316 
TIMBER 
stiffer than one, doubtless owing to the friction between the 
surfaces. 
Bolts increase the friction and produce a marked effect 
on the stiffness of beams, although, with bolted beams as 
with unbolted, the upper beam slides over the one below it. 
In the case of flitch beams, that is, whole or cut timbers 
laid side by side and bolted together, tests show that the 
main difference between these and simple beams of the 
same scantling is that they break more suddenly. 
Loads placed upon timber columns, as upon columns of 
other material, should be in the centre, as all tests show 
that columns eccentrically loaded give considerable reduc- 
tions in strength, and Lanza found this particularly 
noticeable in the case of oak columns.^ 
The question of compression at right angles to the grain 
and the shearing strength of timber has not as yet been so 
carefully studied as that for transverse strength and com- 
pression parallel to grain. 
Pine and spruce will only bear about one-seventh, hickory, 
oak, ash, and some of the Austrahan hardwoods about 
one-half to one-fourth, of the load at right angles to 
the grain which they will bear parallel to the grain 
so that, in the case of timber columns carrying heavy loads 
and having these loads transmitted to timber base plates 
or caps, proper precautions must be taken that the load on 
the side timber is not excessive. 
Judging by a large number of tests on different timbers 
it may be stated generally (although a few samj)les on 
p. 310 show the contrary) that the strength in cross com- 
pression is higher than in shearing, and in some of the harder 
timbers considerably higher (see tests, pp. 120 and 219). 
' "Applied Mechanics," G. Lanza, and " The Practical Column under 
Centre and Eccentric Loads," by J. M. Moncrieff, M. Am. Soc. C.E., 
American Society of Civil Engineers, Vol. XIjV., 1901. 
