Development of linear programming for capital budgeting of construction projects

The UK construction industry suffers the largest number of bankruptcies of any sector of the economy, with many companies failing because of poor financial management, especially inadequate attention to poor cash flow forecasting. The financial model outlined in this paper demonstrates the potential application of simulation methods in assessing financial alternatives.     

A genetic algorithm-based method for scheduling repetitive construction projects

This paper develops a new method for scheduling repetitive construction projects with several objectives such as project duration, project cost, or both of them. The method deals with constraints of precedence relationships between activities, and constraints of resource work continuity. The method considers different attributes of activities (such as activities which allow or do not allow interruptions), and different relationships between direct costs and durations for activities (such as linear, non-linear, continuous, or discrete relationship) to provide a satisfactory schedule. In order to minimize the mentioned objectives, the proposed method finds a set of suitable durations for activities by genetic algorithm, and then determines the suitable start times of these activities by a scheduling algorithm. The bridge construction example from literature is analyzed to validate the proposed method, and another example is also given to illustrate its new capability in project planning.     

基于改进序列线性规划法的空间桁架结构优化设计

在空间桁架的优化设计中,仅把截面面积作为设计变量并不能得到结构的最优解。只有把桁架结构的截面面积和节点坐标作为设计变量,才能大幅降低结构重量及造价。空间桁架结构的优化设计多为复杂的非线性问题,序列线性规划法是解决非线性规划问题的典型算法。本文作者将改进的序列线性规划法结合SAP2000 API功能,对空间桁架进行优化设计。数值结果表明,改进的序列线性规划法具有良好的收敛性和稳定性,可以有效地进行空间桁架结构的形状优化设计。     

A mixed-integer linear programming approach for temporary haul road design in rough-grading projects

Temporary haul road plays a pivotal part in achieving cost-efficiency and successful project delivery in heavy civil and industrial construction. Temporary haul road layout design has been empirically performed by field managers, superintendents or even truck drivers largely based on experience instead of science. Previous research endeavors in earthmoving research devised analytical algorithms to minimize the total earthmoving cost and developed simulation models to optimize earthmoving resources and processes. In the same domain, this research introduces an optimization methodology for temporary haul road layout design in order to facilitate mass earthmoving operations and improve construction performances on a typical rough-grading site. A Mixed-Integer Linear Programming model, integrated with a cutting plane method, is established for the identified problem. In particular, the cutting plane method is introduced to refine the optimization formulation by maintaining field accessibility and haul road continuity, thus ensuring practical feasibility of the analytical solution. Performances of the newly devised algorithms were benchmarked against genetic algorithms in solving ten test cases. Further, feasibility of the proposed methodology was evaluated based on a real-world case study. In conclusion, the proposed methodology is capable of tackling the temporary haul road layout design problem with high computing efficiency and delivering optimal results that are ready for field implementation.     

基于外部性特征的环境项目融资约束机制研究

通过对环境项目的正外部性问题及外部性对资源配置效率的影响进行较为深入的分析,并阐述排污收费对污水和垃圾处理设施项目投融资的重要影响。从宏观和微观视角研究环境项目融资的外部约束机制,将外部约束机制从功能上设计为激励与规制两大制度体系,进而构建宏观外部机制及相应的配套制度机制。设计基于外部性特征的约束机制,包括政策制度机制、规制与保障机制、排污收费机制、环境污染的治理机制等,以期建立有效的投融资经济制度环境,最大化地吸引社会民间资本。分析结果表明,对环境项目融资必须建立良好的外部政策环境和制度约束机制,实现经济发展与环境保护的统一。     

Graph-based deep learning model for knowledge base completion in constraint management of construction projects

Construction projects face various constraints in terms of materials, labor, equipment, and documents, which can interrupt the scheduled work. Package-based constraint management (PCM) is a state-of-the-art graph-based approach that follows the lean theory to effectively model, monitor, and remove constraints before the commencement of work, ensuring smooth construction and minimizing delay and waste. PCM relies on exploring and investigating project knowledge bases (KBs), formed by entity-relation-entity triples of constraints. However, most PCM KBs are incomplete and suffer from poor semantics, which hinders the PCM functions. Although many KB completion (KBC) methods exist in the field of artificial intelligence, they primarily focus on general knowledge and exclude the features of specific domains. Therefore, they cannot be directly applied to complete PCM KBs. To address the issue, this study proposes a novel deep learning model, referred to as the domain information enhanced graph neural network (D-GNN). The features of the developed D-GNN include (1) building a domain ontology to enrich semantics with rule reasoning, (2) applying the GNN to learn and encode embeddings of constraint entities and relations, and (3) employing a convolution neural network (CNN) for decoding and identifying missing triples. D-GNN improves the existing KBC methods by integrating two types of domain information, namely, the ontological classes and working contexts into GNN and CNN, respectively. The experimental results verified that the D-GNN reached an accuracy of 0.848–0.951, and the domain information integration increased the performance by up to 0.263. In practical testing, the D-GNN significantly reduced the KBC time to 1/6–1/35 of the manual approach and reached higher accuracy. Therefore, the proposed D-GNN can facilitate PCM by providing complete KBs and supporting downstream constraint monitoring and removal.     

