Papers by Keyword: Nonlinear

Abstract: This paper presents the predicted results of nonlinear time history analysis of 11 storey (G+10) Reinforced Concrete (RC) residential building under the effects of a strong earthquake. The paper includes studying the effects of using Lead Rubber Bearings (LRB) as base isolators to improve the performance of RC building to sustain the impact of an earthquake. It also includes the effects of the infill panels on the overall dynamic response of both fixed base and base-isolated buildings subjected to a strong earthquake. The main results that are presented in this study include the variation of roof acceleration, roof displacement, base shear with time. The effects of using LRB and including the infill panels on the storey drift are also presented. Maximum reduction in the story drift was obtained when infill panels are included in the analysis of the base isolated building. The inclusion of the infill panels has only marginal effects on the variation of roof displacement with time when the building is isolated by LRB. The main important improvements that emerged from using LRB as well as the infill panels in the analysis are the reduction of inelastic energy and upgrading the elastic one that is summed up along the period of the earthquake.

Abstract: In this article, nonlinear analysis of the composite plates and shells were carried out using the semiloof shell element. The finite element formulation is based on Green strains and Piola-Kirchhoff stresses. The nonlinear solution procedure was implemented to study the nonlinear behaviour of composite plates and shells. Due to coupling effect in composite plate and shells under in-plane load, pre-buckling displacement is significant and hence the behaviour is nonlinear. A verification study has been carried out to establish the efficiency of the present model. Since the margin of factor of safety is less in aerospace application, the detailed understanding and study of pre-buckling displacement is necessary for the designer.

Abstract: Considering the effects of strain rate, the nonlinear dynamic response of two reinforced concrete(RC)structuresisstudied under seismic excitationsin this paper. Firstly, based on the model in a shaking table test, a three-dimensional finite element model of RC frame-shear wall structural model subjected to both horizontal and vertical component seismic excitations is established. The structural model is a three-story RC frame-shear wall structure, which consists of RC slabs, RC columns and transverse spandrel beams.Afringeframe is infilled by a RCshear wall.Then, According to the practice engineering, a multi-story RC frame structure is also established. Finally, the dynamic response of the structures is investigated using nonlinear seismic analytical method considering the effects of strain rate. These results may provide a reference for seismic design of RC structure.

Abstract: There are a few years, it has become the use of artificial discs and effectively to compensate for damaged discs in humans due to the eccentric load applied on the spine. As we know very well that the success of a disc implantation depends strongly on the initial stability of the implant and the integration of the bone tissue of the vertebrae with these discs in the long term. Due to the optimal distribution of mechanical stresses in the surrounding bone. It is for this reason that the search for reasonable solutions to compensate the damaged disk and reduce the stresses in the cortical bone and spongy has become a very important research axis. Several alternatives have been studied, including implant design, prosthesis geometry, prosthetic components and biomaterials used. In this regard, we have proposed two new models for some innovative artificial disks by some of the biomechanics researchers and we have installed these discs between the two vertebrae L5 and S1 of the spine, to ensure spinal stability and avoid slipping, we installed a posterior attachment system (6 screws plus 2 rods) at the pedicular levels of the lumbar vertebra (S1-L5, L5-L4).It is for this technique that we have used finite elements in three dimensions and using the software ANSYS to know the extent of the realization of these discs under the influence of the load applied to them. The numerical results show that these disks played a very important role in the absorption of the stresses and to minimize, On the other hand, the lumbar inter-somatic cage (Model II) filled with cancellous bone is too great a role in reducing the stress compared to another synthetic (Model I) disc. In general, the new model of the inter-somatic cage filled with cancellous bone and reinforced by a posterior fixation system has given a lower level of stress in the cortical bone and the spongy bone of the lumbar vertebra (L5) compared to the healthy disk (D1).

Abstract: Glassy shape memory polymer materials are applied successfully in biomedical fields due to their large recovery deformation, excellent biocompatibility and unique biodegradability. To predict the thermo-mechanical behavior of glassy shape memory polymers in biomedical devices accurately, a reasonably three-dimensional thermo-mechanical constitutive model must be established firstly. A one-dimensional linear-elastic constitutive model proposed by Tobushi et. al. (1997) was extended to capture the loading level dependent degradation of shape memory effect by introducing new nonlinear evolution equations with threshold values. Comparisons between experiments and simulations were carried to validate the extended model. Simulation results agree with experiments well, especially for the high loading levels.

Abstract: This paper examines a model for coupled heat and mass transfer for freezing in a porous matrix with Dirichlet and convective boundary conditions. Variables include porosity, heat transfer coefficients, thermal and mass diffusivity, density, latent heat and boundary temperatures. It is shown that heat and mass transfer balance at the interface can affect stability. The effect of boundary conditions on the velocity of freezing is computed for some cases, and applications to physical problems highlighted

Abstract: This paper presents an analysis into the computational results for modelling of a two degree-of-freedom nonlinear vibrating structure. Fast Fourier Transformations, Short Time Fourier Transformations, Hilbert Transformations and wavelets are used to model this system. These techniques aim to locate and quantify the nonlinear behaviour of the system. Coulomb friction was detected with a number of these techniques, however other nonlinearities could not be detected. From the analysis conducted, improved computational methods are necessary for the detection of nonlinearities.

Abstract: As transmission tower system has the characteristics of large-span and spatial truss structure, the study of the reliability is also developed on the basis of space truss research and large-span structure system. As simple and suitable, RSM (response surface method), in particular, quadratic response surface without considering the cross term is often used in reliability calculation. However, strong nonlinear limit that corresponding to a complex surface, the accuracy of quadratic response surface is inadequate, causing greater reliability estimation error. High-order response surface solves it well. To this end, based on univariate analysis of multivariate function, a reasonable algorithm as to assure that the form of higher-order response surface is proposed; on the algorithm is verified by given examples, the result shows better accuracy and efficiency .

Abstract: In this paper, a fuzzy state observer with an appropriate adaptive law is developed for a class of uncertain nonlinear system. The uncertain nonlinear system is represented by Takagi-Sugeno (T-S) fuzzy model, and the adaptive law is derived based on Lyapunov synthesis approach. It is shown that under appropriate assumptions, the state error between plant system state and desired linear model state converges to zero as time increases. The results of numerical simulation and the experiment on the magnetic levitation system show the effectiveness of this approach.

Abstract: A class of shallow water waves equations are studied in this paper. Using Kato's existence theorem, we mainly study the initial and bounded value problem for the quasi-linear evolution equations. Meanwhile, we prove the existence of local and global existence of solutions to the equations.