| 1. |
- Adiels, Emil, 1989, et al.
(författare)
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Brick patterns on shells using geodesic coordinates
- 2017
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Ingår i: Proceedings of the IASS Annual Symposium 2017. IASS Annual Symposium 2017; Hamburg, Germany; 25 - 28 September 2017.
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Konferensbidrag (refereegranskat)abstract
- We present two separate strategies for generating brick patterns on free form shells and vaults using geodesic coordinates. The brickwork is specified by a surface on which there is a geodesic coordinate system satisfying the condition for a constant distance between bed joints. The first strategy integrates the generation of the geodesic coordinates in a form finding procedure derived from the geometrical and mechanical properties of a shell. The geometric and structural equations are solved using dynamicrelaxation. The second strategy can be applied on an arbitrary surface separating the form
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| 2. |
- Adiels, Emil, 1989, et al.
(författare)
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The architectural application of shells whose boundaries subtend a constant solid angle
- 2024
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Ingår i: Computer Aided Geometric Design. - 0167-8396. ; 111
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Tidskriftsartikel (refereegranskat)abstract
- Surface geometry plays a central role in the design of bridges, vaults and shells, using various techniques for generating a geometry which aims to balance structural, spatial, aesthetic and construction requirements. In this paper we propose the use of surfaces defined such that given closed curves subtend a constant solid angle at all points on the surface and form its boundary. Constant solid angle surfaces enable one to control the boundary slope and hence achieve an approximately constant span-to-height ratio as the span varies, making them structurally viable for shell structures. In addition, when the entire surface boundary is in the same plane, the slope of the surface around the boundary is constant and thus follows a principal curvature direction. Such surfaces are suitable for surface grids where planar quadrilaterals meet the surface boundaries. They can also be used as the Airy stress function in the form finding of shells having forces concentrated at the corners. Our technique employs the Gauss-Bonnet theorem to calculate the solid angle of a point in space and Newton's method to move the point onto the constant solid angle surface. We use the Biot-Savart law to find the gradient of the solid angle. The technique can be applied in parallel to each surface point without an initial mesh, opening up for future studies and other applications when boundary curves are known but the initial topology is unknown. We show the geometrical properties, possibilities and limitations of surfaces of constant solid angle using examples in three dimensions.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- Ander, Mats, 1964, et al.
(författare)
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Constructive alignment in solid mechanics courses by means of project assignments
- 2017
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Ingår i: 6: e Utvecklingskonferensen för Sveriges ingenjörsutbildningar, Chalmers tekniska högskola, 22 -23 november 2017.
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Konferensbidrag (refereegranskat)abstract
- This short text paper describes the procedure of planning and implementing project assignments as a means to constructive align courses in Solid mechanics at the school of Civil enginnering at Chalmers. The courses has now been given twice and we summarize our experiences so far.
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| 6. |
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| 7. |
- Ander, Mats, 1964, et al.
