Torsional stability of thin-walled cylindrical shells filled with free-flowing aggregate

Экспериментами изучено влияние сыпучего заполнителя на устойчивость при кручении тонкостенных цилиндрических оболочек. Для исследования образцы изготавливались из алюминиевого сплава 3004 глубокой вытяжкой в матрице. Образцы закреплялись консольно к жесткой стенке, на свободный конец прикладывался крутящий момент. Испытывались пустые и заполненные железным порошком образцы. Нагружение образцов выполнялось ступенчато, порциями по 10Н вначале и при приближении к моменту потери устойчивости по 1Н, 0,5Н. На каждой ступени нагружения фиксировались крутящий момент и угол поворота свободного конца образца. Построены графики зависимости угла поворота от крутящего момента. Устойчивость образцов терялась в упругости. Вначале нагружения, на заполненных сыпучим заполнителем образцах, не происходит поворот сечений из-за препятствия сил трения заполнителя. Железный порошок увеличивает значение критического крутящего момента на 20-30%. Experiments have studied the effect of free-flowing aggregate on torsional stability of thin-walled cylindrical shells. For research samples were made of aluminum alloy 3004 deep hood in the matrix. The samples were fixed cantilever to a rigid wall, on torque was applied to the free end. Tested empty and samples filled with iron powder. The loading of the samples was carried out stepwise, in portions of 10N at the beginning and when approaching the moment of loss stability of 1H, 0.5H. At each loading stage, torque and angle of rotation of the free end of the sample. Graphs built the dependence of the angle of rotation on the torque. Stability of samples lost in elasticity. At the beginning of loading, on filled with bulk filler in samples, no rotation of sections occurs due to obstacle forces friction of the aggregate. Iron powder increases the critical value of torque by 20-30 %.

Nonlocal Analysis of the Flexural–Torsional Stability for FG Tapered Thin-Walled Beam-Columns

This paper addresses the flexural–torsional stability of functionally graded (FG) nonlocal thin-walled beam-columns with a tapered I-section. The material composition is assumed to vary continuously in the longitudinal direction based on a power-law distribution. Possible small-scale effects are included within the formulation according to the Eringen nonlocal elasticity assumptions. The stability equations of the problem and the associated boundary conditions are derived based on the Vlasov thin-walled beam theory and energy method, accounting for the coupled interaction between axial and bending forces. The coupled equilibrium equations are solved numerically by means of the differential quadrature method (DQM) to determine the flexural–torsional buckling loads associated to the selected structural system. A parametric study is performed to check for the influence of some meaningful input parameters, such as the power-law index, the nonlocal parameter, the axial load eccentricity, the mode number and the tapering ratio, on the flexural–torsional buckling load of tapered thin-walled FG nanobeam-columns, whose results could be used as valid benchmarks for further computational validations of similar nanosystems.

Simplified Method of Determining Torsional Stability of the Multi-Storey Reinforced Concrete Buildings

This article proposes a simplified method for determining the elastic radius ratio of the multi-storey reinforced concrete building. The elastic radius ratio is the benchmark parameter of the buildings in determining torsional stability during an earthquake. When buildings are torsionally flexible, the torsional component of seismic response amplifies the overall response of the building. Because of the numbers of simplified assumptions such as the adoption of the single-storey model, much of the published articles have a very limited range of application. Quantifying the interaction of different forces in multi-story non-proportional buildings has been the main challenge of these studies. The proposed “shear and bending combination method” solves this by introducing parameters that can determine the relative influence of individual actions. Moreover, the proposed method applies to buildings with all type of structural systems, having asymmetry, and accidental eccentricity. The method is validated through a parametric study consisting of eighty-one building models and using computer analysis. The proposed method and the research findings of this study are useful in determining the torsional stability of the building, in verifying the results of the computer-based analysis, and in optimizing the structural system in the buildings.

