A first for SDC...

The jacking process carried out at St Catharine’s College was a first for SDC. Keep an eye on the jacks in the video to see them move, and read below to find out how it's done..

Following the installation of the new steel frame, 3 steel cradles were connected to the 3 pairs of steel beams, located directly below the second floor structure.

Hydraulic jacks were 'sandwiched' within each cradle, centrally located below the existing RC beams. These jacks were then individually pressurised at ever-increasing, and carefully designed loads. As the jacks expanded, they pushed upwards against the soffit of the RC beams, which in turn pushed the cradles downwards, pulling the main supporting steel beams down too. 

This operation continued until the equalisation of the loads being applied from the building above, matched the loads being exerted from the 3 jacks pushing/pulling the steel frame below. Equalisation was achieved when the downwards movement of the steel beams stopped and the existing building structure actually began to move upwards! Don’t panic, it only moved a quarter of a millimetre!

The jacks were then locked off and the dry-packing process commenced. This will hold the pre-stressed steel frame in place, ensuring the whole system becomes fully integrated with the existing structure, allowing us to remove the temporary propping!