April 28, 2015

Bridges and viaducts


Viaduct „Modruš1“ is the first and the longest in the row of three viaducts of the same name at the road section Ogulin- Brinje of the Highway A1 Zagreb-Split- Dubrovnik, at approach to the tunnel Mala Kapela. The object is situated near the settlement and the ruin of the old town of Modruš which once was also the seat of the Modruška County and can be seen from the right side when driving toward Brinje. The viaduct bridges a deep valley at the height up to 50 m from the lowest point of the valley and has a total length of 516 m and a total width of 31.5 m, enabling thus in standard profile the traffic on highway in both driving directions. Due to that many drivers even do not notice that they have crossed over a remarkable road construction building. In order to get an impression of the size of this viaduct one should exit to a parallel state road D23. The construction actually consists of two parallel, almost identical viaducts each serving one driving direction, which are transversally interconnected for the purpose of checking and maintenance. The levelling line of the viaduct is ascending 4.8% toward the tunnel Mala Kapela. The viaduct consists of 13 sections with centre-to-centre distances of the props (pillars): 38+11x40+38m = 516m. Particular construction spans consist of four prestressed ferroconcrete pillars with coffer cross-section, 2.2 m high and 37 m long, interconnected with a roadway slab. Particular span constructions lean on beam heads of pillars, by means of separate bearings.
The lower structure of the viaduct consists of abutments and pillars based on laminated ferroconcrete foundations, in consideration of rocky basic grounds. The foundations of pillars are 10.0x8.0x2.0 m. The abutments with parallel wings are based in the similar way. The pillars of the viaduct are hollow, of outer cross-section of 2.4 x5.4 m and with the wall thickness of 0.3 m. Used materials are ferroconcrete and prestressed concrete.
The project of the viaduct was made by IGH-Institute for Concrete and Masonry Structures, the designers were Gordana Trogrlić-Uzelac, Stjepan Kralj and Dr. Sc. Petar Sesar. It was built by the company Bechtel-Enka with participation of Croatian companies. The viaduct was opened for traffic in 2005 on the occasion of opening of the A1 Zagreb- Split Highway.


The River Krka, a jewel among rivers of the Adriatic drainage area, probably the most beautiful and attractive among them and well known for its waterfalls, was bridged when the A1 Highway was built, at a point few kilometres downstream from the town of Skradin by an impressive arch bridge. The bridge is located between the nods Skradin and Šibenik, and immediately behind it there is a rest area with a restaurant and viewpoint, from where the view of the bridge and the town of Skradin can be enjoyed. Especially attractive is the view at the bridge for yachtsmen heading to Skradin. The total length of the bridge is 391 m, the width is 22.5 m and it rises 66 meters above the sea level. The main span construction of the bridge over the river Krka is a hollow ferroconcrete arch of 204 m, i.e. 4 m bigger than the bridge of Maslenica (200 m). The cross-section of the arch is 3x10m, with the walls of 0.5 m. As much as 2988 m3 of concrete and 747 t of reinforcement have been built into the bridge, which was constructed according to cantilever principle and with cable support. The structure of the bridge above arch is composed of the grid of steel longitudinal and cross beams with cantilever projections and with rim beams. The longitudinal beams are coffered with cross-section of 0.75x1.7 m and a span of 32 i.e. 28 m. On the described grid a ferroconcrete slab of roadway of 25 cm has been laid. The described structure above arch contains 1700 tonnes of steel, 2172 m3 of concrete and 630 tonnes of reinforcement and it leans on the terrain and the arch of the bridge, by means of pillars reaching up to 55 m. The pillars are of hollow cross-section varying from 3.2x2.5 to 1.8x2.2 m in dependence of their height. Each pillar position has two equal pillars.
It should be pointed out that in the construction of this bridge rational technical solutions have been applied which have made possible – by respecting all prescribed conditions - a savings on the total mass of the object of 35 % in relation to almost identical Maslenica bridge.
The designer of the bridge was Dr. sc .Zlatko Šavor, the supervisor was IGH Zagreb - Dr.sc. Z. Marić, and the bridge was built in the period 2002- 2005 by the company “Konstruktor inženjering Inc.” from Split with the steel part built by the company “Đuro Đaković Ltd.” from Slavonski Brod. The bridge was opened to traffic together with the opening to traffic of the highway Zagreb –Split in 2005.

