Projects

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

Material	Lateral Deformation Resisting System (LDRS)	Availability
Wood stud	Plywood shear wall	SRG1
Metal stud	Plywood	-
	Sheet metal/gyp composite (Sure Board-type)	-
	Corrugated sheet metal	-
CMU	CMU shear wall	SRG1
Structural Steel	Moment frame	SRG1
	Eccentric Braced Frame (EBF)	SRG1
	Concentric Braced Frame (CBF)	SRG1
	Buckling Restrained Braced Frame (BRB)	-
Concrete	Shear wall	SRG1
Concrete	Moment frame	SRG1

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.

PROJECT OVERVIEW

Title: Identification and Mitigation of Nonductile Concrete Buildings

Client: Federal Emergency Management Agency (FEMA)

PROJECT SUMMARY

The primary objective of this task order was 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.

On this project, the technical approach will involve: (1) the managed participation of highly qualified consultants specializing in the seismic assessment and upgrade of nonductile concrete buildings; (2) the conduct of work in a collaborative and consensus-oriented process; (3) the preparation of concise, state-of-the-art, user-friendly reports documenting currently available sources of information on identification and risk classification of older concrete buildings, and (4) the results of analytical studies in this project to identify high risk building characteristics.

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

This task involved reviewing and advancing work performed by others 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.

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

This task required coordination with ongoing research in this area, including: (1) the NSF/NEES Grand Challenge research project; (2) the Earthquake Engineering Research Institute (EERI) Concrete Coalition; (3) the NIST/BSSC study to identify concrete building subtypes; and (4) the NIST-funded ATC-76-5 Project. Recommended project participants have been selected with this coordination in mind. A basic building prototype will be identified that represents an older concrete building without deficiencies that are currently identified as collapse indicators. The performance of this building will represent the baseline collapse risk against which the influence of various deficiencies will be measured. In addition, two to four deficiencies (e.g. weak story, shear critical column, etc.) previously identified as significant in other projects, will be selected for the pilot study.

Subtask 1.2 – Conduct Problem-Focused Analytical Studies to Test and Prioritize Deficient Building Characteristics

This task involved the conduct of analytical studies in accordance with FEMA P695 Quantification of Building Seismic Performance Factors to determine the collapse risk of the basic building prototype. The basic building prototype then will be modified to incorporate a previously identified deficiency; the severity of this deficiency will then be varied to study the resulting changes in collapse risk. This study is intended to be completely coordinated with the overall Program Plan of NIST/ATC 76-5 although it only addresses a portion of that plan. The analysis work is intended to satisfy the pilot study described in Task 1.4 of the NIST/ATC 76-5 Program Plan and to identify several collapse indicators as described in Task 2.1 of that plan. Several tasks of the NIST/ATC 76-5 Program Plan that are needed to obtain the comprehensive results envisioned are not needed for the conduct of this study. For example, this study does not include Task 1.1 of the Program Plan (Identification of critical deficiencies) because sufficient deficiencies are already identified for this pilot study. Task 1.2 (Selection of building prototypes) will be partially accomplished with selection of the basic building prototype. Task 1.3 (Identification of ground motions and component models) is not needed for the pilot study because adequate sets of ground motions and component model exist to perform a pilot study.

Subtask 1.3 – Develop Building Evaluation Rules in Accordance with Conclusions of Subtask 1.2.

This task utilized 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). Evaluation procedures will be developed only for the deficiencies studied in Subtask 1.2.

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

Preparationand publication of ATC-78 technical report was completed (December 2011).

PROJECT OVERVIEW:

Title: Development of Industry Foundation Classes (IFCs) for Structural Concrete Components - Strategic Plan

Client: ACI Foundation

Status: Completed

PROJECT SUMMARY:

This project seeks to develop a strategic plan for the development of Industry Foundation Classes (IFCs) for Structural Concrete Components to foster interoperability between disparate Building Information Modeling (BIM) software platforms. This is the initial step in the creation of an extensive suite of interoperable attributes for the IFC exchanges of structural concrete components. The strategic plan will synthesize the state of the art of current IFC interoperability and prioritize the attribute exchanges that would most benefit the industry. This research is designed to support the goal of creating advance tools and methods in the interoperability and building information modeling arena.

The results from the research effort will be documented in a comprehensive report that describes current state of the industry, attribute exchange priorities, and a strategy for implementing effective IFC exchanges. The document will present a possible vision for concrete IFC exchanges and a set of goals and strategies for implementation by incorporation into the evolving National Building Information Model Standards (NBIMS). In addition, it will describe the findings of the feasibility study on encouraging utilization by the design and construction community.

A presentation containing an introduction to the project can be obtained here.

Task 1: Strategic Planning Research

An assessment of the current state of the industry and opinion of industry participants, design professionals, suppliers and builders has been compiled. This information is derived from:

The recent Strategic Development Council (SDC) BIM survey. The Strategic Development Council is a council of the ACI Foundation.
Telephone interviews conducted industry professionals to gain insight and industry perspective on the needs and opportunities that interoperability can achieve. A summary of the interviews is also available.
Concrete domain survey prepared by Chuck Eastman and Pete Carrato for Tekla, which Tekla has agreed to release to the public domain.

A white paper has been produced aggregating this research and laying out a broad structure for the project group to discuss and evolve at the Strategic Planning Session.

Task 2: Strategic Planning Session

The strategic planning session will bring together professionals and industry representatives in a forum to foster discussion, solicit input and gain support for industry initiatives for concrete BIM interoperability. The strategic planning session will consist of an assortment of plenary and break-out meetings to coalesce ideas into strategic initiatives. The session was held on May 5th and 6th, 2010, in Kansas City, in conjunction with SDC session #27. The report from this session can be viewed here (7MB pdf file).

Task 3: Strategic Plan Report

The strategic planning research and the group session was used to develop a Strategic Work Plan. This report highlights the state of the industry and portray a vision for increasing interoperability through the use of IFCs. The exchange attribute priorities are clearly defined and a direction is offered for achieving interoperability through IFC implementation. The Strategic Plan for Development of IFCs for Structural Concrete is available for download here (5.8MB pdf file).

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