Recent guidelines from AASHTO have shifted seismic bridge design from uniform hazard spectrum to a risk-targeted ground motion approach. This shift will result in more uniform reliability of bridges designed to resist seismic ground motions across the U.S. TRB hosted a webinar on Wednesday, May 17, 2023 from 12:00 PM to 1:00 PM Eastern that shared the development and basis for the recently adopted risk-targeted approach. Presenters shared the differences between uniform hazard and risk-targeted ground motions and how to apply the new risk-targeted ground motions within the AASHTO specifications.

This webinar is based on NCHRP Research Report 949: Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design.

This webinar was sponsored by TRB’s National Cooperative Highway Research Program and the Standing Technical Committee on Seismic Design and Performance of Bridges.

The slides are linked in the meeting materials. View the recorded webinar below.

Webinar agenda and presenters

1. Overview and implementation within the AASHTO specifications – Thomas Murphy, Modjeski and Masters, Inc.

2. Calculation of risk-targeted motions – Lee Marsh, WSP

3. Question and answer session moderated by Ian Buckle, University of Nevada, Reno

The first 40 minutes of the webinar were for presentations and the final 20 minutes were reserved for audience questions.

Learning Objectives

At the end of this webinar, participants are able to:

1. Differentiate between risk-targets and uniform hazards ground motions

2. Apply the risk-targets ground motions within the AASHTO specifications

Professional Development Hours

This webinar was delivered as a scheduled – e-learning live event and is categorized within RCEP as Technical, Health and Safety.

Professional Development Hours (PDHs) earned on completion of this program were reported to the Registered Continuing Education Program (RCEP). Certificates of Completion are issued to all participants via the RCEP.net online system. Complaints about registered providers may be addressed to RCEP, 1015 15th Street, NW, 8th Fl., Washington, DC, 20005.