Papers by Keyword: Torsional Stiffness

Abstract: The paper discusses the principles of precast concrete hollow-core slabs taking into account their spatial work. It is shown that consideration of spatial work makes it possible to determine the forces in individual floor slabs significantly more precise. The fact that strain redistribution between precast floor slabs depends on slabs’ bending and torsional stiffness is shown. The research has been mostly devoted to determination of the bending stiffness with regard to formation of cracks and the change in torsional stiffness, especially considering the presence of normal cracks, which is still unstudied. This paper presents the technique for determining the torsional stiffness of hollow-core slabs with normal cracks. In order to determine the components included in the resolving system of equations, it is proposed to use an approximation method based on the processing of numerical data using spatial finite elements.

Abstract: With the development of transportation, more and more long-span floating system steel truss-stiffened cable-stayed bridges have been built. Due to the non-restraint in longitudinal direction, this kind of bridges possess very superior performance in the dissipation of vibration energy. On account of the characteristics above, the paper intends to discuss the dynamic behavior of this type of bridges. Based on a real structure design, the numerical simulation procedure of the vibration has been introduced. According to a series of assumptions, the dynamic 3D FEM model of the bridge is established firstly. Thereafter, the vibration characteristics of the model are evaluated. Results show that the longitudinal stiffness is relatively small in comparison to the torsional stiffness. The 1st order mode is longitudinal floatation of girders and pylons. But overall the bridge is still rather flexible.

Abstract: This article deals with the mathematical description and numerical implementation of the free warping problem. The solution of the warping problem is given by a warping function obtained by solving the Laplace equation with a corresponding boundary condition. An analytical solution is available only for a limited number of specific cross-sectional shapes such as ellipse or rectangle. For the solution of a general cross section, the Laplace equation must be solved numerically by the finite element method. From a mathematical point of view, the free warping problem can be described in the same way as the heat transfer phenomena, but in the numerical implementation, there are several features specific to warping analysis.The solution algorithm has been implemented in the OOFEM open-source finite element code [1] and verification has been done on several examples with known analytical solutions.

Abstract: The iterative formulas of spring forces for Circumferential Arc Spring Dual Mass Flywheel (DMF-CS) were derived by discrete method, involving friction forces. The computation program was designed, and the curves illustrating transmitted torques over deformation angles of the outer and inner arc springs were plotted, which showed linear torque behavior. Thus two stages of torsional stiffness of DMF-CS were figured out to be 465.9923Nm/rad and 631.7980Nm/rad. The two stages of torsional stiffness without friction forces were calculated by this method, which were 434.6408Nm/rad and 591.3652Nm/rad. The experiment of static torque characteristic of DMF-CS was completed, obtaining the experimental torsional stiffness, which were 455.9923Nm/rad and 620.9412Nm/rad. Comparing the above values of torsional stiffness, the values with friction forces show more precise than ones without friction forces, and the values without friction forces are smallest. The results show that the friction forces contribute to the torsional stiffness of DMF-CS.

Abstract: In galloping, reverse split wire plays an important role in. Through the study of split change sub conductor length of wire twisting motion estimation, the wire tension change caused by the torsion of sub conductors; besides considering some of the split wire torsion stiffness of the external factors, but also the influence of torsion wire tension change, caused by the conductor sag, line height worse, we deduced the general formula to calculate the new conductor spacer system torsional stiffness.

Abstract: The objective of this paper is to design, analyze, and test the space frame for electric vehicle with comparison to the engine type. Therefore, in order to design the electric vehicle formula, the same requirements with some changes are considered. The space frame is designed to suit with the electric vehicle and then finite element analysis is used to determine the torsional stiffness of the frame which is verified by the torsional test. Initially, the required torsional stiffness for the electric car is 1350 Nm/deg and the mass is set to be not more than 40 kg. The numerical results and the experimental results for torsional stiffness are 960 Nm/deg and 1218 Nm/deg, respectively. Therefore, the torsional stiffness is about 25% under-predicted; anyway it can be used to predict the torsional stiffness of the frame. Due to some changes must be performed, therefore the modified frame is re-analyzed with the torsional stiffness of 1389 Nm/deg which is less than the revised required car’s torsional stiffness of 1404 Nm/deg. Anyway, the torsional stiffness of frame with battery’s case can meet the requirement. The mass of the modified frame is 50 kg which is larger than required mass due to selected sizes of steel tubes. In conclusion, the space frame can be designed and the mass can be improved further by reducing the sizes.

Abstract: The design of semi-monocoque frame by using the composite-steel joint is considered in this paper. The frame is designed with weight less than 30kg and torsional stiffness more than 1200 Nm/deg. In order to design the semi-monocoque frame, the analysis of the composite-steel joint has to be clearly investigated. Therefore, the stress analysis of composite-steel joint is performed and then the frame is designed. The double lab joint with two holes is tested and verified by the experiments. The carbon-fiber fabric laminated with the KEVLAR fabric composite laminate is used for composite part. From experiments, the joint’s strength can be increased by using the eccentric holes. Therefore, in order to meet the requirement of the SAE rules; load capacity more than 30 kN, the eccentric hole double lap joint is numerically designed and applied to semi-monocoque frame. The joint has strength of 32 kN and can be used in frame design. The semi-monocoque frame is designed and analyzed by finite element analysis. The maximum stress at maximum load is 208 MPa which is less than the yield strength of the materials so it can withstand the loads, the mass is 29.6kg, and the torsional stiffness of the frame is 1408 Nm/degree. Therefore, the semi-monocoque frame can be successfully designed.

Abstract: The torsional stiffness is one of the most important properties of chassis that significantly affect its dynamic characteristics such as handling and rollover. The torsional stiffness is desired to be as high as possible since low torsional stiffness may cause resonance or vibration. There are several types of heavy duty truck chassis that used in Malaysia and no information about the torsional stiffness magnitude of it. In this work, the torsional stiffness of several existing types of heavy duty truck chassis and some modified types, namely: arc model, block model, hole model, multi holes model and fully block model are determined using finite element method. The torsional stiffness of several chassis was compared together with the weight comparison in order to get the best design of chassis that has high torsional stiffness and low weight. Based on the simulation result, the multi holes model is the best design due to the highest of torsional stiffness and the lowest mass.

Abstract: In galloping of transmission lines, the twist of bundled conductors plays an important role. So the research of torsional stiffness of conductors-spacers for in-depth study of the galloping of the transmission lines is important.In addition to considering the impact of previous studies involving some of the torsional stiffness of bundled conductors factors (such as the torsional stiffness of sub conductor, the actual tension, etc.), but also the effects of sag and line height difference are considered. Finally a theoretical torsional stiffness of conductors-spacers formula is deduced. With the previous formula and the measured data on the different conductor types, different sub conductor spacing and different initial tension conditions, theresults of this formula are closer to the measured data.

Abstract: Stress of the cylindrical helical torsion spring is researched with finite element method when torsional degree changes. For spring has great resilience, large deformation effect is considered in the simulations. Analysis on the stiffness shows that the model built is credible, although torsional stiffness is not constant for large torsional angle, the strength is enough whose variation trend is consistent with the spring stiffness with different working torsional angle.