A Treatise On The Principles And Practice Of Dock Engineering

426 DOCK ENGINEERING. bending moment eaused by representative heavy engines running on British railways, with an addition of 2^ per cent, for possible future increa.se. TABLE XXXIV.—Equivalent Distributed Live Loads Derived from Maximum Bending Moments for a Single Line of Way. Span in Feet. Selected Engines. Single Driver. 4-Wheel Coupled. 6-Wheel Coupled. 8-Wheel Coupled. 10-Wheel Coupled. Tons Distri- buted. Tons per Ft. Run. Tons Distri- buted. Tons per Ft. Run. Tons Distri- buted. Tons per Ft. Run. Tons Distri- buted. Tons per Ft. Run. Tons Distri- buted. Tons per Ft. Run. 10 36-9 3-69 36-9 3-69 36-9 3-69 34-6 3-46 39-9 3-99 15 381 2-54 46-6 311 48-8 3-25 50-28 3-35 55-8 3-72 20 44 0 2-20 57'6 2-88 56 2 2-81 63-5 3-18 68-9 3-44 25 51-5 2 06 65-4 2-61 66-3 2-65 73-8 2-95 83-7 3-35 30 61-2 2-04 73-6 2-45 74-7 2-49 83-2 2-77 98-5 3-28 35 71 1 203 82-6 2-36 84-0 2-40 91-4 2-61 106-9 3-06 40 80'4 201 89-0 2-22 92-4 2-31 98-8 2-47 115-3 2-88 45 90'0 2-00 95-6 2-12 99-0 2-20 105-6 2-34 120-2 2-67 50 99-0 1-98 105-3 2-10 104-0 2-08 112-3 2-24 125-0 2-50 60 116'0 1-93 124-8 2-08 117-6 1-96 126-0 2-10 136-3 2-27 70 135-3 1-93 142-8 2-04 132-3 1-89 140-5 201 158-9 2-27 80 152-7 1-91 160-4 2-00 150-4 1-88 159-2 1-99 180-8 2-26 90 172-0 1 91 176-4 1-96 168-3 1-87 176-4 1-96 202-5 2-25 100 188-6 1-88 193-3 1-93 186-0 1-86 192-0 1-92 223-7 2-24 125 233-8 1-87 240-0 1-92 232-5 1-86 240-0 1-92 278-7 2-23 150 277-5 1-85 288-0 1-92 279-0 1-86 286'5 1'91 333 0 2-22 175 316-8 1-81 336-0 1-92 325-5 1-86 332-5 1-90 385-0 2-20 200 352-3 1-76 383-2 1-92 370-0 1-85 378-0 1-89 435-3 2-18 For cartways and vehicular tracks, a rolling load of 10 to 15 cwts. per foot run should be a sufficient estimate in ordinary cases. Special vehicles may, however, carry loads equivalent to a ton per foot run. Floats or lorries for heavy goods vary in size between about 14 feet 9 inches by 6 feet 9 inches to 17 feet 6 inches by 7 feet 6 inches. The former generally carry loads up to 7 or 8 tons and the latter up to 10 or 11 tons, though 12, and even 15, tons may be reached under certain circumstances. Traction engines will exert a pressure of 300 to 600 Ibs. per square foot over the area of their wheel-bases. The weight of a crowd of men is generally taken at 80 to 84 Ibs. per square foot. Dr. Stoney records an experiment in which he succeeded in packing a number of labourers in an enclosure, so closely as to produce a pressure of 147 Ibs. per square foot. It would not be injudicious, therefore, to assume 100 Ibs., or even 1 cwt., as the possible amount of concentrated load upon footways. Practical Application.—By way of illustration of the theoretical methods involved in designing a movable bridge, an outline of the calculations for finding the reactions at the points of support in a specific instance is appended.