首先并不容易。但这并没有阻止一位勇敢的冒险家与结构实践的主要风相抵触，以降低成本，这是摩天大楼工程的动态转变，这最少有望改善高大的建筑韧性和可持续性。激进技术的第一个称为基于性能的风设计的概念证明正在为致力于推进“真实”而不是“食谱”工程的高个子爱好者激发乐观的风暴。他们预测，在10或15年内，高层PBWD将成为全世界的常态。

PBWD被结构工程师称为“变革性”，该方法在奥斯丁的671英尺高度项目上首映。“ PBWD在一个真实项目上的首次实施是该行业展示该技术的可行性和利益的重要一步，” Magnusson Klemencic Associates（MKA）高级负责人Sean P. Clifton说，卖出的结构工程师是售出的结构工程师。自1月以来，正在建设奥斯汀塔的代码开发商的新颖策略。

PBWD is the “future” for towers 400 ft or taller, Clifton adds. To encourage other high-rise designers to follow in its footsteps, the team for the 58-story 321 West 6th Street job is sharing its lessons learned.

The technique is the rigorous evaluation of explicit performance objectives for occupant comfort, serviceability and safety. As with the established performance-based seismic design (PBSD) for tall buildings, the wind engineering method minimizes materials and reduces the carbon footprint compared to a cookbook design.

这座561,000平方英尺的建筑在底座上停车，上面是一个办公楼和一个住宅塔楼（渲染，左），具有相对简单的几何形状，这使其成为第一个PBWD高层建筑的良好候选人。
Rendering courtesy Handel Architects/Neoscape

PBWD还可以增加可观的空间或收缩建筑物的占地面积。它有可能减少基础材料的数量并缩短施工时间表。

作为第一个例子，奥斯汀的设计有意保守。克利夫顿预测未来塔楼的节省的两倍。仅使用结构优化，就可以进一步磨练该技术可以将碳减少12％或更高，而无需挖掘材料本身的体现碳含量。这一切都取决于建筑物，其位置和PBWD的微调。

the 561,000-sq-ft Austin tower, PBWD reduced the cost of the reinforced concrete structure by 5% and reduced embodied carbon by 6%, compared with the conventional design MKA executed in parallel, in case the PBWD didn’t pan out.

解锁工程自由

“While some might say performance-based seismic design, wind design and structural fire design are the most important developments in structural engineering in the last century, I believe the most important development is the courage and tenacity of today’s structural engineers to venture beyond the prescriptive limits of the building code. With the sound underpinning of science and physics and a return to the first principles of engineering, a whole new generation of more resilient and sustainable buildings is coming. It is truly an exciting time working with these new freedoms we have unlocked!”

- Ron Klemencic，2018年新利luckENR卓越奖得主

Engineers predict PBWD will, in 10 or 15 years, replace prescriptive design and static wind tunnel design for high-rises, thanks to the prestandard and the first PBWD structure underway in Austin.
图片由MKA。
*Click on the image for greater detail

基于性能的风设计结构的外观与规定设计没有什么不同。无论哪种方式，奥斯汀塔都将具有钢筋混凝土剪力墙芯，并带有覆盖仪到外线柱（蓝色）。
图片由MKA。
*Click on the illustration for greater detail

The technique trimmed the volume of concrete in the core’s shear walls by 1,800 cu yd, or 5%, of the total concrete volume. It also shaved 6 in. off the core walls’ 3-ft thickness. PBWD cut 350 tons, or 10%, of the reinforcing steel and 125 tons, or 250%, of the embedded steel beams in the core, which will contain only 50 tons.

MKA希望奥斯丁的例子能引发趋势。MKA的董事长兼首席执行官Ron Klemencic说，选择遵循其领先优势的竞争对手不仅会为客户提供更高效的设计，而且将大大减少具体的碳。”他还是Charles Pankow建筑研新利luck究基金会的主任（ENR 4/19-16/18p。34），他还是为提高建筑质量，安全性和速度提高建筑质量，安全和速度的时代以提高建筑质量，安全性和速度的时代，以提高建筑质量，安全性和速度的时代（ENR 4/19-16/18p。34），他还是2018年ENR奖的卓越奖。。

早在净零碳即将到来之前，PB设计对Klemenccic很重要。他说：“ PBWD的商业实施标志着将结构工程归还科学，物理和数学实践的下一个主要里程碑，而不是盲目地遵循规定的代码要求。”

Klemencic predicts that in a decade, PBWD will be the standard of care for tall buildings in regions of high wind demand. The impact on the built environment will be tenfold or more than that of PBSD, he says.

