Resource-constrained scheduling for continuous repetitive projects with time-based production units

In construction projects of highways, pipelines, and tunnels, labor and equipment continuously move in a linear geographic layout. This class of continuous repetitive projects encounters the resource-constrained problem when there are limits on the availabilities of resources (labor and equipment). Conventional scheduling models divide continuous repetitive projects into space segments. The premise is that crews would maintain the same production rate in each space segment. However, when the length of segment is indivisible by the production rate, this assumption leads to an inefficient schedule which asks the crews to change their production rate, a reflection of their size, composition, and associated equipment, in the middle of a time period. Unproductive time would then be spent in extra preparation and unnecessary warming up. Another drawback is that production units divided in space cannot be directly linked to the time-based payment schedule. In light of these shortcomings, this paper presents a scheduling model to find the optimal set of production rates in different time periods for each crew, considering limited availability of resources. To be practical, the proposed model addresses work continuity while maintaining lead-time and lead-distance between operations. The optimization problem is solved by an evolutionary strategy algorithm, which is easy to program and takes less execution time, with no need for selection and crossover process. A real-life project is used to validate the performance of the proposed model in terms of effectiveness, efficiency, and stability.     

Multiobjective design of Work-In-Process buffer for scheduling repetitive building projects

Variability in production is one of the largest factors that negatively impacts construction project performance. A common construction practice to protect production systems from variability is the use of buffers (Bf). Construction practitioners and researchers have proposed buffering approaches for different production situations, but these approaches have faced practical limitations in their application. A multiobjective analytic model (MAM) is proposed to develop a graphical solution for the design of Work-In-Process (WIP) Bf in order to overcome these practical limitations to Bf application, being demonstrated through the scheduling of repetitive building projects. Multiobjective analytic modeling is based on Simulation–Optimization (SO) modeling and Pareto Fronts concepts. Simulation–Optimization framework uses Evolutionary Strategies (ES) as the optimization search approach, which allows for the design of optimum WIP Bf sizes by optimizing different project objectives (e.g., project cost, time and productivity). The framework is tested and validated on two repetitive building projects. The SO framework is then generalized through Pareto Front concepts, allowing for the development of the MAM as nomographs for practical use. The application advantages of the MAM are shown through a project scheduling example. Results demonstrate project performance improvements and a more efficient and practical design of WIP Bf. Additionally, production strategies based on WIP Bf and lean production principles in construction are discussed.     

Optimized acceleration of repetitive construction projects

Contractors and/or owners frequently need to accelerate the delivery of construction projects. Contractors may have to accelerate in order to benefit from contractual bonus, avoid penalties, recover from delays and/or avoid undesirable weather and site conditions. Owners, on the other hand, may order acceleration to meat business and operational opportunities. This paper presents an algorithm for schedule updating, dynamic rescheduling and optimized acceleration of repetitive construction projects. Schedule updating captures the exact progress on site. Dynamic rescheduling aims at capitalizing on the repetitive nature of the project to fine-tune the remaining portion of the project. Optimized acceleration presents an optimized time–cost trade-off that is tailored for repetitive projects. Through a set of iterative steps, the optimized acceleration procedure divides each activity into segments and identifies the segments that would shorten project duration if accelerated. For those identified segments, the ones with the least cost slope are selected and queued for acceleration. Through the proposed segmentation of activities this algorithm provides optimum allocation of additional acceleration resources, thus is rendered capable of identifying least cost acceleration plans. The algorithm allows users to select among different acceleration strategies such as working overtime, working double shifts, working weekends, and employing more productive crews. The presented algorithm maintains work continuity and accounts for typical and non-typical activities. The algorithm is implemented in a spreadsheet application, which automates calculations, yet allows users to fine tune the algorithm to fit the project at hand. The developed algorithm is applied to a case study drawn from literature in order to illustrate its basic features and demonstrate its accuracy.     

Integrated visualized time control system for repetitive construction projects

Construction control is an essential management function for successful delivery and achieving of construction projects’ goals. Considerable research efforts have been done regarding project control. However, literature suffers from a lack of visualizing the controlling process. With the growth of using visualization techniques in construction, Building Information Modeling (BIM) and Geographic Information System (GIS) have recently attained a widespread contribution in visualization of construction progress. BIM is a process of creating virtual models data that represents building facilities. In this research, BIM represents a platform for nD (n-Dimensional) visualization of construction progress. The advantages of this paper stems from three main contributions for construction projects control: 1) developing of a mathematical model for time control of repetitive construction projects; 2) an automated system to dynamically integrate project progress with BIM technique; and 3) a GIS-based tool to visualize the progress of distributed sites. The developed model provides abundant information to help decision makers take the appropriate corrective actions. An example application is presented to demonstrate the applicability of the developed system.     

