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Description of a bridge béton, (concrete,) constructed at Grisoles, in the Department of Tarn-et-Garonne, in France
Description era Bridge of .B~ton.
11t~
engines descend long inclined planes, such as tho~ on the Croydoll Railway, tim application of the brake is seldom necessary, the ~a¢d. that would be due to the accelerating force of gravity, being r ~ l ~ d . by the resistance of the atmosphere, until it settles down to a unifol~ and safe velocity. It is evident, therefore, that there is a great deal yet to learn on this subject, when we fil~(t authority and practice feting ~o materially. Mr. Vignoies observed, in conclusion, that, as the laying out of the lines of railway" ottgi~t to be strictly regulated by the power to be used tbr locomotion, as well as of the load of each. train, attd the nature of the traffic, it becomes interesting to consider these principles in respect of the extension of the railway system in this and other countries; for, looking at the enormous outlay hitherto incurred, lines through remote districts would not be undertaken, unless the first cost of railways, and the aunua| expense of working and maintaining them, were reduced to a minimum. To be continued.
Descriptions of a 33rid~e of I3dlon,* (Cow,crete,) conslructed at Grlsoles, i~ the JDeFartment of Tern-el-Carouse, in ~ra~ce.¢ B2/ ~M. L~ntr~, Jlrchilecl, of ~lonlattba~. Translated for the Journal of the Franklin Institute, from the " Bulletin de la ~oeiet~ d'Eneouragement pour l'Industrie INational," for July, 18,~'. By ELI.WOOD M o a a l s , Civil Engineer.
Living in a region where suitable building stone is scarce and expensive, and where brick masonry alone is used, M. Lebrun, guided by the fine works of M. Vicat, on hydraulic limes, conceived tim idea * T h e French bdton is nearly identical with the English ctmcre/e, the main difii-ren~ being in the manipulation ; thus bdlon is composed of lime, sand, and small pebbles, or broken stone, taken separalely, and successively mixed together, the pebbles being added last ; while concrete is usually formed of lime, mixed directly with gravel, containing natu÷ally about the due proportion of pebbles and sand; proper quantities of water being used, and tim factitious stone resulting, in both cases, being in eflhct the s a m e . - - T a . j- B~ton, or concrete, has before been used in retaining walls and other constructions, and, as is stated by Gen. Paslcy, of tt. B. M. corps of Engineers, (in his admirable Treatise or, Calcareous Cements,) it was also applied experimentally to build a military casemate near Woolwieh, of which the arch had lS feet span, 5 feet rise, and 6 feet depth at the crown, and which, when subjected to the direct tire of 24. pounder gm~s, as well as the vertleal plunge of 13 inch shells, loaded to weigh 200 Ibs. each, resisted both with success, and, contrary to expectatimb was less injurcd by the latter, than by the former. General Treussart, of the Ficnch army, after mentio~ing the successful construction of several concrete vaults, recommended this material for aqueduct bridges, and. for the revetnlents of fortresses, in certain situations. Nevertheless, the bridge above described is amongst the first, if not lhe veryjTrs/, construeties of that nature which has been successfully executed for ordinary use. and its succes~ will suggest at once to the mind of the American enginccr, many situations, in tile southern section of the Union, at least, where concrete may thus be used with great propriety and economy ; indeed, its eornparative eheapnes.% in someeases, would fully justify a lair trial of it, even in the northern United States, though the severity of the winters, there, would seem to render its success in that region more problematical. W e must, however, observe, that the failure of the concrete wharf walls, at Woolwich and Chatham, in consequence of tidal exposure, and the necessary protection of the concrete sea wall at 13rizhton, with woodwork, to shield it from the action of water in mass, (as mentioned by Gem Pasley,) points out the necessity of confining the application¢ of concrete to construetion~, within reasonable and prot~er limits.--'l'xt,
164
Civil Eng{neertng,
o f substituting for this masonry the b~ton, which the Romans used with so much advantage. In consequence, he submitted, in 1839, to the Miuister of Public Works, the project of a bridge entirely of bdton, which he offered to construct on the lateral canal o[" Garonne, to be traversed by many of the royal and departmental routes. This oft~r having been accepted, under certain conditions~ M. Lebrnn eommeuced his work in June, I840.
