Magnetorheological (MR) damper is one of the most promising semi-active control devices for mitigating seismic response, and so, it has received significant attention in recent years. Because of the inherent nonlinear nature of MR damper devices, one challenge to effectively utilize this technology is the development of an appropriate control algorithm. A semi-active control methodology is presented to control structural systems using MR dampers that addresses structural modeling uncertainties. Based on the same idea as the clipped-optimal linear controller, the proposed semi-active control law uses a robust reliability-based active linear control methodology to calculate the reference control forces that the MR dampers attempt to produce approximately. These reference control forces can be calculated using incomplete response measurements at the current and/or previous time steps without any state estimation. The main purpose of the proposed approach is to achieve a more robust performance for uncertain structural systems subjected to uncertain strong-motion excitation. The performance of the proposed approach is demonstrated through a simulated example of a ten-story building with MR dampers installed.