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Contractors World UK & Ireland Vol 6 No 1

15

between lifting positions.

DLT has developed and carried out detailed design

of the gantries, including the lifting tackle, deck anchor-

ages, deck segment adjustment and advancement M&E

systems.

There are 3 spans of 223 m, 104 m and 101.5 m be-

tween the north tower (NT) and the north abutment

(NA) passing over two piers N1 and N2. The transition

between single cable stayed box girder and the twin box

girders is located just to the north of the last pier N2.

The last 222 m of deck weighing 6400 t including this

transition is to be erected by launching from behind NA.

A king post and stay system is used to allow the deck

to cantilever the full span length. The launch support

bearings have to be changed during the launch to ac-

commodate the transition in deck form. An unusual

feature of the launch occurs towards the end when the

nose is lifted to pass over the last pier by sliding the rear

end down temporary ramp walls built in the north

abutment

DLT has developed and detailed the launch scheme,

including permanent works interfaces and all temporary

works, and will provide site support during launching.

Deck Support Falsework at Piers S1

and S2

Erection of the deck segments over the southern ap-

proach piers S1 and S2 requires extendable falsework

to support and adjust the position of the pier deck seg-

ments to allow closure between them and the main

cantilever deck.

After the pier segment has been lifted onto the false-

work, by the Erection Traveller, it is slid south over the

pier to generate sufficient space to lift a further

segment.

Subsequently, the pier segment is moved north to

connect it to the previously erected deck. The required

longitudinal movement range is approximately 5 m.

There is also a requirement for hydraulic vertical supports

to control the loading and in order to transfer the weight

of the segment from the temporary supports onto the

permanent bearings.

DLT has developed the concept and is now carrying

out detailed design of the temporary works, permanent

works interfaces and equipment specification.

© 2015 Dorman Long Technol

Top: Deck erection gantry manufacture model

Middle: Detail of lifting strand jacks and plan align-

ment rams

Bottom: Detail of deck lifting frame with slope adjust-

ment rams.

Contractors World UK & Ireland