Hello,
I am a graduate student , currently working on modelling prestressed concrete hollow core slabs using ATENA.
The test specimens have a constant thickness of 203 mm, total length of 5,000 mm, and are simply supported over a clear span of
4,850 mm. No strengthening has been provided for the test specimen which I am currently studying. The reinforcement has been provided using 9 mm diameter for strands with total area of reinforcement as 384 square mm. The  effective prestressing force is 464.6 KN after considering losses. Since there are 7 strands  for reinforcement, I divided the prestressing force by 7 to get a corresponding prestressing force for each of them. I tried using all the possible bond models for reinforcement provided by the software and also tried applying prestressing force in the initial step or dividing it in 10 steps and applying gradually. I have applied loading at rate of 2 KN per step. After trying all possible ways, I am still not able to get yielding ..even after reaching 160 KN. For the same test specimen, when tested in the laboratory, yielding started at around 80 KN. There is a major difference in the results that I am getting. The corresponding deflection for 160 KN that I have obtained using atena is 12 mm , which is almost 10 times less than what I am expecting. Could you please suggest some possible solutions or ways that I can adopt to rectify this ?
Thanks in Advance.