Recent developments in engineering education

The use of portfolio theory allows the consideration of correlation between projects and may rationalize the selection of the projects and capital budgeting. Positive coefficient of correlation increases the risk for a portfolio, while negative coefficient decreases the risk. On the other hand, the expected return of a portfolio may increase or decrease due to project correlation. The correlation between projects is due to several casual factors which are of different importance and contribution to project correlation. The importance and the level of contribution of each factor can be estimated based on experience and judgement. Experience and judgement may easily be expressed in semantic measures rather than mathematical terms. Classical portfolio theory fails to incorporate subjective information. The semantic measures can be translated into mathematical values using the fuzzy set theory. A method by which project correlation may be estimated based on experience and judgement is proposed. The method utilizes the fuzzy set theory to estimate the coefficient of correlation and the judgement uncertainty. Then, the total risk of a portfolio can be estimated.     

绿色建筑决策中的风险综合评价

绿色建筑是一新兴理念,在决策阶段存在很多不确定性因素,其风险管理具有重要的意义,本文首先分析了绿色建筑项目决策阶段存在的风险、绿色建筑决策阶段主要风险指标和因素的现状,建立合理和可行的风险评价指标体系,通过专家打分法构造判断矩阵,然后运用层次分析法和模糊综合评价法对绿色建筑决策阶段的风险,在定性分析的基础上,定量的对影响绿色建筑项目决策阶段风险因素进行科学和客观的评价,将灰色系统理论引入绿色建筑风险评价区域,给出了较明确的评价标准,实现决策风险的科学测度,为绿色建筑决策阶段的风险管理提供具体、可行的依据.     

PPP模式下基础设施项目私营方风险预警模型

从私营方的角度出发,针对PPP模式与基础设施项目的具体特点,提出了涉及到政治与法律风险、经济风险、信用风险、建设风险、运营管理风险5个方面的15项项指标组成的风险预警指标体系,并运用模糊群决策理论与物元理论构建了PPP模式下基础设施项目私营方风险预警模型。模糊群决策法可有效算出各定性预警指标的权重和评价值,避免了单一决策者的局限性,而物元模型利用综合关联度进行风险综合评价,且计算方法简单,评价结果直观。最后,通过实证研究说明了具体应用过程,结论表明该方法科学可行。     

基于贝叶斯网络的加热炉煤气泄漏风险评估

针对轧钢加热炉煤气泄漏的风险,以蝴蝶结模型为基础,建立了加热炉煤气泄漏的贝叶斯网络模型。采用模糊理论的隶属度函数、λ 截集理论、左右模糊排序法确定贝叶斯网络的先验概率,分析了影响加热炉煤气泄漏的动态因素,引入时间因素研究加热炉煤气泄漏风险随时间变化的动态特性。由实例分析得到了某加热炉煤气泄漏的风险,采用比例变化法得到敏感度分析(ROV)值曲线,从而确定重要根节点,得到了加热炉煤气泄漏风险的动态变化曲线。结果可为加热炉煤气泄漏的动态风险分析及安全管理提供借鉴和参考。     

模糊数学在结构工程中的应用

本文综述了模糊集合理论在结构工程中应用的现状,较详细地介绍了在工程不确定性分析、结构事故分析、结构安全度以及结构物遭受地震后破坏状况的估计等方面应用的情况。 文中还介绍了笔者运用模糊集合理论研究了地震危险区震害的预测方法,通过各地工程技术人员中的调查,研究了地震区多层砖房抗震设计中与房屋高度限值有关问题的情况。     

基于模糊理论大跨浅埋公路隧道施工风险评估

鉴于大跨浅埋公路隧道施工风险评估的模糊属性,采用模糊数学方法定量化处理施工风险估计中的定性问题。建立了茅山隧道施工风险多层次模糊综合评价数学模型,运用模糊理论对专家给出的茅山隧道施工各项风险因素的概率等级和损失等级隶属度进行统计分析,得到了各因素的概率及损失估计结果。基于R=P×C模型考虑了风险因素发生概率及损失对风险评估的影响,得到各风险因素、基本风险事件的风险等级,确定茅山隧道施工的安全风险、环境影响风险及整体风险等级为四级,应采取有效的风险控制措施应对。研究表明,模糊理论解决了风险评估中的模糊性及量化问题,可作为评估大跨浅埋公路隧道施工阶段风险的有效模型。     

