Our Rhodesian Heritage

Memories of the building of of Birchenough Bridge

Inner Page of Cover

IT has given me great pleasure to be asked to contribute a foreword to this booklet which is being issued as a Souvenir of the opening of the Birchenough Bridge. Sir Henry Birchenough is well known to all Rhodesians as one whose unremitting sympathy with the progress of our country and whose invaluable assistance, as Chairman of the Beit Trustees, in matters tending to its development, make it most fitting that this great Bridge should bear his name.

Once again we acknowledge the debt we owe to Alfred Beit, the far-seeing provisions of whose Will have made the building of this Bridge possible, a Bridge which will, I am sure, prove of inestimable benefit to the Eastern Districts of the country by bringing them into closer touch with their markets and with the rest of Rhodesia, and will facilitate the flow of tourist traffic to one of the most beautiful and fertile portions of the colony.

Prime Minister

The
birchenough bridge

THE magnificent bridge spanning the Sabi River, a gift to the Public of Southern Rhodesia from the funds of the Beit Trust has, at the request of the people of Rhodesia, been named " THE BIRCHENOUGH BRIDGE" in recognition of the services given to the country by Sir Henry Birchenough, Bart., G.C.M.G., the Chairman of the Beit Railway Trust and President of the British South Africa Company. Portraits in bronze of Sir Henry Birchenough, by Mr. Sydney Kendrick, and inscription panels in bronze have been inserted in the east and west abutments.

The bridge was built to give the people residing in the eastern districts access across the Sabi River to the central districts of Southern Rhodesia. In addition, the bridge will serve to open up to visitors from the Union of South Africa and elsewhere one of the most beautiful mountain districts in the territory.

The bridge crosses the Sabi River with a single arch which rises to 280 feet above the river, and is 1,080 feet in length, a span which is exceeded by only two other arch spans:—-the great bridge crossing Sydney Harbour, and the Bayonne Bridge over the Kill van Kull Creek, south of New York.

The Birchenough Bridge was designed by Mr. Ralph Freeman, consulting engineer to the Beit Trust, who also designed the Sydney Harbour Bridge and the Beit Bridge over the Limpopo River.

The bridge is the first long-span bridge to be constructed in the British Empire with modern high tensile steel. With trifling exception, the whole structure is made of Dorman Long & Company's " Chromador" steel—a material possessing a strength 50 per cent, greater than that of the mild steel generally used for bridgework and 20 per cent, stronger than the silicon steel used for Sydney Bridge. The use of this material made it possible to construct the bridge at a moderate cost as a single span. This avoided the necessity for making piers in the river bed which was found to be of a shifting and treacherous character. Even if the river bed had been normally stable, the type of bridge adopted, which was selected by the Trustees after full consideration of possible alternatives, was found to be the least costly.

The roadway has a width of 18 feet and is designed for heavy-type Colonial loading. Footways are formed on either side of the road so as to allow for the uninterrupted passage of two lines of traffic.

The total weight of steel is 1,500 tons and it is noteworthy that this is the same weight as that of the Victoria Falls Bridge designed originally for two lines of light railway traffic, bat of less than half the span of the Birchenough Bridge.

In the combination which the design provides of an exceptional span with light weight and small capital outlay, the arch span is unique in bridge construction.

The bridge was erected by the same process as that used for the Victoria Falls Arch and subsequently for the Sydney arch—by building out the arch in two halves as cantilevers, anchored back to the rock shores by wire ropes. The anchorage ropes used were the actual ropes used for the Sydney Harbour Bridge and are now incorporated in the Birchenough Bridge as the suspenders of the roadway.

Material was delivered to the west bank of the river by road and the rapid and completely successful transport of the heavy and cumbrous pieces of material under conditions of exceptional difficulty, was an achievement for which great credit is due to the Rhodesia Railways Road Transport organisation and to the Roads Department of the Government of Southern Rhodesia. The steelwork for the east side was carried across the river by a cableway.

Foundations were commenced in April 1934 and were ready for steelwork in November. The arch span was completed on June 17th, 1935, and the concrete roadway was practically complete at the end of September, 1935.

The only work then remaining was unimportant auxiliary construction and painting. The whole of the works were finished so as to enable the bridge to be opened to traffic on December 20th, 1935, the time occupied by the entire construction being 20 months.

The contractors for the supply of steel, manufacture of steelwork, and erection, were Dorman Long & Company, Limited, of Middlesbrough, England, whose previous experience, as the builders of the Sydney Harbour Bridge, and the arch bridge, of 530 feet span over the Tyne, Newcastle, was of great value.

Bridge Site: Sabi River before work was commenced.
April 1934

East Bank: Excavation work started on the skewback foundations.
May 1934