For our participation in the Solar Decathlon Middle East 2018, we were challenged to design, build and operate a prefabricated and demountable sustainable zero energy house. As structural design sub team, we were also facing other specific challenges, for example the enormous average wind speeds in the desert of Dubai and a maximum construction and installation time of only fifteen days.
Due to the high tensile loads it was clear to see at an early stage that securing the structure from the tensile forces, a ground anchor was needed. Keeping to the Solar Decathlon Middle East 2018 rules and regulations, Spirafix was found to be a perfect solution for this temporary foundation. Offering easy installation/removal, whilst achieving the minimum load needed.
The shape of the architectural design of LINQ, shown in Figure 1, combined with prescribed extreme wind loads of 45 m/s appeared to result in extra high reactions, tensile forces, in the foundation structure. The design of the temporary foundation is based on flexibility for demounting, transporting and rebuilding, which means the entire foundation is easily demounted into manageable parts. The foundation consists of steel profiled beams on top of adjustable lightweight footings. All these beams are connected to the central foundation module, which provides stability and gives the starting point for measuring. This central module is combined with another steel core module inside the house, to bear most loads from the roofs and provide stability of the entire structure. As shown in Figure 2, the steel foundation beams are cantilevering on all edges of the house plan, so the module and footings are not visible to the audience.
The ground being hard, the anchors did not turn into the ground as they should and therefore was reflecting in their loading capacity.
A different approach was taken to use a small electric post driver, which appeared more convenient and much faster than a manual installation. With the multiple small impacts that a post driver provides the anchors did turn into the ground and was therefore reflected in the installation and load results being successful.
The anchors were connected to the structure using steel wire rope and wire clamps.
"In general, the Spirafix anchors were very convenient to install and connect during construction and deconstruction, provided that the anchors are mechanically installed using some type of post driver. Attention should be paid to protecting the fitting top parts while installing or deconstructing the ground anchors. Since tensile resistances seem to depend highly on the type of soil substance, specific tensile tests will give better insight into the structural effect of the Spirafix anchors for locations with unknown soil types or when extra precise calculations are required." Carmen Korevaar