RC frame structures with masonry infill walls represent a typical building topology in Pakistan and many countries worldwide. Burnt brick walls are commonly used in buildings as partitions and external walls. Practicing engineers often employ code-based procedures for the structural design of buildings and ignore the effects of infills, considering them as non-structural components. However, these infill walls contribute to the early strength, initial stiffness, and energy dissipation capacity of the frames and thus can considerably modify the global seismic performance of buildings. This contribution can be captured using nonlinear structural models. However, in the conventional code-based design procedures (based on linear elastic modeling), the infills are generally not included in the analysis model. This study presents a simplified displacement-based design (SDBD) procedure based on the concept of equivalent linearization to overcome this issue. The SDBD procedure uses the framework of the direct displacement-based design (DDBD) method to determine the equivalent linear characteristics of the nonlinear structure. The fundamental idea is that the seismic demands of a nonlinear system can be determined using an equivalent linear system of elongated period and higher damping. The proposed procedure is developed using the three case study buildings (3-, 4-, and 5-story high), and its accuracy is investigated for a 5-story high building under input ground motions. In this evaluation, the inelastic demands obtained from the nonlinear analysis procedure are employed as a benchmark. The proposed SDBD procedure is found to provide accurate estimations of local and global responses for the case study building.