Queen Alexandra Bridge
Sunderland
The Queen Alexandra Bridge is a road traffic, pedestrian and (former) rail bridge spanning the River Wear in North East England, linking the Deptford and Southwick areas of Sunderland. The steel truss bridge was designed by Charles A. Harrison (a nephew of Robert Stephenson's assistant). It was built by Sir William Arrol between 1907 and 1909 and officially opened by The Earl of Durham, on behalf of Queen Alexandra on June 10, 1909.
In 1899 the North Eastern Railway and the Sunderland Corporation agreed to build the bridge to improve communications across the river and to connect the coalfields of Annfield Plain and Washington with Sunderland's south docks. Before the completion of the bridge, road traffic crossing the river had to use one of two ferries which crossed below near to where the bridge is today. As the bridge was due to be built near to the successful shipyards of the Wear, a clause in the North Eastern Railway Act 1900 required that only one arch span be built over the river to give a clearance of 85 feet above high water level.
The approaches to the bridge were completed in 1907 by the Mitchell Brothers of Glasgow and the bridge proper comprises three 200 foot land spans (weighing 950 tons of steel each) and a 300 foot river span (weighing 2,600 tons of steel) and was the heaviest bridge in the United Kingdom at the time. The bridge was built from each side of the river and the two halves came together at noon on 15 October 1908. In all, a total of 8,500 tons of steel, 4,500 tons of granite, 60,000 tons of red sandstone from Dumfries, and 350,000 bricks were used and the cost of completion was £450,000. The bridge also housed gas and water mains and in later years, high voltage electricity cables and a pumped rising-main for sewage.
About six million tons of coal passed over the upper-deck annually for export but the trade rapidly declined at the end of the 1910s. For the last few years only one train per day passed over the bridge. The last goods train ran over in 1921, but the lower-deck continues as a valuable road link. In the Second World War, the upper-deck was used as a searchlight and anti-aircraft platform. The railway and decking at each end of the bridge were finally removed near to the end of the 20th century. A large free standing brick and stone viaduct fragment remains on the north side of the Bridge.
From 21 March 2005, the bridge had been restricted to southbound traffic whilst repainting and repair work was carried out on the 96 year-old structure, which was due to take almost a year to complete. It reopened for both lanes of traffic on 12 October 2006, having been partly closed for 18 months and costing £6.3m in repairs
Selection of Geograph photographs here, here and here.
Construction
The following extracts are taken from 'The Engineer', 4 June 1909 and 11 June 1909.
The girders were built out, on the cantilever principle, until a junction was made in the middle, the overhang loads being taken by temporary steel ties attached to steel towers erected over the main piers, with back ties attached to the extreme ends of the smaller spans, and the weight of each shore span being utilised for anchorage. On the completion of the land spans, the main bearings of the river span were placed in position on the river piers, and upon these the first portions of the lower booms of the main girders were laid.
'During the erection of the main girders, temporary steel towers, 70ft. high, were erected immediately over the end vertical posts of the main girders. The tops of these towers were connected by heavy plate ties to gusset plates at the further ends of the adJoining land spans, and from the gussets at the top of the towers other ties were carried to gusset plates riveted to the bottom booms of the end of the overhanging portion of the river spans. These tie were left with an uncovered gap of 18in. about the centre of their length.