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.     

Entropy-based scheduling of resource-constrained construction projects

A method is presented for resource allocation and scheduling of resource-constrained projects by use of a measure of the projects' entropy. The entropy, as a measure of the degree of disorder in a system, is an indicator of a project's tendency to progress out of order and into a chaotic condition and it can thus serve to forecast a project's development. The entropy metric used in the analysis is based on the resource assignments per activity (required vs. assigned resource units).     

A new approach for automation of location-based earthwork scheduling in road construction projects

Accurate information of working locations is vital for efficient resource planning, safety of the construction site and monitoring the weekly progress of earthworks, which is missing in the existing linear scheduling methods. Construction managers have to depend on the subjective decisions for resources allocation and progress monitoring from location aspects. This has caused uncertainties in planning and scheduling, and consequently delays and cost overruns of projects. In this context, a prototype computer-based model was developed using the theory of the location-based planning. An arithmetic algorithm was designed by incorporating road design data, sectional quantities, variable productivity rates and haulage distance. This paper focuses on the improvement and demonstration of the model functions through a case study experiment, which include the automatic generation of location-based earthwork schedules and the optimisation of the weekly resource allocation when and where necessary from the location aspects, considering different options such as construction sequences of the cut/fill sections, site access points and the equipment sets with known productivity rates. The study concluded that the model is a decision supporting tool that assists in the resources planning, identifying time–space congestion, monitoring the activities progress on a weekly basis from the location aspects, and reducing the gap when communicating the scheduling information amongst the construction site teams.     

Optimal labor scheduling for construction projects in the middle east

In countries where the construction workers are hired on a temporary basis, the decision maker has long been confronted with the dilemma of whether to hire-fire workers in order to meet the fluctuating demand or to keep the manpower at a certain level and let the changing demand be met by overtime work. An integer programming model is presented in this paper to derive an optimal labor schedule for construction projects in the Middle East. The sign of the deviation between the overtime cost and the wage cost was found to be the key criterion in selecting the proper manpower policy.     

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 simulation-based method for effective workface planning of industrial construction projects

The generation of well-defined and moderately sized field installation work packages for the construction workforce, referred to as workface planning, has been recently employed to plan large-scale industrial construction projects under tight schedules. However, traditional CPM-based scheduling of several thousand work packages (e.g. 5000 activities multiply by 10 work packages per activity on average) is a tedious, error prone process. Defining proper logics and controlling congestion among work packages crossing several work areas, and also effective resource allocation over time are other major challenges in workface planning. This paper presents a novel simulation-based framework to implement workface planning for large-scale industrial construction projects. This framework proposes a time-stepped discrete event simulation-based modelling for dynamic resource allocation based on congestion and other constraints on the job site. The proposed method is demonstrated and tested against traditional CPM-based solutions based on an actual case study.     

国内公路建设项目工程决算的编制及其探讨——基于《公路建设项目工程决算编制办法》

基于《公路建设项目工程决算编制办法》,对国内公路建设项目工程决算的编制进行了探讨,重点论述了计算机辅助完成工程决算编制的过程,以期对公路建设项目管理人员有所帮助。     

关于建设工程项目投标方法的探讨

从投标前的决策、组织投标及投标书的编制三方面对建设工程项目投标方法进行总结与探讨。投标前决策要做两项工作：明确投标目的和认真研究招标文件。组织投标需做三项工作：建立有效的投标组织机构、考察施工现场及调查项目所在地的市场环境。编制投标书是投标工作的重点,需做好五项工作：编制施工组织设计、复核工程量、编制报价、选择拟投入的人力及投标书的善后工作。这些总结对从事建设工程项目投标的人员有一定参考意义。     

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.     

建设工程投标报价方法的探讨

通过对招投标法的理解和对招标文件的分析 ,得出一种快速准确的方法来确定建设工程投标报价。指出这种方法是应用数学方法对投标进行模拟 ,对确定出具有竞争力的投标报价有一定的指导作用     

A many-objective optimization model for construction scheduling

Abstract

In recent years, the number of stakeholders of construction projects has significantly increased; this has required the simultaneous achievement of competing objectives, such as reductions in the time, cost, resources, and environmental impact of a project, for example. In order to achieve a balance between these objectives, several multiple-objective construction scheduling models have been reported in the literature. However, several challenges have been encountered, due to the complexities of modelling and visualizing more than three objectives simultaneously. Some of these challenges are addressed in this work via the development of a many-objective scheduling model (MOSM) based on a non-dominated sorting genetic algorithm for the simultaneous optimization of four objectives: time, cost, resources and environmental impact. Coordinate plots are used to visualize the trade-offs made between all four of these objectives. A weighted sum is introduced that offers the project team the freedom to choose an optimal solution, depending on the specific priorities of the project, and the practical application of the model is demonstrated via a case study. Our MOSM allows the optimal outcome to be achieved in construction projects with multiple objectives.     