(författare)
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Development, accomplishment and evaluation of a project course in applied mechanics---Lessons learnt
- 2009
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Ingår i: Svenska mekanikdagarna, Södertälje 2009, 15-17-juni, Session 7:4-Utbildning, sid 99 (1 page abstract). ; , s. 99-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Development, accomplishment and evaluation of a project course in applied mechanics---Lessons learnt M. Ander , T. Grönstedt, T. Abrahamsson and G. JohanssonThis presentation concerns teaching and learning from working in projects within the Chalmers Master programme in Solid and fluid mechanics. The academic tradition requires teaching solid and fluid mechanics as separated subjects of applied mechanics. The researchers/teachers and students belonging to either discipline do not meet on daily basis and thus two separate cultures develop; CFD for fluids and FEM for solids.However, in industry today fresh engineers will meet challenges in multidisciplinary problems and they are expected to be able to know how to treat them. As a remedy to better prepare for their engineering profession, a project course in applied mechanics has been developed. The outline of the course follows the CDIO[1] learning approach: Conceive, Design, Implement and Operate. Starting off from back of the envelope calculations, where all students are required to address all disciplines, the project proceeds towards distinct specializations. The students, divided into groups of six to seven members, focus on ‘student specialists’ roles in solid/structural mechanics-FEM, fluid dynamics, and experimental modal analysis EMA, simulating a true multidisciplinary working environment. The projects studied incorporate a fluid structure interaction core problem, but are required to pose challenges within each specialisation. The task is formulated as a competition to find better solutions or as an investigation of existing methods to solve a problem at hand. The examination is based on individual assignments, group work, presentation of a final report and opposition. As resources for analysing the problems, the students have access to wind tunnel testing, EMA-equipment, computer rooms with commercial software for CFD and FEM. This year we have introduced the ANSYS workbench as a common platform for fluid–structure interaction simulations, allowing the teams to work more closely together. The student perspective is dominated by the urge to approach real world problems with industrial tools. A better contact and understanding between students as well as between teachers/researchers in the different disciplines of applied mechanics are achieved by this approach. Some outstanding challenges are the limited time frame of the course, the time consuming communication required within the teachers team and the student frustration arising from having to address open end problems. [1]www.cdio.org
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Ander, Mats, 1964
(författare)
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On Postbuckling Analysis of Thin-walled Structures Numerical and Statistical Approaches
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thin-walled structural elements, such as plates, shells and beams are important load carrying components in civil-, mechanical-, automotive- aeronautical- and marine engineering structures. In order to reduce the weight thin-walled structures are given an optimum design making them sensitive to unforeseen deviations in geometry, boundary conditions, material properties and applied loads. Therefore to assure safe, reliable structures accurate deterministic numerical methods for nonlinear analysis along with probabilistic methods are needed. In part one of the thesis an analytical probabilistic model is proposed for predicting the scatter of the buckling load of axially compressed thin linear elastic cylindrical shells with geometrical imperfections. The probability density function of the buckling load is deduced using an asymptotic relation according to Koiter between an assumed geometric imperfection and the buckling load. The scatter in the load-carrying capacity predicted by the proposed model, agrees well with experimental results from the buckling of cylindrical shells of a certain manufacturing tolerance class. In general, for complex structures, it is not possible to deduce closed form probability density functions for failure load predictions. Then a computer method using the Monte-Carlo simulation technique can be applied. However, the success of adopting a Monte Carlo technique strongly depends on the ability of the deterministic numerical method used to simulate the non-linear structural behavior. As an important step in developing a probabilistic computer simulation method geometrically non-linear thin structures with conservative deterministic one parameter loading has been studied in part two of the thesis and a computer code has been developed. The finite deformation theory for a linear elastic continuum is expressed in terms of displacement gradients. In the finite element approximation the displacement field is expressed only in translational variables. Standard linear shape functions are used for truss elements and p-hierarchical basis functions based on integrals of the Legendre polynomials are adopted for two-dimensional plane stress elements and for three-dimensional solid elements. The structural deformations are measured with respect to the initial undeformed reference configuration in a total Lagrange formulation. In order to follow the non-linear equilibrium path an incremental algorithm driven by the dominant displacement component is implemented. Numerical tests on a number of geometrically non-linear space trusses, a plane frame and a three dimensional beam show excellent agreement with analytical solutions as well as with numerical results presented in literature. The adopted p-hierarchical solid element formulation is demonstrated to work excellent for linear analysis of thin beams and shells.
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| 12. |
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| 13. |
- Ander, Mats, 1964, et al.
(författare)
-
Studenterna lyfter sig själva i Studion för Mekanik och Hållfasthetslära
- 2014
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Ingår i: KUL2014.
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Konferensbidrag (refereegranskat)abstract
- För att inom mekanik och hållfasthetslära öka studentens förståelse, väcka nyfikenhet, konkretisera fenomen och för att möjliggöra för studenten att erövra en handgriplig känsla har en Studio i Mekanik och hållfasthetslära med demonstrationsexperiment inrättats av studenter för studenter. Resultatet av en pilotstudie där studion för första gången använts presenteras.
