Load Combinations

The special seismic load combinations required by the specified Building Code or Standard are generated automatically by the program. The seismic load combinations are generated automatically based on the selected seismic code. The generated load combinations are those required by the seismic code when the ultimate seismic force is being calculated.

For AISC 341-05/10/16 ASD the load combinations referred to in section 4.1 (B2) are taken from ASCE 7 (05/10-16) IBC 2006/2009/2012/2015/2018 (12.4.3.2) and represent:

( 1.0 + 0.14 × Sds )D ± 0.7Ω _o Q_E

( 1.0 + 0.105 × Sds )D ± 0.525Ω _o Q_E + 0.75 L + 0.75(Lr or S)

( 0.6 – 0.14 × Sds )D ± 0.7Ω _o Q_E

For AISC 341-05/10/16 LRFD the load combinations referred to in section 4.1 (B2) are taken from ASCE 7-(05/10/16) IBC 2006/2009/2012/2015/2018 (12.4.3.2) and represent:

( 1.2 + 0.2 × Sds )D + (1.0 or 0.5)L + 0.2 S ± Ω _o Q_E

Q_E( 0.9 – 0.2 × Sds )D ± Ω _o Q_E

For AISC 2002 the load combinations referred to in section 4.1 are taken from IBC 2000/2003 and represent:

( 1.2 + 0.2 × Sds )D + 0.5L + ( 0.2 or 0.7 ) S ± Ω _o Q_E

( 0.9 – 0.2 × Sds )D ± Ω _o Q_E

For AISC 1997 the load combinations refer to the load combinations 4-1 and 4-2 as follows:

1.2D + 0.5L + 0.2S ± Ω _o Q_E

(4-1)

0.9D ± Ω _o Q_E

(4-2)

For UBC 1997 LRFD the load combinations refer to the load combinations 3-7 and 3-8 as follows:

1.2D + 0.5L ± Ω _o Q_E

(3-7)

0.9D ± Ω _o Q_E

(3-8)

For UBC 1997 ASD the load combinations refer to the load combinations defined in section 2213.5.1 as follows:

1.0D + 0.7L ± Ω _o Q_E

(5-1)

0.85D ± Ω _o Q_E

(5-2)

It is important to note that a large portion of the checks performed in the Seismic Provision mode use the load combinations defined in the Steel-Standard Provision Mode. The engineer should ensure that the currently selected standard provision load combinations (generated and custom) are appropriate for the checks to be performed in the Seismic Provision mode.

Dynamic and "Other" load cases are not included in the generated combinations but can by used in combinations created by the user. The user can create any number of additional load combinations.

When creating user-specified load combinations, the plus and minus combinations should both be explicitly created. The load factors should be "normalized" as explained above.