The Millennium Bridge - Case Study
The Millennium Bridge - Case Study
On the 10
On the 10thth of June 2000 of June 2000 a brand new iconic bridge across the Thamesa brand new iconic bridge across the Thames
rier in !ondon was o"ened to celebrate and mar# out the
rier in !ondon was o"ened to celebrate and mar# out the millenniummillennium year
year$ The bridge $ The bridge called %The Millennium called %The Millennium Bridge& and was the Bridge& and was the result of worldresult of world class architects 'orman (osters and )artners* ciil engineering
class architects 'orman (osters and )artners* ciil engineering consultancy Oe
consultancy Oe +ru" and +ru" and scul"tor Sir +nscul"tor Sir +nthony Carthony Caro winning ao winning a com"etition run by
com"etition run by the (inanthe (inancial Times and cial Times and !ondon Borough of Southwar#!ondon Borough of Southwar# to design a new foot bridge$
to design a new foot bridge$ The now twele years old %Millennium Bridge&The now twele years old %Millennium Bridge& seres as a functional lin# oer the
seres as a functional lin# oer the Thames as well as an iconic Thames as well as an iconic structurstructuree in the heart
in the heart of !ondon ,(of !ondon ,(it"atric#* 2001.$it"atric#* 2001.$ The bridge is a shallow s
The bridge is a shallow sus"ension bridge suus"ension bridge su""orted by two "iers ""orted by two "iers with twowith two sets of four 120mm diameter loc#ed coil cables s"anning from end to end sets of four 120mm diameter loc#ed coil cables s"anning from end to end su""orting a 1//m long dec#$ Steel bo sections s"an between the two su""orting a 1//m long dec#$ Steel bo sections s"an between the two sets of coiled cables su""orting the dec# structure which com"rises of two sets of coiled cables su""orting the dec# structure which com"rises of two steel edge tubes and etruded aluminium bo sections$ The "ier body is a steel edge tubes and etruded aluminium bo sections$ The "ier body is a ta"ering elli"se cast in C0 reinforced concrete and on to" of these rests a ta"ering elli"se cast in C0 reinforced concrete and on to" of these rests a steel brac#et$ The foundations for
steel brac#et$ The foundations for the north and south the north and south abutments consistabutments consist of a series of cast in
of a series of cast in situ concrete "iles made of C0 concrete and situ concrete "iles made of C0 concrete and T30 steel bars$ The "
T30 steel bars$ The "ier foundations arier foundations are designed m diameter caise designed m diameter caissonssons within a sheet "ile co4erdam$ The "robable design life for the
within a sheet "ile co4erdam$ The "robable design life for the structurstructure ise is 120 years as although there is not any s"eci5c information released it 120 years as although there is not any s"eci5c information released it meets the 120 year category as mar#ed by the BS 63/* The 7esign meets the 120 year category as mar#ed by the BS 63/* The 7esign
Manual for 8oads and Bridges olume 2 B7 29:0 %The design manual for Manual for 8oads and Bridges olume 2 B7 29:0 %The design manual for footbridges& as well as
footbridges& as well as the 7esign standards for urban infrastructurethe 7esign standards for urban infrastructure olume 6
olume 6 %Bridges and related Structures& ,(it"atr%Bridges and related Structures& ,(it"atric#* 2001.$ic#* 2001.$ The structur
The structure is situated on the Thamee is situated on the Thames rier in the ;nited <ingdos rier in the ;nited <ingdom andm and thus e"osed to some harsh conditions$ The
thus e"osed to some harsh conditions$ The e"osure"osure conditions fore conditions for reinforced concrete in the design would be =7/* =C2 and =( in reinforced concrete in the design would be =7/* =C2 and =( in accordance with table +$3 ,British Standards >nstitute* 200.$ The
accordance with table +$3 ,British Standards >nstitute* 200.$ The form ofform of e"osur
e"osure this e this structurstructure is e is sub?ect to sub?ect to encom"asses long-term water contactencom"asses long-term water contact and "arts "ermanently submerged in water* an array of
and "arts "ermanently submerged in water* an array of chemicalschemicals including chlorides which hae ability to induce
including chlorides which hae ability to induce corrocorrosion on concrete andsion on concrete and steel* de-icing agents and cyclic wet
steel* de-icing agents and cyclic wet and dry conditions$and dry conditions$
(igur
(igure e 1$ 1$ Satellite Satellite iew iew of of the the Millennium Millennium Bridge* Bridge* !ondon !ondon (igur(igure e 2$ 2$ Street Street ma" ma" iewiew of the Millennium bridg
The eact location of the Millennium Bridge in ;< is TA /209 066 ,;< grid reference 5nder.$
Structural Components
