RAPID: Assessing the Performance of Elevated Wood Buildings, including Manufactured Housing, in Florida during 2018 Hurricane Michael

这项快速反应研究拨款(RAPID)将调查飓风迈克尔期间高架工地建造和制造的房屋的风力性能，迈克尔于2018年10月10日登陆佛罗里达州，仅比5级飓风低几英里每小时(英里/小时)。这是自1992年安德鲁飓风以来袭击美国大陆的最强飓风。观察到的迈克尔飓风的影响为调查高架现场建造和制造的房屋的风力性能提供了一个独特而重要的机会，因为在海岸和更远的内陆，记录到的风速达到并超过了设计风速。佛罗里达州拥有全美最大的人造住房库存之一，这是最容易受到飓风影响的住宅结构，也往往是社会上最脆弱的家庭的住所。虽然在重大飓风事件发生后，人们普遍注意到人造房屋的损坏，但这种类型的结构只得到了很少的研究关注。人造房屋是高架房屋的一个子集，在受飓风迈克尔影响的地区，高架现场建造的房屋也很常见。高程高度、高架分布和基础类型对高架现场建造和制造的房屋结构所经历的风荷载和破坏的影响目前尚不清楚。该项目将通过收集飓风迈克尔后高架房屋性能的短暂数据来调查这些基本知识差距。重大飓风事件后造成的灾害损失中，住房损失往往占到一半，尽管家庭流离失所造成了广泛的破坏。这项研究的结果将与国家和州一级的规范和标准委员会分享，以提高普通但未得到充分研究的住宅楼的弹性，以促进飓风事件后国家福利和繁荣的连续性。通过这笔赠款收集的数据将在NHERI数据仓库和侦察门户网站(https://www.DesignSafe-ci.org))上共享，供工程界广泛使用。飓风迈克尔风场的内陆风速范围很大，因此为现场调查不同类型的住宅建筑结构提供了机会，包括高架现场建造和制造的房屋。目前的规范和标准没有考虑高架住宅楼下的气流。初步研究表明，不同的海拔高度会放大墙面和屋顶表面测量的风压，这表明当前基于规范的设计方法不保守。这项快速裁决将评估一系列高架和非高架房屋的损坏情况，并根据飓风迈克尔期间经历设计水平和更高风速的地区的海拔高度、支柱分布和基础类型进行比较。此外，受迈克尔飓风影响地区的人造房屋设计用于II区(100英里/小时)或III区(110英里/小时)的峰值风速，以及用于高速公路/州际公路运输的75英里/小时的持续风速。目前设计中使用的大多数风荷载考虑三秒阵风风速，这是一种瞬时风荷载，假定结构构件和材料性能在极端风事件期间保持在线性范围内。在风速维持在每小时75英里或更低的现场检查人造外壳的损坏情况，将有助于进一步了解故障是否由疲劳引发，由持续的风载引起，并进展为机组的灾难性故障。这些获得的知识将指导未来人造房屋研究的重点，为人造房屋的翻新(旧)和设计(新)制定更好的损害缓解计划。侦察小组将进入佛罗里达州受迈克尔飓风影响的地区，收集现场数据，包括破坏图像和建筑信息，用于分析和提高高架现场建造和制造房屋的基本知识。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This Grant for Rapid Response Research (RAPID) will investigate the wind performance of elevated site-built and manufactured housing during Hurricane Michael, which made landfall in Florida on October 10, 2018, just a few miles per hour (mph) below a Category 5 hurricane. This hurricane was the strongest to hit the continental United States since Hurricane Andrew in 1992. The observed impact of Hurricane Michael presents a unique and important opportunity to investigate the wind performance of elevated site-built and manufactured housing, given that recorded wind speeds reached and exceeded design winds at the coast and further inland. Florida has one of the largest inventories in the United States of manufactured housing, the most vulnerable residential structure to hurricanes, which also often houses the most socially vulnerable households. While damage to manufactured housing has been widely noticed following major hurricane events, this type of structure has received minimal research attention. Manufactured housing is a subset of elevated housing, where elevated site-built homes are also very common in the areas impacted by Hurricane Michael. The influence that the elevation height, stilt distribution, and foundation type have on wind loading and damage experienced by elevated site-built and manufactured housing structures is presently unknown. This project will investigate these fundamental knowledge gaps through ephemeral data collection of the performance of elevated housing following Hurricane Michael. Damage to housing is often responsible for half of the disaster losses following major hurricane events notwithstanding the widespread disruption it causes through household dislocation. Findings from this study will be shared with national and state-level codes and standards committees to improve the resilience of common, but understudied, residential buildings, in order to promote continuity in national welfare and prosperity following a hurricane event. Data collected through this grant will be shared on the NHERI Data Depot and Reconnaissance Portal (https://www.DesignSafe-ci.org) for broad use by the engineering community.The Hurricane Michael wind field had a wide range of inland wind speeds, and thus presents the opportunity for on-site damage investigation of different types of residential building structures, including elevated site-built and manufactured homes. Current codes and standards do not account for the air flow that occurs underneath elevated residential buildings. Preliminary research has shown that different elevations could amplify the wind pressures measured on the wall and roof surfaces, suggesting unconservatism in current code-based design approaches. This RAPID award will assess damage to a range of elevated and non-elevated homes, and make comparisons based on elevation height, stilt distribution, and foundation type in areas that experienced design-level and higher wind speeds during Hurricane Michael. Furthermore, manufactured homes in the Hurricane Michael impacted areas are designed for either Zone II (100 mph) or Zone III (110 mph) peak wind speeds, as well as for 75 mph sustained wind for transportation on highway/interstate purposes. Most wind loads used in design currently consider three-second gust wind speed, which is an instant wind load that assumes structural component and material behaviors stay in the linear range during an extreme wind event. Examining damage to manufactured housing at the sites where wind speeds were sustained at 75 mph or less will advance missing knowledge on whether failures are initiated by fatigue, caused by sustained wind loads, and progress into catastrophic failure of the unit. This gained knowledge will direct future research foci for manufactured housing studies to have better damage mitigation plans for both retrofit (old) and design (new) of manufactured homes. The reconnaissance team will enter areas in Florida affected by Hurricane Michael and collect on-site data, including images of damage and building information, for analyses and advancement of fundamental knowledge on elevated site-built and manufacturing housing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.