Here’s another solution we developed in collaboration with our client Techrete (UK), who were employed by Kier (Main Contractor) to carry out the precast concrete cladding package on the new Facebook HQ in Kings Cross. During their site operation Techrete had to run a 20T MEWP along the South Elevation and it was identified that a load spread solution was required.
The machine selected was a JLG 1250AJP Articulating Boom Lift, which has a maximum platform height of 38.30m (125 ft 8 in) and horizontal reach of 19.25m (63 ft 2 in). Something we had to overcome was the extendable/retractable axles. When the axles are retracted, the machine width is 2.49m (8 ft 2 in) and when the axles are extended the machine width is 3.81m (12 ft 6 in). The latter provides stability during operation – but there was also a pinch point at the foot of the tower crane base where the machine needed to track, midway along the front elevation. To ensure the axles could be extended/retracted we introduced two layers of thin plastic mats on-top of our Aluminium ALIMATS® system, either side of the tower crane base – this reduced friction during this operation.
Before being awarded the work, we had to demonstrate the axles could extend/retract without disturbing the ALIMATS®, which were the load spread layer below the plastic layer. So, we carried out a simple test near our training centre, utilising a JCB as shown in the video. The actual platform is shown on drawing GA04, and the extent of the platform provided is shown on drawing GA07. With all MEWP’S there are two load cases that need considering – Tracking and Operating. The latter imposing loads similar to mobile crane outriggers, but via the wheels. Both conditions were considered in our proposal, and this is what was approved for use.
With this type of solution, our patented interlock comes into its own, as it ensures load spread is achieved between modules whilst the machine is tracking. When the machine is operating, additional layers are applied to ensure the load spread system functions the same as outrigger mats, but under the wheels.