Didžiosios Britanijos tiltai

MENAI SUSPENSION BRIDGE (FROM A

CORRESPONDENT)

Menai Strait from Anglesey Column

“This stupendous structure was opened for general intercourse on Monday, the 30th of .January, at half past one in the morning. As the season was considered unfavourable for a public celebration1 the Commissioners determined that the opening should be quite private; and, in pursuance of this resolution, a meeting was held the previous evening at Bangor Ferry, to make the final arrangements. Mr. W. A. Provis, the Resident Engineer was then dispatched tto meet the London down mail, and take charge of it across the Bridge. Having mounted the box with David Hughes the coachman, and Reid the guard, the Mail proceeded, and on its way to the bridge took up Mr. Akers, the Mail Coach Superintendant, Mr. Hazeldine, the contractor for the ironwork, Mr. J. Provis, the superintendant for proving and examining it, Mr. Rhodes, who has had charge of erecting the iron and timber work, Messrs. W. and J. Wilson, ssons of the contractor for masonary, Mr. Esplen, an overseer, and as many more as could be crammed in, or find a place to hang by. Thus loaded, amidst the blaze of lamps, the cheers of those assembled, and the rroaring of a heavy gale of wind, the dates were thrown open, and the Mail passed triumphantly across.

About 9 o’clock, that excellent and indefatigable Commissioner Sir Henry Parnell, and the Chief Engineer, Mr Telford (whose works are his best Eulogium) passed over in the carriage of the latter. Throughout the remainder of the day, the number of carriages, horses1 and persons which passed over was immense; the bridge was literally crowded, and tickets could not be issued fast enough for the demand. The evening was spent by the workmen with much fun and feasting, and the sons of the Sister Kingdoms seemed to have but one feeling, in wishing “Success to the Bridge”, and promoting the general hilarity.”

Menai Strait Bridges

For ccenturies, travel to Anglesey from the mainland was often hazardous. Ferries traversed the Menai Strait at various places, but the currents are tricky and numerous boats capsized or ran aground, often with loss of life.

One of the most tragic occurred in 1785 when a boat carrying 55 people became stranded on a sandbar in the middle of the southern end of the strait. Attempts to refloat the boat left it swamped. The alarm was raised and rescuers set off from CCaernarfon. But, the combination of high winds, nightfall and the fear of also running aground meant that the rescuers could not approach the sandbar. Night fell, the tide rose and those stranded on the sandbar were swept away. Only one survived.

Menai Bridge

White Knight says to Alice,

‘I heard him then, for I had just completed my design.

To keep the Menal Bridge from rust.

By boiling it in wine.’

Lewis Carrol, Through the Looking Glass

Menai Bridge

Traffic across the strait and Anglesey increased in the early 19th century after the Act of Union of 1800, when Ireland joined the United Kingdom. Travellers to the ferry port of Holyhead, where ships left for Ireland, had to make the dangerous crossing after a long and arduous journey from London. Soon plans were drawn up by Thomas Telford for ambitious improvements to the route from London to Holyhead, including a bridge over the Menai.

One of the design requirements for the bridge was that it needed to have 100 feet of clear space under the main span, to allow for the passage of the tall sailing ships that plied the strait. This was done by designing a suspension bridge, with sixteen massive chains holding up a 579 foot length oof road surface between the two towers. Although small suspension bridges had been built before, none approached the scale that Telford proposed for this one.

Despite much opposition from the ferry owners and tradesmen in the ports, construction of the bridge started in 1819. The stone used for the arches and piers was limestone quarried from Penmon Quarries at the north end of the strait, then carried down by boat. The ironwork came from Hazeldean’s foundry near Shrewsbury. To prevent the iron from rusting between production and use on the bridge, the iron was immersed, not in boiling wine as the White Knight suggested above, but in warm linseed oil.

The stonework was finished in 1824; then began the monumental task of raising the chains that would hold up the central span. Tunnels were driven into solid rock on either shore to anchor the chains. Then the first section of the chain was secured oil the Caernarvonshire side, drawn up to the top of the eastern tower and left to hang down to the water level. Another chain was drawn up to the top of the tower on the Anglesey side. The central section of chain, weighing 23.5 tons, was then loaded oonto a raft, carefully manoeuvred into position between the towers and connected to the dangling chain. While a fife and drum band played to encourage the workers, 150 men used block and tackle to draw the chain up to the top of the Anglesey tower to complete the span. The large crowd that had gathered to watch cheered wildly as the connection was made.

