In a soil-structure interaction (SSI) analysis in Abaqus, the maximum relative lateral deflection at each frame storey can be determined by defining a node set for each frame storey where you want to measure the lateral deflection. Then, create a history output request for each node set to output the lateral displacement (U2) of the nodes in that set and run the analysis and extract the results. Calculate the relative lateral deflection at each storey by subtracting the displacement of the node at the base of the structure from the displacement of the node at the desired storey. Determine the maximum relative lateral deflection at each storey by finding the maximum value of the relative lateral deflection calculated in step 4 for each node set.

However, it is not correct to subtract the lateral deflection at the base from the lateral deflection at each storey in a SSI analysis since the soil can deform and affect the base displacement. In a SSI analysis, the relative lateral deflection at each storey should be calculated with respect to a reference point, such as the center of the structure or the center of the base, that is not affected by the soil deformation.