Tenth U.S. National Conference on Earthquake EngineeringFrontiers of Earthquake Engineering July 21-25, 2014 Anchorage, Alaska 10NCEE

FEMA P-58 PHASE 2 – DEVELOPMENT OF

PERFORMANCE-BASED SEISMIC DESIGN CRITERIA

J. A. Heintz1, R.O. Hamburger2, and M. Mahoney3

ABSTRACT In 2012, the Applied Technology Council (ATC) completed a 10-year program under contract with the Federal Emergency Management Agency (FEMA) to develop a next-generation methodology for seismic performance assessment of buildings. Collectively referred to as FEMA P-58, Seismic Performance Assessment of Buildings, Methodology and Implementation, the resulting products describe a general methodology and recommended procedures to assess the probable seismic performance of individual buildings based on their unique site, structural, nonstructural, and occupancy characteristics. Recently, FEMA funded a subsequent phase of work to utilize the performance assessment methodology in benchmarking the performance of U.S. model codes and seismic design standards, and developing performance-based seismic design criteria. In this methodology, seismic performance is characterized on a probabilistic basis in terms of the potential for incurring damage or losses in the form of repair costs, repair time, casualties, unsafe placarding, and environmental impacts. Seismic design objectives under consideration include protection of life, limitation of repair costs and repair time, and functional performance, as measured by FEMA P-58 procedures and performance metrics. This paper presents the initial findings and directions of the new 5-year program for development of performance-based seismic design criteria.

1 Applied Technology Council, 201 Redwood Shores Parkway, Suite 240, Redwood City, CA 94065 2 Simpson Gumpertz & Heger, 100 Pine Street, Suite 1600, San Francisco, CA 94111 3 Federal Emergency Management Agency, 500 C Street SW, Washington, D.C. 20472 Heintz, J.A., Hamburger, R.O., and Mahoney, M. FEMA P-58, Phase 2 – Development of Performance-Based Seismic Design Criteria. Proceedings of the 10th National Conference in Earthquake Engineering, Earthquake Engineering Research Institute, Anchorage, AK, 2014.

FEMA P-58

Phase 2 – Development of Performance-Based Seismic Design Criteria

J. A. Heintz1, R.O. Hamburger2, and M. Mahoney3

ABSTRACT

In 2012, the Applied Technology Council (ATC) completed a 10-year program under contract with the Federal Emergency Management Agency (FEMA) to develop a next-generation methodology for seismic performance assessment of buildings. Collectively referred to as FEMA P-58, Seismic Performance Assessment of Buildings, Methodology and Implementation, the resulting products describe a general methodology and recommended procedures to assess the probable seismic performance of individual buildings based on their unique site, structural, nonstructural, and occupancy characteristics. Recently, FEMA funded a subsequent phase of work to utilize the performance assessment methodology in benchmarking the performance of U.S. model codes and seismic design standards, and developing performance-based seismic design criteria. In this methodology, seismic performance is characterized on a probabilistic basis in terms of the potential for incurring damage or losses in the form of repair costs, repair time, casualties, unsafe placarding, and environmental impacts. Seismic design objectives under consideration include protection of life, limitation of repair costs and repair time, and functional performance, as measured by FEMA P-58 procedures and performance metrics. This paper presents the initial findings and directions of the new 5-year program for development of performance-based seismic design criteria.

Introduction

In 2001, the Federal Emergency Management Agency (FEMA) awarded the Applied Technology Council (ATC) the first in a series of contracts to develop next-generation performance-based seismic design guidelines for new and existing buildings. These projects would become known as the ATC-58/ATC-58-1 Projects. Present-generation performance-based design procedures are embodied in ASCE/SEI 41-06, Seismic Rehabilitation of Existing Buildings [1]. The principal product of the 10-year work effort under the ATC-58 series of projects was the development of a methodology for seismic performance assessment of individual buildings that accounts for uncertainty in our ability to accurately predict response, and communicates performance in ways that are intended to better relate to the decision-making needs of stakeholders. In 2012, ATC completed a series of reports outlining the new assessment methodology, collectively referred to as FEMA P-58, Seismic

1 Applied Technology Council, 201 Redwood Shores Parkway, Suite 240, Redwood City, CA 94065 2 Simpson Gumpertz & Heger, 100 Pine Street, Suite 1600, San Francisco, CA 94111 3 Federal Emergency Management Agency, 500 C Street SW, Washington, D.C. 20472 Heintz, J.A., Hamburger, R.O., and Mahoney, M. FEMA P-58, Phase 2 – Development of performance-based seismic design criteria. Proceedings of the 10th National Conference in Earthquake Engineering, Earthquake Engineering Research Institute, Anchorage, AK, 2014.