8einforced concrete "iles were used for the foundations of the north and south abutments$ The foundations are sub?ect to a /0M' combined lie and dead load acting horiontally due to the bridge cables "roducing a large oerturning moment$ ,(it"atric#* 2001. The use of reinforced concrete is a common selection for foundations as its com"osition of concrete and ribbed steel bars allows it to be both good in com"ression and tension$ (or this structure it is essential as it must withstand both horiontal and ertical loading$ 8einforced concrete has ery good
durability ualities and will hae been designed to the correct s"eci5cation according to the %Durocode 2E7esign of Concrete Structures& meaning that an a""ro"riate coer and 5nish will hae been selected to ensure the
structure withstands the corrosie enironment and meets the reuired design life$ (ailures may occur in the reinforced concrete through "oor design or bad construction$ The design may hae underestimated the e4ects of sul"hate attac# or reactie aggregates and thus wea#en the concrete and e"ose the steel bars or be constructed "oorly so as not to meet the s"eci5cation and thus negatiely a4ect the material "ro"erties ,Mulheron* 2012.$
The manufacture of the "iles should be done in accordance with the regulation laid out by ()S ,(ederation of )iling S"ecialists. in association with FSD ,Fealth and Safety Decutie.$ The documentation highlights all the "ossible health haards from materials and manufacture of "iles ,FSD* 2010.$
Concrete is highly al#aline and it can cause serious burns if it comes in
contact with s#in and eyes$ There is also the "ossibility of im"aling oneself on the steel rebar on site$ +""ro"riate clothing and ))D should be worn$ +n alternatie material that could be used instead of reinforced concrete is steel "iles either hollow or %F& sections$ Steel "iles are robust* light to
handle* ca"able of carrying high com"ressie loads and create a high frictional resistance in the ground ,Tomlinson* Goodward* 200.$ +lthough there are metallic coatings such as "aints and organic "olymer 5lms* steel is still sub?ect to chemical corrosion and direct oidation which limits its long-term function and increases costs in maintenance ,Mulheron* 2012.$ The "iers for the bridge are manufactured from C0 reinforced concrete
and a mild steel H brac#et$ The "iers are sub?ect to being submerged in water and must be ca"able of withstanding shi" im"acts$ They are also sub?ect to high com"ressie and aial loads ,(it"atric#* 2001.$ 8einforced concrete with its good com"ressie and tensile character as well as its mass ma#e it a suitable material$ 8einforced concrete is also durable haing good resistance against chemical corrosion and if designed
according to correct standards will "rotect the steel reinforcement$ The mild steel used in the H brac#et has a strong yet malleable form that
allows it to be easily machined* sha"ed and welded$ >t can also be tailored for its use by using di4erent 5nishes which enhance certain characteristics such as cold rolling which "roduces internal stresses in the material
increasing its strength ,Mulheron* 2012.$
The health and safety issues inoling the steel brac#et encom"ass unguarded machinery* e"osure to controlled and uncontrolled energy sources* s#in contact with chemicals and hot metal and etreme
tem"eratures ,>nternational !abour Organisation 2003.$
+ suitable alternatie to steel in the brac#et would be titanium$ Titanium is lighter and sti4er than steel and also has a high leel of corrosion
resistance without reuiring any e"ensie 5nishes$ Titanium is howeer still etremely e"ensie and diIcult to sha"e ,Mulheron 2012.$
The %Millennium Bridge& dec# is manufactured from two steel edged tubes which su""ort etruded aluminium bo sections$ The dec# is designed to withstand an im"osed "edestrian load in accordance with B7 /6:
,(it"atric#* 2001. and wind load and the enironmental e"osure including rain water runo4 and de-icing agents$ Steel is a a""ro"riate
material for the edged tubes because of its strength* ease of manufacture and its ability to act well under both com"ressie and tensile forces
,Mulheron 2012.$ >t does howeer reuire 5nishes to "rotect it against oidisation and chemical corrosion$ )olymer "aints can be used to "rotect the steel but reuire maintenance throughout its serice$
+luminium has a reasonable strength and sti4ness so it is able to carry the im"osed "edestrian load$ >t is highly reactie and forms a colourless oide layer on its surface which gies it a high resistance to corrosion without damaging its aesthetic a""earance$ +luminium is also uite a light
material lowering the oerall weight of the structure ,Mulheron 2012.$ +ustenitic stainless steel also "ossesses a high corrosion resistance
allowing it to withstand harsh wet conditions$ This #ind of stainless steel can also be hardened by cold wor#ing which can increase its load carrying ca"acity$ >n com"arison stainless steel is more e"ensie than aluminium and does not delier the same aesthetical a""eal ,Mulheron 2012.$
