A History of Research and a Review of Recent Developments

Loading/time relationships 77
overpressure. The variations in C d are partly influenced by the proximity of
the ground surface to the boundary layer. Blast loading on arches was
investigated by F.E.Anderson of the US Defense Atomic Support Agency in
1958, and his work was used by Newmark and others in drawing up the
figures.
Anderson also investigated domes, and the results for 45° domes are given
in Figure 4.2 when the peak incident overpressure, p 0, is less than 25 psi. The
variation of C d along the line of symmetry of the dome shows that C d=0 when
the angle a is about 70°. Along a transverse line of a 60° cylindrical arch
under similar loading functions C d is zero when a is about 55°.
In the discussion on the loading of a semi-circular cylinder it was assumed
that the shock front was travelling in a direction normal to the longitudinal
axis of the cylinder. If, however, the shock travels in the same direction as this
axis and first impinges on the flat end of the structure, the values of pressure
ratio and drag coefficient will be similar to those for a rectangular box structure.
All the above loading analyses resulted from research in connection with
the design of structures to resist nuclear weapons effects, so it was presented,
with revisions, during the period 1950 to 1980. However, earlier assessments
Figure 4.2 Blast wave meeting 45° dome (from Newmark et al., ref. 4.2).