Steel Buildings in Europe

Part 3: Actions 3 - 2 2 SAFETY PHILOSOPHY ACCORDING TO EN 1990 2.1 General format of the verifications A distinction is made between ultimate limit states (ULS) and serviceability limit states (SLS). The ultimate limit states are related to the following design situations:  Persistent design situations (conditions of normal use)  Transient design situations (temporary conditions applicable to the structure, e.g. during execution, repair, etc.)  Accidental design situations (exceptional conditions applicable to the structure)  Seismic design situations (conditions applicable to the structure when subjected to seismic events). These events are dealt with in EN 1998 [7] , and are outside the scope of this guide. The serviceability limit states concern the functioning of the structure under normal use, the comfort of people and the appearance of the construction. The verifications shall be carried out for all relevant design situations and load cases. 2.2 Ultimate limit states and serviceability limit states 2.2.1 Ultimate limit states (ULS) The states classified as ultimate limit states are those that concern the safety of people and /or the safety of the structure. The structure shall be verified at ULS when there is:  Loss of equilibrium of the structure or any part of it (EQU)  Failure by excessive deformation, rupture, loss of stability of the structure or any part of it (STR)  Failure or excessive deformation of the ground (GEO)  Failure caused by fatigue or other time-dependent effects (FAT). 2.2.2 Serviceability limit states (SLS) The structure shall be verified at SLS when there is:  Deformations that affect the appearance, the comfort of users or the functioning of the structure  Vibrations that cause discomfort to people or that limit the functional effectiveness of the structure  Damage that is likely to adversely affect the appearance, the durability or the functioning of the structure.