Free vibration analyses of lattice sandwich beams with general elastic supports have rarely been discussed in this field’s literature. In this paper, a unified method is proposed to study the free vibration characteristics of lattice sandwich beams under various boundary conditions. The proposed method is to convert the three truss cores of lattice sandwich beams into an equivalent homogeneous layer and introduce two different types of constraint springs to simulate the general elastic support boundary at both ends of lattice sandwich beams. By changing the rigidity of the boundary restraint spring, various boundary conditions can be easily obtained without modifying the solving algorithm and solving process. In order to overcome all the discontinuities or jumps associated with the elastic boundary support conditions, the displacement function of lattice sandwich beams is usually obtained as an improved Fourier cosine series along with four sine terms. On this basis, the unknown series coefficients of the displacement function are treated as the generalized coordinates and solved using the Rayleigh–Ritz method. The correctness of the present method is verified through comparison with existing literature. The calculation results of the present method are highly accurate, indicating that the present method is suitable for analyzing the vibration characteristics of lattice sandwich beams with general elastic supports. In addition, the effects of beam length, panel thickness, core height, radius and truss inclination on the natural frequencies of lattice sandwich beams with arbitrary boundary conditions have been discussed in this paper.

Chen, H.; Liu, H.; Ge, H.; Kong, F.; Han, Z., and Yu, D., 2020. Mechanics characteristics of chamber and slide system of vertical slide marine emergency evacuation system. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 311–317. Coconut Creek (Florida), ISSN 0749-0208.In this paper, the evacuation process of the vertical slide Marine emergency evacuation system and the force under different states of the system are analyzed and explored. The overall scheme of Marine emergency evacuation system with vertical slide is established. The movement of escaping personnel falling in the chute system is deeply analyzed. The slide system is divided into a network-man model and a load-bearing steel cable model. On this basis, the steel-flexible body contact model (that is, the “ball-net” collision model) and the single-side fixed series multi-degree-of-freedom vibration model are established. And the mathematical exploration and simulation analysis. In the process of analysis, the falling speed, falling angle and boundary conditions of simulation analysis were determined one by one, and the analysis result was the load output of the top of the load-bearing steel cable. The simulation results are in line with the expected estimation. After optimizing the results of the slide dynamic analysis, the dynamic response of the space steel frame is analyzed as the input condition of the dynamic analysis of the space steel frame, and the results meet the expected requirements.

This paper mainly describes the influence factors of the captured energy power by huge wave energy harvesters, in which the vertical motion of buoy can transform ocean’s potential energy into piezoelectric energy power by undulating waves. Firstly, related environmental coefficients are analyzed by means of the incident wave theory. Besides, the geometric structural parameters are also analyzed and compared under optimal environmental coefficients with semi-analytical solutions. Thirdly, the numerical results also show the impact trend of hydrodynamic parameters and geometric volume on motion, voltage and power with qualitative agreement. The numerical simulation confirms that the improved structure parameters could markedly deliver sufficient power under the same conditions with long-time stability.

Liu, H.; Zheng, X.; Zhang, W.; Chen, H.; Kong, F.; Liu, M., and Shu, G., 2019. Multiple freedom interacted influence on the power conversion for mushroom wave energy converter. In: Hoang, A.T. and Aqeel Ashraf, M. (eds.), Research, Monitoring, and Engineering of Coastal, Port, and Marine Systems. Journal of Coastal Research, Special Issue No. 97, pp. 55–70.Nowadays, the design of wave energy converter (WEC) has become a research hotspot of new energy development and utilization. The motion form of traditional WEC is usually in the single degree of freedom model. In order to efficiently utilize wave energy, a multi-degree-of-freedom interactive wave energy converter, namely Mushroom WEC, is proposed in this paper. The device is mainly composed of a spar hinged to the bottom of the sea for pitch motion and a buoy tied to the spar for heave motion along the direction of the spar, which can absorb the potential energy and kinetic energy of the wave at the same time. In this paper, a mathematical motion model is established according to the motion characteristics of the device, and an analytical method based on linear wave theory is used to solve the wave excitation force and hydrodynamic coefficient. Moreover, by introducing two independent PTO systems and using numerical methods to solve the coupled nonlinear equations of motion, the coupled motion effect and power generation performance of Mushroom WEC spar and buoy were analyzed. The result showed that the power generation efficiency of Mushroom WEC is better than that of the traditional single-degree-of-freedom wave energy converter, and the frequency response range of the device can be improved. The research in this paper is of referential significance to the research of wave energy converter moving with multiple degrees of freedom.