Seismic cantilevers (beams seismic: ACI 318)
Horizontal cantilever structural members in structures assigned to Seismic Design Category D, E or F are required to be designed to the applicable load combinations plus an isolated minimum net upward force of 0.2* times the dead load.
If a cantilever beam has been marked as a seismic cantilever, then provided the seismic design category = D, E or F the minimum design moment at the restrained end is checked as follows:
Calculate minimum positive design moment:
| Mmin+ | = | 0.2 * Me,dead- |
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where |
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| Mmin+ | = | Minimum positive design bending moment at the restrained end. |
| Me,dead- | = |
Critical negative bending moment at the restrained end due to dead loads only obtained for the considered seismic combination. |
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Check the minimum design moment at the restrained end:
| Mu+ | ≥ | Mmin+ |
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where |
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| Mu+ | = |
Critical negative bending moment at the restrained end due to dead loads only obtained for the considered seismic combination. |
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If the check fails the region is designed for Mu+ = Mmin+