Ad 1.: See ATENA Troubleshooting, 2.2.3 How can I model Fibre Reinforced Concrete (FRC, UHPC, SHCC) in ATENA? and 2.2.4 I want to use the user-defined stress-strain law of concrete to replace that used in ATENA program. How can I do it?
You may also be interested in the Tutorial for ATENA Science GiD FRC (the current versions of all our manuals are available for download from our web under Products - ATENA - Documentation).

Ad 2.: You can send us your model (see ATENA Troubleshooting, 2.1.1) such that we can try to reproduce the issue.

Regards.

        I am a Master's student. I am doing my thesis on Engineered Cementitious Composite (ECC) or Bendable Concrete.
1. I want to know if I can analyse ECC in ATENA? I have stress strain curve for the same from the experimental results. If yes then
    please give me some idea how to do it?

2. While Analysing simple concrete beam of M45 grade, it is showing "(x) Internal analysis error: Access violation at address
    026CA784 in module 'CCFEModel.DLL'. Read of address 00000C98".

         I am trying it on Demo version. If you can help me I will really appreciate that.

    THANK YOU.

PREETI VERMA