Figure 13 Crossflooding through a series of structural ducts with 1 manhole
k

= 
0.2748
• L_{i}
+ 0.0313 if 0 < L <
1_{i}

k

= 
—0.0986
• L_{i}
^{3} + 0.6873 • L_{i}
^{2} – 1.0212 • L_{i}
+
0.7386 if 1 ≤ L_{i}
≤ 4

Note:
k is
the friction coefficient related to each space between two adjacent
girders. k is evaluated with effective crosssection
area therefore in calculations use the real crosssection area A and
not S_{equiv}. The pressure loss for entrance in the first
manhole is already computed in the calculation, and k = 1 has to be
added to take into account the outlet losses.
Figure 14 Crossflooding through a series of structural ducts with 2 manholes
k

= 
0.4045
• L_{i}
+ 0.0627 if 0 < L
< 1_{i}
< 1

k

= 
0.0424
• L_{i}
^{3} – 0.3593 • L_{i}
^{2} + 1.1401 • L_{i}
–
0.356 if 1 ≤ L_{i}
≤ 4

Note:
k is
the friction coefficient related to each space between two adjacent
girders. k is evaluated with effective crosssection
area therefore in calculations use the real crosssection area A and
not S_{equiv}. The pressure loss for entrance in the first
manhole is already computed in the calculation, and k = 1 has to be
added to take into account the outlet losses.