Application of particle swarm optimisation to construction planning for cable-stayed bridges by the cantilever erection method

The optimum construction planning of cable-stayed bridges using the cantilever erection method is modelled by setting the objective function as the minimisation of deviation between structural displacement upon completion and the pre-planned construction targets. The constraints on the axial forces of each cable during each erection stage are set to not exceed allowable values and the design variables of post-tensioning force of the dominated cable at each erection stage. Particle swarm optimisation (PSO) and simulated annealing (SA) in the mutation operation of a conventional genetic algorithm (GA) are integrated to improve the ability to escape a local minimum. The PSO–SA–GA is designed to work with the Midas Civil commercial software to determine variables automatically. The newly constructed SheZi Bridge in Taipei, Taiwan, was chosen as a case study and the obtained results were compared to planned results determined by the bridge contractor. The results obtained show that the method developed in this study can be applied effectively for optimum planning of cable-stayed bridges using cantilever erection.     

Integrated wind‐induced response analysis and design optimization of tall steel buildings using Micro‐GA

This paper presents an integrated procedure for wind‐induced response analysis and design optimization for rectangular steel tall buildings based on the random vibration theory and automatic least cost design optimization technique using Micro‐Genetic Algorithm (GA). The developed approach can predict wind‐induced drift and acceleration responses for serviceability design of a tall building; the technique can also provide an optimal resizing design of the building under wind loads to achieve cost‐efficient design. The empirical formulas of wind force spectra obtained from simultaneous measurements of surface pressures on various rectangular tall building models in wind tunnel tests are verified testified using a published example. Upon the known wind force spectra, the equivalent static wind loads for every storey, such as along‐wind, across‐wind and torsional loads, are then determined and applied for structural analysis including estimation of wind‐induced responses. An improved form of GAs, a Micro‐GA, is adopted to minimize the structural cost/weight of steel buildings subject to top acceleration and lateral drifts constraints with respect to the discrete design variables of steel section sizes. The application and effectiveness of the developed integrated wind‐induced response analysis and design optimization procedure is illustrated through a 30‐storey rectangular steel building example. Copyright © 2009 John Wiley & Sons, Ltd.     

An Advanced Stochastic Time‐Cost Tradeoff Analysis Based on a CPM‐Guided Genetic Algorithm

This article presents an advanced stochastic time‐cost tradeoff (ASTCT) method that performs time‐cost tradeoff analysis by identifying optimal set(s) of construction methods for activities, hence reducing the project completion time and cost simultaneously. ASTCT involves a stochastic time‐cost tradeoff analysis method based on a critical path method (CPM)‐guided genetic algorithm (GA). It makes use of CPM schedule data exported from a project management software, and alternative construction methods obtained from estimators (i.e., normal and accelerated durations and costs) for each activity. It simulates schedule networks, identifies an optimal set of GA parameters (i.e., population size, crossover rate, mutation rate, and stopping rule), implements several GA cycles, and computes near‐optimal solution(s) exhaustively. This study is of value to practitioners because ASTCT improves the computation time, reliability, and usability of existing GA‐based time‐cost tradeoff methods. The study is also of relevance to researchers because it facilitates experiments using different GA parameters expeditiously. Two test cases verify the usability and validity of the computational methods.     

基于遗传算法-神经网络混合训练技术的结构近似可靠分析方法

根据多层神经网络映射存在定理,提出了基于遗传算法-神经网络混合训练技术的结构近似可靠性分析方法,数值试验表明,该方法建立的神经网络模型可以很好地拟合真实的极限状态函数.     

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.     

土钉结构稳定验算的经验遗传–单纯形算法

针对基坑开挖的土钉支护问题,提出将经验遗传–单纯形算法应用于支护结构的稳定性验算,并与一般遗传算法的结果进行了比较。比较结果表明:本文建议的方法更有效和准确。文中还对一个具体的工程实例使用本文建议的方法进行了验算分析,并与商业软件的分析结果做了比较。结果表明:该商业软件未能搜索到最危险滑裂面,其结果对稳定性评价是偏于不安全的。此外,在土钉支护的稳定性验算过程中,一些优化程序在求解安全系数时将土层看作或是转化为均质土,而本文方法考虑了土体的分层。     

空间网格结构风振控制中的MR阻尼器数量和位置寻优

采用改进遗传算法(Genetic Algorithms,GA)研究空间网格结构风振抑制的MR阻尼器位置和数量的优化布置.构建了适用于空间网格结构的MR阻尼器位置和数量同步优化计算的适应度函数,明显提高了寻优计算速度和精度.利用谐波叠加法模拟计算模型的表面节点风速时程,并转化为节点风载序列.通过数值算例,对典型空间网壳结构的阻尼器空间位置和数量进行优化计算;采用寻优后的阻尼杆件位置和数量布置,分析结构的风振响应.最后,给出MR阻尼器位置和数量寻优的结论.     

