Optimization design of piles subjected to horizontal loads based on reliability theory

Based on reliability theory,a general method for the optimization design of piles subjected to horizontal loads is presented.This method takes into consideration various uncertainties caused by pile installation,variability of geotechnical materials from one location to another,and so on.It also deals with behavior and side constraints specified by standard specifications for piles.To more accurately solve the optimization design model,the first order reliability method is employed.The results from the numerical example indicate that the target reliability index has significant influence on design parameters.In addition,the optimization weight increases with the target reliability index.Especially when the target reliability index is relatively large,the target reliability index has significant influence on design weight of piles.

考虑多失效模式的桩锚结构鲁棒性设计及经济性优化

目的 研究岩土力学参数的不确定性对桩锚支护体系的整体影响,探究经济性和鲁棒性共同作用的优化设计。方法 选取黄土地区工程案例,考虑支护桩隆起破坏、支护桩倾覆破坏、整体稳定性破坏三类破坏形式,使用蒙特卡洛及点估计法嵌套的方式求出不同设计组合下的失效概率及标准差;同时考虑优化设计的经济性,筛选出桩锚支护结构体系的鲁棒性优化设计方案。结果 随着桩长增加,主控模式由隆起破坏向整体稳定性改变,不同的几何参数对结构鲁棒性影响不同,优化后可以获得同时满足经济性、鲁棒性及可靠度要求的最佳设计方案。结论 在桩锚结构设计中考虑经济性优化及多失效模式的鲁棒性设计是必要的。

基于混合和谐搜索算法的自压滴灌田间管网多目标优化设计

为了综合考虑管网投资和水压分布,合理进行管网布置和管径选择,以满足管网的经济性和可靠性,使自压滴灌管网系统达到投资最低和灌水均匀度最高的目的。以管网投资最低(管网经济性)和节点富余水头均值最小(管网可靠性)为目标,建立了自压滴灌“梳子”形和“丰字”形田间管网系统的多目标优化数学模型,提出了混合和谐搜索算法求解多目标优化模型的方法和步骤。以新疆某自压滴灌工程为例,采用该方法对其田间管网系统进行优化,优化方案的管网总投资为47.63万元,与原设计方案相比降低了9.86%;管网节点富余水头均值为8.87 m,与原设计方案相比降低了28.37%。该优化设计方法得到的优化结果,不仅节省投资明显,而且节点富余水头均值显著减小,说明管网系统的压力偏差小,灌水的均匀度显著提高。优化结果表明,混合和谐搜索算法收敛速度快,计算精度高,在自压滴灌管网的多目标优化设计中具有很好的应用价值。

System reliability-based robust design of deep foundation pit considering multiple failure modes

Recently,reliability-based design is a universal method to quantify negative influence of uncertainty in geotechnical engineering.However,for deep foundation pit,evaluating the system safety of retaining structures and finding cost-effective design points are main challenges.To address this,this study proposes a novel system reliability-based robust design method for retaining system of deep foundation pit and illustrated this method via a simplified case history in Suzhou,China.The proposed method included two parts:system reliability model and robust design method.Back Propagation Neural Network(BPNN)is used to fit limit state functions and conduct efficient reliability analysis.The common source random variable(CSRV)model are used to evaluate correlation between failure modes and determine the system reliability.Furthermore,based on the system reliability model,a robust design method is developed.This method aims to find cost-effective design points.To solve this problem,the third generation non-dominated genetic algorithm(NSGA-III)is adopted.The efficiency and accuracy of whole computations are improved by involving BPNN models and NSGA-III algorithm.The proposed method has a good performance in locating the balanced design point between safety and construction cost.Moreover,the proposed method can provide design points with reasonable stiffness distribution.

Reliability-based robust design optimization of vehicle components, Part Ⅱ： Case studies

The reliability-based optimization, the relia- bility-based sensitivity analysis and robust design method are employed to propose an effective approach for reliability-based robust design optimization of vehicle components in Part I. Applications of the method are further discussed for reliability-based robust optimization of vehicle components in this paper. Examples of axles, torsion bar, coil and composite springs are illustrated for numerical investigations. Results have shown the proposed method is an efficient method for reliability-based robust design optimization of vehicle components.

Reliability-based components, Part robust design optimization of vehicle I： Theory

The reliability-based design optimization, the reliability sensitivity analysis and robust design method are employed to present a practical and effective approach for reliability-based robust design optimization of vehicle components. A procedure for reliability-based robust design optimization of vehicle components is proposed. Application of the method is illustrated by reliability-based robust design optimization of axle and spring. Numerical results have shown that the proposed method can be trusted to perform reliability-based robust design optimization of vehicle components.