An online predictive control method with the temperature based multivariable linear regression model for a typical chiller plant system

Building Simulation - As many studies prefer to focus on the accuracy of prediction models in model-based problems of chiller plants, the practicality and feasibility of the models used for field...     

A test of a linear programming model of agriculture

Conclusions The pattern of agricultural production and land use specified by the linear programming model was greatly different from the actual pattern existing in 1963. I believe that the application of this model or similar models to other areas would not approximate actual patterns of production or resource use. Therefore, it is concluded that the assumptions upon which the model is based are inadequate for the construction of models aimed at estimating the economic feasibility of water resource investments. Further work on the model itself is necessary before it can be properly used in the predictive sense required in economic feasibility studies.In order to improve the model, it will be necessary to quantify additional constraining relationships that are generally encountered by the type of economic units being studied. Care should be taken not simply to build empirical realities into the model so as to reduce differences between the model results and existing production and resource use. Rather the type of constraints needed appear to require such studies as how economic units tend to react to opportunities for increased profits in situations where changes in habits would be required for the realization of these increased net returns.Studies which accurately estimate the economic efficiency of water resource investments need to consider how economic units will react to changes in water resources. The use of mathematical programming models in these studies serves to make this need more apparent.Richard Howes and Associates     

前交叉韧带重建术在胫骨平台骨折合并韧带损伤患者中的临床效果及对并发症发生率的影响研究

目的:探究前交叉韧带重建术在胫骨平台骨折合并韧带损伤患者中的临床效果及对并发症发生率的影响。方法:选取2013年1月-2018年1月本院收治的胫骨平台骨折合并韧带损伤患者30例,按照随机数字表法将患者分为研究组和对照组,各15例。对照组使用常规手术治疗,研究组使用前交叉韧带重建术治疗。比较两组患者的手术指标、临床效果和并发症发生情况。结果:研究组手术时间以及住院时间均长于对照组(P<0.05),出血量大于对照组(P<0.05);研究组治疗总有效率高于对照组(P<0.05);研究组膝关节不稳定发生率低于对照组(P<0.05),两组的切口不良愈合、感染、关节僵硬、骨筋膜室综合征发生率比较,差异均无统计学意义(P>0.05)。结论:在对胫骨平台骨折合并韧带损伤患者进行治疗的过程中,采用前交叉韧带重建术,能够有效改善患者手术指标,优化临床效果,减少并发症的发生,对提升患者生存质量具有重要意义,应当在临床中进一步推广。     

Enhanced heuristic for finance-based scheduling of construction projects

Typically, construction contractors operate under cash-constrained operating conditions. The lag between the time when contractors spend money to accomplish work on site and the time when payments are actually made by clients, which partially compensate contractors for the accomplished work, constantly creates a finance deficit. Contractors often supplement finance deficits using external funds procured through establishing credit-line bank accounts which typically allow contractors to withdraw cash up to specified credit limits. This makes the task of project scheduling considering the constraints of specified finance very important for financial and operational planning. This scheduling concept and technique are referred to as finance-based scheduling. An enhanced heuristic is proposed to devise finance-based schedules of multiple projects within contractors’ portfolios. The enhancement is achieved by replacing the exhaustive enumeration technique employed in the heuristic to specify activities’ start times with a polynomial shifting algorithm. This enhancement resulted in a substantial reduction in the number of solutions explored before a feasible solution is encountered. The enhanced heuristic was validated through comparison with the integer programming technique using 240 problems of randomly generated networks of sizes that range from 30 to 240 activities. Further, it was proved that the enhanced heuristic can be easily scaled up to handle portfolios of multiple large-size projects.     

Planning linear construction projects: automated method for the generation of earthwork activities

Earthworks planning for road construction projects is a complex operation and the planning rules used are usually intuitive and not well defined. An approach to automate the earthworks planning process is described and the basic techniques that are used are outlined. A computer-based system has been developed, initially to help planners use existing techniques more efficiently. With their input, the system has been extended to incorporate a knowledge base and a simulation of the earthworks processes. As well as creating activity sets in a much shorter time, the system has shown that for a real project, the model is able to generate activity sets that are comparable to those generated by a project planner.     

基于等效线性化的土–地下结构整体动力时程分析方法研究

地下结构抗震设计简化分析方法离不开场地地震反应分析,而频域内的等效线性化方法是一维土层地震反应分析的主流方法。在一维土层地震反应分析的等效线性化方法的基础上,提出了一种地下结构抗震设计的等效线性化分析方法,并给出场地材料参数的确定方法。将该方法应用于地铁车站的横断面抗震分析中,并与土体直接采用非线性的Davidenkov模型进行的动力时程分析方法对比,两者计算误差满足工程需要的精度要求。此方法兼具场地等效线性化方法和地下结构动力时程分析方法的双重优势,可以作为一种动力时程分析方法运用于地铁车站等地下结构的抗震设计中。     

Construction project control under resources constraints by fuzzy linear programming

Fuzzy linear programming (FLP) provides an alternative method of programming and the authors claim improvements in flexibility more appropriate to construction situations, but believe this is an area that needs further research.     