Faards and ris#s should be highlighted during design and a""ro"riate information "roided to wor#ers$ Chec#s on CSCS and C)CS tests of
wor#ers should be carried out and a""ro"riate welfare facilities "roided throughout the construction "eriod$ +ny obious ris#s should be
immediately re"orted$ The contractors res"onsible for the wor# should
carry out ris# assessments and abide by the %Fealth and Safety Decutie& regulations FSD ,2006.$
Life Cycle
The life cycle of the %Millennium Bridge& was initiated in Se"tember 199 when the (inancial Times and the !ondon Borough of Southwar# organised a com"etition to design a new "edestrian foot bridge in !ondon$ The
winning teams design was ta#en forward and gien 5nancial bac#ing ,(it"atric#* 2001.$
(ollowing this the "reliminary design stage begins with research* scul"ting and redesigning$ Then detailed design ta#es oer and a series of
"rofessional drawings clearly showing eery as"ect of the bridge are "roduced and sent to the client* architect and "ro?ect manager$ >f no
amendments were reuired the "ro?ect moes to the tender stage$ Balfour Beatty won the contract for the enabling wor#s and ?oint enture Monberg Thorsen and Sir 8obert Mc+l"ine the main contract ,(it"atric#* 2001.$
Because of the sensitiity of the area an archaeological ecaation started >n late 199 and the 5rst "ile went into the ground in +"ril 1999$ The main su"erstructure was underway in the beginning of 2000 and the bridge oIcially o"ened to the "ublic on the 10th June 2000 ,(it"atric#* 2001.$
Once o"ened the bridge e"erienced a large lateral loading and began oscillating at concerning leels$ + research "rogram was underta#en to 5nd a solution at >m"erial College !ondon and Oe +ru" oer saw the design wor#$ Cleeland Bridge ;< won the contract for the amendments and the bridge was o"ened again at the end of 2001 ,(it"atric#* 2001.$ The %Millennium Bridge& enters serice for its designed life time which is
li#ely to be 120 years $ Foweer during this "eriod it will reuire maintenance chec#s and re"air wor#s$ The bridge will need to be re"ainted freuently throughout its life time and the icious dam"ers re"laced seeral times ,(it"atric#* 2001.$
(inally the bridge will be ta#en a"art much of it recycled with a small amount demolished and dis"osed of in land5ll$
End-of-Life Options
The structure as a whole at the end of its life is li#ely to be
decommissioned after a structural ins"ection 5nds it unsafe for serice and ta#en down$ >t could be ta#en down and rebuilt in a di4erent location and re5tted$ +nother alternatie could be modifying:e"anding it for a continual serice in !ondon$
There are s"eci5c com"onents of this structure which could be reused in other buildings$ The cables used to su""ort the dec# could be ta#en a"art and em"loyed on another sus"ension bridge$ Suitable testing and chec#s would need to be carried out beforehand but this is certainly a "ossibility$ The main dec# could also be dismantled and installed on a new foot bridge
as could the hand rails$ The foundations could be reused for a new structures in the same location$
The "articular materials also hae di4erent end of life o"tions aailable$ The etruded aluminium dec# could be recycled or reused on another
footbridge de"ending on its condition$ +luminium scra" is in high demand with a good "rice for it as it melts at a much lower tem"erature than the irgin material so it is more eIcient and cost e4ectie to recycle ,BM8+.$
The steel edged tubes* bo sections and H brac#et can be reused or recycled$ The reinforced concrete "iles and caissons could also be
recycled$ The steel must be remoed from concrete which is achieed by sawing and brea#ing the section$ This releases the steel which can then be "rocessed as scra" metal and the concrete bro#en u" further and recycled as an aggregate base$
A Dierent Design Approach
The %Millennium Bridge& is a "iece of architectural magni5cence and engineering achieement$ This being so it is an etremely com"le structure which reuires s"ecialist com"onents* materials and
construction$ + far more sim"le structure could hae been designed using minimal amounts of new materials and feature a sim"le dismantling
"rocess so recycling the structure could be made etremely eIcient$ +""roaching the conce"t design with an aim of dematerialisation* trans-materialisation and durability would limit the amount of materials needing to be "rocessed and ensure that the materials used were the most
sustainable without com"romising on long term "erformance$ This would hae a "ositie im"act on end of life o"tions as there is less material to wor# and what there is can be done so in a sustainable manner$
References
1$ (it"atric#* +$T$ ,2001. %!in#ing !ondonE The Millennium Bridge& Royal Academy of Engineering* ""$ -2
2$ (it"atric#* +$T$,2001. %The !ondon Millennium (ootbridge& 69:22 ""$ 16-// The Structural Engineer onlineK +ailable at
htt"E::www$londonmillenniumbridge$com: ,+ccessedE10 7ecember 2012.
