A cellular framework for structural analysis and optimization

Due to the technological advances in computer hardware and software tools, structural optimization has been gaining continuously increasing interest over the last two decades. The purpose of the present work is to quantitatively compare three metaheuristic optimization algorithms, namely the Differential Evolution, Harmony Search and Particle Swarm Optimization methods, in the framework of structural optimization. The comparison of the optimizers is performed with reference to their efficiency (overall computing demands) and robustness (capability to detect near-optimal solutions). The optimum design of a real-world overhead traveling crane is used as the test bed application for conducting optimization test runs.

This study presents a unified reanalysis approach for structural analysis, design, and optimization that is based on the Combined Approximations (CA) method. The method is suitable for various analysis models (linear, nonlinear, elastic, plastic, static, dynamic), different types of structures (trusses, frames, grillages, continuum structures), and all types of design variables (cross-sectional, material, geometrical, topological). The calculations are based on results of a single exact analysis. The computational effort is usually much smaller than that needed to carry out a complete analysis of modified designs. Accurate results are achieved by low-order approximations for significant changes in the design. It is possible to improve the accuracy by considering higher-order terms, and exact solutions can be achieved in certain cases. The solution steps are straightforward, and the computational procedures presented can readily be used with general finite element systems. Typical results are demonstrated by numerical examples.

Summary form only given as follows. Software has been developed for the last two decades using the traditional structured analysis and design (SAD) approaches or some variations of this approach. Now in the 1990s, there is a radical shift in the software development approach; most notable is the emergence of object-orientation (OO). We discuss the various opportunities and challenges imposed by the OO technology along with the associated changes needed in the organization structure for its adoption as well as changes required in the management activities.

In this paper, the principles of the developed structural analysis approach for reactive moulding processes are rationalised and described. So far in the industry, the prediction of reactive moulding process induced problems that are directly related to the structural integrity of a finished product have largely been disregarded in the simulations. With the addition of the structural analysis method for reactive moulding processes, the fully three-dimensional simulation approach has been extended to cover all the process stages from mould filling, curing and post-casting heat treatment to final cooling down. The relevant physical phenomena, such as thermal and chemical deformations, that are affecting the structural integrity of analysed castings are taken into account. The utilisation of the structural analysis approach to a medium voltage industrial application case along with selected results is presented later in the paper. The combined effects of numerous variables contributing to the casting process formulate the biggest challenge for reliable analysis results.

Purpose — Analysis of nonprismatic members has received a great deal attention from designers and engineers due to their ability in satisfaction of architectural and aesthetic necessities. Using these structural members in complex structures such as aircrafts, turbine blades and space vehicles, exact static and dynamic analyses of these members become more significant. Based on structural/mechanical principles, the purpose of this paper is to present a new method to evaluate exact structural matrices for nonprismatic Euler‐Bernoulli beam elements. Design/methodology/approach — Through introducing the concept of basic displacement functions (BDFs), it is shown that exact shape functions are derived in terms of BDFs. BDFs and their derivatives have structural interpretations; therefore, they are obtained via application of flexibility method. Unlike the conventional methods, which are almost categorized as displacement‐based methods, the flexibility basis of the method ensures the true satisfaction of equilibrium equations at any interior point of the element. Findings — The exact shape functions and consequently structural matrices are derived for general nonprismatic beam elements. Numerical examples are carried out to determine static deflection and natural frequencies, and the results are highly competent with the other methods in literature. Research limitations/implications — The method can be extended to structural analysis of curved beams, plates and shells as well. Moreover, it is possible to derive exact dynamic shape functions via BDFs by solving the governing equation for transverse vibration of beams. Theoretically, the method faces limitation in analysis of nonprismatic beams that converge to a point where cross‐sectional area and moment of inertia are equal to zero. Practical implications — The development of this idea, i.e. BDFs seems to lead to promotive novel approaches for structural analysis and could be a breaking point for developing new elements for plates and shells as it was shown for beam elements. Originality/value — The paper's introduction of special functions, namely BDFs and their application, in both static and dynamic analyses of structures, could be a breaking point in analysis procedures.

