A general purpose real-world structural design optimization computing platform

Structural optimization has matured from a narrow academic discipline, where researchers focused on optimum design of small idealized structural components and systems, to become the basis in modern design of complex structural systems. Some software applications in recent years have made these tools accessible to professional engineers, decision-makers and students outside the structural optimization research community. These software applications, mainly focused on aerospace, aeronautical, mechanical and naval structural systems, have incorporated the optimization component as an additional feature of the finite element software package. On the other hand though there is not a holistic optimization approach in terms of final design stage for real-world civil engineering structures such as buildings, bridges or more complex civil engineering structures. The optimization computing platform presented in this study is a generic real-world optimum design computing platform for civil structural systems and it is implemented within an innovative computing framework, founded on the current state of the art in topics like metaheuristic optimization, structural analysis and parallel computing. For demonstration purposes the application of the optimization computing platform in five real-world design projects is presented.     

Mixed-integer second-order cone programming for global optimization of compliance of frame structure with discrete design variables

Frame structures are extensively used in mechanical, civil, and aerospace engineering. Besides generating reasonable designs of frame structures themselves, frame topology optimization may serve as a tool providing us with conceptual designs of diverse engineering structures. Due to its nonconvexity, however, most of existing approaches to frame topology optimization are local optimization methods based on nonlinear programming with continuous design variables or (meta)heuristics allowing some discrete design variables. Presented in this paper is a new global optimization approach to the frame topology optimization with discrete design variables. It is shown that the compliance minimization problem with predetermined candidate cross-sections can be formulated as a mixed-integer second-order cone programming problem. The global optimal solution is then computed with an existing solver based on a branch-and-cut algorithm. Numerical experiments are performed to examine computational efficiency of the proposed approach.     

Integrating a multi-objective optimization framework into a structural design software

In this paper, we present a tool combining two software applications aimed at optimizing structural design problems of the civil engineering domain. Our approach lies in integrating an application for designing 2D and 3D bar structures, called Ebes, with the jMetal multi-objective optimization framework. The result is a software package that helps civil engineers to create bar structures which can be optimized further with multi-objective metaheuristics according to different goals, such as minimizing the structure weight and minimizing the deformation. The main features of both Ebes and jMetal are described and how they are combined together in one single tool is explained. Finally a case study to illustrate how the application works is presented.     

Performance-based multiobjective optimum design of steel structures considering life-cycle cost

A new methodology for the performance-based optimum design of steel structures subjected to seismic loading considering inelastic behavior is proposed. The importance of considering life-cycle cost as an additional objective to the initial structural cost objective function in the context of multiobjective optimization is also investigated. Life-cycle cost is considered to take into account during the design phase the impact of future earthquakes. For the solution of the multiobjective optimization problem, Evolutionary Algorithms and in particular an algorithm based on Evolution Strategies, specifically tailored to meet the characteristics of the problem at hand, are implemented. The constraints of the optimization problem are based on the provisions of European design codes, while additional constraints are imposed by means of pushover analysis to control the load and deformation capacity of the structure.     

Discovering relationships between modularity and cost

While much has changed in product modularity research in the 18 years since the independence axiom, some basic questions remain unanswered. Perhaps the most fundamental of those questions is whether increasing modularity actually saves money. The goal of the research behind this paper was to clearly define the fundamental relationship between product modularity and product cost. Our previous work in modular product design provided a complete package of a product modularity measure and a modular design method. The “best” measure was created and verified after correcting common performance problems among the seven measures, finally subtracting the averaged relationships external to modules from the averaged relationship within modules. After comparing and finding better design elements among four representative modular design methods, the “best” method was developed that includes product decomposition, multi-component reconfiguration and elimination, and an extended limiting factor identification. The “best” method/measure package quickly yields redesign products with higher modularity. To seek out relationships between product life-cycle modularity and product life-cycle cost, modular product design experiments were implemented for four off-the-shelf products using the new measure/method package applied to increase both functional and retirement modularity. The modularity data recorded for each redesign included retirement modularity, manufacturing modularity and assembly modularity. Each redesign’s life-cycle cost was also obtained based on several classical cost models. The cost data recorded for each redesign included retirement cost, manufacturing cost, and assembly cost. The best relationships came from the retirement viewpoint. However, there is not a significant relationship between any life-cycle modularity and any life-cycle cost unless there are significantly large modularity changes. Life-cycle modularity-cost relationships are more likely to exist in data pools generated from that life-cycle redesign viewpoint. The beginning of modular redesign, where greater modularity improvements are seen, is more effective at reducing costs. Cost savings depend the appropriateness of the modularity matrix’s product architecture representation from a cost savings viewpoint.     

