Hybrid of genetic algorithm and simulated annealing for multiple project scheduling with multiple resource constraints

Since scheduling of multiple projects is a complex and time-consuming task, a large number of heuristic rules have been proposed by researchers for such problems. However, each of these rules is usually appropriate for only one specific type of problem. In view of this, a hybrid of genetic algorithm and simulated annealing (GA-SA Hybrid) is proposed in this paper for generic multi-project scheduling problems with multiple resource constraints. The proposed GA-SA Hybrid is compared to the modified simulated annealing method (MSA), which is more powerful than genetic algorithm (GA) and simulated annealing (SA). As both GA and SA are generic search methods, the GA-SA Hybrid is also a generic search method. The random-search feature of GA, SA and GA-SA Hybrid makes them applicable to almost all kinds of optimization problems. In general, these methods are more effective than most heuristic rules. Three test projects and three real projects are presented to show the advantage of the proposed GA-SA Hybrid method. It can be seen that GA-SA Hybrid has better performance than GA, SA, MSA, and some most popular heuristic methods.     

钢筋混凝土圆形水池的结构优化

以结构造价为目标函数，探讨了钢筋混凝土圆形水池的优化问题，提出了池径和池高一定时池壁厚度优化的数学模型和求解方法，并以一地上式开口圆池为例说明了优化过程及效果。     

Performance-based seismic design of steel frames using ant colony optimization

In this paper, a performance-based optimal seismic design of frame structures is presented using the ant colony optimization (ACO) method. This discrete metaheuristic algorithm leads to a significant improvement in consistency and computational efficiency compared to other evolutionary methods. A nonlinear analysis is utilized to arrive at the structural response at various seismic performance levels, employing a simple computer-based method for push-over analysis which accounts for first-order elastic and second-order geometric stiffness properties. Two examples are presented to illustrate the capabilities of ACO in designing lightweight frames, satisfying multiple performance levels of seismic design constraints for steel moment frame buildings, and a comparison is made with a standard genetic algorithm (GA) implementation to show the superiority of ACO for the discussed optimization problem.     

Hybrid Meta-Heuristic Algorithm for the Simultaneous Optimization of the O–D Trip Matrix Estimation

Abstract:   In the present article, the origin–destination (O–D) trip matrix estimation is formulated as a simultaneous optimization problem and is resolved by employing three different meta-heuristic optimization algorithms. These include a genetic algorithm (GA), a simulated annealing (SA) algorithm, and a hybrid algorithm (GASA) based on the combination of GA and SA. The computational performance of the three algorithms is evaluated and compared by implementing them on a realistic urban road network. The results of the simulation tests demonstrate that SA and GASA produce a more accurate final solution than GA, whereas GASA shows a superior convergence rate, that is, faster improvement from the initial solution, in comparison to SA and GA. In addition, GASA produces a final solution that is more robust and less dependent on the initial demand pattern, in comparison to that obtained from a greedy search algorithm.     

海洋混凝土储油罐壁的热应力分析

在我国渤海海域 ,冬季海水温度较低 ,而原油进砼罐时温度较高 ,罐体内外温差将会引起较大的温度应力。混凝土罐壁能否承受如此大的温度应力 ,是关系到混凝土平台能否应用于渤海油田的关键性问题。本文通过有限元分析 ,对罐壁在不同变温情况下的应力状态进行了研究 ,并根据罐壁与变温前后的顶底板的组合分析 ,讨论了由变温引起的内在约束对外环壁受力状态的影响 ,并与试验结果进行了对比 ,符合较好     

基于遗传算法的单向调压塔尺寸优化研究

介绍了单向调压塔水锤防护的工作原理及计算模型,对单向调压塔水锤防护效果的主要影响因素进行了分析。采用反问题分析方法,以单向调压塔直径、有效水深、补水管直径及水泵出口阀的关闭参数作为决策变量,以单向调压塔的容积最小作为目标函数,建立了单向调压塔尺寸和水泵出口阀关闭程序同时优化的数学模型,并采用改进遗传算法对优化模型进行求解。该优化模型和优化方法在实际工程中的应用表明,数值模拟结果较准确,由此确定的防护措施可靠。     

A comparative study on optimization of constrained layer damping treatment for structural vibration control

This paper presents a comparison of optimization algorithms for constrained layer damping (CLD) patches’ layout with an objective to minimize the maximum vibration response of the odd modes, which constitutes the dominant acoustic radiation, of a simply supported beam excited by a harmonic transverse force. An analytical model developed for relating the displacement response of the beam with bonded CLD patches and their layout is adopted to formulate the optimization problem. Four different nonlinear optimization methods/algorithms, sub-problem approximation method, the first-order method, sequential quadratic programming (SQP) and genetic algorithm (GA), are then, respectively, used to optimize the CLD patches’ locations and lengths with the aim of minimum displacement amplitude at the middle beam. The efficiency of each considered optimization method is evaluated and also compared in terms of obtained optimal beam displacement and the added weight owing to damping treatment. The results show that GA is most efficient in obtaining the best optimum for this optimization problem in spite of highest computation efforts required to improve its stability.     