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.     

Risk analysis of bridge falsework cuplok systems

Bridge falsework systems are one of the most common temporary structures used to support the formwork during the construction of concrete bridges. In this paper, the development of a risk analysis of selected bridge falsework structures using the Cuplok^® system is presented by means of a risk-informed structural design methodology based on newly developed structural robustness and structural fragility indices. Illustrative examples are given detailing the steps and calculations needed, including consideration of model and statistical uncertainties, and the results obtained are discussed. Furthermore, strategies for decreasing risks are presented and risks are determined for a reference (baseline) scenario and one selected alternative (improved) scenario and later evaluated against proper risk criteria. For the cases analysed, it is concluded that if the cost of the permanent structure considerably exceeds the cost of the temporary structure, which is often the case, the extent of improvements in terms of structural and economical risks may justify the extra costs incurred by implementing simple quality management procedures.     

Life cycle cost assessment of masonry structures

The objective of this study is to propose a life cycle cost (LCC) model able to assess the structural performance of masonry structures. For this purpose the proposed LCC model is used for assessing the structural behaviour of one unreinforced and three retrofitted masonry structures derived following three retrofit scenarios that are suitable for strengthening this type of structures. According to the proposed LCC model the exceedance probabilities required, are calculated by means of fragility analysis (FA). In particular, FA is applied to the unreinforced and retrofitted masonry structures and the limit-states' exceedance frequencies are obtained by convolving fragilities with hazard curve. Life-cycle cost analysis models are recognised as suitable for assessing the structural performance, especially when the structure is expected to be functional for a long period of time. For the needs of the study, linear time history analyses are performed over a large database of natural records.     

Application of evolutionary global optimization techniques in the design of RC water tanks

This paper presents evolutionary-based optimization procedures for designing conical reinforced concrete water tanks. The material cost of the tank that includes concrete, reinforcement, and formwork required for walls and floor was chosen as the objective function in the nonlinear optimization problem formulation. The wall thicknesses (at the bottom and at the top), base thickness, depth of water tank, and wall inclination were considered as design variables.Three advanced optimization techniques to solve the nonlinear constrained structural optimization problems were investigated. These methods are: (1) Shuffled Complex Evolution (SCE), (2) Simulated Annealing (SA) and Genetic Algorithm (GA). Several tests were performed to illustrate the robustness of these techniques and results were encouraging for SCE Method. The SCE method proved to be superior to the SA and GA methods in obtaining the best discovered solutions. The paper concludes that the robust search capability of SCE algorithm technique is well suited for solving the structural problem in hand.     

超高层建筑结构生命周期多维度经济成本评估及优化方法

超高层建筑结构具有结构体系复杂、结构功能多样、生命周期长、投资量大、持有人固定不变等特点,其全生命周期成本费用包含初始费用、维护费用、灾害失效费用以及拆除费用等多项费用。为了实现超高层结构全生命周期经济利益最大化而采用的生命周期经济评估方法通过方案对比、构件对比、费用项目等多维度对超高层结构成本费用进行管理。使用该方法能够在项目初期就对结构项目进行全面的评估与优化,同时,一个超高层建筑的实例将被引用来说明其有效性与适用性。     

高层混合结构中楼盖刚度对结构受力性能的影响分析

通过楼板将两种变形特性完全不同的结构体系连接而成混合结构,在受力性能上与框架结构、筒体结构既具有一定的联系,又有本质的区别。本文以一30层外部为钢框架、内部为混凝土核心筒组成的混合结构为例,采用通用有限元程序SAP2000分别计算了钢框架结构、混凝土筒体结构及混合结构,比较了三种结构体系的受力性能;通过调整楼板型式和板厚,探讨了楼板刚度对混合结构受力性能的影响。结果表明,采用混合结构使得结构变形、内力沿高度方向趋于均匀,受力性能得以改善;采用梁板体系能有效地减轻剪力滞后;随着楼板刚度的增加,结构高阶自振周期增大,侧移减少,层间剪力、楼层弯矩及总钢框架承担剪力、弯矩增加;而钢框架承担总剪力、弯矩百分比减少。     

复杂结构模型的信息集成和协同计算

通用有限元软件在处理复杂结构分析模型中,往往工程概念针对性不强且建模效率较低。根据BIM技术原理及其信息集成的内涵,以及复杂结构数据信息集成的特征,构建基于BIM技术的复杂结构信息模型基本框架,并对复杂结构模型的信息集成过程进行分析。基于BIM协同计算理念和IFC标准数据模型表达格式,设计复杂结构有限元分析模型通用转换平台,以专用于多高层建筑结构的有限元分析软件SATWE和通用有限元分析软件ABAQUS为代表,结合SATWE对复杂结构模型建模简便且符合工程概念的特点,初步开发SATWE和ABAQUS之间结构分析模型转换程序。通过上海某国际设计中心和浦东某酒店扩建工程实例应用,对转换模型4个振型的周期进行计算,并将计算结果与试验数据进行对比。结果表明,基于BIM技术的SATWE和ABAQUS模型转换程序可以提高ABAQUS针对复杂结构的建模效率,在结构协同计算中具有实用性和有效性。     