Viral Patel, director of design for structures at Walter P Moore (WPM) and the Austin tower’s structural peer reviewer, thinks PBWD will be the “standard way of engineering tall buildings in 10 to 15 years.”

计算模拟显示，当风流接近建筑物的面（右蓝线）时，风流速度正在减慢，拐角处的速度更快（红色和黄色）以及建筑物后面的湍流唤醒。
图形提供的CPP

Challenges Remain

帕特尔说，挑战仍然存在，但有可能改善流程，“绝对可以节省金钱”。他补充说：“第一次有学习曲线。”

The Austin example would never have gained traction were it not for the building’s developers. In pitching the idea, MKA had estimated a 5% to 10% reduction in the cost of structural materials. But without a precedent, there was no guarantee of any savings.

“我们认为收益值得冒险，”奥斯丁工作总承包商瑞安·库斯（Ryan Cos。）的房地产副总裁兼蒂斯曼·斯皮尔（Tishman Speyer）的代码开发商Ryan Cos。

MKA是Tishman Speyer众所周知的，Tishman Speyer开发了工程师在旧金山的第一座PBSD大楼。Tishman Speyer设计与建筑集团高级总监Cynthia Bowden说，在奥斯汀的“我们很高兴”的结果中，将再次走上PBWD路径。

There is a caveat: Tishman Speyer would only consider a PBWD with MKA or its equal and the same consultants for wind engineering and peer reviews.

Tishman Speyer和Ryan拒绝在Austin项目上提供开发或建筑成本，尽管他们说较薄的核心墙将建筑物的足迹在各方的四方面都减少了118luck.cub英尺，这节省了覆层。

开发人员还认为PBWD可能会修剪时间表，因为有较少的材料可以制定。但是，只有挖掘完成，现在还为时过早。在2024年末和2025年初的分阶段完成设置之前，他们会很了解。

MKA用自己的一角钱进行了结构的平行规范设计。但是，即使没有这笔费用，PBWD仍有成本溢价，因为这项工作的数量级要大。

PBWD需要更多的时间进行分析，更深入的风洞测试以及结构和风设计同行评审。有大量数据可以筛选，以确保满足接受标准，并且需要很长时间才能执行分析。

迄今为止，西6街321号奥斯汀市中心的模型是在CPP风洞中唯一测试的PBWD塔。
Photos courtesy CPP

MKA说，尽管如此，这项技术不仅仅是为自己支付。克利夫顿说，即使在奥斯汀塔上，降低的建筑成本也是增加设计费用的十倍以上。

塔楼的建筑师（在底座上都堆叠停车甲板，上面是一个办公大楼，然后是顶部的公寓部分，也支持PBWD对建筑的好处。“这确实是要拥抱的东西，”塔楼设计师Handel Architects的负责人詹姆斯·哈克斯（James Hakes）说。他补充说：“没有理由害怕它。”“与创新的工程师合作为我们提供了更多的创新建筑的机会。”

佩奇（Page）建筑师的校长布兰登·汤森（Brandon Townsend）表示，与MKA和城市建筑官员的批准流程非常成功，以至于Page和MKA正在在一个750英尺高的奥斯汀项目中追求PBWD。

西6街321号is not only the first PBWD tower approved and under construction; it is the first tall building designed, approved and permitted according to the precepts of the Prestandard for Performance-based Wind Design, published by the American Society of Civil Engineers’ Structural Engineering Institute (ASCE-SEI) in 2019, with support from the Pankow foundation, the MKA Foundation and other groups.

The concept of PBWD is not new, but the prestandard for the first time presents a format that structural engineers and building officials can follow, says John Kilpatrick, a member of the prestandard committee and practice area lead in RWDI’s wind engineering group.

RWDI是奥斯汀·乔布斯（Austin）的Wind专家CPP Wind Engineering顾问的同行评审。CPP高级校长和委员会成员Roy Denoon补充说，Prestandard允许“如果您使用批准的统计技术，则允许“如果使用批准的统计技术”。

The document is important, adds Patel, a prestandard peer reviewer. Otherwise, “many engineers could misuse” the process, he says.

而不是重新发明轮子

Prestandard的创建者并没有重新发明轮子，而是使用了已建立的ASCE-SEI高建筑PB地震设计标准的模板。

Starting about 25 years ago, MKA executed its first PBSD towers without any guides or standards. “For better or worse, we just started doing it,” says Klemencic.

In the absence of an accepted methodology, the PBSD pioneer was put through the wringer by reviewers and cautious building officials in California. “A lot of tears were shed over the uncharted course of peer review, process and technology,” says Klemencic. “It was tough.”

