13.6Necessity for Fatigue Assessment

• a) Fatigue assessment is not normally required for building structures except as follows:

1. Members supporting lifting or rolling loads,
2. Member subjected to repeated stress cycles from vibrating machinery,
3. Members subjected to wind induced oscillations of a large number of cycles in life, and
4. Members subjected to crowd induced oscillations of a large number of cycles in life.

• b) No fatigue assessment is necessary if any of the following conditions is satisfied.

1. The highest normal stress range $f_{\mathrm{f}, \mathrm{Max}}$ satisfies

$f_{\mathrm{f}, \mathrm{Max}} \leq 27 \mu_{\mathrm{c}} / \gamma_{\mathrm{mft}}$

2. The highest shear stress range $\tau_{\mathrm{f}, \max }$ satisfies

$\tau_{\mathrm{f}, \mathrm{Max}} \leq 67 \mu_{\mathrm{c}} / \gamma_{\mathrm{mft}}$

3. The total number of actual stress cycles $N_{\mathrm{sc}}$, satisfies

$N_{\mathrm{sc}} \leq 5 \times 10^{6}\left(\frac{27 \mu_{\mathrm{c}}}{\gamma_{\mathrm{mft}} f_{\mathrm{feq}}}\right)$

where

$\begin{aligned} f_{\mathrm{feq}} & =\text { equivalent constant amplitud } \\ & \text { stress range in MPa given by }\end{aligned}$

$f_{\mathrm{feq}}=\left[\frac{\sum_{i=1}^{r} n_{i} f_{\mathrm{fi}}^{3}+\sum_{j=y_{s}}^{r} n_{j} f_{\mathrm{fi}}^{5}}{n}\right]^{1 / 3}$

where

$n=\sum_{i=1}^{k} n_{i}$

: stress ranges falling above and below the $f_{\mathrm{fn}}$, the stress range corresponding to the detail at $5 \times 10^{6}$ number of life cycles.