History Page

Architect's Description.
Pages from Humber's book 1857.

During the early - middle part of the nineteenth century the rush to exploit the vast coal reserves of the South Wales valleys was well underway.
The development of the railway network in the area played a vital part in this process. But the deep valleys and steep sided hillsides proved a formidable challenge to the railway engineers of the time.

By 1847 it became obvious that a new double track railway line of standard gauge was needed to link the N.A.H. (Newport, Abergavenny and Hereford) in the east, with the T.V.R. (Taff Vale Railway) in the west. Parliament authorized N.A.H. to build this line, which was to be called the T.V.E. (Taff Vale Extension).

This line had to cross the Ebbw and the smaller Kendon valley at Crumlin. It was decided that a stone bridge would be impracticable owing to the strong lateral forces of the wind in such a narrow valley. But the more likely reason for not opting for a masonry structure was because of the enormous cost involved. In August 1852 the Board of the N.A.H. invited tenders for the construction of a wrought iron bridge and by October they had received two. One was a lattice structure submitted by Doyne, who had previously designed on bridge over the river Taff at Treforest and the other by Kennard described as a Warren Bridge.

Charles Liddell the chief engineer with N.A.H. preferred Thomas Kennard's submission and this was accepted by the company and the contract was signed in December the same year, with a stipulated completion date of October 1st 1854.

Kennard’s plan incorporated his own-patented modification of the Warren Truss (a form of bridge span invented by James Warren).  There would be ten Trusses in total, each being 150 feet in length and supported by eight Piers. Six Piers and seven Trusses over the Ebbw valley, two Piers and three Trusses over the Kendon valley, with the hillside between forming a further natural support.  Kennard himself designed the Piers, which were formed by 14 round cast iron columns held in place by diagonal and horizontal wrought iron braces.

Kennard owned the Falkirk ironworks where the iron castings for the Viaduct were produced and shipped to Newport then by canal or railway to Crumlin.  

Most if not all of the wrought iron was made at the nearby town of Blaenavon by the Blaenavon Iron and Coal Company, which his father R. W. Kennard M. P. established.

Kennard had an assembly plant especially built at Crumlin called the "Crumlin Viaduct Works" where the various sections of ironwork were put together.

He also had Crumlin Hall built, where he resided and from where he could view the progress on the Viaduct.

Before work began in the summer of 1853 boreholes were drilled into the valley floor to establish the nature of the sub-terrain. It discovered that there was good foundation consisting of compacted gravel to a depth of some 40 feet. 

The canal, which terminated beyond the Viaduct site had to be shortened somewhat and drained to accommodate the foundations of the first pier. The foundations in the valley floor were constructed of one foot of concrete, 4 inches of Memel planking and 12 feet of solid masonry.

Whereas the piers on the sides of the valley were set onto the levelled ground cut out of the solid rock.

By the following December just seven months later the first pier was raised into place. There was a ceremony to mark this occasion and it is reported that Lady Isabella Fiztmaurice the wife of M.P. and Chairman of the N.A.H. William Fiztmaurice buried an inscribe cup containing coins of the period into the base of the pier, which from then onwards was called the "Isabella" pier.

As reported in the London Illistrated News, December, 1853.

"The ceremony of fixing the first column was performed by Lady Fitzmaurice, on the 8th instant, in the presence of several scientific gentlemen and numerous spectators. Previously to lifting the first girder, it was tested with a weight of 250 tons, and gave great satisfaction to the engineer who inspected it. On the third instant, about half-past three in the afternoon, it reached the position destined for it, from pier to pier on the Pontypool side of the valley. The weight of the girder was twenty-four tons, and it was raised by machinery at the rate of four inches a minute. When the girder was ‘planted’, a loud and hearty cheer burst from the lips of the workmen, who were some of them in the most perilous positions; while one, more courageous than the rest, actually walked across the girder which was about a foot in width and 200 feet from the ground. In the midst of the excitement, Mr HM Kennard, brother of the contractor, ascended a platform and spoke to the men in glowing terms of the dangers to which our troops were exposed in the Crimea, proposing to the men the desirability of contributing something towards the fund, as a sort of commemoration of a memorable day. The proposal was received with deafening acclamations, and a day’s pay was at once cheerfully offered. The work people were afterward regaled by Mr Kennard, who has built a large permanent workshop adjacent to the viaduct".

