Dear Masih,
Please see my post dated Mar 05, 2014 in the following forum topic where I provide an example of a wind file with wind-speed steps: Beginner Guide for MATLAB Simulink and FAST - #12 by Jason.Jonkman. Please note that what were formerly called AeroDyn “hub-height” wind files are called “uniform wind files” in the InflowWind module of FAST v8 and OpenFAST.
Best regards,