The Earthquake Risk Reduction in Buildings and Infrastructure Program has the following dual mission: (1) to 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) to perform the statutory lead agency duties for the National Earthquake Hazards Reduction Program (NEHRP). The Earthquake Risk Reduction program accomplishes this with a staff of seven engineers, one social scientist, and one program manager/analyst. A portion of the time of two engineer’s and all of the program manager/analyst’s time is dedicated to the NEHRP lead agency responsibility. The budget for the Earthquake Engineering Group is $4.15 million per year, with an additional $1 million per year dedicated to the NERHP lead agency role. The program is also jointly budgeted with the National Science Foundation (NSF) to administer $3.1 million in disaster research grants.
All engineers and the social scientist hold Ph.D.’s. Postdoctoral experience ranges from 3 years to more than 30 years. The group’s median experience level is 8.5 years, and the average is 12.5 years. One engineer and the social scientist are female. Collectively, the group has published more than 30 invited and/or refereed papers on their areas of research. One staff member was awarded the Housner Grant by the Earthquake Engineering Research Institute. This award recognizes promising and motivated early- to mid-career professionals with the confidence, skills, and sense of responsibility needed to exercise leadership by developing fellows’ capacity for advocacy and leading efforts to reduce earthquake risk.
Since the mid-1990s, a major thrust of the NEHRP agencies (NIST, the Federal Emergency Management Agency [FEMA], NSF, and the U.S. Geological Survey [USGS]) has been the development and advancement of performance-based seismic design and implementation of this methodology in the improvement of the nation’s building codes and standards, and thereby, the nation’s earthquake resilience. NIST sought public input and guidance on the most important and appropriate research thrusts to support this goal, as published in the ATC-57 report.1 Earthquake research thrusts are drawn from the tasks identified in that report and include improving performance-based seismic evaluation and design procedures and identifying economical and effective earthquake-resistant systems. A final thrust area is as the lead NEHRP agency.
The Earthquake Engineering Group’s research includes analytical and experimental studies performed with both intramural and extramural resources. When initially tasked with the NEHRP lead agency role, the Earthquake Engineering Group relied heavily on external resources through a contract with the NEHRP Consultants Joint Venture and individual universities. Increasingly, the group has been shifting to a mode of self-reliance in which most research is performed using internal resources and capabilities. Together with the Structures and Materials group, the Earthquake Engineering Group has recently commissioned the Performance-based Engineering Research for Multi-hazards (PERFORM) Structural Testbed.
1 Applied Technology Council, 2003, The Missing Piece: Improving Seismic Design and Construction Practices, Redwood City, CA.
TECHNICAL MERIT OF THE PROGRAM
Improving Performance-Based Seismic Design Procedures
The earthquake engineering community developed a first-generation performance-based seismic evaluation and design (PBD) methodology in the mid-1990s, under the ATC-332 project. The American Society of Civil Engineers (ASCE) standardized this methodology in its ASCE 41 publication.3 ASCE 41-17 has been adopted by the nation’s building codes and has become the primary means by which civil and structural engineers assess probable building performance in earthquakes and by which engineers design seismic retrofits of buildings to improve their performance. This standard is also used as the basis of seismic design for some new buildings with enhanced performance objectives. As identified in the ATC-57 report, the reliability of this methodology has not been ascertained or verified, calling into question whether the substantial investment currently made in hardening the nation’s building stock for earthquake resistance is either necessary or adequate. Some years ago, NIST undertook an evaluation of selected buildings designed to the then-current building code using the ASCE 41 procedures. Using the ASCE 41 procedures, NIST determined that these code-conforming buildings could not meet the life-safety protection goals of the code. This indicated either that the building code was not adequate to provide building designs capable of meeting its stated goals or that the ASCE 41 procedures were excessively conservative in assessing building performance. Given that the FEMA P-695 study4 characterized and verified the reliability of the code provisions, the inadequacy of the ASCE 41 procedures was apparent.
An important thrust of the Earthquake Engineering Group’s programs since that time has been to improve the PBD procedures. Research tasks undertaken in support of this goal include verification of the collapse reliability of steel frame buildings; collapse performance modeling of non-ductile concrete columns; quantification of material, loading, and modeling uncertainties; and development of improved assessment criteria for performance-based seismic design.
