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Louis Alexis Beaudemoulin

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Louis Alexis Beaudemoulin, born 24 December 1790 in Paris, died 25 June 1877 in Paris, was a French engineer, chief engineer of ponts et chaussées (bridges and roads).

See French Wikipedia entry.

1870 Description of experiments with a bridge de-centering apparatus. 'In 1847, M. Beaudemoulin, Ingenieur en Chef des Ponts et Chaussees, made use of sand in decentering arches, applying its peculiar property when in its ordinary state of division of not conveying appreciable strains to its envelopes, even when under the direct action· of considerable weight.
At first linen bags were successfully employed; afterwards iron cylinders filled with sand were used, upon which the pressure was distributed by means of a wooden piston. The first application of the cylinders was made in 1854, at Paris, in the works of the Pont d'Austerlitz. Since that time they have been frequently employed. In 1864 and 1865, Marechal made use of sand bags on a railroad at Brest and found them simple in use and economical.
M. Beaudemoulin, seeing in 1855, at the Pont de l'Alma, the action of cylinders for decentering, noticed defects of which he gave an account in the "Annales des Ponts" (March 20). At the same time he observed important qualities in them which had been even considered as defects, and from these he deduced a new and important process, which he calls differential, which can be employed for as short periods as may be desired; a great advantage in security and precision of working.
This method has become of general application. It was first employed at Paris in 1857, in the simultaneous decentering of the three arches of the Pont Saint-Michel, when 192 cylinders of sand placed at the points of support were made use of. With the old methods as many workmen would have been necessary; but in this case only a dozen were required, and the operation was successfully completed in two hours.
In 1867, Beaudemoulin exhibited at the Great Exposition a new apparatus, superior to that of the iron cylinders then employed, in regularity, precision, and security of working. We have lately tried the action of this apparatus with two sets, one a model 0.161 m. in diameter and 0.0015 m. in thickness, the other a practical working apparatus, 0.314 m. in diameter.
The model consists of 9 rings. The lower ring, 0.155 m. in diameter and 0.056 m. in depth, is fixed in a socket of wood, and is pierced with four holes 0.015 m. in diameter; below each of these a small horizontal piece called bavette is fixed. This first ring is surrounded with a movable collar, carrying four vertical fans, disposed in such a manner that a slight displacement of the collar causes these fans to sweep off the cones of sand from the bavettes. This circle has play enough so as to slide easily. The first piece is also pierced near its upper edge with four holes about on a level, intended for the pins for holding the second ring while the apparatus is being set up. The other eight rings differ only in the absence of the orifices of discharge and of the collar. The dimensions are given in the following table: ....'[1]

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Sources of Information

  1. [1] Engineering 30 Dec 1870