Overview
Performance-based design approaches for seismic engineering have been used for buildings on the West Coast of the United States and in many seismically active regions internationally for several years. The performance-based seismic design (PBSD) use is predominately focused on tall buildings and retrofit of existing buildings. The acceleration of the PBSD approach, including the acceptance of the methodology with authorities having jurisdiction (AHJs), was the result of significant research and development of industry guidance in such documents as PEER/TBI, “Guidelines for Performance-Based Seismic Design of Tall Buildings”; LATBSDC, “An Alternative Procedure for Seismic Analysis and Design of Tall Buildings Located in the Los Angeles Region”; PEER/ATC 72-1; and ASCE 41-13. As the development of PBSD analysis and modeling techniques became better defined, additional guidance from the material-specific codes and standards was needed. For the design of reinforced concrete structures, guidance for PBSD has been incorporated into Appendix A of ACI 318-19.
While performance-based wind design (PBWD) is seemingly a natural extension of the overall PBSD framework, PBWD has been used for only a limited number of tall buildings outside of the United States, a few specific cases in the United States for existing building structures (for which prescriptive, code-based design methods would require more extensive and expensive modifications), and a tower now under construction in Austin, Texas. Designers may be reluctant to use PBWD because:
- They perceive a lack of sufficient research and guidance;
- They do not perceive a benefit in comparison with PBSD, which leverages a larger degree of inelasticity; or
- They are not familiar with the dynamic response characteristics associated with wind loads.
However, the potential benefits of PBWD include a more efficient and effective structural design by allowing modest levels of nonlinearity; a more direct evaluation of reliability and performance targets; and improved overall building design as a result of the rigorous consideration of serviceability, strength, and stability.
A catalyst is needed to accelerate the use and acceptance of PBWD, and that catalyst has arrived in the form of ASCE/SEI, “Prestandard for Performance-Based Wind Design,” (ASCE Prestandard) supported by ASCE, SEI, the Charles Pankow Foundation, the ACI Foundation, AISC, the MKA Foundation, and FEMA.
With the release of the ASCE Prestandard, the material standards have an opportunity to address material-specific issues related to PBWD. The behavior of concrete elements subjected to many cycles of modest yielding is a unique aspect that ACI will need to address. There are two coordinated efforts underway to address this need between ACI Committee 375, Performance-Based Design of Concrete Buildings for Wind Loads, and ACI Subcommittee 318-W, Wind Provisions. ACI Committee 375 has engaged in supporting efforts to determine needs and prioritize future research regarding concrete design for PBWD. ACI Subcommittee 318-W has formed to develop a new Code Appendix to provide design provisions, complimentary to the ASCE Prestandard, to be included in ACI 318-25.
