Implementation of TRESCA yield certeria in ABAQUS plasticity material model using UMAT

hi everybody.

 I am interested to implement  tresca failure criteria in my plastic material model (ABAQUS/standard) using UMAT subrountine which is avaiable in ABAQUS code but it is primaryly made for Mises failure , so i made few attempt to modified it for tresca , but it did not work out, so if anyone have any idea , please guide me. 

thanks

prashant sharma