Northern Spire Bridge

Roughan & O’Donovan provided consultancy services - from tender through to completion of construction - for the permanent works structures on this large-scale infrastructure design and build scheme.

The bridge is 340m long and comprises a 24m-wide steel concrete composite deck, supported by a 1,550 tonne, 105m-high A-frame pylon, with sections of concrete and concrete/steel composite construction. 

It stands apart from traditional cable-stayed solutions in two ways:

1. Its central pylon was fabricated in one piece off site and transported by sea to the bridge site
2. Its deck was assembled in two sections alongside the bridge and launched in two separate phases across the river 

These innovations provided substantial benefits, in terms of construction and whole-life maintenance costs, to our client.

Major and minor structures designed to facilitate the scheme construction included:

• 140m long x 25m wide piled basal mattress
• Reinforced earth wall retained embankment up to 9 metres in height
• Retaining walls of sheet pile, contiguous bored pile and reinforced earth construction

The raising of the 105m high, 1550t steel/concrete pylon marked the culmination of two years of design and planning and 12 months of fabricating. A highly complex process, it required stringent geometric control and monitoring procedures.  

The pylon was raised into the vertical position using cables.  Temporary hinges were provided on top of the concrete ‘tusks’ at the base of the pylon to facilitate the lift.  A temporary back mast was fitted to the pylon and hoisted vertical from a barge using 4 number 450t capacity strand jacks. 

Not one critical trigger level was reached during the launch, which is testament to the joint venture's expertise in the design and interface co-ordination of complex permanent and temporary works on major bridge structures.

• Bridge engineering design
• Structural engineering design
• Geotechnical
• Temporary works
• Electrical
• Lightning protection
• Road engineering design