Visualization of Work Flow to Support Lean Construction

Implementation of advanced production management techniques, such as lean construction concepts like filtering of work packages to stabilize work flows, pull flow of teams and materials, and in-process quality control, demands effective and timely flows of information both to and from the workface. The key requirement—making the process state transparent to all participants—is more difficult to achieve in construction than in manufacturing, because work crews move continuously within a physical environment that is itself changing. Novel computer-aided visualization tools can fulfill the needs that simpler tools, such as Kanban cards, fulfill in manufacturing. Two prototypes with user interfaces designed to facilitate process flow have been devised and implemented within the context of building information modeling (BIM) software systems. They demonstrate aspects of the synergy between BIM and lean construction. Given the dynamic and dispersed physical environments and the fractured contracting arrangements typical of construction, BIM-based visualization interfaces are important tools for providing process transparency.     

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.     

Irrigation Scheduling. II: Heuristics Approach

A sequential irrigation schedule that honors user demands of duration and minimizes earliness and tardiness is interpreted as a single-machine schedule with earliness and tardiness costs and a common deadline (or fixed interval). A heuristic solution is presented for this irrigation scheduling problem. Four models are presented to reflect the different methods in which an irrigation system at the tertiary unit level may be operated, the first model permits jobs to be noncontiguous, i.e., idle time between jobs is permitted, whereas the others permit contiguous jobs only. The heuristic is tested extensively and the solution quality is compared with either an optimum solution from an integer program or the best available solution obtained from an integer program within allocated computation time. The heuristic is computationally efficient for all models presented, however for schedules with noncontiguous jobs, or where idle time is inserted before and after a contiguous set of jobs, solution quality deteriorates. The work brings the science of single scheduling from operations research into irrigation scheduling and suggests areas for further development.     

Critical Concerns of Production Control System on Projects with Labor Constraints: Lessons from a Residential Case Study

Labor constraints and schedule pressures are common in periods of high market growth. Such conditions can have a significant impact on project performance. However, the extent to which such conditions impact the project depends on the effectiveness of the production control system. This case study analyzes the performance problems on a large residential project with significant labor constraints. The case first describes how the combination of labor shortage, high workload, and quality problems caused extensive workflow disruptions and schedule delays. Then, the analysis discusses why the production control system (the way the work assignments are planned, coordinated, and released for execution) failed to effectively manage these problems. The case is based on data from nine single-family houses in a large residential development. To evaluate the production control system, the authors used lean construction metrics and collected detailed data on the activities completed every week, the activities that were not completed as planned for that week, and the reasons for not completion. At the completion of the units, the researchers tracked the cycle time and evaluated the effect of the production control problems on the delays. The findings illustrate that, on projects with labor constraints, it is critical that the production control system focuses on creating reliable work assignments and minimizing quality defects in order to prevent further disruptions and make the best possible utilization of the limited labor resources.     

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.     

Critical Path Method with Multiple Calendars

This paper presents the critical path method forward and backward passes with multiple calendars. Multiple calendars are required in many construction projects to effectively represent various project conditions such as work properties, resource availabilities, weather conditions, etc. For this reason, major project management software packages such as P3 and MS-Project provide functions to handle multiple calendars. However, the background theory of handling multiple calendars has not been disclosed, so users of those software packages simply assume without clear knowledge that the time data generated by them are correct. This paper provides how multiple calendars should be handled in scheduling. Applying the theory presented herein, it has been noticed that the P3 operations with two calendars may generate a wrong answer for a start-to-finish with zero lag and inconsistent results in all negative lags when nonworking days are involved. The theory covers all four relationships in the precedence diagramming method with lags of zero, positive, and negative values. This study should be of considerable benefit to the construction industry and academics because it details and advances the theory for scheduling with multiple calendars, which is real scheduling in practice.     

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.     

Optimal Planning and Scheduling for Repetitive Construction Projects

This paper presents a multiobjective optimization model for the planning and scheduling of repetitive construction projects. The model enables construction planners to generate and evaluate optimal construction plans that minimize project duration and maximize crew work continuity, simultaneously. The computations in the present model are organized in three major modules: scheduling, optimization, and ranking modules. First, the scheduling module uses a resource-driven scheduling algorithm to develop practical schedules for repetitive construction projects. Second, the optimization module utilizes multiobjective genetic algorithms to search for and identify feasible construction plans that establish optimal tradeoffs between project duration and crew work continuity. Third, the ranking module uses multiattribute utility theory to rank the generated plans in order to facilitate the selection and execution of the best overall plan for the project being considered. An application example is analyzed to illustrate the use of the model demonstrate its new capabilities in optimizing the planning and scheduling of repetitive construction projects.     

