Schedule control model for linear projects based on linear scheduling method and constraint programming

China Railway is undertaking massive construction and development projects.A reasonable and resource-leveled schedule that allows for adjustments for unforeseen circumstances during construction is critical for managing railway construction projects. Currently, most construction projects use traditional network planning methods or the Gantt schedule for project management. However, these methods have limited applicability to railway construction projects, which are typically linear. This study uses the linear scheduling method and constraint programming techniques for solving schedule control problems faced during railroad construction. The proposal comprises a schedule control model, scheduling model, and schedule control system; the scheduling model is central to the schedule control model. Characteristics such as high flexibility and practicality facilitate multi-objective optimization during scheduling and modification of the linear schedule. The proposed model and algorithm were validated by comparing results with actual data from a highway construction project and the Urumqi–Dzungaria railway construction project.     

The determinants of the vertical boundaries of the construction firm: comment

A method is presented for allocating resources to construction activities and for scheduling construction projects under resource constraints by considering the effects that such resource limitations may have on the tendency of the activities (and the project in general) to fall into disarray and behind schedule. Resource‐constrained scheduling problems (RCSP) are very common in real‐life construction projects and because of their nature their numerical solution is computationally intensive. The method utilizes a measure of each activity's perceived level of disorder stemming from resource limitations. The proposed technique aims to optimize the number of resources assigned to the activities and to schedule the project so as to minimize the overall project's tendency to fall into disorder. The entropy‐like metric used in the scheduling optimization is related to the ratio of required over‐assigned resource units per activity, and its utilization allows a planner to take into consideration project disorder when planning a project. A case study and its mathematical framework help demonstrate the ‘duration vs. disorder’ trade‐off analysis that planners should perform when considering possible activity resource assignments and the feasibility of these assignments in terms of induced disorder. The entropy optimization method proves to be a powerful project‐planning metric.     

Schedule-dependent evolution of site layout planning

The appropriate layout of temporary facilities on a construction site has a large impact on construction safety and productivity. For the duration of a project the site layout may need to be efficiently re-organized at various intervals to satisfy the schedule requirements and to maintain site efficiency. This paper presents a practical model for schedule-dependent site layout planning in construction. The proposed model uses a combination of artificial intelligence tools (knowledge-based systems, fuzzy logic, and genetic algorithms) to generate, optimize, and re-organize the site layout plan at frequent intervals during the project. The model incorporates flexible representation of irregular site shapes and several options for placing facilities. Based on the proposed model, an automated system is developed, fully integrated with widely used scheduling software. At each schedule interval, the system recalculates the space requirements and, for the convenience of congested sites, can utilize parts of the constructed space to accommodate temporary facilities. Details of the schedule-dependent model are described, and its application in an actual case study project is presented to demonstrate its capabilities.     

Incorporating rework into construction schedule analysis

Rework has been a primary cause of cost and schedule overruns in large construction projects. While several research efforts have analyzed the causes and effects of rework and provided guidelines to reduce rework, almost no research exists to analyze the impact of rework timing and quantity on schedule delays and to support decisions on cost effective recovery. This research presents a quantitative mechanism for schedule analysis considering rework. The mechanism has three aspects: (1) a new schedule representation of rework magnitude as negative percentage complete for affected activities, documented on the specific date on which the rework is detected; (2) a modified daily-windows delay analysis to apportion project delays among the responsible parties; and (3) an optimization technique for determining the least costly corrective action strategy that recovers project delays. The proposed approach is applied to a case study to demonstrate its ability to consider rework impact, in combination with other progress events by other project parties. This research offers an innovative quantitative approach to consider rework timing and amount in delay analysis and corrective action optimization.     

Minimizing duration and crew work interruptions of repetitive construction projects

This paper presents the development of a novel scheduling model for minimizing the duration and crew work interruptions of repetitive construction projects. The main contributions of the developed model are its ability to (1) generate early and late start schedules that minimize the duration of repetitive construction projects while keeping the total work interruptions of their utilized crews to a minimum; (2) calculate novel types of crew work-continuity floats that consider the impact of delaying the early start of repetitive activities on crew work continuity; (3) develop a wide range of intermediate schedules between the early and late start schedules that maintain the least project duration and minimum total crew work interruptions; and (4) compare shortest duration schedules with and without interruptions to identify the best schedule that fits the specific project needs. The model performance was evaluated using an application example of a repetitive construction project.     

