Collaborative Research: Seismic Isolation of Embedded Foundations Using Periodic Meta-material Barriers to Create Resilient Structures

过去几十年来地震造成的严重破坏凸显了改善的必要性，以减少对美国经济和公民安全的相关威胁。最近地震中的证据表明，传统的隔震系统在减少地震水平分量造成的破坏方面是有效的。然而，传统的隔震系统不能很好地抵御地震震动的垂直分量，也不能很容易地用于嵌入式或地下结构。为了克服传统隔震体系的不足，我们开发了基于周期性材料的新型隔震器。周期性的基于材料的隔震器具有明显的频带间隙，可以阻挡、过滤和反射频率落在这些间隙之间的入射地面振动。这些频带间隙可以被设计成阻止对结构有害的地面运动。以前的研究表明，由周期性材料隔震器组成的周期性基础在隔震地面上建造的结构的地面运动方面是有效的。本项目将研究嵌入式或地下结构的周期性基于材料的隔震系统。从这项研究中获得的知识将具有广泛而深远的意义，超越了传统的商业和住宅建筑，并延伸到位于地震区的所有类型的结构。这项研究的结果可以在普遍的基础上影响抗震设计规范的发展。该项目涉及基于周期性超材料屏障的隔震系统的研究，用于弹性结构的开发。周期超材料屏障隔震体系是与周期基础配套使用的隔震体系。周期势垒和周期基础都受到声子晶体的启发，声子晶体可以利用频率带隙机制隔离地震波。利用这一机制，无论波的传播方向如何，落在适当设计的周期性基础或障碍物的频带内的入射地震波都将被过滤掉。周期性基础也是上部结构的基础，它可以隔离来自嵌入基础下的土壤中的地震波。另一方面，周期性屏障将嵌入的结构与输入的横向地震波隔离。周期屏障和周期基础的组合将形成嵌入基础的隔震包络。本项目将通过数值模拟和现场研究相结合的方法来研究组合周期性屏障和周期性基础体系的有效性。实地研究将研究地震波如何在有和没有周期性屏障的土壤中传播。该项目的主要目标是开发能够有效衰减传入地震波的周期性屏障。该项目还将生成一套简化的设计指南，用于实践工程师设计可减弱地震震动的周期性屏障。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。

The severity of damage caused by earthquakes over the past decades underscores the need for improvements to reduce the associated threat to America's economy and the safety of its citizens. Evidence in more recent earthquakes shows that conventional seismic isolation systems are effective in reducing the damage from horizontal components of earthquake shaking. However, conventional isolation systems are not well suited for protection against the vertical components of earthquake shaking, nor can they be readily used for embedded or underground structures. To overcome the disadvantages in the conventional seismic isolation systems, we have developed innovative periodic material-based seismic isolators. Periodic material-based seismic isolators possess distinct frequency band gaps which block, filter, and reflect incoming ground vibrations with frequencies falling between these gaps. These frequency band gaps can be designed to block ground motions that are harmful to structures. Previous studies have shown periodic foundations, made of periodic material-based seismic isolators, to be effective in isolating ground motions for structures built on the ground surface. This project will investigate periodic material-based seismic isolation systems of embedded or underground structures. The knowledge gained from this research will have broad and far-reaching significance that goes beyond conventional commercial and residential buildings and extends to all types of structures located in seismic zones. Results from this research can impact the development of seismic design codes on a universal basis.This project involves the investigation of periodic meta-material barriers-based seismic isolation systems for development of resilient structures. The periodic meta-material barriers-based seismic isolation system is a complementary system to be applied together with periodic foundations. Both periodic barriers and periodic foundations are inspired by phononic crystal, which can isolate the seismic waves using the frequency band gap mechanism. With this mechanism, the incoming seismic waves falling within the frequency band gaps of the properly designed periodic foundations or barriers will be filtered out regardless of the direction of wave propagation. The periodic foundations, which also act as the foundation of the superstructure, can isolate seismic waves coming from the soil beneath the embedded foundations. Periodic barriers, on the other hand, will isolate the embedded structures from the incoming lateral seismic waves. The combination of periodic barriers and periodic foundation will form an isolation envelope for the embedded foundations. This project will study the effectiveness of the combined periodic barriers and the periodic foundation systems through numerical simulation and field studies. The field studies will examine how seismic waves propagate in soil with and without periodic barriers. The main objective of this project is to develop periodic barriers that can effectively attenuate incoming seismic waves. This project will also generate a set of simplified design guidelines for practicing engineers to design periodic barriers that will attenuate seismic shaking.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.