Costain has used the UK’s largest mobile crane to install the main deck girders for the Clydach River Bridge.
The bridge, located in Saleyard, is part of the Heads of the Valleys project to create a dual carriageway on the A465.
Costain used the 1,200t capacity Gottwald AK680-3 to move six 70m span weathering steel main plate girders. Sarens Group was tasked with carrying out the lifting.
Girders were joined together in pairs with bolted splices and internal bracing to create 4m high beams that weighed 160t. These were lifted by the crane into place on the bridge abutments in preparation for a precast concrete deck due for completion later in the year.
The completed piled integral steel composite bridge will have a single 67m clear span across the River Clydach.
“Usually the next stage would be to put up permanent formwork and cast an in-situ deck. Instead, the whole deck will be precast in sections in a compound on site,” said Dave Morris, structures manager, Costain.
“Over a single day we have seen the steel lengths increasing by 15-20mm as they expand and contract in relation to the temperature extremes of the weather,” he added. “A key sequence of work is to get the timings right to grout the thrust plates in and cast the main diaphragms that will effectively lock the steel beams into the bridge at the required length.”
“After the diaphragms are cast and deck slabs are installed and stitched together we can then waterproof it, put on the parapets and handrails and install the full road surfacing.”
The bridge is expected to be completed in late March 2017.