Civil Engineering Reference
In-Depth Information
As shown in Fig. 1.3, all flow and structural quantities are treated as vectors within
the coordinate system they belong, except the quantities associated with torsion. Cross
sectional rotation and the corresponding torsion moment are considered positive with the
windward front face up, which is a long standing practice in wind engineering. However,
it should be noted that such an inconsistency can not be accepted in a finite element
format, and thus, in chapter 9 a strictly vector description has been adopted, see Fig. 9.2.
1.4 Structural design quantities
Design calculations are intended to cover a certain unfavourable loading condition, e.g.
an extreme storm situation, that is characteristic to the particular place where the
structure is located, and whose probability of occurrence is suitably small. In this
situation it is the comparison of structural strength or capacity to the extreme value of
some critical stress or stress resultant that is of interest. The situation is illustrated in Fig.
1.5. Since structural behaviour is assumed linear elastic, these quantities may in general
be obtained from the extreme values of the displacements
()
( )
max
rx
rxt
,
k
yz
θ
,,
+
⎣
⎡
⎤
⎦
where
=
(1.9)
k
k
Fig. 1.5
Bending moment design quantities
