Impact of Inspected Buffers on Production Parameters of Construction Processes

This paper examines the production implications of quality control inspections conducted on the buffer between processes in a construction project by modeling the linkage between these processes. Inspection of partially completed work at the end of one activity but before the beginning of work by the next activity is fairly common. Work that is deemed to be of sufficient quality is then made available for the next activity. Work that is deemed insufficient requires rework, typically by the trade appropriate to the activity that fed into the buffer, to bring the work into compliance. This has implications for workload management for that trade, of course, as well as for the reliability of work flow to the successor or downstream processes. While such situations are common in all construction sectors, an example from the residential construction sector was examined via a simulation model augmented by field data collected from residential construction projects. The impacts of the work flow into the predecessor process, the inspection pass rate, and resource availability were examined. The inspection pass rate was found to dramatically affect the reliability of work flow, unless resources are unlimited. Furthermore, the inspection pass rate was found to be functionally related to the production parameters of the process.     

LEAPCON: Simulation of Lean Construction of High-Rise Apartment Buildings

A lean model has been proposed for the construction management of high-rise apartment buildings with customized apartment designs. It incorporates a number of changes to traditional management practice, including single-piece flow with pull scheduling, work restructuring, and multiskilling. A simulated construction process scenario was devised for experimental evaluation of the model. The simulation was first implemented as a live management game, in which participants played the roles of the clients, general contractor, and subcontractors. Eleven runs with different teams indicated that the lean model increased throughput, improved cash flow, and reduced apartment delivery cycle time. However, the limitations of the live simulation led the writers to implement a discrete event computer simulation of the same process. The computer simulation reinforced the findings of the live simulation and emphasized the specific beneficial effect of single-piece flow under pull scheduling. The lean model may be of immediate interest to construction planners and managers because it enables full customization with minimal waste and no additional resources. The demonstrative clarity of the lean model simulation, both live and computerized, makes it a powerful tool for education and research.     

WorkPlan: Constraint-Based Database for Work Package Scheduling

A database program called WorkPlan has been created to systematically develop weekly work plans. Such work plans are used by crew foremen in scheduling work packages and allocating available labor and equipment resources. WorkPlan adopts the Last Planner methodology, which implements several lean construction techniques. A week prior to conducting work, WorkPlan guides the user step by step through the process of spelling out work packages, identifying constraints, checking constraint satisfaction, releasing work packages, and allocating resources; then at the end of the week, collecting field progress data and reasons for plan failure. This systematic approach helps the user create quality work plans and learn from understanding reasons for failure. The lean planning philosophy underlying WorkPlan and the functionality of the computer program implementation are detailed in this paper. Various ways of displaying work package data are illustrated. WorkPlan's job-shop scheduling view complements the view traditionally adopted by project management, as is reflected in scheduling tools using the critical-path method.     

Key Constraints Analysis with Integrated Production Scheduler

Project delays due to late availabilities of resource and information (RI) prerequisites are one of the major threats to construction management. It is desirable to avoid such delays through better means of constraint management. With most contemporary planning methodologies and tools, it is generally difficult to represent many hidden flow constraints in a construction work plan. However, evaluating the impact of flow constraints is crucial in determining their criticalities, based on which the flow constraints may be prioritized and consequently resolved to minimize project delays. Due to the fact that limited resources are often shared among various trades, it may not be practical to resolve all the constraints simultaneously so that a tradeoff is inevitable, which suggests that management should focus on the most important ones termed as key constraints (i.e., those directly contributing to project delays). This paper presents a methodology that augments the traditional critical path method with RI availability constraints to analyze the causes of delays and locate the key constraints binding on project completion without ambiguity based on the principles of the theory of constraints. The methodology of key constraint analysis has been implemented with the integrated production scheduler, a constraint-based scheduling tool which facilitates the modeling, analysis, and management of constraints at the production planning level. An illustrative example is depicted to demonstrate how the proposed methodology works.     

Contributors to Construction Debris from Electrical and Mechanical Work in Hong Kong Infrastructure Projects

The crucial problem of construction debris is of increasing concern in Hong Kong. In the construction industry, the electrical and mechanical (E&M) installations in the infrastructure, for example, buildings, tunnels, or dams, are some of the major and usually complex components. Difficulty in coordinating the various trades affects productivity in general, and has a major impact on the quantity of construction debris. By identifying the sources of waste at each stage of E&M engineering work, some of the construction debris can be eliminated at the source during production. This paper investigates the critical production shortcomings in the E&M sector in Hong Kong. The study is based on a survey that includes a preliminary questionnaire survey, brainstorming exercises with a focus group, structured interviews with experienced frontline supervisors, and a second focus group exercise to test findings and proposed measures. The principal findings are that “poor coordination” and “design changes and/or errors” are major contributors to variations or change orders and rework, which in turn result in a high volume of construction debris. The results also indicate that construction debris can be minimized in the E&M sector of the construction industry, if the material wastes from incidental work are reduced and also controlled better in a new work process flow pattern through recommended construction project management improvements for reducing critical production shortcomings.     