Performance Assessment of Buildings, Methodology and Implementation [2][3][4]. These reports describe a general methodology and recommended procedures to assess the probable seismic performance of individual buildings based on their unique site, structural, nonstructural, and occupancy characteristics (Figure 1). In this methodology, seismic performance is characterized on a probabilistic basis in terms of the potential for incurring damage or losses in the form of repair costs, repair time, casualties, unsafe placarding, and environmental impacts. Although it represents a significant achievement, the performance assessment methodology was not the ultimate objective of FEMA’s overall program to develop next-generation performance-based seismic design guidelines.

Figure 1. The FEMA P-58, Seismic Performance Assessment of Buildings, Methodology and Implementation series of products.

Recently, FEMA funded a subsequent phase of work to utilize the performance assessment methodology to benchmark the performance attainable through compliance with present U.S. model codes and seismic design standards, and to develop performance-based seismic design criteria. Seismic design objectives under consideration include protection of life, limitation of repair costs and repair time, and functional performance, as measured by FEMA P-58 procedures and performance metrics. This paper presents the initial findings and directions of the new 5-year program for development of performance-based seismic design criteria.

The Need for Next-Generation Design Procedures In present-generation procedures, performance is expressed in terms of a series of discrete performance levels identified as Operational, Immediate Occupancy, Life Safety, and Collapse Prevention. These performance levels are applied to both structural and nonstructural components, and are assessed at a specified seismic hazard level. Although they established a vocabulary and provided a means by which engineers could quantify and communicate seismic performance to clients and other stakeholders, implementation of present-generation procedures in practice uncovered certain limitations and identified enhancements that were needed. As outlined in FEMA 445, Next-Generation Performance-Based Seismic Design Guidelines, Program Plan for New and Existing Buildings [5] next generation procedures were needed to:

• Develop a framework for performance assessment that properly accounts for, and adequately communicates to stakeholders, limitations in our ability to definitively predict response, considering the many inherent uncertainties.

• Revise the discrete performance levels defined in present-generation procedures to create new performance measures that better relate to the decision-making needs of stakeholders.

• Create procedures for estimating these new performance measures for both new and existing buildings.

• Expand current nonstructural procedures to explicitly assess the damageability and post-earthquake condition of nonstructural components and systems.

• Modify current structural procedures to assess performance based on global response parameters, so that the response of individual components does not unnecessarily control the prediction of overall structural performance.

Phase 2 Objectives

The FEMA P-58 seismic performance assessment methodology was developed with these needs in mind. The subsequent Phase 2 work, designated the ATC-58-2 Project, is intended to utilize this methodology in the development of performance-based design guidelines and stakeholder guides for improved decision-making in seismic design. As currently envisioned, Phase 2 will result in products that:

• Assist decision-makers in selecting appropriate performance objectives for buildings of different occupancies.

• Assist design professionals in identifying appropriate strategies for structural design of buildings to achieve specific performance objectives.

• Assist design professionals in developing efficient preliminary designs that will require relatively little iteration during the design process.

• Quantify the performance capability of typical buildings designed to current prescriptive building codes, so that designers and building officials can understand code equivalency, and the lack of consistency in current performance and the advantages of performance-based design approaches is evident.

• Provide guidance on simplified design of buildings to achieve different performance objectives.

