改进的蚁群算法及其在桁架结构优化中的应用

蚁群算法是优化领域中的一种新型模拟进化算法,具有很强的搜索较优解的能力,其缺点是搜索时间长、容易出现停滞现象。引用局部搜索能力较强的模拟退火算法对其改进,使其跳出局部最优,发现更高质量解。并将其成功应用在25杆桁架中,结果表明,基于模拟退火的改进蚁群算法是有效可行的,是解决组合优化问题的有效方法。     

基于遗传算法钢框架抗震优化设计

采用遗传算法对钢框架结构进行了抗震优化设计,编制了分析程序,并分析了算例,证明将遗传算法运用于抗震优化设计是行之有效的,丰富了钢结构优化设计的理论和方法。     

蚁群算法在雨水管道系统优化设计中的新尝试

引入一种新的优化设计方法——蚁群算法,并探讨将该法应用于雨水管道系统的优化设计.通过实例说明蚁群算法的过程,并与遗传算法进行比较,表明蚁群算法在给排水管网设计中有较为广阔的应用前景.     

基于蚁群算法的排水管道系统优化设计

引入一种新的优化设计方法——蚁群算法，并将该法应用于排水管道系统的优化设计。通过实例说明了蚁群算法的设计过程，并与遗传算法进行了比较，结果表明蚁群算法在给排水管网设计中有较为广阔的应用前景。     

基于GASA混合优化策略的双层规划模型求解算法研究

本文提出用遗传—模拟退火算法(GASA)混合优化策略来求解双层规划模型。混合优化策略结合了遗传算法的并行结构和模拟退火算法的概率突跳性,提高了找到全局最优解的可靠性和计算效率。数值模拟实验表明算法性能良好,GASA混合优化策略求得全局最优解时的进化代数比单一的遗传算法减少约35％,比模拟退火算法的迭代次数减少约50％。     

桥梁抗震设计规范与建筑抗震设计规范的比较

对我国现行<公路工程抗震设计规范>与<建筑抗震设计规范>进行了较为详细的对比,分别从抗震设计的基本思想、设计地震动参数、地震反应分析和计算方法、构造细节等方面对这两本规范进行了比较,并指出了今后我国各行业工程结构抗震设计规范宜逐步统一.     

Multi-objective optimal design of braced frames using hybrid genetic and ant colony optimization

In this article, multi-objective optimization of braced frames is investigated using a novel hybrid algorithm. Initially, the applied evolutionary algorithms, ant colony optimization (ACO) and genetic algorithm (GA) are reviewed, followed by developing the hybrid method. A dynamic hybridization of GA and ACO is proposed as a novel hybrid method which does not appear in the literature for optimal design of steel braced frames. Not only the cross section of the beams, columns and braces are considered to be the design variables, but also the topologies of the braces are taken into account as additional design variables. The hybrid algorithm explores the whole design space for optimum solutions. Weight and maximum displacement of the structure are employed as the objective functions for multi-objective optimal design. Subsequently, using the weighted sum method (WSM), the two objective problem are converted to a single objective optimization problem and the proposed hybrid genetic ant colony algorithm (HGAC) is developed for optimal design. Assuming different combination for weight coefficients, a trade-off between the two objectives are obtained in the numerical example section. To make the final decision easier for designers, related constraint is applied to obtain practical topologies. The achieved results show the capability of HGAC to find optimal topologies and sections for the elements.     

模拟退火算法在热力管线优化设计中的应用

以管径和保温层厚度为优化变量,以初始投资和运行费用相结合的等额年费用为目标函数,建立了热力管线优化设计的数学模型。该模型是有约束的非线性规划问题,应用模拟退火算法对该模型进行了求解。计算结果表明模拟退火算法方法简单,计算速度较快,对初始点依赖性不强,计算结果合理。     

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.     

Seismic design of water distribution networks using auto-generation techniques

A feasible approach that uses an auto-generation technique is proposed to design and retrofit water distribution networks (WDNs) subjected to earthquakes. Because pipelines are laid along roads, the road information is extracted and then integrated into the auto-generation technique whereby the rules relevant to laying the pipelines are established. An optimisation model with parameters of network topology and pipeline diameter is developed to design and retrofit WDNs, whose seismic functional reliability index serves as a constraint. An intelligent optimisation program via a particle swarm algorithm is employed to generate the optimal network after a number of evaluations and evolutions. For illustrative purposes, a hypothetical and a real WDN model are investigated, respectively. Numerical results indicate that the optimisation and design method developed in this paper provides a new perspective towards the rational balance between risk and investment.     

Optimal design of urban drainage networks

In this paper, a general procedure for the optimal design of urban drainage networks is proposed taking into account realistic technical constraints and the management cost of the automatic flushing devices. The procedure, which is based on the utilisation of a standard genetic algorithm, is first tested with reference to a urban drainage network taken from the literature, while a second test case is considered in order to evaluate the impact of different input parameters and constraints on the optimisation problem. In particular, we evaluate: (i) the effect of considering the crown elevation of the network outlet not fixed a priori but variable in a given range; (ii) the effect of imposing that the size of the conduit downstream a node should be not smaller than the sizes of the conduits upstream; and (iii) the effect of modifying input parameters such as the peak wastewater discharge or the management unit costs.     

