CCL designed the post-tensioned (PT) slabs for the Clatterbridge Cancer Centre in Liverpool to answer the very specific loading, deflection, and vibration criteria of the building design for this 11-storey specialist hospital.
The basement and ground floor levels used traditional reinforced concrete (RC) slabs. The remaining storeys, including the stepped cover slab, were designed and installed with PT, which significantly reduced the level of steel reinforcement by increasing the tensile strength of the slabs and reducing deflection in critical areas.
The vibration criteria for the project was crucial because of the need to accommodate highly sensitive equipment. Slab depth was increased from 325 mm to 450 mm in specific areas to provide sufficient concrete mass for the required vibration resistance. In critical areas, this was enhanced by stiffening with deep orthogonal beams.
A curved cantilevered section that extends around 8 m from the front of the main building and is supported by huge raking columns had to be tied into the PT slab. The design of the slab had to consider the significant horizontal forces created by the size of the cantilever and its unusual shape.
The impact of the horizontal forces was also a consideration for the level two slab where a large steel atrium meant that the forces from the steel structure at the void had to be incorporated into the slab design. An edge beam was installed around the perimeter of the void to manage the forces and control deflection.
The lack of raised access floors throughout the hospital required facade fixing brackets to be recessed c. 150 mm into the slab which necessitated careful liaison between the construction team, the facade designer, and CCL to coordinate the location of the PT anchors and tendons.DOWNLOAD CASE STUDY