Fuzzy optimization of cold-formed steel sheeting using genetic algorithms

In this paper, genetic algorithms are applied for optimization of dimensions of cold-formed steel trapezoidal sheeting. The objective of the optimization is to obtain the minimum weight subjected to the given constraints in accordance with Eurocode 3, Part 1.3. In traditional optimization, these constraints are defined with crisp number. However, in practical engineering, constraints with a small certain percentage of violation can be acceptable. Thus, in this research, sheeting is optimized to satisfy the constraints considering the fuzziness so that the optimization is more practical from the engineering point of view. The better performance of introducing the fuzziness into a constraints-handling technique has been demonstrated with a design example.     

Lifetime-oriented multi-objective optimization of structural maintenance considering system reliability, redundancy and life-cycle cost using GA

The need to design and construct structural systems with adequate levels of reliability and redundancy is widely acknowledged. It is as crucial that these desired levels are maintained above target levels throughout the life of the structure. Optimization has served well in providing safer and more economical maintenance strategies. Lifetime maintenance optimization based on system reliability has already been proposed. It is still needed, however, to incorporate redundancy in the lifetime maintenance optimization process. Treating both system reliability and redundancy as criteria in the lifetime optimization process can be highly rewarding. The complexity of the process, however, requires the automation of solving the optimization problem. Genetic algorithms (GAs) are used in this study to obtain solutions to the multi-objective optimization problems considering system reliability, redundancy and life-cycle cost (LCC). An approach to provide the optimization program the ability to optimally select what maintenance actions are applied, when they are applied, and to which structural components they are applied is presented. Two different strategies are proposed. The first strategy has the ability to optimally select mixed maintenance types to apply to different parts of the structure at the same time. This strategy can be used in cases where any combination of different maintenance options can be practically applied to any part of the structure. The application of this strategy on truss structures is shown in a numerical example. The second strategy can be used when a limited number of possibilities of practical maintenance options are available. The application of this strategy to bridge structures is shown in a numerical example. The greatest advantage of the proposed approach (both strategies) is its ability to avoid the application of maintenance interventions to structural components that are not critical.     

基于遗传算法和BP网络的岩爆预测

选取影响岩爆的一些关键指标,例如脆性系数、弹性应变能指数、应力强度比等作为输入参数,采用经遗传算法优化过的BP网络,对岩爆的发生及其烈度进行了预测.针对国内外一些地下工程的实例进行了分析计算,预测结果与实际情况是符合的,说明这种方法有一定的实际意义.     

Predicting the risk of contractor default in Saudi Arabia utilizing artificial neural network (ANN) and genetic algorithm (GA) techniques

The construction project is subject to several risks, one of the most important of which is contractor default because contractor default may increase the final project cost considerably. In the US construction industry, owners commonly shield themselves from the risk of contractor default by transferring this risk to the contractor, who in turn transfers this risk to a surety company. On the other hand, the General Directorate of Military Works (GDMW) of the Kingdom of Saudi Arabia retains the risk of contractor default rather than transferring it to a third party. An artificial neural network (ANN) and a genetic algorithm (GA) are used in this study to predict the risk of contractor default in construction projects undertaken for the Saudi armed forces. Based on this prediction, the Saudi GDMW can make a decision to engage or not to engage the services of a contractor. In case the models are not able to generate reliable predictions (or generate contradictory outcomes), the GDMW will have to augment its budget with contingency funds to be used in the event of contractor default. The outcome of this study is of particular relevance to construction owners because it proposes an approach that can allow them to replace an indiscriminate blanket policy by a policy that is rational, effective, prudent and economical.     

