View source for Principal Place Commercial, London

==Article in [https://www.newsteelconstruction.com/wp/wp-content/uploads/digi/2016pdf/NSC1606digi.pdf#page=22 NSC June 2016]==
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'''The principal of steel'''<br>
Located on a prime central London plot, the 15-storey Principal Place Commercial is a landmark [[Multi-storey_office_buildings#Mixed use commercial buildings|mixed-use development]] utilising steel construction’s flexibility.<br> 
''By Martin Cooper''<br>

Sitting just to the north of the City of London boundary, Shoreditch has in recent times transformed itself from a run-down former manufacturing district into a trendy and fashionable area that now seamlessly merges with the nearby business-dominated streets. Taking advantage of Shoreditch’s proximity to the Square Mile, a number of [[Multi-storey_office_buildings|commercial developments]] have sprung up, including Principal Place Commercial, a landmark 15-storey development being built by Brookfield Multiplex.

Designed by Foster + Partners the 79,000m<sup>2</sup> scheme offers efficient and high density Grade A space with typical floors of 4,100m<sup>2</sup>. The building will also offer retail space within its ground floor area. The [[Braced_frames|steel-framed]] building will also feature a 1,400m<sup>2</sup> reception area and a significant public realm, as well as two roof terraces exclusively for tenant use. All of these attributes, and with the City of London literally next-door, have persuaded Amazon, the global on-line retailer to pre-let 40,000m<sup>2</sup> of space at Principal Place.

A project on this site had been mooted for a number of years and a previous developer did begin preliminary works and installed a significant quantity of steel to form a [[Bridges|bridge]] over the railway lines into Liverpool Street Station. This ground level grillage of steel beams has now been incorporated into the Principal Place job, as it will form the entrance to the new building and a support for the public realm.

Brookfield Property Partners acquired the site in 2012 and immediately reviewed and improved the overall [[Design|design]] with significant changes to the [[Facades_and_interfaces|façade]] and interior of the scheme. “Principal Place was always going to be a [[Braced_frames|steel-framed]] building, but our [[Design|design]] changes have enhanced the building and its [[Multi-storey_office_buildings#Value for money|cost-effectiveness]],” explains Brookfield Multiplex Project Director David Jordan.
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sight lines|width=300}}
Prior to the [[Construction|construction]] programme starting, sports pitches most recently occupied the plot, although in the past it had been the site of a railway yard and one of Europe’s first gasworks in the early 19<sup>th</sup> Century. “The industrial past of the site meant we had to remediate parts of the site before we could start on the building’s substructure,” adds Mr Jordan. The site’s history went back further than Georgian times as Mr Jordan adds. “As with many central London projects, an archaeological dig was also undertaken and quite a few medieval and Roman artefacts were recovered.”

Steelwork for the superstructure begins at basement level, so once this had been dug out and the slab cast, Severfield was able to begin its [[Construction#Steel erection|steel erection]] programme. 

The centrally-positioned concrete [[Concept_design#Concrete or steel cores|core]], that provides the [[Braced_frames|steel frame]] with its [[Concept_design#Structural options for stability|stability]], was more than 60 percent complete when the steelwork package started. To allow both of the site’s [[Construction#Tower cranes|tower cranes]] to be used for the [[Construction#Steel erection|steel erection]], a third crane was temporarily installed by Brookfield Multiplex to serve the [[Concept_design#Concrete or steel cores|core]] construction.

“One of the main challenges for us was the installation of the basement to first floor columns,” says Severfield Associate Project Director Steve Dobbs. “They were [[Construction#Steel erection|erected]] and left free-standing while the reinforced ground floor slab was cast around them, as [[Construction#Steel erection|erecting]] them after the slab was cast would have been very difficult.” To allow the columns to free-stand, a series of large [[Moment_resisting_connections#Column bases|base plates]] was initially installed, these each measured 1.5m × 1m and weighed close to 1.5t each. Once the [[Moment_resisting_connections#Column bases|base plates]] were in place the columns were then attached via a [[Welding|welded]] connection.

