PROJECT OVERVIEW

Title: Methodology to Assess and Verify the Seismic Capacity of Low-Rise Buildings

Project Status: Completed

Client: Federal Emergency Management Agency (FEMA)

PROJECT SUMMARY

This project seeks to conduct the first phase of a multi-phase project to eventually develop an alternative seismic design approach for low-rise construction in the United States that similarly utilizes non-linear response analysis results in a simplified displacement-based approach.  The approach would ideally incorporate a computing tool or analytical engine (similar to the tool developed for FEMA P-807) using the large amount of dynamic analysis data that has already been generated.  Rather than calculating an equivalent lateral force as prescribed in ASCE/SEI 7, such an approach would utilize the assessed nonlinear response characteristics of the building to select and size the seismic-force-resisting system.  

One challenge in implementing such an approach would be to validate it against the performance of standard code-designed buildings and demonstrate that the seismic performance intent of current U.S. model building codes and standards are met.  The FEMA P-695 report, Quantification of Building Seismic Performance Factors, provides a methodology that can be used to validate the performance equivalency of alternative design procedures.  To be generally useful and nationally applicable, an alternative design procedure would need to be verified for a variety of: (a) seismic-force-resisting systems; (b) site classes and seismic hazards; and (c) range of building configurations.  This validation effort would require the pre-determination of applicable building heights and structural system types, and a comparison of these parameters with the Canadian study parameters to determine which of the Canadian study data can be used, and what, if any, new data must be developed.

Task 1: Develop Initial Methodology for Validation on Selected Systems.  This task involves the investigation of the development of an initial methodology for simplified design of low-rise buildingsbased on the methodology developed on the Canadian project. 

Subtask 1.1 – Review Information from Related Projects

The Project Management Committee will review the work conducted on the Canadian project to understand the technical basis, and consider what adaptations would be needed for U.S. design and construction practice.  The PMC will also review work from other relevant projects including: FEMA P-807Seismic Evaluation and Retrofit of Weak-Story Wood-Frame Buildings, FEMA P-440A Effects of Strength and Stiffness Degradation on Seismic Response (ATC-62 Project), NIST GCR 10-917-9 Applicability of Nonlinear Multiple-Degree-of-Freedom Modeling for Design (ATC 76-6 Project), Static Pushover to Incremental Dynamic Analysis, SPO2IDA, as developed by Vamvatsikos and Cornell (2006).  Work will include the following milestones:

• Initial review of Canadian Methodology (February 8, 2012)
• Identify potential scope of consideration for U.S. practice based on the issues listed below (April 30, 2012)
  • Performance level/definition
  • Definition of low rise
  • Construction types (prototypes)
  • Damage patterns
  • Earthquake sources/regions of seismicity
  • Behavioral limitations/acceptable modes of behavior
  • New buildings with an eye toward existing buildings
  • Analytical engine
  • Modeling sophistication
  • Gravity system drift capacities
  • Torsional considerations
  • Case study analyses as required for validation of scope
• Focused review of Canadian Methodology (June 15, 2012) relative to the above (bulleted) task breakdown
  • Develop ideas for U.S. methodology
  • Review Canadian methodology for solutions
• Summarize the Canadian Methodology (June 30, 2012)
  • Identify what is applicable to U.S. practice
  • Identify necessary adaptations for U.S. practice

Subtask 1.2 – Develop Initial Methodology for Validation Studies

Based on available information, the Project Management Committee will develop an initial methodology targeted to U.S. applications and perform limited proof-of-concept studies.  In developing the initial methodology, the PMC will consider: (1) selected lateral systems that are popularly used in U.S. construction; (2) defined seismic environments and appropriate earthquake ground motion records for intended nonlinear responses analysis and performance measurement; and (3) necessary restrictions on building configuration (e.g. number of stories, height, vertical/ horizontal irregularities). 

