Large Space Frames Research Articles

Application and Seismic Analysis of changing masonry structure into bottom frame structure

In order to meet the requirements of people for the use of large space, the masonry structure building is underpinned, the load-bearing wall of the building is removed, and the underpinning beam is constructed to replace the original load-bearing wall to bear the upper load, the bottom masonry structure is transformed into a large space frame structure. Based on the analysis of two different underpinning methods, this paper selects the structural underpinning method according to their advantages and disadvantages, and takes an example as an example to summarize the construction of underpinning beam structure first. Then the main construction methods and matters needing attention of the underpinning technology for removing the load-bearing wall in the construction process, so as to provide a certain basis for the future construction of the structure. Through the displacement loading method, the bearing capacity of frame beam and underpinning beam is analyzed, and the data are processed, and the advantages and disadvantages of underpinning beam and frame beam under load are obtained.

A wavelet-based scheme for impact identification of framed structures using combined genetic and water cycle algorithms

This paper presents a synthesis strategy for impact force localization and identification of framed structures in time-domain using a two-step wavelet-based fitness evaluation scheme in conjunction with genetic and water cycle algorithms. For this purpose, a straightforward approach is developed for sensitivity analysis of accelerations and spatial signal connecting the peak values. The proposed scheme is capable of using diverse scales of wavelet functions at considerably small sampling rates. A decimal genetic algorithm (GA) coding system and a recently developed water cycle algorithm (WCA) are improved to be used for impact localization and identification, respectively. The fitness evaluation is then modified for using the obtained results from sensitivity analysis rather than the acceleration itself. Numerical study is first conducted for a large space frame to evaluate the precision, convergence, and efficiency of the identified results using the proposed GA-WCA strategy to different measurement scenarios and initial estimates of the structural model. For comparison purposes, the robustness of WCA in identification step is thoroughly compared with other three state-of-the-art optimization algorithms i.e., particle swarm optimization (PSO), imperialist competitive algorithm (ICA), and differential evolution (DE). Afterwards, an experimental validation study is carried out on a laboratory scale truss bridge. It is concluded that the computational performance of the proposed method is significantly better than the existing methods with respect to fitness evaluation. Results show that, even for the cases with a rough knowledge on structural parameters, the impact force is successfully identified with an excellent precision. This demonstrates the superiority of WCA strategy in handling the global search over large design space with large number of design variables. It is also concluded that the impact localization step is accomplished very fast, thus providing a near real-time strategy in dealing with large-scaled frame and bridge structures.

03.12: Global structural modelling of space frame structures with consideration of joint behaviour: An integral analysis approach

ABSTRACTThe effects of the behaviour of joints on the distribution of internal forces and moments within a structure and on the overall deformations of the structure are generally neglected [1]. However, where such effects are significant, they should be taken into account. Provisions are given in Eurocode 3, Part 1‐8 [2] for analysis, classification and modelling of joints with respect to rotational degrees of freedom. Provisions for translational degrees of freedom are missing.In shear connections slip may occur in case slip resistance is smaller than design load. This holds true for shear connections category A and B according to Eurocode 3, Part 1‐8 [2]. In structures with predominant normal forces such slip effects may accumulate and considerably affect the internal forces as well as the deflections. Structural modelling and calculation of slip effects is a complicated task in structural mechanics. In this paper, concepts are presented how to consider slip effects in joints when dealing with large space frame structures. Stick‐slip‐models are outlined and implemented in 3d structural models. Calculation techniques are discussed relating to the additional degrees of freedom (statically over‐determined systems) and the non‐linear behaviour.The importance and benefit of this integral analysis approach, where the effects of the joints are considered in the global modelling, are illustrated by the example of the Louvre Abu Dhabi Dome. The dome measures 185m in diameter and consists of approx. 11'000 steel members, most of which having shear connections. The results show that slip in joints must not be neglected in the global structural analysis. The quality and accuracy of the calculated results are verified by deflection measurements on site.

Large Deformation of Inelastic Large Space Frame. II: Application

Material and geometric nonlinear analysis of the tested models for a large space frame is presented based on the 1D finite-element method. The analytical results have been confirmed to agree sufficiently with the experimental results up to a large deformed state. Members-coupled buckling of continuous chords and complicated collapsed states were simulated well. The analytical results of the partial models have shown that coupled buckling between several continuous chords appears to be asymmetric because of the difference in axial forces allowed by adjacent members. Except for whole bucklinglike phenomena, it is possible to analyze a large and complicated space frame with elastoplastic coupled buckling up to a large deformed state.