Extract from the ‘Monmouthshire Merlin' (December 1853)

"In the presence of the directors and the local gentry, her ladyship (Lady Isabella Fitzmaurice) placed inside a stone, a cup containing the coins of that year, a bottle of wine was broken over the pier, and the permanent bolts were placed in position."

In April 1855 after all the piers had been raised into place and the masonry abutments constructed on each end, work began on lifting the trusses. Each truss consisted of four main girder supports, which were lifted separately. During the construction of the piers parallel openings were temporally left forming a groove to facilitate the lifting of these girders by means of pulleys and a steam winch. They were then move sideways and pinned into position. It took a team of twenty men one whole day to raise a single girder, at a rate of 4 inches a minute, another team would then work through the night to install it in position. The lifting tackle was then reposition in readiness for the next lift; this operation alone took two days.

The first girder went up without incident, but one man was killed and another two were seriously injured when the second girder buckled and one end slipped out of the groove as it was being lifted into position, dragging the men with it. This was the only fatal accident in the Viaduct's construction. 

Safety measures were put in place after this accident, including wooden bracing to strengthen the girders during the lift.

The main structural work on seven span section of the Viaduct was completed in August, 1855 and the smaller three span Kendon section by December

Following the completion of the larger section, a procession of workmen led by Mr. Kid, the Viaduct Works manager, made their way to the western end of the main viaduct, where Mr. and Mrs. Thomas Kennard and friends joined them. They then proceeded to cross the Viaduct via a narrow temporary boardwalk.

As reported in the Monmouthshire Merlin, September, 1855.

"The procession having moved forward upon the viaduct, just as the centre had been reached, a number of cannon on the hillside poured forth thunder peals, which reverberated through the valleys; the workmen joined in rounds of cheering for Mr. and Mrs. Kennard and their friends; and again and again discharges of cannon resounded from height to height.

 When the procession reached the Pontypool side of the viaduct (the view from which spot was strikingly picturesque) a Welshman of the neighbourhood ascended a platform and delivered a short and appropriate address in Welsh, congratulating Mr Kennard upon the completion of the majestic viaduct. 

The procession did ascend the hill, singing ‘cheer, boys, cheer!’ Shortly after, two barrels of beer were broached by Mr Lewis Richards, in front of the Navigation Hotel… (and) singing, music and dancing concluded the gratifying proceedings."

It was declared ready for testing in May, 1857 and six locomotives loaded with lead and weighing 380 tons were run onto one of the spans, using both tracks. The resident engineer M. W. Carr startled the onlookers when he daringly climbed over the handrails to minutely examine the works for any movement.

The maximum deflection observed was between one inch and one inch and half. A few days later the inspector Colonel Wynne passed the Viaduct as safe.

Lady Isabella Fitzmaurice eventually opened the Viaduct on Whit Monday 1st of June 1857, amid great celebrations. It was estimated that a crowd of 20,000 people travelled from all parts of the country to witness the event. Locomotives on the Viaduct line and the Western Valley line below were decorated with flags and evergreens. Over the centre of the Viaduct an Arch was constructed of evergreens and flowers with a banner declaring "Long life and prosperity to T. W. Kennard". Two cannon fired volleys throughout the day, which re-echoed from mountainside to mountainside.

The dimensions of the Viaduct were an overall length of 1658 feet; it was 200 feet high at the highest point above the valley floor.

An estimated 1,300 tons of Wrought Iron, 1,250 tons of Cast Iron, 800 cubic yards of Masonry for the Abutments and Foundations and 25,000 cubic feet of timber went into its construction  

The final cost being £62,000.

In the early years after it was opened there was some technical problems caused by metal expansion.  This was particularly bad in the two hot summers of 1859 and 1865, which led to lateral movement of the track.  This problem was finally solved when iron girders and wrought iron sheeting replaced the original wooden decking.

It then remained virtually unchanged until 1928, when because the more modern locomotives were very much heavier than their predecessors, it was decided on grounds of safety to replace the double track with a single one.

The railway line was closed down in 1964 and the last passenger train passed over the Viaduct on the 13th of June that same year.  Demolition work began the following year, but this work was dogged with problems.  Seven different demolition contractors were used in all before "Birds" were successful with the use of a Bailey bridge.  Even while this work was in progress scenes for the film "Arabesque" which starred Sophia Loren and Gregory Peck were being shot on it.

Crumlin Viaduct remained the highest railway viaduct in Great Britain throughout its working life.