At this time, it is envisioned that the U.S. methodology will be closely patterned after the Canadian Methodology.  It is assumed that prior design and analytical work conducted on the Canadian project will be leveraged to conduct proof-of-concept studies.  The scope and extent of studies that can be performed will depend on the degree of similarity or difference between the U.S. methodology and the Canadian Methodology and the resulting variations in construction types, seismicity, and building configurations covered.  Workwill include the following milestones:

• Confirm scope of low-rise applications in U.S. (May 31, 2012)
• Perform limited investigation of technical adaptations (July 15, 2012)
  • Choose one prototype (e.g. wood); attempt solution; identify issues
  • Investigate multistory wood systems; explore modes of behavior including structural and nonstructural elements
  • Check a FEMA P-807 building using the Canadian Analyzer
• Refine list of necessary adaptations for U.S. practice (July 31, 2012)

Task 2: Prepare Draft Outline of the Methodology.  This task involves the preparation of an early draft (20% complete) report outlining the initial methodology, including a summary of the Canadian methodology, adaptations necessary for U.S. construction practice, and recommendations for study in future phases of work.  The report will be prepared under the direction of the Project Technical Director, with assistance from selected members of the PMC.  Workwill include the following milestones:

• Development of a preliminary Outline (June 30, 2012)
• Develop future plan (scope/level of effort/schedule) for adaptation of the Canadian Methodology to develop a FEMA methodology for low-rise buildings in the U.S. (August 15, 2012)
  • Compare with current US practice (IEBC, ASCE 41)
  • Consider implementation ideas (incentives/liability/training)
  • Consider verification
• Submissionof draft report to FEMA (September 14, 2012)

PROJECT OVERVIEW

Title:  Planning and Conduct of an Earthquake Building Performance Rating System Workshop

Project Status:  Completed May 2011

Client:  Federal Emergency Management Agency (FEMA)

Related Projects and Reports:  The need for this workshop was the highest ranked recommendation in the NEHRP Workshop on Meeting the Challenges of Existing Buildings, which was held in San Francisco in September 2007 (ATC-71 Project)

PROJECT SUMMARY

Rating systems are common for everything from restaurants and movies to energy efficiency of appliances and “green” buildings. But when it comes to earthquake risk, building occupants and owners lack a simple, common vocabulary for decision-making, such as a rating system. An “Earthquake Rating System for Building Performance” was identified as the highest-ranked need in earthquake hazard risk reduction in a variety of recent forums, including the National Earthquake Hazards Reduction Program (NEHRP) Workshop on Meeting the Challenges of Existing Buildings, which was conducted in September 2007 in San Francisco by the Applied Technology Council (ATC) and the Earthquake Engineering Research Institute, with funding from the Federal Emergency Agency (FEMA) and other National Earthquake Hazard Reduction Program (NEHRP) federal agencies.

The Earthquake Building Performance Rating System Workshop was conducted to gather input on potentially developing and implementing a new system for rating the earthquake performance of existing buildings. Prior to the Workshop, ATC organized a web-based Discussion Forum to enable Workshop participants and other interested stakeholders to openly discuss the relevance and usability of such a system. Both the Discussion Forum and the Workshop were intended to enable stakeholders to express their views on the desirability of developing and implementing an Earthquake Rating System for Building Performance. Topics addressed at the Workshop included (1) the extent to which such a rating system would encourage and promote building seismic evaluation and rehabilitation, (2) technical difficulties and related consistency issues, (3) advantages and disadvantages of such a system, (4) potential socio-economic impediments, and (5) other stakeholder concerns and needs.  Following the Workshop, ATC issued the ATC-71-2 Workshop Proceedings, which summarize the presentations, discussions and findings of the Workshop, and provides a roadmap on the steps necessary to develop a rigorous but practical building rating system.

Workshop attendees included a broad range of stakeholders, including representatives from the insurance, financial, and real estate industries, social scientists, risk managers, building owners and regulators, earthquake engineering professionals, and key specialists involved in other building and construction rating programs.

FEMA P-50 REFERENCE MATERIALS

The FEMA P-50 report, Simplified Seismic Assessment of Detached, Single-Family, Wood-Frame Dwellings, uses the Simplified Seismic Assessment Form.

The FEMA P-50-1 report, Seismic Retrofit Guidelines for Detached, Single-Family, Wood-Frame Dwellings, is another available resource.

When completing the Simplified Seismic Assessment Form, available resources to determine site liquefaction potential/susceptibility are listed here.

To determine site landslide potential/susceptibility, available resources are listed here.

For more information about the FEMA P-50 report, click here.