A fuzzy approach to construction project risk assessment

The increasing complexity and dynamism of construction projects have imposed substantial uncertainties and subjectivities in the risk analysis process. Most of the real-world risk analysis problems contain a mixture of quantitative and qualitative data; therefore quantitative risk assessment techniques are inadequate for prioritizing risks. This article presents a risk assessment methodology based on the Fuzzy Sets Theory, which is an effective tool to deal with subjective judgement, and on the Analytic Hierarchy Process (AHP), which is used to structure a large number of risks. The proposed methodology incorporates knowledge and experience acquired from many experts, since they carry out the risks identification and their structuring, and also the subjective judgements of the parameters which are considered to assess the overall risk factor: risk impact, risk probability and risk discrimination. All of these factors are expressed by qualitative scales which are defined by trapezoidal fuzzy numbers to capture the vagueness in the linguistic variables. The most notable differences with other fuzzy risk assessment methods are the use of an algorithm to handle the inconsistencies in the fuzzy preference relation when pair-wise comparison judgements are necessary, and the use of trapezoidal fuzzy numbers until the defuzzification step. An illustrative example on risk assessment of a rehabilitation project of a building is used to demonstrate the proposed methodology.     

绿色建筑材料的综合评价研究

针对绿色建筑材料的特点,分析其在整个生命周期内对环境和人类健康的影响并建立了可行的评价指标体系;利用信息论和模糊理论,构造了基于熵值权的绿色建材模糊数学评价模型并给出了详细评价步骤。该评价模型也可直接用于相关领域评价。     

基于多元联系数－三角模糊数随机模拟的围岩稳定性风险评价

围岩稳定性评价受具有随机性、模糊性和未确知性特点的诸多因素影响与控制,应用传统的围岩稳定性评价方法已很难满足当今复杂地下工程的围岩稳定性评价需求。基于集对分析理论和三角模糊数随机模拟理论,探讨基于联系数和三角模糊数随机模拟的围岩稳定性风险评价模型,即基于待评样本的评价指标体集和围岩稳定性等级标准集构成的集对,构造多元联系数表达式来定量描述评价指标样本与评价标准等级之间隶属关系的层次性和模糊性;采用三角模糊数表达多元联系数的差异度分量系数的连续变化过程和不确定性,以及围岩稳定性等级标准的模糊性,并通过随机模拟技术把三角模糊数及其函数之间的运算转化为普通实数之间的运算,实现克服现有三角模糊数的乘法、除法和函数运算尚不够严谨、操作较为复杂等问题;结合指标权重计算综合联系数以风险评估样本的围岩稳定性等级。实例应用及与其他方法评价结果对比分析表明,本文方法应用于围岩稳定性的风险评价是有效可行的,且取得较好成果,此也为工程设计和施工风险评价提供了重要依据。     

A Fuzzy Diagnostic Model for Diagnosing Cracks in Reinforced Concrete Structures

Abstract: A fuzzy diagnostic model based on the concept of cause-and-effect diagraming and fuzzy set theory is presented. Two levels of parameters representing the causes of cracks in concrete are used to form fuzzy sets. The parameters represent materials used, fabrication of structural elements, loading, and environmental conditions. An expert system that links the parameters by means of fuzzy set theory is constructed using finite universal sets consisting of membership functions and fuzzy vectors. The model is capable of interpreting the causes of crack formation by means of a cause-and-effect diagram. Two examples are presented to demonstrate the effectiveness of the model in diagnosing crack formation in reinforced concrete structures.     

基于模糊层次分析法的代建单位风险评价研究

“代建制”是我国近十年来对政府投资项目传统管理体制改革的产物,具有突出的先进性,能够有效提高政府投资项目的管理水平和投资效益。文章立足于代建单位,分析了代建单位风险评价的意义,利用风险分解结构法对代建单位风险进行了识别,并提出了一种基于层次分析法、Delphi法和模糊数学理论相结合的风险评价方法,建立了代建单位风险因素集和评语集,确定出各因素权重和评判矩阵,构建出模糊评价模型。论文以江苏省某代建项目为例验证了该风险评价方法;评价结果具有参考价值,可以推广使用。     

Knoledge-Based Systems and Fuzzy Sets in Risk Management

An integrated microcomputer-based knowledge system is developed for risk management in construction. The system (Expert-Risk) applies the concepts of fuzzy set theory to evaluate the overall risk of a project. It is also integrated with various rerlational data bases that provide the system with financial and cost data necessary for bankruptcy and risk analysis. Today's construction industry involves more dynamic and construction industry involves more dynamic and uncertain planning than ever before. without professional risk management, decision makers cannot systematically approach complex problemx. The system provides a more definitive perception of the overall risk of a construction project, and a more rational basis for contingency planning and evaluation. The system allows management to focus on those risk factors which have significant impact on planning.     

