Facilitating the Use of the PEER PBEE: Methodology in Engineering Practice - 1292005

Project goals and objectives

This project is an essential element of the Building Packaging/Outreach Program, whose objective it is to communicate the PEER methodology to the users and to facilitate the use of the methodology in engineering practice. Its focus is on a simplified PBEE approach and on documentation of the PBEE methodology and its components.

Role of this project in supporting PEER's mission (vision)

The focus of the PEER research program on buildings during this year and next year is on the areas of: (a) benchmarking the PBEE methodology on code-conforming structures, (b) decision making based on anticipated performance, and (c) outreach and packaging the PBEE methodology. The focus of this project is on the second and third areas. Advantage is taken of the work performed in parallel in the benchmarking effort, and of the past work performed in the Van Nuys test bed study and in several other related projects.

Methodology employed

We have synthesized methods and tools developed by PEER researchers into a simple format that greatly facilitates the implementation of the PEER PBEE methodology in engineering practice. Much effort was devoted to the development of a graphical tool that facilitates Performance-Based Design (PBD) in engineering practice. This graphical tool is also capable of performing performance assessment in a simplified manner. The tool translates the deep yet complex equations used in probabilistic performance assessment into a graphical format that facilitates utilization in conceptual design decision making. An essential part of this tool is a database of IM-EDP response curves for generic structures. Such a database has been developed for generic moment-resisting frames and shear walls covering a large practical range of structural properties. As a side product, the sensitivity of different structural response parameters to variations of a number of structural parameter is evaluated and documented. Summary documents will be written that comprise the essentials of the complete performance assessment methodology, and additional user-oriented documents will be developed with a focus on the domain expertise of the PI, i.e., they will emphasize the structural engineering aspects of the PBEE methodology.

Brief Description of previous year's achievements, with emphasis on accomplishments during last year (Year 8)

During the last two years we have developed a simplified procedure for performance-based design and assessment that incorporates three domains: the hazard domain, the structural domain, and the loss domain, with an emphasis on the mean values of the ground motion intensity (IM), building response (EDP), and losses DVs (Figure below). This simple PBD procedure helps engineers make decisions on global structural parameters (e.g., base shear strength and period) and the choice of an effective structural system and material (e.g. steel moment-resisting frame or concrete shear wall), based on performance targets that are defined upfront (e.g., acceptable average monetary loss at discrete hazard level, and tolerable average annual probability of collapse). The simplicity of the proposed PBD approach and its semi- graphical presentation provide engineers with an insight about the contribution of different building subsystems to the building total loss.

An additional advantage of this simplified PBD process is that it can be used as a performance assessment approach by reversing the flow of information from ground motion hazard to loss estimation. Special consideration is given to design for collapse prevention for the life span of the structure. We have also developed a consistent way for incorporating different sources of uncertainty (aleatory and epistemic) in the proposed approach for collapse safety.

An essential backbone of the simplified PBD procedure is the information incorporated in the Structural System Domain in the form of mean IM-EDP curves and collapse fragility curves for various design alternatives. A comprehensive database of IM-EDP curves and collapse fragility curves for generic moment-resisting frames and shear walls covering a large practical range of structural parameters was developed during the past year. Sensitivity of various building response parameters to variation of these structural parameters was studied. The conclusions obtained from this sensitivity analysis provide insight about the effect of different structural parameters on building response. This is an essential ingredient needed for performing a conceptual performance-based design.

Other similar work being conducted within and outside PEER and how this project differs

Development and implementation of PBEE concepts have become a priority for research and practice in many countries, as documented in the proceedings of the International Workshop on Performance-Based Design – Concepts and Implementation, held in Bled, Slovenia, in June 2004. At this workshop it became clear that different countries are pursuing different approaches to PBEE, but that the PEER PBEE approach has matured much more than approaches pursued in other countries.

Describe any instances where you are aware that your results have been used in industry

The SAC (Scientific Advisory Committee) identified communication of the PEER PBEE methodology to the profession as the highest priority for the PEER Years 9 and 10 activities. This project addresses this priority and will develop documents intended to encourage adoption of PBEE in engineering practice. Currently, the ATC-58 and ATC-63 projects incorporate components of the PEER methodology.

Expected milestones & deliverables

The following products will be the deliverables of the Year 9 study:

• - A set of short documents that will provide guidance in carrying out a performance assessment
• - A comprehensive document summarizing the process and data for simplified approaches to performance assessment
• - A comprehensive document summarizing data and criteria that can form the basis for performance-based seismic design
• - Interaction with ATC-58 for consideration of the PEER methodology in code development
• - Interaction with ATC-63 in the utilization of the collapse fragility approach developed in this project and a previous PEER project.
• - Assessment of the utility of the PEER PBEE methodology for protocol development for experimentation and data collection, in the context of NEES and ATC-58.