The steel beams positioned on the piles have to be encased in concrete to both prevent corrosion and also provide stiffness against twist from any lateral forces of the building structure. As the steel beams are above ground, everything has to be shuttered to hold the concrete when it’s poured. All the shuttering is installed with all dimensions correct. The top level of the finished concrete has been checked to be level across the site to be within 2.5mm between highest and lowest points.
A further step has been welding on steel stub fabrications which provide attachment points for the steel columns in the building frame. These take building load from the roof and first floor downwards to the foundations. To make sure that the bolts attaching the steel columns align correctly, the steel stubs have to be located with a 2mm tolerance in all three axis, an order of magnitude lower than timber frame. This alignment has to be maintained through the follow on operations to make sure the steel frame will fit without the need for onsite alteration. A system of reference points have been installed around the site and these, along with laser surveying will be used to check alignment measurements.
The next challenge will be to spot a block of successive dry days with above zero temperatures at day and night for the next stage.