Single-layer Lattice Research Articles

Simulation Study of the Whole Process of Collapse and Collision of a Large-Span Steel Single-Layer Lattice Structure

The project Expo Axis is one of the landmark buildings of Expo Shanghai 2010, and its structural safety depends largely on the security of the six Sun Valleys, which are the important components of the Expo Axis. The simulation of the whole process of collapse and collision of the sun valley under earthquake action is conducted in this article. In the calculation multiple nonlinear factors are taken into account, such as material nonlinearity, large displacement effect, self-contact collision among the structure members, contact collision between the structure and the ground, etc. Through analyzing the results, a reasonable assessment of the structure of Sun Valley’s performance under the supper-large earthquake is given out. This method can also offer reference to other similar large-span steel single-layer lattice structure’s performance analysis.

Analysis of Nonlinear Behavior and Feasibility for A New Type of Two-Way Single Layer Lattice Dome with Nodal Eccentricity using T -Joint Struts

Analysis of Nonlinear Behavior and Feasibility for A New Type of Two-Way Single Layer Lattice Dome with Nodal Eccentricity using T -Joint Struts

SHAPE AND SECTION OPTIMIZATION FOR FREE-FORM STEEL STRUCTURES CONSIDERING CONNECTION COST

A shape and section optimization method is presented for free-form steel structures considering cost of connections. Two types of rigid connections are considered. One is a conventional full-strength connection, and the other is a partial-strength connection using for example fiber reinforced mortar. The inherently different costs of the two are made continuous by introducing a cost increase function of the latter. A nest-structure optimization, consisting of a shape and section optimization as the main problem and cost minimization of each connection as the sub-problem, is proposed to minimize the total cost of members and connections. Examples of a single-layer lattice roof are shown to demonstrate the effectiveness of the proposed method.

Study on Stability of a New Prestressed SINGLE-Layar Spherical Lattice Shell

Prestressing of lattice shell is realized by cable, and author put forward a new kind of layout: The prestressing has been brought to bear by hoop and radial element of single-layer lattice shell, which avoid cable's effect on architectural purpose. The element has been made to sleeve, and the magnitude of prestressing is dominated by bolt. Article shows an example of K6, K8 single-layer spherical lattice shell, and the prestressing have been exert on partial ribs and hoops. The prestressing has been calculated by element axial force under normal loading. Stability of shells have been studied, and show the deformation satisfy the criteria under normal loading; The ultimate capacity has been improved obviously, loads transfer is rational. The new layout of prestressing is a promising technique.

Dynamic Buckling Behavior of Rigidly Jointed Single Layer Lattice Domes under Vertical and Horizontal Step Wave

Dynamic Buckling Behavior of Rigidly Jointed Single Layer Lattice Domes under Vertical and Horizontal Step Wave

Seismic isolation analysis of FPS bearings in spatial lattice shell structures

A theoretical model of a friction pendulum system (FPS) is introduced to examine its application for the seismic isolation of spatial lattice shell structures. An equation of motion of the lattice shell with FPS bearings is developed. Then, seismic isolation studies are performed for both double-layer and single-layer lattice shell structures under different seismic input and design parameters of the FPS. The influence of frictional coefficients and radius of the FPS on seismic performance are discussed. Based on the study, some suggestions for seismic isolation design of lattice shells with FPS bearings are given and conclusions are made which could be helpful in the application of FPS.

A STUDY ON BUCKLING LOAD OF LATTICE DOMES OF TWO-WAY

The present paper proposes an efficient method for evaluating the elasto-plastic buckling loads of two-way single layer lattice domes under vertical loads. The connections are assumed semi-rigid as formed with screwed bolt-to-ball joints. The procedure of the method is composed of the following steps: linear buckling analysis to find the generalized slenderness ratio of the specific member that is the most relevant to their loading capacities; the generalized slenderness ratio is applied to obtain the axial strength for the specific member, based on which the elasto-plastic buckling load is evaluated. The comparison of the evaluated buckling loads with those obtained from FEM elasto-plastic buckling analyses proves that the procedure is valid and efficient enough to be applied in design practice. Based on safety factors, given in some recommendations, the allowable column strength is also proposed for proportioning the members of the single layer lattice domes.

Study on dynamic behavior of a new type of two-way single layer lattice dome with nodal eccentricity

This paper discusses a feasibility of a new type of two-way system for single layer lattice domes with nodal eccentricity by investigating the dynamic behavior under earthquake motions. The proposed dome is composed of two main arches, intersecting each other with T-joint struts to provide space for tensioning membranes. The main purposes of this study are to calculate the nonlinear dynamic response under severe earthquake motions and to see the possibility of using this new type of two-way system for single layer lattice domes against earthquake motions. The results show that the main arches remain elastic except yielding of the joints of strut members that can be used to absorb some amount of strain energy at strong earthquake motion. Consequently, deformation of the main arches can be reduced and any heavy damages on the main arches can be minimized. A kind of damage-control characteristic appeared in this system may be utilized against severe earthquake motions, showing a possibility of designing a new type of single layer lattice dome.

