This program has two broad objectives: (1) Develop and deploy advances in measurement science related to earthquake engineering - including performance-based tools, guidelines, and standards for designing buildings to resist earthquake effects and improve building safety, thus enhancing disaster resilience of buildings, infrastructure, and communities; and,(2) Perform the statutory Lead Agency duties for the National Earthquake Hazards Reduction Program (NEHRP). See reference 1.
What is the problem?
The problem is technical, programmatic, and societal, extending from widespread earthquake hazards and associated risks in the built environment to a lack of comprehensive, full-spectrum research, implementation, and outreach. The technical aspects of the problem result from the complexity and variability of the impacts of earthquake-induced ground motions on buildings and infrastructure. The programmatic aspects of the problem arise from the highly multi-disciplinary and multi-agency nature of addressing it. The societal challenge is large and growing, because damaging earthquakes occur so infrequently in human timescales that leaders and society-at-large tend to forget about the problem, leading to neglecting the need to address it.
Damaging earthquakes are infrequent; but, they come without warning, creating potentially catastrophic injury and loss of life, and damage to the built environment that creates significant economic loss and societal disruption. Earthquakes of magnitude 6.5 (M6.5) or greater are known to have occurred in Alaska, California, the Pacific Northwest, South Carolina, the Intermountain West, the Central U.S., and New England. While U.S. earthquake activity has been relatively quiet since the 1994 Northridge event, major 2010 and 2011 earthquakes in Chile, New Zealand, and Japan re-emphasized the potential impacts of such events, even in well-developed areas that are similar to the U.S. in terms of quality of the built environment.
A 2003 Earthquake Engineering Research Institute (EERI) report (reference 3) stated that a single large earthquake in a major U.S. urban area could easily cause combined direct and indirect economic losses between $100B and $200B (reference 4). The report noted that population growth and economic investment needed to sustain national quality of life, and increased societal interconnectedness associated primarily with increased urbanization, have led to placing greatly increased numbers of lives and extent of the built environment at risk. A recent study reported by the Seismological Society of America (reference 16) indicates that over 143 million Americans are exposed to potentially damaging earthquake, with as many as 28 million Americans likely to experience strong shaking in their lifetimes. This is a significant increase in the numbers of vulnerable Americans, as compared to earlier such reports, due primarily to population growth and urbanization.
The 2003 EERI report also explained that U.S. model building codes emphasize occupant life safety, with little consideration given to economic losses or recovery (i.e., resilience). This was an early recognition that earthquake preparedness should extend to providing local, state, and national earthquake resilience (reference 5).
The NEHRP agencies cast a vision of an earthquake-resilient nation in the NEHRP Strategic Plan (reference 6). The present Administration has recognized that national resilience in the face of risks from hazards is a vital challenge (reference 7). The National Research Council endorsed the NEHRP vision in its 2011 report (reference 8), stating that "A disaster-resilient nation is one in which its communities, through mitigation and pre-disaster preparation, develop the adaptive capacity to maintain important community functions and recover quickly when major disasters occur."
While earthquake-resistant design provisions for new buildings in U.S. model building codes have been improved, their focus has continued to be on occupant life safety using inflexible prescriptive design procedures. The typical code-compliant building may withstand the effects of moderate earthquakes but will likely be severely damaged when subjected to larger events, leading to costly repair work, or demolition and replacement, severely limiting societal resilience. The nation's existing building stock is more vulnerable to earthquake damage than newly designed buildings, posing higher societal risk, both in terms of life safety and resilience. Cost-effective seismic evaluation and mitigation methodologies for existing buildings are not widely available or applied.
As national leaders realize the need for improved resilience with respect to all hazards, the criticality of lifeline resilience in sustaining quality of life and economic strength will become more prominent. The nation's infrastructure is aging and, in many areas, deteriorating. Maintaining the serviceability of individual energy, communication, water, transportation, and waste lifeline systems is critical to societal resilience. Further, the interconnectedness of these separate (but not independent!) lifeline systems is a major factor in their serviceability and in societal resilience.
What is the technical idea?
NIST EL has two broad responsibilities within NEHRP that have been in place since 2006 when NIST was assigned the lead agency role.
First, EL fulfills statutory NEHRP Lead Agency responsibilities: supporting the NEHRP Interagency Coordinating Committee (ICC) and the Advisory Committee on Earthquake Hazards Reduction (ACEHR); drafting and updating NEHRP strategic and management plans; documenting NEHRP agency budgets; and submitting annual reports to Congress on NEHRP activities. Further to these responsibilities, NIST EL is faced with reenergizing the NEHRP program and the agencies to continue to work together despite the lack of Congressional action on a NEHRP reauthorization. The first steps include holding of an Interagency Coordinating Committee meeting during fall 2016 to chart a new course going forward for improved agency cooperation and coordination. With the change in presidential administration to occur in January 2017, effective engagement of senior agency leaders on an ongoing basis is of great importance to the program.