Stamp Issue: 2015.04.23

March 2, 2015


Reason and inspiration
The Bridges stamp issue celebrates the leaps in engineering that have seen the UK’s bridges evolve from humble stone crossings to dramatic symbolic landmarks conceived by progressive architects. The stamp images feature British bridges constructed from a wide range of different materials, including gritstone, limestone, cast iron, wrought iron and steel, while referencing diverse styles of bridge engineering, from clapper and stone arch to suspension and bowstring girder.

Stamp details
Designed by London agency GBH, the ten photographic stamps from locations spanning the whole UK, are arranged chronologically: pre-1600 – Tarr Steps, River Barle; 1700s – Row Bridge, Mosedale Beck; c.1774 – Pulteney Bridge, River Avon; 1814 – Craigellachie Bridge, River Spey; 1826 – Menai Suspension Bridge, Menai Strait; 1849 – High Level Bridge, River Tyne; 1850 – Royal Border Bridge, River Tweed; 1911 – Tees Transporter Bridge, River Tees; 1981 – Humber Bridge, River Humber; 2011 – Peace Bridge, River Foyle.

The origins of Tarr Steps, which crosses the River Barle in Exmoor National Park, are not definitively known. It has long been suggested that the structure could be up to 3,000 years old, but recent research reveals it is most likely to date from the 15th or 16th century. Tarr Steps is a most elemental bridge formed by large slabs of gritstone – weighing up to 2 tons each and varying in length from 2 to 2.9 metres – placed flat on broad, low piers made from blocks of stone. Comprising 17 spans, the 55-metre bridge is held together by weight with no system of fixings or mortar. Serious flood damage over the years has resulted in substantial rebuilding and repairing of the original stones, but Tarr Steps remains an outstanding example of clapper-bridge construction.

Believed to have been constructed in the mid 18th century, this packhorse bridge over Mosedale Beck at Wasdale Head in Cumbria is a fine example of a type of bridge common in Western Europe in the Middle Ages. Goods were often carried in panniers slung from packhorses, so bridges on trade routes could be narrow, making them quick and cheap to build. The relative lightness of the loads carried by this type of bridge – simply single rows of packhorses – meant that their forms could be daring, with added strength given to the material used through bold and ingenious design. Typically, as with Row Bridge, they were conceived as high semi-circular or segmental stone-built arches (an inherently strong form), often crossing a river or chasm in one slender span.

Designed by the esteemed Scottish architect Robert Adam, Pulteney Bridge in Bath is the UK’s finest example of an ‘inhabited’ bridge. Completed by 1774, it contains shops, originally with accommodation above, and was built to link the ancient centre of Bath with the proposed new Bathwick estate on the opposite bank of the River Avon. Adam based his structure on an unbuilt design by the great 16th-century architect Andrea Palladio, which the Italian had entered into a competition to build a bridge at the Rialto in Venice. Though Palladio’s scheme was not selected, it was published and became an inspiration for 18th-century architects such as Adam, whose resulting creation, made from mellow Bath stone, with its three semi-circular arches and pedimented centre pavilion, is one of the most beautiful classical bridges in the world.

Designed by Thomas Telford and completed in 1814, Craigellachie Bridge carries the roadway on a single 46-metre-long arched span over the River Spey in Moray, Scotland.
Telford had the arch made of cast iron, which was revolutionary at the time because, unlike masonry, only iron could achieve the single long, slender and shallow arch required. The components were cast at a Welsh foundry in controlled conditions to ensure high quality and delivered to the site for assembly. Cast iron is very strong in compression but has low tensile strength, making it ideal for columns but not for beams. Well aware of the metal’s structural limitations, Telford built the bridge ensuring that the maximum number of its components are in compression. The span of the arch is restrained by masonry towers, designed in picturesque manner to look like miniature castles.