Identification of the excessive conservatism inherent in the ASCE 41 performance assessment methodology is a significant and important accomplishment. Supported research has identified potential reductions in this conservatism through use of improved loading protocols in experimental investigations to predict element performance characteristics. Substantial NIST-supported work in this area was published under the ATC-1145 series of documents. Earthquake Engineering Group staff have been instrumental in moving recommendations from these studies into pending updates of the ASCE 41 and related standards developed by materials industry associations.
2 Applied Technology Council, 1997, NEHRP Guidelines for Seismic Evaluation of Existing Buildings, Report No. FEMA 273, Federal Emergency Management Agency, Washington, DC.
3 American Society of Civil Engineers, 2017, Seismic Evaluation and Rehabilitation of Buildings, ASCE 41-7, Reston, VA.
4 Federal Emergency Management Agency, 2009, FEMA P695 Recommended Methodology for Quantification of Building System Performance and Response Parameters, Project ATC-63, Applied Technology Council, Redwood City, CA.
5 Applied Technology Council, 2017, Recommended Modeling Parameters and Acceptance Criteria for Nonlinear Analysis in Support of Seismic Evaluation, Retrofit and Design, NIST Report No GCR-17-917-45, National Institute of Standards and Technology, Gaithersburg, MD.
Challenges and Opportunities
Massive effort is needed to improve the nation’s seismic performance assessment procedures. The procedures embodied in the ASCE 41 standard are based on more than 40 years of research conducted at universities throughout the United States, Europe, and Asia during the last half of the 20th century. The Earthquake Engineering Group’s studies identify that this research was excessively conservative in characterization of structural performance. Extensive analytical and experimental work is needed to update these studies using more appropriate procedures. To date, NIST has been able to perform such studies on steel moment-resisting frame and nonductile concrete structures. These are only two of more than 20 structural systems represented in the nation’s building inventory. Substantial additional work is needed to fully improve and enhance the PBD procedures embodied in ASCE 41 in their entirety. Successful accomplishment of this work will allow better assessment of the nation’s existing earthquake risk, identification of those buildings that are highest priority for mitigation, and more economical use of available resources to improve the nation’s earthquake resiliency.
While NIST has focused on improvement of present-generation procedures, its partnering NEHRP agency, FEMA, has moved forward with development of next-generation PBD procedures6 that characterize building performance directly in terms of the probable economic, human, and environmental impacts of building damage, while inherently considering the uncertainties associated with such characterization. The Earthquake Engineering Group’s advanced capabilities in structural reliability analysis and characterization of uncertainties, as well as their broad connection with the earthquake community as lead NEHRP agency, places the group in a unique position to advance the development and effectiveness of this methodology.
Identifying Effective Earthquake-Resistant Systems
Engineers traditionally provided earthquake protection through design of robust systems with substantial strength and stiffness. These robust structural systems are expensive to build or retrofit into existing structures, embody substantial carbon, and deliver substantial seismic forces and displacements to supported nonstructural components, systems, and contents. Development of more elegant structural systems, for both new structures and retrofit of existing structures, will make provision of seismic protection more affordable, more practical to attain, and more sustainable. Research tasks undertaken in support of this goal include the following: developing cost effective relationships between building characteristics and seismic retrofit costs and benefits; earthquake risk reduction in buildings and infrastructure; seismic performance of steel buildings in the central and eastern United States; reliability of fiber-reinforced composite systems in resilient infrastructure; advancing the seismic implementation of high-strength reinforcing bars in concrete walls; seismic assessment of pre-Northridge earthquake weak panel zones and welded column splices; and improving earthquake re-occupancy and functional recovery.
This is a developing research area. Work accomplished to date includes development of research plans for specific studies and initiation of a process to solicit proposals for a new extramural Indefinite Delivery Indefinite Quantity (IDIQ) contractor that will assist with the work in many of these tasks.
6 Applied Technology Council, 2012, FEMA P58: Next-Generation Building Seismic Performance Assessment Methodology, Report No. FEMA P-58, Federal Emergency Management Agency, Washington DC.
Challenges and Opportunities
This is an important research area. Successful development of cost effective and practical systems to provide robust design solutions and resilient structures is necessary to make earthquake resilience an attainable goal. Much work needs to be done to move forward with the research tasks in this area. Japan has extensive experience in designing sophisticated earthquake resistant buildings where they design in-force absorption for the earthquake-induced motion. Collaboration with their laboratories or agencies is likely to be informative.
