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.     

Activity Gazer: A multi-dimensional visual representation of project performance

Project failure often arises from a flawed or delayed perception regarding the discrepancies between planned and actual performance; for this reason, project managers constantly seek better methods of capturing, processing, and presenting the complexity of multi-dimensional project data. Visual representations provide a useful means of monitoring key aspects of project performance, thus enabling project managers to better execute their duties. This paper introduces the conceptual framework for, and a prototype implementation of, Activity Gazer, a novel paradigm that renders project monitoring and control data in an intuitive visual environment. Activity Gazer applies the concept of earned value management, among other metrics, to provide performance information regarding schedule, cost, quality, and safety at the activity level. This information visualization tool facilitates management-by-exception and improves the effectiveness and efficiency of project managers for large-scale construction projects.     

Design of a construction management data visualization environment: A top-down approach

Explored in this paper is the topic of designing a construction management (CM) data visualization environment with emphasis on its use for supporting the time management function during the planning and execution phases of construction projects which are characterized by sizeable volumes of data of different types. A brief overview of recent construction data visualization work is first provided. Then, as part of a top-down design approach, we introduce concepts and useful terminology related to a structured way of thinking about analytical reasoning and visual analytics, and their relationship with construction management functions. The focus of the latter then shifts to how a construction data visualization environment can support project participant analytical reasoning needs for the management of time, specifically planning/predicting and monitoring/diagnosing/controlling construction conditions and time performance. A case study of aspects of an actual project examined using the construction data visualization environment developed to date is then presented. Purposes served include demonstrating the breadth of support that can be offered for reasoning by such an environment, and providing a test case for demonstrating the kind of evaluation process one should engage in to assess how well an environment conforms to the requirements set out for it. Time management functions treated for this case study include assessing quality of a baseline schedule, assessing actual vs. planned construction conditions and time performance, and assessing reasons for deviations. An evaluation of the current environment is then made to assess conformance/non-conformance with the requirements established for it and to identify worthwhile extensions to it. The paper concludes with a discussion of lessons learned from work performed to date, and their application to create a more comprehensive visualization environment that supports multiple CM functions.     

An evaluation of the applicability of 4D CAD on construction projects

4D CAD models that integrate physical 3D elements with time, have been used to visualize construction processes in several projects worldwide. 4D models have been used and have been shown to have benefits over processes that span the entire lifecycle of a project such as collaboration with stakeholders, making design decisions, assessing project constructability, identifying spatial conflicts in construction and so on. Despite these benefits, several organizational and project-specific barriers have hindered the widespread adoption of 4D CAD. In order to reconcile the theoretical benefits of 4D models with the practical difficulties faced in implementation, there is an urgent need to explore the implementation of 4D models on construction sites as well as the perceptions of intended users/beneficiaries towards this implementation. This paper aims to address this need and contribute to our understanding of how 4D models must be introduced, positioned and implemented on construction sites, so as to maximize both their acceptability and their usefulness. We describe two 4D models of infrastructure projects and two 4D models of commercial projects that have been built and implemented. Through a process of structured and unstructured interviewing the paper gauges the response of project participants across various organizational levels on each of these projects as to the usefulness of 4D in project planning and control. Through qualitative and statistical analysis of the data we establish that 4D CAD is likely to be most beneficial in the project shaping or planning stage and in the construction stage. In the project shaping stage, 4D CAD is likely to be particularly useful in communicating construction plans and processes to clients, while during the construction phase, 4D CAD is likely to be particularly useful in comparing the constructability of work methods visually in order to detect conflicts or clashes, and as a visual tool for contractors, clients, subcontractors and vendors to review and plan project progress. Further, upper management and site workers are more likely to use and derive benefits from the visualization of processes using 4D given their lack of site related knowledge or skills, while construction professionals who are more construction-savvy are more likely to appreciate and benefit from the analytical and planning aids that 4D simulations provide during the construction phase. However, it is likely that despite these benefits 4D CAD models might not diffuse through the construction industry unless 4D modelling and analysis is integrated into existing project planning approaches. The paper concludes with a brief discussion on future 4D software development that seeks to bring about such integration and leverages the benefits of 4D CAD to bring about improved operational efficiencies on construction sites.     

A linear‐discrete scheduling model for the resource‐constrained project scheduling problem

For some specific types of construction projects, the classical CPM or PDM scheduling techniques are not the most suitable. Few specific scheduling approaches have been developed to cope with construction projects that are made of either repetitive activities or activities with linear developments. But real‐world construction projects do not consist only of such activities. They are generally made of a mixture of linear and/or repetitive activities and of more conventional activities. To allow this, the linear scheduling problem is reformulated, so classical schedule calculation approaches can be used. The implementation of some Allen's algebra features to avoid adverse discontinuities and to allow crew/work continuity, together with a resource‐driven and space‐constrained scheduling are among the key features of the proposed approach. It is also a spin‐off of off‐the‐field practices used for scheduling real projects in the particle accelerator construction domain; an excerpt from such a construction project is provided for illustrating the methodology.     