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| 14. |
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| 15. |
- Andersson, Felicia, et al.
(författare)
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Resedagbok England/Wales - Arkitektur & teknik 2018
- 2018
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Denna resedagbok är en del av Arkitektur och teknik- studenternas förberedelse för årskurs 3 och särskilt en träning i att söka, upptäcka och iakkta arkitekturens komplexa sammanhang och de värden som kan skapas genom arkitektur. Under studieresan byggs ett grundmaterial till dagboken upp genom förberedda presentationer, gemensamma analyser, undersökande skisser och konstnärliga övningar. Studieresan följs upp och bearbetas vid seminarier och genom korsläsning av texter där studenterna uppmanas till ett personligt reflekterande hållningssätt. På så sätt blir dagboken ett levande dokument som visar vår glädje och nyfikenhet över de många broar och byggnader vi upplevt tillsammans, och ett dokument som vill locka oss och alla läsare till vidare upptäcktsfärder.
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| 16. |
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| 17. |
- Arkitektur & teknik, Årskurs 2, et al.
(författare)
-
På fötter genom England 2016
- 2016
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Denna resedagbok är en del av Arkitektur och teknik-studenternas förberedelse för årskurs 3 och särskilt en träning i att söka, upptäcka och iakkta arkitekturens komplexa sammanhang och de värden som kan skapas genom arkitektur. Under studieresan byggs ett grundmaterial till dagboken upp genom förberedda presentationer, gemensamma analyser, undersökande skisser och konstnärliga övningar. Studieresan följs upp och bearbetas vid seminarier och genom korsläsning av texter där studenterna uppmanas till ett personligt reflekterande hållningssätt. På så sätt blir dagboken ett levande dokument som visar vår glädje och nyfikenhet över de många broar och byggnader vi upplevt tillsammans, och ett dokument som vill locka oss och alla läsare till vidare upptäcktsfärder.
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| 18. |
- Halldin, A., et al.
(författare)
-
Implant stability and bone remodeling up to 84 days of implantation with an initial static strain. An in vivo and theoretical investigation
- 2016
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Ingår i: Clinical Oral Implants Research. - : Wiley. - 0905-7161 .- 1600-0501. ; 27:10, s. 1310-1316
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Tidskriftsartikel (refereegranskat)abstract
- ObjectivesWhen implants are inserted, the initial implant stability is dependent on the mechanical stability. To increase the initial stability, it was hypothesized that bone condensation implants will enhance the mechanical stability initially and that the moderately rough surface will further contribute to the secondary stability by enhanced osseointegration. It was further hypothesized that as the healing progresses the difference in removal torque will diminish. In addition, a 3D model was developed to simulate the interfacial shear strength. This was converted to a theoretical removal torque that was compared to the removal torque obtained invivo. Material and methodsCondensation implants, inducing bone strains of 0.015, were installed into the left tibia of 24 rabbits. Non-condensation implants were installed into the right tibia. All implants had a moderately rough surface. The implants had an implantation time of 7, 28, or 84days before the removal torque was measured. The interfacial shear strength at different healing time was estimated by the means of finite element method. ResultsAt 7days of healing, the condensation implant had an increased removal torque compared to the non-bone-condensation implant. At 28 and 84days of healing, there was no difference in removal torque. The simulated interfacial shear strength ratios of bone condensation implants at different implantation time were in line with the invivo data. ConclusionsModerately rough implants that initially induce bone strain during installation have increased stability during the early healing period. In addition, the finite element method may be used to evaluate differences in interlocking capacity.
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| 19. |
- Halldin, Anders, 1971, et al.