Finance-Based Scheduling of Construction Projects Using Integer Programming

Construction scheduling is the process of devising schemes for sequencing activities. A realistic schedule fulfills the real concerns of users, thus minimizing the chances of schedule failure. The minimization of total project duration has been the concept underlying critical-path method/program evaluation and review technique (CPM/PERT) schedules. Subsequently, techniques including resource management and time-cost trade-off analysis were developed to customize CPM/PERT schedules in order to fulfill users’ concerns regarding project resources, cost, and time. However, financing construction activities throughout the course of the project is another crucial concern that must be properly treated otherwise, nonrealistic schedules are to be anticipated. Unless contractors manage to procure adequate cash to keep construction work running according to schedule, the pace of work will definitely be relaxed. Therefore, always keeping scheduled activities in balance with available cash is a potential contribution to producing realistic schedules. This paper introduces an integer-programming finance-based scheduling method to produce financially feasible schedules that balance the financing requirements of activities at any period with the cash available during that same period. The proposed method offers twofold benefits of minimizing total project duration and fulfilling finance availability constraints.     

Implications of Even Flow Production Methodology for U.S. Housing Industry

Production building in the residential sector is often described as the portion of the construction industry that is most like the manufacturing sector. In modern tract construction in the United States, a small number of models are generally repeated several times in a relatively confined area, using specialized trade contractors to complete each phase of each home. Management of the handoffs between predecessor and successor trade contractors is therefore a critical component in the successful completion of a residential project. In order to bring more reliable planning to this process, a workflow-leveling strategy known as even flow production has come into use in the industry in recent years. Even flow production is a strategy intended to reduce the variability in the workflow for trade contractors in the process, thereby gaining production efficiencies. In practice, different operational definitions are in use. This paper describes a series of simulation experiments to identify the management implications of two common strategies (activity-based versus start-based). A special-purpose simulation template was built for the Simphony environment for this purpose. The pace chosen for the flow of activities was found to significantly affect the speed at which the subdivision was completed. The even flow strategy was found to affect the subdivision completion time only slightly, but to have a significant impact on workflow variability and management effort. Control of the pace of starts of only the first activity exhibited nearly the same degree of variability as if the pace of starts were matched to a sales pace.     

Identifying and Assessing Influence Factors on Improving Waste Management Performance for Building Construction Projects

Environmental sustainability has become one of the key drivers for continuous growth in the construction industry. Many project practitioners face challenging circumstances in finding an effective way to prevent pollution and minimize wastes by making the best use of the increasingly scarce natural resources. However, most of these efforts are focused on planning and/or design strategies; therefore, they fail to thoroughly cover the environmental issues based on the construction execution level. Further, there is a lack of quantitative measurement system and management-level guidance. To overcome these limitations, this paper proposes a new methodology that assists project managers to assess the performance level of a project in terms of waste management practice. This study is based on a two-pronged approach. One is the identification of the waste management influence factors that play an important role in decreasing waste and increasing recycled materials on construction sites. The other is the development of an assessment tool to measure the level of waste management performance for a particular project. As a result of this work, 59 factors were identified and an assessment tool was developed based on quantification of these factors. The tool has been proved to effectively measure waste management performance throughout four real-case validity tests. From the industry perspective, this paper contributes to establishing the environmentally sustainable production systems by providing the project stakeholders with an established set of influence factors and with a diagnosis tool for measuring their current performance. Additionally, project owners can use the output of the tool, especially the total index score, as a measure to benchmark the level of waste management for continuous improvement.     

Resource-Activity Critical-Path Method for Construction Planning

In this paper, a practical method is developed in an attempt to address the fundamental matters and limitations of existing methods for critical-path method (CPM) based resource scheduling, which are identified by reviewing the prior research in resource-constrained CPM scheduling and repetitive scheduling. The proposed method is called the resource-activity critical-path method (RACPM), in which (1) the dimension of resource in addition to activity and time is highlighted in project scheduling to seamlessly synchronize activity planning and resource planning; (2) the start/finish times and the floats are defined as resource-activity attributes based on the resource-technology combined precedence relationships; and (3) the “resource critical” issue that has long baffled the construction industry is clarified. The RACPM is applied to an example problem taken from the literature for illustrating the algorithm and comparing it with the existing method. A sample application of the proposed RACPM for planning a footbridge construction project is also given to demonstrate that practitioners can readily interpret and utilize a RACPM schedule by relating the RACPM to the classic CPM. The RACPM provides schedulers with a convenient vehicle for seamlessly integrating the technology/process perspective with the resource use perspective in construction planning. The effect on the project duration and activity floats of varied resource availability can be studied through running RACPM on different scenarios of resources. This potentially leads to an integrated scheduling and cost estimating process that will produce realistic schedules, estimates, and control budgets for construction.     