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.     

Optimizing schedule for improving the traffic impact of work zone on roads

Many different types of construction projects set up work zones on roads. Especially in urban areas, lane closures as a result of work zones have a considerable impact on local traffic. However, for a construction project that consists of several work zones and several work crews, the traffic impact may be improved by appropriate scheduling. Therefore, this paper proposed a scheduling model based on the route-changing behavior of road users. The proposed model calculates the traffic delay of vehicles by microscopic simulation, and applies team ant colony optimization to search for a near-optimal schedule. The project planner then ensures that the contractor executes the activities according to the near-optimal schedule. The proposed model is applied to schedule a sewer system construction project in a city. The results of our study indicate that with our proposed model the total traffic delay is reduced by 11.1% when compared with a schedule proposed by the project planner.     

SCHEDULING OF NONSERIAL LINEAR PROJECTS WITH MULTIPLE NON-OVERLAPPED LOOP STRUCTURES

Existing dynamic programming formulations are utilized for the scheduling of serial linear projects. These formulations cannot, however, be used for the scheduling of nonserial linear projects. The intent of this paper is to present a nonserial dynamic programming formulation for the scheduling of linear projects with multiple non-overlapped loop structures. The objective of the nonserial dynamic programming solution is to provide for the selection of resources, interruptions, and lags for production activities that lead to the minimum project duration. The advantages of this nonserial dynamic programming approach include its ability to handle work interruption and variable production rates. In addition, the developed system produces a graphical representation of the project schedule of minimum duration. A nonserial linear project is treated herein using the proposed method.     

Accelerating linear projects

Scheduling linear repetitive construction projects, such as highways and pipelines, poses unique challenges due to maintaining crew work continuity. An efficient method is presented, developed to accelerate the delivery of this class of projects so as to meet a specified deadline with least associated cost. The method is simple and ensures crew work continuity. An iterative approach is employed, where, in each iteration, the project schedule is analysed and an activity is identified as the controlling activity. A controlling activity is an activity that if accelerated, would reduce project duration at least additional cost. Upon its identification, the method selects an expediting strategy that would reduce project duration, and the project is rescheduled. Several expediting strategies are considered, including working overtime, double shifts and weekends. The method is implemented in a prototype software that operates in a Windows^® environment, providing a user‐friendly graphical interface. It has an open architecture, enabling the user to actively participate in tailoring the generated schedule to suit the requirements of the project at hand. The proposed method accounts for incentives and liquidated damages to aid users in identifying the most cost‐efficient schedule. A relational database model is implemented in Microsoft Access^® to store typical crews and their associated productivity, as well as their availability dates. A project, drawn from the literature, is analysed to demonstrate the basic features of the proposed method and highlight its capabilities.     

基于线形图的地铁工程4D进度控制系统研究与应用

地铁工程涉及专业广、建设周期长、内容复杂,且属于线形工程,采用CPM方法编制进度计划,会导致进度计划非常的复杂、难以直观反映任务的地理位置及工作面搭接关系和施工过程中的空间冲突问题。提出一种基于线形图的地铁工程进度管理方法,形象地显示地铁工程的每一个任务的地理位置和耗费的时间,以及同一工作面上不同任务的位置搭接关系。并通过构建基于线形图的进度冲突识别算法,实时检测当前进度计划可能存在的空间冲突问题。在此基础上,通过数据库将进度计划与3D/CAD模型建立关联关系,构建4D可视化进度管理系统,直观地反映施工过程中的空间冲突问题。本系统在某地铁工程中成功应用,及时发现了施工计划中的空间冲突问题,实现了对项目实时、精准的控制,提升了地铁工程进度管理的水平,提高了投资效益。     

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.     

Resource Leveling Based on Line of Balance and Constraint Programming

This study investigated resource leveling problems concerning linear construction projects based on the line of balance (LOB) technique and constraint programming. In addition, an LOB‐based scheduling optimization model for resource leveling is proposed. This model retains the advantages of the conventional models, including multiple‐resource management and natural rhythm concept, and showcases new abilities: scheduling optimization without specifying a fixed schedule; scheduling optimization on more comprehensive optimization objects and variable values; maintaining continuity of resource while completely eliminating the occurrence of idle time; handling more comprehensive constraints after the addition of logical constraints and explicit expression of certain new constraints. The flexibility, practicality, and solution quality of the proposed model were enhanced accordingly. Further, a scheduling system was developed to assist in schedule optimization and visualization. Lastly, effectiveness of the proposed model was verified based on four case studies involving three case projects investigated in extant LOB‐based studies.     