Gwyn Briwnant Jones And Denis Dunstone
Have written an excellent book about this line called "The Vale of Neath Line"

Contemporary Detailed description by Mr. Clayton, Architect

"The total height from the bed of the river to the level of the rails is 200 feet - being within 2 feet of the height of the London Monument: the piers, from centre to centre, 150 feet; actual bearing of girder, 148 feet; the total length of the viaduct 600 yards.

There are altogether ten spans or openings; but they are unequally divided by a tongue of land on which there are place masonry and earthworks, about 50 yards in length, making in reality, as far as the iron work is concerned, two separate viaducts.

The larger viaduct has seven spans and six piers; the smaller one three spans and two piers. The piers are formed of clusters of cast iron columns, placed in stages. Each column is 17 feet long by 1 foot in diameter; cast hollow, the thickness of metal varying from 1 inch to seven eighths, diminishing within, the same external diameter and form of column being preserved throughout.

The number of columns in each stage is fourteen and they are arranged on plan, in the longer direction, in four rows of three each, one with standing singly at each end of the piers, which gives it a salient angular outline. The width between columns at the base of the pier measures 13 feet 6 inches in every direction, taken on the square, excepting between the two centre rows, where it measures 6 feet throughout the height. The pier gradually diminishes to the top of the columns below the girders, where the dimension, 13 feet 6 inches, is reduced to 9 feet and at the external angle columns to 2 feet.

The dimensions of the piers at the base are, between the centre of the columns, 60 feet by 37 feet and the upper dimensions 30 feet by 18 feet, giving a diminution of 30 feet in one direction and of 9 feet in the other. To effect this, nearly all the columns are more or less inclined and the two centre are the only upright ones. The four columns at the corners, forming the square of the piers, lean diagonally, 4 feet 6 inches. The six intermediate columns correspond, but lean each in one direction only. The two single outside columns are most inclined, being 11 feet 6 inches out of perpendicular, forming a raking brace. The top of each stage of columns is connected by horizontal cast girders, 1 foot deep, with 5 inch flanges, bolted together. There are also horizontal and vertical wrought iron tie-rods. The former are circular and 2 inches in diameter and the latter flat bars four inches and three quarters. They are tightened with wedges where necessary.

The columns are fitted together with socket joints, a projection of half an inch being left on the top of the cap, which fits into the base of the columns above. These are held together by four ears cast on the top and bottom, which are fixed with bolts and nuts. The joints of the columns are turned fitted together with the greatest nicety to ensure a perfect bearing. The base platter upon which the columns stand vary from 3 feet to 6 feet in height and have a plate 3 feet square, resting on the masonry, into which they are joggled, plugged, bolted and put together with sulphur-joints. The number of stages of columns to the centre piers, it will be perceived, is ten, without base-plates.

The upper stages of the columns are connected together at the top by stronger horizontal girders than those below. They are finished with A-shaped or triangular bearers, placed over each row of columns, below which the girders rest. The foundations for the piers are formed of solid, flat-bedded and jointed masonry; they were generally carried down to the solid rock and vary from ten to three feet in depth. The girders, 150 feet long, are formed of wrought iron, after Kennard's patent. This consists of a stout beam and a bottom-tie below, with a diagonal filling-in, the whole being supported by the top beam on the principle of an inverted truss; the mode of execution, however, differs much. The whole girder is gradually strengthened by an additional thickness of plates towards the centre, given by a close calculation of the forces required to be resisted.

The bearing of the girder by which is sustained, is worthy of particular notice. It is held by the ends of the upper beam only, the lower one dropping in a state of suspension; the weight thus entirely rests on the last pin, which passes through the outside diagonal tie. The top of the angular termination of piers furnished with casting 3 feet 6 inches wide on the upper surface of which is a flat sinking three quarters of an inch deep. Under the ends of the upper bean are placed cast-iron blocks, hollowed out on the upper surface to receive half the diameter of the pin and of sufficient depth to raise the bottom flanges of the beam clear of the sliding groove.

The block has perfect freedom of play backwards and forwards, to suit the expansion and contraction of the girders as affected by the temperature of the atmosphere or the super incumbent weight. For this purpose a space of 9 inches is likewise left clear between the ends of the beams. The ordinary expansion and contraction in summer, between midday and midnight does not exceed a quarter of an inch. The girders have been tested with weight of 250 tons each, which produced a very slight deflection and, were the viaduct loaded with locomotives, this would far exceed any weight that could ever be put upon them.

