New Birchenough bridge on the cards

New Birchenough bridge on the cards
Published: 11 January 2018
GOVERNMENT is to construct a new bridge at Birchenough Bridge to replace the current one, which has outlived its lifespan.

This was disclosed by Transport and Infrastructure Minister Jorum Gumbo, who said the cost of constructing a new bridge was almost equal to the cost of rehabilitating the existing one.

According to a survey conducted by the Zimbabwe National Roads Authority (ZINARA), it would cost $35 million to rehabilitate Birchenough Bridge and $40 million to construct a new one.

"We opted to build another bridge as opposed to maintaining the existing one after carefully looking at the cost of both. So we are looking for funds to construct another bridge," said Gumbo during a ZINARA update meeting.

Birchenough Bridge was built in 1935 at a cost of 145 000 British pounds and planned under the Beit Trust — a foundation chaired at the time by the late Sir Henry Birchenough.

In the 1970s, a 40-tonne load limit was imposed on the bridge before it was widened to 10 metres from 7,2 metres in 1984 and strengthened as part of the World Bank's Highway Project One.

Since then, the bridge has deteriorated with no meaningful rehabilitation, such that government imposed a 25 load limit with vehicles taking turns to pass.

This has greatly affected business as haulage trucks are not allowed to pass the bridge, thereby reducing business activity.

"Another factor is the width of Birchenough. We would rather have a two way bridge there, considering the continuous increase of traffic on our roads and that route as well," Gumbo said.

Birchenough Bridge, 120 kilometres south-east of Mutare, straddles the Save River and connects Chipinge and Buhera districts.

The bridge offers passage to vehicles to and from Masvingo and Beitbridge.

Gumbo did not say whether the $232 million allocated for road maintenance this year would include the construction of the new bridge.

Last year, only $148 million was budgeted for road projects, and $95 million of that was utilised.

Birchenough Bridge is one of many projects listed by Wonders of World Engineering, a weekly magazine which appeared between 1937 and 1938, described the bridge as an invaluable link in the communications of Zimbabwe. Its imposing steel structure is one of the longest single-arch span in the world.

When it was built, it became the third longest single-arch bridge in the world, second only to the Sydney Harbour Bridge and to the Bayonne Bridge, New York, according to Wonders of World Engineering.

The total length of the Birchenough Bridge is 1 240 feet and the great arch that rises 280 feet above the river measures 1 080 feet between the foundation bearings.

The depth of the arch crown is 37 ft 6 in and the end posts are 46 feet high, according to details from the magazine.

The width between the arch trusses is 45 feet, and the top and bottom chords are provided with lateral diagonal bracing to resist wind pressure.

The arch trusses comprise twenty-seven panels, braced N-fashion, so that the upper and lower chords are diagonally braced.

The main cross girders of the deck, placed 40 feet apart, are suspended at either end from the arch by steel cables of 2¾-in. diameter.

These cables were used as anchorages during the building of the arch and previously in the building of Sydney Harbour Bridge, the hangers of which comprise steel girders and not cables.

Thus the great steel ropes that travelled more than half-way round the world and back have found a permanent resting place in the heart of Africa.
- fingaz
Tags: Bridge,


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