Topology Optimization in Aircraft and Aerospace Structures Design

Topology optimization has become an effective tool for least-weight and performance design, especially in aeronautics and aerospace engineering. The purpose of this paper is to survey recent advances of topology optimization techniques applied in aircraft and aerospace structures design. This paper firstly reviews several existing applications: (1) standard material layout design for airframe structures, (2) layout design of stiffener ribs for aircraft panels, (3) multi-component layout design for aerospace structural systems, (4) multi-fasteners design for assembled aircraft structures. Secondly, potential applications of topology optimization in dynamic responses design, shape preserving design, smart structures design, structural features design and additive manufacturing are introduced to provide a forward-looking perspective.     

Model-free data interpretation for continuous monitoring of complex structures

Civil engineering structures are difficult to model accurately and this challenge is compounded when structures are built in uncertain environments. As consequence, their real behavior is hard to predict; such difficulties have important effects on the reliability of damage detection. Such situations encourage the enhancement of traditional approximate structural assessments through in-service measurements and interpretation of monitoring data. While some proposals have recently been made, in general, no current methodology for detection of anomalous behavior from measurement data can be reliably applied to complex structures in practical situations.This paper presents two new methodologies for model-free data interpretation to identify and localize anomalous behavior in civil engineering structures. Two statistical methods (i) moving principal component analysis and (ii) moving correlation analysis have been demonstrated to be useful for damage detection during continuous static monitoring of civil structures.The algorithms are designed to learn characteristics of time series generated by sensor data during a period called the initialization phase where the structure is assumed to behave normally. This phase subsequently helps identify those behaviors which can be classified as anomalous. In this way the new methodologies can effectively identify anomalous behaviors without explicit (and costly) knowledge of structural characteristics such as geometry and models of behavior. The methodologies have been tested on numerically simulated elements with sensors at a range of damage severities. A comparative study with wavelet and other statistical analyses demonstrates superior performance for identifying the presence of damage.     

全寿命周期下退化的大规模系统预防性维修策略优化

单元退化情形下,考虑全寿命周期的大规模系统可靠性设计与预防性维修策略的综合优化问题将变得更为复杂.针对单元失效服从威布尔分布的情形,考虑多单元联合的预防性维修模式,构建可靠性约束下大规模系统全寿命周期成本优化模型.单元数量众多带来的组合规模指数增长问题将导致非线性择优困难,利用遗传算法编程快速求解全局最优解,包括设计阶段的单元可靠性和使用阶段的系统预防性维修周期.最后通过典型算例分析验证模型与算法的正确性和有效性,探究维修改善因子、单元可靠性和预防性维修周期等决策变量间的相互关系.研究成果有助于简化系统工程师的可靠性工程设计过程,具有一定的理论和应用价值.     

航天型号软件生存周期模型选择指南

文中首先阐述了有关生存周期模型的基本概念,简要介绍4个已在国内外航天界得到成功应用的典型生存周期模型：瀑布模型、增量模型、进化模型和基于软件包的生存周期模型,分别给出了这4个生存周期模型的优点、缺点、适用情况以及各生存周期阶段的主要产品和里程碑评审,最后给出选择航天型号软件生存周期模型的基本原则。     

Multidisciplinary aerospace design optimization: survey of recent developments

The increasing complexity of engineering systems has sparked rising interest in multidisciplinary optimization (MDO). This paper surveys recent publications in the field of aerospace, in which the interest in MDO has been particularly intense. The primary c hallenges in MDO are computational expense and organizational complexity. Accordingly, this survey focuses on various methods used by different researchers to address these challenges. The survey is organized by a breakdown of MDO into its conceptual components, reflected in sections on mathematical modelling, approximation concepts, optimization procedures, system sensitivity, and human interface. Because the authors' primary area of expertise is in the structures discipline, the majority of the references focus on the interaction of this discipline with others. In particular, two sections at the end of this review focus on two interactions that have recently been pursued with vigour: the simultaneous optimization of structures and aerodynamics and the simultaneous optimization of structures with active control.     

