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.

PROJECT OVERVIEW

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

Project Status: Complete

Client: Federal Emergency Management Agency (FEMA)

PROJECT SUMMARY

A reasonable alternative seismic design approach would be to use non-linear response analysis results in a simplified displacement-based approach.  Rather than calculating an equivalent lateral force for the to-be-designed simple building as prescribed in ASCE/SEI 7, such an approach could utilize the assessed nonlinear response characteristics of the initially proposed simple building for selection and sizing its seismic lateral force-resisting systems.  The challenge in implementing such an approach is that it would need to be validated against the performance of standard code-designed buildings and shown to meet the seismic performance intent of the standard seismic design procedure.  

The recently published FEMA P-695, Quantification of Building Seismic Performance Factors, and the FEMA P-58, Seismic Performance Assessment of Buildings, provide methodologies that can be used to validate the performance equivalency of alternative design procedures.  To be generally useful and nationally applicable, an alternative procedure would also need to be verified to be applicable to: (a) any selected lateral force resisting system, (b) any seismic hazard site, and (c) a reasonable range of building configurations.

This project seeks to complete three aspects, including:  (1) development of a methodology based on simplified nonlinear response analysis to assess and verify that building designs will meet the seismic performance intent of building codes and standards; and (2) development of a tool, based-on this methodology, to assist and improve seismic designs of low-rise buildings; and (3) consideration of the potential consequences of earthquake damage in the design decision process.

Task 1: Continue Development of the Canadian Methodology for Application to U.S. Practice

Under this task, the project team will investigate further extrapolation of the Canadian Methodology and available data to U.S. applications for new construction.  As developed under Task 17.2 in the initial phase of work, the preliminary scope of U.S. application for low-rise buildings is six stories or less, with the systems identified in Table 1.

Table 1.  Preliminary Structural Systems for U.S. Low-Rise Construction

Table 1 also identifies systems for which partial data are available from the Canadian work.  A key limitation is that the Canadian Methodology developed data for 2-story systems and extrapolated it to 3-story systems, while a U.S. application of the methodology may need to extend as high as 6 stories.  A basic assumption of the Canadian Methodology presumes shear behavior, while taller systems will need to be investigated for flexural and cantilever behavior in addition to shear behavior.  

Also investigated under Task 17.2 during the first phase of work was the effect of ground motion characteristics on the predicted response.  Results from this study will be used to refine additional investigations in the current phase of work. 

Selected studies will be targeted to verify the concept and to refine the framework of the proposed U.S. application of the methodology.  At this time, it is envisioned that the U.S. application will be patterned primarily after the Canadian Methodology, but might also be patterned after work leading to the development of the FEMA P-807 methodology for weak story wood frame buildings, which was similar in concept to the Canadian project.  It is assumed that prior design and analytical work will be leveraged to conduct the current work.  The actual number of studies that can be performed will depend on the degree of difficulty and the resulting variations in construction types, seismicity, and building configurations covered.  The extent of validation studies that can be conducted using available project resources will be determined in collaboration with the FEMA Task Monitor and the Project Management Committee. 

Task 2: Complete the Framework of the Methodology with Performance Measures

Based on the developmental work conducted under Task 17.5, the project team will revise the initial report on the outline of the methodology developed under Task 17.3 of the prior phase of work.  The revised report will be prepared by the Project Director and members of the Project Management Committee, and will be reviewed by the Project Review Panel as proposed under Task 17.7, below.  The report will include an assessment of the Project Work Plan, and recommendations for the level of effort of future developmental phases.

PROJECT OVERVIEW

Title: Identification and Mitigation of Nonductile Concrete Buildings

Project Status: Completed

Client: Federal Emergency Management Agency (FEMA)

PROJECT SUMMARY

This project seeks to provide more robust information about the specific characteristics of older nonductile concrete buildings by identifying certain subclasses with inherent structural deficiencies suspected to be the most significant, and that can be more readily identified, and that represent a more consistent level of risk.  Identification of the most vulnerable features of these subclasses will allow prioritization of research and more rapid implementation of current and emerging performance-based seismic design technologies for mitigation of hazardous nonductile concrete buildings.

Work on this project is a continuation of efforts undertaken on the FEMA-funded ATC 78 Project, under which ATC prepared the interim 50% complete draft report, Identification and Mitigation of Non-Ductile Concrete Buildings.

Task 1: Continue Pilot Study for Evaluation of Method for Selection of Collapse Indicators.

This task involves reviewing and advancing work performed in the ATC 78 Project (the first phase of this project) to develop a method of identifying, characterizing, and ranking the significance of deficient characteristics of older nonductile concrete buildings. The work-product of this task is intended to serve as a pilot study for evaluation of a methodology to select configurational and/or structural characteristics that are significant collapse indicators in older concrete buildings.  An outline for this pilot study is described as part of Task 1.4 in the NIST/ATC 76-5 Program Plan, but progress in the first phase will focus additional studies in more detail than the original outline.

Subtask 1.1 – Review Concrete Building Subclass Information from Related Projects and Define Basic Nonductile Concrete Building Prototypes.

This task requires coordination with ongoing research in this area, including: (1) studies undertaken as part of the NSF/NEES Grand Challenge research project; (2) efforts of the Earthquake Engineering Research Institute (EERI) Concrete Coalition; (3) the NIST/BSSC study to identify concrete building subtypes; and (4) efforts undertaken to implement the NIST/ATC 76-5 Program Plan.  Work in Phase 1 (ATC-78 Project) concluded that a major issue pertaining to determination of the importance of collapse indicators is development of methods to combine the effects of multiple collapse indicators in one building.  It was recommended to study whether initial separation of buildings into structural types would simplify the need to consider all combinations of all collapse indicators.  It was also suggested to study sequencing of inclusion of collapse indicators in such a way that all combinations were not necessary.