I.--L&leclion and Preparalion of lhe Materials. T h e llme was of the hydraulic quality, burnt in perpetual kilns, by pit coal. The su~d was clear oi all earihy particles, of fine grain, and pretty mfiform. The g'ruvel slones, of" the size o [ a hen's egg, came from the river Garmme. The lime was slaked alternately iu two basins, joiued together. For this purpose, we poured at first, ill one of the basins, a q, mntity of water prol,orfioued to that of the lime which we wished to slake ; we tftcn put ill sn[iieient quicklime tbr the water to cover it; then we left the lime to slake freely without disturbance, except by taking care to pricl," it, t?om time to time, with a stick, to introduce the water into those parts of the basin where the dissolved lime was dry. W h e n tl.c fi~rmentatiou had ceased, we stirred up the lime in every direction with an iron hoe, in order to mix the paste, and render it homogeneous; we left it then in this state, not to be used fbr twelve hours after slaking. The proportioJ,s observed by M. Lebrun (or concretes (b6tons) destined for the col,structiot~ either of walls or arches, were, in every ten. parts, eomposcd of' two parts o[' lime ill paste, three parts of' sand, and five parts of gravel stones, or pebbles. For making the mortars, we placed, on a paved surface, two measures of" the slaked lime, which, after having been well beaten with pestlcs of'east iron, soi~elled agaiJl by yieldiug up a part of the water with wl~ieh it was charged ; then we placed beside it three measures of sand, which we mixed, little by little, with the lime, always having the aid of the pestles, and stirring the whole with the shovel and hoe, in order that all the parts of tile sand should be well incorporated, observing not to put any water intothe mortars, hut, if tile sand was too dry, we moistened it, a few moments before mixing. As soon as the mortars were sufficiently manipulated, we added five measures of gravel stones; the whole was then long and forcibly mixed and pounded, mltil each part of the gravel was su/fieiently enveloped by mortar; then tim b~lons were takeu it1 quantity, to wait fbr the moment of being used. We took care to make only" what we could employ in a day's work~ withot!t which precaution it would have lost its cohesion,
]I.--Conslr~lcNon oft~re Jbulmerds. The lSth of June, 1840, the exeavatiol~ of the foundations of the two abntments being done, we commenced laying the bdlons, taking care~ each time that a layer~ or course, was finished~ to cover it up
Description o.f a .Bridge of B~ton, or Concrete.
16~
immediately with wet nmts of straw, to prevent a too rapid drying by the heat of the sun. l~y means of this precaution, the ne~r course connected itself more intimately with the one below. We continued the masonry all of bdton, (the backing of' the arch and abutments keeping pace,) until reaching the height fixed. The exterior faces of the abutmcltts, (not next the earth,) and of the walls, were formed by some phmks strongly fixed, against which tile b~lon rested. These planks were removed, two or three days after, and the faces of bdton remained exposed, and were very well preserved. At tile height o f the .~pri2~ging of' the arch, we laid five courses of bricks plumb on the thces of the abutments, to serve as perpendicular faces for the centre to fit up against, and enable it to detach itself easily.
III.~Construction oJ' the Cenlre. .Fifleen days after the laying of the last ~[ons, we commenced the eonsmmtion of" the cemre, composed of many courses of bricks, laid fiat, i,~ snoots;don, (fi'om tim spring towards the crown,) following the curve of the arch at the intrados, built partly with plaster, and partly with cement, or hydraulic mortar, and supported at the springing by proj(~eting masonry, or by a timber tbr that pro'pose. The centre was /brined of" four courses of bricks, (in thickness, or depth, say nine ineh(:s;) the three [ower were laid with plaster, and the upper course with cement, to shelter the plaster from the dampness of the b~ton. The ~pper bricks of the centre were covered by a bed of mortar of day, iu order to model perfectly the intrados of the arch, and to hinder ~he hdton fl'om forming one body with the bricks. The construction of the centre being finished on the 17th of A n , ~ s t , we established, three days after, the masonry of the two heads of the arch of brick, (in lieu of ring stone,) which were completed on the 26th of the same month. IV.~Uonsfructlon of the d2rch. Immediately after the construction of the two heads, we wrought them in.to the~general mass of bglon, forming the arch ; /.his operation was fimshed on the 5th of September, with the exception of the backmg up, which was accomplished, on both sides, tile 1 lth of the same month. The bdlons of the arch were composed in tile s a m e manner as those of the abutments, and manipulated by the same process; but we added to it 2~v cubic feet of ceme~t for every 35½ cubic feet, or ~vth, of the mass, to augment the strength of the mortars of the body of the arch. This construction was made without following any regular order, and the b~tons were east in masses, upon the centre, to the thickness of two feet, which formed the first general bed, or layer, oft the development of the arch. This first bed being finished, we tbrmed the second in order to reach the thickness of three feet at the key, the spandrel backing, and the abutments being leveled up. A. coping of hydraulic mortar was then placed aver the whole extent of the arch, and covered immediately with a layer of clay, strongly beaten.