As part of this work, Phase 2 will exercise the FEMA P-58 seismic performance assessment methodology and identify needed improvements, if any; enhance the methodology to estimate environmental impacts associated with earthquake damage; benchmark the performance of typical code-conforming buildings utilizing next-generation performance metrics; and interact with stakeholders to tailor design guidance to better suit current decision-making needs. Additionally, Phase 2 also includes a task to provide technical assistance to early users of the FEMA P-58 series of products, and to solicit input from such users to inform the Phase 2 developmental efforts. Finally, in addition to design guidance for engineers and stakeholders, final products will include the development of training materials to assist in implementation.

Exercise and Enhancement Extensive quality assurance measures were undertaken to validate the basic methodology and products as part of the Phase 1 developmental process. These included: (1) independent review of the underlying theory and methods by a validation and verification team; (2) review of the component fragility development process by teams of engineers and researchers familiar with the seismic performance of structural and nonstructural components; (3) detailed review of the quality of data and consistent application of procedures by a panel of experts knowledgeable in structural reliability theory; (4) independent review of the calculation algorithms embedded in the supporting electronic materials; and (5) a series of performance evaluations conducted on representative building types to explore the rationality of results. In spite of these efforts, the Phase 2 work recognizes the possibility that additional studies using the FEMA P-58 methodology might result in the need to adjust or calibrate certain aspects of the methodology or the underlying data. Work in Phase 2 will involve additional study of the rationality of results obtained using the assessment methodology and a critical review of experimental data used to develop selected fragility functions. Additionally, Phase 1 included an investigation of the feasibility of incorporating environmental impacts into the FEMA P-58 loss computations. Recommended environmental metrics include climate change potential (measured in CO2 equivalents) and primary energy consumption. Procedures for estimating environmental impacts from earthquakes, and integrating results in an overall Life Cycle Assessment (LCA) process, are contained in a companion volume in the FEMA P-58 series of reports [6], which is the subject of another paper in this session. Phase 2 work will include enhancement of the FEMA P-58 assessment methodology to consider environmental impacts utilizing these recommendations.

Benchmarking of Typical Code-Conforming Buildings Development of performance-based design guidance requires a detailed understanding of the performance objectives that will be targeted by the resulting designs. In the case of new buildings, an obvious target is the performance capability that is inherent in seismic design and detailing requirements contained in current codes and standards. A key effort in this work is to benchmark the performance of code-conforming buildings in terms of next-generation performance metrics. Performance objectives that are being considered include protection of life, repair costs and repair time, and functional performance, as measured by FEMA P-58 procedures and performance metrics. Benchmarking studies were initiated under the FEMA-funded ATC-63-2/ATC-63-3 Projects, and will be continued under the Phase 2 work of this project. Results from initial studies indicate that for some systems and components, predicted losses did not benchmark well with past earthquake experience data, and that predicted losses were higher than expected. In particular, the studies seem to over-predict the potential for post-earthquake loss of function. Quantitatively defining functional performance of buildings has proven to be a very difficult challenge that will need to be addressed as Phase 2 progresses. Benchmarking results to date are documented a

companion volume in the FEMA P-58 series of reports [7], which is the subject of another paper in this session.

Stakeholder Interactions In 2002, early in Phase 1, ATC conducted a FEMA-funded workshop on communicating earthquake risk that was intended to obtain guidance on stakeholder needs [8]. The findings from this workshop set the direction for the Phase 1 development of performance metrics in terms of direct losses (repair costs), downtime (loss of use), indirect costs associated with loss of use, and casualties (injuries and loss of life) [9]. These metrics have since evolved into repair costs, repair time, casualties, and unsafe placarding (and will eventually include environmental impacts). Recognizing that stakeholder input is key to development of design guidance, Phase 2 work includes significant plans for interacting with stakeholders and identifying their decision-making needs. A key objective is to establish a framework and vocabulary for interaction between decision-makers and design teams so that stakeholders are able to communicate seismic risk concerns in a way that promotes a common understanding and enhances the design process. The first major activity on the ATC-58-2 Project was the conduct of a follow-on workshop on communicating seismic performance metrics in design decision-making, which was held in September 2013. The purpose of this workshop was not to re-ask the questions about performance metrics that were answered more than 10 years ago, but to ask how the results of a FEMA P-58 seismic performance assessment should be packaged to serve the seismic design decision-making needs as they exist today. Workshop attendees included a broad range of stakeholders involved in building design, construction, and management decision-making, including owners and developers, lending and insurance representatives, institutional and corporate building managers, building officials, civic building managers, and design professionals. Discussions were organized into a series of plenary presentations and interactive breakout sessions that were designed to identify how various stakeholder groups currently make seismic-related decisions, and how FEMA P-58 assessment results could be effectively used as part of the building design and procurement process. The types of decisions that were explored included: new building design decisions; retrofit of existing buildings; rental decisions; loan or financing decisions; insurance; and emergency preparedness/risk planning activities. Workshop results will be used to guide the development of the Phase 2 engineering and stakeholder design guidance products. Preliminary workshop findings have been organized into two areas: (1) stakeholder observations and concerns; and (2) recommendations for implementation of the FEMA P-58 methodology into engineering practice and the building management and procurement process. Stakeholder Observations and Concerns Preliminary findings related to stakeholder observations and concerns include:

