Colenso Bridge
Bridge over the Tugela river.
1877 Bridge built by Patent Shaft and Axletree Co
Destroyed in the Boer War
1900 An article in Engineering, 26 January[1] headed 'The Frere and Tugela Bridges' featured bridges which had been destroyed in the Boer War.
"The contract for the new bridges to replace the wrecked structures at Frere and Colenso was entrusted to the Patent Shaft and Axletree Company, Limited; of the Old Park Works, Wednesbury. The order was given on December 21 last, and in sixteen working days the first span was completed, whilst the second span was completed by January 18. A third span was ready this week, and the last span will, the contractors state, be completed by the end of February. Each span measures 105ft. over all, is 16 ft. wide, and 16 ft. in extreme depth. These figures fail, however to do justice to the contractors, for each span is of the extraordinary weight of 105 tons. The reasons for this excessive weight will appear clearly on reference to our photograph, showing the completed structure as it stood in the builders' yard. Had more time for the preparation and discussion of more modern designs been possible, Mr. M. W. Carr, the consulting engineer to the Natal Government, informs us that he could have obtained a bridge at least equally strong, weighing not more than 45 tons per span. The possible saving was thus enormous, particularly in view of the fact that the whole material has to he transported a distance of 7000 miles. The matter was, however, urgent, and, to avoid possible delay, Mr. Carr reluctantly decided to make use of the designs shown, which were, we are told, prepared by a well-known firm of consulting engineers in Westminster two or three years ago, and were immediately available. As will be seen, the bridge is of what we may perhaps call an early Victorian type, and the lack of economy in the design is obvious. The shallow depth of girder necessitating the curved braces between the top booms, the small panel length, there being no less than 14 panels to a span of 105 ft., which almost doubles the weight of the floor and web members, all point to the disadvantages of the usual English methods of bridge design, in which the full details of a structure are commonly worked out in the office of a consulting engineer, who very frequently has been too busy with general engineering work to keep up to date in the science of constructional iron work. Of course, some of these engineers are, like Sir Benjamin Baker, for instance, specialists in bridge design, and to them our remarks do not apply; but others, as our engraving shows, have quite failed to keep pace with modern advances in the theory of structures. In some other countries nine bridges out of ten are built and designed by the one firm, a consulting engineer only being called in when the work is of unusual magnitude or difficulty. As a consequence, each firm of contractors keeps a highly qualified staff whose business is to prepare the competitive designs submitted to railway engineers and others requiring bridges. Each firm has, therefore, its own standard details, which, being repeated in structure after structure, have an immense amount of care expended on them in the first instance, to insure that they shall not only be thoroughly efficient, but shall also be capable of economical production. English bridgebuilderss on the other hand, are liable to have to provide an entirely different set of details for every new contract, and it is thus impossible for them to lay out their plant with a special reference to the production of any one type. The rolling load for which the bridge was designed is, we understand, 1½ tons per foot. Contrary to what has been stated in certain press organs, it is intended for rail traffic only, and has consequently an open floor, though a light gangway intended for the use of the permanent-way men will be added on each side of the rails. For much of the information above given we are indebted to Mr. Carr, who also supplied us with the photographs representing the original Tugela Bridge, the wreckage at Frere, and the temporary bridge erected by the military engineers."
The replacement girders for the Frere and Colenso bridges were also covered by The Engineer in 1900 [2], From which the following extracts have been transcribed:-
This firm [Patent Shaft and Axletree Co] undertook to deliver the first shipment of one span in six weeks from the date of the order. The order was given on the 21st of December last, at a most inconvenient time, seeing how near it was to the Christmas holidays. The first span was, as a fact, finished last Saturday, the 13th inst., and deducting Christmas and Boxing day, and three Sundays, the work had actually occupied nineteen working days.
…. Illustrations …..It will be observed that it had been entirely erected in the company's works. This, of course, represents time, several days at all events, and, as a comparison, we may mention that not only was this not done by the makers of the Atbara Bridge, but that the edges of the plates composing this bridge were not planed or finished. The planing involved in the span of the Tugela Bridge was no less than 7500ft. run. Moreover, this span, as will be the case with the whole of both bridges, was also painted with Docker’s "special " Hermator oxide paint.
There are to be in all seven spans of 105ft. long each. Five of the spans are for the bridge at Colenso, the remaining two are for the river at Frere. Each span will weigh some 105 tons, exclusive of rivets, and there are 60,000 rivet holes to be drilled in each span. Siemens-Martin steel, manufactured at the company's works, is used throughout. …….
'The order was received at 9 a.m. on December 21st. By 5 p.m. the same day a considerable quantity of material - some 100 tons - had been rolled at the company's works, tested and approved by the Natal Government engineer, and some of the plates were actually on the planing machines. About 100 men and boys have been continuously at work on the order, but though these have worked late, there has practically been no night work. The quickness with which the first span was completed, and the remainder of the work taken in hand - for two spans are now completed and work begun on the third, fourth, and fifth spans, while the whole of the material for the seven spans is rolled, cut to size, tested, and approved - is the result, so we are informed by the company's officials, of the manner in which the workmen have responded to the call made upon them. Every man and boy, from the manager of the bridges department, Mr Knowles, downwards, having done everything in his power to further the work. Nothing beyond ingots was in stock when the order was received. The firm had made the original Colenso and Frere bridges in 1877, but the new bridges are, as already mentioned, of different pattern. Hence new templates had to be made, and the men in the template department voluntarily worked right through Christmas. The company is certainly to be congratulated on the promptitude with which the work has, been completed, and on having such a staff of workpeople as to render this possible.'