Work Structuring to Achieve Integrated Product–Process Design

This paper presents “work structuring,” a term used to describe the effort of integrating product and process design throughout the project development process. To illustrate current work structuring practice, we describe a case study involving the installation of door frames into walls in a prison. We analyze why various problems existed. To improve the work structuring effort, we apply the “five whys” to develop local and global fixes for the system of precast walls and door frames. The five whys is a technique to elicit alternative ways of structuring work without being constrained by contractual agreements, traditions, or trade boundaries. We discuss the importance of dimensional tolerances in construction and how these affect the handoff of work from one group of workers to the next. We argue that these constraints and tolerance management practices are so embedded that project participants can miss opportunities to better integrate product and process design. We propose shifting the focus of work structuring from maximizing local trade efficiency to improving overall performance in the delivery system of a capital project.     

Job Satisfaction of Women in Construction Trades

Existing research on women in construction focuses on engineers and entrepreneurs, yet little to no attention has been given to women in trades. Thus, the aim of this research is to review the literature on tradeswomen and to conduct a localized study to determine if demographic variables affect satisfaction with work, pay, opportunities, supervision, and people on the job for tradeswomen. These variables include age, education, number of dependents, number of trade years, duration of work, and frequency of work outside of the local area. Thirty-nine tradeswomen from the Cincinnati area were surveyed to assess their satisfaction or dissatisfaction with construction work. Currently, the literature review indicates that research on tradeswomen is limited and largely restricted to identifying measures that can attract and retain women in construction trades. Studies on motivation and job satisfaction of construction workers neither identify nor compare perceptions of tradeswomen about their work. Results of this exploratory study showed that pay, benefits, and job security are most important to women in their occupation. Although tradeswomen appear to be satisfied with the nature of work in construction trades, this is not the case in terms of pay, benefits, and job security. Demographic variables did not affect the level of job satisfaction for women in construction trades. Research on tradeswomen is essential and important as the industry tries to change its image and encourage diversity in order to mitigate labor shortage.     

Simplified Spreadsheet Solutions.?II: Overall Schedule Optimization

Overall schedule optimization, considering time, cost, and resource constraints is a difficult task due to the inherent complexity of projects, the difficulties associated with modeling all aspects combined, and the inability of traditional optimization tools to solve this large-size problem. In this paper, a practical approach is presented for the modeling and optimization of overall construction schedules. To simplify modeling, a spreadsheet-based model is developed to be easily usable by practitioners. The spreadsheet model integrates critical-path network scheduling with time-cost trade-off analysis, resource allocation, resource leveling, and cash flow management. The model uses the total project cost as the objective function to be minimized. To facilitate this large-size optimization, a nontraditional optimization technique, genetic algorithms, is used to locate the globally optimal solution, considering all aspects simultaneously. Details of the proposed model are described, and a hypothetical case study was used to experiment with it. Integration of the model with a simple information system is described to automate the development of optimal construction schedules.     

Production System Loading–Cycle Time Relationship in Residential Construction

Production home building possesses characteristics similar to manufacturing processes, such as the construction of more or less similar houses repeatedly and a growing demand for mass customization of homes. As a result of these similarities, larger homebuilders often attempt to view their production system as an assembly line process. However, the management tools generally utilized by these home builders are those used in other sectors of the construction industry, such as critical path method scheduling, cost estimating, and earned value analysis. These management tools do not provide an explanation or control/prediction tools for many undesirable situations that arise during home building, such as increasing cycle time which slows delivery of product to consumers and increases project capital costs, and increasing amounts of work in process that increases capital investment and thereby decreases company financial performance. In order to bring better management tools to the residential construction industry, this study examines relationships between cycle time, work in process, system throughput, new construction starts, and the capacity of the production system using building permit data for new single family homes in Chandler, Ariz. The applicability of Little’s law, a basic equation used in factory production management models, to a residential production system is examined. This study shows a definite, predictable relationship between cycle time, work in process, and production system throughput. It provides a pathway for further study of production system characteristics that have historically not been included in construction management models, with the expectation of developing new construction management tools that will account for more of the characteristics of construction production systems that affect project performance and company financial performance.     