Intracellular processes are cascades of biochemical reactions, triggered in response to various types of stimuli. Mathematical models describing their dynamics have become increasingly popular in recent years, as tools supporting experimental work in analysis of pathways and regulatory networks. Not only do they provide insights into general properties of these systems, but also help in specific tasks, such as search for drug molecular targets or treatment protocols. Different tools and methods are used to model complex biological systems. In this work, we focus on ordinary differential equations (ODEs) and Petri nets. We consider specific methods of analysis of such models, i.e., sensitivity analysis (SA) and significance analysis. So far, they have been applied separately, with different goals. In this paper, we show that they can complement each other, combining the sensitivity of ODE models and the significance analysis of Petri nets. The former is used to find parameters, whose change results in the greatest quantitative and qualitative changes in the model response, while the latter is a structural analysis and allows indicating the most important subprocesses in terms of information flow in Petri net. Ultimately, both methods facilitate finding the essential processes in a given signaling pathway or regulatory network and may be used to support medical therapy development. In the paper, the use of dual modeling is illustrated with an example of ATM/p53/NF-kappaB pathway. Each method was applied to analyze this system, resulting in finding different subsets of important processes that might be prospective targets for changing this system behavior. While some of the processes were indicated in each of the approaches, others were found by one method only and would be missed if only that method was applied. This leads to the conclusion about the complementarity of the methods under investigation. The dual modeling approach of comprehensive structural and parametric analysis yields results that would not be possible if these two modeling approaches were applied separately. The combined approach, proposed in this paper, facilitates finding not only key processes, with which significant parameters are associated, but also significant modules, corresponding to subsystems of regulatory networks. The results provide broader insight into therapy targets in diseases in which the natural control of intracellular processes is disturbed, leading to the development of more effective therapies in medicine.

Active bending is an increasingly popular construction technique that uses elastically bent structural members to form complex curved shapes. The design and analysis of bending-active structures requires an accurate simulation of the bending process, which is often complicated by the occurrence of large displacements. In this article, we propose to combine a previously developed implicit dynamic relaxation method with co-rotational beam elements to obtain a fast and accurate method for form-finding and analysis of bending-active structures. This approach is applied to four test cases. Implicit dynamic relaxation is compared to the classic Newton–Raphson method and conventional dynamic relaxation. The results show that the proposed implicit dynamic relaxation approach can be stabilized intuitively by changing the time step and damping ratio, making it more stable than the classic Newton–Raphson method. Moreover, the proposed approach converges fast compared to the conventional dynamic relaxation: the total computation time is considerably lower, even though the computation time per iteration is higher. Finally, a high accuracy is achieved due to the use of co-rotational beam elements. The combination of high accuracy and low computation time makes this approach well-suited for both form-finding and analysis of bending-active structures.

Four alternative analytical procedures are recommended by the design codes for the structural analysis of buildings under earthquake loading. The objective of this chapter is to assess these procedures by integrating them in the framework of structural optimization. The evaluation is based on the European seismic design code, where procedures based on both linear and nonlinear response history analysis are adopted. In order to realistically simulate seismic actions, suites of both natural and artificial ground-motion records are used. For the solution of the optimization problem an evolutionary algorithm is adopted. The results obtained demonstrate the advantages of using more elaborate seismic design procedures, based on a detailed simulation of the structural behaviour and the applied seismic loading, as opposed to the commonly used simplified design methodologies. Designs with less material cost combined with better seismic performance are obtained when nonlinear response history analysis is performed.

ABSTRACTModern methodologies for the analysis of composite structures are demanded to satisfy the accuracy requirements at different scales, from micro to macro and possibly in a global/local sense. In this domain, the present paper proposes a hierarchical, component-wise approach for the linear static analysis of layered structures. By employing the Carrera Unified Formulation and a variational statement, finite element arrays of refined beam models are expressed in terms of fundamental nuclei. Legendre-based polynomials are utilized to implement, in a hierarchical form, higher-order beam kinematics. Also, curved cross-section geometries are formulated in a correct and consistent manner through mapping blending functions. Mapping and refined kinematics beam models are, thus, inherently combined to give the component-wise method, according to which each component of the structure (e.g., layer, fibers, and matrix) is modeled independently and with its geometric and mechanical characteristics. This approach is demonstrated to provide enhanced accuracy for the analysis of composite structures, from layer scale to fiber-matrix level, but still with low computational costs.

Functional and structural analyses of behavior: Approaches leading to reduced use of punishment procedures?

