There are some fundamental assumptions of Eurocodes that work in the background of every single design. We often take these for granted or simply forget their existence. This blog post is designed to recap these underlying foundations that underpins every piece of design.
Reliability
How does Eurocode consider a structure to be adequate? A design is considered to be adequate if it is verified to have sufficient reliability. Reliability is verified by ‘partial factor method’ in two limit states – ultimate limit state and serviceability limit state. Partial factors provide an uplift on unfavourable loads and a reduction on favourable loads. The verification is considered satisfactory when both ultimate limit states. ULS calculations always use characteristic values whereas SLS calculations typically use ‘mean’ values. See this blog post for the Partial Factor method: https://www.si-eng.org/blog/partial-factors
In Eurocode language, the ‘mean’ values for actions are called ‘quasi-permanent’ actions. It represents the typical conditions the structure is subject to during its life of use.
Eurocode0 is limited to static loading and quasi-static loading where the dynamic effects are assessed using equivalent quasi-static loads and dynamic amplification factors. Non-linear and dynamic analysis are provided in EC1 to 9.
Quality
The reliability of Eurocode is on the premise of having adequate quality assurance in place, to properly execute the design method and implement the construction.
This includes:
· The design and construction is subject to adequate supervision and carried out by competent personnel
· Proper quality control procedure is in place
· Construction has been executed with materials and method as specified
Use and maintenance
Even if a structure has a design with an adequate degree of reliability, and has been properly executed by a competent contractor with adequate quality control procedure in place, its use and maintenance fundamentally affects its performance. The structure is adequately used for its intended purpose and well maintained as required by the designer.
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