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| 2. |
- Girhammar, Ulf Arne, et al.
(författare)
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Exact static analysis of partially composite beams and beam-columns
- 2007
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Ingår i: International Journal of Mechanical Sciences. - Oxford : Pergamon Press. - 0020-7403 .- 1879-2162. ; 49:2, s. 239-255
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Tidskriftsartikel (refereegranskat)abstract
- The ordinary differential equations and general solutions for the deflection and internal actions and, especially, the pertaining consistent boundary conditions for partially composite Euler-Bernoulli beams and beam-columns are presented. Static loading conditions, including transverse and axial loading and first- and second-order analyses are considered. The theoretical procedure is applicable to general loading and boundary conditions for uniform composite beams and beam-columns with interlayer slip. Further, the exact closed form characteristic equations and their associated exact buckling length coefficients for composite Columns with interlayer slip are derived for the four Euler boundary conditions. It is shown that these coefficients are the same as those for ordinary fully composite (solid) columns, except for the Euler clamped-pinned case. For the clamped-pinned case, the difference between the exact buckling length coefficient and the corresponding value for solid Columns is less than 1.8%, depending oil the so-called composite action parameter and relative bending stiffness parameter. Correspondingly, the maximum deviation between the exact and approximate buckling load is at most 2.5%. These small differences can in most practical cases be neglected. Also, the maximum theoretical range for the relative bending stiffness for partially composite beams and beam-columns is derived. An effective bending stiffness, valuable in the determination of the critical buckling load for partially composite members, is derived. This effective bending stiffness is also Suitable for analysing approximate deflections and internal actions or stresses in composite beams with flexible shear connection. The beam-column analysis is applied to a specific case. The difference in the approaches to the first- and second-order analysis is illustrated and the results clearly show the magnification in the actions and displacements due to the second-order effect. The magnification of the internal axial forces is different from magnifications obtained for the other internal actions, since only that portion of an internal axial force that is induced by bending is magnified by the second-order effect.
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| 3. |
- Girhammar, Ulf Arne, et al.
(författare)
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Dynamic analysis of composite members with interlayer slip
- 1993
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Ingår i: International Journal of Solids and Structures. - : Pergamon Press. - 0020-7683 .- 1879-2146. ; 30:6, s. 797-823
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Tidskriftsartikel (refereegranskat)abstract
- The exact and approximate analysis of composite members with partial interaction and subjected to general dynamic loading are presented. General closed-form solutions for the displacement functions and the various internal actions in the composite elements are presented for both the exact and approximate cases. The solutions reduce to the well-known values for the extreme cases of interlayer connection: non-composite and full composite action, respectively. An approximate solution for the eigenfrequencies in the exact analysis procedure is proposed and evaluated by comparison with the exact solution. These solutions show the effect of interlayer connection on the eigenfrequency. The exact and approximate analysis procedures are applied to simply-supported beams subjected to impulsive and step loadings to illustrate the difference in the solutions obtained by the two procedures. Very good agreement is obtained between the results of exact and approximate analysis of these particular cases
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| 4. |
- Girhammar, Ulf Arne, et al.
(författare)
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Generating geometric configurations of Varax domes using Formian
- 2008
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Ingår i: Proceedings of the Ninth International Conference on Computational Structures Technology, Athens - Greece, 2-5 September 2008. - Stirling. - 9781905088232
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Konferensbidrag (refereegranskat)abstract
- Varax domes (domes with variable axes) are lattice domes, efficient space structures, built up of a triangulated network, where all the beams lie in great circle planes. Formian is a professional program, a powerful tool for generating the geometry of space structures. Varax types of domes can presently not be handled by Formian. New functions and procedures have been developed to be implemented into Formian to enable generation of Varax dome configurations also. In this paper the procedures and applications of this Formian program, adapted to generate different configurations of Varax domes, are described and illustrated. The computer schemes necessary to accomplish various dome shapes are illustrated. Varax domes with different number of sectors and divisions of the arc length and the bottom beam are presented. Also, different arrangements of the purlins are illustrated along with an example of applying inherent Formian functions to generate special shape effects on Varax domes. The generated coordinates for the Varax domes can then easily be exported as input variables to other programs for finite element analyses
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| 5. |
- Pan, Danhua, et al.
(författare)
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Effect of ring beam stiffness on behaviour of reticulated timber domes
- 2005
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Ingår i: International Journal of Space Structures. - : SAGE Publications. - 0956-0599 .- 2059-8033. ; 20:3, s. 143-160
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Tidskriftsartikel (refereegranskat)abstract
- Domes are efficient structural systems for long clear-span buildings. The introduction of laminated timber highlighted the economic advantages of this material and led to the use of timber domes even for very large spans. In this paper, reticulated timber domes of triangular network shape with decking and bottom tension ring are considered. These types of domes have high stiffness in all directions along the surface and are kinematically stable. The dome is subjected to uniformly distributed load over the entire structure. The dome model is generated with a preprocessor program called DOME-IN and analysed with ABAQUS. The focus of this paper is to evaluate the behaviour of reticulated timber domes with respect to different stiffnesses of the bottom ring beam, here defined as a non-dimensional ring beam area parameterr*, which is shown to be a very well adapted design parameter for the ring beam. As far as global buckling is concerned, the critical pressure is sensitive to the bottom ring beam stiffness only if the latter is within a certain range. In terms of design, the stiffness of the ring beam should exceed A 2* > 2 in order to utilise the full buckling load capacity of the dome system itself. The maximum deflection, normal forces and bending moments versus the ring beam area parameter are also evaluated. The maximum values of the deflection and the internal actions next to the bottom ring are very sensitive to the bottom ring beam stiffness only if the latter is less than about Ar* < 10. A recommended value for the design of the bottom ring beam is Ar* > 20.
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| 7. |
- Pan, Danhua, et al.
(författare)
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Influence of geometrical parameters on behaviour of reticulated timber domes
- 2003
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Ingår i: International Journal of Space Structures. - : SAGE Publications. - 0956-0599 .- 2059-8033. ; 18:2, s. 105-122
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Tidskriftsartikel (refereegranskat)abstract
- Domes are very efficient structural systems for long clear span buildings. The introduction of laminated timber highlighted the economic advantages of this material and led to the use of timber domes even for very large spans. In this paper, reticulated timber domes of triangular network shape with decking and bottom tension ring are considered. These types of domes have high stiffness in all directions along the surface and are kinematically stable. The dome is subjected to uniformly distributed load over entire structure. The dome model is generated with a preprocessor program called DOME-IN and analysed with ABAQUS. The focus of this paper is to evaluate the behaviour of reticulated timber domes with respect to: (a) height-diameter ratio of the dome, H/D; (b) straight relative curved types of main beams in the triangular networks versus mesh density; (c) perpendicular relative parallel types of purlin arrangements in the triangular networks versus the number of purlins; and (d) mesh density of main network members or size of triangular networks. The influence of these parameters on relative maximum deflection of the dome, relative critical pressure for global buckling of the dome, relative maximum axial forces and relative maximum bending moments in the network members, is evaluated. It is found that: (a) the optimum height-diameter ratio is H/D ≈ 0.3; (b) that straight beams in the triangular networks are preferred to curved beams, especially for higher mesh densities;(c) that purlins perpendicular to the latitudinal beams are preferable to purlins parallel to the latitudinal beams if there is a decking that provides bracing to the system; and (d) mesh densities with six sectors (n=6) (lowest number of practical interest) and as many divisions of the arc beam and of the sector of the ring beam (m = k ≥ 4), which is necessary in order to meet the design criteria for the dome, can be recommended.
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