Applied Mechanics and Materials Vols. 105-107

Abstract: The purpose of the present paper is to show that the problem of geometrically non linear free vibration of symmetrically and asymmetrically laminated composite beams with immovable ends can be reduced to that of isotropic homogeneous beams with effective bending stiffness and axial stiffness parameters. This simple formulation is developed using the governing axial equation of the beam in which the axial inertia and damping are ignored. The theoretical model is based on Hamilton’s principle and spectral analysis. Iterative form solutions are presented to calculate the fundamental nonlinear frequency parameters which are found to be in a good agreement with the published results. The non-dimensional curvatures associated to the fundamental mode are also given in the case of clamped-clamped symmetrically and asymmetrically laminated composite beams.

Abstract: Prestressing spiral groove tendon is a new sort prestressing tendon, its characteristic value of tensile yield strength fyk=1000MPa. Firstly, the yield strength, ultimate tensile strength, elastic modulus and elongation are all tested. According to 68 pullout tests, the bond-anchoring curves and failure modes have been studied, and the effects of concrete strength, diameter, anchoring length, thickness of concrete cover and stirrup ratio have been all analyzed. Finally, the equation for ultimate bond-anchoring strength has been suggested by statistical regression, and the test results are in good agreement with values of the suggested equation.

Abstract: Dynamic response is a key parameter for the engineering applications of MR damper. However, the response time has many different definitions, and which leads to a confusion of the measurement. Commonly, the response of MR damper in the new-designed status is focused, the instance after long-time use or standing-still has not been proposed. In this paper, the influence on the response time by the long-time standing-still is investigated, which shows that the response is largely lengthened. Next step, the measurement will be optimized, and the response of MR damper after long-time use will be in consideration.

Abstract: The giant magnetostrictive material (GMM) is a novel smart material based on magnetostrictive effect, and it is well suited to power ultrasonic transducer. Based on electromagnetic theory and vibration theory, the design and working principle of the magnetostrictive power ultrasonic transducer has been explained. This paper analyzed the dynamic characteristics of giant magnetostrictive materials under the outside magnetic field and deduced the wave equation of Terfenol-D rod, and the steady-state solution to the equation was obtained under given excitation. The speed and acceleration expressions of Terfenol-D were deduced by differentiating with respect to displacement equation. Based on developing mathematical models, computer imitation was made, and the result of modulation was analyzed from external conditions of transducer and inner structure of magnetostrictive material.

Abstract: Limit wind loads of a Concrete Filled Steel-Tube (CFST) transmission tower in a long-span tower-line system is computed. Firstly, fine Finite Element Method (FEM) model of the tower and its Multiple-Degrees-Of-Freedom (MDOF) model are built and the material nonlinear models including steel-tube and CFST are also modeled. Secondly, based on MDOF model, mean displacements under mean wind force are evaluated and the Root Mean Square Displacement (RMSD) under fluctuating wind force is also evaluated by random vibration theory. Then, Equivalent Static Wind Loads (ESWL) are computed considering the first three order modes. Finally, based on FEM model, the nodes are loaded by the ESWL and the nodal loads increase step by step in order to impel materials into plastic status until calculation can not converge. Plastic analysis shows the tower’s failure is caused by steel-tube element failure and the CFST elements have enough strength reserve. The tower’s three kinds of limit wind loads are computed based on different references and it is suggested to select the limit wind loads, whose corresponding wind velocity is 69.7m/s, as the design limit wind loads of the tower.

Abstract: The analytical solutions of shear flexible beams with displacement boundary conditions are derived by using the new sixth-order differential equation beam theory presented by Shi and Voyiadjis (ASME J. Appl. Mech., Vol. 78, 021019, 2011), in which the boundary layer effects are included. The accuracy of the boundary layer effects predicted by the new sixth-order beam theory is evaluated by the finite element analysis in this study. The numerical results show that the new sixth-order beam theory is capable of taking account of the displacement boundary conditions of shear deformable beams and predicting good results of the boundary layer effects induced by the displacement boundaries and the continuity constraints.

Abstract: In the structure design, the definition of the joints had a great impact on the structure internal force distribution, thus affecting the whole structure design. In the traditional design of steel structures, the beam-column joints were always considered as completely rigid connections or ideal hinged connections, but it is usually not in accord with the practical situations. According to the existing formulas, the simplified formulas for the end moments of semi-rigid connections have been proposed, the semi-rigid connections will also be discussed. The formulas proposed in this paper are applied to the auxiliary beam-column joint design, which is part of the counterforce frame design. It is hoped that the formulas can provide a reference for the steel frame design. Keywords: semi-rigid connections, end moments, internal forces distribution, steel frame design

Abstract: To study on the toughing effect of EPS in the plain concrete, the EPS concrete with 10%,20%,30%,40%,50% EPS volume fraction were prepared. Taking specific energy absorption as the index, the toughing effect of EPS concrete with different EPS volume fraction under impact loading were studied using a 100-mm-diameter split Hopkinson pressure bar(SHPB) apparatus, and the toughing effect mechanism of the concrete was discussed. The results show that the toughing effect of the EPS concrete increases with the average strain rate for the strain rate effect, which takes on obvious strain rate dependency. For the EPS microscopic structure effect, the toughing effect of the EPS concrete increases with the EPS volume fraction in 10~30%. Its toughing effect reduces somewhat when the EPS volume fraction reaches 40~50%. To improve the deformation property, the optimum volume fraction of EPS is 20%.

Abstract: According to Natural Bamboo Fiber/ Polypropylene fiber(PP) non-woven materials encountered the problem that its flame retardation is insufficient, this paper tried to add flame retardant to improve its performance, then the cone calorimeter was used to evaluate its flammability. The results show that Peak-Heat Release Rate and Smoke Release Rate etc significantly improved. In accordance with the UL94 ,the flame retardation meet the level V-0 , consistent with the requirements of enterprise.

Abstract: At present, the explosion isolator of the fuze safety system using stepping motor or based on the slider continuation move realized safe state restorability, but the former is restricted by the volume of stepping motor, however, the stepping motor is vulnerable to electromagnetic interference; the latter structure is complex, with several independent components, not compact and irreversible. In view of this, an action reversible mechanism based on piezoelectric actuator is proposed, realizing the fuze safety system reversibility. The principle of the piezoelectric actuator is described and the drive mechanism is designed. The feasibility is analysed. The study shows that the mechanism has the certain practical value for compact structure, small volume and reliable actuation.