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Queensferry Crossing - Erection

Engineering

The Queensferry Crossing is currently under construction for

client Transport Scotland by contractor Forth Crossing Bridge Constructors

(FCBC), a consortium of Hochtief Solutions, American Bridge International,

Dragados, and Morrison Construction.

The Main Crossing consists of a new road bridge across

the Forth estuary spanning 2,637.5 m between abut-

ments. It is a cable stayed bridge with three mono-tow-

ers, two main spans of 650 m and approach spans to

the north and south. The single level deck is continuous

from abutment to abutment.

Over the cable stayed length it is a single composite

box girder but for the southern approach viaduct and

the last span at the northern end it splits into twin com-

posite box girders.

DLT is the temporary works designer for three key

elements of the main bridge construction, the Approach

Viaduct North (AVN), the cable stay bridge deck erection

gantries, and deck support falsework at piers S1 and S2.

Deck Erection Gantries

The cable supported composite box deck sections

for the main bridge are pre-assembled at the site and

transported by barge to their respective erection points.

There are 109 sections in total ranging in length from

6.1 m to 16.2 m and weight from 260 tonnes to

780 tonnes. They are lifted approximately 50 m from

the delivery barge to permanent deck level. This is

achieved using 6. temporary deck erection gantries using

strand jack technology for lifting.

The unusual aspect is the need for the gantries to fit

between the 2 planes of stay cables that are only 4 m

apart in the central section of the bridge. This has led

to a very slender structure that needs sophisticated

control systems to limit eccentric loading from the lifting

strand jacks and retractable feet to allow it to advance

Contractors World UK & Ireland Vol 6 No 1

14

Contractors World UK & Ireland