(författare)
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On a Constitutive Material Model to Capture Time Dependent Behaviour of Cortical Bone
- 2014
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Ingår i: World Journal of Mechanics. - : Scientific Research Publishing, Inc.. - 2160-049X .- 2160-0503. ; 4:11, s. 348-361
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Tidskriftsartikel (refereegranskat)abstract
- It is commonly known that cortical bone exhibits viscoelastic-viscoplastic behavior which affects the biomechanical response when an implant is subjected to an external load. In addition, long term effects such as creep, relaxation and remodeling affect the success of the implant over time. Constitutive material models are commonly derived from data obtained in in vitro experiments. However during function, remodeling of bone greatly affects the bone material over time. Hence it is essential to include long term in vivo effects in a constitutive model of bone. This paper proposes a constitutive material model for cortical bone incorporating viscoelasticity, viscoplasticity, creep and remodeling to predict stress-strain at various strain rates as well as the behavior of bone over time in vivo. The rheological model and its parameters explain the behavior of bone subjected to longitudinal loading. By a proper set of model parameters, for a specific cortical bone, the present model can be used for prediction of the behavior of this bone under specific loading conditions. In addition simulation with the proposed model demonstrates excellent agreement to in vitro and in vivo experimental results in the literature.
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| 20. |
- Halldin, A., et al.
(författare)
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Simulation of the mechanical interlocking capacity of a rough bone implant surface during healing
- 2015
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Ingår i: BioMedical Engineering Online. - : Springer Science and Business Media LLC. - 1475-925X. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: When an implant is inserted in the bone the healing process starts to osseointegrate the implant by creating new bone that interlocks with the implant. Biomechanical interlocking capacity is commonly evaluated in in vivo experiments. It would be beneficial to find a numerical method to evaluate the interlocking capacity of different surface structures with bone. In the present study, the theoretical interlocking capacity of three different surfaces after different healing times was evaluated by the means of explicit finite element analysis. Methods: The surface topographies of the three surfaces were measured with interferometry and were used to construct a 3D bone-implant model. The implant was subjected to a displacement until failure of the bone-to-implant interface and the maximum force represents the interlocking capacity. Results: The simulated ratios (test/control) seem to agree with the in vivo ratios of Halldin et al. for longer healing times. However the absolute removal torque values are underestimated and do not reach the biomechanical performance found in the study by Halldin et al. which might be a result of unknown mechanical properties of the interface. Conclusion: Finite element analysis is a promising method that might be used prior to an in vivo study to compare the load bearing capacity of the bone-to-implant interface of two surface topographies at longer healing times.
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| 21. |
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| 22. |
- Henrysson, Erica, 1987, et al.
(författare)
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Conceptual Design and Analysis of Membrane Structures
- 2016
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Ingår i: Proceedings of 29th Nordic Seminar on Computational Mechanics – NSCM29.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this work one approach for formfinding and analysing tension membranestructures is described. Focus has been on the conceptual stage. For this the computersoftware SMART Form has been further developed, enabling the possibility to do real-timeformfinding and analysis of fabric structures. The software is based on a method where theorthotropic membrane is modeled with a triangular mesh, where the mass is lumped on thenodes. As a computational tool dynamic relaxation is used to find the static equilibriumconfiguration for the structure. The advantage with this is that there is no need for formulationand manipulation of matrices common in the finite element method.
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| 23. |
- Hilmersson, Joel, 1992, et al.
(författare)
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Isogeometric analysis and form finding for thin elastic shells
- 2019
-
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. 153-160
-
Konferensbidrag (refereegranskat)abstract
- Recent developments within the design of shells have seen an increased interest in utilizing active bending as form giving procedure [1]. This enables complex structures to be built from simple off-the-shelf materials. However, forming bending-active structures is highly dependent on the material properties, which makes the design process reliant on either physical testing or digital simulations. An associated problem with the simulation of this behavior is the lack of integration between modeling and analysis in conventional simulation techniques, a crucial concern since the final design is always an equilibrium shape with requirements on both structural and spatial integrity. IsoGeometric analysis (IGA) is a method that aims to bridge precisely that gap between analysis and design, making it a suitable method for bending active structural design. This paper suggests an approach to the modeling and digital design of actively bent shells using the implementation of nonlinear IGA. Further on, two different ways of controlling the geometry, either by tracing the process forwards or backwards during the construction procedure are proposed. Tracing the process forwards returns an implicitly controlled shell geometry through stepwise displacement of the boundaries of a at sheet. However, as a design approach, one is often interested in explicitly controlling the final geometry by a backwards tracing. This allows the designer to start from a desired outcome and instead tailor the material to approximate this desired form. The procedure is tested in a case study where a combination of both forwards and backwards tracing is included. Both processes apply the Kirchhoff-Love shell theory [6] and uses the total Lagrangian formulation for the nonlinear computations.
