Dynamic modeling of the quantitative risk allocation in construction projects

Allocation of construction risks between owners and their contractors has a significant impact on the total construction costs. This research presents an integrated fuzzy-system dynamics approach for quantitative risk allocation. All the factors affecting the risk allocation process are modeled using system dynamics approach. Fuzzy logic is integrated into system dynamics modeling structure to account for the existing uncertainties. The values of different factors that have an uncertain nature are determined by fuzzy numbers. The application of Zadeh's extension principle and interval arithmetic is proposed for the system dynamics to enable the system outcomes to be presented considering uncertainties in the input variables. Using the proposed integrated fuzzy-SD model, the project cost is simulated at different percentages of risk allocation. The optimum percentage of risk allocation is determined as a point in which the project cost is minimized. The performance of the proposed method is assessed by employing the method in a tunneling project.     

基于模糊评价的单层工业厂房搬迁可行性研究

为提升单层工业厂房搬迁加固改造评估的准确性,基于模糊数学理论,将该评估分为结构损伤评估、费用评估和环境保护评估3个部分,选取12个指标作为评估因子,采用隶属函数法和类比法构造判断矩阵,再由层次分析法确定权系数向量,建立三层次两阶段的模糊综合评估模型;以某公司2栋单层厂房为例,应用该评估模型对其搬迁加固改造的技术性与经济性进行了评估。结果表明:模糊综合评估方法的评估结果客观合理,能较准确地反映单层工业厂房搬迁加固改造的优势,可为单层工业厂房的继续使用与持续发展提供有效的科学依据。     

三标度 AHP-熵优化组合赋权法在 PPP 项目风险评价中的应用

目前,政府在基础设施建设中大力提倡 PPP 模式,对 PPP 项目风险进行科学的评价是 PPP 项目顺利完成的重要保障。采用三标度 AHP 确定风险评价指标主观权重,熵权法确定评价指标的客观权重,建立优化组合赋权模型,构造拉格朗日函数对模型进行求解,得到优化组合权重。并对 AA 县给排水 PPP 项目进行风险评价,在项目实施过程中,总体风险与评价结果较为接近。研究结果表明,三标度 AHP-熵优化组合赋权法可行,能在 PPP 项目风险评价中提供可靠的指标权重。     

施工方案评价中的多级模糊优化及非结构性模糊决策分析

选择合理的施工方案是单位工程施工组织设计的核心。针对施工方案评价中影响因素复杂及非结构性因素量化等难点问题，提出了将多因素、多级非结构性模糊优选理论应用到施工方案比选中。采用四级模糊优选模型，综合考虑了影响施工方案比选的各种目标，并针对主观性较大的评价因素，引入非结构性模糊决策法和优先关系法，以确定其隶属度和权重。通过此模糊优选模型，进行了施工方案的优选，得到了比较理想的优选结果，证明了此模型在施工方案评价中的实用性。     

Automated trade‐off between time and cost in planning repetitive construction projects

An automated model is developed to support the optimization of the planning and scheduling of repetitive construction projects. The model provides the capability of optimizing two important objectives commonly sought in scheduling repetitive construction projects: minimizing project duration; and minimizing project cost. The model performs this multi‐objective optimization using a genetic algorithm approach. The output of the model is a set of optimal solutions that represent the trade‐off between time and cost in planning repetitive construction projects. Furthermore, the model can be utilized to find a single scheduling solution that provides the minimum overall project cost by simply adding project indirect cost to the obtained project direct cost for each of the obtained scheduling solutions on the Pareto optimal curve. Other important time‐related costs are also considered in the model including: early completion incentives, late completion penalties and lane rental costs. Providing the planners of repetitive construction projects with an automated set of optimal time–cost trade‐off solutions should contribute to cost‐effective and speedy delivery of this type of construction project. An application example is analysed to illustrate the use of the model and demonstrate its capabilities in generating optimal trade‐off solutions between minimizing the project time and cost for repetitive construction projects.     