• The prevailing perspective is that buildings are “designed to code.” The market is competitive, and, at present, there is little or no market for enhanced seismic performance.

• Performance metrics of downtime and repair costs were of most interest.

• There is some interest and perceived value in the ability to know the breakdown of what is contributing to loss, and how much of a contribution certain elements make to total loss.

• There was much concern over legal liability associated with knowing seismic performance information related to poor performance. Most stakeholders did not want to know an estimated number of potential casualties, and would not know what to do with such information.

• There is concern that two engineers performing a FEMA P-58 assessment would get different results. With the current state of practice in seismic loss estimation (i.e., PMLs), there is also concern that FEMA P-58 assessment results can be “gamed.” Both the accuracy and credibility of the methodology need to be addressed.

• University, high-technology, and bio-technology stakeholders in attendance reported sophisticated building management and procurement processes that included consideration of seismic issues. They also reported that new technologies like FEMA P-58 are considered, when brought to them by engineering consultants.

• Insurers in attendance reported that seismic performance concerns are regional, rather than building specific, although they do want to avoid obviously vulnerable buildings. Also, it was noted that seismic hazard is only one of many hazards that are considered (e.g., fire and flood).

• Lenders in attendance expressed that their primary concern is loan-to-value ratio, and that borrowers are responsible for payment, even in the event of an earthquake. They also mentioned a community expectation that buildings in their loan portfolio have been adequately vetted, and expressed a desired to have a reputation of only lending on “good” buildings.

• Developers in attendance noted that development decisions depend on market conditions and market rents. It is hard to be an early adopter of something that increases building design or construction costs without a clearly defined (and favorable) return on investment.

Recommendations for Implementation of the FEMA P-58 Methodology Preliminary recommendations related to implementation of the FEMA P-58 Methodology into engineering practice and building management and procurement include:

• The FEMA P-58 methodology cannot be all things to all people. Different users will have different needs, and not all stakeholders will be interested in (or will need) the information that FEMA P-58 has to offer.

• The objective of guidance materials should be two-fold: first to motivate stakeholders to utilize the methodology, and second to help them use it.

• Initial guidance should focus on early adopters (i.e., those users whose needs are closely aligned with the products, are receptive to new technologies, are likely recognize the value, and have the resources necessary to implement the technology in practice).

• Potential early adopters include: engineering practitioners interested in differentiating their services from the competition; institutions with important buildings at a fixed location (e.g., universities); manufacturers with valuable contents or operations that are sensitive to product life-cycle and business interruption concerns; corporations and businesses that are sensitive to business interruption concerns; sophisticated building owners located in regions of high seismicity that are sensitive to seismic performance concerns.

• If necessary, adjustments in the current FEMA P-58 methodology (e.g., additional fragility classifications) should be made to make it as consistent as possible with the needs of potential early adopters.

• We need to explain how FEMA P-58 relates to methodologies and tools that currently exist (e.g., Building Codes and Standards, ASCE/SEI 41, HAZUS, ST RISK, and PML evaluations).

• In emphasizing the next-generation change from discrete performance levels to a performance continuum (Figure 2), we have lost the ability to communicate performance objectives to decision makers with recognizable acceptability criteria. We need to figure out how to bridge this communication gap between present-generation and next-generation procedures.

