1) It won't be "more accurate" to enter 7 points instead of 2 for FRP bars. I suppose that failure in you study should occur due to bond failure rather than bar rupture so 2 points would be more than enough.
2) 7 bars are accounted by effective area in the bar definition. There is area calculator where you define rebar size and number and then get area calculated.

Some other considerations:

3) In a lap-splice study the governing parameter is bond relationship. I hope you have some reliable bond functions for bars in use.
4) Hasnat Ahmed was working on a similar study as I remember. You can check his posts on this forum.
5) Example models that are installed along with the ATENA are very helpful. Please check them, you can find multiple examples of similar models.

I am simulating the  four point bending test.
My topic is numerical investigation on the lap-splice length between Glass-Fiber-Polymer reinforcement and stainless steel reinforcement in concrete.   I have three different lap splices.   I need to define stress-strain relationship and bond strength-slip relationships  for GFRP rebars. I have questions. 
1). in Atena-GiD stress-strain relationship starts from 2 to 7 multilinear functions.  As you know, GFRP shows almost linear relationship in tension test which has no yield strength.

So  for Reinf 1 (yield strength ) which value should I enter? (I have tension test results). 

Is it more accurate if I enter 7 multilinear function than 2 linear?

2). in 2D models, I am confused that I have 7 GFRP and 7 stainless steel rebars in tension zone. So How can I take into account this rebars in 2D?  (If I enter 7 in the number of bars section under basics in GiD).

If anybody  already simulated lap-splices before, please give me your e-mail or contact

Best regaards,
ErSultan