One of the new bridges will carry the Birmingham and Worcester Canal while the second, located adjacent to the canal bridge, will carry the Birmingham and Gloucester Railway line over the new relief road.
JOS Structures Ltd has used Harsco’s LOGIK® 60 modular wall panel formwork system to cast the mass concrete piers at either end of the two 70 m long bridges. LOGIK® 60 is ideally suited to projects such as this, the robust large-area system is designed for concrete pressures up to 60 kN/sq m. Individual panels are clamped rigidly together with Harsco’s unique ALL (aligning/levelling/locking) clamps which make the system very quick to assemble.
The two bridges both feature decorative architectural details, such as arched and fluted parapets, which must be finished to a very high standard. Consequently all the formwork panels (with the exception of the LOGIK® 60 system) were fabricated by JOS Structures Ltd carpenters entirely by hand.
“The thing about concrete in civil engineering projects is that it’s usually exposed, whereas in buildings it’s usually covered with cladding” comments JOS Structures Ltd managing director John O’Sullivan. “We have a reputation for high quality finishes and all the formwork panels for the exposed elements of these bridges have been hand-made in our workshop” he adds.
The main decks of both bridges were formed using Harsco’s genuine CUPLOK® and GASS® systems which, like LOGIK® 60, are quick and economical to use thanks to their modular design. The parapet and wing-walls were formed using DU-AL™ aluminium beams with MkII Soldiers used for vertical support.
Both bridges are being constructed in advance of the main work commencing on the new carriageway. The canal bridge has been built in its final location while the canal itself is temporarily diverted around it.
The railway bridge cannot be built in its final location as a full rail service must be maintained throughout the construction process. Instead, the bridge is being built alongside the track and will be picked up and slid into position during a 101 hour possession starting at midnight on Christmas Day.
The 70 m long, 3,846 tonne concrete structure is one of the biggest concrete structures ever installed in this way, says John Daft, project manager for main contractor Birse Civils. “At midnight on Christmas Day we take down the overhead power lines, lift the track and carry the new bridge into place on a series of self-propelled modular vehicles.”
The railway bridge is designed - by consulting engineer Tony Gee & Partners - to flex by up to 150 mm. “It has to be heavily reinforced to withstand the stress of being lifted as much as to support the trains that will travel over it” says Mr Daft.
Harsco secured the formwork package for this project as a result of its on-going framework agreement with JOS Structures Ltd. “We’ve had an agreement with Harsco for a few years now” says Mr O’Sullivan. “We’ve always used their equipment, not just for the quality of the materials but also the technical backup and drawing services, which are excellent”.
When both bridges are completed, Birse Civils will begin excavating the 40,000 tonnes of material from the 15 m high, 100m wide embankment built in 1796 to carry the canal before driving the new road underneath.