PSI - Issue 64

André Weber et al. / Procedia Structural Integrity 64 (2024) 74–80 Weber A. / Structural Integrity Procedia 00 (2019) 000 – 000

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If bigger areas are broken, the loads for the remaining section are increased and the probability of a failure for these areas is also increased. This leads to a progressive failure. In figure 1 the failure ponts are depicted for different loads and diameters. The higher the load, the higher the initial strain, the shorter the time to failure. Interesting is that the diameter or the initial strength (as function of the diameter) seems to have no effect on the time to failure curve. This simplifies a later detailing as in this case diameter can be exchanged without changing the design values.

Figure 1 creep rupture failure points for different diameters In figure 2 we see the principle of time temperature shifting. Higher temperatures lead to shorter times to failure, while lower temperatures lead to higher times to failure. For the general design in outside buildings and structures 40°C is taken into account. This summarizes also higher temperatures up to 65°C with their higher impact on time to failure. A simplified model with the background for this rule can be found in fib (2007) and Weber (2012). t rep ≈ t min + 0,75 x (t max – t min ) For indoor applications without big temperature fluctuations or shorter loading times a higher resistance can be taken into account.