ABSTRACTThis work focuses on developing a design methodology for reliable control system instrumentation. This methodology aims at optimising the instrumentation using a dependability criterion based on reliability and cost. The design methodology is primarily based on three processes: structural analysis of the relations between different variables and physical quantities that govern the system; evaluation of the reliability of the main mission of the control system instrumentation using the structural links, which depends on a graphical tree representation of the system in the design phase; and optimisation, which allows us to determine the best architecture for instrumentation. This methodology is illustrated for the design of an electric vehicle.

Structural configuration modeling and finite element analysis of crew exploration vehicle (CEV) concepts are presented. In the structural configuration design approach, parametric solid models of the pressurized shell and tanks are developed. The CEV internal cabin pressure is same as in the International Space Station (ISS) to enable docking with the ISS without an intermediate airlock. Effects of this internal pressure load on the stress distribution, factor of safety, mass and deflections are investigated. Uniform 7 mm thick skin shell, 5 mm thick shell with ribs and frames, and isogrid skin construction options are investigated. From this limited study, the isogrid construction appears to provide most strength/mass ratio. Initial finite element analysis results on the service module tanks are also presented. These rapid finite element analyses, stress and factor of safety distribution results are presented as a part of lessons learned and to build up a structural mass estimation and sizing database for future technology support. This rapid structural analysis process may also facilitate better definition of the vehicles and components for rapid prototyping. However, these structural analysis results are highly conceptual and exploratory in nature and do not reflect current configuration designs being conducted at the program level by NASA and industry.

Periodic structures have attracted much attention in the past decades due to numerous applications such as metamaterials, antenna arrays, frequency selective surface (FSS), photonic band gap (PBG) or electromagnetic band gap (EBG) structures, etc. Infinite periodic structures are impossible in a realistic fabrication. When truncating infinite periodic structures, discontinuities occur at the interface and surface waves will be excited according to mode conversion, which leads to the edge effect of finite periodic structures. The prediction of wave natures in the edge cells of finite periodic structures is an indispensable procedure during the design of finite periodic structures. The conventional element-by-element method is rigorous and suitable for small finite arrays. However, it requires heavy computational resources for very large arrays. The well-established infinite periodic approximation approach neglecting the edge effect, although reduces the computational domain to a unit cell, is not sufficiently accurate for engineering applications.

This paper proposes a new approach for the FE analysis of composite structures by means of 1D refined models that have been derived in the framework of the Carrera Unified Formulation (CUF). CUF provides hierarchical higher-order structural models with arbitrary expansion orders. Taylorand Lagrange-type polynomials were used to interpolate the displacement field over the element cross-section. The proposed new approach, referred to as Composite-Wise (CW), is able to provide stress and strain fields with solid-like accuracy and very low computational cost. Within the CW approach, different scale components (fiber, matrix, laminae and laminates) can be simultaneously considered in the same structural model. Failure analyses are conducted by implementing well-known failure criteria. Furthermore, an integral evaluation of failure parameters is introduced to determine critical portion of the structure where failure could take place. Results are provided to show the enhaced capability of the present formulation in the failure analysis of fiber-reinforced composite structures by the detection of detailed displacement/stress fields with reduced computational cost.

A formulation is developed for analyzing the dynamic response of multi-support structures with coupled non-classical damping using spectral moments instead of the frequently used cross-correlation coefficients. Its advantages are that the formulation considering the modal response variances and cross-covariances is more efficient in calculation than the conventional formulation, and the coupled damping of structure is taken into consideration. For the dynamic analysis of a structure equipped with coupled damper, the classical mode decomposition method is inapplicable and the velocity term of the external load in vibration equation cannot be neglected. The dynamic equation is firstly decoupled by complex mode decomposition method in this paper. Then, the complete SRSS rule (c-SRSS) addressed by Heredia-Zavoni [2011, 2015] is developed to consider the non-classically damping system under multi-support excitations. Moreover, spectral moments of orders higher than 3 are newly introduced into the dynamic analysis and the convergence difficulty for these spectral moments is overcome by employing the band-limited power spectra. A large-span structure equipped with a coupled damper is taken as an example to calculate its dynamic response using the conventional and proposed formulations, and numerical results show that the proposed formulation is accurate and efficient.