项目进度控制的双边缓冲区方法研究

工期延误是建设项目管理中的重要问题。一方面,事后控制和无缓冲区方法不足以应对工程进度风险,有缓冲区的应变管理可在一定程度上弥补这些不足;另一方面,目前根据工作持续时间按固定比率设缓冲区的方法未考虑各种工作的具体情况。文章根据工作信息流理论提出了设双缓冲区的方法,即在工作开始前和结束后分别设前缓冲区和后缓冲区,并提出根据不同缓冲区的用途和工程变更的预测确定各缓冲区长短的方法。建立了项目工作实施过程系统动力学模型,演示了双缓冲区在调节工期压力、消除工期延误、减少潜在变更影响进度等方面的作用。双缓冲区方法是有效实施进度事前控制,保证项目及时完成的新工具。     

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.     

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.     

Modelling financial decisions in construction firms

Some contractors predict their corporate cash flow on the basis of individual contracts without considering the relationships between the overall before-tax profit, risks, other crucial qualitative factors, or the allocation of resources within the company. Moreover, some contractors, in predicting their cash flow, focus only on the early-start progress in the project and their predictions of progress are too pessimistic, or result in the overuse of resource in order to make up for delays. In the present research a decision model is established for a contracting firm. It provides a methodical system for construction financial decision-making, and a way of solving a financial decision problem under qualitative and fuzzy circumstances. The model can be applied to the management of corporate cash flow, thereby facilitating the minimal use of resources. The information provided by the model allows the planner to eliminate excess use or idleness of resources during the scheduling of a project. Financial forecasting may also suggest the best time to invest in a new project. Four projects for a medium size construction firm in Hong Kong were employed as case studies in order to evaluate the mathematical model. The cases involve two objectives: maximize profit margin and minimize construction risk (consider in a qualitative factor). The model leads to a compromise optimal schedule that provides the contracting firm with the optimal schedule for achieving optimal profit and construction risk by making optimal use of the contractor's resources.     

Visualizing high-rise building construction strategies using linear scheduling and 4D CAD

Project teams face ever increasing pressure to deliver projects as quickly as possible. To meet these demands, contractors are faced with the need to explore various construction strategies in order to meet delivery dates, and to assure themselves as to the achievability and quality of a schedule. Various visual representations of a project's schedule and associated information combined with visual representations of the project in progress, i.e. 4D CAD, can assist with these tasks of identifying effective construction strategies for shortening project duration, assessing their workability, and judging schedule quality. Such visual representations aid communication amongst project staff and facilitate brain-storming, and, implemented well they can provide clear, fast, and multi-dimensional feedback to the project team. In this paper, we describe aspects of our work which is directed at formulating a dynamic visualization environment that links 3D CAD, a generalization of traditional CPM which embraces linear scheduling, dual product representations (scheduling and CAD system) and their mapping onto each other, and schedule and CAD graphics in a manner which facilitates the relatively rapid exploration of alternative construction method and scheduling strategies for large scale linear projects (e.g. high-rise buildings, bridges, etc.). Requirements of such an environment include quickness, treating scale, working at multiple levels of detail, dealing with design variability, and realistic representation of the work. Use is made of a realistic example to highlight aspects of our approach and identify important issues that must be addressed if a visualization environment useful for construction professionals is to be developed.     

不确定性条件下建设工程设计进度优化研究

随着建设工程项目的大型化、复杂化,其设计中的迭代问题也呈多发趋势。但相应技术或方法的缺乏,使得管理者在面对此类问题时常显得束手无策。因此,本文尝试将DSM理论引入到复杂建设工程设计进度管理领域,针对传统进度管理方法的缺陷及现有复杂建设工程设计过程中易发的迭代问题,构建一种以DSM理论为基础的进度优化体系,同时用蒙特卡洛模拟方法对设计进度的不确定性进行研究,最终将其运用于某大飞机配套工程设计进度优化中。结果显示,该模型在迭代活动识别、活动排序优化及工期分布预测计算方面均具有一定的优势,并可以通过解耦操作实现进度的优化,通过仿真模拟预判关键活动,为复杂建设工程设计进度的优化提供了新的思路。     

浅谈项目施工进度管理

工程项目施工的进度目标能否顺利实现,不仅体现了施工单位项目管理水平的高低,同时对工程项目的经济效益也有非常大的影响。从现场管理的角度,通过分析施工进度控制管理在项目管理中的地位和作用、影响工程项目施工进度的众多因素,简单地阐述了工程项目进度控制的原理,提出了工程项目进度控制方法,供施工单位参考。     

Applying cluster identification algorithm and simulation to generate probabilistic network schedules for design projects

