基于遗传算法的偏心支撑结构优化

提出一种遗传算法,确定偏心支撑结构中的最佳连接点及最大侧向屈曲荷载。这种支撑结构常用于地震区,可给予建筑师更多的设计空间。通过非对角线杆件对结构施加偏心,并通过第3根杆件与框架角点相连。设计这种结构时,常反复试验以确定支撑杆件连接点位置,考虑各种参数,如:开口和框架尺寸、支撑杆件的横截面面积及支撑杆件连接点位置。采用传统方法,通过最大侧向屈曲荷载来确定最佳连接点是很难的。以不同框架为例,证明遗传算法的有效性。     

Genetic algorithm in locating the optimum mid-connection of Off-Centre braced system

In this article, a particular Off-Centre braced system is examined. This bracing system consists of three members, where the diagonal member is not straight and it is connected to the corner of the frame by a third member. The out-of-straightness of the diagonal member introduces eccentricity to the system. This system improves the energy dissipation due to earthquake as well as its eccentricity allows architects to have more openings in the panel areas. In this regard, the location of brace elements connection point has significant effect on the stiffness of the system. In order to assess the influence of the connection position and other parameters such as cross section of brace elements and span/height ratio of the braced frame on the stiffness of the system, analytical equations have been developed. A new method based on Genetic algorithm (GA) to obtain the connection point is also proposed. The importance of elite individuals together with selection, mutation and crossover operator between populations are also examined. In order to achieve the best and practical location of the connection point, two equations for boundary conditions with regards to the opening dimensions are set in a computer model developed in MATLAB program. The results indicate that the stiffness decreases as the connection point moves closer to the corner of the frame. Additionally, the proposed method is proven to be efficient in determining the connection point due to its accuracy and minimal computational time required compare to conventional trial and error method.     

Cyclic performance of steel and composite bracing members

This paper describes an experimental study on the response of hollow and filled steel members to monotonic and cyclic axial loading. Monotonic tests were first performed on short specimens to establish their compressive and tensile axial resistances and to investigate the effect of infill on local buckling and ductility. These were followed by cyclic tests on longer bracing members with three different cross-section sizes. The presence of concrete infill was observed to influence the mode of failure displayed by the specimens, as well as their compression and tension load responses. The ductility capacities of the individual specimens are compared, and the effects of slenderness, steel strength and infill are quantified. The experimental findings are compared with the recommendations of a number of international codes of practice and previous research studies on the seismic response of steel braces. It is found that the infill contributes to the compression resistance of the brace, even after multiple inelastic load reversals, and that it can improve ductility capacity by preventing or limiting local buckling.     

Rehabilitation of RC frame joints using local steel bracing

Reinforced concrete (RC) structural frames that were built prior to the 1970s generally do not meet current design code requirements and may behave in a non-ductile manner. The lateral load carrying capacity of these structures is often insufficient due to non-ductile reinforcement detailing, which includes insufficient or no beam-column joint transverse reinforcement and inadequate anchorage for the beam's bottom reinforcement. Experience shows that such frames are prone to earthquake damage and often suffer shear and bond slip non-ductile modes of failure. Recent earthquakes have demonstrated that the beam-column joint safety is an important factor in keeping the integrity of the entire structure. Concentric steel bracing systems have been used for the rehabilitation of non-ductile RC buildings in a number of countries. However, the application of eccentric (local) steel bracing in the rehabilitation of RC structures still lags behind due to the limited research and information on the design, modelling and behaviour of such a combined concrete-steel system. In this paper a new beam-column joint rehabilitation technique using local steel brace members is proposed. Two full-scale specimens representing a standard joint and a rehabilitated joint were made and tested under reversed cyclic load. Their behaviour was compared to that of a non-rehabilitated specimen. It is shown that the rehabilitation technique was successful in enhancing the overall performance of the deficient joint and upgrading it towards a close to current standard performance.     

遗传渐进结构优化法

渐进结构优化法（ESO）是基于一个简单概念提出的一种方法,即可以通过在设计上逐渐消除无效材料而实现最优化结构（具有最大刚度和最轻重量）。一般而言,ESO的结果很可能是局部最优化,而不是整体最优化。将遗传算法（GA）与ESO相结合,形成一种新的算法,即遗传渐进结构优化法（GESO）,考虑了GA在整体优化计算方面的优势。     

结构优化设计中自适应遗传算法的研究

主要介绍了一种基于非连续设计变量的结构优化设计方法一遗传算法(Genetic Al-gorithms，GA)。首先对遗传算法的来源、基本过程进行了论述；为了提高遗传算法的收敛性能，同时考虑到交叉率和变异率的选取问题，引入一种基于个体适应度值的自适应调整交叉率和变异率的自适应遗传算法，并通过算例表明自适应遗传算法是有效的。     

桁架尺寸、几何形状和拓扑优化的力法和遗传算法

结合能量和力法进行桁架重量的最小化,为此,采用遗传算法作为优化工具。提出的主要思想是减少输入变量。在采用遗传算法进行结构优化时,力法的引入非常有意义。该方法不需要求逆矩阵,只需在遗传算法中加入有限的变量,变量的个数等于结构超静定次数。通过几种不同类型的优化案例,验证了当前方法的有效性,并对不同优化技术的结果进行了比较。     

Sensitivity analysis of critical forces of trusses with side bracing

The present research is devoted to the study of out-of-plane buckling of trusses with elastic side bracing. In this paper, a sensitivity analysis of critical buckling loads of a truss due to bracing stiffness is carried out. A method based on the sensitivity analysis for the determination of the threshold bracing stiffness condition for full bracing of a truss is proposed. The influence lines of the unit change of the bracing stiffness on the buckling load, for different initial bracing stiffness, are investigated. The approximations of an exact relation between the buckling load and bracing stiffness are found. The buckling length related to the side-support distance as a function of bracing stiffness is also determined. It is shown that the buckling length of truss chords with elastic side supports is larger than that assumed in design codes.     

