Dynamic modeling and response modification effects of negative stiffness elements: metamaterials, origami and brace
| dc.contributor.advisor | Nagarajaiah, Satish | en_US |
| dc.creator | Herkal, Sudheendra | en_US |
| dc.date.accessioned | 2023-08-09T19:44:54Z | en_US |
| dc.date.created | 2023-05 | en_US |
| dc.date.issued | 2023-04-21 | en_US |
| dc.date.submitted | May 2023 | en_US |
| dc.date.updated | 2023-08-09T19:44:54Z | en_US |
| dc.description | EMBARGO NOTE: This item is embargoed until 2025-05-01 | en_US |
| dc.description.abstract | Negative stiffness is an unconventional property wherein the system assists the deformation instead of resisting it. The negative stiffness property has been observed at multiple scales ranging from nano to meso to macro scales. The negative stiffness property is a very interesting property that has been evaluated for seismic isolation, added in parallel to positive stiffness to achieve high static low dynamic stiffness setting leading to good vibration isolation performance, enhancing material as well as system damping, also evaluated for tuned mass damper performance enhancement, etc. In this study, the systems at three scales that produce negative stiffness are investigated, namely mesoscale metamaterials resembling nano-scale Schwarzite, meso-scale origami materials and macro-scale negative stiffness brace. In the first part of the study, a metamaterial called "Schwarzite" was studied. Owing to its unique architecture, the metamaterial is considered to possess many interesting properties including negative stiffness. However, during the experimentation, it was found that negative stiffness occurs at high strain and was difficult to acheive and control due to test setup limitations. But the experimentation also revealed good energy dissipation properties of the metamaterial. Thus, the metamaterial was studied for vibration isolation applications. The meso-scale metamaterial was manufactured using 3D printing, scaling up the nano-scale Schwarzite architecture, along with a specimen with solid geometry, which was used as a control specimen. Both the geometries were cyclically tested and mathematical models were then developed to capture their experimental hysteretic behaviour. Numerical simulations were then performed on two systems with the same mass supported by the two different geometries and it was found that higher energy dissipation of Schwarzite results in enhanced damping leading to response reduction. The investigation also showed that Schwarzite architecture utilized its tensile and compressive capacities fully, much more efficiently than the solid geometry. The second part of this study investigated meso-scale origami structures. Many origami structures demonstrate the property of negative stiffness which further leads to other interesting properties such as deployability and actuation. However, the dynamic behaviour of these structures is not well understood due to the lack of viable and validated dynamic modelling approaches. An experimentally validated dynamic modelling would help us understand their deployment process and dynamic behaviour better and lead to their increased applicability. Thus, a dynamic modelling approach was proposed in this study. For modelling the stiffness, the reduced-order origami modelling approach was considered while the mass was modelled using mass lumping approach. The best mass lumping formulation was then determined by comparing the results of various mass lumping formulations to finite element simulations and it was found that triangle circumcenter mass formulation was able to capture the dynamics satisfactorily for various loading and geometric scenarios. Then, quasi-static and dynamic experiments were performed to validate the developed dynamic model, experimentally. The final part of the study presents the study of a proposed Negative Stiffness Brace (NSB). Negative stiffness brace similar to a conventional steel brace that is compact and easy to install was studied. The analytical framework to describe the behaviour of NSB was derived. Further, a parametric study was performed to understand the influence of various parameters towards the force-displacement behaviour of NSB. Various parameters that can magnify the stiffness of NSB were determined, which can be exploited for reducing the stiffness of pre-compressed springs when used for structural applications. The developed analytical model was validated by fabricating the device at macro-scale and determining its experimental behaviour. The analytical framework for describing the response of a frame consisting of NSB was then derived. The model of the frame with and without NSB was fabricated and then experimentally verified using a prototype of the frame and the prototype of NSB. Finally, using numerical simulations, the effectiveness of NSB in protecting the structure from periodic as well as seismic base excitation was determined. It was found that NSB significantly reduces the base shear, displacements and accelerations of the structure. In this investigation each length scale was explored individually, to gain better understanding. However, integration between different length scales is still needed. Future investigations that involve efforts to integrate negative stiffness property from material to structure levels are needed, as such a comprehensive effort is beyond the scope of this study. | en_US |
| dc.embargo.lift | 2025-05-01 | en_US |
| dc.embargo.terms | 2025-05-01 | en_US |
| dc.format.mimetype | application/pdf | en_US |
| dc.identifier.citation | Herkal, Sudheendra. "Dynamic modeling and response modification effects of negative stiffness elements: metamaterials, origami and brace." (2023) Diss., Rice University. <a href="https://hdl.handle.net/1911/115209">https://hdl.handle.net/1911/115209</a>. | en_US |
| dc.identifier.uri | https://hdl.handle.net/1911/115209 | en_US |
| dc.language.iso | eng | en_US |
| dc.rights | Copyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder. | en_US |
| dc.subject | Negative stiffness | en_US |
| dc.subject | origami structures | en_US |
| dc.subject | metamaterials | en_US |
| dc.title | Dynamic modeling and response modification effects of negative stiffness elements: metamaterials, origami and brace | en_US |
| dc.type | Thesis | en_US |
| dc.type.material | Text | en_US |
| thesis.degree.department | Civil and Environmental Engineering | en_US |
| thesis.degree.discipline | Engineering | en_US |
| thesis.degree.grantor | Rice University | en_US |
| thesis.degree.level | Doctoral | en_US |
| thesis.degree.name | Doctor of Philosophy | en_US |
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