'When the towers and first set of supporting ties had been erected, the top boom ties were released by means of hydraulic jacks, with a hydraulic stressing gear, inserted in the gap referred to. Pressure was admitted to the jacks which drew the upper and lower ends of the temporary ties at the gap towards each other; the overhanging portion of the river span was thus raised and the ties at the top booms released, A force of about 200 tons was exerted on each pair of ties to draw the two ends together. This force was calculated to take the whole weight of the overhanging portion on to the ties and to relieve the temporary ties at the end posts, which had previously borne the whole of the stress. When the calculated load on the jacks was sufficient to release the stress on the end post ties, the rams were locked and the end post ties were cut through and the continuity between the land and river span severed, except at the butting faces of the bottom booms. Previous to stressing the inclined ties with the 200 tons the end post ties were carrying a load of 460 tons. On cutting out the end-post ties the tops of the end-posts over the river pier came together only 0.04in., a testimony to the efficiency with which the operation of relieving the ties of stress had been carried out. It was then necessary to raise the overhanging portion of the span an additional 3in., so as to make due allowance for the subsequent straining of the supporting ties and consequent future deflections of the girders. This lift accomplished, the upper and lower portions of the ties were connected by their joint covers at the gap, the stressing gear was removed, and the tie took the load direct throughout. [A series of views showing the tie intact, half bored through, and removed, is given on page 603.] The erection of the span again proceeded, and the main girders were built out for another 50ft. in a similar manner. Additional gusset plates were riveted to the bottom booms near the ends, and a second set of ties were built, a gap being left in these as in the first sets of ties, whilst the same stressing gear was used to pull the ends together. A force of about 385 tons was applied to each main girder, and the previous inclined ties were relieved of all stress, and the entire weight of the overhanging portion carried on the new ties. The third stage in the erection was now reached, and the main girders were built out to the centre of the span. The final or closing length of about 8ft. was retained in the bridge yard in a partially finished condition. The material for this length was a few inches longer than the estimated requirements, and the rivet holes had been drilled only as far as could be done with any degree of certainty. When all was ready for the erection of the closing lengths, the requisite measurements were taken across the gap by means of wooden rods. These rods were then sent to the Dalmarnock works, Glasgow, where the various plates and angles forming the closing lengths were marked, cut, and finished off. The material was then sent forward, and put in place, but joined at one end only, the other being left free. This arrangement allowed - previous to the final joining up - for the expansion and contraction as well as the lateral and vertical movements which were continually taking place in the structure. It was recognised that the question of temperature played a not unimportant part in the successful closing of the ends, and the various parts had been designed with great precision so as to ensure an accurate junction, with a prevailing temperature of 60 deg. Fah. The day chosen - October 15th, 1908 - proved exceptionally favourable, as both the temperature and general conditions were similar to those when the measurements for the closing lengths were taken. At 12 noon the halves of the main girder came together, and as the day was dull there was practically no lateral or vertical movement. A few drifts at each of the four booms were rapidly driven home, and immediately afterwards bolting-up commenced at all points. The holes so nearly coincided, and so rapidly did the bolting proceed, that the junction was practically completed within thirty minutes of being commenced!
'In the event of unfavourable climatic conditions
having been experienced, provision had been made for
adjusting the two ends vertically, horizontally, or laterally,
The jacks, previously alluded to, were placed in position at
the ends of the 200ft. spans, ready to supply the power for
adjusting vertically, while special jacks were so secured to
the floor of the second 200ft. approach span on the Southwick side as to have enabled the north half of the structure
to have been moved longitudinally. Lateral adjustment
was provided for by a series of diagonal bracing, joining
the opposite halves of the centre span at each side of the
closing length. When the main girders were joined in
the centre, the expansion bearings at one end of the 330ft.
span, which had previously been locked up, were released.
All expansion or contraction of the structure had been
permitted to take place at the overhanging ends and at
the landward ends of the land spans, where provision had
been made for movement. After the expansion bearings
were relieved, the whole tructure, consisting of the
temporarily-joined three spans, was fixed at one point
only and free to move longitudinally at all the other points
o£ support. The completion of the steel work of the
contre span permitted the stress on the temporary ties, due to the load, to be released by raising the landward
ends of the land epans. Hydraulic jacks, placed underneath the main girders at these ends, were used for
the purpose. The spans were raised about 10in., which
proved sufficient to make the river span - which deflected 2 3/8in.- self-supporting and to slacken off the
temporary ties. A joint in each back supporting tie
was then unbolted and the main girders of the land spans
were lowered to their proper level. The temporary towers,
which were erected on the end vertical posts of the main
girders, were 70ft. high, and were built at the site in
three sections and lifted into place by cranes. Each pair
was braced together diagonally so as to resist the overturning effect of the wind. The base of each tower was
9ft. long by 4ft. 6in. wide, and was bolted round the edges
to the top of the end post. During the operations of
initially stressing the supporting ties, and also during the
progress of erection, various movements occurred at the
top and base of each tower. To avoid severe secondary
bending stresses in the tower, due to these movements,
the bolts in the front and back edges of the base were
slackened, leaving the tower free to pivot longitudinally
to a slight extent on the top of the end post. Before
the closing length of the back ties was inserted the
towers were pulled back 4 1/2in. at the top so as to allow
for the elongation of the supporting ties due their unusual
length, but when the maximum loads were on the temporary towers they were practically in a straight line
with the end posts of the main girders. The supporting
ties were formed of groups of flat plates, 24in. and 30in.
