Active earth pressure generate with springs

Hello everyone,
has somebody any idea how to generate the active earth pressure in Sofistik with using springs (linear, nonlinear, with using worklaws) behind the abutment of integral bridge which is caused by contraction? Generating the passive earth pressure behind the abutment which is caused by expansion is very simple. But in the contraction case I think this is rather impossible, because we get the forces in the springs, which will be acting in front of abutment not behind the abutment, but mayby I think wrong.