ATC-71 PROJECT OVERVIEW

Title: Development of Simplified Guidance for Seismic Rehabilitation of Soft-Story Wood-Frame Buildings

Project Status: Completed May 2012

Client: Federal Emergency Management Agency (FEMA)

Related Projects and Reports:  The ATC-71 Projecthas produced a three-part report on the NEHRP Workshop on Meeting the Challenges of Existing Buildings

PROJECT SUMMARY

Multi-unit wood-frame buildings with a weak first story represent a significant risk in highly seismic regions of the United States because of their high potential for collapse. This collapse potential is due primarily to their soft or weak first-story walls, which have often been weakened by large numbers of openings such as garages or store front windows.  The ATC-71-1 project developed FEMA P-807 report, Seismic Evaluation and Retrofit of Multi-Unit Wood-Frame Buildings With Weak First Stories addressing seismic retrofitting of weak-story wood-frame buildings in seismically active regions of the United States, with a focus on multi-family, multi-story buildings with weak first stories, such as those damaged in the Marina District of San Francisco in the 1989 Loma Prieta earthquake, and apartment buildings with tuck-under parking, such as those damaged in Southern California in the 1994 Northridge earthquake.  These seismic retrofitting guidelines are the first to focus solely on the weak first story and to provide just enough additional strength to protect the first floor from collapse but not so much as to drive earthquake forces into the upper stories, placing them at risk of collapse. They are also the first to take into account the strength provided by existing non-structural walls, making seismic retrofitting more affordable.

An electronic tool, similar to a graphic spreadsheet, was developed as part of the project to help apply the rules and perform the calculations described in the report.  The Weak Story Tool and product support is available for here. Note that the report contains all the data, formulas, and procedural background needed to apply the method without using the Weak Story Tool.

PROJECT WORKSHOP OVERVIEW

Title:  Planning and Conduct of an Earthquake Building Performance Rating System Workshop

Project Status:  Completed May 2011

Client:  Federal Emergency Management Agency (FEMA)

Related Projects and Reports:  The need for this workshop was the highest ranked recommendation in the NEHRP Workshop on Meeting the Challenges of Existing Buildings, which was held in San Francisco in September 2007 (ATC-71 Project)

PROJECT SUMMARY

Rating systems are common for everything from restaurants and movies to energy efficiency of appliances and “green” buildings. But when it comes to earthquake risk, building occupants and owners lack a simple, common vocabulary for decision-making, such as a rating system. An “Earthquake Rating System for Building Performance” was identified as the highest-ranked need in earthquake hazard risk reduction in a variety of recent forums, including the National Earthquake Hazards Reduction Program (NEHRP) Workshop on Meeting the Challenges of Existing Buildings, which was conducted in September 2007 in San Francisco by the Applied Technology Council (ATC) and the Earthquake Engineering Research Institute, with funding from the Federal Emergency Agency (FEMA) and other National Earthquake Hazard Reduction Program (NEHRP) federal agencies.

The Earthquake Building Performance Rating System Workshop was conducted to gather input on potentially developing and implementing a new system for rating the earthquake performance of existing buildings. Prior to the Workshop, ATC organized a web-based Discussion Forum to enable Workshop participants and other interested stakeholders to openly discuss the relevance and usability of such a system. Both the Discussion Forum and the Workshop were intended to enable stakeholders to express their views on the desirability of developing and implementing an Earthquake Rating System for Building Performance. Topics addressed at the Workshop included (1) the extent to which such a rating system would encourage and promote building seismic evaluation and rehabilitation, (2) technical difficulties and related consistency issues, (3) advantages and disadvantages of such a system, (4) potential socio-economic impediments, and (5) other stakeholder concerns and needs.  Following the Workshop, ATC issued the ATC-71-2 Workshop Proceedings, which summarize the presentations, discussions and findings of the Workshop, and provides a roadmap on the steps necessary to develop a rigorous but practical building rating system.

Workshop attendees included a broad range of stakeholders, including representatives from the insurance, financial, and real estate industries, social scientists, risk managers, building owners and regulators, earthquake engineering professionals, and key specialists involved in other building and construction rating programs.

FEMA P-50 REFERENCE MATERIALS

The FEMA P-50 report, Simplified Seismic Assessment of Detached, Single-Family, Wood-Frame Dwellings, uses the Simplified Seismic Assessment Form.