基于网络协同的建设项目价值管理系统

价值管理(Value Management,VM)是降低建设项目成本和改善项目执行效率和质量的一个重要途径,然而,VM在我国建设领域中还存在应用不足、认识不够、相关法律法规不完善以及成效不显著等问题。由于工作计划不同、技术手段差异以及不支持远程协同等因素的影响,针对香港建设领域开发的交互式价值管理系统(IVMS)难以直接应用于内地。为此,本文在IVMS基础上,提出了适用于我国建设领域VM实践的价值管理系统IVMS-CN。IVMS-CN是一个基于网络协同的群体决策支持系统,它由网络通讯平台、协同平台和管理平台等三部分组成,能够为用户提供一个远程协作环境和群体决策支持平台,实现远程参与VM研究,并促进参与者之间的信息交流和共享,减少过程损失,增加信息增益,从而实现VM研究效率与质量的提高。     

Developing a risk assessment method for complex pipe jacking construction projects

Pipe jacking (PJ) construction is a highly complex and uncertain process so that performing an accurate risk assessment is essential to the success of a project. This study presents an innovative risk assessment model which combines fuzzy inference with failure mode and effect analysis (FMEA) to improve the effectiveness of existing risk assessment methods for pipe jacking construction. The proposed model maps the relationship between occurrence (O), severity(S), and detection (D) with the level of criticality of risk events in three steps: fuzzification, fuzzy rule-based inference, and defuzzification. A case study of a PJ construction project for water transmission in Shanghai, China is presented to demonstrate and validate the proposed method. A total of 31 potential risks was identified according to the PJ construction procedure and two-round Delphi questionnaire surveys. By using the proposed fuzzy-FMEA approach, the most critical risks in the PJ construction process can be identified, in particular, the shaft structure construction, jacking operation, and steel pipe segments welding. The proposed method overcomes the inherent weaknesses of traditional FMEA method and provides a reliable and distinguishable risk ranking system by properly reflecting the complexity of PJ construction environment. The study also provides a comprehensive risk identification and evaluation tool for industrial practitioners who manage or involve with PJ construction projects.     

Resource-driven scheduling of repetitive activities

Repetitive activities are found commonly in the construction of high-rise buildings, pipeline networks and highway and housing projects. Construction crews assigned to these activities often perform the work sequentially, moving from one repetitive unit in the project to the next. Because of this frequent crew movement, construction of repetitive activities should be scheduled in such a way as to enable prompt movement of crews among the repetitive units so as to minimize idle crew time. In order to maximize the efficiency of crew utilization, the schedule of repetitive activities should be resource driven, and should satisfy the crew work continuity constraint in addition to precedence relationships and crew availability constraints. This paper presents a flexible algorithm for resource-driven scheduling of repetitive activities that satisfies the three constraints, and considers the impact of a number of practical factors encountered commonly during the construction of this class of projects. The algorithm is applied in two stages: the first achieves compliance with logical precedence relationships and crew availability constraints, and the second achieves compliance with the crew work continuity constraint. A numerical example of a highway project is analysed to illustrate the use of the algorithm and demonstrate its capabilities.     

System development for non-unit based repetitive project scheduling

Repetitive activities are commonly found in construction projects. It is stated in many literatures that repetitive scheduling methods are more effective than traditional CPM methods in the planning and scheduling of repetitive construction projects. Nevertheless, almost all the repetitive scheduling methods developed so far have been based on the premise that a repetitive project is comprised of many identical production units. In this research a non-unit based algorithm and a prototype system are developed for the planning and scheduling of repetitive projects. Instead of repetitive production units, repetitive or similar activity groups are identified and employed for scheduling. The developed system takes into consideration (1) the logical relationship of activity groups in a repetitive project, (2) the usage of various resource crews in an activity group, (3) the maintaining of resource continuity, and (4) the time and cost for the routing of resource crews. A sample case study is conducted for system validation, as well as for demonstration. Application of repetitive scheduling methods can be facilitated with the developed system.