基于改进PSO-BP神经网络的冰蓄冷空调冷负荷动态预测模型

当前多数冰蓄冷空调冷负荷动态预测方法中,由于模型输入变量与输出结果相关性差、信息冗余度高等原因,导致多数预测模型在预测精度和收敛速度方面都未达到理想的预测效果,因此,提出一种改进的PSO-BP神经网络算法预测大型公共建筑的冷负荷。对于输入变量与输出结果采用灰色关联度分析,消除样本输入变量对数的耦合性,确定影响冰蓄冷空调系统冷负荷的关键性因素,将其作为输入变量,预测冰蓄冷空调系统动态冷负荷。结果表明：T时刻室外空气温度、T-1 h时刻室外空气温度、T时刻室外空气湿度、T时刻太阳辐射强度、T-1 h时刻太阳辐射强度、T-1 h时刻空调冷负荷是影响T时刻冰蓄冷空调系统冷负荷的关键因素,并以此作为预测模型的输入变量。相对于传统PSO-BP神经网络全输入变量预测算法,该模型预测结果精确度更高、收敛速度更快。     

浅谈混凝土结构工程修复加固技术

在过去的50多年间,我国的土木工程建设发展极为迅猛.建筑物和构筑物建造、使用中出现的质量、维护问题,及其老龄化问题,引起人们的高度关注和重视,各种修补加固方法也不断出现,笔者根据自身的施工经验,对钢筋混凝土结构的加固施工中所遇到的加固施工方案及施工方法进行简单的介绍,并对不同方案进行优化比较.     

大桥混凝土徐变控制研究及预测

混凝土收缩、徐变的控制和准确预测在世界范围内一直是个难题。论文针对已建高速铁路特大跨预应力混凝土连续梁徐变变形进行深入研究,讨论了混凝土收缩与徐变引起的构件预应力损失,并用数值方法分析构件预应力损失后的力学变化。解决了以往由于没有实测数据作参考而造成预测不准确的问题。     

设计变更方案比选与造价控制

本文通过对局部设计变更方案的优化与比选实例,探讨工程设计变更造价控制的一些做法。     

The optimal cut of sheet metal belts into pieces of given dimensions

The problem of the optimal cut of belts into pieces of given dimensions is resolved using dynamic programming and the genetic algorithm. When using dynamic programming, our basic problem is how to fill the knapsack in the optimal way. We use the solution to this problem to design an algorithm for the optimal cut of the belts into pieces. This problem is also dealt with by applying the genetic algorithm. The dynamic programming and genetic algorithm, the two methods of solving the problem of the optimal cut of belts, are compared and their space and time requirements are determined.     

依托数字化建设优化医院工作流程

当前,医院数字化和信息化正成为现代化医院建设中的热点。本文分析了医院数字化建设和医院工作流程优化的辩证关系,探讨了依托数字化建设优化医院工作流程的一些基本原则和实施要点,并通过一些实例论证了优化工作流程所达到的提升诊疗质量和管理水平的效果。     

城市微气候环境控制及优化的国际经验及启示

城市快速发展进程中大规模的城市建设和更新改造引发的城市微气候环境质量下降问题极大地影响了城市环境的宜居性以及城市生活质量。本文分析城市微气候环境与空间环境的相互影响以及城市微气候环境控制及优化的意义,在此基础上总结分析城市微气候环境控制及优化方面的国际经验,包括开展专项规划研究、重视城市设计管理、推行适宜建设技术等,以期对中国城市建设有所启示。     

浅谈钢结构深化设计与工程成本节约控制

钢结构图纸深化设计是钢结构工程技术一项重要的工作,它并非仅仅是对设计图纸的简单解剖,它直接影响着钢结构工程的安装、运输、施工质量和工程成本。文章以正在施工的国外某电厂项目为例,从分析设计要求、优化设计、细化施工方案等方面,探讨了通过钢结构图纸深化设计实现工程成本控制和节约的途径和方法,提出了强化设计人员业务素质、注重钢结构细节设计、加强深化设计阶段管理等措施,为提高钢结构施工的经济性提供了有力的参考和借鉴。     

