how do i get the realistic design model ?

are you using Solid or shell model?

If it is a shell, you could provide a minimum/base thickness for your shell, so that a minimum layer is kept.

If it is a solid, then you can play a little bit more with some optimization parameters such as mininum and maximum member size.

I am using Shell model of 2D Cantilever Beam (L=1000MM, B=100MM, H=100mm ,Thickness=1MM)and i have given base thickness of 0.01 i got model shown below but still there is a lot of quasi elements (blue part )i should have the stiffness(ribs) between the red part (top and bottom)  how do i get the ribs in between the red parts.

thank you

Iso value helps in interpreting designs and understanding load paths. During the course of Optimization the density value continuously changes from 0 to 1 (normalized value). At the end of the last iteration each element would have retained some material density and this is based on the strain energy. Higher the strain energy density inside an element higher is the density value (say closer to 1). You can safely assume that elements with lower density values do not take much part in carrying the loads so elements with density values up to 0.3 or 0.4 can be discarded and the remaining elements with higher values carried forward for design fine tuning. To interpret designs better from a topology run you can use the DISCRETE parameter which pushes all semi dense elements closer to either 0 or 1. This results in a discrete design and avoids the guessing of what density value should be chosen for the Iso Value plot.

how do i use the discrete parameter what all values i should give ? i tried giving 0.8 but it doesn't change much. 

Thank you.