The Principles of Bridges: Containing the Mathematical Demonstrations of the Properties of the Arches, the Thickness of the Piers, the Force of the Water Against Them, &c. Together with Practical Observations & Directions Drawn from the Whole

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T. Saint, 1772 - Bridges - 102 pages

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Page 83 - ... current may flow freely without the interruption of a pier ; and that the two halves of the bridge, by gradually rising from the ends to the middle, may there meet in the highest and largest arch; and also, that by being open in the middle, the eye in viewing it, may look directly through there. When the middle and ends are of different heights, their difference however ought not to be great in proportion to the length, that the ascent and descent may be easy ; and in that case also it is more...
Page 90 - ... river out of its course above the place of the bridge, into a new channel, cut for it near the place where it makes an elbow or turn ; then the piers are built on dry ground, and the water turned into its old course again, the new one being securely banked up.
Page 99 - ... when the bottom of the river could not be laid dry; and these stilts were surrounded, at a few feet distance, by a row of piles and planks, &c, close to them like a coffer dam and called a sterling or jettee; after which, loose stones, &c, are thrown or poured down into the space, till it be filled up to the top, by that means forming a kind of pier of rubble or loose work, which is kept together by the sides of the starlings: this is then paved level at the top, and the arches turned upon it.
Page 90 - ... the outer or upper line of the wall above the arch ; but it often means only the upper or exterior curve of the voussoirs. FOUNDATIONS, the bottoms of the piers, &c, or the bases on which they are built. These bottoms are alu-ays to be made with projections, greater or less according to the spaces on which they are built.
Page 79 - ... are also * made either with piles only, driven close by one another, and sometimes notched or dove-tailed into each other, or with piles grooved in the sides, driven in at a distance from one another, and boards let down between them in the grooves.
Page 92 - ... digged out for that purpose ; and then the foundation, on a grating of timber. laid on their tops as before. Or, when the bottom is not good, if it be made level, and a strong grating of timber...
Page 82 - ... the breadth being still more contracted by the piers, this will increase the depth, velocity, and fall of the water under the arches, and endanger the whole bridge and navigation. There ought to be an uneven number of arches, or an even number of piers ; both...
Page 83 - ... expect to do in looking at it, and without which opening we generally feel a disappointment in viewing it. If the bridge be equally high throughout, the arches, being all of a heignt, are made of one size, which causes a great saving of centering.
Page 86 - Ixittnui level and rightly; for by opening the sluice, the water will rush in and fill it to the height of the exterior water, and the weight of the work already built will sink it; then by shutting the sluice again, and pumping out the water, it will be made to boat again, and the rest of the work may be completed. It must not however be sunk except when the...

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