ABSTRACT
A saddle surface is a translation one that includes two systems of archesone convex (direction x in Figure 6.1.1) and the other concave (direction y).
f b
f a
b b
a
a
y
x
z
o fa + fb
c
- N x
+ N y
N xy
The surface equation is:
2 2a b x yz f f a b
= − (6.1.1) For example, the rise of point c at the shell corner (where x = – a, y = –
b) relative to point o is:
zc = fa – fb (6.1.2)
The lines that connect the surface center, o, and the corners (for example co, shown in Figure 6.1.1) are straight ones, i.e., the surface is a linear one in diagonals’ directions (hyperbolic paraboloid; see also Section 1.2.4).
