Multihazard Performance and Design of Ecoroofs

在过去的十年里，“绿色屋顶”或更广泛地说，生态屋顶在美国的激增，从根本上扩展了屋顶的历史功能。Ecoroofs提供了提供环境、经济和社会效益的新机会。然而，与传统系统相比，生态系统承载着更高的重力载荷，必须支持长时间的瞬时流体载荷。屋顶设计需求的这种转变已经超过了建筑规范和法规，更重要的是，超出了我们对这些非传统荷载下屋顶结构行为的基本理解。令人遗憾的是，传统工程设计的屋顶占了不成比例的大量结构故障，自1990年以来，一家保险公司的损失超过10亿美元。为了确保这些相对“敏感”的结构部件的结构安全性和适用性，需要进行适当的生态植物设计，以解决以下三个关键问题：1.在地震引起的屋顶震动下，植物生态材料是否会动员起来？种植材料的生态化程度与结构的耦合程度如何？地震后屋面静载不平衡能预见吗？2.在降雨期间，对生态系统产生的负荷效应是什么？在什么时间尺度上？如何在生态沟中分配荷载？传统的设计方法能否确保池塘的稳定性和防止超载？3.典型的生态沟种植材料的工程特性是什么？在地震和降雨事件中，哪些属性对实现生态恢复性能最为关键？本项目是第一个研究结构、岩土和植物相互作用对生态恢复抗震性能影响的项目。研究的重点是系统响应，以说明设计要素之间的重要相互作用。将开发一个生态圈结构模拟器来测试全尺寸的实验室生态圈原型，并将与现场调查和组件实验室数据相结合，以产生关于屋顶流体-结构相互作用的新知识，包括：横向震动中种植材料的移动性、保水和排水特性以及长期使用性能。这些将为制定地震区生态设计的结构指南提供背景材料。

The proliferation of "green roofs" or more generally, ecoroofs in the United States has increased dramatically in the last ten years and has radically expanded the historical function of a roof. Ecoroofs offer new opportunities to provide environmental, economical, and social benefits. However, ecoroofs carry higher gravity loads and must support long-duration transient fluid loading compared to traditional systems. This shift in roof design demands has outpaced building codes and regulations, and more importantly exceeded our fundamental understanding of roof structural behaviors under these nontraditional loads. Regrettably, conventionally engineered roofs account for a disproportionately large number of structural failures with over $1 billion in damages since 1990 for a single insurer. Proper design of ecoroofs to ensure structural safety and serviceability of these relatively "sensitive" structural components requires research to address these three critical questions: 1.Under earthquake induced roof shaking, does the ecoroof planting material mobilize? To what degree is the ecoroof planting material coupled to the structure? Can roof dead load imbalances be expected after an earthquake?2.During rain events, what are the load effects produced on ecoroofs and over what time-scales? How loads are distributed in ecoroofs and will traditional design approaches ensure ponding stability and prevent overloading? 3.What are the engineering properties of typical ecoroof planting materials? Which properties are most critical to achieving ecoroof performance during seismic and rain events?This project is the first to examine the structural, geotechnical, and planting interactions on ecoroof seismic performance. The research focuses on system response to demonstrate the important interactions of the design elements. An ecoroof structural simulator will be developed to test full-scale laboratory ecoroof prototypes and will be integrated with field survey and component laboratory data to produce new knowledge on fluid-structure interaction at the roof including: planting material mobility during lateral shaking, water retention and drainage characteristics, and long-term service performance. These will provide background material for development of a structural guide for ecoroof designs in seismic zones.