基于遗传算法的城市燃气管网优化

建立了城市燃气管网优化模型,将遗传算法应用于管网优化模型,算例所得结果表明遗传算法优于传统算法。     

基于遗传算法的枝状燃气管网布局优化

以图论和遗传算法为理论基础,以管网造价最小为优化目标,提出枝状燃气管网遗传布局优化的方法,并针对枝状管网的特点,对基本遗传算法进行改进。改进后的遗传算法能够获得造价最小的布置方案,算法寻优效率较高。     

工程实用的遗传算法结构优化设计

针对工程结构设计的特点以及目前遗传算法在大规模设计变量设计中的计算量大、优化结果较差的特点,提出了相应的改进措施,算例表明改进方法是有效的。     

采用遗传算法对蜗杆-行星减速器进行优化设计

蜗杆-行星减速器的传动比大,适用于低速重载场合,但优化模型复杂。采用遗传算法,以总体积最小为目标函数,建立了优化设计的数学模型,得到全局最优点。以某履带行走装置为例进行优化,得到合理的设计方案。     

基于退火遗传算法的给水管网优化

给水管网优化设计的难点在于如何处理约束条件，采用较多的是遗传算法中的罚函数法，但其罚系数的选择较繁琐。故提出采用不可行度的概念来处理约束条件，然后应用退火遗传算法进行优化计算。为了缩短算法的计算时间，可在编程上进行一定的加速处理。与其他优化方法相比，该算法具有收敛速度快、精度高的优点，并在四川某市的给水管网扩建工程中得到了成功应用，取得了良好的经济效益和社会效益。     

用遗传算法实现污水管网的优化设计

提出用遗传算法优化大中型污水管网的设计,并与节点递归算法相结合,既满足了污水管网系统内部节点的水力衔接,也保证了管网系统的全局优化。遗传算法具有只需目标函数值而无需导数等信息的优点,并能从全局出发对管网水力参数进行优化,达到费用最低的目标。结合中型污水管网的优化设计,确定了遗传算法的运行参数。     

基于遗传算法的绿色建筑优化设计

建筑师在实际运用建筑节能设计标准过程中感觉标准较复杂、不方便。将遗传算法在多目标优化设计中的优势与建筑能耗仿真软件结合起来,建立一套绿色建筑优化设计方法或模型。以武汉地区住宅建筑为例,在最低能耗与最低成本的目标控制下,同时,优化设计建筑朝向、窗墙比、外墙构造、屋面构造、采暖温度设定点、空调温度设定点、遮阳系数、窗户玻璃类型的组合因素。将优化结果与现有绿色节能建筑设计规范进行对比,给出了绿色建筑设计中部分参数的新的参考值。     

深基坑支护工程遗传优化设计算法

探讨了深基坑支护工程设计同混合遗传算法结合的可能性,提出一种混合遗传优化算法设计方法应用于深基坑支护工程设计,给出相应结论。     

卵形消化池内力分析及基于遗传算法的形状优化

本文以静水压力作用下卵形消化池壳体的薄膜内力为基础 ,建立以体表面积为目标函数 ,以容积、高度 ,应力等为约束条件的优化模型。使用遗传算法对以上模型进行优化 ,并引进动态罚函数和对约束条件不断逼近的方法处理约束条件。从而为初步设计阶段卵形消化池形状的设计提供了建议和参数。     

Buckling of frames braced by flexural bracing

This paper investigates the buckling of multistory frames braced by vertical beams. The sectional properties of the frames and the bracing beam are assumed to vary linearly along the height; the axial forces in the columns and the bracing beam are also assumed to linearly change along the height. A relationship between the buckling load and the bracing rigidity is established. The threshold rigidity for the vertical bracing beam which is just enough to make the frames buckle in a non-sway mode is obtained. The result may be used as a rational basis for classifying sway frames and non-sway frames after taking the influence of initial imperfections and lateral loads into account.     

深基坑支护结构支撑系统简化空间分析方法的研究

提出了一种考虑土压力随支护体位移变化、支撑力随支撑点处位移变化和土-支护结构-支撑系统相互作用的深基坑支护结构支撑系统简化空间分析方法 ,编制了分析计算程序 ,该方法能够用于分析相同开挖深度、不同开挖深度及土质不均等情况下支护结构、支撑系统内力、变形的计算     

Displacement-restraint bracing for seismic retrofit of steel moment frames

This paper presents a seismic retrofit method using wire rope (cable) bracing for steel moment-resisting frames. The retrofitted frame using the proposed bracing system exhibits ductile behavior and maintains seismic energy dissipation capacity to the same extent as the original bare frame. The bracing member does not act for small and medium vibration amplitudes. For large vibration amplitudes, the bracing member acts and restrains unacceptably large story drift. This retrofit method prevents an increase in the column compression force resulting from the brace action. Cyclic loading test results of the portal frames reveal fundamental characteristics of the proposed bracing system. Seismic response analyses are also conducted for the three-story moment-resisting frames. The effectiveness of the retrofit method is discussed in light of these test and analysis results.