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| 24. |
- Hörteborn, Erica, 1987, et al.
(författare)
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Architectural Knitted Windbreaks for Improved Wind Comfort in the City: A Wind Tunnel Study of Custom-Designed Porous Textile Screens
- 2023
-
Ingår i: Buildings. - : MDPI AG. - 2075-5309. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- There is a need to shield from the wind to improve pedestrian comfort in urban environments. Perforated windbreaks, such as fences, vegetation or textile nets, have proven to be an efficient solution, whereas knitted textiles have not yet been explored. The purpose of this study was to evaluate the capacity of knitted textile windbreaks to reduce wind velocities, to inform further research and promote wider architectural applications. Five custom-knitted textile prototypes, representing fragments of textile windbreaks, were tested in a wind tunnel and compared against a perforated and a nonperforated solid board. Forces on the models, as well as upstream and downstream velocities, were measured. The results indicate that the optimal optical porosity of knitted windbreaks should be around 10%, which differs from the porosity for perforated windbreaks recommended by prior studies. Moreover, it was observed that a textile windbreak knitted using the drop-stitch technique efficiently reduces the wind, while not generating a large drag force. Furthermore, the drag coefficient for the knitted windbreak is reduced with increased windspeed. With this, the presented study demonstrates that knitted structures exposed to wind influence have the functional potential of becoming efficient windbreaks, thus improving wind comfort and aesthetic user experience in the urban space.
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| 25. |
- Johansson, Anders, 1974, et al.
(författare)
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Simulation of wheel-rail contact and damage in switches & crossings
- 2011
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 271:1-2, s. 472-481
-
Tidskriftsartikel (refereegranskat)abstract
- A methodology for the simulation of degradation of rail profiles in switches & crossings (S&C) is presented. The methodology includes: simulation of dynamic vehicle-track interaction considering stochastic variations in input data (such as wheel profile, train speed and wheel-rail friction coefficient), simulation of wheel-rail contacts accounting for non-linear material properties and plasticity, and simulation of wear and plastic deformation in the rail during the life of the S&C component. The methodology is demonstrated by predicting the damage of a switch rail profile, manufactured from R260 steel, when exposed to freight traffic in the diverging route (facing move). In particular, the consequences of increasing the axle load from 25 tonnes to 30 tonnes are studied.
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| 26. |
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| 27. |
- Olsson, Jens, 1985, et al.
(författare)
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Adaptive bone re-modelling for optimization of porous structural components
- 2022
-
Ingår i: Proceedings of the IASS Annual Symposium 2022 and APCS 2022.
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a speculative application of adaptive bone-remodelling to generate porous structures for building components using a numerical meshless method. We hypothesize that such porous structures could then be 3d printed to achieve light weight and material efficient building components. The meshless model is built up of particles that are connected by arms to their neighbours within a distance called a horizon. The re-modelling adaption is then based on the ratio of arms strain over average arm strain which is mapped to a third-order polynomial function and used to scale the arm stiffness in a way that mimics the resorption and densification of bone tissue. The method is shown to work rather well in the recreation of the structural patterns found in cross section of a femur bone. The translation to a geometry which can be manufactured with additive techniques is not tackled specifically and suggest a direction for further work.
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| 28. |
- Olsson, Jens, 1985, et al.
