View source for Urbanest 199 Westminster Bridge Road, London

==Article in [http://www.newsteelconstruction.com/wp/wp-content/uploads/digi/NSCMar2015/index.html#/22/ NSC March 2015]==
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'''Steel college supports residential scheme'''<br>
Long internal spans and a lightweight roof structure were the reasons why steel construction was chosen for a prestigious [[Residential_and_mixed-use_buildings#Student residences|student accommodation]] and [[Education_buildings|college project]] in London.<br> 

Scholars lucky enough to get a room at [[Residential_and_mixed-use_buildings#Student residences|student accommodation]] provider Urbanest’s latest London scheme will have some of the most sought after views in the capital. Located next to County Hall and Waterloo Station, 199 Westminster Bridge Road overlooks the River Thames affording views of the Houses of Parliament and Big Ben.

Designed by architects AHMM, the hybrid scheme will deliver 1,092 rooms in a variety of formats including bedsits, two bedroom units and larger four bedroom duplex flats. [[Residential_and_mixed-use_buildings#Student residences|Student accommodation]] is spread over 16 levels from floor three to the uppermost level 18.

Below level three the lower part of the scheme includes four floors of [[Education_buildings|college]] (ground, [[Single_storey_industrial_buildings#Mezzanines| mezzanine]], first and second floors), flexible and affordable workspace for small local start-up businesses, as well as a double height basement containing plant rooms, music rooms, a gym and a 16m × 5m swimming pool.

Level three of the scheme is essentially a [[Residential_and_mixed-use_buildings#Podium structures|transfer deck]] and the most crucial element of the project design as this is the main interface between the reinforced concrete residential zone and the [[Braced_frames|steel-framed]] college below. Level three also supports a private roof garden that will only be accessible to residents.
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From basement level up to the third floor [[Composite_construction|structural steelwork with metal decking]] has been used as the framing material and Bourne Steel [[Fabrication|fabricated]], supplied and [[Construction#Steel erection|erected]] 1,570t of steel for this part of the scheme. Steel was chosen for the college as the design includes a number of [[Long-span_beams|long span]] areas, such as a large central [[Steel-supported_glazed_facades_and_roofs#Atrium Roofs and Sky lights|atrium]]. “These areas are much easier to construct with steel,” adds Balfour Beatty Senior Project Manager Geoff Grant. “And using steel for the [[Education_buildings|college]] also means the classrooms have more [[The_case_for_steel#Flexibility for changing times|in-built flexibility]].”

Bourne Steel’s [[Construction#Steel erection|erection]] sequence has been split into two programmes. Initially the company [[Construction#Steel erection|erected]] the bulk of the project’s steelwork from basement slab up to third floor transfer level during a 12-week period in early 2014. Currently Bourne is working on a return visit to site [[Construction#Steel erection|erecting]] a further 80t of hot rolled steel to form the project’s sloping roof ([[#Topping the project|see below]]).

As busy roads and railway lines surround the site logistics and planning played a key role in the [[Construction#Steel erection|erection]] programme. With little room for material storage as the structure takes up most of the site’s footprint, all of the steelwork had to be delivered on a just-in-time basis. “We delivered about 25t of steel to site each day and with space at a premium and no room to position a [[Construction#Mobile cranes|mobile crane]], all of the steelwork for the lower levels was [[Construction#Steel erection|erected]] by the two on-site [[Construction#Tower cranes|tower cranes]],” says Bourne Steel Project Manager Iain Griffiths.
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The basement contains the initial elements of steelwork to be [[Construction#Steel erection|erected]]. This area contains a plant [[Single_storey_industrial_buildings#Mezzanines|mezzanine]] formed with 3.5m high steel columns supporting [[Steel_construction_products#Decking for floors|metal decking]], while longer 7m columns in the basement support the reinforced concrete ground floor slab.

