So, I made a 2D plane stress model of a rectangular PSC beam. The tendon is a straight tendon. I try to make a time-dependent analysis for elastic modulus that varies with time using a predefined field (field type), as recommended here. The tendon stress is also defined as a predefined field with a pressure type assigned to the tendon. First, I defined the updated elastic modulus for each time case in the material properties as presented in Figs. 1 and 2. There are 34 time cases ranging from 28 days to 358 days, with a time increment of 10 days.
Then, I created a step with a time period of 358 and made the increment 1 to make it easier when extracting the results, as shown in Figs. 3 and 4.
After that, I created a predefined field with a field type and assigned an amplitude to it. The created amplitude was equally spaced with a time span of step time, as seen in Figs. 5 and 6.
Finally, I submitted the job and tried to extract the results, especially the tendon stress at the middle length and the concrete stress at the middle length of the top beam, tendon location, and bottom beam. But I found that the results, as presented in Fig. 7, were strange, and only in the last time case (358 days) did the results seem right. I compared it to the results, as shown in Fig. 8, when I created steps as much as the desired time case (in my case, 34), as seen in Fig. 9, and then modified the magnitude in each step according to the defined amplitude magnitude, as illustrated in Figs. 10–12. And the results when the 34 steps were created and the magnitude changed in each step were in good agreement with the hand calculation results.
But when I extract the field variable for each time case, the results come out right, as presented in Fig. 13.
Can people point out what I did wrong with the first method (when I only created one step)? Because, as you know, it will take more time to use the second method (create the step as much as the desired time case) when the time case is large and it is done manually as well.
Abaqus
