. Railroad structures and estimates . place of the concrete and timber base sometimes a solidaoor 24 inches thick made up of 12X12 timbers drift-boltedtogether is used as a floating platform on which the masonry isbuilt, and sunk into position over the piles, the piles having pre-\iously been cut off by an under-water saw. The objection to this method is the liability in case of an ice shove for the pier to slide between the platform and piles. All piers and abutments should be sufficiently protected from . scour, which is one of the chief sources of bridge failures. This i can only be done by
. Railroad structures and estimates . place of the concrete and timber base sometimes a solidaoor 24 inches thick made up of 12X12 timbers drift-boltedtogether is used as a floating platform on which the masonry isbuilt, and sunk into position over the piles, the piles having pre-\iously been cut off by an under-water saw. The objection to this method is the liability in case of an ice shove for the pier to slide between the platform and piles. All piers and abutments should be sufficiently protected from . scour, which is one of the chief sources of bridge failures. This i can only be done by taking foundations down to solid bottom and anchoring the masonry to the foundation bed by large stone bolts, or dowels. In running water they should be further protected by stone riprapping all around; and when the clearance is limited and ; severe ice shoves are likely to occur, crib protection piers filled . with stones, placed 25 to 50 feet ahead of each pier up stream, should be used. 86 QUANTITIES IN BRIDGE PIERS. Base of Rail. Fig. 19. Bridge 42. - APPROXIMATE CUBIC YARDS IN ONE PFER. (Fig. 19.) Width of piers. B. Ft. 0 (For girders 13-foo\ centers or less.) Total height. 10 14 18 22 26 30 34 38 42 46 oO 04 ft. ft. ft. ft. ft. ft. ft. It. ft. ft. ft. ft. 39 56 74 93 Ill 137 161 186 214 243 274 306 45 64 84 105 129 155 ISO 208 238 269 304 338 50 71 q8 lis 143 171 200 231 263 298 334 3/1 5() 7Q 104 131 159 189 220 254 289 326 36o 4Ub G2 88 115 144 175 207 242 278 317 358 399 443 68 ()6 l?6 158 191 227 264 303 ■MA 387 433 480 75 106 138 17^ 209 247 287 329 373 420 46; 518 81 115 150 187 226 267 310 355 403 454 504 boS 88 124 165 203 245 289 335 383 434 486 5411 5981 58ft. _ 34d3764124494S9529570614657 TABLE \TE CUBIC YARDS IN ONE PIER. (Fig. 19.)(For girders over 13-foot centers up to 20-foot centers.) Total height. Width of piers•• B. Ft. In. 6 0 6 6 7 0 7 6 8 0 8 6 9 0 8390OS106114123132 117127139150161174186 152166181195211227241 1902
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