Completed in 1826 to Thomas Telford’s design, the Menai Suspension Bridge linking the island of Anglesey to the Welsh mainland remains one of the most breathtaking bridges ever built in Britain.
The central span of its roadway, 176.5 metres long and set 30 metres above water level to allow tall-masted ships to pass beneath, was carried by 16 wrought-iron chains (since replaced by steel chains).
The road on either side of the central span is supported by tall and elegant arched limestone viaducts. With a total length of 305 metres, this was the world’s first great suspension bridge and established the potential of suspension-bridge technology to achieve both high and lengthy spans.

Linking Newcastle-upon-Tyne with Gateshead, the High Level Bridge is one of the most innovative and visually powerful bridges created during Britain’s Railway Age.
This two-tier 408-metre-long bridge, designed by Robert Stephenson to carry road and rail traffic at a high level across the Tyne and allow tall-masted shipping below, is a hymn to the strength, utility and robust beauty of cast iron, used in combination with stone and wrought iron. The tall piers, up to 40 metres high, are made of local sandstone, which possesses great compressive strength and is able to withstand damp, while the iron bow-string girders forming the spans of the bridge (the widest being 38.1 metres) use cast iron for components that are in compression and wrought iron for elements that require tensile strength.

Crossing the River Tweed between Berwick-upon-Tweed and Tweedmouth, the Royal Border Bridge was constructed between 1847 and 1850 to the design of Robert Stephenson and was a key component in Britain’s expanding railway system, linking London to Edinburgh.
Of traditional masonry construction, the bridge is essentially a railway viaduct formed of 28 semi-circular-headed arches, each with a span of 18 metres, with the total length of the bridge – including approach works – reaching 658 metres. This vast extent, combined with the majestic 38-metre height of the arches as they cross the river and the slender form of the vertical piers, from which the arches spring, gives the structure a striking elegance. A superb piece of functional engineering, it is also a work of great beauty that complements the rugged border landscape through which it passes.

Completed in 1911, the Tees Transporter Bridge in Middlesbrough is a most novel and visually arresting piece of engineering. Vast in scale and utilitarian in appearance, its stripped-back, lattice-steel structure incorporates a pair of cantilevered trusses that span 259 metres – with a clearance above water of almost 49 metres – that are used to carry a ‘gondola’ across the river. Powered by electric motors, the gondola – which can convey both people and vehicles – is suspended above the river and pulled from one side to the other by a hauling cable in approximately two minutes. This unique design – executed by Sir William Arrol & Co. of Glasgow – was economic to construct and ensured that the crossing would not interfere with river traffic.

More than a century after the notion of a bridge or tunnel crossing the Humber estuary had first been debated, the eventual completion of the Humber Bridge in 1981 redefined the boundaries for suspension-bridge technology.
Its complex construction, by consulting engineers Freeman Fox & Partners, took nine years. With a total length of 2,220 metres and a central span of 1,410 metres between two towers of reinforced concrete, for 16 years the Humber Bridge was the longest single-span suspension bridge in the world. Its mighty scale, elegant minimal form and the fact that it leaps across one of England’s great natural boundaries has captured the imagination. The poet Philip Larkin, who lived in Kingston-upon-Hull, wrote ‘Bridge for the Living’, a poem that was set to music to celebrate the opening of the Humber Bridge.

Spanning the River Foyle in Derry/Londonderry in Northern Ireland, the Peace Bridge functions not only as an urban route, but also as a work of art. Its ingenuity is expressed through delicacy and elegance.
This unique bridge, constructed for pedestrians and cyclists, was conceived as two distinct structural systems that work in absolute harmony. Completed in 2011 to the designs of Wilkinson Eyre, the Peace Bridge features a pair of tall masts, whose system of cables overlap mid-river to form a symbolic structural ‘handshake’ across the Foyle. The 235-metre-long pathway of this self-anchored suspension bridge provides a promenade and makes connections, while evoking a sense of pride, place and unity.

Stamp Issue: 2015.03.05