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Structures Research Group

 
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The Engineering Department (CUED) hosts a series of Structures seminars for post-graduates, undergraduates and staff. Non-CUED university people are also welcome to attend. The seminars will be at the Seminar room, Civil Engineering building in West Cambridge at 3pm, unless otherwise stated.
Updated: 21 min 57 sec ago

Fri 09 Dec 15:00: Instabilities in kirigami structures

Mon, 05/12/2022 - 09:35
Instabilities in kirigami structures

Kirigami, an ancient Japanese art of paper cutting, inspires new ways to tailor the morphology and the mechanics of thin elastic sheets. It has been found to be of special relevance to applications in reconfigurable structures (e.g., large deployable structures) and microstructures (e.g., stretchable graphene sheets). Indeed, careful tailoring of cut patterns results in structures with interesting non-linear macroscopic responses emerging from local instabilities. In this presentation, we will discuss local effects in Kirigami by focusing our attention on the study of the deformation of a thin sheet with a single cut—i.e., the most basic and fundamental geometric building block of Kirigami. We will also discuss a new phenomenon that arises when kirigami sheets interact with a liquid substrate, namely elastocapillary kirigami. We study the effects of a liquid foundation and how it changes the nature of the local instabilities. Our analysis reveals that post-buckling configurations displays two types of a phase transitions: continuous (second order phase transition), which suggests a uniform phase; and a discontinuous transition (first order), leading to a phase propagation through kirigami structures.

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Fri 09 Dec 15:00: Title to be confirmed

Sun, 27/11/2022 - 19:49
Title to be confirmed

Abstract not available

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Fri 25 Nov 15:00: A Swiss Structures seminar from FlexLab

Tue, 22/11/2022 - 09:25
A Swiss Structures seminar from FlexLab

Luna, Fani and Michael are postdocs from the Flexible Structures Laboratory, EPFL Lausanne. Each will present a talk, covering the following topics:

(i) – Luna – The fluid-structure interaction of bristled wings

Slender structures covered with hairs are commonly observed in nature. A particularly intriguing example is the bristled wings of miniature insects. With bristled wings, miniature insects achieve flight via drag-based rowing mechanisms. By combining experiments, simulations and theoretical analysis, we aim to investigate the trade-off among weight, stiffness, and drag of idealized models of the bristled wings. Particular emphasis is given to the role of elastic deformation of the bristles in modifying the generated drag.

(ii) – Fani – Shell buckling of imperfect shells as an extreme-value statistics problem

The buckling capacity of thin shells is highly sensitive to imperfections. Here, we investigate the even more challenging problem of shells containing a random distribution of defects. Focusing on elastic hemispherical shells, we study the statistics of critical buckling loads using experimentally validated finite element modeling (FEM). Our results suggest that the shell buckling of shells containing a random distribution of defects can be regarded as a ‘weakest-link’ problem governed by extreme-value statistics.

(iii) – Michael – Elastic ribbons with inhomogeneous pre-stress: twisting instabilities and reduced models

For a slender elastic filament subject to small pre-stress, it is well known that the system can be modelled as an Euler–Bernoulli rod with effective natural curvature and twist. However, a challenge is to formulate effective models in situations where the Euler–Bernoulli kinematic assumptions do not apply. To address the need for simple, reduced models of such filaments, in this talk we analyse elastic ribbons subject to large, inhomogeneous pre-stress as a model system. We find that the buckling behaviour provides a macroscopic analogue of several critical phenomena in the classical theory of thermodynamic phases.

The meeting can be viewed in CivEng or joined online:

https://eng-cam.zoom.us/j/82357897828?pwd=SnhDdFJjQS9xNlFFQWtTTW5LNzlGdz09

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Wed 30 Nov 16:00: Active Rheology and Stiffening Control of cementitious materials

Fri, 18/11/2022 - 09:20
Active Rheology and Stiffening Control of cementitious materials

Rheological properties of fresh cementitious materials to a large extent depend on mix design and processing conditions, currently leaving only limited options to actively modify workability or flowability during casting. Cutting-edge research at Ghent University has led to a scientific break-through, enabling active intervention during processing, based on the application of external signals to trigger an intended response in the material. This presentation will explain the first concepts of Active Rheology Control (ARC) and Active Stiffening control (ASC) of cementitious materials. Two different routes have been studied, based on responsive mineral particles, and based on newly developed switchable superplasticizers. First proofs of concept at fundamental paste level will be explained. Remaining challenges will be identified. Finding solutions to these challenges will lead to marvelous opportunities for concrete pumping and formwork casting in general, and for 3D printing of concrete structures more particularly.