A Dynamic Programming Approach to the Design of Composite Aircraft Wings

A light and reliable aircraft has been the major goal of aircraft designers. It is imperative to design the aircraft wing skins as efficiently as possible since the wing skins comprise more than fifty percent of the structural weight of the aircraft wing. The aircraft wing skin consists of many different types of material and thickness configurations at various locations. Selecting a thickness for each location is perhaps the most significant design task. In this paper, we formulate discrete mathematical programming models to determine the optimal thicknesses for three different criteria: maximize reliability, minimize weight, and achieve a trade-off between maximizing reliability and minimizing weight. These three model formulations are generalized discrete resource-allocation problems, which lend themselves well to the dynamic programming approach. Consequently, we use the dynamic programming method to solve these model formulations. To illustrate our approach, an example is solved in which dynamic programming yields a minimum weight design as well as a trade-off curve for weight versus reliability for an aircraft wing with thirty locations (or panels) and fourteen thickness choices for each location.

基于协同平衡的可靠性冗余设计优化算法

可靠性冗余设计优化是航天装备研发工作的重点之一。在系统可靠性平衡优化的基础上提出了协同平衡的新概念,即利用单元协同变化实现复杂系统可靠性冗余设计的进一步优化。所提算法充分考虑冗余单元变化对复杂系统可靠度、费用、体积、质量和功耗等性能参数的影响,可以解决各类可靠性冗余设计优化问题。计算结果表明基于单元协同平衡的可靠性冗余设计优化算法可以有效实现可靠性冗余设计的优化目标,同时具有计算成本低、效率高等优点。

满足可靠性要求的轻量化车身结构多目标优化方法

车身结构轻量化设计需要满足模态、刚度和碰撞安全等多项性能要求;同时为了提高设计方案的鲁棒性,必须在设计过程中考虑不确定性因素的影响。在各种方法中,非支配排序遗传算法NSGA-Ⅱ在工程设计的多目标和可靠性设计中应用越来越广泛。在采用高强度钢板后,为确定某车身前端结构的关键零件的厚度参数,分别建立白车身有限元模型和40%偏置正面碰撞的简化模型;在优化模型中综合考虑白车身扭转刚度、最大碰撞力及平均作用力、碰撞吸能要求和质量最轻等多个性能指标要求,在构建高精度的响应面近似模型的基础上,采用非支配排序遗传算法(NSGA-Ⅱ)对其进行6σ可靠性优化设计;运用蒙特卡罗模拟技术对优化方案的鲁棒性进行评价。优化结果提高了整车的碰撞安全性,同时白车身扭转刚度和零件重量得到了很好的控制。

基于协同优化和多目标遗传算法的车身结构多学科优化设计

在汽车车身结构NVH和侧面碰撞安全性研究中,实施多学科多目标优化的可行性设计。通过试验设计制定试验方案并进行数据采样,构建考虑整车侧撞安全性、白车身模态、静态弯曲刚度、扭转刚度和轻量化等性能的响应面近似模型,然后对车身结构分别进行确定性和可靠性轻量化单目标设计。最后,运用多目标遗传算法结合多学科协同优化对车身结构进行多目标优化设计,获取Pareto最优化解集。研究结果表明:可靠性优化设计较确定性优化设计而言,能考虑产品设计和生产过程中的不确定性因素,保证产品稳健性;车身结构的多目标优化设计全面考虑了车身结构轻量化、NVH和碰撞安全性能等多学科之间的耦合和解耦;设计者可按需选择其满意的优化结果,这将大幅缩减产品开发周期、降低产品开发成本。

汽车零部件的可靠性稳健优化设计——理论部分

将可靠性优化设计理论与可靠性灵敏度分析方法相结合 ,讨论了汽车零部件的可靠性稳健优化设计问题 ,提出了可靠性稳健优化设计的计算方法。把可靠性灵敏度融入可靠性优化设计模型之中 。

机械零部件动态可靠性稳健优化设计的群智能算法

在运用随机过程和顺序统计原理建立载荷和强度随时间变化的动态可靠性模型基础上,利用稳健设计理论,建立了机械零部件动态可靠性稳健优化设计的多目标优化模型。针对该多目标模型所具有的动态高维的特点,提出了基于灰色关联分析的多粒子群协同动态多目标优化算法。以钢板弹簧结构为例,给出了动态环境下随时间变化的最优解集,为机械零部件的动态可靠性稳健优化设计提供了理论依据。

