• Structural Engineering and Mechanics
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• v.76 no.6
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• pp.687-708
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• 2020

Openings in steel plate shear walls (SPSWs) are usually used for decorative designs, crossing locations of multiple utilities and/or structural objectives. However, earlier studies showed that generating an opening in an SPSW has a negative effect on the cyclic performance of the SPSW. Therefore, this study proposes tripling or doubling the steel-sheet-plate (SSP) layer and stiffening the opening of the SPSW to provide a solution to undesirable opening effects, improve the SPSW performance and provide the infill option of potential strengthening measures after the construction stage. The study aims to investigate the impact of SSP doubling with a stiffened opening on the cyclic behaviour, expand the essential data required by structural designers and quantify the SPSW performance factors. Validated numerical models were adopted to identify the influence of the chosen parameters on the cyclic capacity, energy dissipation, ductility, seismic performance factors (SPF) and stiffness of the suggested method. A finite Element (FE) analysis was performed via Abaqus/CAE software on half-scale single-story models of SPSWs exposed to cyclic loading. The key parameters included the number of SSP layers, the opening size ratios corresponding to the net width of the SSP, and the opening shape. The findings showed that the proposed assembly method found a negligible influence in the shear capacity with opening sizes of 10, 15, 20%. However, a deterioration in the wall strength was observed for openings with sizes of 25% and 30%. The circular opening is preferable compared with the square opening. Moreover, for all the models, the average value of the obtained ductility did not show substantial changes and the ultimate shear resistance was achieved after reaching a drift ratio of 4.36%. Additionally, the equivalent sectional area of the SSP in the twin and triple configuration of the SPSWs demonstrated approximately similar results. Compared with the single SSP layer, the proposed configuration of the twin SSP layer with a stiffened opening suggest to more sufficiency create SSP openings in the SPSW compared to that of other configurations. Finally, a tabular SPF quantification is exhibited for SPSWs with openings.

• Earthquakes and Structures
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• v.10 no.5
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• pp.1143-1179
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• 2016

Offshore wind turbines are considered as a fundamental part to develop substantial, alternative energy sources. In this highly flexible structures, monopiles are usually used as support foundations. Since the monopiles are large diameter (3.5 to 7 m) deep foundations, they result in extremely stiff short monopiles where the slenderness (length to diameter) may range between 5 and 10. Consequently, their elastic deformation patterns under lateral loading differ from those of small diameter monopiles usually employed for supporting structures in offshore oil and gas industry. For this reason, design recommendations (API and DNV) are not appropriate for designing foundations for offshore wind turbine structures as they have been established on the basis of full-scale load tests on long, slender and flexible piles. Furthermore, as these facilities are very sensitive to rotations and dynamic changes in the soil-pile system, the accurate prediction of monopile head displacement and rotation constitutes a design criterion of paramount importance. In this paper, the Fourier Series Aided Finite Element Method (FSAFEM) is employed for the determination of static impedance functions of monopiles for OWT subjected to horizontal force and/or to an overturning moment, where a non-homogeneous soil profile has been considered. On the basis of an extensive parametric study, and in order to address the problem of head stiffness of short monopiles, approximate analytical formulae are obtained for lateral stiffness $K_L$, rotational stiffness $K_R$ and cross coupling stiffness $K_{LR}$ for both rough and smooth interfaces. Theses expressions which depend only on the values of the monopile slenderness $L/D_p$ rather than the relative soil/monopile rigidity $E_p/E_s$ usually found in the offshore platforms designing codes (DNV code for example) have been incorporated in the expressions of the OWT natural frequency of four wind farm sites. Excellent agreement has been found between the computed and the measured natural frequencies.

• Journal of Biomedical Engineering Research
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• v.25 no.3
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• pp.171-182
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• 2004

This study investigates the biomechanical efficacies of vertebroplasty which is used to treat vertebral body fracture with bone cement augmentation for osteoporotic patients using image and finite element analysis. Simulated models were divided into two groups: (a) a vertebral body, (b) a functional spinal unit(FSU). For a vertebral body model, the maximum axial displacement was investigated under axial compression to evaluate the effect of structural integrity. The stiffness of each FE model simulated was normalized by the stiffness of intact model. In the case of FSU model, 3 types of compression fractures were formulated to assess the influence on spinal curvature changes. The FSU models were loaded under compressive pressure to calculate the change of spinal curvature. The results according to the various factors suggest that vertebroplasty has the biomechanical efficacy of the increment of structural reinforcement in a patient who has relatively high level of BMD and a patient with the amount of 15％, PMMA injection of the cancellous bone volume. The spinal curvatures after compression fracture simulation vary from 9$^{\circ}$ to 17$^{\circ}$ of kyphosis compared to that the spinal curvature of normal model was -2.8$^{\circ}$ of lordosis. These spinal curvature changes cause the severe spinal deformity under the same loading. As the degree of compressive fracture increases the spinal deformity also increases. The results indicate that vertebroplasty has the increasing effect of the structural integrity regardless of the amount of PMMA or BMD and the restoration of decreased vertebral body height may be an important factor when the compressive fracture caused the significant height loss of vertebral body.