250 City Road

Not only was a 20 m long x 5 m deep RC transfer beam a part of the value engineering solution, but it also showcased our design team’s innovativeness. This key structural element was located in the basement and designed to support a vertical load of 3607 tonnes, including two of the tower column loads, and distribute these loads onto the new basement secant piles.

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To verify the beam’s structural adequacy, we utilised the compatible stress field method (CSFM): anew analysis technique developed by Prof. Dr. Walter Kaufmann and his team at the ETH Zurich Institute of Structural Engineering that has been implemented in the recently released Idea StatiCa Detail software. This is believed to be the first time a UK-based design office has used this efficient method on a live project.  

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Our piling work included the design and construction of a 110 m perimeter cantilever secant piled wall for a double level basement for car parking and plant rooms along with 270 bearing piles to support the superstructure.

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We designed the piles in-house, fully coordinating with the client and their structural engineers. Our work, which involved the installation of secant piles from a high-level platform and subsequently the relocation of plant and equipment to the lower basement levels to install the bearing piles, was sequenced to suit the phased release of various areas.

Piles were installed to depths of 32 m, using our 100 ton Soilmec SR-95 high-torque multi-discipline piling rig by the continuous flight auger (CFA) method.  

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In order to tie into perimeter secant piles installed in a previous phase where access was restricted, we mobilised a Klemm 709 mini piling rig.  We also undertook restricted access mini piling for a tower crane base where there was limited headroom and mobilised a Klemm 702 mini rig.

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The site's location presented some challenging logistics. It was adjacent to a TfL Red route and located above a busy London Underground station with several lines converging at at Old Street. Particular care was therefore required to protect LUL assets during the demolition of the existing basement which involved the removal the existing ground floor slab, columns and basement slab along with the subsequent excavation and piling for a double level basement.

‍

The 37-storey tower was constructed using a jump form system and a mixture of insitu RC (blade) walls and precast columns, which were fabricated in-house. Reinforced concrete slabs were constructed to level 8. From levels 9 to 37, slabs were post-tensioned and designed in-house.

‍

Not only was a 20 m long x 5 m deep RC transfer beam a part of the value engineering solution, but it also showcased our design team’s innovativeness. This key structural element was located in the basement and designed to support a vertical load of 3607 tonnes, including two of the tower column loads, and distribute these loads onto the new basement secant piles.

‍

To verify the beam’s structural adequacy, we utilised the compatible stress field method (CSFM): anew analysis technique developed by Prof. Dr. Walter Kaufmann and his team at the ETH Zurich Institute of Structural Engineering that has been implemented in the recently released Idea StatiCa Detail software. This is believed to be the first time a UK-based design office has used this efficient method on a live project.  

‍

Our piling work included the design and construction of a 110 m perimeter cantilever secant piled wall for a double level basement for car parking and plant rooms along with 270 bearing piles to support the superstructure.

‍

We designed the piles in-house, fully coordinating with the client and their structural engineers. Our work, which involved the installation of secant piles from a high-level platform and subsequently the relocation of plant and equipment to the lower basement levels to install the bearing piles, was sequenced to suit the phased release of various areas.

Piles were installed to depths of 32 m, using our 100 ton Soilmec SR-95 high-torque multi-discipline piling rig by the continuous flight auger (CFA) method.  

‍

In order to tie into perimeter secant piles installed in a previous phase where access was restricted, we mobilised a Klemm 709 mini piling rig.  We also undertook restricted access mini piling for a tower crane base where there was limited headroom and mobilised a Klemm 702 mini rig.

‍

The site's location presented some challenging logistics. It was adjacent to a TfL Red route and located above a busy London Underground station with several lines converging at at Old Street. Particular care was therefore required to protect LUL assets during the demolition of the existing basement which involved the removal the existing ground floor slab, columns and basement slab along with the subsequent excavation and piling for a double level basement.

‍

The 37-storey tower was constructed using a jump form system and a mixture of insitu RC (blade) walls and precast columns, which were fabricated in-house. Reinforced concrete slabs were constructed to level 8. From levels 9 to 37, slabs were post-tensioned and designed in-house.

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