A three-dimensional finite element model (FEM) of the L3-L4 motion segment using ABAQUS v 6.9 has been developed. The model took into account the material nonlinearities and is imposed different loading conditions. In this study, we validated the model by comparison of its predictions with several sets of experimental data. Disc deformation under compression and segmental rotational motions under moment loads for the normal disc model agreed well with the corresponding in vivo studies. By linking ABAQUS with MATLAB 2010.a, we determined the optimal Young s modulus as well as the Poisson's ratio for the artificial disc under different physiologic loading conditions. The results of the present study confirmed that a well-designed elastic arthroplastic disc preferably has an annulus modulus of 19.1 MPa and 1.24 MPa for nucleus section and Poisson ratio of 0.41 and 0.47 respectively. Elastic artificial disc with such properties can then achieve the goal of restoring the disc height and mechanical function of intact disc under different loading conditions and so can reduce low back pain which is mostly caused due to disc degeneration.
Diseases of lumbar spine and associated diseases of the intervertebral disc are a major focus of contemporary spinal care. Low back pain, in fact, is becoming in the recent years one of the most diffuse chronic pathologies. Ascribed to the prevalence of low back pain-mostly caused due to disc degeneration, and limitations of current treatments, arthroplasty has been propounded for replacing the degenerated disc. A three-dimensional finite element model (FEM) of the L3-L4 motion segment using ABAQUS v 6.9 has been developed. The annulus fibrosus of the model is idealized as an inhomogeneous composite of an isotropic ground substance, reinforced by helically oriented collagen fibers. The model took into account the material nonlinearities and is imposed different loading conditions. In this study, the model is validated by comparison of its predictions with several sets of experimental data. Disc deformation under compression and segmental rotational motions under moment loads for the normal disc model agreed well with the corresponding in vivo studies. We determined the optimal Young's modulus as well as the Poisson's ratio for the artificial disc under different physiologic loading conditions by linking ABAQUS with MATLAB 2010.a. The results of the present study suggest that a well-designed elastic arthroplastic disc preferably has an annulus modulus of 19.1 MPa and 1.24 MPa for nucleus section and Poisson ratio of 0.41 and 0.47 respectively. Elastic artificial disc with such properties can then achieve the goal of restoring the disc height and mechanical function of intact disc under different loading conditions and so can reduce low back pain.
Moment resisting frames (MRFs) are one of the most favorable systems, thanks to their appropriate performance and sufficient geometric flexibility. Despite these advantages, MRFs have limitations such as low stiffness and certain code limitations. This paper provides the experimental and numerical results of a novel dual lateral load resisting system. This dual system is proposed to combine the flexural and shear nonlinear behavior of MRFs with different lengths. In the proposed dual system, MRFs are combined with frames that have a shear link with a smaller cross-section at the mid-span. This combination transfers the first plastic hinges location from the beam ends of the MRFs to the mid-span of the shear link frames. Two 1/3-scale tests are performed in the strong floor lab, and the frames are tested under quasi-static cyclic loading. In addition to increasing the stiffness of the system, the novel dual system waives the code requirement to satisfy the constraint on the beam span-to-depth (span/depth) ratio. Furthermore, the new dual system improves the resilience of the system due to the substitutability of the shear link after an earthquake. Moreover, verified 3D finite element models of the moment resisting-shear link frames dual system are also used to demonstrate the performance of the new dual system.
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