View source for Eleven York Street, Manchester

==Article in [http://www.newsteelconstruction.com/wp/wp-content/uploads/digi/NSC_Mar20digi/pubData/source/NSC_Mar20digi.pdf#page=22 NSC March 2020]==
{{#image_template:image=File:Eleven_York_Street-1.jpg|align=right|wrap=true|caption=How the latest [[Multi-storey_office_buildings|commercial scheme]] in Manchester will look |width=300}}
'''Prime offices spur regional activity'''<br>
Manchester’s [[Multi-storey_office_buildings|commercial sector]] has seen record levels of activity in recent years and Eleven York Street is one of the projects set to complete this year.<br>
''By Martin Cooper''<br>

Greater Manchester’s skyline has been awash with [[Construction#Tower cranes|tower cranes]] for a number of years as the city continues to experience record levels of [[Construction|construction]] activity. A total of 27 schemes, predominantly in the commercial and [[Residential_and_mixed-use_buildings|residential sectors]], were completed in 2019 and a further 47 completions are expected this year. Although these figures are impressive, they are slightly down on the record levels of activity experienced in 2018, according to the latest research from Deloitte.

The company’s 2020 Crane Survey reported that Manchester’s [[Multi-storey_office_buildings|commercial office]] sector remained most resilient across all UK cities with approximately 190,000m<sup>2</sup> under [[Construction|construction]] for a second successive year. Investment in the central Manchester office market remains high as the city is seen as an ideal location for new and expanding companies, that require a north of England headquarters.

One of Manchester’s city centre [[Multi-storey_office_buildings|commercial schemes]] due to complete by the end of 2020 is Eleven York Street, an eight-storey building that will offer 7,300m<sup>2</sup> of floor space. Designed to achieve a [[BREEAM|BREEAM]] ‘Excellent’ rating, the structure will have seven office floors, a ground floor accommodating two retail units and a main lobby, as well as a basement offering space for 23 cars.

Main contractor Kier started on site during 2018, with the demolition of the previous five-storey concrete-framed building. Replacing, what had become a very tired-looking structure, the designs for the new build always envisaged a [[Braced_frames|steel-framed]] building, according to Tier Consult Engineer Robert Harmston. “The client wanted long span, [[Multi-storey_office_buildings#Flexibility and adaptability|column-free office space]], and this is best achieved using structural steelwork. The material also gives the project team valuable [[Multi-storey_office_buildings#Speed of construction|speed of construction]], which is always an important consideration on any scheme.”
{{#image_template:image=File:Eleven_York_Street-2.jpg|align=left|wrap=true|caption=Leach initially [[Construction#Steel erection|erected]] the [[Concept_design#Concrete or steel cores|steel core]]|width=300}}
Once demolition had been completed, the new building’s foundations were installed, which included a contiguous piled wall and a series of CFA piles, installed to a depth of up to 14m. This then allowed the steelwork programme to kick-off , which required Leach Structural Steelwork to [[Fabrication|fabricate]], supply and [[Construction#Steel erection|erect]] 890t of steel over a period of 21 weeks.

“Logistics have been one of the main challenges for the project, especially for the [[Fabrication#Handling and transportation|delivery of steelwork]] and other materials,” says Kier Project Manager Lee Williams. “We are surrounded by a number of narrow and busy streets, which need to be negotiated by our trucks, so any bad parking can cause havoc to our deliveries.”

Unlike many [[Multi-storey_office_buildings|commercial schemes]], Eleven York Street has a [[Concept_design#Concrete or steel cores|steel braced core]], which accommodates staircases, lifts, risers and toilets. It also provides the building’s main frame with its [[Concept_design#Structural options for stability|stability]], and was chosen over a more traditional [[Concept_design#Concrete or steel cores|concrete core]] for commercial reasons. “It may have been difficult to get a contractor to install a concrete core as there is so much [[Construction|construction]] work underway in the city,” says Mr Harmston. “Plus, a [[Concept_design#Concrete or steel cores|steel core]] has programme benefits, whereby the project team didn’t have to wait for a concrete contractor to finish its work before beginning the [[Construction#Steel erection|steel erection]] as it was all part of the same programme.” For this reason, the [[Concept_design#Concrete or steel cores|steel braced core]] was the initial part of the building to be [[Construction#Steel erection|erected]]. It was installed to its full height and, once completed, it then allowed the remainder of the structure to be installed by providing the frame’s [[Concept_design#Structural options for stability|stability]].

Although centrally-positioned, the [[Concept_design#Concrete or steel cores|core]] is offset and located along one of the building’s main elevations, thereby creating more valuable floor space. After the [[Concept_design#Concrete or steel cores|core]], Leach Structural Steelwork [[Construction#Steel erection|erected]] the main steel frame by dividing the structure into two further phases, with each one [[Construction#Steel erection|erected]] bay-by-bay and to the full height of the building.
{{#image_template:image=File:Eleven_York_Street-3.jpg|align=right|wrap=true|caption=A large [[Steel_construction_products#Plate girders|plate girder]] creates the column-free entrance|width=300}}
Radiating out from the [[Concept_design#Concrete or steel cores|core]], each of the floor’s long clear spans are formed by a series of Westok [[Steel_construction_products#Cellular beams|cellular beams]], up to 15m in length. The choice of using Westok beams was made because the cellular sections are able to fully [[Service_integration|integrate the services]] within their depth, maximising the structure’s floor-to-ceiling heights, while also being economic as they are lighter than traditional [[Steel_construction_products#Standard open sections|UB sections]]. The Westok beams were optimised to adhere to the strict 660mm-depth restriction imposed on the floorplate. To facilitate the passage of the services, a cell pattern of 425mm-diameter holes at 600mm centres was provided, along with some discreet wider elongated cells. Kloeckner Metals UK Westok Design Team Manager John Callanan commented, “We continue to see a steady stream of clear-span [[Multi-storey_office_buildings|commercial office developments]] in Manchester and Salford, and it was great to work with the project team on this job.” 

The building’s [[Design|design]] contains just one solitary internal column, located in an area where the span would have been greater than 15m. Without this column, the span would have needed a beam with dimensions much greater than the other beams, and this would have interfered with the structure’s overall floor-to-ceiling heights. For this reason, the decision was taken to allow the one column to invade the otherwise open-plan floorplates.

All of the steelwork has been [[Construction#Steel erection|erected]] using the project’s one [[Construction#Tower cranes|tower crane]], and so all individual sections had to be within the crane’s capacity. To this end, the heaviest pieces of steelwork, other than the [[Steel_construction_products#Cellular beams|cellular beams]] which weigh up to 9t, is a series of transfer [[Steel_construction_products#Plate girders|plate girders]]. The heaviest of these is 9.6t and it is positioned close to the [[Concept_design#Concrete or steel cores|core]], where the structural loads are deemed to be too great for a [[Steel_construction_products#Cellular beams|cellular beam]] to support. There is another 5t plate girder positioned at the underside of the second-floor level that creates a cantilever over the entrance’s double-height space, while a further transfer girder is positioned at sixth floor level to form a set-back in the structure along its northern elevation to form an outdoor maintenance terrace.

Eleven York Street is due to be complete by the end of the year.

{|class="wikitable" width="400"
|-
|'''Architect'''||AHR
|-
|'''Structural Engineer'''||Tier Consult
|-
|'''Steelwork Contractor'''||Leach Structural Steelwork
|-
|'''Main Contractor'''||Kier
|-
|'''Main Client'''||Kier Property
|}

[[Category:Case studies - Multi-storey office buildings]]