechanism, as rubbish collected on the deck rolls towards traps built at each end.{{Sfn|Petroski|2005|p=98}}

A lighting system designed by Jonathan Spiers and Associates is used at night to attractively illuminate the bridge without causing light pollution, as the cables are too thin to be visible or reflect light at night.{{Sfn|White|Fortune|2012|p=207}}{{Sfn|Blandford|2007|loc=para. 2.7 Colour}} The lights shine white during the week and a variety of colours over the weekend. Green and red LEDs are used during the day to alert cyclists and pedestrians to the bridge's opening and closing.<ref>{{Cite web|title=Gateshead Millennium Bridge lighting|url=https://www.gateshead.gov.uk/article/4604/Gateshead-Millennium-Bridge-lighting|access-date=6 February 2022|website=[[Gateshead Council]]}}</ref>
{{gallery
|Too Late - geograph.org.uk - 336862.jpg|alt1=Picture of a close-up of the pedestrian and cycle arch while the bridge is tilting.|Close-up of the pedestrian and cycle arch while the bridge is tilting.
|Millennium Bridge - Hydraulic Rams - geograph.org.uk - 477276.jpg|alt2=Picture of the hydraulic rams which allow the bridge to fully tilt open in around 4 minutes.|The hydraulic rams allow the bridge to fully tilt open in around 4{{nbsp}}minutes.
|Millenium Bridge at dusk.jpg|alt3=Picture Gateshead Millennium Bridge lit purple at dusk.The lights on the bridge vary in colour over the weekend.|Gateshead Millennium Bridge lit purple at dusk. The lights on the bridge vary in colour over the weekend.
}}

=== Construction and installation ===
Gateshead Council selected Gateshead-based Harbour & General as the main contractor for the construction of the bridge. Harbour and General then selected over 12 sub-contractors to cover elements of construction including control systems, metalwork, lighting, and piling and river work.{{Sfn|White|Fortune|p=215|2012}} Consulting engineering group [[Ramboll]] provided further engineering, construction, and contract management services.<ref name=":3">{{Cite web|title=Gateshead Millennium Bridge|url=https://uk.ramboll.com/projects/ruk/gateshead%20millennium%20bridge|access-date=7 February 2022|website=Uk.ramboll.com}}</ref> The bridge's structure was modelled in [[LUSAS]] using 3D elements. LUSAS modelling allowed a model of the bridge to be built and allowed analysis of buckling forces, wind, and temperature.<ref>{{Cite web|title=Gateshead Millennium Bridge|url=https://www.lusas.com/case/bridge/gateshead.html|access-date=7 February 2022|website=Lusas.com}}</ref>{{Sfn|White|Fortune|2012|p=217}} Another software – Pertmaster Professional – was used for risk and project management and cost analysis.{{Sfn|White|Fortune|2012|p=217}}

[[Severfield|Watson Steel]] was appointed as the specialist contractor to prefabricate the bridge, and they subcontracted the design of the hydraulic system to Kvaerner Markham.{{Sfn|Blandford|2007|loc=para. 3 Constructions}} The pre-fabricated sections of the bridge were [[shot-blasted]] and painted in Hadrian's Yard, {{Convert|6.5|km|mi|abbr=in}} from the bridge's final position.{{Sfn|Blandford|2007|loc=para. 3.2.1 Initial Assembly}}{{Sfn|LeCuyer|2003|p=38}} The entire structure was assembled by first welding together the nine arch sections and deck sections, and then attaching the cables to the arch and deck.{{Sfn|LeCuyer|2003|p=38}} Protective paintwork (Interzone 505 and Interthane 990 from [[International Paint|International Protective Coatings]])<ref>{{Cite magazine|date=2002|title=Protecting Gateshead's Millennium Bridge. The innovative Gateshead Millennium Bridge has been coated by IPC|magazine=[[Products Finishing]]|publisher=Sawell Publications ltd.|volume=55|issue=5|page=19|access-date=}}</ref> was applied to the arch before it was erected.{{Sfn|Blandford|2007|loc=para 3.2.3 Paintwork}}

The bridge was lifted into place in one piece by the [[Asian Hercules II]],<ref>{{cite web |url=https://www.gateshead.gov.uk/article/4601/Bridge-delivery-and-opening |website=[[Gateshead Council]] |title=Gateshead Millennium Bridge delivery and opening |access-date=2009-07-23 |df=dmy-all}}</ref> one of the world's largest [[Crane vessel|floating cranes]], on 20 November 2000.<ref name="BBC-opening" /> Whilst being transported by the crane, the bridge was rotated 90° in order to navigate narrow bends along the river.{{Sfn|LeCuyer|2003|p=38}} It was successfully slotted into threaded bolts in the piers with only {{Convert|3|mm|in|1|abbr=in}} of tolerance. Handrails, seating, and the hydraulic systems were installed after the bridge was in place.{{Sfn|Blandford|2007|loc=para. 3.4 Final Installations}} The transportation of the bridge took only one day and was a spectacle, attracting crowds of onlookers.{{Sfn|LeCuyer|2003|p=38}}

{{Multiple image
| image1            = Bollards west of the Gateshead Millennium Bridge (geograph 2557922).jpg
| image2            = Forth Sentinel at Gateshead Millennium Bridge (geograph 2806946).jpg
| footer            = The piles under Gateshead Millennium Bridge (left) were removed in 2012 (right).
}}

The [[Port of Tyne Authority]] required the design of the bridge to incorporate a vessel collision protection system. As a result, two rows of parallel fixed piles, splaying out diagonally on each side of the bridge, were installed. However, it became clear to members of the construction project team and WilkinsonEyre that they were unsightly and undermined "the finesse of the bridge". Between February and June 2000, the unsightly nature of the piles also caught the attention of the public, with multiple news articles and letters expressing discontent. Complaints pointed out that the [[Millennium Bridge, London|Millennium Bridge in London]] did not have similar piles, and that a [[Newcastle University]] boat race had to be moved specifically to avoid potential collision with the piles.{{Sfn|White|Fortune|2012|p=215}} Over time, Gateshead Council and the Harbourmaster noted that the piles were not required and they were removed in 2012 by [[BAM Nuttall Limited]]. This decision was ultimately less expensive than maintaining them.<ref>{{cite news|date=2012-03-16|title=Final River Tyne bollard removed|work=[[BBC News]]|publisher=[[BBC]]|url=https://www.bbc.co.uk/news/uk-england-tyne-17403849|access-date=2012-08-01|df=dmy-all}}</ref><ref>{{Cite news|last=Sykes|first=Alan|date=8 March 2012|title=Gateshead and Newcastle's 'winking bridge' loses its painful piles|work=[[The Guardian]]|url=https://www.theguardian.com/uk/the-northerner/2012/mar/08/blogpost-winking-bridge-newcastle-gateshead-millennium-sage-baltic|access-date=7 February 2022}}</ref>