Fluid transients and pipeline optimization using GA and PSO: the diameter connection

This paper describes the optimal selection of pipe diameters in a network considering steady state and transient analysis in water distribution systems. Two evolutionary approaches, namely genetic algorithms (GA) and particle swarm optimization (PSO), are used as optimization methods to obtain pipe diameters. Both optimization programs, inspired by natural evolution and adaptation, show excellent performance for solving moderately complex real-world problems which are highly nonlinear and demanding. The case study shows that the integration of GA or PSO with a transient analysis technique can improve the search for effective and economical hydraulic protection strategies. This study also shows that not only is the selection of pipe diameters crucially sensitive for the surge protection strategies but also that more global systematic approaches should be involved in water distribution system design, preferably at an early stage in the design process.     

钢筋混凝土圆形水池裂缝分析与处理

本文针对某钢筋混凝土圆形水池在使用过程中出现的裂缝进行计算和分析，讨论了温度对水池的影响，特别是考虑储水区与非储水区存在温差的条件对水池池壁裂缝的影响，并提出处理方案。     

Optimization of Mediterranean building design using genetic algorithms

While it is possible to check the energy performance of a given building by means of several available methods, the inverse problem of determining the optimum configuration given a desired performance is more difficult to solve. In the Mediterranean region this problem is more complex due to the following two reasons: the air-conditioning load is as important as the heating load, and the energy needs depend on a high number of architectural parameters which have different, even contradictory, effects on summer and winter loads. In this paper we present an optimization algorithm that couples pseudo-random optimization techniques, the genetic algorithms (GA), with a simplified tool for building thermal evaluation (CHEOPS) for the purpose of minimizing the energy consumption of Mediterranean buildings. Since increasing the energy performance usually requires the use of special devices resulting in a high construction cost, we also propose to use GA for the purpose of economical optimization.     

New improved metaheuristic approaches for optimum design of posttensioned axially symmetric cylindrical reinforced concrete walls

Two novel hybrid approaches are presented for optimum design of axially symmetric cylindrical walls subjected to posttensioning loads using metaheuristic algorithms such as harmony search (HS), flower pollination algorithm (FPA), and teaching learning based optimization (TLBO). The objective function of the optimization problem is to minimize the total cost of the wall subjected to constraints on the basis of sectional capacities (bending moment, shear force, and axial tension), ACI 318 (building code requirements for structural concrete) requirements and design variables such as wall thickness, compressive strength of concrete, location and intensities of posttensioning cables, size, and spacing of reinforcement. In the optimum design, the performance of the iterative population based metaheuristic algorithms, HS, FPA, and TLBO are compared and tested by taking wall thickness as discrete and continuous variable. In order to improve the efficiency on finding global optimum results, hybrid forms of the HS combined with FPA and TLBO are effective for the optimization problem.     

环向预应力筋分布对预应力圆形水池应力的影响

为配合预应力混凝土圆形水池技术规程的编制,现利用大型有限元分析软件ANSYS研究环向预应力筋的分布对预应力混凝土圆形水池池壁应力分布的影响,探讨预应力筋最大间距与池壁厚度关系.     

Predicting the capacity of perfobond rib shear connector using an ANN model and GSA method

Due to recent advances in the field of artificial neural networks (ANN) and the global sensitivity analysis (GSA) method, the application of these techniques in structural analysis has become feasible. A connector is an important part of a composite beam, and its shear strength can have a significant impact on structural design. In this paper, the shear performance of perfobond rib shear connectors (PRSCs) is predicted based on the back propagation (BP) ANN model, the Genetic Algorithm (GA) method and GSA method. A database was created using push-out test test and related references, where the input variables were based on different empirical formulas and the output variables were the corresponding shear strengths. The results predicted by the ANN models and empirical equations were compared, and the factors affecting shear strength were examined by the GSA method. The results show that the use of ANN model optimization by GA method has fewer errors compared to the empirical equations. Furthermore, penetrating reinforcement has the greatest sensitivity to shear performance, while the bonding force between steel plate and concrete has the least sensitivity to shear strength.     

