A New Displacement‐based Design Procedure for the Retrofitting of RC Buildings with Steel Braces

Abstract

AbstractThis paper proposes a new displacement‐based methodology for the design of concentric steel‐brace retrofitting systems for RC framed buildings. It relies on deformation control for different levels of seismic intensity and explicitly considers the interaction between both structural systems. When dealing with the seismic assessment and strengthening of existing RC buildings, practitioners are likely to resort to the q‐factor approach, due to its simplicity and popularity for the design of new structures. However, in non‐seismically designed RC structures, the uncertainties associated to the nonlinear behaviour are relevant, making it therefore very difficult to define a direct correlation between the real internal forces that develop in structural members during the seismic excitation, and those experienced by an equivalent indefinitely elastic structure. Consequently, several authors have argued that the force‐based seismic assessment and retrofitting of existing RC structures will not yield, in general, satisfactory results. The design methodology proposed herein thus addresses this limitation, offering a solution which is intuitive and fit to be used in practical applications, while providing retrofitted structures with adequate and more predictable seismic performance.