COOKIES: By using this website you agree that we can place Google Analytics Cookies on your device for performance monitoring. |

University of Cambridge > Talks.cam > Engineering Department - Mechanics Colloquia Research Seminars > Counting with symmetry for structural analysis

## Counting with symmetry for structural analysisAdd to your list(s) Download to your calendar using vCal - Dr Simon Guest, CUED
- Friday 20 November 2015, 14:00-15:00
- Department of Engineering - LR2.
If you have a question about this talk, please contact Ms Helen Gardner. Counting components, and then comparing the number of constraints with number of degrees of freedom available to a structure, is a good first step in evaluating likely structural behaviour. Maxwell first described this in 1864 when he stated that, in general, a structure with j joints would require 3j-6 bars to make it rigid. Later Calladine generalised this idea by pointing out that the difference between the number of bars and 3j-6 counts the difference between the number of mechanisms and the number of states of self-stress. Sometimes, just simple counting can lead to profound insights, such as showing that any stiff repetitive structure must necessarily be overconstrained. This talk will introduce the idea that any rule that involves counting components can be expanded to a more general symmetry version that involves counting the symmetries of sets of components, and that this counting can practically be done by simply considering the number of components that are unshifted by particular symmetry operations. This provides useful insight into why certain symmetric structures are able to move despite apparently having enough members to make them rigid, or that tensengrity structures can be rigid without having ‘enough’ members. The talk will describe a recent result on ‘auxetic’ materials: a symmetry criterion that shows when a periodic system made up of bars, bodies and joints has an ‘equiauxetic’ mechanism, that is, show the limiting behaviour of Poisson ratio equal to -1, with equal expansion/contraction in all directions. Such systems can provide good models for the design of lattice materials with high, stretching-dominated, shear modulus, but low, bending-dominated, bulk modulus. This talk is part of the Engineering Department - Mechanics Colloquia Research Seminars series. ## This talk is included in these lists:- All Talks (aka the CURE list)
- Cambridge University Engineering Department Talks
- Cambridge talks
- Centre for Smart Infrastructure & Construction
- Civil Engineering Talks
- Department of Engineering - LR2
- Engineering - Division C talks
- Engineering Department - Mechanics Colloquia Research Seminars
- Engineering Department Bio- and Micromechanics Seminars
- Engineering Department Dynamics and Vibration Tea Time Talks
- Featured lists
- Interested Talks
- Lennard-Jones Centre external
- School of Technology
- Trust & Technology Initiative - interesting events
- bld31
Note that ex-directory lists are not shown. |
## Other listsThe Impact of Social Science Research Single Cell seminars at the Wellcome Genome Campus The obesity epidemic: Discussing the global health crisis Software Innovation Centre for Global Equality CU Labour Club: All Events## Other talksConstructing the organism in the age of abstraction Domain Uncertainty Quantification On being a "barang": Experiences of interviewing fishermen in Cambodia and Indonesia Equations in groups Exploring the mechanisms of haematopoietic lineage progression at the single-cell level Beyond crazy: Rationality, irrationality, and conspiracy theory |