Achieving Sustainable Urban Buildings with Seismically Resilient Mass Timber Core Wall and Floor System

人口密集的城市地区的增长，减少新建筑的碳足迹，以及在灾难性地震后迅速恢复入住率的紧迫性，需要重新审视中高层建筑的结构系统。为了满足这些可持续性和地震弹性的需求，本研究的目标是以一种包括建筑和结构考虑在内的方式实现全木材材料系统。大量木材的利用在提供储存而不是产生碳的建筑物方面具有重要的社会意义，并为该国萧条的木材生产地区增加经济机会。这项研究将集中在核心墙的建筑物，因为这些建筑类型是当代城市中高层建筑中最常见的。开放式地板布局将允许商业和混合用途的占用，但也将包含重大的技术知识差距，阻碍其与大规模木材的实施。制定研究计划是为了通过以下方式填补这些空白：（1）根据多个利益相关者的意见开发合适的中高层原型，（2）进行参数化系统级抗震性能调查，（3）开发新的关键部件，（4）通过大规模实验验证性能，及（5）在现有的教育及外展架构内加入教学单元，以填补业界的资讯空缺。位于木材生产区的中心，多学科团队将利用当地具有木材经验的设计专业社区和波特兰州立大学最近实施的绿色建筑学者计划，提供直接影响周围环境的技术成果。研究成果将在系统性能层面以及关键部件层面上推进知识。研究的建筑系统将包括交叉层压木芯、地板和胶合木结构构件。使用大量木材将在有效实现理想的抗震性能，特别是抗震弹性的目标方面提出挑战。这些挑战将通过核心摇摆与梁和地板相互作用的独特组合在系统层面上得到解决，以实现非线性弹性行为。这种系统性能将消除后张拉以实现重新定心的需要，但将引入可直接影响横向性能的新参数。本研究将研究这些参数对整体建筑行为的影响，并将开发一种方法，设计师可以使用这些参数来战略性地控制建筑物的地震反应。这些关键参数将使用参数数值分析以及大规模的子系统实验进行研究。该系统的关键组成部分之一将是压制，一个设备，连接木材核心的基础，并提供滞后能量耗散。中高层建筑的强度要求和变形要求，沿着与大量木材的整合，将需要在开发这种低损伤组件方面提高知识。所研究的压具将具有大变形能力，且易于更换部件。此外，压紧件将具有在大变形下以受控和可重复的方式降低部件强度的潜力，同时在低变形下保持原始强度。该部件特性可以降低整个系统的超强度，这反过来将具有有益的经济意义。减少新建筑的碳足迹，连接农村和城市经济，增加地震区建筑物的寿命，这些都是大规模木材研究将推进的目标，对城市的可持续发展至关重要。

The urgency in increasing growth in densely populated urban areas, reducing the carbon footprint of new buildings, and targeting rapid return to occupancy following disastrous earthquakes has created a need to reexamine the structural systems of mid- to high-rise buildings. To address these sustainability and seismic resiliency needs, the objective of this research is to enable an all-timber material system in a way that will include architectural as well as structural considerations. Utilization of mass timber is societally important in providing buildings that store, instead of generate, carbon and increase the economic opportunity for depressed timber-producing regions of the country. This research will focus on buildings with core walls because those building types are some of the most common for contemporary urban mid- to high-rise construction. The open floor layout will allow for commercial and mixed-use occupancies, but also will contain significant technical knowledge gaps hindering their implementation with mass timber. The research plan has been formulated to fill these gaps by: (1) developing suitable mid- to high-rise archetypes with input from multiple stakeholders, (2) conducting parametric system-level seismic performance investigations, (3) developing new critical components, (4) validating the performance with large-scale experimentation, and (5) bridging the industry information gaps by incorporating teaching modules within an existing educational and outreach framework. Situated in the heart of a timber-producing region, the multi-disciplinary team will utilize the local design professional community with timber experience and Portland State University's recently implemented Green Building Scholars program to deliver technical outcomes that directly impact the surrounding environment.Research outcomes will advance knowledge at the system performance level as well as at the critical component level. The investigated building system will incorporate cross laminated timber cores, floors, and glulam structural members. Using mass timber will present challenges in effectively achieving the goal of desirable seismic performance, especially seismic resiliency. These challenges will be addressed at the system level by a unique combination of core rocking combined with beam and floor interaction to achieve non-linear elastic behavior. This system behavior will eliminate the need for post-tensioning to achieve re-centering, but will introduce new parameters that can directly influence the lateral behavior. This research will study the effects of these parameters on the overall building behavior and will develop a methodology in which designers could use these parameters to strategically control the building seismic response. These key parameters will be investigated using parametric numerical analyses as well as large-scale, sub-system experimentation. One of the critical components of the system will be the hold-down, a device that connects the timber core to the foundation and provides hysteretic energy dissipation. Strength requirements and deformation demands in mid- to high-rise buildings, along with integration with mass timber, will necessitate the advancement of knowledge in developing this low-damage component. The investigated hold-down will have large deformation capability with readily replaceable parts. Moreover, the hold-down will have the potential to reduce strength of the component in a controlled and repeatable way at large deformations, while maintaining original strength at low deformations. This component characteristic can reduce the overall system overstrength, which in turn will have beneficial economic implications. Reducing the carbon footprint of new construction, linking rural and urban economies, and increasing the longevity of buildings in seismic zones are all goals that this mass timber research will advance and will be critical to the sustainable development of cities moving forward.