Pictures of the Colenso bridge destroyed in the Boer War with Fort Wylie in the background. See here and here and from the other side of the river here.
and a picture of the temporary structures erected during rebuilding the Colenso Bridge, presumably a view taken from Fort Wylie: c.1901 photo.
From The Engineer, 30 March 1900[3]
'As a supplement to to-day's issue we give reproductions from
two most interesting photographs which have been courteously
handed to us by Mr. M. W. Carr, consulting engineer to the
Natal Government. These photographs show the bridge over the
Tugela River at Colenso, which our readers will remember was
blown up by the Boers. An examination of these photographs will
show the wanton damage caused to this bridge. All military
objects would have been achieved had only one span been destroyed,
but not content to simply do this, the Boers have wrecked every
span , and have completely demolished one of the piers. The explosive used was probably placed on the top and bottom of each girder at some distance away from the piers, and the result was that the girders collapsed and slid off the masonry piers. In the case of the wrecked pier, however, it would seem that undermining bad been resorted to.
The destroyed bridge, an engraving of which as it appeared before
being destroyed is shown above, formed part of the Maritzburg-Ladysmith extension of the railway which was commenced in 1882 under the superintendence of Mr. Carr, when chief resident engineer to the Natal Government. The bridge was completed in the year
1885. The contractors, for this piece of railway were James Perry and Co., and the iron structure of the bridge was supplied by Head, Wrightson and Co. It consisted of five spans, each of 100ft. - the girders being 105ft. long - carried on masonry piers. These
piers were built of a fine hard freestone quarried in a neighbouring
locality. Great care was exercised in their erection and indeed
in the construction of the whole bridge - which was considered quite
the show bridge of the colony. The excavation for the piers was
taken down to the solid rock, which at this place comes near the
surface, and the foundation stones were set on the rock in one to one cement and sand. In design the piers are very strong, and necessarily so, as frequently they have to withstand furious floods which come down in a remarkably short space of time. Colenso is so near
the foothills of the Drackensburg that the stream, which one evening
may have but little water in it, may in the morning following have
risen 20ft., and be a raging torrent. In the views we reproduce, it
would seem as though too large a bridge had been provided at this
point , but this is by no means the case , as the water stretches from
abutment to abutment in times of high flood. This same remark
applies to all the bridges in Natal. Streams that in dry weather
one could almost jump across are often traversed by railway bridges
of 100ft. s pan. This great length is quite necessary. In floods the
water level may rise so greatly that it comes but a few feet below
the underside of the girder, and the stream may be much more than
100ft. wide.
In our issues of January 19th and February 6th we gave photographs and drawings of the new spans, which were made by the Patent Shaft and Axletree Company to take the place of the spans destroyed at Colenso and at Frere. These were ordered by the Natal Government, when these bridges were blown up, and now some of the spans, if not all of them, have arrived at their destinations, and
in the case of the Colenso Bridge , at all events, they will have
arrived before they can be used. As a matter of fact, the Natal
authorities, as soon as ever hostilities began, set to work to make
provision for the temporary repair of such bridges as might be
blown up. It was recognised that such an eventuality was more
than a probability. The locality does not produce timber of the
requisite character for making temporary bridges, and all of this
had to be imported. So quickly was the work organised, however,
that weeks before our forces finally occupied Colenso, the necessary timbers for the temporary repair of the bridges were obtained, worked to size and shape, and loaded ready on trucks. In the original of one of the photographs which we reproduce there is
very faintly shown a train of trucks with the timbers made ready
for the necessary repairs. The temporary bridge is alongside the
wrecked bridge, but at a lower level, of course, the rail being diverted
on to the new structure. The timbers are made up into trestles,
which are placed on the bed of the stream and as securely fastened
as circumstances require, being further secured by weights piled up
on the cross beams at the bottom. The temporary bridge at Frere
has long since been completed, and that at Colenso was reported
complete recently, enabling through traffic between Durban, Ladysmith, and Elandslaagte to be resumed. All necessary repairs and reconstruction of the way and works have been carried out in the most expeditious manner by the engineering department of the railway, under the supervision of Mr. J. W. Shores, M. Inst. C.E., engineer-in-chief.'
1900 'A BRIDGE-BUILDING FEAT.
At a meeting of the shareholders of the Patent Shaft and Axletree Company in Birmingham, the chairman told the story of tho building of the bridge to replace the one destroyed by the Boers over the Tugela. About two years ago, he said, the managers of the Egyptian Railways placed an order in America for the Atbara Bridge, and the Americans made great capital out it. In common with other bridgebuilders in this country, the Patent Shaft were very much disappointed and annoyed at losing this order. They considered they were not treated fairly, inasmuch if they had had an opportunity of taking the order on the same conditions as it was placed in America they would have done the work quite quickly. The Tugela Bridge was more than double the weight of the Atbara Bridge, and was made to the designs of an eminent Westminster engineer. They received the order on December 21st, and although the Christmas holidays intervened they completed the whole of the seven spans on February 17, or one month before the specified time.'[4]
Note: The newspaper article above refers to the works fabrication time of the replacement girders. It will be noted that although all the rivet holes have been made, a proportion of the rivets would be fitted on site. In contrast the Atbara bridge was of the pin-connected truss type, which may have facilitated faster assembly on site.
See Hopetown Old Wagon Bridge (S. Africa) for another example of quick construction of a bridge span in 1900.
By 1957 a new bridge had been built beside the old one which had been partly demolished: see here