In a long-awaited, historic step toward “real" not cookbook wind engineering, the Structural Engineering Institute of the American Society of Civil Engineers recently issued a recommended alternative to the building code’s prescriptive procedures for the wind design of buildings. Properly implemented, the Prestandard for Performance-Based Wind Design, available free of charge for all structural engineers to use, results in buildings capable of achieving wind performance objectives specified in the ASCE 7 design load standard, and in many cases, superior performance, according to SEI.

“这是重要的,”斯科特说,一名高级公关incipal with PCS Structural Solutions and chair of the wind loads subcommittee for ASCE 7’s standard, Minimum Design Loads and Associated Criteria for Buildings and Other Structures. “It allows us to use the reserve capacity in structures,” adds Scott, also the principal investigator for the research project that developed the 127-page prestandard, catalyzed by a $150,000 grant from the Charles Pankow Foundation.

Innovation

The document, which mandates peer review for all structures engineered using PB methods, will allow greater scope for innovation in structural and building envelope design for wind, say the members of the document’s reliability peer review team, which reviewed reliability research done by Seymour Spence at the University of Michigan. It also will result in more efficient use of building materials, while still meeting accepted levels of safety and functionality.

Scott says members of the ASCE 7 wind loads subcommittee have been talking about PBWD for many years. It took the Pankow foundation, which committed half the funds and raised the other half from the American Concrete Institute Foundation, the American Institute of Steel Construction, the ASCE Leadership Council and the MKA Foundation, to turn talk into action. The U.S. Federal Emergency Management Agency provided additional financial or in-kind support.

“Without Pankow foundation funding, we would not have been able to produce the document,” says Scott.

Prestandard是由由13位专业人员组成的委员会创建的，研究，研究，风洞测试，教育和政府。可靠性团队和一般同行评审团队都对其进行了同行评审。它概述了主要的设计创新，包括针对风设计的非线性动态分析，抗风力系统的指定元素中有限的非弹性，基于系统的性能标准和建筑信封的增强设计标准。

Resolve Conflicts

The document also addresses a need, identified by designers, for a methodology to use when buildings are subjected to both wind and seismic events. “The prestandard has been developed to help resolve conflicts in performance objectives that exist when using prescriptive procedures for the wind design and performance-based procedures for the seismic design of individual buildings,” says the executive summary.

To develop the PBWD prestandard, Scott and his team followed the template for the ASCE/SEI PB seismic design standard, which is widely used. “We relied a lot on research in seismic design to create the prestandard,” says Scott.

Peter Irwin, senior technical director and past president of wind engineer, RWDI, and a member of the prestandard’s reliability peer review team, says, “I support PBD for wind, having participated in its application in the case of an older building that was being reevaluated against the current prescriptive code.”

Irwin说，旧建筑无法满足现代风码的简单规定标准，这些标准要求该结构保持在弹性范围内，直到最终的设计风速。自2000年代初以来，这也是ASCE/SEI风风委员会的投票成员的Irwin补充说，它必须被拆除。

欧文说，但是PBWD允许对弹性范围之外的历史结构进行分析，如地震设计，并显示主要结构具有足够的结构强度储备，不需要拆除。

The PBWD document introduces design innovations that require additional studies to build a body of knowledge related to its application and to support its acceptance and approval as an ASCE/SEI standard. Consequently, the prestandard takes a conservative approach to design, says Scott.

To date there have been only 15 or 20 structures designed for wind using the required nonlinear time-history analysis. There need to be hundreds to fully determine the reliability of the methodology, adds Scott.

标准

It could take three years to collect the data required for a full standard and another three to develop the standard, which is expected by about 2025. SEI is preparing a white paper to discuss the research needs to develop a full standard.

Meanwhile, to familiarize engineers with the methodology, Scott will present a session on advances in PB wind engineering at the annual ASCE/SEI Structures Congress, next April 5-8, in St. Louis. There will also be articles in Structure Magazine.

此外，ASCE 7-22风负载小组委员会将制定和投票提案，以将Prestandard引用到2022年ASCE 7的评论中。地震PBD的起源，我们可以在ASCE评论中引用这个Prestandard。他补充说：“这样做为设计师提供了首选。”