The struts have also been tested with a crushing weight of 250 tons. The roadway is formed of 6 inch planking, bolted to the beams, the rails laid on strong, longitudinal- formed sleepers. An ornamental cast-iron balustrade is fixed on each side of the roadway.

The whole viaduct is not straight on the plan, the approaches to the larger one being curved, to which the last spans of the viaduct accommodate themselves by a slight inclination southwards at the extremities".

Pages from Humber's book on Iron Bridges, 1857 and supplied by Dr. P.R. Lewis

At the bottom of the page there is reference to plates 37 and 38 with links to each below.
These links are large images so will take longer to download.

Bridges and Girders






Constructed and Erected by Mr. T. W. Kennard.

This magnificent structure, a general view which is given in the frontispiece of this work, was erected for the purpose of carrying the Taff Vale Extension of the Newport, Abergavenny, and Hereford Railway, over the river and valley of the Ebbw near the village of Crumlin in South Wales. From its extensive dimensions, and the boldness of its design this viaduct may well rank with some of the most important engineering wonders of the day, and does much credit to the engineers and the contractor.

Its total length is about 1,800 feet, or rather more than one third of a mile, but it is divided into two distinct parts, by a ridge of hills which run through the centre of the valley, each forming a separate viaduct, the one consisting of seven equal spans of 150 feet, and the other of three of the same dimensions, the greatest height of the roadway above the surface of the water not being less than 200 feet.

As these two viaducts are similar in construction, we shall confine ourselves to describing the more important structure.

The piers are formed of cast iron hollow columns, each 17 long by 1 foot in diameter, the thickness of the metal varying from 1 to 7/8 of and inch, the external diameter being preserved throughout. These columns are arranged in tiers, as shown fig. 1 plate 37. There are fourteen columns in each tier, the distance between each at the base of the pier measures 13 feet 6 inches, in every direction taken on the square, excepting between the centre rows where it measures 6 feet throughout the height, see plan fig 2. The dimensions of the centre pier, taken between the centres of the external column, are at the base, 60 feet by 27, and at the summit 30 feet by 18, giving thus an inclination of 15 feet in one direction, and 4 feet 6 inches in the other. To effect this nearly all the columns are more or less inclined, the two centre ones alone retain their perpendicular position. The four angle columns have an inclination of about 1 foot in 46, and the six intermediate ones a corresponding inclination, but leaning only in one direction, the two single outside columns are the most inclined, viz., about 1 foot in 12, forming raking braces.

The top of the columns in each are connected by horizontal cast iron girders 1 foot deep, with flanges 5 inches wide, there are also horizontal and vertical wrought iron tie rods, the former are round 2 inches in diameter, the latter flat bars, 4 inches by ¾ of an inch; they are both tightened with wedges. The columns are fitted together with socket joints, a projection of ½ being left on the top of the cap, which fit into the bore of the column above; they are bolted together with four lugs cast on the top and bottom of each column. The joints are turned and fitted together with the greatest nicety to ensure a perfect bearing. The feet upon which the columns rest vary from 3 to 5 feet in height, a have a plate 8 feet square resting upon a bed of masonry, also vary from 3 to 5 feet, carried down to the solid rock, into which they are joggled, plugged, bolted, and secured with sulphur joints.

The piers are all the same pattern, but the number of tiers in a column vary in each, the columns forming the upper tier are connected together at the top by stronger horizontal girders than those used below. Each pier is surmounted by triangular trusses, upon which the girders rest.

The girders are of wrought iron, and of the triangular form, known as "Warren and Kennard’s patent", each consisting of a stout compression beam and tension bar, connected together by diagonals; the whole being supported by a top member, on the principle of inverted truss. These girders are 150 feet long and 14 feet 6 inches deep. The compression beam is comprise of plates and angle iron, (fig. 6 plate 38), riveted together as to form a box girder, 14 inches deep and 9 inches at the greatest width, the distance between the sides being 4 and 5/8 inches, the thickness of the top and bottom plates as also that of the sides vary, extra stiffening pieces are carried along the bottom, as likewise at the joints, and where the bolts cross. The tension member is formed by a series of 4 inch wrought iron bars, 6 inches by 5/8 of an inch on the average, placed in pairs 3 inches apart, to admit the diagonals and packing, as shown fig. 9; these bars reach from diagonal to diagonal, where they are all four united by means of plates, 3 feet long by 16 inches deep to which they are riveted, with 7/8 rivets. There are eighteen diagonals in each girder, acting alternately as struts and ties until they gradually approach the centre, where they act as both. These diagonals are fixed to the top and bottom members, with pins 3 inches in diameter, and as we have before observed, it is upon these pins that the strength of the girder depends. The diagonal ties and struts are of different sections, the struts being in the shape of a cross, (fig. 12), formed by plates riveted together by means of four angle irons, see fig. 12, plate 38. The ties are form of two flat iron bars 9 inches wide, by thickness marked on fig. 11, with the exception of the two nearest the centre, which are constructed exactly similar to the struts, to enable them to act in the double capacity of ties and struts.

