How is the sustained loads ration used in you software
Thank you for your question which relates to the Combined concrete cone and pull-out failure checks.
Given that fastenings must ensure safe load transfer over many years, their long-term behavior is of greatest importance.
When verifying the “combined pull-out and concrete cone failure” of chemical fasteners, Eurocode 2 Part 4 adds an additional coefficient Ψsus which is the effect of tension loads acting permanently on the fastening (sustained
loading). Permanent dead loads decrease the bond strength of the chemical fastening over an extended period of sustained loading. This coefficient is product-specific and can be found in the product’s European Technical
Assessment (ETA) document. It is factored into the design by considering the ratio of the value of sustained loading related to the value of short-term loading. If no value is specified in the ETA, a default coefficient of Ψsus = 0.6 is applied. Hilti’s PROFIS Engineering software simplifies post-installed anchor design based on each chemical anchor’s unique Ψsus coefficient in its ETA.
Important Note: The Ψsus figure is 0.6 by default unless the chemical anchor is retested to the new test standard and a
new ETA with a higher value is published.