Subtask 1.2 – Conduct Problem-Focused Analytical Studies to improve and refine the methodology proposed to identify and prioritize collapse indicators.

Three major issues were identified in Phase 1 that need resolution:

• It is well known that many collapses of concrete buildings initiate in the gravity load carrying system.  The various seismic weaknesses in such systems must be incorporated into the overall methodology.  Stiffness and/or strength of such systems can be easily included in model studies, but P-delta effects cannot be included without creating another variable that will affect the significance of each collapse indicator.  The methodology must be generalized, either within the evaluation procedure or for study of collapse indicators.
•  Many, if not most, older concrete buildings contain walls that will affect response—either significant shear walls, or incidental walls such as fire stops or perimeter closer walls.  Concrete wall structures have been studied in previous projects associated with FEMA P695, Quantification of Building Seismic Performance Factors, but definition of collapse in such buildings is poorly identified.  Walls in combination with frames have not been studied.  A complete collapse indicator methodology must include walls.
• Models used in Phase 1 of this project were adequate to measure flexural response, or adequate to measure shear/compression failure, but not both.  The crossover effect on prioritizing collapse indicators must be studied and incorporated into the methodology.

Subtask 1.3 – Incorporate the results of Subtasks 1.1 and 1.2 into advancing Building Evaluation Rules or other evaluation methodology to identify buildings with high probability of collapse.

This task utilizes the trends from focused analytical studies to assist in developing an enhanced screening procedure that could be used to progressively prioritize (screen) an inventory of older nonductile concrete buildings.  As currently envisioned, this procedure would involve more detail and effort (with greater reliability) than the FEMA 154 procedure for rapid visual screening of buildings (FEMA 2002), but less effort than the ASCE 31 procedure for seismic evaluation of existing buildings (ASCE 2003). 

Task 2: Preparation of a Report Documenting Analytical Studies of Subtask 1.1 and the Draft Building Evaluation Procedures developed in Subtasks 1.2 and 1.3.

Work will include preparationand publication of a final technical report (April 2013)

PROJECT OVERVIEW

Title: Identification and Mitigation of Nonductile Concrete Buildings

Project Status: Completed

Client: Federal Emergency Management Agency (FEMA)

PROJECT SUMMARY

This project is to begin development of a simplified assessment guideline document for older or non-ductile concrete buildings to allow identification of those buildings that present an earthquake collapse hazard so that they may be evaluated and retrofitted, in order to mitigate the risks presented by this class of buildings.

Task 1: Development of a Simplified Methodology for Identifying Concrete Moment Frame Buildings with a High Probability of Collapse in Earthquakes

Building on the work performed under ATC 78-1, which focused on the identification of Collapse Indicators for older concrete buildings and the identification and resolution of related critical issues, work on this task will focus on the development of a simplified methodology for identifying concrete moment frame buildings with a high probability of collapse in earthquakes.  The simplified methodology will be based on analytical results from this and other projects, past collapses of concrete buildings in earthquakes, laboratory research on concrete structural components, and engineering judgment. Such a methodology will allow identification of additional systematic analysis that is required to complete the methodology.

Moment frame buildings were selected for this initial developmental effort because of their  known high potential vulnerability and the availability of methods and procedures that can contribute to the development of a simplified methodology for identifying concrete moment frame buildings with a high probability of collapse in earthquakes.  The development of similar methods for other older concrete building structural systems is reserved for a future project(s).

Work on this task will consist of three subtasks:  (1) the identification of existing simplified elastic methods to estimate inelastic displacements, along with the identification of improvements needed to such methods for this project; (2) the identification of collapse indicators for global building response that can be used as acceptance criteria, along with the identification of and analysis methods to determine acceptance criteria; and (3) the integration of the results from the above tasks to develop the simplified methodology for identifying concrete moment frame buildings with a high probability of collapse in earthquakes.

The methodology will utilize a linear analysis approach with modifiers to determine anticipated inelastic deformations that would be expected in a moment frame building if analyzed using non-linear time history analysis procedures given a suite of 44 ground motions.  Collapse indicators that can be used as acceptance criteria to predict global building collapse will be identified.  A simplified methodology will be developed to predict moment frame buildings with a high probability of collapse in earthquakes. 

As specified in the SOW, ATC will use (on this task) information on Collapse Indicators that were identified and evaluated during prior phases of this project.  The Project Management Committee will also consider and use, as appropriate (1) data generated by the NSF NEES Grand Challenge Project on Nonductile Concrete Frame Structures, (2) information being developed under the NIST-funded ATC-95 Project, Development of a Collapse Indicator Methodology for Existing Reinforced Concrete Buildings, and (3) California inventory data on older concrete buildings currently being collected by the Concrete Coalition.

Task 2: Demonstration of the Feasibility of the Simplified Methodology by Conducting and Documenting a Pilot Study for Moment Frame Buildings

The feasibility of the methodology will be demonstrated by doing a pilot study on regular moment frame buildings.  The procedures of the methodology will be demonstrated and the results will be compared to detailed studies incorporating non-linear time history analyses of the subject moment frame buildings.  The pilot study will be summarized in a final report.

The Pilot Study to demonstrate the feasibility of simplified methodology for moment frame buildings will be carried under the direction of the Project Management Committee.  The study will be documented in a project report (principal task order project deliverable) that specifically demonstrates the feasibility of the simplified methodology for identifying concrete moment frame buildings with a high probability of collapse in earthquakes.  The Project Technical Director will serve as the lead author/editor of the document, with chapter contributions provided by the various Project Management Committee members and the Project Working Groups.  One PMC meeting at the outset of this task and possibly one near the end of this task are planned.  Between meetings, the PMC will communicate via WebEx meetings and telephone conference calls.