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出需要改进，以减少对美国经济和公民安全的相关威胁。最近地震的证据表明，传统的隔震系统在减少地震震动水平分量的破坏方面是有效的。然而，传统的隔震系统不能很好地防止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。为了克服传统隔震系统的缺点，我们开发了创新的周期性材料隔震器。基于周期性材料的隔震器具有独特的频带间隙，可以阻挡、过滤和反射入射的地面振动，频率落在这些间隙之间。这些频带间隙可以用来阻挡对结构有害的地面运动。以前的研究表明，周期性基础是由周期性材料制成的隔震器，可以有效地隔离地面上建造的结构的地面运动。该项目将研究嵌入式或地下结构的周期性材料隔震系统。从本研究中获得的知识将具有广泛而深远的意义，超越传统的商业和住宅建筑，扩展到位于地震带的所有类型的结构。这一研究结果将对通用抗震设计规范的发展产生影响。该项目涉及研究基于周期性超材料屏障的隔震系统，用于开发弹性结构。周期性超材料屏障隔震体系是与周期性基础相辅相成的隔震体系。周期势垒和周期基都是由声子晶体启发的，它们可以利用带隙机制隔离地震波。利用这种机制，无论波的传播方向如何，在合理设计的周期性基础或屏障的频带间隙内的入射地震波都将被过滤掉。周期性基础也充当上层建筑的基础，可以隔离来自嵌入式基础下土壤的地震波。另一方面，周期屏障将把嵌入结构与传入的横向地震波隔离开来。周期屏障与周期基础的结合将为嵌入式基础形成一个隔离包络。本项目将通过数值模拟和现场研究，研究周期屏障和周期基础组合体系的有效性。实地研究将检查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入射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，供执业工程师设计周期性屏障，以减弱地震震动。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.