Second, through its NEHRP research program, NIST has developed broad technical goals for its earthquake risk mitigation research. The NEHRP agencies mutually developed the NEHRP Strategic Plan (reference 6) that outlines a coordinated NEHRP-wide approach to research and implementation based on a vision for a nation that is earthquake-resilient in public safety, economic strength, and national security. Approved by the ICC and reported to Congress, the Plan also established nine strategic priorities for the NEHRP agencies to pursue, depending on the availability of future resources. In 2011, the National Research Council (NRC) completed a NIST-commissioned study that produced a twenty-year “roadmap” for earthquake resilience research, implementation, and outreach (reference 8). The roadmap endorsed the NEHRP Strategic Plan and provided a comprehensive perspective that was developed by leading North American earthquake professionals.
EL research planning addresses NIST responsibilities outlined by the Strategic Plan and NRC roadmap. The responsibilities were outlined philosophically in the 2003 NIST earthquake R&D program plan provided by ATC 57 (reference 9). From 2006 through 2013, individual research projects followed the “ATC 57 roadmap philosophy” and satisfied needs that have been suggested by leading earthquake engineering practitioners and researchers in various national publications and validated through interactions with engineers who are actively developing national standards for seismic design, primarily ASCE/SEI 7 (reference 11).
EL subsequently commissioned the Building Seismic Safety Council (BSSC) to develop a ten-year research roadmap for recommended NIST-specific research that encompasses the ATC 57 philosophical goals, the NEHRP Strategic Plan, and the broad research directions set by the NRC study. BSSC released this roadmap report (reference 2) in early 2013. The 2013-2014 EL program began a transition to the recommended roadmap work and the proposed 2016 EL program continues this transition. Key features of the ongoing and proposed work are significant interactions with the partner NEHRP agencies, integrated analytical and experimental research, and continuing engagement with leading earthquake researchers and practitioners in the private sector and in academia, largely via its extramural Indefinite Delivery, Indefinite Quantity (IDIQ) contract with the Applied Technology Council (ATC). In addition, EL memberships in the BSSC Provisions Update Committee, the ASCE/SEI 7 Seismic Subcommittee, ASCE 41 Standard Committee, and corresponding ACI and AISC technical committees bring the latest technical ideas to the EL program.
To fulfill its NEHRP research responsibilities, NIST EL leverages the specialized expertise of a small number of in-house research structural engineers with the broader and deeper technical expertise available through its contractual relationship with the ATC. This permits EL to combine analytical and experimental efforts, consult with leading practicing engineers and researchers, and apply multi-disciplinary expertise to high-priority research needs. For example, recent and planned ATC task orders have addressed important geotechnical engineering needs of the NEHRP community that could not be addressed adequately by the in-house staff.
Significantly, all of these activities share the common thread of improved resilience. Earthquake resilience can be enhanced significantly by developing robust capabilities to predict and mitigate effects of earthquakes on building and lifeline systems and on communities-at-large. Resilience requires developing validated: (1) data to characterize the risk environment; (2) validated, rigorous models to predict performance of structures and lifelines to failure; (3) metrics for measuring performance, including interactions of building and lifeline systems; (4) acceptance criteria for different performance objectives (not only life safety); (5) mitigation strategies based on evaluated performance; and, (6) community-scale loss estimation tools.
What is the research plan?
Since 2006, the NEHRP agencies have jointly developed two broad planning documents: the NEHRP Strategic Plan (reference 6) and the NRC Roadmap (reference 8). The Plan outlines the NEHRP agencies' broad collective vision of the work needed to make the U.S. an earthquake-resilient nation. The Roadmap provides national expert recommendations on research, implementation, and outreach activities involving all NEHRP agencies that are needed to fulfill the vision for national earthquake resilience presented in the Strategic Plan.
I support of its role in fulfilling the NRC Roadmap, NIST commissioned the Building Seismic Safety Council (BSSC) to develop a roadmap of NIST research that will address the needs outlined in the NRC Roadmap. The BSSC Roadmap (reference 2) provides national expert consensus planning for NIST earthquake engineering research for buildings, for highest priority (to be accomplished in less than three years), higher priority (3-5 years), and high priority (5-8 years) needs. The planned 2016 program continues transitioning to significant reliance on the BSSC recommendations.
