In this paper, we are introducing a design method concerned with the shifting of shear force between twin-tower buildings. The twin-tower buildings, a base isolation retrofit structure, had been originally built separately. One is rectangular shaped and the other is L-shaped. In this project, they are base isolated and joined at foundation level. Since the upper buildings are different shapes, they vibrate randomly. Consequantly, an enormous shear force will be caused at the connecting part. In this paper we discuss the process of the above mentioned design method that is used to solve the problem.