基于多目标非耦合优化策略的可靠性稳健优化设计

以实现多目标问题的可靠性稳健优化设计为目标,通过对目标函数和约束条件进行灵敏度分析,生成目标函数和约束函数的灵敏度附加项,建立了基于灵敏度附加目标函数的可靠性稳健优化设计模型;基于独立公理,使用正交试验和方差分析技术确定设计变量对各个设计目标的影响程度,将设计参数按无耦合或准耦合设计形式分组,把多目标优化问题单目标化,避免多个设计目标之间的反复权衡;结合增广乘子法,应用MATLAB的优化和符号工具箱来实现钳形盘式制动器的可靠性稳健优化设计。算例表明,提出的稳健设计方法具有较高的精度和可靠度。

汽车零部件(轴)的可靠性稳健优化设计

应用汽车零部件可靠性稳健优化设计的理论方法 ,对汽车典型轴系零部件 ,如半轴、前轴和后桥进行了可靠性稳健优化设计 ,给出了计算仿真分析结果 。

汽车零部件(弹簧)的可靠性稳健优化设计

应用汽车零部件可靠性稳健优化设计的理论方法 ,对汽车典型弹簧系零部件 ,如扭杆弹簧、螺旋弹簧和钢板弹簧进行了可靠性稳健优化设计 ,给出了计算仿真分析结果 。

机械结构动态可靠性设计的智能计算方法

针对多失效模式下机械部件动态可靠性设计问题,提出了一种Monte Carlo-时变极端学习机模型,利用该模型得到了随时间变化的载荷、强度、弹性模量、设计参数等与可靠度的显性函数表示。在此基础上建立了机械部件动态可靠性优化设计模型,并利用所提出的动态粒子群算法对模型进行求解。实验结果表明,该方法能提供整个服役期内满足可靠度要求的所有设计参数,为机械部件动态可靠性优化设计提供了一种行之有效的途径。

汽车机械式变速器多目标可靠性优化设计

以某轿车变速器为例,根据汽车动力性要求,在保证零件强度和刚度可靠性的条件下,按变速器齿轮系体积最小和传动齿轮重合度最大建立了变速器的多目标可靠性优化设计的数学模型,然后应用MATLAB优化工具箱进行联合优化设计计算。设计结果表明:该数学模型正确有效,采用多目标可靠性优化设计方法可以缩短汽车变速器的设计周期,减小其体积并改善传动平稳性。

基于改进PSO的可靠性稳健优化计算方法

基于现代设计方法和可靠性设计理论,建立了多目标约束优化数学模型,根据动态加速常数和速度自适应的改进粒子群算法(PSO),用编写的程序代码实现了数学模型的数值化求解。同时研究了加速常数和粒子速度的变化对优化计算结果的影响规律。算例表明,提出的可靠性稳健优化计算方法与传统方法相比,具有简便易行、能迅速得到结构可靠性稳健优化设计信息的优点,适合工程应用。

基于灵敏度分析的鱼雷联接结构稳健设计

工程中存在许多不确定因素或随机波动。确定性优化结果往往位于约束边界附近,随机波动容易导致设计失效。稳健设计可以保证产品使用的可靠性,同时降低操作费用。将可靠性优化设计理论与可靠性灵敏度分析方法相结合,应用可靠性稳健设计优化理论方法对鱼雷楔环联接结构进行了优化设计。此外将拉格朗日乘子引入惩罚项中,把有约束的优化问题转化为无约束优化问题。通过与确定性优化的对比,验证了所提出的优化方法具有良好的优化效果,为武器装备产品的稳健优化设计提供了理论依据。

基于模糊的多目标粒子群优化算法及应用

粒子群优化算法的思想来源于人工生命和进化计算理论,由于其容易理解、易于实现,在很多领域得到了应用。由于传统的粒子群优化算法无法对多目标优化问题进行求解,因此文中利用模糊理论中的隶属度函数和给定的最优解评估选取原则,提出了一种适合求解约束型多目标优化问题的模糊粒子群算法(FPSO)。模糊粒子群算法很好地解决了汽车零部件可靠性稳健优化设计的求解问题,仿真结果证明,该算法可行而有效,同时也拓展了粒子群算法的应用领域。