Paralleling the suggested BSSC approach, the program is subdivided into five complementary research program elements:
Program Element 1: Improved Building Codes and Standards Provisions;
Program Element 2: Performance-Based Seismic Engineering (PBSE) for New and Existing Buildings;
Program Element 3: Lateral Force-Resisting Structural Elements and Systems;
Program Element 4: Tools and Guidelines for Improved Earthquake Engineering Practice; and,
Program Element 5: National Earthquake Hazards Reduction Program (NEHRP) Coordination
Elements 1-4 address major technical areas of earthquake engineering research for improved design and construction of new and existing buildings. Program Element 5 supports the NEHRP Lead Agency role that is stipulated in PL 108-360 (NEHRP authorizing legislation). This program element is a recurring, non-research, requirement in the Program that is largely unchanged from year to year. The following is a brief discussion of FY 2017 research that is planned for each program element: Program Element (PE) 1 consists of short-term practical, applied research projects that improve seismic design practice, and building code and standard development. National model building codes contain prescriptive seismic provisions that have largely evolved from practitioner experience, without specific research results to substantiate them. This Program Element is devised to provide those research results.
Proposed 2017 PE 1 research includes an in-house project, Collapse Assessment of Buildings Under Seismic Loading, which is continuing and is an extension of an FY 2014-2015 project, Vertical Distribution of Lateral Forces and Approximate Fundamental Period. Lessons learned in the earlier work are being used to structure the new project, which will use nonlinear analysis approaches first promulgated in the FEMA P695 report, Quantification of Building Seismic Performance Factors, to correlate the building performance levels described in ASCE/SEI 7 with those described in ASCE/SEI 41. This is a vital step in equilibrating the design approaches that are used in prescriptive (ASCE/SEI 7 – reference 11) procedures with those used in performance-based seismic design (ASCE/SEI 41 – reference 14) procedures.
A second related PE 1 in-house project is entitled Seismic Performance of Wind Load-Controlled Steel Buildings in the Central and Eastern United States, which is a new project aimed at using the FEMA P695 evaluation methodology to examine buildings in the eastern two-thirds of the country where wind loads may control the design but seismic performance also must be ensured. The design of structures for wind assumes linear elastic response instead of the implied nonlinearity employed in seismic design. How these two different loading regimes interact in the design process has not been adequately evaluated in previous studies, where the focus has been on areas of high seismicity. A proposed in-house project under PE 2 is entitled Quantification of Material, Loading, and Modeling Uncertainties of Reinforced Concrete Columns and Steel Beam-Columns under Seismic and Gravity Loads for Use in Performance-
Based Earthquake Engineering (PBEE). The application of PBSE has provided a probabilistic framework to predict the response of the structural systems by incorporating the influences of various sources of uncertainty. While the effect of uncertainty in the applied loads on the performance assessments of structures is well established, the influences of material and modeling uncertainties have not yet been systematically integrated into PBSE. The proposed study will extend current work on steel structures to reinforced concrete columns under axial loading from gravity and lateral loading from earthquake ground motions. This project will conduct a comprehensive literature review on the previous studies conducted on the uncertainty quantification of the structural response and explore various research ideas on the field of uncertainty quantification for future consideration by the Earthquake Engineering Group at NIST.
An FY 2017 in-house project, Stability of Steel Wide-Flange Beam-Columns in Seismic Loading, is a continuation of research begun in 2014. The project will develop global and local buckling models and improved concepts of inelastic stability for axially-loaded deep, slender wide-flange steel sections, such as those used for lower-story columns in mid-rise buildings in seismically active areas. This work was identified as an area of major research need by an extramural panel of experts in NIST GCR 11-917-13 (reference 15). Extramural laboratory testing of 25 steel beam-column sections has been performed at the University of California, San Diego (UCSD), and 23 more tests will be conducted through a Phase II effort awarded under an FY 2015 task order. The laboratory test results have shown some unanticipated and potentially dangerous responses to seismic loading. The in-house research complements the UCSD testing with high fidelity finite element modeling to develop validated design relationships for the beamcolumns. The Phase II UCSD testing will extend into FY 2017, so this in-house project will extend into FY 2018, ultimately producing validated design guidance, including modeling techniques, for inclusion in ASCE and AISC seismic design standards.
