What type is the tower bridge

Londoners were thrilled. Once the bridge was completed in , however, the public was appalled with the results. Jones' original design was simple and had a medieval style. But Jones died in , and Barry added his own artistic touch. When the Tower Bridge opened to traffic in , the journal The Builder cursed the bridge, calling it "the most monstrous and preposterous architectural sham that we have ever known.

Educators' Guide Shop. From big blockbusters to video games, Tower Bridge has appeared on screen too many times to count. In another universe, Tower Bridge might have looked very different. Discover some of the designs put forward for a new London river crossing in the 's.

From the inception of its design and the Bridge's construction through to the amazing feats that have happened since, David leads you on a journey of discovery along the key historical dates in greater detail.

Whether you're planning a visit or researching for a school project, there's plenty more to learn about Tower Bridge. Discover more about Tower Bridge. Please note there are currently pavement closures on Tower Bridge until 12 November, please allow extra time to follow diversions and reach the entrance. More info. English French Spanish German Italian. A brief history Built between and , the Bridge has spent more than a century as London's defining landmark, an icon of London and the United Kingdom.

Choosing the design for a new river crossing. Building the Bridge. How it works. Key dates. Looking for more history? Dive deeper into the articles below, which explore some of the historical feats in more detail. The day a bus jumped Tower Bridge.

Read more. Discover the history for yourself. The best way to discover the history of Tower Bridge is to step inside the icon itself. Plan your visit. The two side spans, each feet long, are of the suspension type. They are carried on stout chains that pass at their landward ends over abutment towers of moderate height to anchorages in the shore. At their river ends the chains pass over lofty towers which are themselves connected at an elevation of feet above high water.

Heavy tie bars, at the level of the connecting girders, unite the two pairs of chains so that one acts as anchorage for the other at the centre. The central span has two high-level foot ways side by side, and one low-level roadway. High-level girders carry the upper footways, which are reached by hydraulic lifts or staircases in the main towers. The roadway, or central opening span, is feet long and consists of two bascules or leaves.

The Tower Bridge Act laid down that when the bridge was open there should be a clear headway at high tide between the water and the high-level footways of feet and a headway of 29 feet when the bridge was closed.

These dimensions were exceeded in practice, the open height being 5 feet and the closed height 6 in. This was above high-water level. The greatest extreme between high and low tide at Tower Bridge is 25 feet. The Act further stipulated that the piers were to be feet long and 70 feet wide. There was also a clause making it compulsory to maintain at all times during the building of the bridge a clear waterway feet wide.

This stipulation made it impossible for the two piers to be built at the same time, because the staging would have occupied far too much of the river space. As the use of timber cofferdams was prohibited, the builders had to rely on caissons. The restricted area which they were allowed for their staging, feet by feet, did not permit the use of one caisson extending the full length of a pier.

The builders therefore adopted a system of small caissons covering the area of the pier. By this means it was possible while building one of the piers to be working also at the shore side of the other. Had both piers proceeded simultaneously a saving of thirteen or fourteen months might have been effected. The piers of the Tower Bridge are much more complicated structures than the piers of an ordinary bridge.

In addition to supporting the towers carrying the overhead girders for the high-level footways and the suspension chains of the fixed spans, they also house the counterpoise and the machinery which operates the bascules. The caissons used for securing the foundation of the piers consisted of strong boxes of wrought iron, without either top or bottom. To secure a good foundation it was found necessary to sink them to a depth of about 21 feet into the bed of the river.

There were twelve caissons for each pier. On the north and south sides of each pier was a row of four caissons, each 28 feet square, joined at either end by a pair of triangular caissons, formed approximately to the shape of the finished pier. There was a space of 2. The caissons enclosed a rectangular space 34 feet by The space was not excavated until the permanent work forming the outside portion of the pier had been built, in the caissons and between them, up to a height of 4 feet above high-water mark.

The method adopted in building and sinking the caissons was unusual. First came the building of the caisson upon wooden supports over the site where it was to be sunk. The caisson was 19 feet in height and it was divided horizontally into two lengths. The lower portion was known as the permanent caisson and the upper portion, which was removable when the pier was completed, was called the temporary caisson.

The object of this upper portion was simply to keep out water while the pier was being built. When ready the supports were removed and the permanent caisson lowered to the river bed this had previously been levelled by divers by means of four powerful screws attached to four lowering rods. After the caisson had reached the ground various lengths of temporary caisson were added to the permanent section, till the top of the temporary portion came above the level of high water.

The joint between the permanent and the temporary caissons was made tight with india-rubber. Divers working inside the caisson excavated first the gravel and then the upper part of the clay forming the bed of the river. As they dug away the soil, which was hauled up by a crane and taken away in barges, the caisson gradually sank until its bottom edge penetrated some 5 feet to 10 feet into the solid London clay.

London clay is a firm watertight stratum, and when the desired depth had been reached by the caisson it was safe to pump out the water, which up to this time had remained in the caisson, rising and falling with the tide through the sluices in the sides. The water having been pumped out, navvies were able to get to the bottom of the caisson and to dig out the clay in the dry.

Additional lengths of temporary caisson were added as the caisson sank, so that at last each caisson was a box of iron 57 feet high, in which the preparation of the foundations could be made.

The caisson having been controlled from the first by the lowering rods and screws, its descent any farther than was desired was easily arrested by the rods when the bottom of the caisson was 20 feet below the bed of the river. The clay was then excavated 7 feet deeper than the bottom of the caisson, and outwards beyond the cutting edge for a distance of 5 feet on three of the four sides of the caisson. In this way not only was the area of the foundations of the pier enlarged but, as the sideways excavation adjoined similar excavations from the next caissons, the whole foundation also was made continuous.

All the permanent caissons, with the spaces between them were then completely filled with concrete, upon which the brickwork and masonry were begun in the temporary caisson and carried up to 4 feet above high water. The preparation of the foundations was a long and troublesome task because of the extent of the river traffic, which made it difficult to berth the necessary barges.

When the cutting edge of one of the caissons had reached a depth of 16 feet beneath the river bed, water rushed into the caisson through a rent in the clay.

The caisson had to be lowered still further to seal the opening when the water was pumped out. The second blow was due to one of the stage piles between the caissons having been driven in aslant.