combinations of actions
accidental design situation
key element
modified structural systems


The paper discusses two main design strategies when checking for reliability and considers accidental action combinations according the various codes. If accidental actions can be identified, one of the possible design strategies is checking the “key element”. This strategy minimizes the possibility of local failure and subsequent progressive collapse. The combination of actions for accidental design situation for checking of the “key-element” resistance was proposed. In addition, the values of the combination factors for variable loads and partial factors for permanent loads in accordance with required reliability class RC for structural element and values of accidental loads was proposed. The second strategy is checking modified structural systems in accidental design situation from unidentified accidental actions. For this case, a comparison of several probabilistic models was performed, as well as a probabilistic assessment of the accidental action combinations according the various codes.



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