The LRFD combinations are given in Section 1605.2, "Load combinations using strength design or load and resistance factor design". The template files are RamSteelIBC2000_LRFD.cmb and RamSteelIBC2003_LRFD.cmb
The IBC lists the following combinations:
| 1.2D + 1.6L + 0.5Lr | (Formula 16-2) |
| 1.2D + 0.5L + 1.6Lr | (Formula 16-3) |
| 1.2D + 1.6Lr + 0.8W | (Formula 16-3) |
| 1.2D + 0.5L + 0.5Lr + 1.6W | (Formula 16-4) |
| 1.2D + 0.5L + Snow + E | (Formula 16-5) |
| 0.9D + 1.6W | (Formula 16-6) |
where
|
E
| = | ρ QE ± 0.2 SDS D (see Sec. 1617.1.1) |
|
QE
| = | the Seismic force from the analysis. ρ is the Reliability/Redundancy Coefficient as explained previously |
If the Roof Load has been specified as Snow in the Criteria – Live Load Reduction command in the RAM Manager, the user may specify whether to use the full factor (0.7) or the partial factor (0.2) on the Snow load, or disregard the Snow entirely when in combination with seismic forces, as specified for f2 in Section 1605.2.1.
Note: The 0.5 factor on Live Load should be 1.0 in cases of public assembly loads, live loads greater than 100 psf, and parking garage loads, but that is not implemented. Custom combinations can be created if necessary.
The generated load combinations can be viewed using the Reports – Load Combinations command.