Lead NEHRP Agency
Intense earthquakes are an infrequent but high-consequence phenomenon. Traditionally, U.S. and international building codes have sought to accept damage in these rare events but avoid massive life loss by permitting design of structures that are anticipated to withstand substantial, but not complete, damage in such events. The massive damage suffered by New Orleans from Hurricane Katrina and Christchurch, New Zealand, following the 2010-2011 earthquakes there, and the long recovery times that have ensued in both cities, have challenged this life safety paradigm and suggested that it is not sufficient. Society now demands the development of resilient communities that can remain viable following such major events. However, it is not clear how best to go about revising community development practices to accomplish this goal. As part of its reauthorization of the National Earthquake Hazard Recovery Program, Congress charged NIST with development of a report to Congress on how to develop a framework for building practices to achieve community resiliency. In addition to this task, NIST serves as the coordinating NEHRP agency partnering with FEMA, NSF, and USGS in assuring that building practices for federal buildings are sufficiently resilient and that the nation’s building codes and standards are appropriate to achieving this goal.
NIST successfully produced a final report to Congress on Research Needs to Support Establishment of an Immediate Occupancy Performance Objective Following Natural Hazard Evenys.7 NIST also completed a draft report to Congress on Recommended Options for Improving the Built Environment for Post-Earthquake Re-Occupancy and Functional Recovery Time.8 In addition, NIST worked with the National Security Council and the Office of Scientific and Technology Policy (OSTP) to help draft Executive Order 13717 Establishing a Federal Earthquake Risk Management Standard in February 2016, and NIST drafted the implementation guidelines for federal agencies concerning EO13717 and has revised the Standards of Seismic Safety for Existing Federally Owned and Leased Buildings (RP-10).9 NIST also acted as the secretariat for the Advisory Committee on Earthquake Hazard Reduction, an advisory committee to the President of the United States on earthquake policy issues.
7 NIST. Available at https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.1224.pdf
9NIST. Available at https://www.gsa.gov/cdnstatic/ICSSC_RP8_December_2011_508c.pdf
Challenges and Opportunities
The responsibility to serve as lead NEHRP agency is not itself a research activity. While serving in this capacity provides resources to the Engineering Laboratory that it might otherwise not realize, the secretariat duties can detract from the other thrust areas by drawing both personnel and resources.
PORTFOLIO OF SCIENTIFIC EXPERTISE
The Earthquake Engineering Group includes one senior, two mid-career, and several early-career researchers. All hold doctoral degrees and three hold professional engineering licensure. One has 10 years of engineering practice. As evidenced by their publications, the group has a wealth of analytical research expertise and knowledge of structural reliability principals. The group lead, who held senior positions with the Network for Earthquake Engineering Simulation (NEES) Consortium and NSF, has some laboratory research experience. One of the research engineers also has some laboratory research experience.
Challenges and Opportunities
The PERFORM testbed provides the Earthquake Engineering Group with an important tool to conduct intermural laboratory experimentation into structural behavior. It appears however, that the group is lacking in experience in performance of large and complex physical tests. This may limit the group’s ability to take advantage of this important capability.
ADEQUACY OF RESOURCES
Together with the Structure’s Group, the Earthquake Engineering Group has successfully commissioned the PERFORM Structural Testbed. PERFORM provides the capability to dynamically, and quasi-statically test large structural assemblies under complex loading conditions with peak structural loading of 220,000 pounds. Comparable capability at U.S. universities include a 1 million pound machine at the University of California, Berkeley, a 2.4 million pound machine at the University of Washington, a 2 million pound machine at Lehigh University’s Advanced Technology for Large Structural Systems (ATLSS) Center, and similar large testbeds at Purdue University, the University of Michigan, Ann Arbor, the University of California, San Diego, and the University of Illinois, Urbana-Champaign, among others. The PERFORM testbed does have enhanced flexibility to accommodate unusual structural geometries and systems.
Challenges and Opportunities
The capacity to perform large-scale structural tests in-house provides the Earthquake Engineering Group with the ability to perform independent study of the earthquake resistance of a wide variety of structural components and systems. The challenge to the group will be to demonstrate an ability to perform such tests competitively with the many comparable research laboratories at major U.S. universities.
EFFECTIVENESS OF DISSEMINATION OF OUTPUTS
The Earthquake Engineering Group disseminates its work through a variety of resources, including publication of TechBrief and technical reports, publication of journal and conference papers, seminars for professional organizations, and direct support and participation in the standards development process. During the period 2008-2017, NIST developed, through its extramural IDIQ consultant, a series of 13 TechBriefs on design of structural systems for seismic resistance. The TechBriefs, prepared by leading authorities on each structural system, are readily available for download from the NIST and NEHRP consultants websites and are widely referenced by practicing engineers in the course of design work.
