Astor College is located on Charlotte Street in the London Borough of Camden.  The existing buildings at the site include a 9 storey student accommodation block, built in the 1960s and extended in the 1970s.  The works include significant structural alterations to the existing building, the construction of a new 8 storey extension to the rear, and a new extension to the front.

Galliford Try, the contractors, appointed Michael Barclay Partnership to develop the early stage 
structural proposals for the scheme.  The construction cost is approximately 22m.  Demolition and piling works commenced in February 2017 and project completion is planned for the summer of 2018.
 
The rear extension is a reinforced concrete frame on piled foundations.   We used ETABS and SAFE 3D structural modelling software packages to develop an efficient and practical structural design for the frame.  In doing so material savings were made; the thickness of the reinforced concrete slabs reduced by 25 percent and the quantity of piles reduced by 20 percent.

The existing building has a loadbearing masonry structure above 2nd floor level and a reinforced 
concrete structure below.  The foundation is a reinforced concrete raft founded on both gravel 
deposits and made variable ground.  The proposals include the construction of the front extension and the removal of several multi-storey shear walls.  Extensive investigation works were carried out to confirm the form and condition of the structure, and the feasibility of the alterations.   A steel sway frame, stiffened with vertical bracing, is adopted to replace the demolished walls and to form a lightweight structure to the front extension.  The new extension’s weight is carefully distributed to avoid strengthening the existing foundations. 
The new and existing building structure is modelled in Autodesk Revit BIM software to BIM level 2.  A federated model is used for co-ordination of the design with the other members of the team.  The proposed scheme aims to achieve a BREEAM Good rating.  The drainage system is designed to 
make use of the existing building’s infrastructure and rainwater flows from the site are attenuated by 
a blue roof to the new rear extension.  The concrete specification for the project allows the use of cement combinations and recycled aggregates, where practicable and deemed to lower the CO2 content.