4D CAD Based Method for Supporting Coordination of Urban Subsurface Utility Projects

Coordinators of inner city utility construction works face increasing difficulty in managing their projects due to tight physical restrictions, strict deadlines and growing stakeholder fragmentation. This paper therefore presents a 4D CAD based coordination method that supports project plan scoping, formalizing and synchronizing. We developed and implemented the method by conducting ethnographic action research in four project cases. In these projects, we observed that 4D-models generated with the method allowed practitioners to identify project interfaces and conflicts, to identify schedule shortcomings and to evaluate delays. By introducing the method and reporting on its empirical evaluation we extend 4D CAD's domain of applicability with mid and small-sized utility projects and address a need for 4D implementation studies.     

Applicability of 4D modeling for resource allocation in mega liquefied natural gas plant construction

Four-dimensional (4D) modeling has gained much potential in improving construction process design and planning. The integration of three-dimensional model with scheduling information has been shown to enable the effective detection of construction process design and planning flaws. However, the research work in 4D has been predominantly focused on the building construction industry. 4D has been rarely explored in the oil and gas industry, particularly Liquefied Natural Gas (LNG) plant construction. It is very difficult to conceive the scale and complexity of mega-projects in the LNG sector. This paper presents a study with the goal of investigating the feasibility and benefits of 4D in supporting LNG construction projects. 4D models were developed at both the activity level and the operations level, and geometry-based virtual construction was implemented to rehearse the construction process for the purpose of identifying potential risks and safety issues. These models were used for synergistic planning for the whole project and for resource scheduling. It has been demonstrated in this paper, mega LNG construction projects can benefit from 4D in terms of improved process planning and control.     

Integrating automated data acquisition technologies for progress reporting of construction projects

Controlling construction projects necessitates controlling their time and cost in an effort to meet the planned targets. Management needs timely data that represent the status of the project to take corrective actions, if needed. This paper presents a control model that integrates different automated data acquisition technology to collect data from construction sites required for progress measurement purposes. Current automated data acquisition technologies are described, and their suitability for use in tracking and controlling construction activities is assessed. This includes bar coding, Radio Frequency Identification (RFID) 3D laser scanning, photogrammetry, multimedia, and pen-based computers. The user can move with a tablet PC in the construction site and record, take snapshots and also hand written comments about activities on site. The proposed cost/schedule control model integrates with the automated data acquisition technologies, a planning and scheduling software system, a relational database, and AutoCAD to generate progress reports that can assist project management teams in decision making.     

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.     

A methodology for scheduling overlapped design activities based on dependency information

The practice of overlapping activities is becoming a requirement for fast-tracking complex construction projects. The amount, timing, and nature of the information exchanged between pairs of activities determine the degree to which pairs of activities may be overlapped. This paper presents a four-step process for scheduling the design phase of fast-tracked construction projects while taking into consideration information exchange among project activities. The process starts with capturing and quantifying this exchange of dependency information. A contemporary scheduling tool, the dependency structure matrix (DSM), aids in generating the shortest (overlapped) schedule based on dependencies among the different design disciplines. An algorithm is designed to calculate the shortest possible schedule for the design phase of a construction project. The developed scheduling algorithm is unique as it includes information exchange alongside task durations. The algorithm is validated in the context of a real-world case study, a fast-tracked multi-billion dollar educational facility project in the Arabian Peninsula.     

Optimizing project selection and scheduling problems with time-dependent resource constraints

This study presents an optimization model using constraint programming (CP) for project selection and scheduling problems with time-dependent resource constraints. A generic model is proposed to maximize the total profit of selected projects for construction and R&D departments given scheduling problems with various resource constraints during specified time intervals, including consumed and renewable resource limitations. Due to different periodical procurement strategies and annual budget concerns, this research considers various practical limitations for scheduling and allocating resources, such as budget limitations and resource constraints. For additional practicality, the optimization model integrates a project selection mechanism, scheduling precedence, and relationships between projects. To illustrate the model capabilities for solving project selection and scheduling problems, the current study presents two scenarios for maximizing profit, including fifteen candidate projects with time-dependent resource constraints. Analysis results demonstrate that the proposed model allows planners to determine an optimal portfolio with specified resource constraints according to various time intervals, and benefits decision-making for project selection and scheduling.     

复杂施工环境下轨道交通项目进度管控方法与应用研究

为了提高轨道交通项目建设进度管控水平,确保轨道交通项目在复杂施工环境下顺利开展。依托宁波轨道交通2号线一期工程项目实践,分析项目进度管控的重难点问题,并对比了几种常用进度管理方法。考虑轨道交通项目建设过程中时间、资源等不确定因素的影响,提出适用于复杂施工环境下的轨道交通项目进度管控方法,并以石碶站B 号出入口工程为例进行实证研究。结果表明,改进工序工期估计和缓冲区设置的关键链技术有效缩短了项目工期,提升了项目进度管理水平,可为类似工程项目提供参考。