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             Olympic Park Bridges
          L01 and H01
              
                Exceptionally
                slender steel tied arch footbridge with steel plate hangers 
                Single-span integral highway bridge of composite steel
                box girder construction
                Elastic critical bucking and nonlinear
                analysis  
 The London 2012 Olympic
          Park structures, bridges and highways project required the provision of
          11 highway bridges, 13 pedestrian bridges, 6 underpasses and many other temporary bridges with
          spans up to 56.5m.  Atkins used LUSAS Bridge analysis software to assist with its analysis and
          design of a number of bridges on the project including two that
          required detailed elastic critical bucking and nonlinear analysis. In
          doing so, Atkins found that existing industry and codified guidance
          was not always sufficient to ensure that a structure with unusual
          buckling behaviour was correctly modelled and the behaviour correctly
          accounted for.  Footbridge
          L01 Footbridge L01 crosses
                Ruckholt Road and provides
                a pedestrian and cycle link between the Northern Spectator
                Transport Mall and the Olympic Park.
                The single span structure is a unique form of construction whose behaviour is a hybrid between that of a tied arch and Vierendeel girder.
                The arch spans 42m and carries a 5.5 wide steel deck formed from
                550mm x 300mm box sections with transverse ribs at 540mm
                centres. The arch rib is made exceptionally slender by exploiting the overall Vierendeel girder behaviour.
                135mm x 25mm solid plated hangers (slats)
                at 135mm centres provide both lateral and in-plane stability,
                and also create a striking effect in elevation. The complex geometry required elastic critical buckling analysis
                with LUSAS Bridge to determine the resistance of the arch and
                also nonlinear analysis to assess the effects of arch deformation on the rigid hangers and deck.
                  
                 
                  
                    | 
 |  
                    | In plane
                      buckling |  
                    | 
 |  
                    | Out of plane
                      buckling |  Bridge
H01
                 Bridge H01 is an
                example of the type of integral, steel–concrete composite
                open-top box girder construction that was used across the park.
                It is a single-span integral highway bridge that carries a local distributor road over the River
                Lea in the north of the Olympic Park. It was the first box girder bridge to be erected and opened
                initially to construction traffic in October 2009. 
                  
                 
                  
                    
                      | 
 |  
 |  
                    | Bridge H01 during
                construction
                     | Bridge H01 completed 
                     |   Whilst
                box girders are torsionally stiff when completed they are less so during construction if they are
                of the open-top type, as in this case. The design of
                bridge H01 used vertical cross-bracing at regular centres to
                restrain the compression flange during deck slab construction to prevent lateral
                buckling, but detailed analysis with LUSAS Bridge indicated that this alone was insufficient to prevent significant second order twisting effects under torsional loading.
                Atkins' designers addressed the problem and, as a result, updated national box girder design guidance was
                produced.
                 
                  
                    |  
 |  
 |  
                    | LUSAS modelling
                 | Girder
                      buckling |   
 Bridge F02 -
                similar in appearance to H01
                     Additional
                    information
                 
                  
                    Paper by Atkins
                    entitled 'Design of the Olympic Park
  Bridges H01 and L01' describing the technical challenges
  involved with these bridges can be found here.
                    Article entitled
                    'Cool Olympic Bridge' in August 2012 issue of Modern Steel
                    Construction can be found here.
                  Paper
                  by the project partners entitled 'Delivering London 2012: structures, bridges and highways'
                  describing
  the Olympic Park structures, bridges and highways project as a whole is
                  available from the ICE Virtual Library here.
                  Presentation
                    entitled 'An Overview of the Olympic Park Infrastructure'
    was given by Chris Hendy of Atkins and David Baird of the Olympic Development Agency
    at Bridges 2012, held in Manchester, UK, 27-28 March 2012. 
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