Displacement-Based Retrofit of Existing Reinforced Concrete Frames Using Alternative Steel Brace Systems

This paper presents an application of the displacement-based method for selecting suitable retrofit strategies for an RC frame building. An overview of different bracing technology is presented. By targeting the ultimate displacement depending on the failure mechanism of existing frames, a displacement-based retrofit of brace systems is implemented. A detailed seismic assessment (DSA) of a pre-1970 four-story RC case study frame is performed using SLaMA (Simple Lateral Mechanism Analysis) and Displacement-based assessment methods. The results indicate that the frame is classified as potentially earthquake-prone, showing joint shear failure mechanism with a seismic capacity of 46%NBS (New Building Standard). X-braced, V-braced (Chevron) concentric braces, and Buckling-Restrained braces (BRB) are used for retrofitting the building. After the retrofit, the failure mechanism of the frame is changed and the seismic capacity of the building exceeds 100%NBS. By evaluating the local and global behaviour of the retrofitted frames, the advantages and disadvantages of alternative braces systems are derived. The results indicate the feasibility and efficiency of Displacement-based retrofit design procedure for concrete frame buildings