Aarsleff Ground Engineering has completed a complex design and build foundations contract for a nursing home in Preston.
Contracted by Dynamic Building Solutions, Aarsleff’s scope of work included the design and supply of the piles and ground beams for a two-storey nursing home on a former car park at the Grasshoppers RFC site at Lightfoot Lane, Preston.
The foundation system comprised precast concrete driven piles to a 12m depth and 1200 linear metres of precast concrete ground beams. Aarsleff was also asked to install the piles for the foundation base for a tower crane that was to be erected to complete the superstructure build.
According to Aarsleff, the plan layout of the building was quite complex,as it was square in shape with an attached plantroom wing built around a central courtyard. There were internal loadbearing walls in different positions to each other coupled with staggered wall junctions and a lift shaft.
Aarsleff said: “Due to the complexity of the design, all pile loads were not to exceed 400kN. This led to several pile layouts being produced and considered so as to ensure the piles did not exceed the allowable loads whilst ensuring that the forces on the beams were kept to a manageable level without compromising the capacity or integrity of the beams.
“Dynamic Building Solutions also requested a specific sequence of construction of the beams in order to facilitate crane access that had to be adhered to. This required a further consideration in the design to ensure that the foundations could actually be constructed in a logical sequence whilst maintaining stability of the beams during installation.
structural analysis - Preston Aarsleff
“A late change by the client in the construction sequence meant that we had to act swiftly and check that the ground beam installation sequence as it stood was still viable, and with ground beams in production at this point, it was essential that any required changes to the beam design were done with the minimum of disruption to both the clients program and Aarsleff’s own casting programme.”
The piling operations were completed in 11 days, with the ground beam installation completed in five days - 290 piles and 1200m of ground beam installed in 16 days in total.