Optimum topological design of geometrically nonlinear single layer latticed domes using coupled genetic algorithm

Single layer latticed domes are lightweight and elegant structures that provide cost-effective solutions to cover the large areas without intermediate supports. The topological design of these structures present difficulty due to the fact that the number of joints and members as well as the height of the dome keeps on changing during the design process. This makes it necessary to automate the numbering of joints and members and the computation of the coordinates of joints in the dome. On the other hand the total number of joints and members in a dome is function of the total number of rings exist in the dome. Currently no study is available that covers the topological design of dome structures that give the optimum number of rings, the optimum height of crown and the tubular cross-sectional designations for the dome members under the given general external loading. The algorithm presented in this study carries out the optimum topological design of single layer lattice domes. The serviceability and strength requirements are considered in the design problem as specified in BS5950. The algorithm takes into account the nonlinear response of the dome due to effect of axial forces on the flexural stiffness of members. The optimum solution of the design problem is obtained using coupled genetic algorithm. Having the total number of rings and the height of crown as design variables provides the possibility of having a dome with different topology for each individual in the population. It is shown in the design example considered that the optimum number of joints, members and the optimum height of a geodesic dome under a given external loading can be determined without designer’s interference.

Analysis based evaluation for buckling loads of two-way elliptic paraboloidal single layer lattice domes

The present paper proposes an efficient method for evaluating elasto-plastic buckling loads of two-way elliptic paraboloidal lattice domes of single layer under vertical loads. The procedure is composed of the following steps: linear buckling analysis to find the generalized slenderness ratio of the specific member that is the most relevant to their loading capacities; the generalized slenderness ratio is applied to obtain the axial strength for the specific member, based on which elasto-plastic buckling load is evaluated. The comparison of the evaluated buckling loads with those obtained from FEM elasto-plastic buckling analyses proves that the procedure is valid and efficient enough to be applied in design practice. Based on safety factors, given in some recommendations, the allowable column strength is also proposed for proportioning the members of elliptic single layer paraboloidal lattice domes.

Structural damage detection with wavelet support vector machine: introduction and applications

Based on wavelet packet decomposition and conditions of the support vector kernel function, a non-linear wavelet basis is introduced to construct the kernel function of support vector machine (SVM), and a tighten wavelet support vector machine (WSVM), which has strong generalization ability is obtained. Wavelet packet decomposition is applied to the structural response signals under ambient vibration, feature vectors are obtained by feature extraction according to wavelet energy spectrum. The feature vectors are used for training and classification as the inputs of the tighten SVM. Hence, a new structural damage detection method called complete WSVM is established. This method is used to a single-layer spherical lattice dome for damage detection. The structural damage location and degree can be detected and classified, and the result is highly accurate. This approach has some advantages, such as engineering oriented, low cost and convenient. Copyright © 2005 John Wiley & Sons, Ltd.

Nonlinear dynamical bifurcation and chaotic motion of shallow conical lattice shell

The nonlinear dynamical equations of axle symmetry are established by the method of quasi-shells for three-dimensional shallow conical single-layer lattice shells. The compatible equations are given in geometrical nonlinear range. A nonlinear differential equation containing the second and the third order nonlinear items is derived under the boundary conditions of fixed and clamped edges by the method of Galerkin. The problem of bifurcation is discussed by solving the Floquet exponent. In order to study chaotic motion, the equations of free oscillation of a kind of nonlinear dynamics system are solved. Then an exact solution to nonlinear free oscillation of the shallow conical single-layer lattice shell is found as well. The critical conditions of chaotic motion are obtained by solving Melnikov functions, some phase planes are drawn by using digital simulation proving the existence of chaotic motion.

Dynamic characteristics of single-layer cylindrical lattice shells

This investigation is concerned with the free vibration and seismic response of single-layer cylindrical lattice shells. The effects of basic structural parameters such as the ratio of rise to span, mass, damping, the ratio of length to span and the rigidity of supports, on the dynamic behaviour of single-layer cylindrical lattice shells are investigated in detail. In this paper the finite-element method is used, in which three-dimensional beam elements are employed. Both the natural frequencies and their associated modes of vibration are obtained with a subspace iteration technique, and the direct dynamic analysis method is adopted to analyse the dynamic responses of single-layer lattice shells under vertical and horizontal earthquake excitations. The objective of this study is to achieve a better understanding of the dynamic characteristics and seismic behaviour of single-layer lattice shells. The results are valuable for the earthquake-resistant design of such structures.

Dynamic characteristics of single-layer cylindrical lattice shells

This investigation is concerned with the free vibration and seismic response of single-layer cylindrical lattice shells. The effects of basic structural parameters such as the ratio of rise to span, mass, damping, the ratio of length to span and the rigidity of supports, on the dynamic behaviour of single-layer cylindrical lattice shells are investigated in detail. In this paper the finite-element method is used, in which three-dimensional beam elements are employed. Both the natural frequencies and their associated modes of vibration are obtained with a subspace iteration technique, and the direct dynamic analysis method is adopted to analyse the dynamic responses of single-layer lattice shells under vertical and horizontal earthquake excitations. The objective of this study is to achieve a better understanding of the dynamic characteristics and seismic behaviour of single-layer lattice shells. The results are valuable for the earthquake-resistant design of such structures.

