| 1. |
- Girhammar, Ulf Arne, et al.
(författare)
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Finite element modelling of shear walls using connector shear elements based on continuum plasticity
- 2010
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Ingår i: Proceedings of the Tenth International Conference on Computational Structures Technology. - Stirlingshire, Scotland : Civil-Comp Press. - 9781905088386
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Konferensbidrag (refereegranskat)abstract
- Light-frame timber buildings are often stabilised against lateral loads by using diaphragm action of roofs, floors and walls. The mechanical behaviour of the sheathing-to-timber joints has a significant impact on the structural performance of shear walls. Most sheathing-to-framing joints show non-linear load-displacement characteristics with plastic behaviour. This paper is focused on the finite element modelling of shear walls. The purpose is to present a new connector shear element based on the theory of continuum plasticity. The incremental load-displacement relationship is derived based on the elastic-plastic stiffness tensor including the elastic stiffness tensor, the plastic modulus, a function representing the yield criterion and a hardening rule, and another function representing the plastic potential. The plastic properties are determined from experimental results obtained from testing actual connections. Load-displacement curves for shear walls are calculated using the connector shear model and they are compared with experimental and other computational results. Also, the ultimate horizontal loadcarrying capacity is compared to results obtained by an analytical plastic design method. Good agreements are found.
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| 2. |
- González, Ignacio
(författare)
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The validity of simplified dynamic analysis of the new årsta bridge response to moving trains
- 2010
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Ingår i: Proceedings of the Tenth International Conference on Computational Structures Technology. - 9781905088386
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Konferensbidrag (refereegranskat)abstract
- Dynamic simulations are necessary to predict the behaviour of bridges loaded by high-speed trains. These simulations are expensive, require a lot of computational power and are very sensitive to input parameters that are difficult to estimate. If the dynamic behaviour of the bridge could be accurately predicted by simpler models, time and resources could be saved. In this paper, a 2D finite element model of a complex bridge is developed. The results obtained are compared with those obtained by other more complex 3D models as well as with the actual response of the bridge measured in situ by a long term monitoring system. Furthermore, based on the measured results, some model parameters are updated. The main aim of this study is to check the validity of simplified models and simplified analysis of the response of complex bridges to moving trains, as well as the capabilities of updating in enhancing the model accuracy.
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| 3. |
- Mauritsson, Karl, 1980, et al.
(författare)
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Dynamic equations for an orthotropic piezoelectric plate
- 2010
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Ingår i: Proceedings of the tenth international comference on computational structures technology, Valencia 14-17 September 2010. - 9781905088386
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Konferensbidrag (refereegranskat)abstract
- Piezoelectric materials have been used widely in applications for sensing and actuation purposes in recent years. As piezoelectric sensors and actuators usually are thin in comparison to the relevant wavelengths, the analysis of thin piezoelectric layers has attracted considerable research interest. The present work considers the derivation of new plate equations and the corresponding edge boundary conditions for an orthotropic piezoelectric plate. Here, power series expansions in the thickness coordinate for the displacements and the electric potential are stated, that lead to recursion relations among the expansion functions. These recursion relations are important as all fields hereby can be expressed in a finite number of expansions functions without performing any truncations. Moreover, the recursion formulas involve no approximations since they stem from the definition of the series expansions and are as such exact. Using the recursion relations in the boundary conditions on the surfaces and along the edges, a set of plate equations and the corresponding edge boundary conditions are obtained in a systematic fashion. Hence the surface boundary conditions constitute the plate equations of motion, and as such the lateral boundary conditions are exactly fulfilled. These plate equations can be truncated to any order in the thickness and it is believed that they are asymptotically correct, based on experience for other structures. Contrary to most traditional theories, there is no need to assume kinematical simplifications based on various engineering assumptions; neither for the equations of motion nor for the corresponding edge boundary conditions. Note that various sorts of series expansion procedure have been developed by others, but there are several differences in the derivation procedure among these works, such as in the series expansion formulation, the development of recursion relations or in the truncation process. The plate theory developed is given explicitly for flexural motion using a low order truncation. These equations of motion resemble the Mindlin type plate equations, albeit the present theory involves some further terms as well as no correction factors. The accuracy of the plate theory is displayed for the displacement, electric and stress fields, where comparisons are made with exact and traditional approximate theories. These results show that the present asymptotic plate theory renders considerably more accurate results than the Kirchhoff and the Mindlin theories.
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| 4. |
- Pettersson, Robert, et al.
(författare)
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Free-time optimization of targeted movements based on temporal finite element approximation
- 2010
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Ingår i: Proceedings of the Tenth International Conference on Computational Structures Technology. - : Civil-Comp Ltd. - 9781905088386
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Konferensbidrag (refereegranskat)abstract
- Previous work by the authors has shown that temporal finite element approximations can be used for the representation of targeted optimal control problems, and that a weak equilibrium formulation leads to robust and efficient simulations. A free-time formulation is now introduced to increase the degree of freedom in finding optimal movement. The timescale parameter in relation to the objective function is discussed and verified by numerical examples. For movements with partial contact multiple phases with different mechanical properties are included. The free-time formulation allows these phases to be determined by the optimization. A three-phase two-foot high jump is simulated where the movement optimization finds a prior motion preparing for the subsequent phases with different mechanical properties.
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