To avoid stresses and deflections exceeding those given
in the above Regulations along construction elements of variable cross-section,
the required section modulus calculated as for construction elements
of constant cross-section should be increased by a factor K expressed
by:
where α = l
1/l
0, γ = W1/W0
The value
of factor K obtained by the formula should be not less than unity.
l
1, l
0, W1 and
W0 are indicated in the figure 3 below:
Figure 3
The moment of inertia should likewise be increased by the
factor C expressed by:
where α = l
1/l
0, β = I1/I0
The value
of factor C obtained by the formula should be not less
than unity.
I1 and I0 are indicated
in figure 3 above.
The use of the above formulae should be limited to the determination
of the strength of hatch beams and covers in which abrupt changes
in the section of the face material do not occur along the length
of the beam or cover.