The review and approval process improved considerably after the first guidelines came out about a dozen years ago, written based on knowledge gleaned from first-hand experience and the results of laboratory tests of structural members under earthquake loads. Today, PBSD is the norm for tall buildings throughout the world.

“亲眼目睹PBWD对PBSD的巨大积极影响，有望产生更大和更广泛的影响，”克莱米奇（Klemencic）说。

早年的苦难PBSD通知MKA’s polar-opposite strategy to initiate PBWD: “Avoid the bloodshed,” Klemencic says, by engaging the community of peer reviewers and competitors to write the methodology in advance of executing the projects.

Consequently, without a real-world example or any research into the subject, MKA approached ASCE to discuss engaging its already established wind subcommittee for its design load standard, called ASCE 7. The wind engineer and peer reviewers for the Austin project, plus MKA’s wind and seismic subject matter experts, all had a hand in writing or reviewing the prestandard.

事后看来，在MKA腰带的奥斯汀项目中，克莱米奇（Klemencic）对PBWD的“马车前”策略感到遗憾。他说，如果没有构建的例子，则Prestandard包含不清楚的规则，并且比它需要的更具限制。他担心，很难以任何实质性的方式进行修改。

该指南主要是在常见的钢筋混凝土结构上编写的，并带有剪切壁芯，以抵抗横向载荷，类似于奥斯汀建筑物。Klemencic说，设计自由在于其他侧向系统，例如钢制的核心和大型框架。

“The essence of performance-based design has eroded,” Klemencic adds. “PBWD today is no more than enhanced prescriptive design with a different set of rules.”

Research, such as at Washington State University on steel-reinforced link beams (above) and at UCLA on reinforced concrete link beams (below), will advance PBWD.
Photo (above) by Christopher Motter/WSU; Photo (below) by Saman Abdullah/UCLA

定义所需的结果

在PBWD中，工程师考虑了生命安全，生物舒适性和建筑绩效，定义了所需的结果或成就。然后，他们演示了设计符合预期的结果。

“我们没有施加力和计算位移，而是针对可接受的位移水平，从那里计算力，应力，菌株等。”这说明了剪切壁芯的横向系统中的大部分物质节省。

Prestandard通过概述了风力阻力的主要设计创新来指导工程师取得结果。其中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的非弹性有限，基于系统的性能标准和建筑物信封的增强设计标准。

长期以来，非弹性行为一直是地震设计中公认的方法，即使在PBSD之前 - 但不是在风设计中。对于PBWD，非弹性行为的分析更为复杂，因为暴风雨可以持续数小时。地震仅持续10到30秒。

But in a major departure from prescriptive wind requirements, PBWD uses nonlinear response-history analysis to assess inelastic behavior rather than linear analysis to assess elastic, or bounce-back, behavior.

例如，在两种最严重的负载方案中，暴风雨可能每700年或1,700年发生一次，PBWD允许由于建筑物位移或漂移而导致的增强钢或结构钢的可接受的非线性反应或永久变形。。MKA说，少量的屈服并不能以任何方式损害生命安全。

PBWD involves applying actual dynamic wind loads instead of prescribed static loads to the building model in the wind tunnel, which offers a more realistic picture of the building’s behavior under wind. “It allows members that can accommodate inelastic behavior to push the limit,” says WPM’s Patel.

Properly implemented, the prestandard, available free of charge, results in buildings capable of achieving wind performance objectives specified in ASCE 7, and in many cases, superior performance, according to ASCE.

奥斯汀塔团队不仅遵循预标准，还建议根据其经验进行改进。预计到秋季初期是1.1版。Asce说，标准可能会在2025年出现。

Prestandard概述了对奥斯丁有帮助的审查和批准过程。该小组在设计阶段开会了四次以审查：1）设计的基础；2）风洞测试和风载建议；3）初始比例，计算机建模和初始设计；4）非弹性建模和设计。

合作几乎很有趣

The prestandard’s required design-phase engineer-reviewer collaboration is “almost enjoyable,” says RWDI’s Kilpatrick, compared to the often contentious process that typically kicks in after the design is set in stone, when changes are more difficult.

基尔帕特里克说，在奥斯汀的同行评审会议上，有很多辩论和讨论，但是问题得到了解决。“如果我们可以让两名风顾问同意，那么每个人都会感觉更好。”

The prestandard provides three methodologies for PBWD. For the Austin project, MKA selected the first, which is the simplest.