Enhancing disassembly and recycling planning using life-cycle analysis

Both the general public and governmental agencies highly prioritize resource optimization (energy and material) and environmental issues such as ozone, acid rain and global warming in the life-cycle context. Disassembly and recycling are also increasingly important in most industrial countries due to the significant increase in the quantity of used products being discarded. Disassembly of used products has been recognized as necessary to make recycling economically viable in current state-of-the-art reprocessing technology. This emerging trend requires incorporating environmental considerations into design strategies. This study presents a graph-based heuristic method for disassembly analysis of end-of-life products, which incorporates the Eco-Design concept. Product components and their assembly relationships from the bill of material BOM are adopted to split the graph into sub-graphs denoting modular sub-assemblies. The life-cycle analysis LCA is then used to analyze disassembly trees, from which a disassembly sequence can be derived. Designers can use the analytical results to evaluate the dis-assemblability and recyclability of products when they are designed.     

Flight-vehicle structures education in the united states—Assessment and recommendations

An assessment is made of the technical contents of flight-vehicle structures curricula at 41 U.S. universities with accredited aerospace engineering programs. The assessment is based on the technical needs for the new and projected aeronautical and space systems as well as on the likely characteristics of the aerospace engineering work environment. A number of deficiencies and areas of concern are identified and recommendations are presented for enhancing the effectiveness of flight-vehicle structures education. A number of government supported programs that can help aerospace engineering education are listed in the appendix.     

CAD系统中混合语言间的数据交换技术研究

在土木工程CAD系统开发过程中,常常需要用多种语言进行混合编程,如何充分发挥各种开发语言的优点又能够使整个系统成为一个有机的整体是一个难点。先对混合语言程序设计进行概述,然后结合非杆件结构CAD系统的开发探讨多种混合语言之间的数据交换技术。     

Time-dependent reliability of textile-strengthened RC structures under consideration of fuzzy randomness

The reliability of civil engineering structures is time-dependent. By means of strengthening it is possible to improve the load-bearing capacity and serviceability of structures and simultaneously to increase structural reliability. In this paper, we focus on the time-dependent reliability assessment of RC structures strengthened by textile-reinforced fine-grade concrete layers.The paper starts with a short introduction concerning textile strengthening of RC structures and the underlying mechanical model. The uncertain material parameters of textile-strengthened structures are then investigated. The uncertain parameters are quantified as fuzzy variables or fuzzy random variables. In order to take account of the latter in the assessment of the time-dependent reliability a new fuzzy probabilistic safety concept is presented. The fuzzy adaptive importance sampling (FAIS) method is introduced. The algorithm is demonstrated with an example. The uncertainty of the input parameters is comprehensively reflected in the uncertainty of the computed fuzzy reliability index. The assessment of the uncertain results is discussed.     

基于全寿命管理的通用型交互式电子手册系统设计

本文从装备全寿命管理思想出发,提出了通用型交互式电子技术手册系统的设计思想。并根据装备管理过程中各类用户的不同需求,设计系统总体框架,对相应的实现技术做了说明。系统摆脱了原有交互式电子手册设计中采用的局部改造和重新设计的思维定式,提出了系统统一管理、装备全程维护的新思路,具有一定的实践意义。     

Integrating a constraint-based optimization approach into the design of oil & gas structures

Currently, design optimization is widely applied in civil and mechanical engineering. Optimization strategies are used to enhance the product performance and reduce the cost, lead time and environmental impacts related to the product lifecycle. In this context, evolutionary algorithms are used for determining the optimum solution in engineering problems. The design of complex products, such as those that are engineered to order, often requires the study of subproblems. Modularization is a common practice to reduce the complexity; however, the configuration practices are difficult to be applied in engineered to order products. As a solution, the integration of the optimization tools and model-based simulations is proposed to manage the complexity. However, even when a commercial software is available to support the parameter optimization, there may exist a lack of design tools that can be integrated with the product structure of an engineered to order product. This paper describes a design optimization approach that integrates a Constraint Satisfaction Problem (CSP) tool with model-based simulations in a collaborative design context. A platform tool is developed using the .NET and MiniZinc languages. The case study is focused on the design optimization of a 700-ton steel structure. In particular, the optimization analysis considers the mechanical behavior, weight, and cost reduction.     