MACROS: Multiobjective Automated Construction Resource Optimization System

This paper presents the development of a practical and automated system for optimizing the utilization of construction resources to simultaneously minimize project cost and duration while maximizing project quality. The system is named the Multiobjective Automated Construction Resource Optimization System (MACROS), and it incorporates four newly developed modules: (1) a multiobjective optimization module to quantify and optimize the impact of resource utilization decisions on construction duration, cost, and quality; (2) a relational database module to facilitate the storage and retrieval of construction scheduling and optimization data; (3) a middleware module to provide seamless integration between the internal modules in MACROS and external commercially available project management software; and (4) a user interface module to facilitate the input of project data and the visualization and ranking of the generated optimal construction plans. An example project of 180 activities is analyzed to illustrate the use of MACROS and demonstrate its unique and practical construction optimization capabilities.     

Ecological constraints on mental health services.

Proposes 4 principles for community mental health programing that are consistent with an ecological thesis: (1) Assessment methods are focused on the total population rather than on those persons who presently receive a mental health service. (2) Mental health services are designed to reduce a high risk for community service. (3) Professional and research services are created as local community resources. "By initiating the informal coordination of current services, the community mental health program helps to create specific new community services as needed." (4) The program plans for change; this involves mobilizing anticipatory problem-solving resources not only for clients but for professionals as well. A "conception of community mental health work based upon the ecological thesis that adaptive programs change" is presented. (39 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimating Work Zone Road User Cost for Alternative Contracting Methods in Highway Construction Projects

Highway construction often causes an additional road user cost (RUC) to motorists due to traffic flow interruption and congestion in work zones. Consequently, facility owners, such as the Florida Department of Transportation (FDOT), are often interested in using alternative contracting methods such as A+B contracting to expedite construction. Although many of these contracting methods rely on the RUC to determine incentives or disincentives, no standard method for RUC calculation is available to FDOT district engineers. In addition, existing methods are neither practical nor user-friendly for determining incentives or disincentives. This study intends to develop a RUC calculation procedure for the FDOT that focuses on using data that are easily accessible to FDOT district engineers, such as drawings and maintenance of traffic plans. The procedure is developed based on traffic analysis methods published in the Highway Capacity Manual, previous studies on user benefit analysis and work zones, and empirical data specific to Florida. Case studies are used to illustrate the procedure and to compare it with two other existing models, the Arizona model and the queue and user cost evaluation of work zone model, through correlation analysis, comparison of calculation assumptions, and data input analysis. This study shows that the suggested procedure produces consistent RUC estimates.     

Damage to Treasury: Abnormally Low Tenders in Public Construction Works

The purpose of this paper is to determine the adverse effect of abnormally low tenders (ALTs) on public construction works in Turkey. A comprehensive literature review was performed to investigate the reasons of ALTs. This paper categorizes the reasons behind ALTs with the help of a questionnaire to which 430 construction companies responded. A detailed analysis of the submitted questionnaires revealed a number of reasons for ALTs and their adverse effect on the construction industry. Staying in the business, miscalculation of bid price, work experience document, and inaccuracy of the conceptual cost were found to be the main reasons behind ALTs. A better database system for contractors on market unit prices, a better quality control assessment in construction and postconstruction phases, full complete design documents in tender packages, and a better evaluation system on the assessment of ALTs are recommended by the study.     

Evaluation of a Genetic Algorithm for the Irrigation Scheduling Problem

A typical irrigation scheduling problem is one of preparing a schedule to service a group of outlets which may be serviced simultaneously. This problem has an analogy with the classical earliness/tardiness problem in operations research. In previously published work an integer program was used to solve this problem, however such scheduling problems belong to a class of combinatorial problems known to be computationally demanding (N-P hard). This is widely reported in operations research. Hence integer programs can only be used to solve relatively small problems usually in a research environment where considerable computational resources and time can be allocated to solve a single schedule. For practical applications metaheuristics such as genetic algorithms, simulated annealing, or tabu search methods need to be used. However as reported in the literature, these need to be formulated carefully and tested thoroughly. This paper demonstrates the importance of robust testing of one such genetic algorithm formulated to solve the irrigation scheduling problem with simultaneous outlets serviced against an integer program formulated to solve the same problem.     