From ground floor upwards the scheme’s steelwork zone incorporates a central [[Steel-supported_glazed_facades_and_roofs#Atrium Roofs and Sky lights|atrium]] around which the college’s [[Single_storey_industrial_buildings#Mezzanines|mezzanine]], first and second floor facilities are arranged. “Typically college floors are formed from a [[Composite_construction|composite steel frame construction]] with concrete slab on profiled [[Steel_construction_products#Decking for floors|metal decking]], while [[Concept_design#Structural options for stability|stability]] is provided by the [[Concept_design#Concrete or steel cores|cores]] and an additional stair core that runs from basement to third,” says Ramboll Project Director Mitesh Patel.

Most of the steel beams are designed as [[Composite_construction#Downstand beams|downstand beams]] acting compositely with the slab above. [[Welding#Drawn_arc_stud_welding.2C_process_783|Shear studs welded]] to the top flange of the beams provide the required composite action. However, there are a few areas of the building where [[Composite_construction|composite construction]] was not suitable as Mr Patel explains. “Around the building’s perimeter and the internal [[Steel-supported_glazed_facades_and_roofs#Atrium Roofs and Sky lights|atrium]], primary beams are required to cantilever out from the columns. These beams are designed as non-composite as the top flanges will be in tension under hogging action. To ensure the internal spans still behave as composite sections all the moment from the edge cantilevers (both internal and external) are taken by the columns with [[Simple_connections|pinned connections]] between the column and internal primary beams.”
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At first floor level, hangers are used to support areas of the [[Single_storey_industrial_buildings#Mezzanines|mezzanine]] below where there a large cantilevers or long internal spans. In these instances, the depths of the beams were increased so that the top of the steel is level with the top of slab and this then acts non-compositely but fully restrained. At [[Single_storey_industrial_buildings#Mezzanines|mezzanine]] level, due to restrictions on the structural depth, all beams sit within the slab level and are designed as non-composite.

The largest sections of steelwork to be [[Construction#Steel erection|erected]] were a series of fabricated [[Steel_construction_products#Plate girders|plate girders]], up to 22m long and weighing up 19t each, which spans the college’s central [[Steel-supported_glazed_facades_and_roofs#Atrium Roofs and Sky lights|atrium]] and forms the third floor [[Residential_and_mixed-use_buildings#Podium structures|transfer deck]]. “The project needed a transfer structure at this floor level as an entire row of concrete columns are removed necessitating the use of deep fabricated steel beams to transfer the load back to the steel columns below,” says Mr Patel.

All transfer beams at this level are at the same level as the top of the slab and designed as non-composite. Typically, the transfer beams cantilever out past the perimeter steel column below, picking up the full length of the concrete column above and supporting the [[Facades_and_interfaces|cladding]] line on the building perimeter.

The scheme is scheduled be to completed and ready in time for the start of this year’s autumn term.

==Topping the project==
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A sloping steel roof structure, designed with sightlines of the Houses of Parliament in mind, tops the building and incorporates the uppermost residences.

Slightly longer spans are required for this floor and so a lightweight steel solution was chosen. [[Steel_construction_products#Cladding and Roofing|Steel decking]] forms the roof itself and spans between steel beams providing them with lateral restraint. The roof beams are also designed to support a green roof.

Two [[Concept_design#Concrete or steel cores|cores]] provide [[Concept_design#Structural options for stability|stability]] along with two sections of [[Braced_frames#Vertical bracing|vertical cross bracing]] at the ends of the two ‘wings’. [[Braced_frames#Horizontal bracing|Horizontal cross bracing]] is provided at roof level to ensure the frame can span between the various vertical stability elements.

Several of the studios at level 18 contain duplex-style sleeping decks. These sleeping decks are designed as lightweight timber structures spanning between the room partitions.

“Getting the steel to the top of the building has been a challenge as we have 800 pieces of steel to erect,” says Bourne Steel Project Manager Iain Griffiths. “In order to reduce the number of crane lifts we’ve invested in two 3.5t capacity lifting cradles to enable the cranes to hoist a number of steel sections in one lift.”

{|class="wikitable" width="400"
|-
|'''Architect'''||Allford Hall Monaghan Morris
|-
|'''Structural Engineer'''||Ramboll
|-
|'''Steelwork Contractor'''||Bourne Steel
|-
|'''Main Contractor'''||Balfour Beatty
|-
|'''Main Client'''||Urbanest
|}

[[Category:Case studies - Education buildings]]