During this same period of time, NIST produced through the same extramural consultant a series of eight technical reports covering such topics as the following: program plans for assessing collapse risk assessment of concrete buildings; evaluation of the FEMA P695 Methodology for assessing seismic performance factors, applicability of multi-degrees-of-freedom analysis in design, selecting and scaling earthquake ground motions for use in design and analysis, a research plan for exploring the seismic capacity of deep wide flange steel columns, a comparison of U.S. and Chilean building codes, soil-structure interaction for building structures, and use of high-strength reinforcement in steel columns. The reports on soil-structure interaction and use of high-strength reinforcing steel in concrete structures have directly supported recent updates to the ACI 318 and ASCE 7 standards. Research conducted on deep, wide-flange steel columns have contributed directly to updates of the American Institute of Steel Construction (AISC) standards and also the ASCE 41 standard for seismic rehabilitation and evaluation.
Several Earthquake Engineering Group researchers are active participants in industry committees that develop the nation’s design and construction standards. These include the AISC Committee on Specifications and the ASCE committees on Seismic Rehabilitation and Minimum Design Loads and Associated Criteria for Buildings and Other Structures. A member of the Earthquake Engineering Group led an effort at the AISC Specifications Committee to develop a new standard, AISC 342, which will provide nonlinear seismic analysis of structures useful both for evaluation and retrofit of existing buildings and design of new buildings.
Challenges and Opportunities
Growing societal interest in resilient communities presents the need for creation of new design, analysis, and construction standards to meet this challenge. The Earthquake Engineering Group is ideally suited to direct as well as self-perform the needed research to enable development of these standards.
Much of the substantial work performed by the group over the past 10 years has been accomplished through the extramural contract with the NEHRP Consultants Joint Venture. This consultant established uniquely qualified teams, comprising domestic and international experts from practice and academia, to execute specific assignments. Expiration of the IDIQ contract under which this work was performed compromises the group’s capability to perform similar high-quality studies. To the extent that the Earthquake Engineering Group elects to self-perform these research tasks, it will need to increase its internal staffing levels. To the extent such studies are self-performed, it will be important to have formal mechanisms for obtaining external review and input so that the work does not become excessively insular.
CONCLUSIONS AND RECOMMENDATIONS
Technical Merit of the Program
The Earthquake Engineering Group’s studies have found that that procedures embodied in the ASCE 41 were excessively conservative in the characterization of structural performance.
RECOMMENDATION: The Earthquake Engineering Group should broaden its work with steel frame and concrete wall structures to encompass the many other common buildings systems.
RECOMMENDATION: The Earthquake Engineering Group should work to establish next-generation loading protocols and/or adaptive hysteretic modeling approaches that will enable reduction in the inherent conservative bias in present performance-based design procedures.
Portfolio of Expertise
The Earthquake Engineering Group includes one senior, two mid-career, and several early-career researchers. The PERFORM testbed provides the Earthquake Engineering Group with an important tool to conduct intermural laboratory experimentation into structural behavior. It appears, however, that the group is lacking in experience in performance of large and complex physical tests. This may limit the group’s ability to take advantage of this important capability.
RECOMMENDATION: The Earthquake Engineering Group should seek to broaden its capability with mid- or senior-level researchers with extensive structural laboratory expertise in order to take full advantage of the Performance-based Engineering Research for Multi-hazards (PERFORM) testbed now available.
RECOMMENDATION: The Earthquake Engineering Group should establish an external peer review process composed of leading researchers and practicing engineers to provide input on the specific research tasks undertaken and the details of significant research programs.
RECOMMENDATION: The Earthquake Engineering Group should establish formal procedures to assure interaction with practicing professionals and researchers at other institutions to assure that the program does not become overly insular.
Effectiveness of Dissemination of Outputs
An important thrust of the group’s programs has been to improve the performance-based seismic evaluation of design (PBD) procedures.
RECOMMENDATION: As lead National Earthquake Hazards Reduction Program agency, the Earthquake Engineering Group should partner with the Federal Emergency Management Agency and NIST to improve and implement the FEMA P-58 methodology in industry design guidelines and standards.
RECOMMENDATION: The Earthquake Engineering Group should partner with private industry to develop new cost-effective, damage-resistant, and damage-tolerant structural systems.