(författare)
-
Sculptural form finding with bending action
- 2017
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Ingår i: International association for shell and spatial structures (IASS).
-
Konferensbidrag (refereegranskat)abstract
- This paper demonstrates a method development for integration of bending action into the form finding process. The aim has been to facilitate the designer with means to compromise between structural efficiency and sculptural freedom for grid shell type of structures.The analysis is carried out using Dynamic Relaxation (DR) and to achieve bending capability, the base element implementation is a 12 degrees of freedom beam where the DR is solving for both translations and rotations [2]. For purpose of validation, stress based utilization is calculated based on Eurocode 3 equations which are simplified to allow for separation of axial and bending utilization [3]. A stress based sizer is also implemented to enable comparison based on tonnage.The methods presented are derived from the principles behind stiffness control and force-density control form finding, commonly applied for compression and tension structures respectively [1]. The common denominator being that they are all driven by a form finding load case, where the user can specify various combinations of axial- and bending utilization limits for the elements, to which the form adapts as it tries to find equilibrium of internal and external forces and moments.None of the methods was found to satisfy all requirements for a useful general purpose shell design tool. The main issue was found to be wrinkling of the initial geometry when the need for drastic change in element length, required for a structurally unsound free form surface changing shape in the form finding process, is being opposed by the relatively high axial stiffness of a beam. This is not usually an issue when form finding with elastic springs that undergo large deformations in the process.Conclusively there might be merit for a form finding element that allows for large axial deformation to avoid the wrinkling problem but has the bending properties of a beam. From a workflow point of view, the implementation of elements with bending capability was demonstrated to be useful for form exploration, particularly when combined with automatic sizing. The separation of bending and axial utilization was also found useful from a form evaluation point of view.
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| 29. |
- Olsson, Jens, 1985, et al.
(författare)
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The numerical simulation of standard concrete tests and steel reinforcement using force flux peridynamics
- 2023
-
Ingår i: Structural Concrete. - : Wiley. - 1751-7648 .- 1464-4177. ; 24:2, s. 2071-2092
-
Tidskriftsartikel (refereegranskat)abstract
- Peridynamics is a numerical particle-based solid mechanics method that enables the simulation of brittle and quasi-brittle materials, as well as ductile materials. It allows cracking to appear spontaneously in the arms joining the particles and can therefore be used to simulate progressive fracture. In this article, we apply our version of peridynamics, which we call force flux peridynamics, to the simulation of concrete where the appearance of cracks plays an important role in the global mechanical properties. It is not difficult to modify the material parameters in peridynamics to achieve a given tensile strength or a given compressive strength. However, it is much more difficult to choose parameters which will model all the strength parameters of a material within the same model. When concrete fails in compression it may split or spall showing a complex relationship between compressive and tensile failure. We therefore set ourselves the simple task of producing a single peridynamics model which can predict the stiffness and strength behavior of concrete in standard compression and tension tests for which we chose the American Society for Testing and Materials standards for the cylinder compression test, the split cylinder test, and the modulus of rupture test. A parameter sensitivity study was performed based on the cylinder compression test to tune the key peridynamics parameters that determine the global material behavior. The compressive and tensile strengths were then determined from the combined simulation data. While the fracture modes, crack branching pattern and also the stress–strain curve show promising results, the maximum tensile strength was found to be significantly larger than physical experiments suggest. This is probably due to imperfections within real concrete at the interface between aggregate particles and cement paste and it shows that the detailed numerical modeling of the failure of concrete is highly complex with a large number of unknown material parameters.
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| 30. |
- Olsson, Jens, 1985, et al.
