Usually one sided fillet welds should be avoided in areas that are subjected to fatigue loading. The reason for the poor fatigue behavior can be found in the additional bending moment due to the eccentricity between the mid plane of the attached sheet and the weld throat. In the case shown below, the rib would tilt to the left side when loaded by a vertical membrane force. The stresses at the root point of the weld might exceed in the nominal stresses in the sheet by one magnitude (factor 7 for A = t).
Obviously, it is important to include the effect of additional bending in one sided welds and in case of partial penetration welds. When the lateral movement of the rib is constrained by further structures, the effective eccentricity will be reduced or even removed. All these effects can be taken into account using LIMIT.