This paper describes the result of a shaking table test on high-aspect-ratio models of base-isolated buildings. We confirmed the influence of shear displacement upon axial stiffness in the test. Through our investigation of the development of a large axial force caused in connection with horizontal, vertical, and rocking vibrations, we found that careful attention to the influence of vertical vibration on the development of a large axial force is required. We developed a method for predicting additional axial forces produced by vertical vibrations. Predictions by this method were in good agreement with experimental results, confirming the validity of the method.