Seismosoft | Earthquake Engineering Solutions

The D1-F1 direction of the Joint_B_Cen link element is fixed, i.e. the relative displacement D1 of the two nodes is zero (in fact it is 1e-15, due to round of errors in the PC computations). Hence the very small value of the F1 force (which again should be zero, but it is larger than zero, due to the round of errors). The horizontal load is
undertaken by the rotation of the RC joint.
Have a look at the action effects diagrams for the shear and the axial frame element forces.
Regards,
Seismosoft Support