The remaining fifteen chains were raised in a similar manner over the next ten weeks. Rods were then hung from the chains and bolted to iron bars that were used as the base for the wooden road surface. The bridge was opened on 30 January 1826 to great fanfare. Its completion, along with other improvements to the road by Telford, reduced travel time from London to Holyhead from 36 hours to 27 (today it takes 5.5 hours).

The bridge has been modified and reconstructed many times over the years. The road surface was damaged in severe winds in 1839 and needed repair. The wooden deck was replaced with a steel one in 1893. With the coming of modern vehicles the previous weight limit of 4.5 tons per vehicle became an impediment. Overweight vehicles would have to

carry their loads over in two or more trips. In fact, even bus conductors would regularly have to ask some passengers to walk across. So, between 1938 and 1940 the old iron chains were replaced with new steel ones, all while traffic continued to cross. In the autumn of 1999 the bridge was closed for several weeks to completely replace the road surface and strengthen the bridge.

Britannia Bridge

Britannia Bridge from Church Island

The completion of the Menai Bridge was a boon iin easing the journey to the island, particularly for travel to Ireland. However, the rapid rise of rail travel later in the 19th century meant that there was soon a need for trains to cross the Strait. When plans were first being made to build a railway to Holyhead it was proposed that the carriages be taken over the Menai Bridge; the carriages would be uncoupled from the locomotive at one end, then drawn across one by one, using horses, tto a waiting locomotive at the other end.

This idea was abandoned and plans were drawn up for a new bridge by Robert Stephenson, son of the locomotive pioneer George Stephenson. He faced the challenge of building a bridge rigid and sstrong enough to carry a heavy train of many carriages. This was done by making the bridge out of two long iron tubes, rectangular in shape, through which the trains would travel.

When first conceived, the tubular bridge was to have been suspended from cables strung through the openings at the tops of the towers. However, after engineering calculations and tests of the finished tubes it was decided that they were strong enough by themselves to carry the trains.

Like the Menai Bridge, the stonework of the Britannia Bridge was constructed of limestone from Penmon, although sandstone from various places was used internally. The tubes themselves were constructed on the banks of the Strait.

Stephenson faced a much greater challenge in raising tthe 1,500 ton finished tubes than had Telford with his much lighter chains. He too would float the tube into position. However, the process didn’t go as smoothly with the first tube as with the Menai Bridge chains and the giant tube came close to being swept out to sea. Fortune prevailed and it did finally end up in place. Then, very slowly, using hydraulic f5umps, the tube was raised into position. Stonework was built up under the ends of tthe tube as it was lifted; this was to support it if the lifting equipment failed. This was fortunate because one pump did indeed fail, but the tube only fell nine inches.

Menai Bridge

With the tubes in place the final touches were added. These are the four magnificent limestone lions that guard the entrances to the bridge. They were carved by John Thomas, who had also done stone carving for the Houses of Parliament and Buckingharn Palace in London. The lions are almost 4 metres high and sit on plinths of equal height. The bridge was opened on 5 March 1850.

The present day bridge has a much different appearance than the original. This is because it has been reconstructed after a disastrous fire in 1970. A group of teenagers looking for bats in the dark tubes accidentally dropped the burning paper they were using as a torch. This eventually started a ferocious fire through the whole tubular structure that caused so much damage to the tubes that they were in danger of falling into the strait.

As assessments were being made as to how to repair the bridge the local County Surveyor came up with the clever idea of making two bridges oout of one. For many years there had been discussions of building a third bridge~

Britannia Bridge across the strait to ease the traffic coiThestion after reconstruction on the Menai Bridge. It was proposed that the

Britannia Bridge be rebuilt as a two level bridge carrying both trains and road traffic.