钢框架结构基于整体优化策略的非线性抗震设计

针对现有抗震优化设计很少考虑结构非线性反应的缺点,提出了整体优化策略,并运用到钢框架结构造价最小的抗震优化设计中。以结构构件截面尺寸为设计变量,结构构件的总体积为目标函数,整体优化策略在以结构弹性强度和弹性变形为约束条件的基础上,增加弹塑性变形为约束条件,与我国抗震设计规范两阶段设计方法相对应,因此基于整体优化策略的优化设计结果可以作为最终的结构设计方案。整体优化策略不仅能够考虑结构的非线性反应,而且可以采用我国抗震规范的相关规定作为约束条件,适用于钢框架结构造价最小的抗震优化设计。     

基于三角模糊数的输变电工程模糊综合评价

针对输变电工程风险评价中专家主观因素所占比例较高的现状,研究了主观和客观相结合的评价方法,利用网络分析法与模糊评判法构建模糊网络风险评价模型,从而对风险实施有效控制。根据输变电工程特征,分析了影响施工安全的综合因素,建立了输变电工程风险评价指标体系,并使用两两比较判断矩阵法计算风险指标权重,再利用模糊综合评判将二级指标整合,得到项目的综合风险水平。为解决模型主观偏好的弊端,构建过程加入风险维度,用三角模糊数处理决策过程中的模糊性,对模型做进一步改善。并以某输变电工程为例,验证该方法具有可行性。     

Forecasting contractor's deviation from the client objectives in prequalification model using support vector regression

Contractor prequalification (CP) is a very complex decision-making process with nonlinearity, uncertainty and imprecision in inputs containing both subjective and objective data. The failure to perform CP can lead to large losses, delays or severe loss of project quality. Although the most reliable approach identified in the literature is currently artificial neural network (ANN), it has weaknesses that negatively affect CP. In this study, a new approach called support vector machines (SVM) has been used to forecast a contractor's deviation from a client's objectives. In order to test the model, CP for 250 virtual contractors was solved. The proposed model had a great generalization in linear, nonlinear, noisy and inductive environments. The Results showed that SVM could reliably perform even with a small amount of training data. Also when compared to ANN, SVM showed an overall better performance.     

基于未确知测度理论的工程成本风险评价

工程成本极易受到各种风险因素的影响,从而给整个项目带来潜在风险。针对工程成本风险的特点,从环境、经济、技术、管理 4 个维度出发,构建成本风险评价指标体系。考虑到风险因素本身的不确定性和评价过程的未确知性,以及指标赋值中人为主观因素的影响,选择未确知测度理论和熵权法建立评价模型。由评价模型得到风险因素测度向量,最终利用置信度识别准则对风险因素测度向量进行排序,确定风险等级。将该方法运用到实际工程中,得出该工程的成本风险处于一般风险等级,与实际情况相吻合,验证了该方法的可行性与有效性。     

Supplier selection process in an integrated construction materials management model

The procurement and management of construction materials involve challenges related to reducing inventory, speeding delivery, and increasing the control of materials, thus decreasing the overall project cost. The objective of this research was to define and develop an integrated construction materials management (ICMM) model to address these challenges by deploying principles of virtual inventory management, feasible materials management networks, and a supplier selection process. Contributions include the development of the ICMM model and the demonstrated potential of the selection supplier process for improving procurement for construction projects. The use of the supplier selection process has been demonstrated through implementation on an industrial project and using the TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) method. This process optimizes and validates purchasing at each stage of fabrication for each construction package. A variety of project-specific criteria are involved in the supplier selection process, including price, lead-time, cash rebate, and supplier performance.     

代建制下激励机制问题研究

代建制下投资人与代建人之间的关系是多任务的委托代理关系。由于投资人无法在使用之前对代建工程质量进行客观评价,且产权移交和主观评价等激励机制在代建制中实施会存在许多问题,因此根据多任务委托代理问题分析结果,此时投资人给予代建人固定工资是最优的激励机制。考虑到工程质量与代建人的努力水平,工程质量与代建工程后续维修加固费用均存在正相关函数关系,延后激励奖惩实现时间,以使用阶段代建工程的维修加固费用指标作为对提高工程质量这一任务的激励依据,并采用使用阶段实现激励奖惩的方式,能够有效地缓解投资人、代建人双方的信息不对称矛盾,提高投资人对代建人激励水平,从而双方获得更大的效益。     

THE ROLE OF PRICING ON INTEGRATED WATER MANAGEMENT AT THE INDUSTRIAL PARK LEVEL: A CASE OF TEDA

Increasing water shortage and water pollution issues have attracted people to seek an integrated water management approach. This paper presents an integrated water management model at the industrial park level by employing a case of TEDA. Such a model is an overall management model for optimizing water resources within an industrial park, seeking potential water reuse among industries, incorporating the size and cost of reclaimed wastewater delivery systems. The main focus of this paper is to test how pricing strategy can influence water reuse scenarios by doing a cost sensitivity analysis. The results Indicate that when being set at the correct level, increased water charges could help reduce freshwater use and wastewater discharge, while covering administrative costs, financing environmental improvements (e.g. cleaner production), or subsidizing the operation of the wastewater treatment plant and the maintenance of freshwater infrastructure, therefore, providing water reuse incentives for water users within an industrial park.     

