How to apply uniformly distributed load to shell element when I do nonlinear analysis of I-BEAM

Hi, everyone:

I am using ABAQUS to do my final dissertation:nonlinear analysis of steel members.

I want to apply UNIFORMLY DISTRIBUTED LOAD to the middle height of the web, I splited the web into top and bottom parts,but nomatter I use 'LINE LOAD' OR 'SHELL edge LOAD' ,it does not work at all.

Thank you so much in advance, any opinion is welcome.