Limit State Design - The purpose of limit state design is to ensure a structure performs under the maximum permissible load and that during normal working conditions remains serviceable i.e. the appearance of the structures is not compromised.
There are two key principles of Limit State Design Ultimate limit state and Serviceability limit state.
- Ultimate Limit State (ULS) – Is a requirement that the structure must be able to support the maximum permissible load, including adequate safety factors to ensure the safety of the structural element and/or the safety of people.
- Serviceability Limit State (SLS) – Is the limit state that concerns the appearance/serviceability of a structure. Typically critical serviceability elements are Deflections, Cracking, Durability and Fatigue.
The importance of each limit state will vary dependent on the nature of the structure. For industrial warehouses the primary objective are to carry the applied loads and minimise the cracking at the surface of the slab.