Resource Sharing in Linear Construction

In the method developed, the conventional method of allocating resources are not used. Instead, resource‐hour units are employed. This enables to allocate resources precisely and the analysis becomes realistic unlike any other method. The method uses linear programming to determine the maximum rate of construction and the resource requirements in various activities. Sharing of resources which are available in limited quantities and balanced trades are all catered for in this development. The economics of using additional resources, working overtime and the optimal usage of all resources are the more important aspects of this paper. The step by step process of introducing additional resources and overtime ease the decision making process considerably. The method also helps to determine whether it is more economical to invest in additional resources or introduce work on overtime. If there is no proper method to compute resource requirements, a considerable waste in resource utilization would result. If resources are under utilized, even by a very small quantity, a considerably large delay of time would incur.     

Material Waste in Building Industry: Main Causes and Prevention

Material waste has been recognized as a major problem in the construction industry that has important implications both for the efficiency industry and for the environmental impact of construction projects. Moreover, waste measurement plays an important role in the management of production systems since it is an effective way to assess their performance, allowing areas of potential improvement to be pointed out. This paper describes the main results of two research studies carried out in Brazil that investigated the occurrence of material waste at 74 building sites located in different regions of that country. Some typical figures for the waste of some key construction materials are provided, and the main causes of waste in the sector are discussed. The results indicate that the waste of materials in the Brazilian building industry is fairly high and that a large variability in waste incidence is found across different projects. Most of this waste can be avoided by implementing inexpensive preventive measures, mostly related to managerial improvements.     

全国危险废物处置设施普查的分析和思考

对全国危险废物和医疗废物处置设施普查数据进行了全面分析,得出数量、布局、规模、工艺技术、运行等方面的总体情况,分别从加强清洁生产审核、开展危险废物产生源调查、完善危险废物鉴别体系、提高综合利用技术门槛、尽快淘汰落后医疗废物处理设施、严格控制《规划》项目建设规模、加大医疗废物非焚烧技术的宣传和应用、加快制定全过程管理的配套政策等方面,提出下一步加强管理和设施建设进程的工作建议。     

全国危险废物处置设施普查的分析和思考

对全国危险废物和医疗废物处置设施普查数据进行了全面分析，得出数量、布局、规模、工艺技术、运行等方面的总体情况，分别从加强清洁生产审核、开展危险废物产生源调查、完善危险废物鉴别体系、提高综合利用技术门槛、尽快淘汰落后医疗废物处理设施、严格控制《规划》项目建设规模、加大医疗废物非焚烧技术的宣传和应用、加快制定全过程管理的配套政策等方面，提出下一步加强管理和设施建设进程的工作建议。     

澳洲SINO选矿EPC工程仓储管理系统的开发及应用

结合澳洲SINO选矿EPC工程实例,介绍了国际EPC工程施工现场的仓储管理,尤其是发达法制国家无人区资源匮乏的施工现场的仓储管理系统软件开发及应用,通过计算机信息化管理,实现工程设备仓储管理的协同工作和实时动态管理,提高管理效率、降低管理成本,促进工程项目进度。     

项目管理的定义对实践的意义

本文阐述了项目和项目管理的定义,探索项目管理主要控制要素在建设工程项目中应用,论证了企业项目管理也将成为未来长期性组织管理的一种发展趋势,它将为企业的带来经营活力。     

Excavation Game: Computer-Aided-Learning Tool for Teaching Construction Engineering Decision Making

This paper reports on an interactive computer-aided-learning (CAL) tool that was developed for the education of construction engineering students: the excavation game. It builds on the large potential of using CAL in education. CAL tools could offer a better learning environment for students, as they provide an excellent opportunity for applying and testing the management skills learned in classroom, but are difficult to implement in reality. In this research, the CAL tool focuses on improving students’ decision-making skills in the aspects of excavation and related activities. These are excavation equipment, dewatering, and soil-support methods. It also covers mobilization, surveying, safety, overtime shifts, and reporting. Students compete with regard to time, cost, and quality of construction of a given project. The game flow is nonlinear as it depends on students’ decisions. Wrong decisions deviate the construction flow to a path that costs money and time, while reducing quality. This must be corrected costing extra money and time. The game was tested by senior practicing engineering and university professors. Then, it was tested by senior undergraduate construction students. Both groups agreed that the game responds, to a great extent, to the characteristics of effective CAL software, and that the information provided could not be easily assimilated or practiced through the usual tutorial or demonstration educational format. 18% of the professionals and 72% of students indicated the usefulness of the game in applying management and decision-making skills. 60–70% of students believed that it improved their technical skills in dewatering, soil-support, and excavation activities. In addition, 80% of the professionals found the game presenting realistic soil-support and excavation situations, while 72% of students became more appreciative of the interdependencies between activities.