ABSTRACT

Recent earthquakes in urban areas have repeatedly demonstrated the vulnerability of older structures to seismic deformation, not only the traditional ones but also those made with reinforced concrete materials, with deficient shear strength, low flexural ductility, and insufficient lap splice length of the longitudinal bars. Very often, these structures also have inadequate seismic detailing, and, in many cases, very bad original design, with insufficient flexural capacity. The most critical mode of failure in RC structures is column shear failure. To prevent this brittle failure, the columns need to have guaranteed shear capacity both at their ends, in potential plastic hinge regions, where concrete shear capacity can degrade with increasing ductility demands and in the column center portion, between flexural plastic and/or existing built-in column hinges.