Risk-Targeted Ground Motions and Their Implications for Bridge Design in the CEUS

Presented By: Lee Marsh, WSP USA Inc Description: In 2022 AASHTO adopted risk-targeted ground motions (RTGMs) to replace the long-standing 1000-year return period hazard-based ground motions. The RTGMs address a long-standing short-coming of the 1000-year uniform hazard ground motions because the earthquake demands based on hazard alone can underestimate the shaking that can occur with earthquakes that have historically occured in the CEUS. RTGMs help address this by looking not only at hazard (what the ground alone can produce), but also the likelihood of significant damage or collapse of bridges in the face of the actual earthquake hazard present in the CEUS.