Pin-connected precast concrete structures are widely used in some European countries of moderate seismicity. However, this structural system is not earthquake resistant because it does not have enough lateral stiffness or lateral-load resistance. Lack of a rigid diaphragm at the roof level imposes severe forces to connections. It is difficult to strengthen such buildings with conventional strengthening techniques because buildings must be unoccupied before retrofitting, which building owners do not like. To overcome this difficulty, employment of external shear walls and a diaphragm at roof level are proposed in this study. A typical pin-connected precast concrete frame and a strengthened structure with the proposed method were tested under imposed, reversed, cyclic drift of constant rate. The experimental study showed that the proposed method increased lateral stiffness, lateral-load resistance, and seismic energy dissipation and provided a diaphragm effect for the structure