(författare)
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The Use of Peridynamic Virtual Fibres to Simulate Yielding and Brittle Fracture
- 2021
-
Ingår i: Journal of Peridynamics and Nonlocal Modeling. - : Springer Science and Business Media LLC. - 2522-896X .- 2522-8978. ; 3:4, s. 348-382
-
Tidskriftsartikel (refereegranskat)abstract
- The forces in the ‘arms’ joining the particles in a peridynamic analysis depend upon the state of stress in the equivalent continuum and the orientation, length and density of the arms. Short and long arms carry less force than medium length arms as controlled by the weighting kernel. We introduce an intermediate step of imagining a mat of long fibres in which the fibre forces only depend upon the stress, the fibre orientation and the length of fibres per unit volume without the added complexity of the arm lengths. The effect of the arm lengths can then be considered as a separate exercise, which does not involve the continuum properties. The arm length is proportional to size of the particles and the separation of length from the state of stress allows for modelling of variable particle density in the discretisation of a problem domain, which enables computationally efficient accurate analysis. We then introduce the concept of arm elongation to fracture in order to model surface energy in fracture mechanics. This means that shorter arms have a larger strain to fracture than longer arms. The numerical implementation demonstrates that this produces a fracture stress that is inversely proportional to the square root of the crack length as predicted by the Griffith theory.
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| 31. |
- Olsson, Karl-Gunnar, 1955, et al.
(författare)
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Architecture and Engineering - education of Form and Force
- 2019
-
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. 145-152
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Konferensbidrag (refereegranskat)abstract
- Inspired by the work and attitudes of architects and engineers like Jorg Schlaich, Renzo Piano, Piero Luigi Nervi, Sverre Fehn, Ted Happold, and environments like ILEK in Stuttgart and ETH in Zurich, a vision of a new kind of architects and engineers arose at Chalmers University of Technology in the early 2000. With support from the university and the branch, a double degree Architecture and Engineering programme was developed. Since the programme started in 2006 it has been a very popular programme, and among all Swedish MSc in Engineering and Master of Architecture programmes it has almost every year been the most difficult programme to get admitted to. The concept of the programme is a 180 ects (European Credit Transfer and Accumulation System) bachelor's degree, where the fundamentals from the engineering science: mathematics, mechanics, physics and materials, is combined with history of architecture and engineering, artistic explorative courses, and the fundamentals of the architectural design process. After three years the students can choose to continue for a Master of Science in Engineering with different possible directions, from mathematics and data science to industrial ecology, acoustics, management, structural engineering, and building technology, or to continue for a Master of Architecture. For the latter they need 150 etcs minimum in pure architectural design projects. In this paper the basic concepts of the programme, the culture developed around it and the strengths we can experience in the examined students will be discussed and reflected. Today students from the programme can be found at architecture and engineering companies all over the world and are appreciated for their ability to address complex architectural and engineering design issues with attitudes, insights and skills from the both professions.
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| 32. |
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| 33. |
- Safari Hesari, Puria, 1989, et al.
(författare)
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On the implementation of isogeometric analysis for thin shells
- 2017
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Ingår i: J. Hölsberg, N.L. Pedersen (Eds.), 30th Nordic Seminar on Computational Mechanics, NSCM-30, 2017.
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Konferensbidrag (refereegranskat)abstract
- This paper concerns the implementation of Isogeometric Analysis (IGA)for analysis of free-form shells using Kirchho-Love theory. The objective is the study of accuracy and convergence rate obtained with IGA compared to classic FEA on a per-degree-of-freedom basis. Findings suggest that the IGA model is more accurate forthe considered problems, due to an accurate geometric description. By utilization of high continuity over element boundaries, IGA also exhibits superior rates of convergencecompared to classic FEA. These advantages are also discussed in relation to the application of the implemented model to analyse a real shell structure.
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| 34. |
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| 35. |
- Sehlström, Alexander, 1987, et al.
(författare)
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Architectural design methods used in engineering Master's thesis projects
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- By letting structural engineering thesis students explore questions using architectural design methods, they creatively and systematically addressed holistic questions while maintaining a technical depth. The approach may serve as a model to increase engineering students' ability to insightfully contribute to solutions for complex societal problems.
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| 36. |
- Sehlström, Alexander, 1987, et al.
