960 ; REPORT-—1890. 
4, Factors of Safety. By W. Bayuey Marssaut, M.Inst.C.L. 
The factor of safety for materials used in constructional ironwork, bar iron of 
various sections and plates, whether the material is puddled or ingot iron, has 
usually been taken at 5 tons per square inch for ordinary quality and 6 tons for 
specialiy good material. This limit is based upon a total resistance of about 23 tons 
per square inch, and an assumed elastic limit of from 50 to 60 per cent. of the 
total stress. 
The importance of considering the elastic limit in determining the factor of 
safety, or of ascertaining what stress any particular member will bear before it 
begins to stretch, has frequently been demonstrated. 
In the tables appended to the present paper the writer has endeavoured to show 
that the elastic limit is the only constant quality in bar and plate iron; and that 
whilst she total stress is frequently influenced by, and the reduction of area and 
extension seem almost absolutely to depend upon, the shape of the specimen operated. 
upon, yet the elastic limit remains constant, notwithstanding considerable variation 
in the dimensions of the specimens operated upon :— 
Tons per square). 5 5 
4 Original Original inch 5 | 2 43 
care ize of piece Area |———_——___| 99 | 8 
ae Devesption in feet in feet |Elastic) Total 3 = & 8 
limit | stress | © 5 n 
1 |iplate . : . | JL x 0°25 0377 | 13°38 | 18°6 4:5 3 
2 | 2plate . : . | 2:02 «061 1232 | 13-7 | 22:7) 10 11 
3 | 6x6x1 angle. . | 1:51 x0°95 1-434 | 13-9 | 23:5 | 11 13 
4 |4xibar. A .| 200 x052 1040 | 13:8 | 19°2 | 16 8 
5 | 3x3xdbar . .| 75 x0-52 0910 | 13:9 | 21-7 | 20 14 
6 | 5x2 bar. , . | 202 x0°76 1535 | 13°8 | 223 | 21 20 
7 | 44x4ixangle .| 194 x0°70 1:358 | 13:9 | 226 | 21 17 
8 33 x3ixzangle .| 2°005 x 0:62 1:243 | 13:9 | 23:5 | 22 20 
9 | 3$x1 bar f | 1:25 x097 1212 | 13:7 | 22:1 | 23 19 
10 | 8xlbar. 3 . | 1:505 x 1:02 1535 | 13-5 | 227 | 23 22 
ll | 3}x3xZangle . | 202 x0502 | 1:014 | 13:8 | 22:2) 24 20 
12 | 6x4xiitee . .| 151 x0°70 1057 | 13°8 | 22°38 | 27 22 
13 | 24x bar : . | 2°51 x0:76 1907 | 13:6 | 21:7 | 30 29 
14 | 2x} bar : . | 2:02 x 051 1030 | 13:7 | 21:5 | 32 26 
‘15 | 6x5girder . . | 150 x 0:48 0-720 | 13:9 | 238] 32 27 
16 | 21 round. . | 1:29 dia. 1:307 | 13-5 | 23:0 | 36 28 
17 | lj round. A . | 1465 dia. 1685 | 13:7 | 23:1] 42 29 
18 | lround . : . | 0°94 dia. 0°693 | 13:5 | 22:6 | 44 25 
19 | #round . : . | O75 dia. 0-441 | 136 | 21:9 | 45 26 
20. | li round . ; .| 1:13 dia. 1:000 | 13:7 | 22-7 | 55 29 
21 | plate . 5 .| 1:51 x 0°62 0936 | 14:2 | 20:2 7 4 
22 | 5x5xangle. . | 1:12 «0°83 0930 | 141 | 23:5 | IL 10 
23 | 8xl1bar. ; - | LOL x 0:97 0-980 | 14:4 | 22-7 | 11 16 
24 | 7x3bar. ; «| 1:27 x0°75 0-953 | 144 | 214] 16 10 
25 | 6x5xlangle. .| 100 x0-96 0960 | 14:1 | 223 | 16 11 
26 | 64x4xf angle .| 201 x0:54 1085 | 140 | 23:4 | 17 13 
27 | 6x5girder . .| 150 x 054 0810 | 14:4] 218 | 19 14 
98 |5xibar. . .| 1:97 x0515| 1014 | 140] 22:9] 20'| 19 
29 |12x%bar . .|°201 x0575| 1155 | 142] 22:7] 21 | 18 
30 |Z plate. . .| 201 x015 | 0-302 | 141] 345 | 23 | 13 
31 |2ixgbar . .| 2015x066 | 1:329 | 142] 22-7] 23 | 19 
32 |8plate . . .| 1:885x0-40 | 0-754 | 140| 229] 25 | 21 
33 | 2x2" bar . . | 2:00 x054 | 1:080 | 14:2| 223] 25 | 23 
34 | 42x4hxSangle .| 148 x060 | 0888 | 141 | 220) 28 | 20 
35 |2 plate. . .| 1:25 x056 | 0-700 | 141 | 264| 32 | 26 
36 |Jdround. . .| 1:26 dia. 1:247 | 144] 236] 38 | 28 
37 | 2iround. . .| 1-285 dia. 1:297 | 14-4 | 228] 41 | 31 
38 | 1" round. . | 41:04 dia. 0'849 | 14:11 22°81 48 26 