Rather than being a tubular bridge the new span is now supported by arches. A single railway track carries the trains to and from Holyhead. On top of this is a roadway carrying traffic on the A55 Expressway. The traffic on the bridge is monitored by a video camera that is now connected to the

Internet.

And today, the lions that once had pride of place at the entrance to the tubular bridge now sit forlornly below the road surface as thousands of vehicles thunder past.

Update – The closure of the Menai Bridge

for repairs in 1999 caused severe traffic problems on the Britannia Bridge. This, plus the increase in traffic that inevitably will be caused by the building of a new dual-carriageway across Anglesey, means that there have been new calls locally for a third crossing to be built across the Strait. One favourite option is to build a new deck on top of tthe Britannia Bridge, so that it has two levels for cars. Whether this will happen remains to be seen.

Update 2, Oct. 2001 – The latest DIan being discussed to ease traffic is to build a tunnel underneath the strait, with one entrance near Gaerwen and the other beyond Bangor. It has been estimated that this would cost at least as much as the whole dual carriageway across Anglesey. It also m~y not be feasible because the strait is formed from a geological faui’rwhich is still occasionally active. An alternative is to convert the Britannia Bridge from two to three lanes, with the traffic direction of the centre lane changing at different times of the day.

Travelling from England to Ireland

At the commencement of the eighteenth century a voyage from England to Ireland was not lightly undertaken. The vile condition of the Welsh roads compelled travellers to make either Bristol or Liverpool the port from which to sail. The ships of those days were far from being commodious or comfortable, and when, as often happened, contrary winds and storms protracted the voyage, the passengers fared badly.

Now, the map shows very clearly that Holyhead, at the northwest corner of the

island of Anglesey, is much nearer the Irish coast than

is either Liverpool or Bristol, and this geographical fact presently made it the fashion to brave the joltingsof Welsh mountain tracks in preference to the tossings of seventy miles of Irish Sea. It is true that the Holyhead route included the crossing of the Menai Straits, which, in certain states of tide and weather, was a very unpleasant business; and when these had been negotiated, there remained the

roads of Anglesey, which wwere, if possible, worse than those of

Wales. To the credit side of the Holyhead route could be placed the

fact that Anglesey and Liverpool were equidistant from many of the

large midland and southern towns.

Telford’s Road to Holyhead

In 1810 the great engineer, Mr. Thomas Telford, was engaged to deal with the roads between Shrewsbury and Holyhead, via Llangollen, Bettws-y-Coed, and Bangor. He blasted rocks, built parapets, and formed embankments, until, in the place of rough, steep mountain tracks and tenacious quagmires, there wwas a wide, safe, and splendidly graded road, which even at this day is one of the best in the British Isles.

He decides to bridge the Menal Straits

But there still existed the irksome passage of the straits. Until these were bbridged the road would be incomplete. Mr. Telford under took to span the gap. He submitted two plans for arched bridges, one of which showed a 500-foot cast-iron arch, to be supported during construction on centres suspended from large frames rising on the two shores. Both these plans were ruled out, however, on the ground that they would interfere seriously with the navigation of the straits; so the engineer decided on a suspension bridge which should clear the water by 100 feet or more-sufficient to permit the passage of a tall ship. The site chosen was at a point where the shore on either side rises steeply, and where the straits are about 800 feet wide at high tide. The ddistance between abutments is just short of one-third of a mile. To span this, Telford specified two short embankments, 7 arches of 52 1/2 feet span, and a main suspension span over the channel of 550 feet between the centres of the towers.

The last factor taxed Mr. Telford’s ingenuity severely. Such a span was at the time unprecedented, and the safe accomplishment of the task demanded that a vast amount of preliminary experiment should be devoted to the huge chains fforming the distinguishing feature of the structure.

The Building of the Piers.

An Act empowering the building of the bridge was passed in 1819, and Telford lost no time in getting to work. The foundations of the two main piers, each 153 feet high, were taken in hand first, and while the piers rose the arches of the two approaches rose with them, the chief difficulty being that of providing sufficient stone to keep the army of masons engaged. As the piers would be subjected to the Piers severe lateral strains, their individual stones were bound together by iron clamps, in much the same manner as the components of a lighthouse. Four large cast-iron saddles, running on rollers, to carry the suspension chains, capped each pier. Their easy movements over the rollers provided for the expansion or contraction of the chains as the temperature of the air should vary.

