141
OF ENGINEERING FORMULÆ.
Angles of Roofs.
Load on Roofs.
Exclusive of Framing.
Lead covering weighs .. ..
Zinc ......................
Corrugated iron ..........
Slates .. ..................
Tiles......................
Boarding, f thick ..........
Ditto, 1^ thick..............
Timber framing for slated or
tiled roofs .. ..
Additional load for pressure
of wind..................
Steepest angle of Gothic roofs
Per Square ot
100 supl. feet.
7 CWt
U „
3 „
H to 9 „
8 to 15 „
2i „
5 „
5 to 6
36 „
..........
Minimum
alone.
4°
4° •
4°
25|° to 30c
2ui° to 30°
25°
6IT
Pkbssuke of Wind on Roofs. (Unwin.)
a = Angle of surface of roof with direction of wiud.
F = Force of wind in lbs. per square loot (see page 386).
A = Pressure normal to surface of roof = F. gin. a 1'84 cos. a-1
B = Ditto, parallel to direction of wind ±= F, sin. a I’M cos. a
C Ditto, perpendicular to do. do. 3= F. cot.asin.a 1-84 ew.a
Angle of roof=a 5° I 10° 20° 30° 40° 50° I 60° 70° I 80° | 90°
A = F x •125 -24 •4S •66 •83 -95 |1’00 1-021-01!1-00
B = F X •122 -24 'I -I' ' •42 •57 •64 -61f -50 •351 -17! -00
C =F X •01 04 ■15 •33 •53 •73 -85 _____________ •96] -991-00