/$ B8>T>SF ST+'7+87S >'ST>T;TD$ ,200. BS3000-1 E 200$ 8euired Coer related to D"osure Conditions$ Milton <eynesE BS>
$ The 7esign Standards for ;rban >nfrastructure ,2012. %Bridges and 8elated Structures& Urban Services onlineK +ailable atE
htt"E::www$tams$act$go$au:LLdata:assets:"dfL5le:000/:1236:ds06L bridges$"df ,+ccessed 10 7ecember 2012.
3$ 7M8B ,200. % 7esign Criteria for (oot Bridges& +ailable atE
htt"E::www$dft$go$u#:ha:standards:dmrb:ol2:section2:bd290$"df ,+ccessed 10 7ecember 2012.
$ ;< grid reference 5nder ,2012. +ailable atE
htt"E::gridreference5nder$com: ,+ccessed 10 7ecember 2012.
6$ +8;)$ ,2001.$ %General Arrangement and Damper Layout’ E Oe +ru" and )artners$
$ +8;)$ ,2001.$ %orth and South !iers General Arrangement’ E Oe +ru" and )artners$
9$ Mulheron* M$ ,2012. Construction Materials* D'@2100 !ecture notesK "onstruction #aterials$ #etals and there Alloys$ "oncrete
Technology$ Reinforced "oncrete% Construction Materials$ ;niersity of Surrey* (aculty of Dngineering and )hysical Sciences* @uildford$ 10$ FSD ,2006. %Contractors 8oles and 8es"onsibilities& +ailable
atE htt"E::www$hse$go$u#:construction:cdm:contractors$htm ,+ccessed 10 7ecember 2012.
11$ Tomlinson$ M* Goodward$ J ,200. )ile 7esign and Construction )ractice$ Dbrary onlineK +ailable atE
htt"E::www$irssg$com:ciil:5les:library:structure:"ile$"df ,+ccessed 10 7ecember 2012.
12$ >nternational !abour Organisation ,2003. %Code of )ractice on the Safety and Fealth in the >ron and Steel >ndustry& onlineK
+ailable atE
htt"E::www$ilo$org:wcms"3:grou"s:"ublic:NedL"rotect:N"rotra:Nsa fewor#:documents:normatieinstrument:wcmsL112/$"df
,+ccessed on 10th 7ecember 2012.
1/$ BM8+ ,2012. &About #etal Recycling’ +ailable atE
htt"E::www$recyclemetals$org:aboutLmetalLrecycling ,+ccessed 10 7ecember 2012.
1$ The concrete Society ,2012. &Design 'or(ing Life’ +ailable atE htt"E::www$concrete$org$u#:5ngerti"sLnuggets$as"
cmdPdis"layQidP630 ,+ccessed 10 7ecember 2012.
13$ <eoleian* +* @$ ,2003. %!ife Cycle Modelling of Concrete Bridge 7esign& onlineK +ailable atE
htt"E::dee"blue$lib$umich$edu:bitstream:2026$2:9:1:<eoleianJ>n fraSystems2003$"df ,+ccessed 10 7ecember 2012.
16.()S ,2012. %'otes for @uidance on )uwer& onlineK +ailable atE
htt"E::www$f"s$org$u#:f"s:safety:);GD8R20@uidanceR20Dd2R20-R20MarR202010$"df ,+ccessed on 10th 7ecember 2012.
By Ben?amin J Chase 10th 7ecember 2012
