The SAC-FEMA approach quantifies the seismic risk associated with structures in a simplistic way. Enhancements to the accuracy of this approach are presented in two stages. Firstly, improved intensity measure–engineering demand parameter relationships are established. Secondly, the application of this approach is extended to systems in which two different mechanisms could result in the attainment of the assessment limit state. The improved SAC/FEMA approach can be used by practitioners in daily design and assessment to quantify the likelihood of reaching key limit states. This could not only improve the communication between engineers and clients but also facilitates the decision making process for consultants to choose the most suitable structural system at an early stage of design and assessment.