wide, and were supJ>orted at several points by timber
trestles. All the joints in the ties were formed by turned
and fitted bolts , of which some 20,000, generally
1 1/16in. in diameter, were used. Before deciding to utilise
bolts instead of rivets several tests as to their relative shearing strength were carried out, with the
result that steel bolts 1 1/16in. in diameter, turned and
fitted into drilled boles, were found to be quite equal to
lin. diameter steel rivets hydraulically driven into
1 1/16in. drilled boles, whilst for temporary work bolted
connections were much more convenient than riveted
connections.
'The effect of the weather conditions upon the large exposed surface of the supporting ties was readily apparent in the rise and fall of the overhanging portion of the span. During the warm weather of September last the point of the span moved transversely a maximum distance of l 3/8in. Many of the members of the main girders during erection required strengthening and stiffening on account of the erection stresses. Several of the main diagonal ties, formed of flat plates, were temporarily converted into compression members by the addition of angles and lattice bracing. The bottom booms, particularly at the ends, were also strengthened. As some illustration of the forces dealt wtth, it may be cited that the stresses in the back tie of each half span amounted to about 1200 tons and in the front ties to about 1400 tons, and the maximum weight suspended from the temporary ties before the closing lengths were fixed was 2400 tons. In the tests carried out by the North-Eastern Hailway Company .....
'As previously remarked , the works have been designed by Mr. Charles A. Harrison, D.Sc., Newcastle-upon-Tyne, the chief engineer of the North Eastern Railway Company, and he has been represented at the site by Messrs. Philip Bulmer and F. C. Buscarlet. From the inception of the works Mr. Andrew S. Biggart, the managing-director of the contracting firm - Sir William Arrol and Co., Limited, of Glasgow - has taken the principal direction, whilst Mr. R. C. Macdonald was in charge of the work in connection with the foundation and erection. The scheme and details of the erection were prepared under the direction of Mr. Adam Hunter, A.M. Inst. C.E., the chief of the technical staff of Sir William Arrol and Co., Limited, and Mr. J. M. Moncrieff, M. Inst. C.E., of Newcastle-upon-Tyne, acted as consulting engineer so far as concerned the queetion of the strength and sufficiency of the temporary and permanent work for the streses the parts had to bear during the various stages of the erection. ....'
This photograph of the bridge in an advanced stage of construction clearly shows the tie-back structure supporting the cantilevered girder sections.
See here[1] for an interesting I.C.E. Discussion Paper on the discussion of this bridge (and also the new Clyde Bridge). In the Paper Dr Harrison asks and answers the question of why, if the centre span had to be built by the cantilever method, had the bridge not been designed as a cantilever bridge at the outset? The answer was that only after the designed had been finalised and approved by the Wear Commissioners and the Sunderland Corporation, was it revealed that the contractors would not be allowed to obstruct the waterway.
Dr Harrison credits Messrs Arrol with the decision to use the cantilever construction method.
J. M. Moncrieff modestly stated that he 'had some slight connection with the Wear bridge', before going on to reveal interesting insights. He noted that although the calcualtion of the ordinary direct stresses was straightforward, if lengthy and tedious, the stresses and strains during the erection process were a different matter. He also focused on the critical importance of minimising friction at the 'heel-blocks' during erection. One major concern had been the use of fitted bolts in many holes, rather than hot riveting. It was he who had insisted on Arrol carrying out comparative tests.
Mr C. R. S. Kirkpatrick had been one of the unsuccessful tenderers, and he was critical of a number of cost-saving measures, including the fact that only one air-locked access shaft rather than two had been used.
J. M. Moncrieff and Adam Hunter both referred to concerns about unsatisfactory sharing of shearing stresses in riveted joints between the girder end posts and the temporary ties during the erection process. Hunter had investigated the problem using rubber models, and as a result it was decided to rivet about half of the holes, building out part of the girders, then riveting the remainder of the holes.
See Also
Sources of Information
- The Engineer 1909/06/04, pp.588-9
- The Engineer 1909/06/11, pp.603-4