Civil l~nginee~ng.
166
V.--DeeentremenL All was left in this state until the 25th of January, 1841 ; we theft proceeded to the operation of the deeentrement of the arch. TILe28th of January, the centre of bricks wae taken away, and the intrados of the arch appeared very even in all its parts. After three months, it manifested not tim smallest settlement in its masonry, and, since then, the bridge has stood through the summer, without iueurrit,g the least degradation capable of affecting its solidity. This bridge has a clear opening of :3.~}{-t}.~etbetween the abutm(mls ; the middle is placed i~t the axis of the canal, which has two towitlg I)aths ; its breadth is 19-} feet between the heads, or t~mes, of the riLJgs ; and the arch is Ibrmed of a segment of a circle of 3'~}.. l~et chord~ and .5~t4feet rise, or versed sine. The entire mass of lhe abutments is of h(51o,~,except the four angles on the sides of the towing paths, which are of large stone, rounded orl the arris, on account of the rubbing of'the towing lines. The arch is also of b~loJt, as are tile facts of tile tympans, or spandrels, aud. the intrados, with the exception of the artists of tile soliit, or rings of the heads, which are of toriek masollry. ~¢I. Le.brun has joined to his memoir, along with a plan of tile bridge of Grisoles, many certificates, [}'ore the mayor of this eomtm/ne, and from tile engineer of the lateral eangtl of the Garonne, proving the complete success of tim works, and tile solidity of the construction, "whie}~ has endured the ]woof of the passage of loaded carriages, the numerous inllue~lees of heat, and .qOLllO very severe frosts, without having sullL'red the leaat degrad~'~tion.
gI.--E:r])lcznalioaz o/' lhe I~gures.
V
~
,
~
S
N
a, eanal. b, abutment of b~lon. e, mass of arch, also of b~ton. d d, towing paths. e, angles of bridgo l~pon the tow-paths, built of largo stone, with the angles rounded. f , arrises of lhe soffit, or bands of brick at each head of the arch, instead of t|.te usual ring-stone.
11t~
engines descend long inclined planes, such as tho~ on the Croydoll Railway, tim application of the brake is seldom necessary, the ~a¢d. that would be due to the accelerating force of gravity, being r ~ l ~ d . by the resistance of the atmosphere, until it settles down to a unifol~ and safe velocity. It is evident, therefore, that there is a great deal yet to learn on this subject, when we fil~(t authority and practice feting ~o materially. Mr. Vignoies observed, in conclusion, that, as the laying out of the lines of railway" ottgi~t to be strictly regulated by the power to be used tbr locomotion, as well as of the load of each. train, attd the nature of the traffic, it becomes interesting to consider these principles in respect of the extension of the railway system in this and other countries; for, looking at the enormous outlay hitherto incurred, lines through remote districts would not be undertaken, unless the first cost of railways, and the aunua| expense of working and maintaining them, were reduced to a minimum. To be continued.
Descriptions of a 33rid~e of I3dlon,* (Cow,crete,) conslructed at Grlsoles, i~ the JDeFartment of Tern-el-Carouse, in ~ra~ce.¢ B2/ ~M. L~ntr~, Jlrchilecl, of ~lonlattba~. Translated for the Journal of the Franklin Institute, from the " Bulletin de la ~oeiet~ d'Eneouragement pour l'Industrie INational," for July, 18,~'. By ELI.WOOD M o a a l s , Civil Engineer.
