Retrofit Design Methodology for Substandard R.C. Buildings with Torsional Sensitivity

Recent earthquakes have revealed the susceptibility of non-ductile reinforced concrete (R.C.) buildings with deficiencies related to stiffness and/or mass irregularities in plan and elevation. This paper proposes a design methodology for the seismic upgrading of rotationally sensitive substandard R.C. buildings. The methodology aims to first eliminate the effect of torsional coupling on modal periods and shapes and then modify the lateral response shape of the building in each direction so as to achieve an optimum distribution of interstory drift along the building height. A case study is used to illustrate practical application of the proposed methodology.