Stability of Thin Web Composite Cantilever Beams of Random Lamination

This study addresses the analytical treatment of a closed-form buckling equation for lateral-torsional stability of thin web composite cantilever beams under mid-height tip force. The beam is composed of random ply fiber orientations. Classical lamination theory is embedded into the Vlasov plate formulation to make up the framework of the analytical treatment. A closed-form solution is realized when an innovative dimensional reduction is extended to the 3D constitutive stiffness matrix. This was made possible through a two-step process in which the shear strain, lateral curvature, and twisting curvature are retained first. By condensing the shear strain variable, effective lateral, torsional, and coupling stiffness terms were formulated. Applying the equilibrium conditions in the deformed configuration, two differential equations are obtained in terms of the lateral curvature and twisting angle. Eliminating the lateral curvature, the twisting angle differential equation with nonconstant coefficients is generated. This equation is solved using a hybrid numerical-analytical approach yielding an analytical buckling expression. Finite element results are generated to verify the accuracy of the buckling load predictions indicating very good correlation with the buckling equation results regardless of the random lamination applied.

Comparison of Short Stems Versus Straight Hip Stems: A Biomechanical Analysis of the Primary Torsional Stability

Cementless straight stems show very good survival rates. However, the more distal force application of straight stems may lead to release-related proximal stress-shielding. Nevertheless, this technical brief had the objective of conducting a biomechanical in vitro analysis comparing short stems with established straight stems with respect to their primary torsional stability. Two cementless short hip stems and three cementless straight hip stems were implanted in n = 5 synthetic femora each. Torsional torques were applied into the hip stems at a continuous interval of ±7 Nm. Micromotions were measured by six inductive extensometers on four different measurement levels. At the proximal measuring point, significantly smaller relative micromotions of the CLS® prosthesis could be detected compared to all other stem models (p < 0.05). In all stem models, smallest relative micromotions were found at the metaphyseal/diaphyseal measuring point. Only at the measuring point of the distal tips of the straight stems, statistically significantly lower relative micromotion of the CLS® stem compared to the Trendhip® stem could be found (p < 0.01). All the investigated stems generally display a rather comparable anchoring pattern and an almost physiological force application. Since the comparatively long straight stems present an anchoring pattern nearly identical to that of the examined short stems, a shortening of the established straight stems could be taken into consideration. This would offer the advantage of minimally invasive surgery and bone-saving resection as well as preservation of cancellous bone in case a revision would become necessary.

TORSIONAL SHEAR STRENGTH PROPERTIES OF MALAYSIAN TROPICAL TIMBER IN STRUCTURAL SIZE

The shear strength of timber joists in timber design is important, especially to provide an adequate torsional stability and to avoid vibrational serviceability problems. In Malaysia, the data of shear strength of timber is available in MS544 Part 2. The data were developed by shear block test with small samples without defect known as small clear samples. Torsion test is one of the other approaches that can be used to attain the state of pure shear as it does produce a purer and a clearer shear stress distribution in the specimen, allowing measurement of the pure shear properties. However, in Malaysia, very little attention has been paid to the use of the torsion test in evaluating shear strength. Therefore, this study aims to investigate the torsional shear strength of selected Malaysian tropical timbers of different strength groupings (SG) namely Balau (SG1), Kempas (SG2), Kelat (SG3), Kapur (SG4), Resak (SG4), Keruing (SG5), Mengkulang (SG5), Light Red Meranti (SG6), and Geronggang (SG 7) using structural size timbers in accordance with BS:EN 408 and then compared with published by MS554: Part 2. The result shows contradictions of strength grouping between findings and published by MS554: Part 2. Resak (SG4) and Mengkulang (SG5) grade stress value have risen towards SG 3. Geronggang is currently in the SG6. Also from the findings, Kelat (SG3), Kapur (SG4) and Keruing (SG5) grade stresses are at par towards each other, even though they are completely in the different strength group as stated in MS544: Part 2. In conclusion, shear strength data need to be re-examined, since the strength for the tested specimen is much higher than the data given in MS 544 Part 2. This will lead to the increment in section and wastage in cost.