Some buildings constructed in the US prior to the implementation of the special details for ductile response may pose a collapse risk under strong earthquake ground shaking.  Major advances in understanding seismic response of older hazardous concrete buildings, leading to engineering criteria for building assessment and retrofit, as well as advanced dynamic simulation capabilities.

Many seismic retrofit (or rehabilitation) strategies have been developed in the past few decades following the introduction of new seismic provisions and the availability of advanced materials (e.g. fiber-reinforced polymers, FRP, fiber reinforced concrete and high strength steel) Retrofit strategies are different from retrofit techniques, where the former is the basic approach to achieve an overall retrofit performance objective, such as increasing strength, increasing deformability, reducing deformation demands while the latter is the technical methods to achieve that strategy, for example FRP jacketing.