桥梁施工安全事故流变-突变规律

结合桥梁施工事故的特点,通过对流变突变理论的桥梁施工安全事故规律研究,绘制出桥梁施工安全事故流变规律曲线。建立了桥梁施工安全事故流变突变数学模型,基于该数学模型采用数学软件MATLAB分析了事故致因与流变突变曲线的关系。对该数学模型进行假设性验证分析,得到起始安全度和衰减系数对事故时间的影响。通过支架结构的施工期变形的监测数据和某次支架坍塌事故实例验证流变突变数学模型是合理的。     

山西2005预算定额与2011预算定额测算对比分析

通过工程项目实例对《山西省2005预算定额》与《山西省2011预算定额》进行了测算、对比,分析出一些数据结果,以期指导在新旧定额交替之际,投标及签订合同时能正确决策,保证企业最大合理利润。     

重庆市主城区住房售租分异格局及影响因素

当前“租购同权”成为全国热点话题背景下,中国多数城市住房售价与租金价格存在明显的比例差异和空间差异,“租购同权”改革推进存在较多盲区和障碍,探讨重庆市主城区住房销售价格与租赁价格的空间分异格局及其影响因素,对于认识山地城市住房价格与租金空间差异、推进租购同权改革具有重要理论和实践价值。本研究利用重庆市主城区二手普通商品房住宅小区的住房销售价格和租赁价格数据,采用空间趋势面分析等地理空间分析方法,研究重庆市主城区住房销售价格与租赁价格的空间分异格局及影响因素。研究发现：第一,重庆市主城区住房销售价格和租赁价格在空间上均呈现“中间高、两边低”的特点,但住房租赁价格的空间分异性更弱。第二,重庆市主城区住房销售价格的热点区集中在嘉陵江段、中心城区北部区域,而冷点主要分散在外围地区。住房租赁价格的冷热点分布格局与其一致,但范围更小,且没有滨江特点。第三,重庆市主城区住房销售价格在空间上总体呈现中心—外围模式扩展,住房租赁价格则呈现多中心扩展的特点。第四,从影响因素来看,区位因素（主要是到中心商务区的距离、到地铁站点距离）、社会属性因素（主要是到最近医院距离、到最近幼儿园的距离、到最近小学的距离）和自然因素（到江的距离）是对重庆住房销售价格和住房租赁价格产生主要显著影响的因素。其中,对住房销售价格影响力由大到小为到中心商务区的距离、到地铁站点距离、到最近医院距离、到江的距离、到最近幼儿园的距离、到最近小学的距离;住房租赁价格的影响因素贡献度由大到小为到地铁站点距离、到中心商务区的距离、到最近购物中心的距离、到江的距离,且影响性质和影响程度存在明显空间差异。     

Shape optimization of cold-formed steel columns

The objective of this paper is to demonstrate the application of formal optimization tools towards maximizing the compressive strength of an open cold-formed steel cross section. In addition, in the work presented here the cross section shape is not limited by pre-determined elements (flanges, webs, stiffeners, etc.), as is commonly required to meet the necessity of conventional code-based procedures for design that employ simplified closed-form stability analysis. Instead, by utilizing the finite strip method for stability analysis and the Direct Strength Method for the strength calculation, the full solution space of cold-formed steel shapes may be explored. In the analysis herein, a given width of sheet steel is allowed to be bent at 20 locations along its width, thus providing the ability to form nearly any possible shape. Three optimization algorithms are explored: the gradient-based steepest descent method and two stochastic search methods, genetic algorithms and simulated annealing. Compared with a standard cold-formed steel lipped channel the final optimized capacities are found to be more than double the original design. Steepest descent solutions are shown (as expected) to be highly sensitive to the initial guess, but they provide symmetrical and conceptually clean solutions. The stochastic search methods require significantly more computational capacity, explore the solution space more fully, and generate solutions that are largely insensitive to the initial guess. For long and intermediate length cold-formed steel columns the optimization methods identify two non-conventional alternative designs that maximize capacity. The future of this work lies in further integrating the optimization methods with additional manufacturing and construction constraints; for now, the method suggests several interesting alternative cross sections that are worthy of future study.