Optimal design of district heating and cooling pipe network of seawater-source heat pump

The district heating and cooling (DHC) system of a seawater-source heat pump is large system engineering. The investments and the operational cost of DHC pipe network are higher than a tradition system. Traditional design methods only satisfy the needs of the technology but dissatisfy the needs of the economy, which not only waste a mass of money but also bring problems to the operation, the maintenance and the management. So we build a least-annualized-cost global optimal mathematic model that comprises all constrict conditions. Furthermore, this model considers the variety of heating load and cooling load, the operational adjustment in different periods of the year. Genetic algorithm (GA) is used to obtain the optimal combinations of discrete diameters. Some operators of GA are selected to reduce the calculation time and obtain good calculation accuracy. This optimal method is used to the design of the DHC network of Xinghai Bay commercial district which is a real engineering. The design optimization can avoid the matter of the hydraulic unbalance of the system, enhance the running efficiency and greatly reduce the annualized-cost comparing with the traditional design method.     

偏心结构黏滞阻尼器的空间位置优化

提出了一种基于遗传算法的黏滞阻尼器空间位置优化方法,运用GATBX遗传算法工具箱编制遗传优化程序,通过编制空间三维协同弹塑性动力时程反应分析程序来对结构上设置多个黏滞阻尼器的空间位置进行优化,以控制偏心结构在多维地震作用下的扭转联耦反应。选用两种目标函数,以一个6层的偏心结构为算例,比较阻尼器的均匀布置和优化布置的结构动力响应。优化布置阻尼器可以更有效地减小最大层间位移角,使层变形趋向于均匀,采用遗传算法计算所得结构控制效果较好。     

Structural Displacement Measurement Using an Unmanned Aerial System

Vibration‐based Structural Health Monitoring (SHM) is one of the most popular solutions to assess the safety of civil infrastructure. SHM applications all begin with measuring the dynamic response of structures, but displacement measurement has been limited by the difficulty in requiring a fixed reference point, high cost, and/or low accuracy. Recently, researchers have conducted studies on vision‐based structural health monitoring, which provides noncontact and efficient measurement. However, these approaches have been limited to stationary cameras, which have the challenge of finding a location to deploy the cameras with appropriate line‐of‐sight, especially to monitor critical civil infrastructures such as bridges. The Unmanned Aerial System (UAS) can potentially overcome the limitation of finding optimal locations to deploy the camera, but existing vision‐based displacement measurement methods rely on the assumption that the camera is stationary. The displacements obtained by such methods will be a relative displacement of a structure to the camera motion, not an absolute displacement. Therefore, this article presents a framework to achieve absolute displacement of a structure from a video taken from an UAS using the following phased approach. First, a target‐free method is implemented to extract the relative structural displacement from the video. Next, the 6 degree‐of‐freedom camera motion (three translations and three rotations) is estimated by tracking the background feature points. Finally, the absolute structural displacement is recovered by combining the relative structural displacement and the camera motion. The performance of the proposed system has been validated in the laboratory using a commercial UAS. Displacement of a pinned‐connected railroad truss bridge in Rockford, IL subjected to revenue‐service traffic loading was reproduced on a hydraulic simulator, while the UAS was flown from a distance of 4.6 m (simulating the track clearance required by the Federal Railroad Administration), resulting in estimated displacements with an RMS error of 2.14 mm.     

二阶段移动边界遗传算法结构优化设计

遗传算法是一种倍受关注的计算方法 ,它在优化设计领域取得了很大的成功。但是简单遗传算法的计算效率不高 ,限制了遗传算法的进一步应用。根据自然系统的层次结构特征和遗传算法的本质并行特征 ,设计了二阶段移动边界遗传算法。算例表明 ,该算法是高效可行的。     

Spatial variability of damage and expected maintenance costsfor deteriorating RC structures

The paper develops a technique to predict life-cycle costs, using probabilistic information about the likelihood and extent of corrosion-induced cracking to reinforced concrete (RC) structures. The present paper focuses on the likelihood and extent of severe cracking as the criterion for the timing and cost of maintenance. The life-cycle cost and expected maintenance cost considers multiple repairs and various inspection intervals over the service life of the structural element. A repair cost function is also developed. Two common maintenance strategies are considered: repair and rehabilitation. It was found that for a 2% discount rate the benefits of delaying the timing of repairs outweigh the cost of increased extent of damage, for maintenance of a RC bridge deck.     

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。