The FEMA P-50-1 report, Seismic Retrofit Guidelines for Detached, Single-Family, Wood-Frame Dwellings, is another available resource.

When completing the Simplified Seismic Assessment Form, available resources to determine site liquefaction potential/susceptibility are listed here.

To determine site landslide potential/susceptibility, available resources are listed here.

PROJECT OVERVIEW

Title: Environmental Benefits of Retrofitting.

Project Status: Completed

Client: Federal Emergency Management Agency (FEMA)

PROJECT SUMMARY

One of the most significant impediments to seismic retrofit is cost, however, cost estimates rarely include the environmental benefit of retrofitting an existing building as opposed to demolishing the building, disposing of the demolished building materials, and replacing it with a new structure.  This project seeks to complete development of the Seismic Performance Assessment Methodology and to create a tool that can be adapted to capture this benefit.  The primary purpose of this task order is to identify what is needed to adapt the Seismic Performance Assessment Methodology to measure environmental consequences, such as carbon footprint, and to begin the process of developing the necessary information.

Task 1: Develop a Performance-Based Environmental Impact Methodology

Under this task the ATC-86 Project Management Committee, with the overview and guidance of the ATC-58 Project Management Committee, will develop a Performance-Based Environmental Impact Methodology for use with the Seismic Performance Assessment Methodology now under development on the ATC-58 Project.  As currently envisioned, the Performance-Based Environmental Impact Methodology will quantify the environmental effects of earthquake-related damage and the potential benefits (in terms of reduced environmental effects) related to retrofitting an existing building or designing a new building for improved seismic performance.  Possible metrics under consideration include greenhouse gas emissions, resource depletion, and embodied energy.  The approach is expected to involve calculating environmental impacts in much the same way that repair costs are estimated for the various building elements and components in the ATC-58 Project, and is expected to contribute to, or interface with, the life cycle assessment process currently used in determining environmental impacts for new building projects. 

For this information to be incorporated into the Seismic Performance Assessment Methodology, the environmental consequence functions would need to be developed and incorporated into the consequence function spread sheets and imported into the companion electronic Performance Assessment Calculation Tool (PACT).  Based on the level of effort required to develop and program consequence functions on the ATC-58 Project, development of the associated environmental consequence functions for the vast array of components and systems now considered in the ATC-58 Project is beyond the level of effort that can be funded on this task order. 

Work will consist of the development of an overall environmental loss assessment methodology, including selection of the most appropriate environmental loss measure, and direction on how environmental consequences should be estimated.  As currently envisioned, the scope of this effort is limited to developing and completing the environmental impact methodology, and testing it on a limited number of components and/or system fragilities. 

Task 2: Prepare Draft Report Describing Performance-Based Environmental Impact Methodology

Under this task the ATC-86 Project Management Committee will prepare a draft report describing the Performance-Based Environmental Impact Methodology.  As a minimum, this report will identify the recommended environmental loss metrics, the relationship between this methodology and the life cycle assessment (LCA) process, how environmental consequences should be estimated, and how the recommended methodology can be implemented within the ATC-58 Seismic Performance Assessment Methodologyand the Performance Assessment Calculation Tool (PACT).

Task 3: Review of Draft Performance-Based Environmental Impact Methodology

This task involves review of the recommended Performance-Based Environmental Impact Methodology by selected experts and stakeholder groups.  The list of reviewers will be determined with input from FEMA, and may include members of the ATC-58 Project Team, the American Society of Civil Engineers (ASCE) Structural Engineering Institute (SEI) Sustainability Committee, and other environmental experts.  As currently envisioned, outside reviewers will not be funded under the ATC-86 project, but will be invited to participate on a voluntary basis. 

Task 4a: Complete the Performance-Based Environmental Impact Methodology

Based on review comments received, the ATC-86 Project Management Committee will update and refine the draft Performance-Based Environmental Impact Methodology. 

Task 4b: PrepareFinal Report

Based on any changes to the methodology, the ATC-86 Project Management Committee will update and refine the draft report and prepare a final report outlining the recommended Performance-Based Environmental Impact Methodology and what is needed to implement it within the ATC-58 Seismic Performance Assessment Methodology.