Collaborative Research: A Resilience-based Seismic Design Methodology for Tall Wood Buildings

随着美国城市社区人口的持续增长，对8到20层的高层住宅和综合用途建筑的需求持续增加。在这个高度范围内的建筑通常是用混凝土或钢建造的。最近在西欧开发了一种新的木材结构创新，称为交叉叠层木材(CLT)，目前正在世界各地实施，作为高层建筑传统结构材料的可持续和低碳足迹替代方案。然而，目前还没有一个公认的、经过验证的高层CLT建筑抗震设计方法，因此这些高层木结构建筑在美国的建设受到了限制。这项研究将通过研究弹性高层木结构建筑的抗震设计方法来打破这一障碍，这种建筑可以在设计级地震后立即重新占用，并在大地震后快速修复(与当前的建筑系统相比)。使用本项目中开发的抗震设计方法，研究团队将与工程和建筑界的从业者合作，通过在利哈伊大学由美国国家科学基金会(NSF)支持的自然灾害工程研究基础设施(NHERI)实验设施进行全尺寸装配系统测试，然后在加州大学圣地亚哥分校由NSF支持的NHERI室外振动台进行全尺寸测试，来设计、建造和验证一座十层木结构建筑的性能。这项研究将实现一种新的具有成本竞争力的可持续建筑实践，从而增加对工程木材生产的需求，为森林资源提供附加值，并促进建筑和林业部门的就业增长。作为研究的一部分，实验项目将致力于向公众和利益相关者提供与地震减灾、现代木材工程和弹性建筑概念相关的问题。本研究的目标是调查和验证结合高性能结构和非结构系统的高层木结构建筑的抗震设计方法。该方法将从数量上考虑建立复原力的问题。这将通过计划在四年内完成的一系列研究任务来实现。这些任务将包括使用几种后张张拉摇摆CLT墙系统的高层木结构建筑的力学模型，影响弹性的结构和非结构建筑构件的易损性建模，建筑组件系统的全尺寸双向测试，基于弹性的抗震设计方法的发展，最后是一系列10层CLT建筑试件的全尺寸振动台试验，以验证所研究的设计。所研究的结构体系将包括整体和分段摇摆配置的后张法CLT摇摆墙。在一个完整的建筑系统中实施分段摇摆墙将是一个变革性的概念，尚未在物理上实现。摇摆墙系统将在整体建筑行为的背景下进行研究，包括重力系统和非结构构件。研究小组将进一步推动现有基于性能的抗震设计的界限，制定一种设计程序，明确考虑建筑物在地震后恢复功能所需的时间。利用NHERI实验设施提供的大规模测试能力，设计方法将得到实验验证，同时将生成动态载荷下高层木结构建筑的里程碑式数据集，通过NHERI DesignSafe-ci.org Data Depot提供给更广泛的研究和从业者社区。该项目将通过与太平洋西北部对高层CLT建筑感兴趣的从业人员密切联系，促进这一新结构原型的实施，作为一种具有成本竞争力的设计选择。研究生和本科生，包括社区学院的学生，将积极参与这项研究，并获得宝贵的知识和经验，这将为他们成为使用现代工程木材材料的可持续建筑实践的领导者做好准备。

As the U.S. population continues to grow in urban communities, the demand for tall residential and mixed-use buildings in the range of eight to twenty stories continues to increase. Buildings in this height range are commonly built using concrete or steel. A recent new timber structural innovation, known as cross laminated timber (CLT), was developed in western Europe and is now being implemented around the world as a sustainable and low carbon-footprint alternative to conventional structural materials for tall buildings. However, an accepted and validated design method for tall CLT buildings to resist earthquakes has not yet been developed, and therefore construction of these tall wood buildings in the United States has been limited. This research will break this barrier by investigating a seismic design methodology for resilient tall wood buildings that can be immediately re-occupied following a design level earthquake and quickly repaired (compared to current building systems) after a large earthquake. Using the seismic design methodology developed in this project, the research team will work with practitioners across the engineering and architectural communities to design, build, and validate the performance of a ten-story wood building by conducting full-scale sub-assembly system testing at the National Science Foundation (NSF)-supported Natural Hazards Engineering Research Infrastructure (NHERI) experimental facility at Lehigh University, followed by full-scale tests at the NSF-supported NHERI outdoor shake table at the University of California at San Diego. This research will enable a new sustainable construction practice that is also cost-competitive, thereby increasing demands for engineered wood production, providing added value for forest resources, and enhancing job growth in the construction and forestry sectors. As part of the research, the experimental programs will serve to provide outreach to the public and stakeholders on issues related to seismic hazard mitigation, modern timber engineering, and resilient building concepts.The goal of this research is to investigate and validate a seismic design methodology for tall wood buildings that incorporates high performance structural and non-structural systems. The methodology will quantitatively account for building resilience. This will be accomplished through a series of research tasks planned over a four-year period. These tasks will include mechanistic modeling of tall wood buildings with several variants of post-tensioned rocking CLT wall systems, fragility modeling of structural and non-structural building components that affect resilience, full-scale bi-directional testing of building sub-assembly systems, development of a resilience-based seismic design methodology, and finally a series of full-scale shake table tests of a ten-story CLT building specimen to validate the investigated design. The structural systems investigated will include post-tensioned CLT rocking walls in both monolithic and segmental rocking configurations. Implementing segmental rocking walls in a full building system will be a transformative concept that has yet to be realized physically. The rocking wall systems will be investigated under the context of holistic building behavior, including gravity systems and non-structural components. The research team will further push the boundary of existing performance-based seismic design by developing a design procedure that explicitly considers the time needed for the building to resume functionality after an earthquake. With the large-scale testing capacity provided by the NHERI experimental facilities, the design methodology will be experimentally validated, which will at the same time generate a landmark data set for tall wood buildings under dynamic loading that will be available to the broader research and practitioner community through the NHERI DesignSafe-ci.org Data Depot. The project will facilitate implementation of this new structural archetype by interfacing closely with practitioners in the Pacific Northwest interested in tall CLT buildings as a cost-competitive design option. Graduate and undergraduate students, including community college students, will actively participate in this research and gain valuable knowledge and experience, which will prepare them to become leaders in sustainable building practices using modern engineered wood materials.