Limit States Design

General

General concepts about actions on structures are cited in the §1.3 of Volume A', the study of which contributes to the understanding of the actions imposed on an earthquake resistant building.

Two limit states should be taken into account for the design [*]NoteThe term ‘design’, as referred in EC0, could also be translated as study of a structure:

Ultimate Limit State (ULS)

ULS concerns the safety of people and structure. In all cases of gravity, environmental and seismic design actions, the structure [EC0, 3.3. (1)] should have sufficient resistance and serviceability during its design working life [*]NoteThe proposed (national) values for the design life of usual buildings is 50 years and of monumental buildings 100 years. .

Serviceability Limit State (SLS)

SLS concerns the functioning of the structure under normal use, the comfort of people, the appearance of the construction works [EC0, 3.4. (1)] e.g. to avoid high deflection and extensive cracking [*]NoteIn common earthquake resistant buildings of reinforced concrete consisted of structural columns, beams and slabs, without pretension, provided that the relevant structural design rules and provisions of the EC2 and EC8 are followed, ultimate limit state is ensured. Thus the check of serviceability limit state may be omitted. etc.

In limit states design, the unfavourable actions are multiplied by a safety factor γ_f≥1.0 (e.g. γ_g=1.35 for dead loads and γ_q=1.50 for imposed loads), while the material strength is divided by γ_m ≥1.0 (ε.γ. γ_c=1.50 for concrete and γ_s=1.15 for steel).