Living in a region where suitable building stone is scarce and expensive, and where brick masonry alone is used, M. Lebrun, guided by the fine works of M. Vicat, on hydraulic limes, conceived tim idea * T h e French bdton is nearly identical with the English ctmcre/e, the main difii-ren~ being in the manipulation ; thus bdlon is composed of lime, sand, and small pebbles, or broken stone, taken separalely, and successively mixed together, the pebbles being added last ; while concrete is usually formed of lime, mixed directly with gravel, containing natu÷ally about the due proportion of pebbles and sand; proper quantities of water being used, and tim factitious stone resulting, in both cases, being in eflhct the s a m e . - - T a . j- B~ton, or concrete, has before been used in retaining walls and other constructions, and, as is stated by Gen. Paslcy, of tt. B. M. corps of Engineers, (in his admirable Treatise or, Calcareous Cements,) it was also applied experimentally to build a military casemate near Woolwieh, of which the arch had lS feet span, 5 feet rise, and 6 feet depth at the crown, and which, when subjected to the direct tire of 24. pounder gm~s, as well as the vertleal plunge of 13 inch shells, loaded to weigh 200 Ibs. each, resisted both with success, and, contrary to expectatimb was less injurcd by the latter, than by the former. General Treussart, of the Ficnch army, after mentio~ing the successful construction of several concrete vaults, recommended this material for aqueduct bridges, and. for the revetnlents of fortresses, in certain situations. Nevertheless, the bridge above described is amongst the first, if not lhe veryjTrs/, construeties of that nature which has been successfully executed for ordinary use. and its succes~ will suggest at once to the mind of the American enginccr, many situations, in tile southern section of the Union, at least, where concrete may thus be used with great propriety and economy ; indeed, its eornparative eheapnes.% in someeases, would fully justify a lair trial of it, even in the northern United States, though the severity of the winters, there, would seem to render its success in that region more problematical. W e must, however, observe, that the failure of the concrete wharf walls, at Woolwich and Chatham, in consequence of tidal exposure, and the necessary protection of the concrete sea wall at 13rizhton, with woodwork, to shield it from the action of water in mass, (as mentioned by Gem Pasley,) points out the necessity of confining the application¢ of concrete to construetion~, within reasonable and prot~er limits.--'l'xt,
164
Civil Eng{neertng,
o f substituting for this masonry the b~ton, which the Romans used with so much advantage. In consequence, he submitted, in 1839, to the Miuister of Public Works, the project of a bridge entirely of bdton, which he offered to construct on the lateral canal o[" Garonne, to be traversed by many of the royal and departmental routes. This oft~r having been accepted, under certain conditions~ M. Lebrnn eommeuced his work in June, I840.
I.--L&leclion and Preparalion of lhe Materials. T h e llme was of the hydraulic quality, burnt in perpetual kilns, by pit coal. The su~d was clear oi all earihy particles, of fine grain, and pretty mfiform. The g'ruvel slones, of" the size o [ a hen's egg, came from the river Garmme. The lime was slaked alternately iu two basins, joiued together. For this purpose, we poured at first, ill one of the basins, a q, mntity of water prol,orfioued to that of the lime which we wished to slake ; we tftcn put ill sn[iieient quicklime tbr the water to cover it; then we left the lime to slake freely without disturbance, except by taking care to pricl," it, t?om time to time, with a stick, to introduce the water into those parts of the basin where the dissolved lime was dry. W h e n tl.c fi~rmentatiou had ceased, we stirred up the lime in every direction with an iron hoe, in order to mix the paste, and render it homogeneous; we left it then in this state, not to be used fbr twelve hours after slaking. The proportioJ,s observed by M. Lebrun (or concretes (b6tons) destined for the col,structiot~ either of walls or arches, were, in every ten. parts, eomposcd of' two parts o[' lime ill paste, three parts of' sand, and five parts of gravel stones, or pebbles. For making the mortars, we placed, on a paved surface, two measures of" the slaked lime, which, after having been well beaten with pestlcs of'east iron, soi~elled agaiJl by yieldiug up a part of the water with wl~ieh it was charged ; then we placed beside it three measures of sand, which we mixed, little by little, with the lime, always having the aid of the pestles, and stirring the whole with the shovel and hoe, in order that all the parts of tile sand should be well incorporated, observing not to put any water intothe mortars, hut, if tile sand was too dry, we moistened it, a few moments before mixing. As soon as the mortars were sufficiently manipulated, we added five measures of gravel stones; the whole was then long and forcibly mixed and pounded, mltil each part of the gravel was su/fieiently enveloped by mortar; then tim b~lons were takeu it1 quantity, to wait fbr the moment of being used. We took care to make only" what we could employ in a day's work~ withot!t which precaution it would have lost its cohesion,
]I.--Conslr~lcNon oft~re Jbulmerds. The lSth of June, 1840, the exeavatiol~ of the foundations of the two abntments being done, we commenced laying the bdlons, taking care~ each time that a layer~ or course, was finished~ to cover it up
Description o.f a .Bridge of B~ton, or Concrete.
