Danish Requirements for Robustness of Structures: Background and Implementation

Increased use of advanced types of structures with limited redundancy and serious failure consequences combined with strengthened requirements to efficiency in design and execution as well as increased risk of human errors necessitates requirements for the robustness of new structures, essential. This paper describes the background of the revised robustness requirements implemented in the Danish Code of Practice for Safety of Structures in 2003 [1, 2, 3]. According to the Danish design rules robustness shall be documented for all structures where consequences of failure are serious. This paper describes the background of the design procedure in the Danish codes, which shall be followed in order to document sufficient robustness in the following steps:
Step 1: review of loads and possible failure modes/scenarios and determination of acceptable collapse extent.
Step 2: review of the structural systems and identification of key elements.
Step 3: evaluation of the sensitivity of essential parts of the structure to unintentional loads and defects.
Step 4: documentation of robustness by 'failure of key element' analysis.
Step 5: documentation of robustness by increasing the strength of key elements if Step 4 is not possible.