The design philosophy embodied in this specification is based on the concept of limit state design. Structures are designed and proportioned taking into consideration the limit states at which they would become unfit for their intended use. Two major categories of limit-state are recognized - ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability, while that in serviceability is deflection.

The following sections describe the salient features of the design approach. In STAAD.Pro, members are proportioned to resist the design loads without exceeding the limit states of strength, stability, and serviceability. Member selection is done on the basis of selecting the most economic section on the basis of the least weight criteria. It is generally assumed that you (the engineer) will take care of the detailing requirements, such as the provision of stiffeners, and check the local effects like flange buckling, web crippling, etc.

Tapered member design is limited to I-sections with a tapered web, rectangular hollow sections, and circular sections. The additional design checks for bending required for these members is described in Tapered Members. Tapered member design is limited to EN 1993-1-1 only (i.e., no National Annex checks are considered for these members). Haunch members as described in EN 1993-1-1 are not designed in STAAD.Pro.

You are allowed complete control over the design process through the use of the parameters listed in D5.C.6 Design Parameters. Default values of parameters will yield reasonable results in most circumstances. However, you should control the design and verify results through the use of the design parameters.