BS EN Eurocode Basis of structural design

In the Eurocode system BS EN 1990, Eurocode: Basis of structural design[14] overarches all the other Eurocodes, BS EN 1991 to BS EN 1999. BS EN 1990 defines the effects of actions, including geotechnical and seismic actions, and applies to all structures irrespective of the material of construction. The material Eurocodes define how the effects of actions are resisted by giving rules for design and detailing. See Figure 1.2.

Figure 1.2

The Eurocode hierachy

Figure 1.2

The Eurocode hierachy

BS EN 1990 provides the necessary information for the analysis of structures including partial and other factors to be applied to the actions from BS EN 1991. It establishes the principles and requirements for the safety, serviceability and durability of structures. It <BS EN 1990:

describes the basis for design as follows: 2.1>

A structure shall be designed and executed (constructed) in such a way that it will, during its intended life, with appropriate degrees of reliability and in an economical way:

Sustain all actions and influences likely to occur during execution and use. Remain fit for the use for which it is required.

In other words, it shall be designed using limit states principles to have adequate stability, structural resistance (including structural resistance in fire), serviceability and durability. For building structures, a design working life of 50 years is implied.

BS EN 1990 states that limit states should be verified in all relevant design situations, persistent, transient or accidental. No relevant limit state shall be exceeded when design values for actions and resistances are used in design. The limit states are:

■ Ultimate limit states (ULS), which are associated with collapse or other forms of structural failure.

■ Serviceability limit states (SLS), which correspond to conditions beyond which specified service requirements are no longer met.

All actions are assumed to vary in time and space. Statistical principles are applied to arrive at the magnitude of the partial load factors to be used in design to achieve the required reliability index (level of safety). There is an underlying assumption that the actions themselves are described in statistical terms.

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