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- Adiels, Emil, 1989, et al.
(författare)
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The use of virtual work for the formfinding of fabric, shell and gridshell structures
- 2018
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Ingår i: Proceedings of the Advances in Architectural Geometry conference 2018. - 9783903015135 ; , s. 286-315
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Konferensbidrag (refereegranskat)abstract
- The use of the virtual work theorem enables one to derive the equations of static equilibrium of fabric, shell and gridshell structures from the compatibility equations linking the rate of deformation of a surface to variations in its velocity. If the structure is treated as a continuum there is no need to consider its micro-structure provided that the grid is fine compared to the overall geometry. Thus we can include fabrics, ribbed shells, corrugated shells and gridshells with a fine grid, such as the Mannheim Multihalle. The equilibrium equations are almost identical to those obtained by assuming that a shell is thin and of uniform thickness, but are more general in their application. Our formulation introduces the concept of geodesic bending moments which are relevant to gridshell structures with continuous laths. The virtual work theorem is more general than the energy theorems, which it in- cludes as a special case. Hence it can be applied to surfaces which admit some form of potential, including minimal surfaces and hanging fabrics. We can then use the calculus of variations for the minimization of a surface integral to define the form of a structure. Many existing formfinding techniques can be rewritten in this way, but we concen- trate on surfaces which minimize the surface integral of the mean curvature subject to a constraint on the enclosed volume, producing a surface of constant Gaussian curvature. This naturally leads to the more general study of conjugate stress and curvature directions, and hence to quadrilateral mesh gridshells with flat cladding panels and no bending moments in the structural members under own weight.
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| 2. |
- Olsson, Sara, et al.
(författare)
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Covalently attached UV-absorbers for improved UV-protection of wood
- 2010
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Ingår i: Proceedings of The Fifth European Conference on Wood Modification ECWM5. - : Latvian State Institute of Wood Chemistry.
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Konferensbidrag (refereegranskat)abstract
- The present study describes the use of reactive UV-absorbers (UVAs) that can be covalently attached to a wood substrate to obtain an improved exterior durability. It has previously been demonstrated that the photostability of wood is increased if the UVA is grafted to the wood surface. The grafting of an epoxide-functional UVA, 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP), to thin veneer wood specimens had a larger photostabilizing effect than if the corresponding UVA without the reactive handle was added to the wood coating. The present study shows that not only the chemical structure of the UVA is important but also how the modification is performed i.e. the reaction procedure. A successful attachment of the UVA depends on both the reaction conditions as well as if other reactive species are present at the same time. The presence of for example a vegetable oil (epoxy functionalized soy bean oil) affects the grafting reaction of the UVA. Details on the effect of reaction conditions, reaction sequences, and presence of co-reactants will be presented.
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| 7. |
- Ander, Mats, 1964, et al.
(författare)
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A building of unlimited height
- 2019
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Ingår i: IASS Symposium 2019 - 60th Anniversary Symposium of the International Association for Shell and Spatial Structures; Structural Membranes 2019 - 9th International Conference on Textile Composites and Inflatable Structures, FORM and FORCE. - 9788412110104 ; , s. 1465-1472
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Konferensbidrag (refereegranskat)abstract
- We consider the overall buckling under own weight of a thin-walled column of circular cross-section and a radius that is a hyperbolic sine function of distance from the top of the column. The maximum stress is limited to a given value, but there is no limit to the height of the column. The wall thickness is determined by consideration of local buckling. It can be made to represent a building by adjusting the own weight of the column to include the weight of the floors, finishes, cladding and imposed load.
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| 9. |
- Andersson, Tim, et al.
(författare)
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Comparison of Machine Learning’s- and Humans’- Ability to Consistently Classify Anomalies in Cylinder Locks
- 2022
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Ingår i: IFIP Advances in Information and Communication Technology. - Cham : Springer Science and Business Media Deutschland GmbH. - 9783031164064 ; , s. 27-34, s. 27-34
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Konferensbidrag (refereegranskat)abstract
- Historically, cylinder locks’ quality has been tested manually by human operators after full assembly. The frequency and the characteristics of the testing procedure for these locks wear the operators’ wrists and lead to varying results of the quality control. The consistency in the quality control is an important factor for the expected lifetime of the locks which is why the industry seeks an automated solution. This study evaluates how consistently the operators can classify a collection of locks, using their tactile sense, compared to a more objective approach, using torque measurements and Machine Learning (ML). These locks were deliberately chosen because they are prone to get inconsistent classifications, which means that there is no ground truth of how to classify them. The ML algorithms were therefore evaluated with two different labeling approaches, one based on the results from the operators, using their tactile sense to classify into ‘working’ or ‘faulty’ locks, and a second approach by letting an unsupervised learner create two clusters of the data which were then labeled by an expert using visual inspection of the torque diagrams. The results show that an ML-solution, trained with the second approach, can classify mechanical anomalies, based on torque data, more consistently compared to operators, using their tactile sense. These findings are a crucial milestone for the further development of a fully automated test procedure that has the potential to increase the reliability of the quality control and remove an injury-prone task from the operators.
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| 10. |
- Andersson, Tim, et al.
(författare)
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Interpretable ML model for quality control of locks using counterfactual explanations
- 2024
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Konferensbidrag (refereegranskat)abstract
- This paper presents an interpretable machinelearning model for anomaly detection in door locks using torque data. The model aims to replace the human tactile sense in the quality control process, reducing repetitive tasks and improving reliability. The model achieved an accuracy of 96%, however, to gain social acceptance and operators' trust, interpretability of the model is crucial. The purpose of this study was to evaluate anapproach that can improve interpretability of anomalousclassifications obtained from an anomaly detection model. Weevaluate four instance-based counterfactual explanators, three of which, employ optimization techniques and one uses, a less complex, weighted nearest neighbor approach, which serve as ourbaseline. The former approaches, leverage a latent representation of the data, using a weighted principal component analysis, improving plausibility of the counter factual explanations andreduces computational cost. The explanations are presentedtogether with the 5-50-95th percentile range of the training data, acting as a frame of reference to improve interpretability. All approaches successfully presented valid and plausible counterfactual explanations. However, instance-based approachesemploying optimization techniques yielded explanations withgreater similarity to the observations and was therefore concluded to be preferable despite the higher execution times (4-16s) compared to the baseline approach (0.1s). The findings of this study hold significant value for the lock industry and can potentially be extended to other industrial settings using timeseries data, serving as a valuable point of departure for further research.
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