Seismic retrofit of a reinforced concrete flat-slab structure: Part I — seismic performance evaluation

An evaluation of seismic performance was conducted for a reinforced concrete (RC) frame structure representative of 1980s construction in the Central United States. The case study building is a five-story RC flat-slab office building designed for the code requirements used in this region. The structural response was predicted using nonlinear static analysis and nonlinear dynamic analysis with synthetic ground motion records. The FEMA 356 criteria were used to evaluate the seismic performance of the case study structure. Because the case study building does not meet the FEMA 356 basic safety objectives for the Memphis motions, three seismic retrofit techniques were applied to enhance the seismic performance including the addition of shear walls, the addition of RC column jackets, and confinement of the column plastic hinge regions using externally bonded steel plates. Finally, the predicted seismic performance for the three retrofitted structures was compared to that for the unretrofitted structure. Varying levels of improvement in the seismic performance were demonstrated through the use of the selected seismic retrofits. Based on the seismic evaluation with the FEMA 356 criteria, the addition of shear walls provided the greatest improvement in the seismic performance of the case study building.