Optimal design of double-layer barrel vaults using genetic and pattern search algorithms and optimized neural network as surrogate model

This paper presents a combined method based on optimized neural networks and optimization algorithms to solve structural optimization problems. The main idea is to utilize an optimized artificial neural network (OANN) as a surrogate model to reduce the number of computations for structural analysis. First, the OANN is trained appropriately. Subsequently, the main optimization problem is solved using the OANN and a population-based algorithm. The algorithms considered in this step are the arithmetic optimization algorithm (AOA) and genetic algorithm (GA). Finally, the abovementioned problem is solved using the optimal point obtained from the previous step and the pattern search (PS) algorithm. To evaluate the performance of the proposed method, two numerical examples are considered. In the first example, the performance of two algorithms, OANN + AOA + PS and OANN + GA + PS, is investigated. Using the GA reduces the elapsed time by approximately 50% compared with using the AOA. Results show that both the OANN + GA + PS and OANN + AOA + PS algorithms perform well in solving structural optimization problems and achieve the same optimal design. However, the OANN + GA + PS algorithm requires significantly fewer function evaluations to achieve the same accuracy as the OANN + AOA + PS algorithm.     

遗传算法和高斯牛顿法联合反演地下水渗流模型参数

充分利用遗传算法善于进行全局搜索和高斯牛顿法善于进行局部搜索的优点,克服了两种方法各自的不足,用改进的遗传算法和高斯牛顿法联合反演地下水数值模型参数,首先用遗传算法求出地下水模型参数的初值,然后利用这组初值用高斯牛顿法进行数值模型参数的反演,并以非均质各向同性承压二维非稳定流动模型,结合有限元法讨论了用遗传算法和高斯牛顿法联合反演地下水数值模型参数的过程。计算结果表明,联合参数反演方法,具有收敛速度快、解的精度高的特点。     

有中心支柱圆形清水池结构电算方法

本文重点介绍有中心支柱圆形钢筋混凝土清水池结构内力计算的电算方法。从而根本上解决了此类水池靠查内力系数表计算内力的繁重而有误差的工作。减轻了计算工作强度,提高了计算精度。     

基于附加质量法的水与水池壁板动力相互作用分析

用于储存清水、污水等液体的钢筋混凝土矩形水池结构广泛应用于给水、排水等工业企业。在这类结构的抗震设计中,液动压力是一项主要的地震作用。基于Westergaard附加质量法考虑水平地震动下池中液体与水池结构的相互作用,对矩形水池的壁板进行了多遇地震作用下的有限元时程分析。对比了地震荷载作用下考虑液动压力与不考虑液动压力对水池壁板弯矩、剪力的影响,并与规范方法进行了对比。结果表明,考虑液动压力的附加质量法与规范方法的内力结果明显大于不考虑液动压力的计算结果,说明了考虑液体-结构动力相互作用的合理性。在设计中应当考虑水平地震动引起的动水压力对池壁的影响,初步得出了附加质量模型动力时程分析的基本规律。     

Generalized SDOF system for seismic analysis of concrete rectangular liquid storage tanks

This paper presents a simplified method using the generalized single degree of freedom (SDOF) system for seismic analysis and design of concrete rectangular liquid storage tanks. In most of the current design codes and standards for concrete liquid storage tanks, the response of liquid and tank structures is determined using rigid boundary conditions for the determination of hydrodynamic pressures. Also, the lumped mass approach is used for dynamic analysis. However, it has been shown that the flexibility of a tank wall increases the hydrodynamic pressures as compared to the rigid wall assumption. On the other hand, the consistent mass approach reduces the response of liquid containing structures as compared to the lumped mass approach. In the proposed method, the consistent mass approach and the effect of flexibility of a tank wall on hydrodynamic pressures are considered. The prescribed vibration shape functions representing the first five mode shapes for the cantilever wall boundary condition are studied. The application of the proposed shape functions and their validity are examined using two different case studies including a tall and a shallow tank. The results are then compared with those using the finite element method from a previous investigation and ACI 350.3 commonly used in current practice. The results indicate that the proposed method is fairly accurate which can be used in the structural design of liquid containing structures. It is also concluded that the effect of the second mode should also be considered in the dynamic analysis of liquid containing structures.     

圆柱形预应力混凝土污泥消化池的受力分析

为研究圆柱形预应力混凝土污泥消化池的应力变化情况，对某污水处理厂污泥消化池进行了施加预应力阶段和试水阶段的原型监测试验，并采用三维有限元方法进行了分析计算。结果表明：三维有限元方法的计算值和原型检测结果符合良好，池壁混凝土在预应力作用下沿高度和环向的应力分布规律与内水荷载作用下沿高度和环向的应力分布规律相同，但拉、压应力方向相反；在施加预应力阶段及使用期，池壁混凝土局部存在的拉应力值在设计允许的范围内，在满水闲气试验中池壁混凝土基本处于受环向和竖向压应力状态。此外，还对影响池壁混凝土应力分布均匀性的主要因素进行了分析。     

钢储罐环墙基础裂缝分析

通过对某大型项目4台钢储罐基础环墙充水试压后产生不同程度的裂缝进行分析,介绍了可能产生裂缝的原因,并结合钢储罐环墙基础的设计以及钢筋混凝土环墙受力分析,对钢储罐环墙基础提出设计建议,从而有效减少钢储罐环墙基础裂缝的产生。