Anchoring the Suspension Chains.

Since the efficiency of a chain depends ultimately on secure attachment, every care was taken to ensure firm anchorages for the chains of this bridge. The method adopted was to drive four parallel tunnels obliquely down into the native rock for a distance of 20 yards or more, and excavate a cchamber across their lower ends. In this chamber were built up massive transverse anchorage frames, resting against the walls of rock separating the tunnels, and therefore immovable unless the rock itself were torn away – a contingency that was practically negligible.

The chains, sixteen in number, were composed of 1/2 inch bars of iron. Thirty-six bars – corresponding to the strands of a wire cable -were grouped together to make a square chain four inches on the side, the components of the chain being wrapped with iron wire. The weight of the portion of the chain between the two suspension piers was over 23 tons; its length, 570 feet.

An Experiment.

The masonry completed, preparations were made for hoisting the chains into position-a process to which Mr. Telford looked forward with the greatest anxiety. In order to obtain exact figures as to the

power required to hoist a chain and give it the correct curvature between the piers, he fastened together, end to end, a number of iron bars totalling five hundred and seventy feet in length. These were laid out in an adjacent valley, and raised at the ends until the centre was clear of the ground and the curve was the same aas that of the suspension chains to be. From the stresses recorded, Telford calculated that a pull of thirty-nine and a half tons would be needed to handle the central span of a chain.

Each chain was divided into three parts – two to reach from the anchorages to the piers, the third to span the channel. One of the land sections – that on the Carnarvon side – was long enough to extend down the seaward side of this pier to water-level; the other reached only to the pier saddle. The rest of the chain was built on a raft 450 feet long and 6 feet wide, ready to be floated to a position between the two piers.

Hoisting the Chains.

On April 14, 1828, the hoisting of the first of the chains took place under the eyes of thousands of people who gathered from far and near to witness the subjection of the straits. In the afternoon, shortly before high water, the raft bearing the chain was taken in tow by four boats, swung round, and moored across the straits on the line of the bridge. One end was then made fast to a loose end of the Carnarvon section, and

to the other were attached strong ropes leading over the top of the Anglesey pier to two capstans on the shore. At the given signal 150 sturdy labourers threw their weight on the capstan bars. Slowly the chain rose from the raft, and yet more slowly, as less and less weight was water-borne. Presently a great shout arose when the raft, now entirely freed from its load, floated down the tide.

The Junction made.

For another hour the crowd watched the curve oof the made chain grow flatter and flatter, and the word went round that a junction had been made with the Anglesey land section – in fact, that a continuous chain now extended from Anglesey to Wales. This provoked a fresh outburst of cheering, which in turn encouraged some foolhardy workmen to use the chain as an unlicensed bridge and win the perilous honour of being the first to cross the straits by an aerial pathway.

A Foolhardy Feat.

Not that they wwere so daring as a workman on the great cantilever bridge across the Niagara gorge, who, when but a narrow gap separated the two cantilever arms, laid a plank across it, walked deliberately to the middle, and stood on his hhead, kicking his legs about just to show how little he cared for the whirlpool raging two hundred feet below

The Bridge opened.

The remaining fifteen chains were raised in the same manner as the first, and by July 9, 1825, the last was in place. A band ascended to a temporary platform on the centre of the span and played the National Anthem to the crowds which had assembled for the occasion. Then followed the more prosaic work of attaching the roadway of stout planks to the vertical suspension bars of inch-square iron. By the end of the year the structure was complete, and on January 30, 1826, a stage-coach made the passage of the bridge at the head of a ggreat procession of people of all ranks.

Menai SusDension Bridge from the Canarvon side. Menai Susr~ension Bridge from the Anglesey side.

Facts and Figures.

This remarkable bridge has a roadway length of just 1,000 feet, while the suspension chains measure 1,715 feet from anchorage to anchorage. The roadway, 30 feet wide, gives accommodation for two carriage-ways and a footpath. Over 33,000 pieces of iron, weighing 2,187 tons, are incorporated in the structure, the cost ...