Most falseworks
are designed to support
but in practice
they are also subjected
to forces in the horizontal plane.

These result
from dynamic effects
as the rapid pouring
or vibrating of concrete,
from the movement of ten-
sioning cables,
from the wind, from differential
under heat or load,
and from many
other causes.

Some of these forces
can be estimated
but others can not,
and the fact
that they
are usually contained
is no proof
that they are not important.

They may be
particularly significant
in skew spans
where displacements in two
perpendicular directions
produce unexpected strains
in the third,
or in cases where
the design loads are applied
rather than simultaneously.

Taken from an article (that I have, without reason, kept for a very long time) on the Building Standard 449:1959 – The use of structural steel in building. Submitted by Kim Rooney.