Civil Engineering Reference
In-Depth Information
Figure 5.8
Examples of influence lines for an
arch roof and a tower.
Figure 5.8(b) shows the influence line for the bending moment at a point in an arch
roof. In this case, the sign of the influence line changes along the arch. Thus, wind
pressures applied in the same direction at different parts of the roof may have opposite
effects on the bending moment at
C, M
c
.
It is important to take into account these non-uniform influences when considering the
structural effects of wind loads, even for apparently simple structures, especially for the
fluctuating part of the loading.
5.3.6
Along-wind response of a structure with distributed mass—modal
analysis
The usual approach to the calculation of the dynamic response of multi-degree-of-
freedom structures to dynamic forces, including resonance effects, is to expand the
complete displacement response as a summation of components associated with each of
the natural modes of vibration:
(5.16)