An expert system on design of liquid-retaining structures with blackboard architecture

Abstract: The design of liquid‐retaining structures involves many decisions to be made by the designer based on rules of thumb, heuristics, judgement, codes of practice and previous experience. Structural design problems are often ill structured and there is a need to develop programming environments that can incorporate engineering judgement along with algorithmic tools. Recent developments in artificial intelligence have made it possible to develop an expert system that can provide expert advice to the user in the selection of design criteria and design parameters. This paper introduces the development of an expert system in the design of liquid‐retaining structures using blackboard architecture. An expert system shell, Visual Rule Studio, is employed to facilitate the development of this prototype system. It is a coupled system combining symbolic processing with traditional numerical processing. The expert system developed is based on British Standards Code of Practice BS8007. Explanations are made to assist inexperienced designers or civil engineering students to learn how to design liquid‐retaining structures effectively and sustainably in their design practices. The use of this expert system in disseminating heuristic knowledge and experience to practitioners and engineering students is discussed.     

BLISS/S: a new method for two-level structural optimization

The paper describes a two-level method for structural optimization for a minimum weight under the local strength and displacement constraints. The method divides the optimization task into separate optimizations of the individual substructures (in the extreme, the individual components) coordinated by the assembled structure optimization. The substructure optimizations use local cross-sections as design variables and satisfy the highly nonlinear local constraints of strength and buckling. The design variables in the assembled structure optimization govern the structure overall shape and handle the displacement constraints. The assembled structure objective function is the objective in each of the above optimizations. The substructure optimizations are linked to the assembled structure optimization by the sensitivity derivatives. The method was derived from a previously reported two-level optimization method for engineering systems, e.g. aerospace vehicles, that comprise interacting modules to be optimized independently, coordination provided by a system-level optimization. This scheme was adapted to structural optimization by treating each substructure as a module in a system, and using the standard finite element analysis as the system analysis. A numerical example, a hub structure framework, is provided to show the new method agreement with a standard, no-decomposition optimization. The new method advantage lies primarily in the autonomy of the individual substructure optimization that enables concurrency of execution to compress the overall task elapsed time. The advantage increases with the magnitude of that task. Received December 5, 1999?Revised mansucript received April 26, 2000     

外流作用下管道流固耦合非线性动力学研究进展

管道广泛应用于海洋、核电以及航空航天等重大工程中,是采油平台、蒸汽发生器等重要工程装备的关键结构之一.当有外部流体经过时,管道会发生流固耦合振动行为,是导致重大装备振动破坏和失效的重要原因之一,已成为重大工程设计必须解决的关键问题.本文针对外流作用下柔性管道流固耦合非线性动力学机理这一科学问题,梳理了国内外学者的重要研究成果,重点分析了柔性管道分别在横向外流和轴向外流作用下的流固耦合非线性振动行为.从实验研究、仿真分析和理论建模等方面进行了深入地探讨,揭示了外部流体对管道动力学行为的影响机制.最后,对当前国内外研究现状进行了简要的总结,并给出了这一研究仍存在的难点与挑战.     

Modified-modal-pushover-based seismic optimum design for steel structures considering life-cycle cost

A modified-modal-pushover-based optimization technique is presented to design steel moment resisting frame buildings for minimizing the life-cycle cost based on the framework of performance based earthquake engineering. Modified modal pushover analysis (MMPA) procedure capturing the higher mode effect well is utilized to analyze the inelastic seismic demands of the structures subjected to the considered design earthquakes in terms of the Chinese seismic code for buildings, especially for the medium- to high-rise buildings. Furthermore, the life-cycle cost is formulated as the summation of the initial material cost and the future expected damage loss, which can be stated as a function of seismic performance levels and their corresponding failure probability by means of a statistical model. Meanwhile, the damage loss is explicitly and continuously expressed by the defined interstory drift index using the fuzzy-decision theory. Moreover, the powerful adaptive simulated annealing algorithm is applied to solve the discrete optimization problem due to the discreteness of standard steel sections. Finally, a 9-story planar steel frame is provided to illustrate the effectiveness of the proposed optimization design technique, which achieves not only more cost-effective design but greatly improves the robustness of the optimum design as well.