Tsai-Wu failure criteria Timber beam ANSYS

I am a PhD student on Timber structure.I have modelled timber beam using solid 45 element as 4 points bending but my result is overestimated.I have reviewed the literature and I have found that assigning Tsai_Wu failure mode in timber can solve the problem.I have found Tsai-Wu in following category in Ansys 12.1:Material model/nonlinear/inelastic/non metal plasticity/failure criteria/criteria3But Ansys appears the following error:*** ERROR ***