A Treatise On The Principles And Practice Of Dock Engineering
Forfatter: Brysson Cunningham
År: 1904
Forlag: Charles Griffin & Company
Sted: London
Sider: 784
UDK: Vandbygningssamlingen 340.18
With 34 Folding-Plates and 468 Illustrations in the Text
Søgning i bogen
Den bedste måde at søge i bogen er ved at downloade PDF'en og søge i den.
Derved får du fremhævet ordene visuelt direkte på billedet af siden.
Digitaliseret bog
Bogens tekst er maskinlæst, så der kan være en del fejl og mangler.
DISTRIBUTION OF PRESSURE ON KEEL-BLOCKS. 489
L B, we have K L B as thé pressure diagram for an overhang of one-fourth
the vessel’s length.
For overhangs greater than this, we may proceed by analogy thus:—Take
the point M as the limit of the supported length, and make O T = 2 O M.
MT
Then the eccentricity of the point O is O Z =■—g—. Hence, make
2 W
M N = 2
where Z2 is the length of effective base M T. Join N T, and MN T is the
pressure diagram. Although the vessel apparently receives support from
T to B, such, as a matter of fact, is not the case, the compressive stress
passing through zero value at T to a negative value beyond that point. In
other words, there would be a gradually inereasing tensile stress from T to
B, if the vessel were fastened down to the blocks.
Similarly, if the forefoot extend to P, take 0 8= 2 O P. Draw
P Q = 2 a3, where
a3Z8 = Wj as before.
Join Q Sj, and P Q S is the pressure diagram under these conditions.
Any number of points may be found in this way, and since
LKxKB=NMxMT=QPxPS=2W,
we may write down the general equation—
a: y = constant, ...... (135)
so that the curve L N Q is a rectangular hyperbola, with its origin at O,
and the lines 0 A and O R as its asymptotes.
This equation is only applicable to values of x not exceeding K O.
When the overhang of the vessel is less than one-fourth of the total length,
the compression does not vanish at B, but gradually inereases as the forefoot
decreases, until it attains a maximum value of B C, with the disappearance
of all overhang at the stem.
Consequently, we must substitute for (135) another equation conforming
to the altered conditions. We obtain this readily from the investigation in
Chap. v. already alluded to. There it was seen that when the eccentricity
was less than one-sixth of the base, the value of the greatest intensity
of pressure at the outer, or nearer, edge of the joint was
Y = a + y,
where a = the uniform intensity due to zero eccentricity under similar
conditions of load, and
Gax
y =
x being the eccentricity.
Apply this to the case where the rise of the vessel’s stem begins at the
point I. Then the length of base is I O = Z4, and
W
«4 = -7-
'4