A portion of the tension member situated between the four centre diagonals is strengthened by an additional bar 4 inches wide, introduced between the other two riveted like them to the junction plates.

The whole girder is likewise gradually strengthened by an additional thickness of plates towards the centre, the amount being determined by a careful calculation of the strains to be resisted. The vertical plates, forming both members, diminish from 1 inch in the centre 5/8 of an inch at the ends. Each pair of girders is stayed laterally at a point near the main pins by a 5 inch cast iron hollow truss, with ½ inch thickness of metal. The main pins are past through the ties, diagonals, and packing pieces, in such a manner that the ends of the pins project about an inch, on which is screwed a cast iron cap to prevent them from drawing out. To these caps the cast iron braces just mentioned are bolted by means of flanges.

The method by which the girders are supported, is worthy of particular notice. They are sustained by the end of the upper member only, the lower one remaining suspended; the weight thus rests on the last pin, which passes through the diagonal tie.

The top of the piers are furnished by saddle casting, 3 feet 6 inches long, and 5 inches wide, on the upper surface which is a flat channel ¾ of an inch deep. Under the ends of the top members are place cast iron blocks, hollowed out on the upper surface to receive half the diameter of the pin, and of sufficient depth to raise the bottom flanges of the beam clear of the sliding groove. This block has perfect freedom of action, backwards and forwards in the channel of the saddle, to suite the expansion and contraction of the girder, as effected by the temperature of the atmosphere, or super-incumbent weight; to meet contingency a space of 9 has been left between the first diagonal of the girders and the piers, but the ordinary expansion and contraction of this structure in summer, between midday and midnight, does not exceed 1 ¼ inches.

The roadway is formed of 6 inch planking, bolted to the beams, and the rails are fixed upon longitudinal framed sleepers. An ornamental cast iron balustrade is fixed on each side of the roadway.

Previous to submitting this structure to the inspection of the government officers, experiments were made by the engineers and contractors with a view of testing its stability.

In the first place two engines were drawn over the viaduct at a slow pace, and it was ascertained that the maximum deflection did not exceed ½ of an inch. They next pass over with four engines two abreast, when the deflection was somewhat less than an inch. The whole six engines with their tenders loaded, so as to weigh on the average 52 tons each, were then distributed over one span, first on a single line, and then two abreast, the latter load was allowed to remain stationary for some time, but the deflection did not exceed 1 and 1/8 inch. An engine then passed over at the rate of ten miles and hour for the purpose of ascertaining the amount of oscillation, which proved to be scarcely perceptible. The results were very favourable, for although much more severe than any to which the structure would be liable from any ordinary traffic, still they did not come within 1/5 of the ultimate strength of the structure.


Fig. 1.-Elevations of Viaduct.
 "   2.-Plan of pier on line A B fig. 1
 "   3.-Enlarged elevation of half of one bay.
 "   4.-Plan of girder, part of superstructure and horizontal bracing, half showing bracing at top,
           and half showing ditto at bottom of girder.
 "   5.-Transverse section of half of bridge.
 "   6.-Section showing arrangement of plates, and angle iron showing compression member.
 "   7.-Elevation of part of ditto at the point of connection with struts and ties.
 "   8.-Section of ditto through centre of main pin, showing horizontal bracing at top of girder.
 "   9.-Section through tension bars forming bottom of girder.
 "  10.-Elevation of portion of do.
 "  11.-Section of do, through G. H. fig. 10.
 "  12.-Section of struts.
 "  13.-Section of ditto through the main pin holes.
 "  14.-Side of elevation of do.

Click here for plate 37.
Click here for plate 38.

Home Photos Stories History Old/New Guest-Book