水平方向単一パルス波を受ける単層ラチスドームの動的座屈性状

This paper is intended as an investigation of the elasto-plastic dynamic buckling behavior of single layer lattice domes with substructures under horizontal single pulse waves. A single pulse wave is regarded as one wave of the earthquake motion or the wind load. The input waveform of single pulse wave is a half-sine pulse. Numerical analysis method is a time history response analysis taking into account the geometrical and material nonlinearities. From the results of numerical studies, the effects of the half subtended angle of dome and the duration of the half-sine pulse on the dynamic buckling behavior are made clear, and the relationship between the dynamic buckling behavior under earthquake motion and under half-sine pulse will be discussed.

Enhanced light diffraction from a double-layer microsphere lattice

Anomalously strong diffraction, whose efficiency is as high as 55%, has been observed from a double-layer microsphere lattice. The enhancement is due to the specular resonance scattering from two spheres in contact, each belonging to the top and bottom layers of the double-layer, respectively. The system thus works as a single layer two-dimensional (2D) lattice of bispheres. No enhancement is observed from a single-layer lattice nor from triple-layer lattice. It functions as a “blazed” transmission grating with 2D spectral dispersion compared with the one-dimensional dispersion in ordinary linear gratings.

A Direct Method for Buckling Analysis of Single Layer Lattice Structures

Numerous authors have studied the buckling behaviour of single layer lattice structures. Issues such as the buckling analysis in the elastic and plastic ranges, and the effects of imperfections in the failure mechanism of the structure have been investigated. However, there is still an uncertainty at the time of performing the buckling design of individual elements within the structure. This uncertainty stems from the need to approximate the effective length of each individual member. In addition, the approximate design criteria established by the different codes, and in particular Eurocode 3, are generally applicable to planar frames, but uncertain for spatial structures. This paper presents a direct one-step method for the buckling analysis of single layer lattice structures. The method avoids the use of the effective length factor of each individual element. The key point is to perform a non-linear analysis of the structure starting from an initial deformation state that includes the initial imperfections of the elements. Such an initial deformation state is obtained from the first buckling mode of the structure by a suitable scaling procedure based on an energy approach. The resulting initial deformed shape is introduced along with the external loads in a fully non-linear structural analysis that yields the resulting element stresses including the buckling effects. The performance of the method is checked by means of a series of numerical examples. The stiffness characteristics of the connections have been obtained, and included in the analysis, thus showing their influence on the behaviour of the structure.

中間荷重を受ける単層ラチスドームの座屈荷重の推定法に関する研究

The present paper studies the effects of the intermediate loads along members on the ultimate strength, that is, elasto-plastic buckling strength of single layer lattice domes and proposes an effective method to evaluate the buckling strength based on column buckling strength for members which is used to size the member sections. The method is based fundamentally on a concept of column buckling strength in terms of generalized slenderness that includes the effects of shell-like buckling with nonlinear effects before ultimate loads. The results presented in the paper confirm that the proposed method works well for the estimation.

Imperfection-Sensitive Overall Buckling of Single-Layer Lattice Domes

In this paper, the effects of geometric imperfections on the nonlinear buckling behavior of rigidly jointed single-layer lattice domes under vertical loading have been studied. A commercially available finite-element code has been used. Numerical experiments using varying levels of imperfection, chosen to be of the same forms as various linear buckling eigenmodes, have demonstrated the complexity of the buckling behavior. Lower bounds to the imperfection sensitivity of elastic overall buckling loads have been shown to result from the reduced stiffness analysis which is a simple extension to the classical linear buckling analysis. In addition an alternative elastic and plastic interaction empirical formula based upon the reduced stiffness loads has been seen to predict the lower bounds in the relatively large level of geometric imperfections.

大規模スペースフレームの動的解析に対するPCクラスタによる並列化システムの開発 : その1 改良した反復解法による並列化動的解析手法の効果について

In recent years, large-scale numerical analysis in structural design are increasingly demanded because of the necessity of realizing dynamic response analysis with elastic plastic behaviors in large-scale space frame structures. In order to realize large-scale numerical analysis, the developments of new high performance computing system without super-computers are desired. In several approaches, a parallel computing system is especially gathering the most attention for engineers. Thus the purpose of this study is to develop a parallel processing system for the dynamic analysis by using a PC cluster, which is a group of personal computers connected to a network mutually. Furthermore the calculating ability of the system is investigated by the numerical experiments for single layer lattice domes in this paper. It is demonstrated that the iteration method proposed to the dynamic analysis for structures is suitable for parallel calculations. Accordingly it was found through numerical experiments that the ability of parallel computing in this system produce good results and that parallel calculations using PC cluster with four personal computers reduce total analysis times to about 54% for models with different number of freedoms.