The meeting can be viewed in CivEng or joined online:

https://eng-cam.zoom.us/j/82357897828?pwd=SnhDdFJjQS9xNlFFQWtTTW5LNzlGdz09

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Fri 25 Nov 15:00: A Swiss Structures seminar from FlexLab

Fri, 18/11/2022 - 09:20
A Swiss Structures seminar from FlexLab

Three postdocs from the Flexible Structures Laboratory, EPFL Lausanne, will be talking to us about their research, covering the following topics

(i) Fluid-structure interaction of porous structures at small scales (ii) Complex rods with internal structures (iii) Probabilistic shell buckling

The meeting can be viewed in CivEng or joined online:

https://eng-cam.zoom.us/j/82357897828?pwd=SnhDdFJjQS9xNlFFQWtTTW5LNzlGdz09

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Fri 18 Nov 15:00: Concrete Canvas – from university project to global company

Fri, 18/11/2022 - 09:20
Concrete Canvas – from university project to global company

Concrete Canvas is the originator of a new class of cementitious composites called GCC Ms. Concrete Canvas has offices on every continent and its GCC Ms are supplied globally. They enable construction 10 times faster than conventional sprayed or poured concrete with less material to transport and less embodied carbon. Peter Brewin, a founder and alumni, will describe the journey from university project to a UK manufacturer with global sales and will explain how GCC Ms work, how they are being used and the global challenges they can help solve.

The meeting can be viewed in CivEng or joined online:

https://eng-cam.zoom.us/j/82357897828?pwd=SnhDdFJjQS9xNlFFQWtTTW5LNzlGdz09

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Wed 30 Nov 16:00: Active Rheology and Stiffening Control of cementitious materials

Thu, 10/11/2022 - 09:14
Active Rheology and Stiffening Control of cementitious materials

Rheological properties of fresh cementitious materials to a large extent depend on mix design and processing conditions, currently leaving only limited options to actively modify workability or flowability during casting. Cutting-edge research at Ghent University has led to a scientific break-through, enabling active intervention during processing, based on the application of external signals to trigger an intended response in the material. This presentation will explain the first concepts of Active Rheology Control (ARC) and Active Stiffening control (ASC) of cementitious materials. Two different routes have been studied, based on responsive mineral particles, and based on newly developed switchable superplasticizers. First proofs of concept at fundamental paste level will be explained. Remaining challenges will be identified. Finding solutions to these challenges will lead to marvelous opportunities for concrete pumping and formwork casting in general, and for 3D printing of concrete structures more particularly.

The meeting can be viewed in CivEng or joined online:

https://eng-cam.zoom.us/j/82357897828?pwd=SnhDdFJjQS9xNlFFQWtTTW5LNzlGdz09

Add to your calendar or Include in your list

Fri 25 Nov 15:00: A Swiss Structures seminar from FlexLab

Thu, 10/11/2022 - 09:14
A Swiss Structures seminar from FlexLab

Three postdocs from the Flexible Structures Laboratory, EPFL Lausanne, will be talking to us about their research, covering the following topics

(i) Fluid-structure interaction of porous structures at small scales (ii) Complex rods with internal structures (iii) Probabilistic shell buckling

The meeting can be viewed in CivEng or joined online:

https://eng-cam.zoom.us/j/82357897828?pwd=SnhDdFJjQS9xNlFFQWtTTW5LNzlGdz09

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Fri 11 Nov 15:00: Snap through Dynamics and some strategies for morphing

Thu, 10/11/2022 - 09:14
Snap through Dynamics and some strategies for morphing

The snap through of a spherical cap happen quickly, but still slowly relative to an elastic time scale. This talk will discuss how such slow dynamics can arise without viscous dissipation, and how the snap through of multiple soft elements provides a means of morphing that is reprogrammable.

The meeting can be viewed in CivEng or joined online:

https://eng-cam.zoom.us/j/82357897828?pwd=SnhDdFJjQS9xNlFFQWtTTW5LNzlGdz09

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Fri 18 Nov 15:00: Concrete canvas

Thu, 10/11/2022 - 09:13
Concrete canvas

Peter is the co-founder, and director of Concrete Canvas, a company which specialises in composite concrete-fabric technologies, including geosynthetic concrete composite mats and rapidly inflatable concrete-fabric shelters. He will be speaking about entrepreneurship and developing the technologies.

The meeting can be viewed in CivEng or joined online:

https://eng-cam.zoom.us/j/82357897828?pwd=SnhDdFJjQS9xNlFFQWtTTW5LNzlGdz09

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Fri 11 Nov 15:00: Snap through Dynamics and some strategies for morphing

Mon, 07/11/2022 - 09:17
Snap through Dynamics and some strategies for morphing

The snap through of a spherical cap happen quickly, but still slowly relative to an elastic time scale. This talk will discuss how such slow dynamics can arise without viscous dissipation, and how the snap through of multiple soft elements provides a means of morphing that is reprogrammable.

