The counterforce frame was systematically designed and optimized, aiming to improve its current disadvantages of small stiffness, unreasonable structures, and excessive material consumption, etc. By adopting SOLIDWORKS, the 3D models of four different kinds of counterforce frame structures were established, upon which static analysis were then conducted by ANSYS and ABAQUS. The magnitude and distribution of their stiffnesses and strengths were obtained, and after comparing the steel consumptions and mechanical properties, the style of fish-bell sill was chosen to be further optimized. As for the fish-belly sill counterforce frame, its inherent frequency and vibration modes were obtained through the modal analysis in ANSYS. The first vertical vibration took place at the frequency of 25.6Hz, satisfying the requirement that the 10Hz actuator loading could not trigger resonance. Afterwards, the transient analysis could provide the vibration response of this specific counterforce frame, when tested with the 10Hz actuator. The displacement peaked at 1.128mm, and then stabilized at 0.72mm after 5 seconds, which met the requirements of both dynamic loading accuracy and counterforce frame stiffness. In sum, the results showed that the fish-belly sill structure could offer the most stiffness compared with the other three, which was large enough to meet the dynamic loading stiffness requirement, and in the meantime was the most economical with the least steel consumption.
