Dong Shi-lin

A Study on Space Masts Based on Octahedral Truss Family

Octahedral truss is a kind of geometry-rich structure, which can be used extensively in space missions. Regular octahedron is the basis of other various octahedral trusses. Firstly, five basic units of octahedral truss or derivatives are proposed, and the structural performances are investigated briefly. Mechanism features and formations are then studied for fundamental deployable modules in conjunction with the basic units. And knowledge of geometry is formulated in detail for different deployable modules, especially for variable geometry truss and tensegrity. The corresponding mast formations are also developed. Finally, kinematic analysis approach is proposed concisely for statically determinate deployable octahedral truss, and spares matrix storage and reduced matrix technique are employed to improve the computation efficiency.

A New Catenary Cable Element

In this paper, a new explicit analytical solution of a single cable with two fixed points was presented by considering the equilibrium and geometric conditions of the cable mini-element. Combining the analytic solution and virtual work principle, the authors proposed a new two-node catenary cable element. By comparing the stiffness matrix of the new cable element and the two-node straight-line cable element, a simplified matrix form was presented and a nonlinear analysis procedure considering the influence of cable initial sag and force was given. This cable element has the advantage of high computing precision and simple expression compared with multi-node cable element and other cable elements. Two numerical examples illustrated the accuracy and reliability of the nonlinear element presented in this paper.

A New Design Conception for Large Span Deployable Flat Grid Structures

The deployable flat grids, consisting of only hinged pantographic units, usually have low structural stiffness, and the bending moment constitutes a great part of internal forces. This results in structural inefficiency, especially for large span grids. Diagonals (web struts) and lower chords are added herein to enhance the structural stiffness. The newly added web struts must be compatible with the deployable geometry. Cables or foldable bars can be used as lower chords. The statical determinacy characteristics are analysed for the newly proposed grid system. On the basis of this concept, several flat grids are firstly developed for potential applications. And a joint conception also developed. The structural performances are investigated for a series of deployable flat grids. Steel quantities and deflections are compared for four different grids. The results indicate that the newly proposed conception has fairly high economic scale, structural efficiency and promising potential application field.

Initial pre-stress finding procedure and structural performance research for Levy cable dome based on linear adjustment theory *

The cable-strut structural system is statically and kinematically indeterminate. The initial pre-stress is a key factor for determining the shape and load carrying capacity. A new numerical algorithm is presented herein for the initial pre-stress finding procedure of complete cable-strut assembly. This method is based on the linear adjustment theory and does not take into account the material behavior. By using this method, the initial pre-stress of the multi self-stress modes can be found easily and the calculation process is simplified and efficient also. Finally, the initial pre-stress and structural performances of a particular Levy cable dome are analyzed comprehensively. The algorithm has proven to be efficient and correct, and the numerical results are valuable for practical design of Levy cable dome.

A New Frequency Domain Method for Wind Response Analysis of Spatial Lattice Structures with Mode Compensation

The large span spatial lattice structures have many natural frequencies in a narrow frequency range, the conventional frequency domain method is difficult to contain all significant contribution modes. Through numerical examples, it is found that some high order modes are likely to be overlooked because of their higher positions of modal order, in spite of their significance to wind response. According to the contributions of modes to strain energy of system, the paper presented an efficient method to compensate the errors owing to missing out some significant high order modes. The effectiveness of the proposed method is verified through a numerical analysis of the wind responses of a spherical dome. At last, a simplified method of wind vibration coefficient is present for design of practical projects.

Neural network method for solving elastoplastic finite element problems

A basic optimization principle of Artificial Neural Network—the Lagrange Programming Neural Network (LPNN) model for solving elastoplastic finite element problems is presented. The nonlinear problems of mechanics are represented as a neural network based optimization problem by adopting the nonlinear function as nerve cell transfer function. Finally, two simple elastoplastic problems are numerically simulated. LPNN optimization results for elastoplastic problem are found to be comparable to traditional Hopfield neural network optimization model.

Manufacture Error and its Effects on the Initial Pre-Stress of the Geiger Cable Domes

The model of Type-I Extreme Value Distribution (also named Gumbel Distribution) is firstly proposed for the analytical model of the manufacture errors of the cable length which are according to the average error of the cable manufacture industry specifications. The analysis procedure of the manufacture errors are formulated subsequently. At the same time, the effects of the effective sectional area and elastic module (herein using the multiplication of the cable stiffness EA) of the cables are also taken into account. Under the background of the Blue Sea cable dome, the structural forms of the geometry are compared and investigated for three types of cable domes, the Blue Sea cable dome, the classical cable dome and the rib-hoop cable dome, respectively. Next, the effects on the initial pre-stress of three cable domes from the manufacture errors of the cables which include different kinds of cables and any one of the cables are mainly evaluated thoroughly. The effects on the structural performances of three cable domes can be found through analysis and the cables which are sensitive to the manufacture errors are also found. The works can provide valuable guideline to the manufacture and installation of the cable dome.