Optimization of Large Space Frame Steel Structures

Optimization of large space frame steel structures subjected to realistic code-specified stress, displacement, and buckling constraints is investigated. The basis of design is the American Institute of Steel Construction (AISC) Allowable Stress Design (ASD) specifications. The types of structures considered are space moment resisting frames with and without bracings. The structures are subjected to wind loadings according to the Uniform Building Code (UBC) in addition to dead and live loads. The parallel-vector algorithm developed in this research is applied to three highrise building structures ranging in size from a 20-story structure with 1,920 members to a 60-story structure with 5,760 members, and its parallel processing and vectorization performance is evaluated. For the largest structure, speedups of 6.4 and 17.8 are achieved due to parallel processing (using eight processors) and vectorization, respectively. When vectorization is combined with parallel processing a very significant speedup of 97.1 is achieved.

1次元有限要素法による大規模立体骨組の複合非線形解析

Materially and geometrically non-linear analysis of the tested models for a large space frame is presented based on one-dimensional finite element method. The analytical results have been confirmed to agree sufficiently with the experimental ones up to a large deformed state. Coupled chord bucklings and complicated collapsed states were simulated well. The analytical results of the partial models have shown that coupled buckling between several chords appears asymmetric because of the difference of axial forces allowed by adjacent members. Except for whole buckling-like phenomena, it is possible to analyze a large and complicated space frame with elasto-plastic coupled bucklings up to a large deformed state.

Exact Parametric Study Giving Insight into Dome Vibrations

A parametric study is presented of the undamped free vibration of a one layer truss type circular dome, with terrestrial proportions. The dome is composed of 36 identical portions, but is supported at only 4, 6, 9, 12, 18 or 36 uniformly spaced points. Only one of the 36 portions is needed in the analysis, using the large space frame computer program BUNVIS-RG, which can analyse linearly repetitive or rotationally periodic structures ‘exactly’, e.g. without the usual finite element discretisation approximations. The study includes changing: the height to diameter ratio; the number of supports; the type of supports; and the type of joint from rigid to pinned connections. In addition, modal densities are found for a near optimum dome. The method used gives valuable insights into the exact mode shapes by showing that they are always composed entirely of a (usually short) finite series of circumferential sine waves.

On the convergence quality of minimum-weight design of large space frames under multiple dynamic constraints

Weight optimization of large space frames under dynamic constraints requires adaptable design search techniques because of the enormous number of sizing variables, the highly nonlinear frequency constraint surfaces, and the multiple points of local minima. With modern OC procedures, based on alternately satisfying the constraints (scaling) and applying the Kuhn-Tucker (optimality) condition (resizing), the convergence to weight minima is oftentimes oscillatory. Even though the convergence rate for OC methods is initially fast, it gradually slows near local extrema, mainly because the selection of appropriate step sizes (or move limits) in the redesign phase becomes increasingly difficult. The focus here is to create specific criteria based on past scaled designs to “damp out” the oscillatory convergence propensity of OC recursive methods. Several OC recursive strategies, which are frequently worked to resize and to evaluate the Lagrange multipliers, are steered by the present approach to design large space frames under multiple dynamic constraints. Besides this, the design iteration histories obtained by the various recursive strategies are compared graphically. On the whole, the present OC approach achieves a smooth upper-bound convergence to weight minima, as it quickly dissolves the (sometimes violent) oscillations of scaled weights in the iteration history. Most of all, the method eliminates the need for adjustments of internal parameters during the redesign phase.

Nonlinear Analysis of Thin‐Walled Structures Using Least Element/Member

The paper presents the derivation of a deformation stiffness matrix for an asymmetric thin-walled beam-column element. This matrix KD is a function of element deformation and incorporates the coupling between axial stretching and the lateral and torsional deformations. The stiffness matrix derived and the solution procedure proposed may be used together with the linear and geometric stiffness matrices for thin-walled beam-column elements to analyze large deflection behavior of space frames comprising members in which the influence of sectorial warping in the section can be neglected. These include members with solid, tubular hollow, or angle type sections. The formulation has been applied to a variety of sample problems involving arbitrarily large deflections. Results obtained from the approach using only one element per member in most cases agree very well with independent analytical and other published finite element solutions. The proposed method is suitable for analyzing the nonlinear behavior of large space frames, such as transmission towers.

Space Station Structure Modal Selection Criteria

In many dynamic analysis procedures the size of the problem is curtailed by truncation of the modes selected for study. A preferable approach in the case of a structure such as a large space frame is to identify and include those natural modes in the order of their increasing importance. Two of the many criteria which can be used to determine importance are examined in this paper. The first involves establishment of a “completeness index” reflecting the model identities satisfied by the natural frequencies and integrals of the mode shapes. The second involves displacements at a point of excitation and a response point. Both selection methods are implemented on a simplified model of the Initial Operating Configuration Space Station and comparative transient response analyses are made. It is shown that mode selection is a function of more than one variable. The first method performs well in reducing model error yet the second is necessary to predict those modes excited by various forcing functions when control of displacements is the chief concern. Different mode selection criteria will be necessary when other variables are involved.