16~
immediately with wet nmts of straw, to prevent a too rapid drying by the heat of the sun. l~y means of this precaution, the ne~r course connected itself more intimately with the one below. We continued the masonry all of bdton, (the backing of' the arch and abutments keeping pace,) until reaching the height fixed. The exterior faces of the abutmcltts, (not next the earth,) and of the walls, were formed by some phmks strongly fixed, against which tile b~lon rested. These planks were removed, two or three days after, and the faces of bdton remained exposed, and were very well preserved. At tile height o f the .~pri2~ging of' the arch, we laid five courses of bricks plumb on the thces of the abutments, to serve as perpendicular faces for the centre to fit up against, and enable it to detach itself easily.
III.~Construction oJ' the Cenlre. .Fifleen days after the laying of the last ~[ons, we commenced the eonsmmtion of" the cemre, composed of many courses of bricks, laid fiat, i,~ snoots;don, (fi'om tim spring towards the crown,) following the curve of the arch at the intrados, built partly with plaster, and partly with cement, or hydraulic mortar, and supported at the springing by proj(~eting masonry, or by a timber tbr that pro'pose. The centre was /brined of" four courses of bricks, (in thickness, or depth, say nine ineh(:s;) the three [ower were laid with plaster, and the upper course with cement, to shelter the plaster from the dampness of the b~ton. The ~pper bricks of the centre were covered by a bed of mortar of day, iu order to model perfectly the intrados of the arch, and to hinder ~he hdton fl'om forming one body with the bricks. The construction of the centre being finished on the 17th of A n , ~ s t , we established, three days after, the masonry of the two heads of the arch of brick, (in lieu of ring stone,) which were completed on the 26th of the same month. IV.~Uonsfructlon of the d2rch. Immediately after the construction of the two heads, we wrought them in.to the~general mass of bglon, forming the arch ; /.his operation was fimshed on the 5th of September, with the exception of the backmg up, which was accomplished, on both sides, tile 1 lth of the same month. The bdlons of the arch were composed in tile s a m e manner as those of the abutments, and manipulated by the same process; but we added to it 2~v cubic feet of ceme~t for every 35½ cubic feet, or ~vth, of the mass, to augment the strength of the mortars of the body of the arch. This construction was made without following any regular order, and the b~tons were east in masses, upon the centre, to the thickness of two feet, which formed the first general bed, or layer, oft the development of the arch. This first bed being finished, we tbrmed the second in order to reach the thickness of three feet at the key, the spandrel backing, and the abutments being leveled up. A. coping of hydraulic mortar was then placed aver the whole extent of the arch, and covered immediately with a layer of clay, strongly beaten.
Civil l~nginee~ng.
166
V.--DeeentremenL All was left in this state until the 25th of January, 1841 ; we theft proceeded to the operation of the deeentrement of the arch. TILe28th of January, the centre of bricks wae taken away, and the intrados of the arch appeared very even in all its parts. After three months, it manifested not tim smallest settlement in its masonry, and, since then, the bridge has stood through the summer, without iueurrit,g the least degradation capable of affecting its solidity. This bridge has a clear opening of :3.~}{-t}.~etbetween the abutm(mls ; the middle is placed i~t the axis of the canal, which has two towitlg I)aths ; its breadth is 19-} feet between the heads, or t~mes, of the riLJgs ; and the arch is Ibrmed of a segment of a circle of 3'~}.. l~et chord~ and .5~t4feet rise, or versed sine. The entire mass of lhe abutments is of h(51o,~,except the four angles on the sides of the towing paths, which are of large stone, rounded orl the arris, on account of the rubbing of'the towing lines. The arch is also of b~loJt, as are tile facts of tile tympans, or spandrels, aud. the intrados, with the exception of the artists of tile soliit, or rings of the heads, which are of toriek masollry. ~¢I. Le.brun has joined to his memoir, along with a plan of tile bridge of Grisoles, many certificates, [}'ore the mayor of this eomtm/ne, and from tile engineer of the lateral eangtl of the Garonne, proving the complete success of tim works, and tile solidity of the construction, "whie}~ has endured the ]woof of the passage of loaded carriages, the numerous inllue~lees of heat, and .qOLllO very severe frosts, without having sullL'red the leaat degrad~'~tion.
gI.--E:r])lcznalioaz o/' lhe I~gures.
V
~
,
~
S
N
a, eanal. b, abutment of b~lon. e, mass of arch, also of b~ton. d d, towing paths. e, angles of bridgo l~pon the tow-paths, built of largo stone, with the angles rounded. f , arrises of lhe soffit, or bands of brick at each head of the arch, instead of t|.te usual ring-stone.