Within the double-height basement a [[Braced_frames|steel-framed]] [[Single_storey_industrial_buildings#Mezzanines|mezzanine]] deck was also installed along with the main columns. This extra level will primarily support cycle storage facilities and plant areas.

The [[Braced_frames|steel frame]] has been [[Construction#Steel erection|erected]] around a 10.5m x 10.5m [[Concept_design#Floor grids|grid]], offering quite a lot of repetition as the [[Braced_frames|steel frame]] went up. Two of the main features are the double-height entrance foyer that incorporates a first floor that is setback to overlook the main doors, and large 4.5m deep cantilevers that run along both of the building’s main elevations.
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One of the enhancements to the original [[Design|design]] was the addition of these two cantilevers. The columns have been set back to form these overhangs and increase the floorplates above. An added benefit has been the creation of a sheltered pedestrian walkway along the Worship Street elevation. “A lot of work and coordination was required so we could agree the cantilever deflection criteria with the cladding contractor,” says WSP Parsons Brinckerhoff Project Engineer Andrew Woodward.

The building has a step at level 10 that creates one of its roof terraces on this western portion – the other terrace sits atop level 15 on the eastern side. As well as forming an interesting [[Design|design]] feature, viewing corridor regulations also stipulated a lower part of the structure at the western side.

During the initial [[Construction#Steel erection|steel erection]] programme both of the site’s [[Construction#Tower cranes|tower cranes]] were positioned within the structure’s two [[Steel-supported_glazed_facades_and_roofs#Atrium Roofs and Sky lights|atriums]]. However, once the steelwork had progressed past level 10, Brookfield
Multiplex decided to reposition the [[Construction#Tower cranes|crane]] on the western side in order to help speed up the [[Multi-storey_office_buildings#Fa.C3.A7ade_systems|cladding]] installation within the [[Steel-supported_glazed_facades_and_roofs#Atrium Roofs and Sky lights|atrium]]. In order to support the [[Construction#Tower cranes|tower crane]] on the [[Braced_frames|steel frame]] at level 10, Severfield designed, [[Fabrication|fabricated]] and installed a bespoke steel grillage.

Also at level 10 the main [[Concept_design#Concrete or steel cores|core]] decreases in size as there are less services to accommodate for the upper floors. “This means the steel piece count actually increases for the upper levels as more steel components were required to infill the area above the core,” adds Mr Woodward. “Plus the roof has a significant amount of steel to form plant enclosures and a Building Maintenance Unit (BMU) support system.”

Principal Place is targeting a [[Sustainability#Understanding BREEAM|BREEAM ‘Excellent’ rating]] and is scheduled for completion by the end of the year.

==Principal Tower==
In addition to the [[Multi-storey_office_buildings|office building]] and the half-acre public piazza, there is also a significant residential component to the development, also being built by Brookfield Multiplex but under a separate contract for Brookfield Property Partners and Concord Pacific.

Principal Tower, the 50-storey luxury residential establishment at Principal Place, will be Foster + Partners’ first fully designed residential tower, reaching 175m, making it one of the tallest [[Residential_and_mixed-use_buildings#Residential buildings in urban areas|residential buildings]] in Central London.

Severfield will be installing a steel [[Residential_and_mixed-use_buildings#Podium structures|transfer structure]] that will support the concrete tower as it cantilevers over the rail lines that serve Liverpool Street Station. The residential tower will be completed in 2018.

{|class="wikitable" width="500"
|-
|'''Architect'''||Foster + Partners
|-
|'''Structural Engineer'''||WSP Parsons Brinkerhoff
|-
|'''Steelwork Contractor'''||Severfield
|-
|'''Main Contractor'''||Brookfield Multiplex
|-
|'''Main Client'''||Brookfield Property Partners
|}

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