给深圳华强北带来繁荣的区位因素

通过对华强北的空间位置、物业属性、通达性,与新旧市中心的互动关系,在城市改造升级过程中出现的时空上、产业(尤其是商业)转型上的契机,自身业态上的关联度和由此产生的整体吸引力,以购物为指向的市区意象等区位因素的分析,揭示其从工业区向大深圳商业中心演变的区位性内在机制。     

房地产企业项目团队间知识共享障碍因素研究

基于扎根理论质性研究方法，通过对深度访谈资料进行扎根分析，将资料中知识共享障碍因素的相关内容进行概念化、范畴化和编码处理，构建了房地产企业项目团队间知识共享障碍因素模型。研究结果表明，4 项主体因素、1 项客体因素和 4 项环境因素是当前房地产企业项目团队间知识共享的主要障碍因素，为房地产企业管理者采取有效措施改善和提高知识共享效果奠定了理论基础     

工程质量风险的模糊层次分析

将模糊数学与层次分析方法相结合 ,建立了模糊层次分析模型并应用于工程项目质量风险分析 .为质量风险辩识、估计和评价提供了一种主客观相结合的分析方法     

模糊理论与AHP相结合的BOT风险研究

BOT是国际上出现的一种新的融资与项目管理模式。分析了BOT项目的风险来源及构成 ,将模糊数学方法与AHP(层次分析法 )相结合 ,建立了模糊层次综合评判模型并用于对BOT项目风险评估的研究 ,为BOT项目风险辨识、估计和评价提供了一种主客观相结合的分析方法。     

Nature as a Model for Large-scale Planting Design

This study was undertaken to arrive at an objective design process to prepare planting designs for large areas of woodland, as found in regional parks, green belts around cities and hillsides along freeways. The method involves preparing a computer program consisting of: (1) a 'Community Specifier Database' (CSD), determining the suitable plant community for the project site, based on its climatic and overall soil characteristics; (2) a 'Law Extracting Package' (LEP), determining the laws governing the distribution of species within an existing native plant community, with respect to topographic and soil variation; and (3) a 'Species Assigning Package' (SAP), which uses the laws from the LEP to assign the suitable species to each location, with its specific topographic and soil characteristics, within the project site. The program is intended to be used as a decision support system for landscape architects in arriving at planting designs resembling natural plant communities.     

Impact of contractor's optimized financing cost on project bid price

The financing cost depends on the incoming and outgoing cash flow throughout the project, and can differ greatly from project to project. This study proposes a model that calculates the expected financing cost based on the cash flow forecast. This approach is more realistic than assuming an approximate percentage of the total cost. The proposed model calculates the bid price using an optimized financing cost that is obtained by selecting an optimum combination of available financing alternatives offered by different lenders. The proposed model minimizes financing cost, reduces the bid price, enhances the competitiveness of the bidder, increases the contractor`s negotiating power with a lender by providing an optimum financing schedule, and eliminates the risk of financing surprises during construction. This study investigates the impact of different financing considerations on bid price in three cases to prove the effectiveness of the proposed model.     

A cost allocation method for facilities siting with fixed-charge cost functions

The fixed-charge plant location problem determines the sites at which to place central treatment facilities as well as the assignments of communities to those facilities. We show here that the mathematical programming dual of a special version of the plant location model provides cost allocations to the communities which satisfy the core conditions of an n-person cooperative game. These cost allocations are faulted- because they may fail to provide equity among the participants. A new methodology is proposed, the Separable Costs Opening Cost method (SCOC), to allocate costs among the participants once the optimal set of facilities and coalitions has been determined. The SCOC is guaranteed to determine allocations which are insidexhe core and hence increase the fairness of the allocation.     

Welfare-maximizing and profit-maximizing agroindustry location: A comparison

Traditionally, the location model has assumed that firms choose their location and input usage so as to maximize their profits. However, in the planning version of the location model, the industrial location might be selected on the basis of a welfare-maximizing objective. This paper attempts to develop systematically the theory of plant location for a welfare-maximizing agroindustrial firm and to compare it with its profit-maximizing counterpart. Our analysis shows that, unless the transport cost of raw materials is linear in distance and the firm's production function is homogeneous of degree one, the welfare-maximizing location chosen by a regulated agroindustrial firm always differs from that of its profit-maximizing counterpart. It also demonstrates that the results obtained previously for a non-agroindustrial firm cannot be applied directly to its agroindustrial counterpart. Received: August 1998/Accepted: January 1999