A proposed FY 2017 PE 3 project, Performance of Ordinary Reinforced Concrete Columns Under Combined Gravity and Seismic Loading, was originally planned for FY 2015 award, but was delayed. This project seeks to improve the simulation and prediction of the shear and axial load-deformation response of ordinary RC columns in the PBSE framework. Reinforced concrete columns that do not meet the stringent reinforcement requirements for “special” columns as defined by ACI 318 (reference 16) are known as “ordinary” columns. “Ordinary” reinforced concrete columns are found in regions of low to moderate seismicity and are also typical of older structures that were designed under less robust design rules than those that exist today. The research will collect and review available experimental data as well as numerical models on the shear and axial load failure response of concrete columns, and utilize the information to improve their numerical modeling.
Program Element (PE) 4 develops synthesis documents, most of which are known as “techbriefs.” Techbriefs are short, succinct documents that distill research findings, findings of professional
committees and task groups, and cost-effective and code-compliant detailing practices into forms usable by practitioners. Techbriefs have been produced extramurally at the rate of one or two per year. In FY 2017 extramural work, two new techbriefs will be added to the growing series. The first TechBrief will explain present design provisions found in ASCE/SEI 7 to inform the design community about best practices and to provide important guidance to the community in application of the existing provisions.
The second TechBrief will address the application of probability and statistics to earthquake engineering analysis and design. This document will address underlying theoretical aspects of probability concepts as concerns hazard recurrence intervals and expected ground motions together with discussion of current load factors found within ASCE/SEI 7. Both of these topics have been identified by the engineering community as subjects that should be developed by NIST for this series.
Program Element (PE) 5, National Earthquake Hazards Reduction Program (NEHRP) Coordination, supports all activities of the NEHRP Office (“Secretariat”), which is organizationally located in EL. The Office performs all administrative and management activities to fulfill the NEHRP Lead Agency role - support for all activities of the ICC and ACEHR, interagency program coordination via the Program Coordination Working Group, required reporting (e.g., NEHRP Annual Report), and routine knowledge transfer activities (e.g., NEHRP web site). These administrative activities are ongoing each year and involve combined efforts of the in-house staff and an administrative support IDIQ. The Office also supports NIST’s role as lead agency for the U.S.-Japan Cooperative Program in Natural Resources (UJNR) Panel on Wind and Seismic Effects and the federal Interagency Committee on Seismic Safety in Construction (ICSSC). Current plans call for working with the Japanese to reform the UJNR partnership into a more modest and informal agency-to-agency relationship that leverages current electronic communications technology.
1. National Earthquake Hazards Reduction Program of 1977, as amended, http://www.nehrp.gov/about/PL108-360.htm.
2. Development of NIST Measurement Science R&D Roadmap: Earthquake Risk Reduction in Buildings, NIST GCR 13-917-23, 2013.
3. Earthquake Engineering Research Institute, Securing Society Against Catastrophic Earthquake Losses: A Research and Outreach Plan in Earthquake Engineering, January 2003.
4. The EERI report (reference 2) projected losses in terms of 2003 dollars. These costs are estimated to range between $125B and $250B in 2015.
5. In the context of this program, resilience may be thought of as the capability of a community to develop the adaptive capacity, through mitigation and pre-disaster preparation, to maintain important community functions and recover quickly when a major disaster occurs. Source: reference 6.
6. Strategic Plan for the National Earthquake Hazards Reduction Program, Fiscal Years 2009-2013, October 2008.
7. National Preparedness, Presidential Policy Directive/PPD-8, The White House, March 30, 2011.
8. National Research Council, National Earthquake Resilience: Research, Implementation, and Outreach, 2011.
9. Applied Technology Council, The Missing Piece: Improving Seismic Design and Construction Practices, ATC 57, 2003.
10. NEHRP Advisory Committee on Earthquake Hazards Reduction, Effectiveness of the National Earthquake Hazards Reduction Program, May 2008.
11. American Society of Civil Engineers, ASCE Standard, Minimum Design Loads for Buildings and Other Structures, ASCE/SEI 7-10, 2010.
12. A corporate partnership of the Applied Technology Council and the Consortium of Universities for Research in Earthquake Engineering.
13. Research Required to Support Full Implementation of Performance-Based Seismic Design, NIST GCR 09-917-2, NIST, 2009.
14. American Society of Civil Engineers, ASCE Standard, Seismic Rehabilitation of Existing Buildings, ASCE/SEI 41-06, 2007.
15. Research Plan for the Study of Seismic Behavior and Design of Deep, Slender Wide-Flange Structural Steel Beam-Column Members, NIST GCR 11-917-13.
16. Seismological Society of America news release, More Americans at risk from strong earthquake, says new report, http://www.seismosoc.org/society/press_releases/SSA_2015_EarthquakeThrea... .