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Fri 04 Nov 15:00: Theory and the Creation of Structures; Using the concepts of Airy, Maxwell, Michell, Heyman, Calladine, Pellegrino, Guest and McRobie to create structures

Tue, 01/11/2022 - 14:53
Theory and the Creation of Structures; Using the concepts of Airy, Maxwell, Michell, Heyman, Calladine, Pellegrino, Guest and McRobie to create structures

Fundamental concepts such as energy theorems, the geometry of equilibrium, mechanisms & states of self-stress and engineering mechanics are an excellent basis for creating efficient and elegant structural systems. The talk will provide an overview of how some of the concepts of Airy, Maxwell, Michell, Calladine, Pellegrino, Guest and McRobie (along with help from Rankine) provide insights into the creation of structures

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Fri 04 Nov 15:00: Theory and the Creation of Structures; Using the concepts of Airy, Maxwell, Michell, Calladine, Pellegrino, Guest and McRobie to create structures

Sun, 30/10/2022 - 14:28
Theory and the Creation of Structures; Using the concepts of Airy, Maxwell, Michell, Calladine, Pellegrino, Guest and McRobie to create structures

Fundamental concepts such as energy theorems, the geometry of equilibrium, mechanisms & states of self-stress and engineering mechanics are an excellent basis for creating efficient and elegant structural systems. The talk will provide an overview of how some of the concepts of Airy, Maxwell, Michell, Calladine, Pellegrino, Guest and McRobie (along with help from Rankine) provide insights into the creation of structures

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Fri 11 Nov 15:00: Title to be confirmed

Fri, 28/10/2022 - 09:19
Title to be confirmed

TBC

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Fri 04 Nov 15:00: Theory and the Creation of Structures

Fri, 28/10/2022 - 09:17
Theory and the Creation of Structures

Abstract to be confirmed

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Wed 30 Nov 16:00: Active Rheology and Stiffening Control of cementitious materials

Thu, 20/10/2022 - 14:38
Active Rheology and Stiffening Control of cementitious materials

Rheological properties of fresh cementitious materials to a large extent depend on mix design and processing conditions, currently leaving only limited options to actively modify workability or flowability during casting. Cutting-edge research at Ghent University has led to a scientific break-through, enabling active intervention during processing, based on the application of external signals to trigger an intended response in the material. This presentation will explain the first concepts of Active Rheology Control (ARC) and Active Stiffening control (ASC) of cementitious materials. Two different routes have been studied, based on responsive mineral particles, and based on newly developed switchable superplasticizers. First proofs of concept at fundamental paste level will be explained. Remaining challenges will be identified. Finding solutions to these challenges will lead to marvelous opportunities for concrete pumping and formwork casting in general, and for 3D printing of concrete structures more particularly.

Add to your calendar or Include in your list

Fri 25 Nov 15:00: A Swiss Structures seminar from FlexLab

Thu, 20/10/2022 - 09:05
A Swiss Structures seminar from FlexLab

Three postdocs from the Flexible Structures Laboratory, EPFL Lausanne, will be talking to us about their research, covering the following topics

(i) Fluid-structure interaction of porous structures at small scales (ii) Complex rods with internal structures (iii) Probabilistic shell buckling

Add to your calendar or Include in your list

Fri 18 Nov 15:00: Concrete canvas

Thu, 20/10/2022 - 08:53
Concrete canvas

Peter is the co-founder, and director of Concrete Canvas, a company which specialises in composite concrete-fabric technologies, including geosynthetic concrete composite mats and rapidly inflatable concrete-fabric shelters. He will be speaking about entrepreneurship and developing the technologies.

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Fri 28 Oct 15:00: Understanding Tensegrity with an Energy Function

Thu, 20/10/2022 - 08:45
Understanding Tensegrity with an Energy Function

The methods of analysis of pin-jointed structures that we teach our first-year undergraduate students cannot explain why tensegrities stand up: this talk will explore a helpful complementary analysis. The talk will explore the use of a simple quadratic ‘energy function’ to model pin-jointed structures that are stressed; the function is clearly unphysical, but it is simple, and wrong in a useful way. Using the quadratic function makes is straightforward to correctly capture the stiffness of the inextensional modes of deformation in tensegrity structures that a simple analysis ignores.

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Fri 21 Oct 15:00: Graphic Statics as a Legendre Transform

Tue, 18/10/2022 - 20:55
Graphic Statics as a Legendre Transform

This somewhat impromptu talk is to describe a few things that I have been thinking about in my research of late. It will be more of a discussion piece than a polished fait accompli.

After a brief overview of some recent work in 2D and 3D graphic statics, this talk will focus in on a few fundamentals. These can be found in James Clerk Maxwell’s 1870 paper “On Reciprocal Figures, Frames and Diagrams of Forces” and they relate to the notion of a stress function. Encouraged by Bill Baker to read Maxwell’s original papers, I was quite taken aback at how little I was aware of the basics of my own subject. This short talk will look at Maxwell’s notion of a “Diagram of Stress”, involving a stress space wherein the only stress is a simple, constant, isotropic pressure from which (almost) any other stress field can be constructed. This leads naturally to the conclusion that “form” and “force”, the two fundamentals of graphic statics, are a Legendre transform pair. I will show how this understanding can be extended to include moments, and finish with a brief glimpse at how this may find applications in the design of materially-efficient structures, including shells and gridshells.

Recommended pre-reading: JC Maxwell 1870, “On Reciprocal Figures, Frames and Diagrams of Forces”, Trans RS Edinburgh, XXVI , Pt1, pp 1-40, section: “General Theory of Diagram of Stress in Three Dimensions”. https://archive.org/details/dli.granth.111835/page/178/mode/2up

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