Load combinations for strength design are applied automatically according to reinforced concrete, stuctural steel and seismic regulations.
İnternational Design Codes
ASCE 7-16 : Load Combination and Strength Design
Structures, components, and foundations are designed so that their design strength equals or exceeds the effects of the factored loads in the combinations given in Codes. Combinations are applied to consider one or more effects together. General load types defined in codes are given below.
The load effects obtained as a result of these load types are combined with appropriate coefficients to form combinations. When a structure is subject to seismic load effects, it is considered together with seismic load effects and other effects such as dead load, live load. Load combinations are used to determine design strength of any element.