PCE’s Offsite engineered Hybrid structure

An innovative two storey offsite engineered Hybrid concrete structure erected by PCE Ltd in Durham provided a new data, IT and Marketing office centre for City Electrical Factors (CEF).

Featuring internal exposed concrete surfaces, clear spans with the concrete units providing control of the building’s internal environment, which proves the use of concrete for smaller sized buildings.

Structural concrete

For the two storey building, Architects FaulknerBrowns chose structural concrete as the principal construction material including the roof structure, the first floor having two separate and distinct floor areas separated by an atrium area, one being rectangular of 52m x 15m and the second being “L” shaped with side lengths of 70m and 31m with a 9m width.

Both suspended areas are linked at floor level by three bridging walkways.

Three important aspects of the design requirements were: 

1. Clear span requirements of the working floor areas, with flat soffits to both the suspended 1st floor and roof structure,
2. The incorporation into the structure of an embedded pipework system in soffits of the concrete first floor and roof, to provide thermal control of the internal environment,
3. The need to have high quality exposed concrete finishes.

A Kit of Parts

Main contractor Sir Robert McAlpine won the tender competition to bring the design to life. PCE put forward an Offsite engineered Hybrid structural solution utilising its “kit of parts” approach to develop a bespoke solution that met the overall design requirements for the project and this led to PCE being appointed on a design and build basis to construct the buildings structural frame.

The two lift and stair cores were constructed using PCE’s PreFastCore modular system providing a safe, fast and dimensionally accurate solution, erected full height at the start of the construction process which gave stability to the structure as well as providing safe access for construction personnel to the first-floor level as work proceeded.

Additional precast concrete shear walls were also used to provide stability where required.

Thermally Active Building System incorporated into the soffit of the PCE GT flooring units

GT flooring system

For the precast concrete flooring and roofing units, PCE chose to use their own GT flooring system which was initially developed by the company to provide a long, up to 16m, clear span option for car parks and has been extensively used for such.

1,424m² of 400mm deep GT units were used for the 14m clear span whilst 1,441m² of 250mm deep GT units were used for the 8.0m clear span. The GT concrete units are designed so that no structural concrete toppings are required and thus their use reduced further additional onsite activities and programme time.

The bridging walkways between the two first floor areas were also formed of GT units.