建筑抗震概念设计初探

阐述了建筑抗震概念设计的主要内容,指出在进行结构抗震设计时,应明确抗震设计的思想,灵活、恰当地运用抗震设计原则,合理地解决结构中的基本问题,做到注意总体布置大原则的同时做好关键部位的细节构造,以从根本上提高结构的抗震性能。     

浅谈建筑抗震设计的特点

针对建筑抗震工作在建筑设计与施工中的重要性,根据建筑结构抗震设计的基本要求,提出了提高抗震性能的几项措施,以使建筑结构在遭遇地震时确保具有良好的抗震能力。     

两种加筋土挡墙的动力特性比较及抗震设计建议

为分析比较条带式和包裹式加筋土挡墙的地震动力响应特征,开展了两种加筋土挡墙模型的大型振动台试验.结合震害调查的结果,发现砌块式加筋土挡墙在地震作用下的破坏模式主要表现为局部砌块的松动变形,很少会出现整体垮塌的情况.相比条带式加筋土挡墙,包裹式加筋土挡墙在地震作用下产生的变形量要小.在相同地震量级作用下,包裹式加筋土挡墙相应部位的水平加速度放大系数要小于条带式加筋土挡墙,但峰值动土压力却要比条带式加筋土挡墙大,这是因为包裹式加筋土挡墙面板在地震作用下的变形量小,对土体的约束能力强所致.因此,在抗震设防区,特别是是高地震烈度区进行加筋土挡墙的选型时,包裹式加筋土挡墙应作为一种优选结构.分析认为加筋土挡墙的抗震设计除了要进行整体稳定性的验算外,还应注重墙体变形量的控制,加筋土挡墙在地震作用下的最大变形量应小于允许的变形量.为维持线路的正常使用,加筋土挡墙的变形指数应控制在4%以内.若验算得到的变形量超出允许值,可采取增大墙后填土的压实度和增加拉筋长度,以及加厚墙体和降低墙体坡率等措施.     

Bridge retrofit prioritisation for ageing transportation networks subject to seismic hazards

The deteriorating state of highway bridges is traditionally ignored in estimating the seismic reliability of transportation networks. In this study, the present day seismic reliability of ageing bridges in highway networks is evaluated through a time-dependent seismic fragility analysis of typical bridge classes. An efficient algorithm based on finite-state Markov Chain Monte Carlo simulations is also presented to assess the reliability of large ageing highway bridge networks without the need to simplify the network topology. The criticality of ageing bridges is then assessed through different proposed ranking strategies to arrive at an optimised seismic retrofit prioritisation. A case study on an existing bridge network with 515 bridges in the state of South Carolina, USA reveals striking differences between results of the proposed ranking strategies and those from state-of-the-practice methods. Such differences emphasise the significance of accounting for network-level importance in seismic retrofit programs of ageing transportation networks.     

The directionality effect in the seismic risk assessment of highway networks

This study introduces the directionality effect of the ground motion in the probabilistic seismic risk assessment (PSRA) of lifeline systems. Given an earthquake scenario, the seismic wave strikes each component of the system with a different angle. The angle may vary significantly depending on the shape, the location and the orientation of the structure. An appropriate example of a lifeline system is a highway transportation network, in which under earthquake conditions the bridges are considered the most vulnerable components. The proposed PSRA model requires that the seismic fragility model is a function of a ground motion intensity measure (IM), as in the traditional risk analysis, and the angle of seismic incidence. The model was implemented in a new framework for the PSRA of highway transportation network. In addition, the framework includes new algorithms. One reduces the confidence interval of the results and one increases the computational efficiency. The example used is the highway transportation network serving the Los Angeles area, which has more than 3000 bridges. The results show a considerable difference in the system resilience with or without the seismic directionality taken into consideration. This is important for benefit/cost analysis and it represents a clear departure from the current risk analysis.     

脆性岩石卸围压试验与岩爆机理研究

岩爆是高地应力区地下工程开挖卸荷产生的动力现象。按照地下工程开挖卸荷特点,开展了脆性花岗岩常规三轴、不同卸载速率条件下峰前、峰后三轴卸围压试验,研究了岩石破坏的全过程并进行了声发射特征分析,探讨了岩爆岩石的变形破坏特征和岩爆形成力学机制。试验结果表明:无论是峰前还是峰后卸围压,高地应力下花岗岩都表现脆性破坏特征,峰前卸围压时岩样表现出的脆性比峰后卸围压更为强烈;卸载速率越快,岩石脆性破坏越强,发生岩爆的可能性越大。试验研究成果对地下工程岩爆发生的机理研究和预测提供了试验依据。     

高层建筑结构抗震概念设计原则探讨

详细阐述了高层建筑结构抗震概念设计原则,并就一些具体设计方法进行了探讨,通过探讨,可为工程设计人员就高层建筑结构的抗震设计积累经验,从而完善高层建筑结构设计。     

基于位移的框架结构抗震设计方法

介绍了结构抗震理论的发展历程和相关的研究理论,着重以基于位移的抗震设计理论为基点,给出了实现“三水准”的两阶段设计方法,实践证明：这种设计方法遵照国家的建筑设计规范,计算简单,可以在工程中得到广泛推广。     

多目标遗传算法用于给水管网优化设计的研究

建立了一个基于经济性和可靠性的多目标数学模型用于给水管网优化设计。利用惩罚函数法对遗传算法进行改进后,应用其对多目标数学模型进行求解,并将该优化方法运用于实际工程。结果表明,采用多目标遗传算法得出的结果优于常规优化方法。