MSC NASTRAN Beam Element

Dear All,

I am wondering about beam element in MSC NASTRAN.

How can a linear distribution of translation or rotation along a beam element produce a linear distribution of moment and constant shear force in a case of single tip force loading?  

What kind of beam element or beam theory used? I am not sure it is Timoshenko beam theory (which produce constant moment and linear shear force distribution)

I thank you in advance.

Best regards,

Sugeng