基于FEAHP的绿色建筑项目风险模糊综合评价

风险评价是绿色建筑项目风险管理的重要内容。本文在文献分析的基础上,构建绿色建筑项目风险因素层次结构模型。采用集成三角模糊层次分析法和模糊综合评价法,计算出绿色建筑项目风险的模糊综合评价值,识别出关键风险因素,提出了风险应对措施。研究结果对业主提高绿色建筑风险管理水平,确保绿色建筑项目的取得成功具有理论和实践价值。     

Time–cost optimization: using GA and fuzzy sets theory for uncertainties in cost

Uncertainties should be considered in any time–cost trade‐off problems when minimizing project cost and duration, which leads to the so‐called stochastic time–cost trade‐off problem. A new approach to investigate stochastic time–cost trade‐off problems employing fuzzy logic theory is presented. The proposed approach fully embeds the fuzzy structure of the uncertainties in total direct cost into the model. An appropriate GA is used to develop a solution to the multi‐objective fuzzy time cost model. The accepted risk level of the project manager is defined through α cut approach for which a separate Pareto front with set of non‐dominated solutions has been developed. To compare the alternative set of options for any assumed project duration, associated fuzzy costs for different values of α cut are ranked employing two appropriate approaches for fuzzy costs comparison. The proposed models are applied to solve two benchmark test problems. It is shown that the models facilitate the decision‐making process by selecting specified risk levels and employing the associated Pareto front.     

基于模糊神经网络的公路隧道洞口段施工阶段风险评估

公路隧道洞口段埋深较浅,围岩风化严重,加上降雨的影响,很容易发生边仰坡失稳、洞口坍塌等事故,因此研究隧道洞口段施工风险对于保证施工安全极为重要。为了降低公路隧道洞口段施工阶段风险,分析了影响公路隧道洞口段施工阶段的风险及风险因素,运用层次分析法构建了公路隧道洞口段施工阶段风险评估指标体系,利用模糊层次综合评判法结合相关资料建立了样本数据,并对样本数据进行主成分分析;将模糊数学理论、主成分分析法与神经网络相结合建立了风险评估模型,提出了隧道洞口段施工阶段风险评估方法。选取 45 座公路隧道施工实例作为样本进行训练分析,以另外 5 座隧道作为评估目标进行评估,并与模糊层次综合评判法所得结果比较,两种方法评估结果误差较小。     

邻近盾构隧道的建筑物安全风险模糊层次分析

盾构隧道施工会对邻近既有建筑物产生潜在的安全风险。首次将模糊层次分析法引入对邻近盾构隧道的建筑物安全风险评估中。分析建筑物和隧道的影响因素,遴选出主要因素作为模糊层次评估方法的影响因子,建立了邻近盾构隧道的建筑物风险指标体系。采用专家打分法确定层次分析中各风险评价指标的权重,建立邻近盾构隧道的建筑物风险模糊层次评估模型。运用本文方法,对武汉长江盾构隧道上方的武汉理工大学电教楼进行了风险评估,得到的评估结果符合实际工况,验证了本文方法的可靠性。     

基于模糊综合评价的BT建设项目风险管理研究

基于模糊综合评价理论,导入丽水南城东扩二期区块BT项目的实证研究,分析了项目存在的风险因素和风险类别,运用＂模糊综合评价理论＂对项目风险进行了评价,进而确定丽水南城东扩二期区块BT项目风险级别,为实施项目风险管理提供指导。     

基于未确知聚类的高层建筑防火风险评估系统

目前,高层建筑的火灾防控难题一直未得到有效解决。针对高层民用建筑防火能力风险评估中评估指标获取不科学、指标体系差异大的问题,运用典型火灾事件分析法,结合《建筑设计防火规范》,科学获取影响高层建筑防火能力的12个主要不确定性风险因素,构建了更为科学的高层建筑防火能力风险评估指标体系。在此基础上,引入未确知聚类理论,构建了基于未确知聚类的高层建筑防火能力风险评估模型。并以8栋典型高层民用建筑火灾风险数据为例,进行实证分析。研究成果表明,该风险评估系统可行有效。研究成果可为高层民用建筑火灾风险防控提供一种新的方法和途径。