Scheduling of a design project is complex because design activities often have information dependencies between each other. This study proposes a network‐based model to schedule design projects and generate probabilistic project durations. The proposed model applies a modified cluster identification algorithm to evaluate information dependencies between design activities to facilitate the establishment of a schedule network (and regroup activities to support the assignment of design work); it also uses a simulation approach to incorporate the effect on duration of the uncertain number of design iterations. The model is implemented in four stages, which are breaking down the design work; evaluating the dependencies; identifying concurrent activities; and estimating the durations of activities and simulating the duration of design project. The advantages of the proposed model are demonstrated through its application to an example project, which was reviewed by industrial practitioners. Practitioners felt that the generated detailed scheduling data could help them to control their design work more precisely than a bar chart. Additionally, the simulated probabilistic project duration provided them with an awareness of the risk involved in meeting the contractual deadline.     

A framework for an automated and integrated project scheduling and management system

Construction projects are becoming progressively larger and more complex in terms of physical size and cost. Building information modeling (BIM) is being regarded as a revolutionary change for managing the entire lifecycle of a construction project. However, the information provided by BIM cannot fulfill the requirements of on-site project scheduling and management. This paper presents a BIM-based framework with the function of developing the near-optimum schedule plan according to project objectives and project constraints for project scheduling and management. An automated database management system, a schedule simulation system, and a MD (multi-dimensional) CAD model creator provide a reliable platform for the proposed framework. To verify the concept and test the feasibility of this framework, a computer implementation called NDSM (N-Dimensional project Scheduling and Management system) was developed and implemented in a construction project.     

基于交通延误最小的道路养护策略优化

道路养护常常需要关闭相应的机动车道 ,因而会产生新的交通延误。为减少四车道道路养护时所带来的交通延误 ,论文建立了基于交通延误最小的道路养护策略的整数规划优化模型 ,其中目标函数为路网总的交通延误最小 ,约束条件为总的可用工作时间 ;并通过具体的实例对模型进行了验证。在整数规划优化的基础上 ,论文还讨论了通过引入交通标志对交通流进行诱导从而进一步减少交通延误的可能性     

基于不确定性因素的水利工程信息系统进度计划风险模型

进度计划风险控制是水利工程项目管理信息化实施目标的重要内容之一,对项目成本目标和质量目标的实现起到决定性作用。水利工程项目管理信息化进度计划受确定性和不确定双重因素的影响,进度计划表现出一定的随机性。基于水利工程项目群,分析了人为、环境和政策等不确定性因素对水利工程信息化进度计划的影响,并构建进度计划风险模型,通过蒙特卡洛方法对模型进行仿真性实验,验证了模型的有效性。     

重庆松藻矿区建设工程工期控制若干问题的探讨

本文就目前影响松藻矿区建设工程工期的一些原因进行了阐述,科学合理地分析了影响松藻矿区基本建设的工期延误的一些原因,对加快施工进度、缩短工期等方面进行了探讨。     

隧道建设进度延迟的机理分析及其对策

根据隧道施工的现实需求,结合实际隧道工程项目。介绍了Ishikawa法,并将其引入隧道进度管理,对该工程项目的进度延迟进行了原因分析。针对性地从渗漏水控制、激励机制以及组织管理等方面提出了相应的对策,从而有效地解决了隧道项目施工中的进度延迟问题。     

A framework of critical resource chain for project schedule analysis

Analysing a schedule is beneficial to help stakeholders understand the scheduled project. Project schedules, which create time plans based on the critical path method (CPM) or on resource‐constrained project scheduling problem (RCPSP) optimization, are targets herein. The Theory of Constraints (TOC) treats a schedule as a system. Schedule elements are suspected constraints and a goal depends on the schedule creation policy. Resource information is further surveyed herein to identify true constraints. A framework is proposed to integrate identified constraints on a schedule, and the critical resource chain concept is introduced. Three scenarios illustrate the proposed framework under different scheduling considerations. Results explain schedule constraints, and several schedule analysis issues are discussed.     

VR-based planning of construction site activities

This paper presents an approach to the integration of site-related activities into the planning and scheduling of the entire construction project. The paper starts by briefly reviewing some common methods used by construction firms in the planning and scheduling of site activities. Next follows a discussion of current research efforts concerned with the modelling of site-related procedures. Then a virtual-reality-based model is proposed, which uses both knowledge-based simulation of the work progress and visualisation capabilities, to achieve the desired integration. Finally the prototype system is described and its potential is demonstrated through several examples.