by Various
Available in 585 free installments
Owner:
0.70
0.73
0.72
Do. Case b
3.25
1.7
1.3
1.2
1.15
Large as these loads are on short spans, they are not more than must often be provided for.
Live Load on Railway Bridges.?The live load is the weight of the heaviest train which can come on the bridge. In the earlier girder bridges the live load was taken to be equivalent to a uniform load of 1 ton per foot run for each line of way. At that time locomotives on railways of 4 ft. 8½ in. gauge weighed at most 35 to 45 tons, and their length between buffers was such that the average load did not exceed 1 ton per foot run. Trains of wagons did not weigh more than three-quarters of a ton per foot run when most heavily loaded. The weights of engines and wagons are now greater, and in addition it is recognized that the concentration of the loading at the axles gives rise to greater straining action, especially in short bridges, than the same load uniformly distributed along the span. Hence many of the earlier bridges have had to be strengthened to carry modern traffic. The following examples of some of the heaviest locomotives on English railways is given by W.B. Farr (Proc. Inst. C.E. cxli. p. 12):?
Passenger Engines.
|
Total weights, tons |
84.35 |
98.90 |
91.90 |
85.48 |
|
Tons per ft. over all |
1.58 |
1.71 |
1.62 |
1.61 |
|
Tons per ft. of wheel base |
1.92 |
2.04 |
1.97 |
1.95 |
|
Maximum axle load, tons |
19.00 |
16.00 |
18.70 |
18.50 |
Goods Engines.
|
Total weight, tons |
77.90 |
78.80 |
76.46 |
75.65 |
|
Tons per ft. over all |
1.54 |
1.50 |
1.54 |
1.51 |
|
Tons per ft. of wheel base |
2.02 |
2.02 |
2.03 |
2.00 |
|
Maximum axle load, tons |
15.90 |
16.00 |
13.65 |
15.50 |
Tank Engines.
|
Total weight, tons |
53.80 |
58.61 |
60.80 |
47.00 |
|
Tons per ft. over all |
1.60 |
1.68 |
1.70 |
1.55 |
|
Tons per ft. of wheel base |
2.45 |
2.52 |
2.23 |
3.03 |
|
Maximum axle load, tons |
17.54 |
15.29 |
17.10 |
15.77 |