Substructure provides all load groups as defined in AASHTO LFD Table 3.22.1A and AASHTO LRFD Table 3.4.1.1 and Table 3.4.1.2. You can use these load groups directly, or create your own load groups (e.g., you may need to create seismic load groups).

Each load in the load group is given as either unidirectional or reversible. A reversible load is where both positive and negative values are considered in the load combinations. A unidirectional load only considers its positive value in the load combination. In AASHTO LFD, only W, WL, LF, and EQ are reversible loads. The rest of the loads are unidirectional. For AASHTO LRFD, BR, WS, WL, and EQ are reversible. Note that self-weight (SW) of structure is always associated with dead loads (DL). If you do not select a dead load, the self-weight will not be considered in the results of load combinations and envelopes.

Substructure provides a special load group (i.e., limit state) for seismic design. In the AASHTO Standard, this is the "Seismic" group and in the AASHTO LRFD this is the "Extreme Event Seismic" group. When such a load group is defined and then selected for analysis and design, the program generates a separate envelope for it. When column design is performed, the program also determines the plastic hinge moment in columns. When cap and footing design is performed, the program considers the column plastic hinging moment and performs a separate check for this special load group responses.

For LRFD California, two special load groups are included: FATIGUE I and STRENGTH II. FATIGUE I uses only fatigue live load and centrifugal force for fatigue (LLf and CEf). This group is a Substructure combination. The STRENGTH II group uses only permit live load and centrifugal force for permit (LLp and CEp). Both types of loads —LLf and LLp— have special types of trucks input in the truck library.