Figure 2. Present-generation discrete performance levels mapped into the next-generation

performance continuum.

• Stakeholder guides should be focused as narrowly as possible. Potential users should feel that the guides are immediately relevant to their situation or needs.

• Guidance should speak to (or address) potential barriers to implementation. Potential barriers identified in the workshop include: a perceived high cost; the length of time needed to perform an assessment; the apparent complexity of the results; disenchantment with the

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Operational Immediate Occupancy

Life Safety Collapse Prevention

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current PML market; involvement of the structural engineer late in the design process after key financial and building design issues have already been decided.

• We need to clearly identify the cost and level of effort needed to get meaningful assessment results. Without this information, stakeholders cannot consider using the methodology in their processes.

Conclusions

In 2012, ATC completed a 10-year program to develop a next-generation methodology for seismic performance assessment of buildings. Although a significant achievement, the performance assessment methodology is not the ultimate objective of FEMA’s overall program to develop next-generation performance-based seismic design guidelines. Recently, FEMA funded the next phase of work intended to utilize the performance assessment methodology in benchmarking the performance of U.S. model codes and standards, and to develop performance-based seismic design criteria. Work in this phase will exercise the FEMA P-58 seismic performance assessment methodology and identify needed improvements, if any; enhance the methodology to estimate environmental impacts associated with earthquake damage; benchmark the performance of typical code-conforming buildings utilizing next-generation performance metrics; and interact with stakeholders to tailor design guidance to better suit current decision-making needs.

Acknowledgments ATC is indebted to the members of the ATC-58/ATC-58-1/ATC-58-2 Project Teams for their efforts in performing this work. In particular, ATC would like to acknowledge Laura Samant, Tom Tobin, and Maryann Phipps for their initial analyses and summary of results from the September 2013 stakeholder workshop. ATC also gratefully acknowledges the input and guidance provided by Michael Mahoney (FEMA Project Officer) and Robert Hanson (FEMA Technical Monitor) in the development of the FEMA P-58 methodology and associated products. The work forming the basis for this paper was conducted pursuant to multiple contracts with the Federal Emergency Management Agency (FEMA). The substance of such work is dedicated to the public.

References 1. ASCE, 2007, Seismic Rehabilitation of Existing Buildings, ASCE/SEI 41-06, American Society of Civil

Engineers, Reston, Virginia.

2. FEMA, 2012, Seismic Performance Assessment of Buildings, Volume 1 – Methodology, FEMA P-58-1, prepared by the Applied Technology Council for the Federal Emergency Management Agency, Washington, D.C.

3. FEMA, 2012, Seismic Performance Assessment of Buildings, Volume 2 – Implementation Guide, FEMA P-58-2, prepared by the Applied Technology Council for the Federal Emergency Management Agency, Washington, D.C.

4. FEMA, 2012, Seismic Performance Assessment of Buildings, Volume 3 – Supporting Electronic Materials and Background Documentation, FEMA P-58-3, prepared by the Applied Technology Council for the Federal Emergency Management Agency, Washington, D.C.

5. FEMA, 2006, Next-Generation Performance-Based Seismic Design Guidelines, Program Plan for New and Existing Buildings, FEMA 445, prepared by the Applied Technology Council for the Federal Emergency Management Agency, Washington, D.C.

6. FEMA, 2013, Seismic Performance Assessment of Buildings, Volume 4 – Methodology for Assessing Environmental Impacts, FEMA P-58-4, prepared by the Applied Technology Council for the Federal Emergency Management Agency, Washington, D.C.

7. FEMA, 2013, Seismic Performance Assessment of Buildings, Volume 5 – Evaluation of Seismic Performance Assessment Methodologies and Investigation of Building Seismic Performance, FEMA P-58-5, prepared by the Applied Technology Council for the Federal Emergency Management Agency, Washington, D.C.

8. ATC, 2002, Proceedings of a FEMA-Sponsored Workshop on Communicating Earthquake Risk, ATC-58-1, Applied Technology Council, Redwood City, California.

9. ATC, 2003, Preliminary Evaluation of Methods for Defining Performance, ATC-58-2, Applied Technology Council, Redwood City, California.