PBWD和并行设计看起来没有什么不同。抗横向力的系统由放置在电梯周围的钢筋混凝土剪力壁和火出口楼梯组成，并补充了一个单层混凝土壁式支撑系统，该系统连接到外围柱，大约三分之二的塔楼。

Floor slabs in the apartments are post-tensioned. Floors in the office and parking levels have post-tensioned beams and slabs. Perimeter columns slope at the amenity levels between the more slender residential tower and the broader office block. Two subgrade parking levels are underlain by concrete drilled shafts into limestone.

MKA’s Clifton pushed for PBWD on the Austin structure because of its relative simplicity. “We see benefits for a more complex structure but it adds a level of complexity” to the engineering, he says.

MKA于2021年初开始在奥斯汀大厦（Austin Tower）上工作，大约是在开始对PBWD进行一些内部研究的三年后。

In April 2021, “MKA raised their hand and walked us through the benefits and risk mitigation” for the novel method, says Ryan’s Knoll.

With only the excavation complete, developers say it is too soon to tell whether there will be construction schedule savings associated with PBWD.
照片由Ryan Cos提供。

Biggest Risk

一个很大的未知是结构性评论是否会延迟佩奇的汤森（Page）所说的“非常激进的”设计时间表 - 九个月而不是更舒适的一年。但是，根据该市建筑官员的说法，这项审查的审查不超过先前提交的高层审查的评论。

2021年5月，在示意图设计期间，MKA与该市联系，并邀请其开发服务部（DSD）成员参加初步的同行评审开球会议。

The city approved the structure under the section of the building code that allows for alternative materials, design and methods of construction and equipment, and under the code’s analysis section, which allows for a rational structural analysis that takes into account equilibrium, general stability, geometric compatibility and both short- and long-term material properties, in accordance with well-established principles of mechanics.

作为a condition of PBWD, the city requested approval letters from the peer reviewers, confirming that the lateral design procedures used were in general conformance with ASCE’s recommendations and its PB design guidelines.

The ongoing collaboration between the design and peer review teams, in tandem with periodic check-ins with the city, allowed the city’s structural reviewers to have “a level of familiarity and understanding of project-specific design processes” not typical of other projects and associated plan reviews, according to DSD.

The city also says it “highly encourages” design teams considering PBWD and any other PB design “to engage the local building official/authority having jurisdiction early and confirm any requirements they may have for alternate methods of compliance.”

Beyond peer review, PBWD requires different and more in-depth wind tunnel tests to provide more specific wind force data to the design engineer.

传统上，在风洞测试中，等效的静态载荷用于结构，而不是动态载荷。在Prestandard中，仅规定了框架。设计本身可以相当流畅，“一旦您了解了以非线性方式行事，” RWDI的Kilpatrick说。

The prestandard allows a site-specific wind-climate analysis if approved statistical techniques are used. Wind-loading time histories are used in PBWD to look at nonlinear behavior of certain elements.

奥斯汀塔是第一个在CPP风洞中经过此过程的建筑。RWDI尚未在其隧道中有PBWD塔。两家公司都不知道正在建造的其他PBWD塔。

ASCE 7-10是奥斯汀的管理标准，但设计团队获得了使用ASCE 7-16的700年重复风速，即108 mph，而不是115英里 /小时。CPP的Denoon说：“如果它是规范性的设计，那么获得许可将更加困难。”

There is an advantage to reduced wind speeds. “If there is a 10% reduction in wind speeds, there is a 20% reduction in pressure,” he adds.

开发人员对PBWD充满信心，但“有兴趣了解建筑物的性能，以及您是否可以说出摇摆或漂移的差异，” Tishman Speyer的Bowden说。

作为回应,MKA说设计目标包括occupant comfort for one- and 10-year wind occurrences; operational performance for the 10-year wind and continuous occupancy for the 700-year wind.

从第一个PBWD工作中，需要更好地管理生成的数据的量，自定义软件和更强大的计算机。MKA的最初连续分析持续了一个月，这威胁了设计时间表。购买的速度更快的计算机将时间减少了三分之一到一半。

MKA说，需要进行更多的研究来确定在不同类型的链路增强中应允许多少非线性响应。正在进行的测试结果将阐明更好的细节，包括在钢制增强的连接梁的风载下的行为，以及将梁与钢嵌入的连接光束。

Klemencic很高兴看到PB设计的成熟，并设想了三种PB方法的混合时期（seismic，Wind和PB结构火灾设计），部分原因是消除了对结构钢上施加的火力阻力的需求，可以提供更好的建筑物。

He says, “PB design opens up a huge range of opportunities for research, development, design and implementation—all resulting in a better, safer, more resilient and lower-carbon future.”