An analytical investigation on the seismic retrofit of older medium-rise reinforced concrete shear walls under lateral loads

This paper describes an analytical investigation on the behavior and retrofit of older medium-rise monolithic cast-in-place reinforced concrete shear walls under lateral loads. A set of prototype and parametric walls is designed to represent building structures from the 1960s and early 1970s in regions of the US with high seismicity. Analytical models of the walls are constructed using a micro-plane fiber element that can capture axial–flexural–shear interaction in the nonlinear range. These models are then used to conduct nonlinear lateral load analyses to evaluate the following three wall retrofit methods recommended by ASCE 41-06: (1) reduction of flexural strength; (2) addition of concrete confinement; and (3) increased shear strength. The results show that older reinforced concrete shear walls are likely to exhibit limited lateral displacement capacity without retrofit or with the use of a single retrofit approach. A combination of different retrofit methods may be needed for improved behavior.