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I came across 2 creep coefficient diagram. First one is from Eurocode, second one is from elsewhere. I think the second one make sense, As the time progress, the creep coefficient shall increase, hence, the effetive modulus of concrete shall decrese. Can someone explain it ? I am confused.

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  • $\begingroup$ I think you need to define what are the axes represent in the Euro Code. The second graph seems to indicate that with time increases (x-axis), the shrinkage rate increases (y-axes). $\endgroup$ – r13 May 4 at 16:00
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You are looking at a diagram for an infinite duration of loading, which is noted by the $\infty$-symbol. For a limited duration of loading, refer EN 1992-1-1 annex B.1.

Just for clarity, the time shown on the first diagram, $t_0$, is the concrete age when loading starts, which is why the creep coefficient decreases with increasing $t_0$.

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  • $\begingroup$ Do you mean the first graph ( from EUrocode) present the creep of concrete that is loaded at different age (creep of concrete will be less when the concrete is older, concrete loaded after sometime ) ? While the second graph showed that the creep of concrete over time (concrete loaded at t =0 ) ?? Am I right ? Thus, (in second graph, as the time progress, creep will be higher? ) (In first graph, for older concrete, the creep will less noticeable than fresh concrete ? ) $\endgroup$ – utk2366 May 5 at 2:13
  • $\begingroup$ The second graph from the other source is missing a definition of the aging coefficient for me to interpret it properly, but they appear to show almost the same thing: The more hardening prior to loading the less creep. The difference is the second graph has a fixed duration of loading instead of a fixed concrete age, which doesn't really change anything for practical purposes. $\endgroup$ – ingenørd May 5 at 15:15
  • $\begingroup$ Can i say that the first diagram in the first post present the final creep coefficient at diffrent age of loading (creep coefficient will be decreasing and become constant after concrete fully harden) ? While in Annex B present the creep coefficient with time at diffrent age of loading ? $\endgroup$ – utk2366 Jun 7 at 7:24
  • $\begingroup$ Hence, annex B is used to find the creep coefficient ratio at certain time only at different age of loading ? $\endgroup$ – utk2366 Jun 7 at 7:24
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Creep rate for steel does not change with time. That is the basis of ASME Boiler code allowable stresses. Most of the world uses boiler code ; often they rewrite it for national pride. Superalloys (gas turbine blades and vanes) also have constant creep rate at constant temperature. Depending on how it is measured , it may appear to change as the cross-section area of the test bar changes with strain and constant load. Footnote: Over 60 years ago , some creep test machines had curved load arms ( that changed the load) to compensate for the diameter reduction of test bars as the the tests progressed.

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