(författare)
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On multi-objective topology optimization and tracing of Pareto-optimal structures
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper an sequential linear programming (SLP) algorithm for solving multi-objective topology optimization problems have been implemented and numerical results for a design domain have been calculated. Examples shows that the SLP algorithm performs similar to the single objective ptimality criteria algorithm but also that some further work is needed.
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| 37. |
- Sehlström, Alexander, 1987, et al.
(författare)
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Prestressed gridshell structures
- 2017
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Ingår i: Proceedings of the IASS Symposium 2017.
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Konferensbidrag (refereegranskat)abstract
- This paper describes a method for the form finding of shell structures composed of both compression and tension members which may lie in one layer or two layers. The length of some of the members can be constrained to a fixed length yielding some control of the resulting form found shape. The form finding is accomplished by adjusting the nodal positions until an equilibrium state is reached using dynamic relaxation. If part of a structure is unstable due to compression forces, then a negative mass must be used in the dynamic relaxation. The length constraint is met by adjusting the force density during form finding, again using dynamic relaxation. Finally, case studies are presented where the applied load and the prestress is used to govern the form found shape.
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| 38. |
- Tsigkari, Martha, et al.
(författare)
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Form Finding Nodal Connections in Grid Structures
- 2018
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Ingår i: Proceedings of the IASS Symposium 2018.
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Konferensbidrag (refereegranskat)abstract
- Nodes for grid structures are often manufactured in a rather material intensive and inefficient way, increasing the weight of the structure and thus the load. Recent development of additive manufacturing techniques, have resulted in a rising interest in large-scale metal 3D printing. Topology optimization has become the obvious companion in the design of structural parts for 3D printing, and rightfully so. The technique is demonstrably able to provide material efficient solutions and is well suited for a manufacturing technique with few formal restrictions. However, from a designer’s perspective one could argue that topology optimization have some limitations. Like other “automated processes”, it tends to take over and does not leave much room for other form drivers. This paper presents an alternative method for designing material efficient nodes in grid structures that builds on the conventional form-finding techniques, usually applied to create minimal surface tensile structures or gravity shell like structures. The technique works by modelling the node as a hollow shell with a mesh, applying a set of tensile forces derived from the structural action from elements adjacent to the node (where compression is converted to tension) and running a form finding simulation. After the simulation, the shell is then thickened and analysed for the real load case (which consider both tension and compression) using FE-analysis. The benefit of such technique is that the designer has control over the topology of the design which enables more creative control and free exploration of a range of design variations. The form finding is done using dynamic relaxation and introduces spline elements with bending capability to control deviation from the pure spring network solution.
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| 39. |
- Wallander, Linda, et al.
(författare)
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Textile Informed Structures - How to Braid a Roof, Translating the logic of textile structure into the scale of architecture
- 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. 2756-2763
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Konferensbidrag (refereegranskat)abstract
- There is a great variety of textiles materials, both in terms of the behaviour of the fibres they comprise and the assembly methods used to construct them. Hence, the definition of textile is expanded nowadays from including only conventional fabrics to encompassing surfaces with structures that follows the logic of textiles.[1] One can then refer to textile as a repetition of bindings, or joints, forming a non-hierarchical surface. Analogies between classical textile assembly methods of interlacing threads (triaxial weave and bobbin lace) and architectural structural systems are explored in this research. Similar to the work of Snelson the internal structural logic is identified by the joints used, and these typologies are mapped onto structures.[2] The resulting modules aim to be used for the assembly of structures in the scale of architecture. Like the assembly logic of the textiles, these structures have the potential to grow in all directions depending on spatial requirements while still retaining some kinetic properties. Subsequently, the result proposes two concepts: firstly a tensegrity weave structural system- combining triaxial woven textiles and tensegrity; secondly a reciprocal lace system where a basic pattern of bobbin lace is mapped onto reciprocal structures. The final concepts propose intriguing load bearing systems that illustrate the possibility to design and construct temporary structures able to seamlessly span irregular spaces.
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