By Roy Lobo, Ph.D., S.E., SEAOC Seismology Chair
The SEAOC Seismology Committee develops, updates, and maintains the Association's publication “Recommended Lateral Force Requirements and Commentary” (SEAOC Blue Book) and reviews the SEAOC Seismic Design Manuals. The Committee also provides seismic code change proposals to the International Building Code developed through the local and state Seismology committees.
Currently the committee is focusing its efforts in a number of directions. The 2015 NEHRP provisions are out and SEAOC Seismology was actively involved in the balloting process. These provisions are now published and available as a two volume document, FEMA P-1050. The first volume has two parts, Part 1 Provisions and Part 2 Commentary (FEMA P-1050-1). The second volume is Part 3, Resource Papers (FEMA P-1050-2). These provisions include a number of new ideas that if adopted could chart the future of our profession. Some of the areas where significant changes are being proposed include:
1) Better quantifying the response modification coefficient used in the design of building structures with the methodology outlined in FEMA P695. This will be done by evaluating building performance based upon nonlinear response history analysis incorporating full scale cyclic test results of Seismic Force Resisting System elements and/or actual building performance in past earthquakes.
2) Alignment of seismic performance objectives to ensure fewer than 1% collapses in 50 years for Risk Category II buildings.
3) Changes to the diaphragm design forces. These changes have also been adopted in ASCE 7-16 for precast concrete structures. Buildings with precast concrete will now be required to have their diaphragm and their connections designed for a much higher demand. This procedure has also been adopted as an alternative for other structures.
4) Changes to the new ground motions. New maps will show an increase in the short period response and a modest decrease at the one second period.
5) Many changes are proposed for lateral force resisting systems utilizing energy dissipation and/or isolation bearing devices for buildings, such as base isolated buildings and viscous or friction damped frame buildings.
6) Modifications to the requirements for design on liquefiable soils.
7) Soil structure interaction.
The goal is to improve our analysis and design of structures using current computer modeling capabilities with simplified assumptions to achieve the necessary level of safety to protect lives and limit property damage. Depending on the magnitude of the ground shaking at the site, the intent is to keep lives safe at all costs and limit damage to where the structure may be repaired given a moderate earthquake and does not collapse in a maximum credible earthquake.
The Seismology Committee is also currently charged with updating Volume 1 of the Seismic Design Manual to the 2015 IBC. The revisions will not only focus on code updates, but each problem will be evaluated with the intent to revise any critical issues with the problem. These manuals should not be considered a “template” design procedure, but as a practical guide for up-and-coming structural engineers.
The Seismology Committee provides a forum for vetting new ideas for code changes and challenging existing ones. Issues and research needs identified during the development of the 2015 NEHRP recommended provisions for new buildings and other structures have been categorized into two groups: “Future Provisions Issues” and “Research Needs” including all major building construction materials and analysis and design procedures. The local Seismology Committee chairs are actively seeking volunteers to get on the Building Seismic Safety Council (BSSC) issue teams to help advance the state of earthquake resistant design. They have also had experts and researchers to update their committee members on the latest development in earthquake engineering. There have been presentations on a variety of topics such as building ratings using the developed SP3 software as an extension of the ATC-58 and the PACT software, waste water injection and hydraulic fracking, lessons from the NAPA earthquake, shake table testing results for low-cost & base isolated residential buildings, Shakecast, pseudo-dynamic cyclic testing criteria for vibration isolators for non-structural components, structural sealant glazing, point supported glass, and proposed criteria for seismic certification of non-structural components.
If any of these areas interest you, NOW is the time to get actively involved in the SEAOC Seismology Committee. This is the way to have a voice to make the necessary impact at the national level. The strength of an organization is primarily achieved with active participation from its membership. The Seismology Committee executes the mission of SEAOC which is to seek to advance the state-of-the-art and the state-of-the-practice in structural engineering; to provide the public with structures of safe and dependable performance; to give the structural engineering profession the most current information and tools for structural analysis, design, and detailing and for effective business management. The SEAOC Seismology Committee serves as a respected, leading, and proactive voice in structural code and standard development. To learn more about joining the Committee, contact email@example.com.