View source for South Stand Expansion, Etihad Stadium

==[[Structural_steel_design_awards|Structural Steel Design Awards]] 2016 - Award==
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The South Stand expansion increased the capacity of the [[Leisure_buildings#Stadia|stadium]] during the 2014/15 football season, adding 6,000 new seats through a third tier on the terraces and 1,500 additional seats around the pitch.  An architecturally sympathetic extension of an existing catenary ringed structure was needed, which did not compromise the integrity or capacity of the structure and ensured that the existing [[Leisure_buildings#Stadia|stadium]] remained operational during works. 

The [[Design|design]] was technically complex as the existing [[Leisure_buildings#Roofing options in stadia|roof]] involved a cable net structure with a tension ring, from which steel roof rafters hung.  The structural integrity of the existing tension ring relies on it running around the whole circumference of the roof; therefore any modification to the [[Leisure_buildings#Roofing options in stadia|roof]] could not affect this, even in areas where roof rafters were removed.  Protection of the existing cable was vital as there was no repair procedure in place and damage would result in replacement and potentially the closure of the [[Leisure_buildings#Stadia|stadium]] for two years. 

Extensive [[Design|design]] optimisation exercises were undertaken, particularly for the [[Leisure_buildings#Roofing options in stadia|steel roof]] and the [[Concept_design#Concrete or steel cores|stability cores]].  A whole series of geometric studies evaluated the effects of different stay and mast angles, concluding with a solution to satisfy both minimum material requirements and cost.  The [[Concept_design#Concrete or steel cores|stability cores]] were formed of steel [[Braced_frames#Vertical bracing|vertical brace]] planes with the inclusion of outrigger bracing to add efficiency and, although a solution normally adopted on [[Multi-storey_office_buildings#Tall commercial buildings|tall buildings]], this approach proved effective for the project.  A [[Design|design]] and [[Cost_of_structural_steelwork|costing]] study of the original stays, which were formed of cable, revealed that bars could be introduced for the new stays.  These had marginally more [[Construction#Steel erection|erection]] work associated with them, but overall were a more efficient solution.  Combined 3D [[Modelling_and_analysis#Modelling|modelling]] allowed the [[Service_integration|integration of all services]] within the structural envelope, including the late addition of increased sports lighting requirements in accordance with new regulations. 
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The project contains a number of highly bespoke details tuned to the complex geometries and design challenges, including the multi-stay connection at the top of the masts and column bases formed of spherically machined plates and rotational [[Bridge_articulation_and_bearing_specification#Bearings|bearings]], which allow the new [[Design|design]] to accommodate differential movements between the new and existing structures. 

An area of complexity centred on the temporary modes of the [[Leisure_buildings#Stadia|stadium]].  For typical [[Leisure_buildings#Stadia|stadium]] conversions an additional tier can be built behind the existing building and a new roof constructed over the existing roof, with little interaction between old works and new.  This was not the case with Etihad as the roof profile and supports at the end stands extended further back behind the seating and the new upper tier would therefore project through the existing roof profile. 

The ‘interim roof’ solution involved cutting and removing the existing back of the roof, acknowledging that this meant cutting into roof rafters which had significant locked-in forces from the dead loading of the roof.  Significant and complex [[Construction#Temporary works|temporary works]] were required for the project, with the remodelling of the existing roof completed in the first closed season, alongside temporary propping to allow work to proceed above the existing roof.  The existing roof was removed in the second closed season to reveal the new terrace behind.  The new design respects the geometry of the existing [[Leisure_buildings#Stadia|stadium]] and, whilst the expanded South Stand is significantly larger than the previous one, blends into the original [[Design|design]]. 

Examples of innovation include bespoke designed solutions such as [[Bridge_articulation_and_bearing_specification#Spherical bearings|spherical bearings]], cable protection frames, an upper MEWP platform, intermediate roof propping, tie bar installation lifting beams to include remote release features and hidden bolted [[Moment_resisting_connections#Splices|splices]] in the rafters.  The availability of a CTL 1600 [[Construction#Mobile cranes|crane]], the largest [[Construction#Mobile cranes|crane]] of its type in the country, significantly influenced the lifting methodology as it permitted much larger lifts, speeded up [[Construction|construction]] and reduced the need for working at height splicing components. 
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In terms of [[Sustainability|sustainability]] the project focussed on [[Recycling_and_reuse|re-use and recycling]], rather than demolition.  The team worked exceptionally hard to retain the existing cable net that supports the stadium roof.  Much of the original building was retained during [[Construction|construction]] and existing components from the building’s [[Facades_and_interfaces|façade]] re-used.  Steel and aluminium crowd ‘flood gates’ were cleaned, repaired and repainted and the existing lower tier terracing was re-used, following careful detailing with the connection to the new building.  The client also received a masterplan [[Design|design]] which enables the [[Leisure_buildings#Stadia|stadium]] capacity to be expanded further to the absolute limit of the existing cable net and then, only at that point, does the roof need to be completely replaced.

A risk assessment considered potential [[Structural_fire_resistance_requirements|fire loadings]] throughout the building and established specific design criteria.  [[Fire_protecting_structural_steelwork#Intumescent Coatings|Intumescent paint]] was used extensively to enable steel to be exposed to view and [[Corrosion_protection|corrosion protection]] is to a high standard and [[Appropriate_specifications|specification]]. 

The extension, completed within 16 months, was opened on the 16 August 2015 in front of a record crowd of 54,331 people.
 
{|class="wikitable" width=400px 
|-
|'''Architect'''||Populous
|-
|'''Structural Engineer'''||BuroHappold Engineering
|-
|'''Steelwork Contractor'''||Severfield
|-
|'''Main Contractor'''||Laing O’Rourke
|-
|'''Client'''||Manchester City Football Club
|}

==Judges' comment==
This is a complex project which added 6,000 seats above the roof at one end of an existing [[Leisure_buildings#Stadia|stadium]].  The work tested all facets of steelwork [[Construction|construction]] to their limits, including [[Design|design]], [[Fabrication|fabrication]] and construction.

A stunning testimony to all concerned and to the capabilities of steelwork which merges seamlessly into the existing structure.

[[Category:Case studies – Leisure buildings]]
[[Category:SSDA]]