[ Infrastructure ]
[ Infrastructure ]
Beauty and function For centuries , bridges have been an essential element of civilisation . Not only do they assure mobility and connectivity , but they also often serve as a rallying point or an expression of people ’ s aspirations for a better quality of life . At their best , bridges combine the beautiful and the practical .
Background Materials used for bridges have included stone , wood , wrought or cast iron , steel , aluminium , reinforced concrete ( often with stainless rebar ) and stainless steel . Stone bridges can last a long time , but the material is heavy and unwieldy . Wood , iron , and steel require a great deal of maintenance , which is all too often neglected . Two steel bridge collapses in the USA ( Silver Bridge , West Virginia , 1967 ; Mianus River Bridge , Connecticut , 1983 ) drew attention to the need for maintenance and helped usher in the current preference for stainless steel , which greatly reduces the need for maintenance and disruptive repair work . Corrosion played a role in both collapses , as it did in that of the Morandi Bridge in Genoa , Italy , in 2018 .
Stainless advantages The reduced maintenance required when stainless steel is applied largely stems from the fact that it requires little or no anti-corrosion treatment , such as coating or painting . Over time , it has become evident that life-cycle costs for stainless steel are lower than for carbon steel , even if the initial cost is higher . The projected life of bridges made from duplex is about 100 to 120 years , while those made of austenitics can be expected to last about 70 years .
Additional reasons for using stainless include its aesthetic appeal ( its ductility makes it easier to create attractive designs ) and the fact that it is 100 % recyclable . A major cause of corrosion is from salt , whether derived from sea air or seawater or from de-icing salts . So maritime locations and cold winters are factors that influence the specification of stronger grades . Other factors include industrial or other pollution ( especially from sulphur dioxide ), a humid climate , and exposure to water ( especially when the relevant bridge section is under water and , therefore , difficult to inspect or maintain ). Stainless steel use can be structural – girders , beams , bearings , reinforcing bars in concrete ( rebars ), anchors , arches , cables – or decorative ( handrails , mesh ). Structural elements often use plate welded into I-sections , whereas non-structural elements are normally made from sheets or hollows .
Austenitics One of the earliest , if not the earliest , use of stainless steel on a bridge-like structure was the Progreso Pier in Yukatán , Mexico ( 1941 ), where stainless rebar in 304 was applied ; it is still in service . More recent examples include the Waldeck-Rousseau road bridge at Saint-Brieuc , France ( 1998 ), one of a series of bridges using austenitic grades ( mostly 316L or 314 ) supplied by Arcelor , of which a more famous example is the Simone-de-Beauvoir pedestrian bridge in Paris ( 2006 ) spanning the river Seine . The use of austenitics in both structural and non-structural applications persisted even after duplex grades started to become popular in the first decade of the current century . They were applied
on pedestrian bridges , where aesthetics rather than mechanical strength was the primary consideration , though one vehicular bridge that made extensive structural use of austenitics is the Story Bridge in Brisbane ( 2015 ; 316L applied in mesh , I-beams , rebar , angle bar , polished tube , and cable ).
Duplex The introduction of duplex stainless steel in bridge construction roughly coincides with the start of this century . Duplex trumps austenitics by offering greater mechanical strength for the same weight , i . e ., a favourable strengthto-weight ratio . Thinner gauges can be used , making off-site construction , transportation , and installation easier . As a structural , load-bearing material , duplex is unbeatable . The first bridge in which duplex was applied was possibly the Suransuns pedestrian bridge in Switzerland ( 1999 ), but it was London ’ s Millennium Bridge ( 2001 ) that made people sit up and take notice . Designed by Foster and Partners , Anthony Caro , and Ove Arup and Partners , and using duplex 2205 , this footbridge across the Thames drew much praise and has since become a tourist attraction . It ushered in two decades in which Europe took the lead in duplex stainless-steel bridges , with Spain , Italy ( Siena ), Sweden , and UK being notable hotspots . Initially , only the standard type 2205 was applied , but from 2003 ( Pedro Arrupe Bridge , Bilbao , Spain ) lean grades such as 2304 and Forta LXD 2101 were used with growing frequency . The first projects were pedestrian / bicycle bridges , catering for the trend towards making city centres more accessible to non-vehicular traffic . Then , in 2005 , came
The Simone de Beauvoir pedestrian bridge , Paris , connects the Bibliothèque Nationale with the Bercy Park . The handrails are made of 316L supplied by Arcelor . Photo : AHert . Licence : https :// commons . wikimedia . org / wiki / File : Passerelle _ Simone-de-Beauvoir . jpg
Millennium Bridge is a pedestrian bridge linking St Paul ’ s Cathedral and the Tate Modern art gallery . Photo : Sumple , at https :// en . wikipedia . org / wiki / Millennium _ Bridge ,_ London #/ media / File : St _ Pauls _ and _ Millennium _ Bridge _ at _ night . jpg .
16 Stainless Steel World December 2023 www . stainless-steel-world . net