Population and Initial Validation of a Formal Model for Construction Safety Risk Management

The transient, unique, and complex nature of construction projects makes safety management exceptionally difficult. Most construction safety efforts are applied in an informal fashion under the premise that simply allocating more resources to safety management will improve site safety. Currently, there is no mechanism by which construction-site safety professionals may formally evaluate safety risk and select safety program elements for implementation. This paper introduces and validates a risk-based safety and health analytical model that can be used to evaluate expected risk given specific worker activities, strategically select highly effective safety program elements for implementation when resources are limited, and quantify resulting risk once the identified safety elements have been implemented. Specifically, the paper has three primary objectives: (1) introduce a risk-based construction safety and health analytical model; (2) validate relevant data used to populate the model; and (3) illustrate the applications of the model in practice. The findings of this research indicate that the values used to populate the model are reliable and that the model has the potential to significantly improve construction safety management.     

Human circular colonic smooth muscle cells possess active somatostatin receptors

High-dose chemotherapy with autologous and allogeneic blood stem cell transplantation has become a standard therapy for hematological malignancies and solid tumors. To ensure quality of treatment and adherence to internationally approved protocols, the use of computer systems has been introduced in some oncology centers. Most software packages cannot be used automatically by other institutions because of different treatment strategies and medications. To overcome this problem, we designed a software system based on an Oracle database, which allows the user to develop his own therapy blocks and assemble them to generate specific therapy plans. The system supports the daily work of the physicians by suggesting medications based on changes in the vital parameters or the clinical chemistry. Parameters can be given upper and lower limits whose surpassing leads to treatment suggestions by the system. All quantitative variables may be depicted in a graphical way. The system is connected to external laboratory devices. Export of data to international registries is possible. Until now, 43 patients have been transplanted with the help of this system. There is a high degree of acceptance among the nursing staff and the physicians. The system can be transferred to other centers, if the local hardware and network capacities meet the minimal requirements.     

Site Management of Work-in-Process Buffers to Enhance Project Performance Using the Reliable Commitment Model: Case Study

Buffers have been commonly used as a production strategy to protect construction processes from the negative impact of variability. Construction practitioners and researchers have proposed several buffering approaches for different production situations and contexts. However, these solutions have been impractical for managing buffers. To overcome this, this study proposes a new site methodology for managing work-in-process (WIP) buffer in repetitive projects, on the basis of the reliable commitment model (RCM). RCM is a decision-making tool based on lean principles, which uses statistical models to develop more reliable work plans at the operational level. RCM helps to manage WIP buffer in work plans by using site information and planning reliability indicators that result in improved project performance, such as labor productivity and process progress. A repetitive building project was used as a case study. The main finding was that labor productivity, process progress, and waiting times improved when using larger WIP buffers than those typically used among crews. This shows the potential of RCM as a practical tool to manage WIP buffer sizes and to promote the use of lean production strategies at the operational level.     

特殊钢厂炼钢-连铸调度模型

针对特殊钢厂的炼钢-连铸调度问题,建立了多目标调度模型.在模型求解过程中,对静态调度策略和动态调度策略进行了探讨.在静态调度部分,结合炼钢厂运行原则,并根据炼钢炉和连铸机作业周期的不同对应关系,对生产模式进行了分类,给出了相应的求解方法.在动态调度部分,给出了基于规则的动态调度策略以及具体的时间调整方法.最后,根据某转炉特殊钢厂的实际生产状况,在三台连铸机同时生产的情形下,对三个浇次的调度计划进行了仿真计算.通过与实际生产数据的比较,表明所采用方法的有效性.      

Optimal Schedule Planning for Multiple, Repetitive Construction Process

This study attempts to develop a construction scheduling model using a conceptual approach to improve the efficiency of construction resources for a multiple, repetitive construction process (MRCP). It is important for a project manager to arrange the number of horizontal repetitive work areas by each crew group to reduce the work interruption period in MRCP. This study suggests some equations for estimating the optimal number of horizontal repetitive work areas for a crew group and pursued a conceptual model for MRCP, which can reduce the loss in manpower and use of construction equipment that is caused by work interruption periods. A computer program developed for the analysis of MRCP shows an appropriate performance through the application to a case study based on the proposed procedure model in this study. Supposing that there is time to spare in the project completion date, the result of the study shows that cost loss could be greatly reduced by the proposed methodology.     

Microcomputer Spreadsheet Applications

The introduction of inexpensive microcomputer hardware and innovative user‐oriented software packages has had a significant impact on the traditional data processing procedures of the construction industry. Copyrighted electronic spreadsheet packages such as VisiCalc and SuperCalc are now available to practically all microcomputer users. These spreadsheet packages provide construction contractors, owners and managers with a versatile management tool that can be applied to a wide range of construction‐related problems. The overall capabilities of spreadsheet packages are examined and specific applications of interest to the construction management community are presented.