基于替代试件模型的振动台迭代学习控制方法

由于加载系统的非线性、不确定性以及振动台 试件耦合特性,非迭代加载的振动台试验的复现精度较差;而迭代加载过程常对试件造成损伤,进而改变试件力学性能。针对此问题,提出一种基于替代试件模型的振动台迭代控制方法。该方法首先构建与试件动力特性相近的替代模型,再利用该模型完成迭代学习得到振动台加载命令,最后开展原试件的振动台试验。本文重点研究了获取替代试件模型动力参数的方法。研究表明：针对线性试件,基于试件模态参数的反解法以及基于遗传算法的优化方法均能获得替代效果良好的线性模型参数;对于非线性试件,考虑阻尼器参数的线性替代模型能实现更好的替代效果。     

基于线性模型的导线网平差方法研究

传统的导线网平差采用的数学模型为非线性模型,需要进行线性化,并且平差前需要获取各未知参数的近似值。本文提出一种基于线性模型的导线网平差方法,该方法首先以角度作为观测值,利用最小二乘法解算出各导线边的方位角。然后根据各边方位和边长构建基线向量,再以基线向量作为虚拟观测值解算各待求点最或然坐标值。利用该方法进行导线网数据处理,不需要解算待求点近似值,而且程序设计非常容易实现。为验证其正确性,分别就传统方法和新方法设计程序对实例数据进行验证比较,证明其结果是可靠的,而且新方法所需要代码量远远小于传统方法。     

Critical path effect based delay analysis method for construction projects

Assessing schedule delay's impact on total project duration to distribute delay liability remains a controversy. None of existing delay analysis methods is perfect because including an element of assumptions, subjective assessment and theoretical projection. Windows-based delay analysis methods are excellent in identifying and measuring construction schedule delays. Based on a previous study identifying potential problems in available windows-based delay analysis methods, this study proposes an innovative windows-based delay analysis method, called the effect-based delay analysis method (the EDAM method). The EDAM method performs delay analysis using extracted windows and determines delay impacts by considering the effects of delays on the critical path(s). According to its application to hypothetical cases and comparisons with other methods, the EDAM method is efficient in delay analysis and effective in solving concurrent delays and determining schedule shortened. The proposed EDAM method is a good alternative for schedule delay analysis for construction projects.     

A linear programming model for cash flow management in the Brazilian construction industry

A linear programming model has been developed for optimal cash flow management addressing specific cash flow issues related to the construction industry. These include typical financial transactions, possible delays on payments, use of available credit lines, effect of changing interest rates, and budget constraints that often occur in the construction industry. A small size project from the Brazilian construction industry is provided as a case study, aiming at evaluating the potential benefits from using the model. Different changes to the basic structure of the model allow and establish the consistency of the results. Alternative formulations are suggested to deal with uncertainties, longer planning horizons, and multiple subcontractors and suppliers. In addition to the tangible financial earnings derived from the optimization process, the simple structure of the model, as a network flow and corresponding equations, provides much visual insight concerning the relationships between the external inputs and the variables of the problem. Optimal results have yet to be achieved in a real life situation, but a better view of whole cash flow management is provided when using the model.     

基于AHP法的房地产项目投资方案的比较选择

指出房地产投资不但有其内在的规律,在对投资进行分析时还需特定的理论与方法,在认真总结国内现有理论与方法的基础上,对房地产项目经济评价进行研究,并把房地产项目多方案评价作为重点进行分析。     

System reliability theory based multiple-objective optimization model for construction projects

Although the system reliability theory has a high capability in quality quantification, while system reliability optimization (SRO) has been well developed in manufacturing engineering, seldom can their applications be found in the construction industry. This study aims to develop a system reliability theory based multiple-objective optimization model to conduct SRO, and then identify the cost–quality trade-off solution for construction projects. First, the whole construction project is treated as a system composed of different work packages. Second, the reliability function is employed to quantify the quality performance and the nonlinear cost-reliability function is set up. Moreover, according to the physical arrangements among each work package, the system reliability structural function is determined. Third, the total construction cost minimization and system reliability maximization are defined as multiple-objectives. The particle swarm optimization algorithm is employed to search for the Pareto-optimal solutions, from which the final cost–quality trade-off solution can be selected. A real construction case is used to evaluate the workability of the proposed model and the results have fully proven its validity and practicality.     

基于层次分析法的混凝土建模在质控中的应用

针对混凝土质量提出运用层次分析法，分析影响混凝土质量的各种因素，建立实用有效的层次结构模型，并列表采用求根法进行计算，经过一系列的综合分析和一致性检验，最终确定混凝土进行质量控制的重点，为混凝土进行质量控制提供了理论依据和指导。